Heterocyclic triazin or triazolo compounds having serotonin 2-receptor antagonistic activity

Abstract: A heterocyclic compound represented by formula (I): and salts thereof, and intermediates therefor are disclosed. The compound of formula (I) and salts thereof exhibit selective serotonin 2-receptor antagonistic activity and are useful for the prevention or treatment of circulatory diseases, e.g., ischemic heart diseases, cerebral vessel disturbances, and peripheral circulation disturbances.

Description: This invention relates to heterocyclic compounds represented by formula (I) shown below, and the salts thereof. Also, this invention relates to a pharmaceutical composition, in particular as a serotonin 2-receptor antagonist and for preventing or treating heart diseases, which contains a compound of formula (I) or a salt thereof as an active ingredient. The heterocyclic compound of formula (I) and salts thereof exhibit selective serotonin 2-receptor antagonistic activity and are useful for the prevention and treatment of circulatory diseases, e.g., ischemic heart diseases such as angina pectoris, myocardial infarction, heart failure, restenosis after percutaneous transluminal coronary angioplasty, cerebral vessel disturbances such as cerebral infarction, brain injury after subarachnoidal hemorrhage, and peripheral circulation disturbances such as Raynaud disease, Buerger disease. Known treating agents for heart diseases, e.g., angina pectoris, myocardial infarction, and heart failure, include β-blockers, calcium blockers, and cardiotonics. Drugs having serotonin 2-receptor antagonistic activity have recently been studied as treating agents for the heart diseases, but there has been found no drug having sufficient effects. Serotonin has strong physiological activities, such as blood platelet aggregation and vasoconstriction, and is a neurotransmitter. Serotonin is known to act serotonin receptors, and the serotonin receptors are known to include serotonin 1-receptor, serotonin 2-receptor, etc. In case of cardiac infarction endothelial cells of coronary vessels are injured and in such case it is considered that serotonin causes vasoconstriction or thrombus formation through serotonin 2-receptor, resulting in further reduction of blood supply to the ischemic site of the myocardium. From this point of view, drugs for treating ischemic heart diseases have also been studied. As a representative serotonin 2-receptor antagonist which has been clinically used, Ketanserin is known. Also, Ritanserin and Irindalone are known as serotonin 2-receptor antagonists but they are not yet practically used in therapy. Ketanserin is a serotonin 2-receptor antagonist and also strong α₁-receptor antagonist, and hypotensive activity thereof is believed to be attributed to the α₁-receptor antagonistic activity. On the other hand, strong hypotensive activity is unfavorable for some ischemic heart diseases, such as acute myocardial infarction. From this viewpoint, Ketanserin having strong α₁-receptor antagonistic activity is not useful for the treatment of ischemic heart diseases. From the same reason, Irindalone having strong hypotensive activity due to α₁-receptor antagonistic activity is also unfavorable. While Ritanserin shows weak α₁-receptor antagonistic activity, it is known to have a neuroleptic activity and is therefore an unsuitable drug for circulatory diseases. Thus, most conventional serotonin 2-receptor antagonists have many pharmacological activities such as α₁-receptor antagonistic activity and neuroleptic activity other than the objective activity. EP-A-62 873 relates to compounds of the formula wherein Ar is a phenyl group or a phenyl group substituted by one or more members of the group consisting of halogen atoms or lower alkyl, halolower alkyl, hydroxy or lower alkoxy groups, "lower" indicating groups having from 1 to 5 carbon atoms; m is zero or 1, n is 2 or 3; and their dehydro derivatives having a double bond in the azacyclic ring extending from the carbon atom having the Ar substituent; and the pharmaceutically acceptable acid addition salts thereof. These compounds have analgesic activity. US-A-3,609,148 relates to herbicidal compounds of the formula wherein R₁ represents hydrogen, halogen, nitro, lower alkyl, lower alkoxy or halogenalkyl, R₂ represents straight- or branched-chain alkyl, lower alkenyl, lower alkynyl, cycloalkyl, alkoxyalkyl or halogenalkyl, and R₃ represents hydrogen, halogen, nitro, lower alkyl, lower alkoxy or halogenalkyl. An object of this invention is to provide a compound having highly selective serotonin 2-receptor antagonistic activity over other activities, particularly α₁-receptor antagonistic activity , and being useful as a preventing or treating agent for heart diseases, etc. It was now found that the above object is accomplished by the heterocyclic compounds represented by formula (I) shown below. This invention relates to heterocyclic compounds represented by formula (I): wherein R¹ represents a hydrogen atom, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, an alkox group, an alkyl group and a trihalogenomethyl group; ℓ represents 0 or 1; ring A represents a 5- to 7-membered heterocyclic ring which may contain one hetero atom selected from the group consisting of an oxygen atom and a sulfur atom in addition to the nitrogen atom shared with the triazine ring or triazole ring, and which may contain one or more double bonds; Y represents an alkylene group having from 1 to 15 carbon atoms which may be substituted with one or more substituents selected from a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; and Q represents a group represented by formula (II): wherein R² represents a hydrogen atom, a hydroxyl group, an alkyl group or an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, a hydroxyl group, an alkyl group, an alkoxy group and a trihalogenomethyl group; and R³, R⁴ and R⁵, which may be the same or different, each represents a hydrogen atom, a halogen atom an alkyl group, an alkoxy group, a nitrogen containing 5- to 7-membered alicyclic heterocyclic group which in addition may contain one or more hetero atoms selected from a nitrogen atom, an oxygen atom and a sulfur atom or a trihalogeno group, or a group represented by formula (III): wherein Ar¹ and Ar², which may be the same or different, each represents an aryl group or an aromatic heterocyclic group, selected from pyridyl, pyrimidinyl, thienyl, furyl, pyrazolyl, imidazolyl, thiazoly, oxazolyl, isothiazolyl and isoxazolyl, each of which may be substituted with one to three substituents selected from the group consisting of a halogen atom, a hydroxyl group, an alkoxy group, an alkyl group and a trihalogenomethyl group, whereby in the above meanings the alkyl and alkoxy groups contain 1 to 6 carbon atoms and aryl is phenyl, naphthyl or biphenyl, and salts thereof. The present invention furthermore relates to a pharmaceutical composition, in particular as a serotonine-2 receptor antagonist or for preventing or treating heart diseases, which contains at least one compound of formula (I) or a salt thereof as an active ingredient. The heart diseases on which the compounds of the present invention are effective include angina pectoris, myocardial infarction, heart failure, restenosis after percutaneous transluminal coronary angioplasty and arrhythmia. In formula (I), the alkyl group contains from 1 to 6 carbon atoms and includes methyl, ethyl, isopropyl, n-propyl, t-butyl, n-butyl groups and the like. The halogen atoms includes fluorine, chlorine, bromine and iodine atoms. The trihalogenomethyl group is a methyl group substituted with three halogen atoms (e.g., fluorine, chlorine, bromine, and iodine) and includes trichloromethyl, trifluoromethyl groups and the like. The alkoxy group contains from 1 to 6 carbon atoms and includes methoxy, ethoxy, propoxy, butoxy groups and the like. Ring A fuses with the triazine or triazole ring with sharing a nitrogen atom and a carbon atom together, and includes 5- to 7-membered aromatic or aliphatic heterocyclic rings, which may contain, in addition to the nitrogen atom shared with the triazine or triazole ring, one more hetero atom selected from an oxygen or sulfur atom and may contain one or more, preferably two, double bond, e.g., pyridine, 1,2-dihydropyridine, 1,2,3,4-tetrahydropyridine, 1,2,3,6-tetrahydropyridine, pyrrole, pyrroline, piperidine, homopiperidine, pyrrolidine, azepine, 1,2-dihydroazepine, 1,2,3,4-tetrahydroazepine, 1,2,3,6-tetrahydroazepine, thiazole, thiazoline, thiazolidine, oxazole, oxazoline, oxazolidine, isothiazole, isothiazoline, isothiazolidine, isoxazole, isoxazoline, isoxazolidine, 1,4-oxazine, 2,3-dihydro-1,4-oxazine, morpholine, 1,3-oxazine, 2,3-dihydro-1,3-oxazine, 2,3,4,5-tetrahydro-1,3-oxazine, 1,4-thiazine, 1,3-thiazine, and the like. The aryl group includes phenyl, naphthyl and biphenyl groups and the like, and usually the aryl group may be substituted with one or more, preferably to three, substituents. The aromatic heterocyclic group in formula (III) includes pyridyl, pyrimidinyl, thienyl, furyl, pyrazolyl, imidazolyl, thiazolyl, oxazolyl, isothiazolyl, isoxazolyl groups and the like. The alkylene group includes a methylene or polymethylene group which may be substituted with one or more alkyl groups. Specific examples of the alkylene group include methylene, ethylene, propylene, butylene, pentylene, ethylethylene, trimethylene, tetramethylene, hexylene, and heptylene groups. Preferably, Y is an alkylene group having 2 to 7 carbon atoms or a group of the following formula: wherein R⁶ represents a hydrogen atom, an alkyl group, an aryl group which may be substituted with one or more substituents selected from a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group . and n and m each represents 0 or an integer of from 1 to 6. The alicyclic heterocyclic group for R₃, R₄ and R₅ includes 5- to 7-membered heterocyclic group derived from the alicyclic heterocyclic ring referred for ring A. Salts of the compound of formula (I), particularly, pharmaceutically acceptable salts thereof include acid addition salts formed with inorganic acids, e.g., hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, organic acids, e.g., methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, tartaric acid, maleic acid, fumaric acid, malic acid, oxalic acid, lactic acid, citric acid and the like. This invention includes a heterocyclic compound and salts thereof as claimed in Claim 1, wherein Q is represented by formula: wherein R⁷ and R⁸, which may be the same or different, each represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxy group, a halogen atom or a trihalogenomethyl group and a heterocyclic compound and salts thereof as claimed in Claim 1, wherein Q is represented by formula: wherein R² represents a hydrogen atom, a hydroxyl group, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of an alkyl group, an alkoxy group, a halogen atom, and a trihalogenomethyl group; and R³, R⁴ and R⁵, which may be the same or different, each represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or an alicyclic heterocyclic group. The compound of formula (I) preferably includes those represented by formulae (IV), (V) and (VI): wherein ring A, R¹, R⁶, Q, m, and n are as defined above. wherein ring A and R¹ are as defined above; R⁷ and R⁸, which may be the same or different, each represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxy group, a halogen atom or a trihalogenomethyl group; Y¹ represents an alkylene group having from 2 to 7 carbon atoms. wherein ring A, R¹, R², R³, R⁴, R⁵ and Y¹ are as defined above. Of the compounds represented by formula (I), particularly preferred are those wherein ring A is a pyrrolidine or a piperidine, a homopiperidine or a thiazole; Y is an alkylene group having 1 to 6 carbon atoms; and Q is a group represented by formula (II') or (III'): wherein R²¹ represents a hydrogen atom or a hydroxyl group; and X represents a halogen atom. wherein X¹ and X², which may be the same or different, each represents a halogen atom. In the above (V) and (VI), the alkylene group as represented by Y¹ is a methylene or polymethylene group which may be substituted with one or more alkyl groups, and examples thereof includes methylene, ethylene, propylene, butylene, pentylene, hexylene, ethylethylene, trimethylene, tetramethylene groups and the like. Of the compounds of formula (I), most preferred is 3-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione or acid addition salts thereof. The heterocyclic compounds represented by formula (I) can be prepared by many processes. Typical processes thereof are as follows. 1) Process A: The heterocyclic compounds of formula (I) can be prepared by reacting a compound represented by formula (VII): wherein R¹, ring A and ℓ are as defined above, with a compound of formula (VIII): HO - Y - Q (VIII) wherein Q and Y are as defined above, in a solvent, e.g., dimethylformamide, tetrahydrofuran and dioxane, in the presence of dehydrating reagents, for example, a mixture of triphenylphosphine and a dialkyl azodicarboxylate, at a temperature of from 0°C to the boiling point of the solvent for several minutes to several days. The compounds of formula (VIII) and dehydrating reagents can be used in equimolar excess amount to the compound of formula (VII). The compounds of formula (I) can also be prepared by reacting the compound of formula (VII) or salts thereof with a compound represented by formula (IX): X³ - Y - Q (IX) wherein Y and Q are as defined above; and X³ represents a halogen atom, a trifluoromethanesulfonyloxy group, an alkylsulfonyloxy group or an arylsulfonyloxy group which may be substituted with an alkyl group, a halogen atom or an alkoxy group in the aryl group moiety thereof, in the presence of a base, e.g., an alkali metal carbonate (e.g., potassium carbonate and sodium carbonate), an alkali metal hydride (e.g., sodium hydride and potassium hydride), and an organic base (e.g., triethylamine and 1,8-diazacyclo[5.4.0]-7-undecene), in an organic solvent, e.g., ethanol, methanol, dimethylformamide, tetrahydrofuran, dioxane, and benzene, at a temperature of from room temperature to the boiling point of the solvent for 0.5 hours to several days. The reaction may be carried out in the presence of from a catalytic amount to an equimolar excess amount of an alkali metal iodide, e.g., sodium iodide and potassium iodide to the compound of formula (VII). The compound of formula (IX) and base can be used in equimolar excess amount to the compound of formula (VII). The above arylsulfonyloxy group include p-toluenesulfonyloxy group and p-bromophenylsulfonyloxy group, preferably p-toluenesulfonyloxy group. Some of the intermediate compounds represented by formula (VII), wherein ℓ is 1, are known. For example, 2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione, 6-methyl-2H-oxazolo[3,2-a]-1,3,5-triazine-2,4(3H)-dione, and 8-methylimidazo[1,2-a]-1,3,5-triazine-2,4(3H,8H)-dione are disclosed in West German OLS 1922837, Synthesis , p. 892 (1985), British Patent 1328205, and Journal of Organic Chemistry , Vol. 43, p. 4774 (1978), respectively. The compounds of formula (VII) can be prepared by referring to the processes disclosed in the above-described literatures. In general, the compounds of formula (VII) wherein ℓ is 1 can be prepared by reacting a compound represented by formula (X): wherein R¹ and ring A are as defined above, with phenoxycarbonylisocyanate or diphenyl imidocarboxylate in a solvent, e.g., dimethylformamide, tetrahydrofuran, acetonitrile and dioxane, at a temperature of from 0°C to the boiling point of the solvent. Also, most of the compounds of formula (VII) wherein ℓ is 0 are known and can be prepared according to processes described in Boll. Chim. Farm. , Vol. 113, p. 152 (1974), Chem. Ber ., Vol. 90, p. 909 (1957) and Gem. Ber ., Vol. 103, p. 1934 (1970), 2) Process B: The compound of formula (I) can be prepared by reacting a compound represented by formula (XI): wherein R¹, ring A, ℓ and Y are as defined above; and X⁴ represents a halogen atom, a trifluoromethanesulfonyloxy group, an alkylsulfonyloxy group or an arylsulfonyloxy group which may be substituted with an alkyl group, an alkoxy group or a halogen atom in the aryl group moiety thereof with a compound represented by formula (XII) or salts thereof: H-Q (XII) wherein Q is as defined above, in a solvent, e.g., benzene, toluene, acetonitrile, chloroform, dichloroethane, dimethylformamide, tetrahydrofuran and dioxane, in the presence of a base, e.g., triethylamine, dimethylaniline, 1,8-diazabicyclo[5.4.0]-7-undecene, potassium carbonate, sodium carbonate, sodium hydride, and potassium hydride, at a temperature of from room temperature to the boiling point of the solvent for 0.5 hours to several days. If desired, this reaction may be carried out in the presence a catalytic amount to equimolar excess amount of an alkali metal iodide, e.g., sodium iodide and potassium iodide to the compound of formula (XI). The compound of formula (XII) and base can be used in equimolar excess amount to the compound of formula (XI). Of the starting compounds of formula (XI), the compounds wherein ℓ is 0 are novel compounds and can be prepared by processes described in the Reference Examples hereinafter given or an appropriate combination of known processes, such as those described in Boll. Chim. Farm. , Vol. 113, p. 152 (1974), Chem. Ber . , Vol. 90, p. 909 (1957), and Chem. Ber . , Vol. 103, p. 1934 (1970). Also, of the compounds of formula (XI), the compounds wherein ℓ is 1 can be prepared by processes described in the Reference Examples or processes as follows. wherein ring A, R¹, Y and X⁴ are as defined above, and Ar³ represents an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, an alkyl group, an alkoxy group and a nitro group. That is, the compound of formula (VIIa) can be reacted with a compound of HO-Y-X⁴ in the presence of triphenylphosphine and diethylazodicarboxylate in an organic solvent at a temperature of -30°C to the boiling point of the used solvent to give the objective compound of formula (XIa). Also, the compound of formula (X) can be reacted with the compound of formula (XIII) in an organic solvent at a temperature of room temperature to the boiling point of the used solvent to give a compound of formula (XIV), and the compound can be reacted with alkylsulfonylchloride, arylsulfonylchloride which may be substituted with an alkyl group, an alkoxy group or a halogen atom or halogenating agents such as thionylchloride, phosphorouschloride in the presence of an organic base such as triethylamine, dimethylaniline, 1,8-diazabicyclo[5.4.0]-7-undecene in an organic solvent to give the objective compound of formula (XIa). When the compound of formula (I) according to the present invention was orally administered to rats for 10 consecutive days, no case of death was observed at a dose level of 800 mg/kg, proving that the compound of formula (I) and salts thereof are of high safety. The compounds of formula (I) or a salt thereof can be formulated into various dose forms, such as tablets, powders, capsules, and injectable solutions by conventional techniques using appropriate additives such as lactose, corn starch, crystalline cellulose, polyvinyl alcohol, carboxymethyl cellulose calcium, magnesium stearate, talc and the like. The compounds of formula (I) and salts thereof can be generally administered orally, subcutaneously, intramuscularly or intravenously. The compounds of formula (I) or a salt thereof are usually administered at a dose of from 30 to 2,000 mg/day for adult when orally given. The compounds according to the present invention and the salts thereof exhibit potent and long-lasting serotonin 2-receptor antagonistic activity, while having weak α₁-receptor antagonistic activity. Therefore, they have excellent selectivity in their serotonin 2-receptor antagonistic activity the selectivity being higher than that of Ketanserin, and the activity being higher than that of Ritanserin. Further, the compounds of the invention and the salts thereof have lower toxicity than Ketanserin and weak neuroleptic activity. Accordingly, the compounds of formula (I) and salts thereof are very excellent as a serotonin 2-receptor antagonist or a drug for circulatory diseases. In particular, the compounds of formula (I) and salts thereof experimentally exhibited excellent activities in improvement of cardiac functions, improvement on myocardium necrosis, prevention of coronary thrombus formation, improvement of cardiac microcirculation, and the like in heart disease animal models, such as an angina pectoris model, a myocardial infarction model, etc. Thus, the compounds of formula (I) and salts thereof are excellent as a preventing and treating agent for heart diseases, particularly ischemic heart diseases. The present invention is now illustrated in greater detail by way of Reference Examples, Examples, and Test Examples. EXAMPLE 1 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione 1)6,7,8,9-Tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione: To an ethanol solution of sodium ethoxide prepared from 0.83 g of metallic sodium and 40 mℓ of absolute ethanol was added 4.8 g of 2-amino-3,4,5,6-tetrahydropyridine hydrochloride under ice-cooling, followed by stirring at room temperature for 30 minutes. The insoluble material was removed by filtration, and the filtrate was concentrated to dryness under reduced pressure. The residue was suspended in 30 mℓ of tetrahydrofuran, and 5.9 g of phenoxycarbonylisocyanate was added dropwise to the suspension with stirring under ice-cooling over 10 minutes. After allowing to stand at room temperature overnight, the precipitated material was filtered to give 1.4 g of the entitled compound. The filtrate was concentrated to dryness under reduced pressure, and the residue was applied to a column contained with 100 g of silica gel, then eluted with chloroform containing 5% methanol to obtain 2.04 g of the entitled compound. The two crops were combined to yield 3.44 g of the entitled compound as colorless crystals. Melting Point: 185-187°C NMR Spectrum (DMSO-d₆) δ: 1.6-1.9 (4H, m), 2.65 (2H, t), 3.64 (2H, t), 11.39 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3450, 3200, 3070, 1700, 1590, 1490, 1440, 1390 Elemental Analysis for C₇H₉N₃O₂: Calcd. (%) C 50.30; H 5.43; N 25.14 Found (%) C 50.37; H 5.45; N 24.91 2) 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione: In 900 mℓ of tetrahydrofuran were suspended 34.1 g of 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in 1) above, 51.2 g of 4-(4-fluorobenzoyl)-1-(2-hydroxyethyl)piperidine and 56.1 g of triphenylphosphine, and 38 g of diethyl azodicarboxylate was added dropwise thereto under ice-cooling over 15 minutes. After stirring at room temperature for 20 minutes, the reaction mixture was concentrated to dryness under reduced pressure, and to the residue was added 500 mℓ of ethyl acetate. The reaction mixture was extracted with 1N hydrochloric acid, and the extract was made alkaline with potassium carbonate and then extracted with chloroform. The chloroform solution was dried over anhydrous sodium sulfate, and then concentrated to dryness under reduced pressure. The residue was crystallized from ethanol and then recrystallized from a mixed solvent of methanol and ethanol to obtain 33.7 g of the entitled compound as colorless crystals. Melting Point: 170-172°C NMR Spectrum (CDCℓ₃) δ: 1.8-2.2 (10H, m), 2.26 (2H, t), 2.81 (2H, t), 3.0-3.3 (3H, m), 3.84 (2H, t), 4.06 (2H, t), 7.13 (2H, t), 7.95 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 1730, 1670, 1600, 1490, 1450, 1410 Elemental Analysis for C₂₁H₂₅FN₄O₃: Calcd. (%) C 62.99; H 6.29; N 13.99 Found (%) C 62.68; H 6.28; N 13.83 EXAMPLE 2 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione Hydrochloride In 150 mℓ of hot ethanol was dissolved 33.0 g of 3-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione as prepared in Example 1, and 15 mℓ of concentrated hydrochloric acid was added to the solution. After cooling, the precipitated crystals were collected by filtration and recrystallized from ethanol to obtain 27.4 g of the entitled compound as colorless crystals. Melting Point: 256-259°C (decomposition) NMR Spectrum (D₂O) δ: 1.4-2.4 (8H, m), 2.86 (2H, t), 3.1-4.0 (9H, m), 4.37 (2, t), 7.30 (2H, t), 8.07 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 3450, 2940, 2510, 1730, 1670, 1600, 1480, 1420 Elemental Analysis for C₂₁H₂₅FN₄O₃·HCℓ: Calcd. (%) C 57.73; H 6.00; N 12.82 Found (%) C 57.50; H 5.82; N 12.59 EXAMPLE 3 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione Maleate In 50 mℓ of methanol was dissolved 2.0 g of 3-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in Example 1, and 0.58 g of maleic acid was added to the solution. The solution was concentrated under reduced pressure, and the precipitated crystals were collected by filtration, followed by recrystallization from 90% aqueous ethanol to give 1.27 g of the entitled compound as colorless crystals. Melting Point: 180-183°C (decomposition) NMR Spectrum (DMSO-d₆) δ: 1.6-2.1 (8H, m), 2.71 (2H, t), 2.9-3.4 (4H, m), 3.5-3.8 (5H, m), 4.12 (2H, m), 6.06 (2H, s), 7.39 (2H, t), 8.10 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 3448, 1734, 1677, 1596, 1494, 1455 Elemental Analysis for C₂₁H₂₅FN₄O₃·C₄H₄O₄: Calcd. (%) C 58.13; H 5.66; N 10.85 Found (%) C 58.28; H 5.64; N 10.87 EXAMPLE 4 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione 1) 7,8-Dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione: In the manner described in Example 1-1), the entitled compound was obtained as colorless crystals from 2-iminopyrrolidine hydrochloride and phenoxycarbonylisocyanate. Melting Point: 201-202°C NMR Spectrum (DMSO-d₆): 2.87 (2H, t), 2.07 (2H, t), 3.82 (2H, t), 11.25 (1H, bs) IR Spectrum ν (KBr) cm⁻¹: 3430, 3210, 3080, 1740, 1710, 1690, 1630, 1440, 1410 Elemental Analysis for C₆H₇N₃O₂: Calcd. (%) C 47.06; H 4.61; N 27.44 Found (%) C 47.15; H 4.40; N 27.33 2)3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione: In the manner described in Example 1-2), 7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in 1) above and 4-(4-fluorobenzoyl)-1-(2-hydroxyethyl)piperidine were condensed in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as a caramel-like substance. NMR Spectrum (CDCl₃) δ: 1.7-1.9 (4H, m), 2.1-2.5 (4H, m), 2.68 (2H, t), 2.9-3.4 (5H, m), 4.05 (4H, t-like), 7.12 (2H, t), 7.95 (2H, dd) EXAMPLE 5 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione Hydrochloride Hemihydrate In 50 mℓ of methanol was dissolved 2.95 g of 3-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in Example 4-2), and 2 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. The residue was crystallized from ethanol to obtain 2.30 g of the entitled compound as a colorless powder. Melting Point: 253-255°C NMR Spectrum (DMSO-d₆) δ: 1.8-2.3 (6H, m), 2.91 (2H, t), 3.0-3.5 (4H, m), 3.5-4.0 (5H, m), 4.16 (2H, t), 7.37 (2H, t), 8.09 (2H, dd), 10.68 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3560, 2940, 2510, 1730, 1680, 1630, 1480, 1450, 1420 Elemental Analysis for C₂₀H₂₃FN₄O₃·HCℓ·1/2H₂O: Calcd. (%) C 55.62; H 5.83; N 12.97 Found (%) C 55.69; H 5.80; N 12.83 EXAMPLE 6 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-7,8,9,10-tetrahydro-2H,6H-1,3,5-triazino[1,2-a]azepine-2,4(3H)-dione 1) 7,8,9,10-Tetrahydro-2H,6H-1,3,5-triazino[1,2-a]azepine-2,4(3H)-dione Monohydrate: In the manner described in Example 1-1), the entitled compound was prepared as a colorless powder from 3,4,5,6-tetrahydro-7-amino-2H-azepine hydrochloride and phenoxycarbonylisocyanate. Melting Point: 157-158°C NMR Spectrum (CDCℓ₃) δ: 1.7 (6H, m), 2.8 (2H, m), 4.0 (2H, m), 11.0 (1H, bs) IR Spectrum ν (KBr) cm⁻¹: 3520, 3200-2800, 1730, 1670, 1600, 1480, 1420 Elemental Analysis for C₈H₁₁FN₃O₂·H₂O: Calcd. (%) C 48.24; H 6.58; N 21.09 Found (%) C 48.33; H 6.42; N 21.02 2) 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-7,8,9,10-tetrahydro-2H,6H-1,3,5-triazino[1,2-a]azepine-2,4(3H)-dione: In the manner described in Example 1-2), 7,8,9,10-tetrahydro-2H,6H-1,3,5-triazino[1,2-a]azepine-2,4(3H)-dione prepared in 1) above was condensed with 4-(4-fluorobenzoyl)-1-(2-hydroxyethyl)piperidine in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as colorless crystals. Melting Point: 130-132°C NMR Spectrum (CDCℓ₃) δ: 1.6-2.0 (10H, m), 2.0-2.4 (2H, m), 2.69 (2H, t), 3.0-3.3 (3H, m), 4.0-4.2 (4H, m), 7.13 (2H, t), 7.95 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 3440, 2950, 1725, 1670, 1600, 1470, 1440 EXAMPLE 7 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-7,8,9,10-tetrahydro-2H,6H-1,3,5-triazino[1,2-a]azepine-2,4(3H)-dione Dihydrochloride In 50 mℓ of methanol was dissolved 3.63 g of 3-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-7,8,9,10-tetrahydro-2H,6H-1,3,5-triazino[1,2-a]azepine-2,4(3H)-dione prepared in Example 6, and 1.6 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. Ethanol was added to the residue, the mixture was concentrated under reduced pressure several times, and the residue was crystallized from a mixture of ethanol and isopropyl ether to obtain 3.70 g of the entitled compound as a colorless powder. Melting Point: 172-176°C NMR Spectrum (DMSO-d₆) δ: 1.6-2.2 (10H, m), 2.8 (2H, m), 3.0-3.5 (4H, m), 3.5-3.9 (3H, m), 4.0-4.2 (4H, m), 7.37 (2H, t), 8.12 (2H, dd), 11.0 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3450, 2940, 2360, 1770, 1725, 1680, 1610, 1580, 1450, 1430, 1230 Elemental Analysis for C₂₂H₂₇FN₄O₃·2HCℓ: Calcd. (%) C 54.21; H 6.00; N 11.50 Found (%) C 54.12; H 6.33; N 11.42 EXAMPLE 8 Synthesis of 3-[3-[4-(4-Fluorobenzoyl)piperidin-1-yl)propyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione In the manner described in Example 1-2), 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in Example 1-1) and 4-(4-fluorobenzoyl)-1-(3-hydroxypropyl)piperidine were condensed in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃) δ: 1.5-2.1 (12H, m), 2.50 (2H, t), 2.7-3.1 (4H, m), 3.2 (1H, m), 3.85 (2H, t), 4.02 (2H, t), 7.13 (2H, t), 7.95 (2H, dd) EXAMPLE 9 Synthesis of 3-[3-[4-(4-Fluorobenzoyl)piperidin-1-yl]propyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione Maleate Hemihydrate In 100 mℓ of hot ethanol was added 0.76 g of 3-[3-[4-(4-fluorobenzoyl)piperidin-1-yl]propyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in Example 8, and 0.21 g of maleic acid was added thereto. The precipitated crystals were collected by filtration and recrystallized from ethanol to obtain 0.42 g of the entitled compound as colorless crystals. Melting Point: 87-89°C NMR Spectrum (DMSO-d₆) δ: 1.6-2.2 (10H, m), 2.70 (2H, t), 2.9-3.3 (4H, m), 3.4-4.0 (7H, m), 6.04 (2H, s), 7.39 (2H, t), 8.10 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 3450, 2970, 1730, 1680, 1600, 1490 Elemental Analysis for C₂₂H₂₇FN₄O₃·C₄H₄O₄·1/2H₂O: Calcd. (%) C 57.88; H 5.98; N 10.38 Found (%) C 57.50; H 6.30; N 10.18 EXAMPLE 10 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione In the manner described in Example 1-2), 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 1-1) and 4-(4-fluorobenzoyl)-4-hydroxy-1-(2-hydroxyethyl)piperidine were condensed in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as colorless crystals. Melting Point: 217-220°C NMR Spectrum (CDCℓ₃) δ: 1.6-2.0 (8H, m), 2.3-2.7 (8H, m), 3.68 (2H, t), 3.87 (2H, t), 5.68 (1H, s), 7.28 (2H, t), 8.24 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 3450, 2960, 1730, 1670, 1600, 1490, 1450, 1410 EXAMPLE 11 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione Dihydrochloride Hemihydrate In 30 mℓ of methanol was dissolved 0.80 g of 3-[2-[4-(4-fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 10, and 0.4 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. Ethanol was added to the residue, followed by concentration under reduced pressure repeatedly. The precipitated crystals were collected by filtration and washed with acetone to obtain 0.68 g of the entitled compound as colorless crystals. Melting Point: 178-184°C NMR Spectrum (DMSO-d₆) δ: 1.6-2.4 (8H, m), 2.7 (2H, t), 3.0-3.6 (6H, m), 3.73 (2H, t), 4.1 (2H, t), 7.2-7.5 (3H, m), 8.77 (2H, dd), 11.0 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3410, 3220, 2550, 1780, 1730, 1680, 1610, 1580, 1440 Elemental Analysis for C₂₁H₂₅FN₄O₄·2HCℓ·1/2H₂O: Calcd. (%) C 50.60; H 5.66; N 11.24 Found (%) C 50.88; H 5.81; N 10.87 EXAMPLE 12 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)-4-phenylpiperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione In the manner described in Example 1-2), 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 1-1) and 4-(4-fluorobenzoyl)-4-phenyl-1-(2-hydroxyethyl)piperidine were condensed in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃) δ: 1.8-2.9 (16H, m), 3.8 (2H, t-like), 4.03 (2H, t), 6.89 (2H, t), 7.26-7.48 (7H, m) EXAMPLE 13 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)-4-phenylpiperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione Dihydrochloride Hemihydrate In 30 mℓ of methanol was dissolved 0.75 g of 3-[2-[4-(4-fluorobenzoyl)-4-phenylpiperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 12, and 0.3 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. To the residue was added ethanol, followed by concentration to dryness under reduced pressure repeatedly. The residue was recrystallized from a mixture of methanol and ethanol to obtain 0.52 g of the entitled compound as a colorless powder. Melting Point: 203-210°C NMR Spectrum (DMSO-d₆) δ: 1.6-2.0 (4H, m), 2.4-3.1 (8H, m), 3.3 (2H, m), 3.5-3.7 (4H, m), 4.1 (2H, t), 7.1-7.7 (9H, m), 11.2 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3410, 2960, 2490, 1770, 1730, 1680, 1620, 1580, 1500, 1440 Elemental Analysis for C₂₇H₂₉FN₄O₃·2HCℓ·1/2H₂O: Calcd. (%) C 58.07; H 5.77; N 10.03 Found (%) C 58.28; H 6.04; N 9.70 EXAMPLE 14 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione Dihydrochloride In 10 mℓ of N,N-dimethylformamide were suspended 0.42 g of 2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione,0.67 g of 4-(4-fluorobenzoyl)-1-(2-hydroxyethyl)piperidine and 0.82 g of triphenylphosphine, and 0.54 g of diethyl azodicarboxylate was added dropwise thereto, followed by stirring at room temperature for 75 minutes. The reaction mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from ethanol and filtered to collect 0.7 g of the base of the entitled compound. The resulting crystals were dissolved in 30 mℓ of ethanol, and 0.2 mℓ of hydrochloric acid was added, followed by concentration under reduced pressure. The precipitate was collected by filtration to obtain 0.27 g of the entitled compound as a colorless powder. Melting Point: 243-244°C (decomposition) NMR Spectrum (DMSO-d₆) δ: 1.8-2.2 (4H, m), 2.88-3.97 (7H, m), 4.38 (2H, t), 7.1-7.5 (4H, m), 8.0-8.3 (3H, m), 8.69 (1H, d), 11.02 (1H, bs) IR Spectrum ν (KBr) cm⁻¹: 3430, 2700-2200, 1730, 1680, 1640, 1590, 1560, 1440, 1410 Elemental Analysis for C₂₁H₂₁FN₄O·2HCℓ: Calcd. (%) C 53.74; H 4.94; N 11.94 Found (%) C 53.39; H 4.83; N 11.83 EXAMPLE 15 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-2H-thiazolo[3,2-a]-1,3,5-triazine-2,4(3H)-dione In 40 mℓ of N,N-dimethylformamide were suspended 1.69 g of 2H-thiazolo[3,2-a]-1,3,5-triazine-2,4(3H)-dione, 2.51 g of 4-(4-fluorobenzoyl)-1-(2-hydroxyethyl)piperidine and 2.89 g of triphenylphosphine, and 1.92 g of diethyl azodicarboxylate was added dropwise thereto with stirring under ice-cooling. After stirring at room temperature for 30 minutes, the reaction mixture was concentrated to dryness under reduced pressure. Ethyl acetate was added to the residue, followed by filtration to obtain 3.0 g of the entitled compound as colorless crystals. Melting Point: 184-187°C NMR Spectrum (CDCℓ₃) δ: 1.5-1.9 (4H, m), 2.2 (2H, m), 2.5 (2H, m), 3.0 (2H, m), 3.4 (1H, m), 3.95 (2H, t), 7.18 (1H, d), 7.34 (2H, t), 7.71 (1H, d), 8.05 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 3450, 3070, 2940, 2820, 1750, 1670, 1590, 1550 EXAMPLE 16 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-2H-thiazolo[3,2-a]-1,3,5-triazine-2,4(3H)-dione Hydrochloride Hemihydrate In 50 mℓ of methanol was suspended 2.95 g of 3-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-2H-thiazolo[3,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 15, and 2 mℓ of concentrated hydrochloric acid was added to the suspension. The crystals thus precipitated were collected by filtration and recrystallized from hot water containing a small amount of methanol to obtain 2.08 g of the entitled compound as a colorless powder. Melting Point: 278-280°C (decomposition) NMR Spectrum (DMSO-d₆) δ: 1.6-2.2 (4H, m), 2.9-3.8 (7H, m), 4.24 (2H, t), 7.23 (1H, d), 7.38 (2H, t), 7.92 (1H, d), 8.11 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 3470, 1740, 1670, 1600, 1580, 1550, 1420 Elemental Analysis for C₁₉H₁₉FN₄O₃S·HCℓ·1/2H₂O: Calcd. (%) C 50.95; H 4.73; N 12.51 Found (%) C 51.29; H 4.88; N 12.55 EXAMPLE 17 Synthesis of 3-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione In 50 mℓ of N,N-dimethylformamide were dissolved 1.67 g of 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 1-1), 3.64 g of 4-[bis(4-fluorophenyl)methylene]-1-(2-hydroxyethyl)piperidine and 3.15 g of triphenylphosphine, and 2.1 g of diethyl azodicarboxylate was added dropwise thereto with stirring under ice-cooling. After stirring for 30 minutes, the reaction mixture was concentrated to dryness under reduced pressure, and the residue was applied to a column contained with 180 g of silica gel and eluted with 3% methanol-containing chloroform to obtain 1.38 g of the entitled compound as a yellow oily substance. NMR Spectrum (CDCℓ₃) δ: 1.8-2.0 (4H, m), 2.3 (4H, m), 2.5-2.8 (8H, m), 3.8 (2H, t), 4.07 (2H, t), 6.96 (4H, d), 7.04 (4H, s) EXAMPLE 18 Synthesis of 3-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione Dihydrochloride In 50 mℓ of methanol was dissolved 1.38 g of 3-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 17, and 0.8 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. The residue was crystallized from a mixture of methanol and isopropanol and then recrystallized to obtain 1.03 g of the entitled compound as a colorless powder. Melting Point: 192-195°C NMR Spectrum (DMSO-d₆) δ: 1.7-2.0 (4H, m), 2.5-2.9 (6H, m), 3.0-3.4 (4H, m), 3.5-3.8 (4H, m), 4.19 (2H, t), 7.18 (8H, d), 9.85 (1H, s), 11.41 (1H, bs) IR Spectrum ν (KBr) cm⁻¹: 3450, 2550, 1760, 1730, 1620, 1510, 1450 Elemental Analysis for C₂₇H₂₈F₂N₄O₂·2HCℓ: Calcd. (%) C 58.81; H 5.48; N 10.16 Found (%) C 58.85; H 5.74; N 10.11 EXAMPLE 19 Synthesis of 3-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione In the manner described in Example 17, 7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 4-1) and 4-[bis(4-fluorophenyl)methylene]-1-(2-hydroxyethyl) piperidine were condensed in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃) δ: 2.2-2.5 (6H, m), 2.5-2.8 (6H, m), 3.02 (2H, t), 4.1 (4H, m), 6.99 (8H, m) EXAMPLE 20 Synthesis of 3-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione Dihydrochloride In 50 mℓ of methanol was dissolved 2.44 g of 3-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-7,8-dihydro-2H,6H-pyrrolo[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 19, and 1 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. The residue was crystallized from a mixture of methanol and isopropanol and then recrystallized to obtain 1.0 g of the entitled compound as a colorless powder. Melting Point: 173-180°C NMR Spectrum (DMSO-d₆) δ: 2.10 (2, m), 2.3-2.7 (4H, m), 2.90 (2H, t), 2.9-3.4 (4H, m), 3.5-3.8 (2H, m), 3.88 (2H, t), 4.14 (2H, t), 7.18 (8H, d), 11.22 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3450, 1725, 1650, 1600, 1580, 1510, 1450, 1420, 1220 Elemental Analysis for C₂₆H₂₆F₂N₄O₂·2HCℓ: Calcd. (%) C 58.11; H 5.25; N 10.43 Found (%) C 58.06; H 5.44; N 10.63 EXAMPLE 21 Synthesis of 3-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2H-thiazolo[3,2-a]-1,3,5-triazine-2,4(3H)-dione Hydrochloride In 20 mℓ of N,N-dimethylformamide were dissolved 1.0 g of 2H-thiazolo[3,2-a]-1,3,5-triazine-2,4(3H)-dione, 2.0 g of 1-(2-hydroxyethyl)-4-[bis(4-fluorophenyl)methylene]piperidine and 1.86 g of triphenylphosphine, and 1.25 g of diethyl azodicarboxylate was added dropwise thereto with stirring under ice-cooling. After stirring for 30 minutes, the reaction mixture was concentrated to dryness under reduced pressure. The residue was applied to a column contained with 120 g of silica gel and eluted with 4% methanol-containing chloroform. The eluate was concentrated to dryness under reduced pressure to obtain 2.05 g of the base of the entitled compound as an oily substance. The resulting base was dissolved in 50 mℓ of ethanol, and 0.5 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure. Ethanol was added to the residue, followed by concentration under reduced pressure repeatedly. The precipitated crystals were collected by filtration to obtain 1.76 g of the entitled compound as colorless crystals. Melting Point: 251-253°C NMR Spectrum (DMSO-d₆) δ: 2.4-2.8 (4H, m), 2.5-2.9 (4H, m), 3.6-3.8 (2H, m), 4.22 (2H, t), 7.18 (9H, m), 7.73 (1H, d), 11.2 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3450, 2340, 1740, 1650, 1580, 1550, 1500, 1420 Elemental Analysis for C₂₅H₂₂F₂N₄O₂S·HCℓ: Calcd. (%) C 58.08; H 4.48; N 10.84 Found (%) C 57.94; H 4.63; N 10.84 EXAMPLE 22 Synthesis of 3-[2-[4-(4-Chlorobenzoyl)piperidin1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione In the manner described in Example 1-2), 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 1-1) and 4-(4-chlorobenzoyl)-1-(2-hydroxyethyl)piperidine were condensed in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as colorless crystals. Melting Point: 142-144°C NMR Spectrum (CDCℓ₃) δ: 1.6-2.1 (8H, m), 2.1-2.4 (2H, m), 2.67 (2H, t), 2.82 (2H, t), 2.9-3.2 (3H, m), 3.85 (2H, t), 4.07 (2H, t), 7.43 (2H, d), 7.86 (2H, d) IR Spectrum ν (KBr) cm⁻¹: 3448, 3964, 2940, 2804, 1726, 1680, 1588 EXAMPLE 23 Synthesis of 3-[2-[4-(4-Chlorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione Hydrochloride In 30 mℓ of ethanol was dissolved 1.59 g of 3-[2-[4-(4-chlorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 22, and 2 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. The residue was crystallized from ethanol to obtain 1.26 g of the entitled compound as colorless crystals. Melting Point: 273-275°C IR Spectrum ν (KBr) cm⁻¹: 3448, 2952, 2504, 1726, 1670, 1594, 1480, 1442, 1410 Elemental Analysis for C₂₁H₂₅CℓN₄O₃·HCℓ: Calcd. (%) C 55.63; H 5.78; N 12.36 Found (%) C 55.20; H 5.92; N 12.05 EXAMPLE 24 Synthesis of 3-[2-Methyl-2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione In the manner described in Example 1-2), 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 1-1) and 4-(4-fluorobenzoyl)-1-(1-methyl-2-hydroxyethyl)piperidine were condensed in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as colorless crystals. Melting Point: 151-152°C NMR Spectrum (CDCℓ₃) δ: 1.00 (3H, d), 1.2-2.2 (8H, m), 2.2-2.9 (5H, m), 2.9-3.4 (3H, t), 3.4-4.3 (4H, m), 7.11 (2H, m), 7.89 (2H, m) EXAMPLE 25 Synthesis of 3-[2-Phenyl-2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione In the manner described in Example 1-2), 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione obtained in Example 1-1) and 4-(4-fluorobenzoyl)-1-(1-phenyl-2-hydroxyethyl)piperidine were condensed in N,N-dimethylformamide in the presence of triphenylphosphine and diethyl azodicarboxylate to obtain the entitled compound as a colorless oily substance. NMR Spectrum (CDCℓ₃) δ: 1.6 (1H, b), 1.66-1.84 (4H, bs), 1.9 (2H, m), 1.97 (2H, m), 2.33 (1H, b), 2.81 (2H, t), 2.90 (2H, bd), 3.0 (1H, bs), 3.24 (1H, bs), 3.82 (2H, m), 3.99 (1H, dd), 4.23 (1H, bs), 4.74 (1H, dd), 7.07 (2H, t), 7.23 (2H, d), 7.30-7.37 (3H, m), 7.86 (2H, dd) REFERENCE EXAMPLE 1 Synthesis of 2-[2-(4-Methylbenzenesulfonyloxy)ethyl]-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In 50 mℓ of pyridine was dissolved 3.6 g of 2-(2-hydroxyethyl)-1,2,4-triazo[4,3-a]pyridin-3(2H)-one, and 7.0 g of p-toluenesulfonyl chloride was added thereto under ice-cooling, followed by stirring for 6 hours. The reaction mixture was concentrated to dryness under reduced pressure. To the residue was added diluted hydrochloric acid, and the mixture was extracted with 150 mℓ of chloroform. The chloroform solution was applied to a column contained with 40 g of silica gel and eluted with chloroform to obtain 4.7 g of the entitled compound as colorless crystals. Melting Point: 149-151°C NMR Spectrum (CDCℓ₃) δ: 2.73 (3H, s), 4.21 (2H, t), 4.47 (2H, t), 6.48 (1H, m), 6.9-7.45 (4H, m), 7.6-7.85 (3H, m) IR Spectrum ν (KBr) cm⁻¹: 1720, 1650, 1360, 1195, 1180 REFERENCE EXAMPLE 2 Synthesis of 2-[2-(4-Methylbenzenesulfonyloxy)ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one 1) 2-(2-Hydroxyethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one: In 100 mℓ of ethanol was dissolved 5.4 g of 2-(2-hydroxyethyl)-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one, and 0.6 g of platinum oxide was added thereto, and the mixture was shaken in a hydrogen atmosphere. The catalyst was removed by filtration, and the filtrate was concentrated to dryness under reduced pressure to obtain 5.2 g of the entitled compound as colorless crystals. Melting Point: 99-100°C NMR Spectrum (CDCℓ₃) δ: 1.7-2.1 (4H, m), 2.68 (2H, t), 3.42 (1H, s), 3.62 (2H, t), 3.93 (4H, s) IR Spectrum ν (KBr) cm⁻¹: 3420, 1700, 1675, 1585, 1500, 1160 2)2-[2-(4-Methylbenzenesulfonyloxy)ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one: In the manner described in Reference Example 1, 2-(2-hydroxyethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one was tosylated to obtain the entitled compound as colorless crystals. Melting Point: 102-103°C NMR Spectrum (CDCℓ₃) δ: 1.7-2.1 (4H, m), 2.44 (3H, s), 2.63 (2H, t), 3.58 (2H, t), 3.98 (2H, t), 4.32 (2H, t), 7.33 (2H, d), 7.80 (2H, d) IR Spectrum ν (KBr) cm⁻¹: 1720, 1705, 1605, 1580, 1500, 1370, 1200, 1085 REFERENCE EXAMPLE 3 Synthesis of 2-[2-(4-Methylbenzenesulfonyloxy)ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one 1) 2-[2-(3,4,5,6-Tetrahydro-2H-pyran-2-yloxy)ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one: In 100 mℓ of acetone, 3.1 g of 2,5,6,7,8,9-hexahydro-3H-triazolo[4,3-a]azepin-3-one, 4.6 g of 2-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)ethyl bromide and 6.9 g of potassium carbonate were refluxed for 20 hours. The insoluble material was removed by filtration, and the filtrate was concentrated to dryness under reduced pressure. The residue was applied to a column contained with 30 g of silica gel and eluted with chloroform to obtain 2.7 g of the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃) δ: 1.2-2.3 (12H, m), 2.5-2.8 (2H, m), 3.3-4.05 (8H, m), 4.6 (1H, bs) 2)2-(2-Hydroxyethyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one: In 20 mℓ of ethanol was dissolved 2.7 g of 2-[2-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one, and 1 mℓ of concentrated hydrochloric acid was added thereto, followed by stirring for 30 minutes. The reaction mixture was concentrated to dryness under reduced pressure, and isopropanol was added to the residue, followed by filtration to give 1.8 g of the entitled compound as colorless crystals. Melting Point: 84-86°C NMR (CDCl₃) δ: 1.8 (6H, bs), 2.70 (2H, m), 3.20 (1H, bs), 3.77 (2H, m), 3.96 (4H, s) IR Spectrum ν (KBr) cm⁻¹: 3410, 1700, 1680, 1590, 1480 3) 2-[2-(4-Methylbenzenesulfonyloxy)ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one: In the manner described in Reference Example 1, 2-(2-hydroxyethyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one was tosylated to obtain the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃) δ: 1.77 (6H, bs), 2.43 (3H, s), 2.62 (2H, m), 3.74 (2H, m), 4.0 (2H, m), 4.31 (2H, t), 7.39 (2H, m), 7.83 (2H, m) REFERENCE EXAMPLE 4 Synthesis of 2-(2-Chloroethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In 500 mℓ of acetonitrile, 61.0 g of 5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one, 164 g of 1-bromo-2-chloroethane and 90.8 g of anhydrous potassium carbonate were refluxed for 8 hours. The insoluble material was removed by filtration, and the filtrate was concentrated to dryness under reduced pressure. The residue was applied to a column contained with 200 g of silica gel and eluted with a 20:1 (by volume) mixture of chloroform and ethanol. After concentration of the eluate, the residue was crystallized from a mixture of isopropyl ether and ethyl ether, followed by filtration to obtain 59.8 g of the entitled compound as colorless crystals. Melting Point: 46-49°C NMR Spectrum (CDCℓ₃) δ: 1.7-2.1 (4H, m), 2.68 (2H, t), 3.62 (2H, t), 3.77 (2H, t), 4.07 (2H, t) IR Spectrum ν (KBr) cm⁻¹: 1700, 1580, 1495, 1435, 1410 REFERENCE EXAMPLE 5 Synthesis of 2-(2-Chloroethyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one The entitled compound was obtained as colorless crystals from 2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one and 1-bromo-2-chloroethane in the manner described in Reference Example 4. Melting Point: 68-70°C NMR Spectrum (CDCℓ₃) δ: 1.52-2.0 (6H, m), 2.55-2.80 (2H, m), 3.62-3.95 (4H, m), 3.95-4.22 (2H, m) IR Spectrum ν (KBr) cm⁻¹: 1700, 1580, 1480 REFERENCE EXAMPLE 6 Synthesis of 2-(2-Chloroethyl)-2,5,6,7-tetrahydro-3H-pyrrolo[2,1-c]-1,2,4-triazol-3-one The entitled compound was obtained as colorless crystals from 2,5,6,7-tetrahydro-3H-pyrrolo[2,1-c]-1,2,4-triazol-3-one and 1-bromo-2-chloroethane in the manner described in Reference Example 4. Melting Point: 91-92°C NMR Spectrum (DMSO-d₆) δ: 2.3-2.58 (2H, m), 2.73 (2H, t-like), 3.64 (2H, t), 3.82-3.98 (4H, m) IR Spectrum ν (KBr) cm⁻¹: 3450, 2970, 1700, 1600, 1480 REFERENCE EXAMPLE 7 Synthesis of 2-(2-Chloroethyl)-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one The entitled compound was obtained as a colorless crystalline powder from 2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one and 1-bromo-2-chloroethane in the same manner as in Reference Example 4. Melting Point: 84-86°C NMR Spectrum (CDCℓ₃) δ: 3.65-3.84 (4H, q-like), 3.96-4.18 (4H, m), 4.64 (2H, s) IR Spectrum ν (KBr) cm⁻¹: 3420, 2940, 1710, 1580, 1500 REFERENCE EXAMPLE 8 Synthesis of 2-(2-Chloroethyl)-6,7-dihydro-5H-1,2,4-triazolo[3,4-b]-1,3-oxazin-3(2H)-one The entitled compound was obtained as colorless crystals from 6,7-dihydro-5H-1,2,4-triazolo[3,4-b]-1,3-oxazin-3(2H)-one and 1-bromo-2-chloroethane in the same manner as in Reference Example 4. Melting Point: 95-96°C NMR Spectrum (CDCl₃) δ: 2.16 (2H, m), 3.74 (4H, t), 4.01 (2H, dt), 4.37 (2H, t) REFERENCE EXAMPLE 9 Synthesis of 2-(2-Chloroethyl)-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-thiazin-3-one The entitled compound was obtained as a colorless crystalline powder from 2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-thiazin-3-one and 1-bromo-2-chloroethane in the manner described in Reference Example 4. Melting Point: 86-88°C NMR Spectrum (CDCℓ₃) δ: 2.98 (2H, t), 3.68 (2H, m), 4.10 (2H, t), 4.8 (4H, m) EXAMPLE 26 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one 2-(2-Chloroethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one (26.8 g), 31.5 g of sodium iodide and 400 mℓ of acetonitrile were refluxed for 30 minutes. To the reaction mixture were added 38.2 g of 4-[bis(4-fluorophenyl)methylene]piperidine and 27.6 g of potassium carbonate, followed by heating at reflux for 8 hours. The insoluble material was removed by filtration, and the filtrate was concentrated to dryness under reduced pressure. The residue was dissolved in 200 mℓ of chloroform, and the solution was applied to a column contained with 550 g of silica gel and eluted with chloroform to obtain 53.0 g of the entitled compound as an oily substance. NMR Spectrum (CDCl₃) δ: 1.7-2.2 (4H, m), 2.2-2.9 (12H, m), 3.6 (2H, t-like), 3.92 (2H, t), 6.9-7.2 (8H, m) EXAMPLE 27 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]-pyridin-3(2H)-one In 100 mℓ of tetrahydrofuran were dissolved 2.0 g of 2-[2-(4-methylbenzenesulfonyloxy)ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one, 2.8 g of 4-[bis(4-fluorophenyl)methylene]piperidine and 2 mℓ of triethylamine, and the solution was refluxed for 16 hours. The reaction mixture was concentrated to dryness under reduced pressure, and 100 mℓ of water was added to the residue, followed by extraction with 100 mℓ of chloroform. The chloroform solution was concentrated to dryness under reduced pressure, and the residue was applied to a column contained with 30 g of silica gel and eluted with a 20:1 (by volume) mixture of chloroform and ethanol to obtain 2.4 g of the entitled compound as an oily substance. EXAMPLE 28 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride Ethanolate In 200 mℓ of ethanol was dissolved 53.0 g of 2-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 26, and 20 mℓ of concentrated hydrochloric acid was added to the solution. The mixture was concentrated to dryness under reduced pressure. The residue was crystallized from a small amount of ethanol, and a 1:1 (by volume) mixture of ethanol and ethyl ether was added, followed by filtration to obtain 39.5 g of the entitled compound as colorless crystals. Melting Point: 129-131°C NMR Spectrum (DMSO-d₆) δ: 1.07 (3H, t), 1.5-2.0 (4H, b), 2.2-2.75 (4H, m), 2.8-3.8 (10H, m), 3.43 (2H, q), 4.12 (2H, t-like), 7.14 (4H, s), 7.23 (4H, s) IR Spectrum ν (KBr) cm⁻¹: 1695, 1599, 1506, 1449, 1218 Elemental Analysis for C₂₆H₂₈F₂N₄O·HCℓ·C₂H₆O: Calcd. (%) C 63.09; H 6.62; N 10.51 Found (%) C 62.78; H 6.73; N 10.65 EXAMPLE 29 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride Isopropanolate In 50 mℓ of isopropanol was dissolved 2.3 g of 2-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 27, and 2 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from a small amount of isopropanol. A 1:1 (by volume) mixture of isopropanol and ethyl ether was added to the crystal, followed by filtration to obtain 2.3 g of the entitled compound as colorless crystals. Melting Point: 139-141°C NMR Spectrum (DMSO-d₆) δ: 1.04 (6H, d), 1.6-2.0 (4H, bs), 2.2-2.75 (4H, m), 2.9-3.8 (10H, bs), 3.8 (1H, q), 4.1 (2H, t-like), 7.16 (4H, s), 7.23 (4H, s) IR Spectrum ν (KBr) Cm⁻¹: 1695, 1596, 1506, 1452, 1212 Elemental Analysis for C₂₆H₂₈F₂N₄O·HCℓ·C₃H₈O: Calcd. (%) C 63.67; H 6.82; N 10.24 Found (%) C 63.39; H 6.59; N 10.35 EXAMPLE 30 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one hydrochloride ethanolate (39.0 g) obtained in Example 28 was recrystallized twice from a mixture of a small amount of methanol and ethyl ether to obtain 20 g of the entitled compound as colorless crystals. Melting Point: 183-185°C NMR Spectrum (DMSO-d₆) δ: 1.68-2.0 (4H, m), 2.3-3.8 (14H, m), 4.11 (2H, t-like), 7.18 (4H, s), 7.22 (4H, s) NMR Spectrum (D₂O) δ: 1.8-2.35 (4H, b), 2.6-3.1 (6H, bm), 3.4-4.05 (8H, m), 4.38-4.65 (2H, b), 7.0-7.5 (8H, m) IR Spectrum ν (KBr) cm⁻¹: 2380, 1710, 1600, 1580, 1505, 1210 Elemental Analysis for C₂₆H₂₈F₂N₄O·HCℓ: Calcd. (%) C 64.13; H 6.00; N 11.51 Found (%) C 63.85; H 6.11; N 11.44 EXAMPLE 31 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Monomaleate In 50 mℓ of ethanol was dissolved 4.5 g of 2-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 26, and 1.16 g of maleic acid was added to the solution. The mixture was concentrated to dryness under reduced pressure, and the residue was recrystallized from a mixture of ethanol and ethyl ether to obtain 4.7 g of the entitled compound as colorless crystals. Melting Point: 144-145°C NMR Spectrum (DMSO-d₆) δ: 1.74-2.02 (4H, m), 2.13-2.76 (4H, m), 2.86-3.63 (10H, m), 4.01 (2H, t-like), 6.08 (2H, s), 7.14 (4H, s), 7.22 (4H, s) IR Spectrum ν (KBr) cm⁻¹: 1710, 1581, 1509, 1455, 1356, 1224 Elemental Analysis for C₂₆H₂₈F₂N₄O·C₄H₄O₄: Calcd. (%) C 63.59; H 5.69; N 9.89 Found (%) C 63.47; H 5.68; N 9.70 EXAMPLE 32 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one In the manner described in Example 26, the entitled compound was obtained as an oily substance from 2-(2-chloroethyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one and 4-[bis(4-fluorophenyl)methylene]piperidine. NMR Spectrum (CDCℓ₃) δ: 1.53-1.95 (6H, m), 2.2-2.47 (4H, m), 2.47-2.87 (8H, m), 3.6-3.84 (2H, m), 3.92 (2H, t), 6.9-7.2 (8H, m) EXAMPLE 33 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one Hydrochloride Ethanolate In 200 mℓ of ethanol was dissolved 30.0 g of 2-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one obtained in Example 32, and 20 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from a small amount of ethanol. A 1:1 (by volume) mixture of ethanol and ethyl ether was added to the crystal, followed by filtration to obtain 22.3 g of the entitled compound as colorless crystals. Melting Point: 118-122°C NMR Spectrum (DMSO-d₆) δ: 1.07 (3H, t), 1.4-1.95 (6H, b), 2.22-2.8 (4H, m), 2.8-4.0 (10H, m), 3.43 (2H, q), 4.15 (2H, t-like), 7.16 (4H, s), 7.24 (4H, s) IR Spectrum ν (KBr) cm⁻¹: 1695, 1587, 1506, 1482, 1443, 1218 Elemental Analysis for C₂₇H₃₀F₂N₄O·HCℓ·C₂H₆O: Calcd. (%) C 59.28; H 6.82; N 10.24 Found (%) C 68.95; H 6.97; N 10.01 EXAMPLE 34 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one Hydrochloride Hemihydrate 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one hydrochloride ethanolate (22.0 g) obtained in Example 33 was recrystallized twice from a mixture of a small amount of methanol and ethyl ether to obtain 17.0 g of the entitled compound as colorless crystals. Melting Point: 119-121°C NMR Spectrum (DMSO-d₆ + D₂O) δ: 1.4-1.96 (6H, m), 2.2-4.0 (14H, m), 4.15 (2H, t-like), 7.18 (4H, s), 7.26 (4H, s) IR Spectrum ν (KBr) cm⁻¹: 1700, 1590, 1505, 1480, 1440, 1220 Elemental Analysis for C₂₇H₃₀F₂N₄O·HCℓ·1/2H₂O: Calcd. (%) C 63.58; H 6.33; N 10.99 Found (%) C 63.66; H 6.47; N 10.97 EXAMPLE 35 Synthesis of 2-[2-[4-[(4-Fluorophenyl)(phenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one In the manner described in Example 27, the entitled compound was obtained as an oily substance from 2-[2-(4-methylbenzenesulfonyloxy)ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one and 4-[(4-fluorophenyl)(phenyl)methylene]piperidine. NMR Spectrum (CDCℓ₃) δ: 1.5-2.0 (6H, m), 2.28-2.9 (12H, m), 3.68-3.9 (2H, m), 3.92 (2H, t), 6.8-7.5 (9H, m) EXAMPLE 36 Synthesis of 2-[2-[4-[(4-Fluorophenyl)(phenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one Hydrochloride Ethanolate In 20 mℓ of ethanol was dissolved 1.9 g of 2-[2-[4-[(4-fluorophenyl)(phenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one obtained in Example 35, and 1 mℓ of hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from a small amount of ethanol. A 1:1 (by volume) mixture of ethanol and ethyl ether was added thereto, followed by filtration to give 1.4 g of the entitled compound as colorless crystals. Melting Point: 118-120°C NMR Spectrum (DMSO-d₆) δ: 1.05 (3H, t), 1.3-1.9 (6H, m), 2.2-2.8 (6H, m), 2.8-3.9 (8H, m), 3.45 (2H, q), 4.13 (2H, t-like), 7.05-7.50 (9H, m) IR Spectrum ν (KBr) cm⁻¹: 1715 Elemental Analysis for C₂₇H₃₁FN₄O·HCℓ·C₂H₆O: Calcd. (%) C 65.83; H 7.24; N 10.06 Found (%) C 65.52; H 7.26; N 10.25 EXAMPLE 37 Synthesis of 2-[2-[4-(Diphenylmethylene)piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one Hydrochloride Ethanolate In 100 mℓ of tetrahydrofuran were dissolved 3.4 g of 2-[2-(4-methylbenzenesulfonyloxy)ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one, 3.0 g of 4-(diphenylmethylene)piperidine and 2 mℓ of triethylamine, and the solution was refluxed for 16 hours. The reaction mixture was concentrated to dryness under reduced pressure, and 100 mℓ of water was added to the residue. The mixture was extracted with 100 mℓ of chloroform, and the chloroform solution was concentrated to dryness under reduced pressure. The residue was subjected to column chromatography using 20 g of silica gel and eluted with a 20:1 (by volume) mixture of chloroform and ethanol to obtain an oily substance. The product was dissolved in 100 mℓ of ethanol, and 2 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. The residue was crystallized from isopropanol and then recrystallized from a mixture of ethanol and ethyl ether to obtain 3.4 g of the entitled compound as colorless crystals. Melting Point: 117-119°C NMR Spectrum (CDCℓ₃) δ: 1.06 (3H, t), 1.4-1.9 (6H, bs), 2.2-2.8 (6H, m), 2.8-3.8 (8H, m), 3.48 (2H, q), 4.13 (2H, t-like), 7.05-7.60 (10H, m) IR Spectrum ν (KBr) cm⁻¹: 1705, 1590 Elemental Analysis for C₂₇H₃₂N₄O·HCℓ·C₂H₆O: Calcd. (%) C 68.15; H 7.69; N 10.96 Found (%) C 67.37; H 7.48; N 11.01 EXAMPLE 38 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride In the manner described in Example 37, the entitled compound was obtained as colorless crystals from 2-[2-(4-methylbenzenesulfonyloxy)ethyl]-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one and 4-[bis(4-fluorophenyl)methylene]piperidine. Melting Point: 127-129°C NMR Spectrum (DMSO-d₆) δ: 2.2-3.8 (10H, m), 4.42 (2H, t-like), 6.70 (1H, m), 7.13 (4H, s), 7.30 (4H, s), 7.30 (2H, m), 7.93 (1H, d) IR Spectrum ν (KBr) cm⁻¹: 1710, 1640, 1600, 1540, 1505, 1440, 1220 Elemental Analysis for C₂₆H₂₄F₂N₄O·HCℓ: Calcd. (%) C 64.66; H 5.22; N 11.60 Found (%) C 64.34; H 5.54; N 11.52 EXAMPLE 39 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7-tetrahydro-3H-pyrrolo[2,1-c]-1,2,4-triazol-3-one In the manner described in Example 26, the entitled compound was obtained as an oily substance from 2-(2-chloroethyl)-2,5,6,7-tetrahydro-3H-pyrrolo[2,1-c]-1,2,4-triazol-3-one and 4-[bis(4-fluorophenyl)methylene]piperidine. NMR Spectrum (CDCℓ₃) δ: 2.3-3.0 (14H, m), 3.7-4.0 (4H, m), 6.9-7.2 (8H, m) EXAMPLE 40 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7-tetrahydro-3H-pyrrolo[2,1-c]-1,2,4-triazol-3-one Hydrochloride Methanolate In ethanol was dissolved 2.5 g of 2-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,7-tetrahydro-3H-pyrrolo[2,1-c]-1,2,4-triazol-3-one obtained in Example 39, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from a mixture of methanol and isopropanol to obtain 1.65 g of the entitled compound as colorless crystals. Melting Point: 123-125°C NMR Spectrum (DMSO-d₆) δ: 2.8-3.4 (8H, m), 3.0-3.6 (9H, m), 3.63 (2H, t), 4.10 (2H, t-like), 7.14 (4H, s), 7.22 (4H, s), 11.4 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3400, 2950, 2550, 1680, 1600, 1500, 1220 Elemental Analysis for C₂₅H₂₆F₂N₄O·HCℓ·CH₄O: Calcd. (%) C 61.84; H 6.19; N 11.09 Found (%) C 62.01; H 6.37; N 11.39 EXAMPLE 41 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one In the manner described in Example 26, the entitled compound was obtained as an oily substance from 2-(2-chloroethyl)-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one and 4-[bis(4-fluorophenyl)methylene]piperidine. NMR Spectrum (CDCℓ₃) δ: 2.37 (4H, m), 2.54 (4H, m), 2.72 (2H, t), 3.6-4.1 (6H, m), 4.62 (2H, s), 6.84-7.03 (8H, m) EXAMPLE 42 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one Hydrochloride In methanol was dissolved 3.3 g of 2-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one obtained in Example 41, and 1 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. The residue was crystallized from ethanol and then recrystallized from a mixture of methanol and isopropyl alcohol to obtain 1.5 g of the entitled compound as colorless crystals. Melting Point: 139-144°C NMR Spectrum (DMSO-d₆) δ: 2.4-2.7 (4H, m), 3.0-3.5 (6H, m), 3.56 (2H, t), 3.97 (2H, t), 4.15 (2H, t), 4.62 (2H, s), 7.14 (4H, s), 7.22 (4H, s), 11.29 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3550, 2540, 1710, 1600, 1510, 1440 Elemental Analysis for C₂₅H₂₆F₂N₄O₂·HCℓ: Calcd. (%) C 61.41; H 5.56; N 11.46 Found (%) C 61.04; H 5.83; N 11.36 EXAMPLE 43 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-6,7-dihydro-5H-1,2,4-triazolo[3,4-b]-1,3-oxazin-3(2H)-one In the manner described in Example 26, the entitled compound was obtained as an oily substance from 2-(2-chloroethyl)-6,7-dihydro-5H-1,2,4-triazolo[3,4-b]-1,3-oxazin-3(2H)-one and 4-[bis(4-fluorophenyl)methylene]piperidine. NMR Spectrum (CDCℓ₃) δ: 2.0-2.6 (10H, m), 2.70 (2H, t), 3.6-3.9 (4H, m), 4.34 (2H, m), 6.8-7.03 (8H, m) EXAMPLE 44 Synthesis of 2-[2-[4-Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-6,7-dihydro-5H-1,2,4-triazolo[3,4-b]-1,3-oxazin-3(2H)-one Hydrochloride Hemihydrate In 50 mℓ of ethanol was dissolved 1.6 g of 2-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-6,7-dihydro-5H-1,2,4-triazolo[3,4-b]-1,3-oxazin-3(2H)-one obtained in Example 43, and 0.5 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. The residue was crystallized from ethanol, and then recrystallized from a mixture of methanol and isopropanol to obtain 0.85 g of the entitled compound as colorless crystals. Melting Point: 138-139°C NMR Spectrum (DMSO-d₆) δ: 2.1 (2H, m), 2.5 (2H, m), 3.0-3.7 (10H, m), 4.01 (2H, t), 4.35 (2H, t), 7.13 (4H, s), 7.21 (4H, s), 10.86 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3450, 1710, 1620, 1510 Elemental Analysis for C₂₅H₂₆F₂N₄O₂·HCℓ·1/2H₂O: Calcd. (%) C 60.30; H 5.67; N 11.25 Found (%) C 60.19; H 5.65; N 11.12 EXAMPLE 45 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-thiazin-3-one In the manner described in Example 26, the entitled compound was obtained as an oily substance from 2-(2-chloroethyl)-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-thiazin-3-one and 4-[bis(4-fluorophenyl)methylene]piperidine. NMR Spectrum (CDCℓ₃) δ: 2.3-2.6 (8H, m), 2.75 (2H, t), 2.97 (2H, t), 3.66 (2H, s), 3.85 (2H, t), 3.93 (2H, t), 6.96 (4H, d), 7.04 (4H, s) EXAMPLE 46 Synthesis of 2-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-thiazin-3-one Hydrochloride Hemihydrate In 50 mℓ of ethanol was dissolved 2.1 g of 2-[2-[4-[bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-thiazin-3-one obtained in Example 45, and 0.5 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness under reduced pressure. The residue was crystallized from isopropanol and then recrystallized from a mixture of methanol and isopropyl ether to obtain 1.73 g of the entitled compound as colorless crystals. Melting Point: 178-180°C NMR Spectrum (DMSO-d₆) δ: 2.9-3.8 (14H, m), 3.75 (2H, s), 4.16 (2H, t), 7.18 (8H, d), 11.2 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3450, 1720, 1600, 1506 Elemental Analysis for C₂₅H₂₆F₂N₄OS·HCℓ·1/2H₂O: Calcd. (%) C 58.42; H 5.49; N 10.90 Found (%) C 58.31; H 5.78; N 10.77 EXAMPLE 47 Synthesis of 2-[2-[4-[Bis(4-methoxyphenyl)methylene]piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride Monohydrate 2-(2-Chloroethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]-pyridin-3(2H)-one (2.08 g), 3.1 g of sodium iodide and 100 mℓ of acetonitrile were refluxed for 30 minutes, and 3.1 g of 4-[bis(4-methoxyphenyl)methylene]piperidine and 2.8 g of potassium carbonate were added thereto, followed by refluxing for 18 hours. The insoluble material was removed by filtration, and the filtrate was concentrated to dryness under reduced pressure. The residue was dissolved in 100 mℓ of chloroform, and the solution was applied to a column contained with 130 g of silica gel and eluted with a 15:1 (by volume) mixture of chloroform and ethanol. The eluate was concentrated to dryness, and the resulting residue was dissolved in ethanol, and 1 mℓ of concentrated hydrochloric acid was added thereto, followed by concentration to dryness. The residue was recrystallized from a mixture of ethanol and ethyl ether to obtain 0.85 g of the entitled compound as colorless crystals. Melting Point: 199-203°C NMR Spectrum (DMSO-d₆) δ: 1.7-2.0 (4H, m), 2.5-3.8 (14H, m), 3.8 (6H, s), 4.17 (2H, m), 6.9 (4H, d), 7.1 (4H, d) Elemental Analysis for C₂₈H₃₄N₄O₃·HCℓ·H₂O: Calcd. (%) C 63.56; H 7.05; N 10.59 Found (%) C 63.62; H 6.72; N 10.35 REFERENCE EXAMPLE 10 Synthesis of 2-(3-Chloropropyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one 1) 2-[3-(3,4,5,6-Tetrahydro-2H-pyran-2-yloxy)propyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one: 5,6,7,8-Tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one (4.8 g), 7.7 g of 3-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)propyl bromide and 6.9 g of anhydrous potassium carbonate were refluxed in 100 mℓ of acetonitrile for 20 hours. The insoluble material was removed by filtration, and the filtrate was concentrated to dryness under reduced pressure. The residue was applied to a column contained with 30 g of silica gel and eluted with chloroform to obtain 7.7 g of the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃); δ: 1.3-1.9 (6H, m), 1.8-2.0 (6H, m), 2.55-2.85 (2H, m), 3.3-4.1 (8H, m), 4.6 (1H, bs) 2) 2-(3-Hydroxypropyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one: In 50 mℓ of ethanol was dissolved 7.7 g of 2-[3-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)propyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one, and 10 mℓ of concentrated hydrochloric acid was added thereto, followed by stirring for 24 hours. The reaction mixture was concentrated to dryness under reduced pressure, and the residue was extracted from 100 mℓ of chloroform. The chloroform solution was applied to a column contained with 30 g of silica gel and eluted with a 20:1 (by volume) mixture of chloroform and ethanol to obtain 3.0 g of the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃) δ: 1.50-2.05 (6H, bs), 2.70 (2H, m), 3.20 (2H, bs), 3.63 (2H, t), 3.90 (2H, m), 3.98 (2H, t) 3) 2-(3-Chloropropyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one: In 50 mℓ of pyridine was dissolved 3.0 g of 2-(3-hydroxypropyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one, and 4.3 g of p-toluenesulfonyl chloride was added thereto under ice-cooling, followed by stirring for 16 hours. The reaction mixture was concentrated to dryness under reduced pressure, and diluted hydrochloric acid was added to the residue. The mixture was extracted with 100 mℓ of chloroform, and the chloroform solution was concentrated to dryness under reduced pressure. The residue was applied to a column contained with 20 g of silica gel and eluted with chloroform to obtain 1.4 g of the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃) δ: 1.50-2.00 (4H, bs), 2.23 (2H, q), 2.68 (2H, m), 3.63 (2H, m), 3.82 (2H, m), 3.94 (2H, m) REFERENCE EXAMPLE 11 Synthesis of 2-(3-chloropropyl)-2,5,6,7,8,9hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one 1) 2-[3-(3,4,5,6-Tetrahydro-2H-pyran-2-yloxy)propyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one: In the manner described in Reference Example 10-1), the entitled compound was obtained as an oily substance from 2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one and 3-(3,4,5,6-tetrahydropyran-2-yloxy)propyl bromide. 2) 2-(3-Hydroxypropyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one: In the manner described in Reference Example 10-2), 2-[3-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)propyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one was treated with an acid to obtain the entitled compound as colorless crystals. Melting Point: 62-64°C NMR Spectrum (CDCℓ₃) δ: 1.50-2.05 (8H, bs), 2.70 (2H, m), 3.20 (1H, bs), 3.63 (2H, t), 3.90 (2H, m), 3.98 (2H, t) IR Spectrum ν (KBr) cm⁻¹: 3435, 1700, 1685, 1590, 1490, 1450, 1405 3) 2-(3-Chloropropyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one: In the manner described in Reference Example 10-3), 2-(3-hydroxypropyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one was treated with p-toluenesulfonyl chloride to obtain the entitled compound as an oily substance. NMR Spectrum (CDCℓ₃) δ: 1.50-2.00 (6H, bs), 2.23 (2H, q), 2.68 (2H, m), 3.63 (2H, m), 3.82 (2H, m), 3.94 (2H, m) REFERENCE EXAMPLE 12 Synthesis of 4-(2-Fluoro-4-morpholinobenzoyl)piperidine Hydrochloride In 30 mℓ of N,N-dimethylformamide were suspended 2.30 g of 1-acetyl-4-(2,4-difluorobenzoyl)piperidine, 0.9 mℓ of morpholine and anhydrous potassium carbonate, and the suspension was heated at 80°C for 4 days with stirring. The reaction mixture was concentrated to dryness under reduced pressure, and 100 mℓ of water was added to the residue. The mixture was extracted with 100 mℓ of chloroform. The chloroform solution was dried over anhydrous sodium sulfate. The solution was concentrated to dryness under reduced pressure, and the resulting oily substance was applied to a column contained with 50 g of silica gel and eluted with a 20:1 (by volume) mixture of chloroform and ethanol to obtain 2.63 g of a mixture of 1-acetyl-4-(4-fluoro-2-morpholinobenzoyl)piperidine and 1-acetyl-4-(2-fluoro-4-morpholinobenzoyl)piperidine as a pale yellow oily substance. To the product was added 20 mℓ of concentrated hydrochloric acid, followed by refluxing for 16 hours. The reaction mixture was extracted with 100 mℓ of chloroform, and the aqueous layer was separated. After the aqueous layer was made basic with potassium carbonate, the mixture was extracted with 100 ml of chloroform, and the chloroform solution was dried sodium sulfate. The solution was concentrated to dryness under reduced pressure, and the residue was dissolved in 50 mℓ of ethanol. To the solution was added 2 mℓ of concentrated hydrochloric acid, followed by concentration to dryness under reduced pressure. An adequate amount of ethanol was added to the residue which was crystallized to obtain 0.6 g of the entitled compound as colorless crystals. Melting Point: 255°C NMR Spectrum (DMSO-d₆) δ: 1.56-2.13 (4H, m), 2.72-3.57 (9H, m), 3.66-3.93 (4H, m), 6.69-7.08 (2H, m), 7.72 (1H, t) IR Spectrum ν (KBr) cm⁻¹: 3410, 2950, 2920, 2790, 2710, 2640, 2500, 1680, 1620, 1520 REFERENCE EXAMPLE 13 Synthesis of 4-(4-Fluoro-2-moroholinobenzoyl)piperidine Hydrochloride After filtration of 4-(2-fluoro-4-morpholinobenzoyl)piperidine hydrochloride in Reference Example 12, the mother liquor was concentrated to dryness under reduced pressure, and the residue was crystallized from a mixture of ethanol and acetone to obtain 1.44 g of the entitled compound. Melting Point: 177-181°C NMR Spectrum (DMSO-d₆) δ: 1.59-2.06 (4H, m), 2.71-3.42 (9H, m), 3.62-3.94 (4H, m), 6.76-7.15 (2H, m), 7.35 (1H, dd) IR Spectrum ν (KBr) cm⁻¹: 3450, 2920, 2820, 2710, 2480, 1655, 1615, 1550 EXAMPLE 48 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In 100 mℓ of tetrahydrofuran were dissolved 3.3 g of 2-[2-(4-methylbenzenesulfonyloxy)ethyl]-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one, 2.8 g of 4-(4-fluorobenzoyl)piperidine and 3 mℓ of triethylamine, and the solution was refluxed for 24 hours. The reaction mixture was concentrated to dryness under reduced pressure, and to the residue was added 100 mℓ of water, followed by extracting with 100 mℓ of chloroform. The chloroform solution was applied to a column contained with 40 g of silica gel and eluted with a 20:1 (by volume) mixture of chloroform and ethanol to obtain 1.9 g of the entitled compound as pale yellow crystals. Melting Point: 118-119°C NMR Spectrum (CDCℓ₃) δ: 1.6-2.0 (4H, m), 2.0-2.4 (2H, m), 2.82 (2H, t), 2.85-3.3 (3H, m), 4.10 (2H, t), 6.43 (1H, m), 5.90-7.25 (4H, m), 7.6-8.04 (3H, m) IR Spectrum ν (KBr) cm⁻¹: 1710, 1680, 1600, 1545 EXAMPLE 49 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride Hemihydrate In 30 mℓ of methanol was dissolved 1.8 g of 2-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 48, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was recrystallized from a mixture of methanol and ethyl ether to obtain 1.2 g of the entitled compound as pale yellow crystals. Melting Point: 225-237°C NMR Spectrum (DMSO-d₆) δ: 1.8-2.2 (4H, bm), 2.9-4.0 (7H, m), 4.42 (2H, t-like), 6.65 (1H, m), 7.2-7.6 (4H, m), 7.8-8.25 (3H, m) IR Spectrum ν (KBr) cm⁻¹: 1710, 1670, 1640, 1600, 1545, 1445 Elemental Analysis for C₂₀H₂₁FN₄O₂·HCℓ·1/2H₂O: Calcd. (%) C 58.04; H 5.60; N 13.54 Found (%) C 57.79; H 5.56; N 13.41 EXAMPLE 50 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In the manner described in Example 48, the entitled compound was obtained as pale yellow crystals from 2-[2-(4-methylbenzenesulfonyloxy)ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one and 4-(4-fluorobenzoyl)piperidine. Melting Point: 105-106°C NMR Spectrum (CDCl₃) δ: 1.6-2.05 (8H, m), 2.05-2.52 (2H, m), 2.53-2.90 (4H, m), 2.9-3.4 (3H, m), 3.4-3.75 (2H, m), 3.93 (2H, t), 7.22 (2H, t), 8.03 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 1705, 1685, 1600, 1575, 1500 EXAMPLE 51 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride In 100 mℓ of ethanol was dissolved 3.5 g of 2-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 50, and 2 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from acetone to obtain 3.2 g of the entitled compound as colorless crystals. Melting Point: 217-219°C NMR Spectrum (DMSO-d₆) δ: 1.6-2.4 (8H, m), 2.4-2.8 (2H, m), 2.8-4.0 (11H, m), 7.25-7.57 (2H, m), 7.95-8.25 (2H, m) IR Spectrum ν (KBr) cm⁻¹: 1695, 1598, 1225 Elemental Analysis for C₂₀H₂₅FN₄O₂·HCl: Calcd. (%) C 58.75; H 6.41; N 13.70 Found (%) C 58.67; H 6.42; N 13.63 EXAMPLE 52 Synthesis of 2-[3-[4-(4-Fluorobenzoyl)piperidin-1-yl]propyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one 2-(3-Chloropropyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one (1.4 g) and 3 g of sodium iodide were refluxed in 100 mℓ of tetrahydrofuran for 20 minutes. To the reaction mixture were added 2.1 g of 4-(4-fluorobenzoyl)piperidine and 2 mℓ of triethylamine, followed by refluxing for 8 hours. The reaction mixture was concentrated to dryness under reduced pressure, and the residue was applied to a column contained with 30 g of silica gel and eluted with a 20:1 (by volume) mixture of chloroform and ethanol. The resulting oily substance was crystallized from isopropyl ether to obtain 1.2 g of the entitled compound as pale yellow crystals. Melting Point: 136-137°C NMR Spectrum (CDCℓ₃) δ: 1.6-2.3 (12H, m), 2.34-2.59 (2H, m), 2.59-2.8 (2H, m), 2.8-3.18 (2H, m), 3.18-3.4 (1H, m), 3.4-3.7 (2H, m), 3.7-3.94 (2H, t), 7.20 (2H, t), 8.03 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 1695, 1670, 1595, 1590, 1500, 1450, 1410 EXAMPLE 53 Synthesis of 2-[3-[4-(4-Fluorobenzoyl)piperidin-1-yl]propyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride Hemihydrate In 50 mℓ of ethanol was dissolved 1.1 g of 2-[3-[4-(4-fluorobenzoyl)piperidin-1-yl]propyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 52, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from acetone to obtain 1.0 g of the entitled compound as colorless crystals. Melting Point: 209-211°C NMR Spectrum (DMSO-d₆) δ: 1.5-2.2 (10H, m), 2.4-2.7 (2H, m), 2.8-3.9 (9H, m), 4.13 (2H, t-like), 7.22-7.60 (2H, m), 7.9-7.22 (2H, m) IR Spectrum ν (KBr) cm⁻¹: 1690, 1595, 1580 Elemental Analysis for C₂₁H₂₇FN₄O₂·HCℓ·1/2H₂O: Calcd. (%) C 58.36; H 6.77; N 12.97 Found (%) C 58.56; H 6.91; N 12.75 EXAMPLE 54 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one In the manner described in Example 48, the entitled compound was obtained as an oily substance from 2-[2-(4-methylbenzenesulfonyloxy)ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one and 4-(4-fluorobenzoyl)piperidine. NMR Spectrum (CDCℓ₃) δ: 1.75 (10H, bs), 2.0-2.4 (2H, m), 2.5-2.75 (4H, m), 2.9-3.3 (3H, m), 2.77 (2H, t), 3.90 (2H, t), 7.0-7.45 (2H, m), 7.8-8.1 (2H, m) EXAMPLE 55 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one Hydrochloride In 50 mℓ of ethanol was dissolved 1.1 g of 2-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]]azepin-3-one obtained in Example 54, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from acetone to obtain 0.9 g of the entitled compound as colorless crystals. Melting Point: 229-231°C NMR Spectrum (DMSO-d₆) δ: 1.4-1.85 (6H, m), 1.85-2.2 (4H, m), 2.57-2.8 (2H, m), 2.9-4.0 (9H, m), 4.14 (2H, t-like), 7.25-7.6 (2H, m), 7.96-8.25 (2H, m) IR Spectrum ν (KBr) cm⁻¹: 1695, 1597, 1580 Elemental Analysis for C₂₁H₂₇FN₄O₂·HCℓ: Calcd. (%) C 59.64; H 6.44; N 13.25 Found (%) C 59.82; H 6.74; N 13.01 EXAMPLE 56 Synthesis of 2-[3-[4-(4-Fluorobenzoyl)piperidin-1-yl]propyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one In the manner described in Example 52, the entitled compound was obtained as an oily substance from 2-(3-chloropropyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one and 4-(4-fluorobenzoyl)piperidine. NMR Spectrum (CDCℓ₃) δ: 1.55 (12H, m), 2.5 (2H, t), 2.0-3.3 (5H, m), 2.6-2.8 (2H, m), 3.6-3.95 (4H, m), 7.0-7.35 (2H, m), 7.8-8.1 (2H, m) EXAMPLE 57 Synthesis of 2-[3-[4-(4-Fluorobenzoyl)piperidin-1-yl]propyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one Hydrochloride In 50 mℓ of ethanol was dissolved 0.7 g of 2-[3-[4-(4-fluorobenzoyl)piperidin-1-yl]propyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one obtained in Example 56, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from acetone to obtain 0.45 g of the entitled compound as colorless crystals. Melting Point: 213-215°C NMR Spectrum (DMSO-d₆) δ: 1.1-1.82 (6H, m), 1.82-2.4 (6H, m), 2.5-2.8 (2H, m), 2.8-4.0 (11H, m), 7.0-7.6 (2H, m), 7.8-8.4 (2H, m) IR Spectrum ν (KBr) cm⁻¹: 1700, 1680, 1595, 1580 Elemental Analysis for C₂₂H₂₉FN₄O₂·HCℓ: Calcd. (%) C 60.47; H 6.92; N 12.82 Found (%) C 60.57; H 6.86; N 12.67 EXAMPLE 58 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-2,5,6,7-tetrahydro-3H-pyrrolo[2,1-c]-1,2,4-triazol-3-one Hydrochloride In the manner described in Example 52, the entitled compound was obtained as an oily substance from 2-(2-chloroethyl)-2,5,6,7-tetrahydro-3H-pyrrolo[2,1-c]-1,2,4-triazol-3-one and 4-(4-fluorobenzoyl)piperidine. The product was dissolved in 50 mℓ of ethanol, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was recrystallized from a mixture of ethanol and isopropyl ether to obtain 0.65 g of the entitled compound as a colorless powder. Melting Point: 215-217°C NMR Spectrum (DMSO-d₆) δ: 1.8-2.2 (4H, m), 2.3-2.5 (2H, m), 2.66 (2H, t-like), 3.0-3.7 (7H, m), 3.64 (2H, t), 4.10 (2H, t), 7.38 (2H, t), 8.10 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 3450, 2450, 1700, 1600 Elemental Analysis for C₁₉H₂₃FN₄O₂·HCℓ: Calcd. (%) C 57.79; H 6.13; N 14.19 Found (%) C 57.87; H 6.43; N 13.85 EXAMPLE 59 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-6,7-dihydro-5H-1,2,4-triazolo[3,4-b]-1,3-oxazin-3(2H)-one In the manner described in Example 52, the entitled compound was obtained as an oily substance from 2-(2-chloroethyl)-6,7-dihydro-5H-1,2,4-triazolo[3,4-b]-1,3-oxazin-3(2H)-one and 4-(4-fluorobenzoyl)piperidine. NMR Spectrum (CDCℓ₃) δ: 1.7-2.4 (8H, m), 2.72 (2H, t), 3.0-3.2 (3H, m), 3.72 (2H, t), 3.84 (2H, t), 4.36 (2H, t), 7.13 (2H, t), 7.96 (2H, dd) EXAMPLE 60 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one In the manner described in Example 52, the entitled compound was obtained as colorless crystals from 2-(2-chloroethyl)-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-b]-1,4- oxazin-3-one and 4-(4-fluorobenzoyl)piperidine. Melting Point: 127-129°C NMR Spectrum (CDCℓ₃) δ: 1.7-1.9 (4H, m), 2.0-2.4 (2H, m), 2.74 (2H, t), 2.9-3.2 (3H, m), 3.69 (2H, t), 3.85-4.07 (4H, m), 4.64 (2H, s), 7.13 (2H, t), 7.96 (2H, dd) EXAMPLE 61 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one Hydrochloride Hemihydrate In 50 mℓ of ethanol was dissolved 1.64 g of 2-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-2,5,6,8-tetrahydro-3H-1,2,4-triazolo[3,4-c]-1,4-oxazin-3-one obtained in Example 60, and 0.5 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure. The residue was crystallized from ethanol to obtain 1.37 g of the entitled compound as colorless crystals. Melting Point: 236-239°C NMR Spectrum (DMSO-d₆) δ: 1.8-2.2 (4H, m), 3.0-3.9 (9H, m), 3.98 (2H, t), 4.17 (2H, t), 4.63 (2H, s), 7.38 (2H, t), 8.10 (2H, dd), 11.0 (1H, bs) IR Spectrum ν (KBr) cm⁻¹: 3450, 2520, 1690, 1600, 1490, 1440, 1420 Elemental Analysis for C₁₉H₂₃FN₄O₃·HCℓ·1/2H₂O: Calcd. (%) C 54.35; H 6.00; N 13.34 Found (%) C 54.46; H 6.25; N 13.18 EXAMPLE 62 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In the manner described in Example 52, the entitled compound was obtained as pale yellow crystals from 2-(2-chloroethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one and 4-(4-fluorobenzoyl)-4-hydroxypiperidine. Melting Point: 165-167°C NMR Spectrum (CDCℓ₃) δ: 1.58-2.07 (4H, m), 2.07-3.0 (12H, m), 3.58 (2H, m), 3.80 (1H, s), 3.92 (2H, t), 7.11 (2H, t), 8.07-8.30 (2H, m) IR Spectrum ν (KBr) cm⁻¹: 1665, 1590, 1490 EXAMPLE 63 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride In 50 mℓ of ethanol was dissolved 2.2 g of 2-[2-[4-(4-fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 62, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was recrystallized from a mixture of ethanol and ethyl ether to obtain 1.8 g of the entitled compound as colorless crystals. Melting Point: 202-204°C NMR Spectrum (DMSO-d₆) δ: 1.55-2.0 (4H, m), 2.0-2.4 (4H, m), 2.55 (2H, m), 2.9-3.7 (8H, m), 4.12 (2H, t), 7.35 (2H, t), 8.29 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 1715, 1685, 1600, 1500, 1440, 1260, 1240, 1150 Elemental Analysis for C₂₀H₂₅FN₄O₃·HCℓ: Calcd. (%) C 56.53; H 5.93; N 13.19 Found (%) C 56.26; H 6.33; N 13.47 EXAMPLE 64 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one In the manner described in Example 52, the entitled compound was obtained as pale yellow crystals from 2-(2-chloroethyl)-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one and 4-(4-fluorobenzoyl)-4-hydroxypiperidine. Melting Point: 156-158°C NMR Spectrum (CDCℓ₃) δ: 1.55-2.05 (4H, m), 2.07-3.0 (12H, m), 3.78 (2H, m), 3.90 (1H, s), 3.92 (2H, t), 7.12 (2H, t), 8.1-8.32 (2H, m) IR Spectrum ν (KBr) cm⁻¹: 1680, 1595 EXAMPLE 65 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one Hydrochloride In 50 mℓ of ethanol was dissolved 2.6 g of 2-[2-[4-(4-fluorobenzoyl)-4-hydroxypiperidin-1-yl]ethyl]-2,5,6,7,8,9-hexahydro-3H-1,2,4-triazolo[4,3-a]azepin-3-one obtained in Example 64, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from ethyl ether, followed by recrystallization from a mixture of ethanol and ethyl ether to give 2.2 g of the entitled compound as colorless crystals. Melting Point: 195-197°C NMR Spectrum (DMSO-d₆) δ: 1.70 (6H, bs), 1.8-2.4 (4H, m), 2.60 (2H, m), 3.0-3.8 (8H, m), 4.10 (2H, t), 7.33 (2H, t), 8.28 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 1705, 1605, 1515, 1490, 1445, 1420, 1220, 1165 Elemental Analysis for C₂₁H₂₇FN₄O₃·HCℓ: Calcd. (%) C 57.46; H 6.43; N 12.76 Found (%) C 57.24; H 6.56; N 12.50 EXAMPLE 66 Synthesis of 2-[2-[trans-3-(4-Fluorophenyl)-4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In the manner described in Example 52, the entitled compound was obtained as an oily substance from 2-(2-chloroethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one and trans-3-(4-fluorophenyl)-4-(4-fluorobenzoyl)piperidine. 500 MHz-NMR Spectrum (CDCℓ₃) δ: 1.77-1.88 (3H, m), 1.89-2.0 (3H, m), 2.28 (1H, t), 2.3 (1H, t), 2.67 (2H, t), 2.79 (2H, t), 3.08 (1H, dd), 3.15 (1H, bd), 3.35 (1H, dt), 3.55 (1H, dt), 3.61 (2H, dt), 3.91 (2H, dt), 6.86 (2H, t), 7.04 (2H, t), 7.16 (2H, m), 7.81 (2H, m) EXAMPLE 67 Synthesis of 2-[2-[trans-3-(4-Fluorophenyl)-4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-3H-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Maleate In 50 mℓ of ethanol was dissolved 0.65 g of 2-[2-[trans-3-(4-fluorophenyl)-4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 66, and 0.16 g of maleic acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from water to obtain 0.45 g of the entitled compound as pale yellow crystals. Melting Point: 90-95°C NMR Spectrum (DMSO-d₆) δ: 1.5-1.95 (4H, bs), 2.10 (2H, m), 2.60 (2H, m), 2.8-3.75 (9H, m), 4.03 (2H, t-like), 4.23 (1H, m), 6.11 (2H, s), 6.92 (6H, m), 7.85-8.14 (2H, m) IR Spectrum ν (KBr) cm⁻¹: 1700, 1600, 1515, 1360, 1225 Elemental Analysis for C₂₆H₂₈F₂N₄O₂·C₄H₄O₄: Calcd. (%) C 61.85; H 5.54; N 9.62 Found (%) C 61.50; H 5.40; N 9.58 EXAMPLE 68 Synthesis of 2-[2-[4-(2,4-Difluorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In the manner described in Example 52, the entitled compound was obtained as colorless crystals from 2-(2-chloroethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]-pyridin-3(2H)-one and 4-(2,4-difluorobenzoyl)piperidine. NMR Spectrum (CDCℓ₃) δ: 1.47-2.42 (10H, m), 2.50-3.26 (7H, m), 3.6 (2H, t), 3.9 (2H, t), 6.67-7.09 (2H, m), 7.68-8.04 (1H, m) The above crystals were dissolved in ethanol, and concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from a mixture of acetone and isopropyl ether, followed by recrystallization from a mixture of ethanol and isopropyl ether to yield the hydrochloride hemihydrate of the entitled compound as colorless crystals. Melting Point: 89°C (decomposition) NMR Spectrum (DMSO-d₆) δ: 1.56-2.24 (10H, m), 2.44-3.88 (9H, m), 4.10 (2H, t), 7.15-7.60 (2H, m), 7.78-8.09 (1H, m) IR Spectrum ν (KBr) cm⁻¹: 3440, 2950, 2530, 1695, 1610, 1495 Elemental Analysis for C₂₀H₂₄F₂N₄O₂·HCℓ·1/2H₂O: Calcd. (%) C 55.11; H 6.01; N 12.85 Found (%) C 55.67; H 6.38; N 12.57 EXAMPLE 69 Synthesis of 2-[2-[4-(4-Fluoro-2-morpholinobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In the manner described in Example 48, the entitled compound was obtained as a pale yellow oily substance from 2-[2-(4-methylbenzenesulfonyloxy)ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one and 4-(4-fluoro-2-morpholinobenzoyl)piperidine. NMR Spectrum (CDCl₃) δ: 1.48-2.30 (11H, m), 2.63-2.79 (4H, m), 2.91-3.01 (6H, m), 3.22-3.94 (6H, m), 3.60 (2H, t), 6.66-6.86 (2H, m), 7.26 (1H, dd) EXAMPLE 70 Synthesis of 2-[2-[4-(4-Fluoro-2-morpholinobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride Hemihydrate In 50 mℓ of methanol was dissolved 0.9 g of 2-[2-[4-(4-fluoro-2-morpholinobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 69, and 1 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the resulting crystal was recrystallized from a mixture of methanol and isopropyl ether to obtain 0.53 g of the entitled compound as colorless crystals. Melting Point: 159-160°C NMR Spectrum (DMSO-d₆) δ: 1.56-2.10 (11H, m), 2.77-3.04 (4H, m), 3.22-3.89 (12H, m), 4.09 (2H, t), 6.77-7.14 (2H, m), 7.24-7.46 (1H, m) IR Spectrum ν (KBr) cm⁻¹: 3450, 2990, 1705, 1620 Elemental Analysis for C₂₄H₃₂FN₅O₃·2HCℓ·H₂O: Calcd. (%) C 52.55; H 6.61; N 12.76 Found (%) C 52.30, H 6.70; N 12.61 EXAMPLE 71 Synthesis of 2-[2-[4-(2-Fluoro-4-morpholinobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In the manner described in Example 48, the entitled compound was obtained as pale yellow crystals from 2-[2-[(4-methylbenzenesulfonyloxy)ethyl]-5,6,7,8-tetrahydro-1,2,4- triazolo[4,3-a]pyridin-3(2H)-one and 4-(2-fluoro-4-morpholinobenzoyl)piperidine. NMR Spectrum (CDCℓ₃) δ: 1.48-2.38 (11H, m), 2.62-2.81 (4H, m), 2.94-3.13 (2H, m), 3.23-3.37 (4H, m), 3.60 (2H, t), 3.78-3.97 (6H, m), 6.36-6.72 (2H, m), 7.78 (1H, dd) The above crystals were dissolved in methanol, and concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from a mixture of methanol and isopropyl ether, followed by recrystallization from a mixture of methanol and isopropyl ether to give the hydrochloride of the entitled compound as colorless crystals. Melting Point: 242-245°C NMR Spectrum (DMSO-d₆) δ: 1.56-2.10 (11H, m), 2.83-3.88 (16H, m), 4.10 (2H, t), 6.63-7.02 (2H, m), 7.60-7.87 (1H, m) IR Spectrum ν (KBr) cm⁻¹: 3450, 2950, 2850, 2320, 1695, 1655, 1615 Elemental Analysis for C₂₄H₃₂FN₅O₃·HCℓ: Calcd. (%) C 58.35; H 6.73; N 14.17 Found (%) C 58.17; H 6.90; N 14.10 EXAMPLE 72 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)-4-phenylpiperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In the manner described in Example 52, the entitled compound was obtained as a colorless oily substance from 2-(2-chloroethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin3(2H)-one and 4-(4-fluorobenzoyl)-4-phenylpiperidine. NMR Spectrum (CDCℓ₃) δ: 1.8-2.9 (16H, m), 3.59 (2H, t-like), 3.85 (2H, t), 6.89 (2H, t), 7.3-7.5 (7H, m) EXAMPLE 73 Synthesis of 2-[2-[4-(4-Fluorobenzoyl)-4-phenylpiperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride Hydrate In 50 mℓ of methanol was dissolved 1.28 g of 2-[2-[4-(4-fluorobenzoyl)-4-phenylpiperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 72, and 0.3 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from a mixture of ethanol and ethyl ether and then recrystallized from a mixture of ethanol and isopropyl ether to obtain 0.87 g of the entitled compound as colorless crystals. Melting Point: 139-142°C NMR Spectrum (DMSO-d₆) δ: 1.6-2.0 (4H, m), 2.3-3.7 (14H, m), 4.1 (2H, t), 7.0-7.7 (9H, m), 11.1 (1H, bs) IR Spectrum ν (KBr) cm⁻¹: 3420, 1700, 1590, 1500, 1450, 1220 Elemental Analysis for C₂₆H₂₉FN₄O₂.HCℓ.H₂O: Calcd. (%) C 62.08; H 6.41; N 11.14 Found (%) C 62.25; H 6.80; N 10.82 EXAMPLE 74 Synthesis of 2-[2-[4-(4-Chlorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one In the manner described in Example 52, the entitled compound was obtained as a colorless oily substance from 2-(2-chloroethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one and 4-(4-chlorobenzoyl)piperidine. NMR Spectrum (CDCℓ₃) δ: 1.7-2.5 (10H, m), 2.5-2.8 (4H, m), 2.9-3.4 (3H, m), 3.5-3.7 (2H, m), 3.90 (2H, t), 7.48 (2H, d), 7.92 (2H, d) EXAMPLE 75 Synthesis of 2-[2-[4-(4-Chlorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one Hydrochloride In 100 mℓ of ethanol was dissolved 3.7 g of 2-[2-[4-(4-chlorobenzoyl)piperidin-1-yl]ethyl]-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one obtained in Example 74, and 2 mℓ of concentrated hydrochloric acid was added thereto. The mixture was concentrated to dryness under reduced pressure, and the residue was crystallized from a mixture of ethanol and ethyl ether to obtain 3.2 g of the entitled compound as colorless crystals. Melting Point: 245-248°C NMR Spectrum (DMSO-d₆) δ: 1.7-2.2 (8H, m), 2.5-2.7 (4H, m), 3.2-3.8 (7H, m), 4.0-4.3 (2H, m), 7.65 (2H, d), 8.15 (2H, d) IR Spectrum ν (KBr) cm⁻¹: 1707, 1683, 1584, 1410 Elemental Analysis for C₂₀H₂₅CℓN₄O₂·HCℓ: Calcd. (%) C 56.47; H 6.16; N 13.17 Found (%) C 56.58; H 6.02; N 12.87 REFERENCE EXAMPLE 14 Synthesis of 6,7,8,9-Tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione To a solution of 1.52 g of 2-amino-3,4,5,6-tetrahydropyridine in 30 ml of acetonitrile, 3.86 g of diphenyl imidodicarboxylate was added. After refluxing for 2 hours, the mixture was concentrated to dryness. The residue was purified by column chromatography (silica gel, eluent: methanolchloroform) to give 1.97 g of the entitled compound as colorless crystals. Melting point: 185-187°C NMR Spectrum (DMSO-d₆) δ: 1.6-1.9 (4H, m), 2.65 (2H, t), 3.64 (2H, t), 11.39 (1H, b) IR Spectrum ν (KBr) cm⁻¹: 3450, 3200, 3070, 1700, 1590, 1490, 1440, 1390 Elemental Analysis for C₇H₉N₃O₂: Calcd. (%) C 50.30; H 5.43; N 25.14 Found (%) C 50.42; H 5.53; N 25.02 Compounds in REFERENCE EXAMPLES of 15 to 19 were prepared in the same manner described in Reference Example 14 (shown in Table 1). REFERENCE EXAMPLE 20 Synthesis of 3-Phenoxycarbonyl-2-oxazolidone To an ice-cooled solution of 5.0 g of 2-oxazolidone and 9.08 g of phenyl chloroformate in 50 ml of dichloromethane, 6.07 g of triethylamine was added dropwise with stirring. After stirring for 20 minutes, water was added to the solution, and an organic layer separated was concentrated to dryness under reduced pressure. The residue was crystallized from hexane to give 9.89 g of the entitled compound as colorless crystals. Melting point: 157-160°C NMR Spectrum (DMSO-d₆) δ: 4.0-4.2 (2H, m), 4.3-4.5 (2H, m), 7.2-7.6 (5H, m) IR Spectrum ν (KBr) cm⁻¹: 3520, 3200-2800, 1730, 1670, 1600, 1480, 1420 Elemental Analysis for C₁₀H₉NO₄: Calcd. (%) C 57.97; H 4.38; N 6.76 Found (%) C 57.78; H 4.36; N 6.78 REFERENCE EXAMPLE 21 Synthesis of 5-Methyl-3-phenoxycarbonyl-2-oxazolidone The entitled compound was prepared as colorless crystals from 5-methyl-2-oxazolidone and phenyl chloroformate in the manner described in Reference Example 20. Melting point: 116-119°C NMR Spectrum (CDCl₃) δ: 1.53 (3H, d), 4.0 (1H, m), 4.50 (2H, m), 7.1-7.5 (5H, m) IR Spectrum ν (KBr) cm⁻¹: 3448,1812, 1728, 1592, 1484 Elemental Analysis for C₁₁H₁₁NO₄: Calcd. (%) C 59.72; H 5.01; N 6.33 Found (%) C 59.56; H 5.08; N 6.52 REFERENCE EXAMPLE 22 Synthesis of 3-Phenoxycarbonyl-3,4,5,6-tetrahydro-2H-1,3-oxazin-2-one A mixture of 23.8 g of bis(tri-n-butyltin)oxide and 4.8 g of 3-chloropropylisocyanate was stirred for 10 minutes at room temperature, and 15.0 g of hexamethylsulforoamide (HMPA) was added thereto. The mixture was stirred for 1 hour at 80°C and cooled. To the mixture, 6.26 g of phenyl chloroformate was added dropwise over 5 minutes, and the mixture was stirred for 30 minutes at room temperature. After cooling, 80 ml of hexane was added to the mixture, and the resultant precipitates were collected by filtration to give 7.79 g of the entitled compound as colorless crystals. Melting point: 94-96°C NMR Spectrum (CDCl₃) δ: 2.19 (2H, m), 3.91 (2H, t), 4.38 (2H, t), 7.1-7.5 (5H, m) IR Spectrum ν (KBr) cm⁻¹: 2924, 1808, 1788, 1696, 1480 Elemental Analysis for C₁₁H₁₁NO₄: Calcd. (%) C 59.72; H 5.01; N 6.33 Found (%) C 59.44; H 5.09; N 6.56 REFERENCE EXAMPLE 23 Synthesis of 3-(2-Chloroethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione A solution of 2.79 g of diethyl azodicarboxylate in 5 ml of tetrahydrofuran was added dropwise to a solution of 2.0 g of 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine2,4(3H)-dione prepared in Reference Example 14, 1.13 g of 2-chloroethanol and 4.2 g of triphenylphosphine in 40 ml of tetrahydrofuran. After stirring for 1 hours, the reaction mixture was concentrated to dryness. The residue was purified by column chromatography (silica gel, eluent: methanolchloroform) to give an oil, which was crystallized form a mixture of acetone and isopropyl ether to give 1.2 g of the entitled compound as colorless crystals. Melting point: 61-63°C NMR Spectrum (CDCl₃) δ: 1.8-2.2 (4H, m), 2.83 (2H, t), 3.77 (2H, t), 3.85 (2H, t), 4.28 (1H, t) IR Spectrum ν (KBr) cm⁻¹: 3390, 2976, 1730, 1678, 1594, 1484 Elemental Analysis for C₉H₁₂ClN₃O₂: Calcd. (%) C 47,07; H 5.26; N 18.30 Found (%) C 47.35; H 5.49; N 18.21 REFERENCE EXAMPLE 24 Synthesis of 3-(2-Bromoethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione The entitled compound was prepared as colorless crystals from 6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione and 2-bromoethanol in the manner described in Reference Example 23. Melting point: 64-66°C NMR Spectrum (CDCl₃) δ: 1.8-2.1 (4H, m), 2.84 (2H, t-like), 3.59 (2H, t), 3.86 (2H, t-like), 4.33 (1H, t) IR Spectrum ν (KBr) cm⁻¹: 3396, 2976, 1730, 1678, 1594, 1484 Elemental Analysis for C₉H₁₂BrN₃O₂: Calcd. (%) C 39.44; H 4.41; N 15.33 Found (%) C 39.66; H 4.48; N 15.25 REFERENCE EXAMPLE 25 Synthesis of 3-(2-Bromoethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione (1) Phenyl N-(2-Bromoethyl)carbamate To an ice-cooled suspension of 5.0 g of 2-bromoethylamine hydrobromide and 3.91 g of phenyl chloroformate in 50 ml of dichloromethane, 5.1 g of triethylamine was added. The mixture was stirred for 2 hours, and water was added thereto. The organic phase separated was concentrated to dryness under reduced pressure. The residue was crystallized with hexane to give 5.33 g of the entitled compound as colorless crystals. Melting point: 57-60°C NMR (CDCl₃) δ: 3.4 (4H, m), 5.6 (1H, b), 7.0-7.5 (5H, m) (2) 3-(2-Bromoethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione To an ice-cooled suspension of 2.44 g of phenyl N-(2-bromoethyl)carbamate and 1.64 g of phenyl chloroformate in 25 ml of acetonitrile, 1.2 g of triethylamine was added dropwise. After stirring for 20 minutes at the same temperature, the mixture was stirred for 3 hours at room temperature. The reaction mixture was concentrated to dryness under reduced pressure, and the residue was extracted with chloroform. After concentration of the chloroform solution, the residue was dissolved in 20 ml of acetonitrile, and a mixture of 1.35 g of 2-amino-3,4,5,6-tetrahydropyridine hydrochloride and 2.02 g of triethylamine was added to the solution. After stirring for 45 minutes at 60°C, the mixture was concentrated and extracted with chloroform. The solvent was evaporated, and the residue was purified by column chromatography (silica gel, eluent: methanol-chloroform). After concentration of the eluate, the residue was crystallized from a mixture of acetone and isopropyl ether to give 0.65 g of the entitled compound as colorless crystals. Melting point: 64-66°C NMR Spectrum (CDCl₃) δ: 1.8-2.1 (4H, m), 2.84 (2H, t-like), 3.59 (2H, t), 3.86 (2H, t-like), 4.33 (2H, t) REFERENCE EXAMPLE 26 Synthesis of 3-(2-Bromoethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione To a mixture of 2.57 g of diphenyl imidodicarboxylate, 1.50 g of 2-bromoethanol and 3.41 g of triphenylphosphine in 30 ml of tetrahydrofuran, 2.26 g of diethyl azodicarboxylate was added dropwise with stirring. After stirring for 2 hours, 0.98 g of 2-amino-3,4,5,6-tetrahydropyridine was added, and the mixture was stirred for 2 hours at room temperature. The reaction mixture was concentrated to dryness under reduced pressure, and the residue was purified by column chromatography (silica gel, eluent: ethyl acetate). After concentration of the eluate, the residue was crystallized from a mixture of acetone and isopropyl ether to give the entitled compound as colorless crystals. Melting point: 64-66°C NMR Spectrum (CDCl₃) δ: 1.8-2.1 (4H, m), 2.84 (2H, t-like), 3.59 (2H, t), 3.86 (2H, t-like), 4.33 (1H, t) IR Spectrum ν (KBr) cm⁻¹: 3396, 2976, 1730, 1678, 1594, 1484 Elemental Analysis for C₉H₁₂BrN₃O₂: Calcd. (%) C 39.44; H 4.41; N 15.33 Found (%) C 39.58; H 4.62; N 15.13 REFERENCE EXAMPLE 27 Synthesis of 3-(2-Hydroxyethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione To an ice-cooled solution prepared from 0.46 g of sodium and 20 ml of anhydrous ethanol, 2.69 g of 2-amino-3,4,5,6-tetrahydro pyridine hydrochloride was added. After stirring for 40 minutes at room temperature, the insoluble material was filtered off, and the filtrate was concentrated to dryness. The residue was dissolved in 30 ml of acetonitrile, and 4.14 g of 3-phenoxycarbonyl-2-oxazolidone was added thereto. The mixture was stirred for 1.5 hours at 60°C. After concentration of the reaction mixture, the residue was purified by column chromatography (silica gel, eluent: methanol-chloroform) to give 3.45 g of the entitled compound as colorless crystals. Melting point: 125-128°C NMR Spectrum (DMSO-d₆) δ: 1.8-2.1 (4H, m), 2.69 (1H, s), 2.82 (2H, t), 3.86 (4H, t-like), 4.14 (2H, t) IR Spectrum ν (KBr) cm⁻¹: 3293, 2960, 1730, 1684, 1602, 1504, 1452, 1416 Elemental Analysis for C₉H₁₃N₃O₃: Calcd. (%) C 51.18; H 6.20; N 19.89 Found (%) C 50.83; H 6.43; N 19.64 Compounds in Reference Example 28 to 31 were prepared in the same manner described in Reference Example 27 (shown in Table 2). REFERENCE EXAMPLE 32 Synthesis of 3-(1-Hydroxypropan-2-yl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione. The entitled compound was prepared as colorless crystals from 5-methyl-3-phenoxycarbonyl-2-oxazolidone prepared in Reference Example 21 and 2-amino-3,4,5,6-tetrahydropyridine hydrochloride in the same manner described in Reference Example 27. Melting point: 109-112°C NMR Spectrum (DMSO-d₆) δ: 1.4 (3H, d), 1.7-2.1 (4H, m), 2.80 (2H, t), 3.34 (1H, s), 3.6-3.9 (3H, m), 4.09 (1H, dd), 5.02 (1H, m) IR Spectrum ν (KBr) cm⁻¹: 3300, 2948, 2884, 1680, 1606, 1490 Elemental Analysis for C₁₀H₁₅N₃O₃: Calcd. (%) C 53.32; H 6.71; N 18.65 Found (%) C 53.26; H 6.89; N 18.82 REFERENCE EXAMPLE 33 Synthesis of 3-(2-Methanesulfonyloxyethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione To an ice-cooled solution of 1.80 g of 3-(2-hydroxyethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in Reference Example 27 and 1.20 g of triethylamine in 25 ml of acetonitrile, 1.17 g of methanesufonyl chloride was added dropwise. After stirring for 30 minutes, the mixture was concentrated to dryness, and the residue was extracted with chloroform. Concentration of the chloroform solution gave 2,34 g of the entitled compound as an yellow oil. NMR Spectrum (CDCl₃) δ: 1.8-2.1 (4H, m), 2.8 (2H, t), 3.1 (3H, s), 3.9 (2H, t), 4.3 (2H, t), 4.5 (2H, t) REFERENCE EXAMPLE 34 Synthesis of 3-[2-(4-Methylbenzenesulfonyloxy)ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione The entitled compound was prepared as a yellowish solid from 3-(2-hydroxyethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in Reference Example 27 and 4-methylbenzenesulfonyl chloride in the manner described in Reference Example 33. NMR Spectrum (CDCl₃) δ: 1.8-2.1 (4H, m), 2.44 (3H, s), 2.81 (2H, t-like), 3.83 (3H, t-like), 4.3 (4H, m), 7.32 (2H, d), 7.77 (2H, dd) EXAMPLE 76 Synthesis of 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl)ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione A solution of 3.3 g of 3-(2-methanesulfonyloxyethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in Reference Example 33, 1.01 g of triethylamine and 2,27 g of 4-(4-fluorobenzoyl)piperidine in 25 ml of acetonitrile was refluxed for 4 hours. After concentration of the reaction mixture, the residue was extracted with chloroform. The chloroform solution was concentrated to dryness, and the residue was purified by column chromatography (silica gel, eluent: methanol-chloroform) to give 2.17 g of the entitled compound as yellow crystals. Melting point: 170-172°C NMR Spectrum (CDCl₃) δ: 1.8-2.2 (10H, m), 2.26 (2H, t), 2.81 (2H, t), 3.0-3.3 (3H, m), 3.84 (2H, t), 4.06 (2H, t), 7.13 (2H, t), 7.95 (2H, dd) IR Spectrum ν (KBr) cm⁻¹: 1730, 1670, 1600, 1490, 1450, 1410 Elemental Analysis for C₂₁H₂₅FN₄O₃: Calcd. (%) C 62.99; H 6.29; N 13.99 Found (%) C 62.76; H 6.32; N 14.05 EXAMPLE 77 Synthesis of 3-[2-[4-[Bis(4-fluorophenyl)methylene]piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione The entitled compound was prepared as a yellowish oil from 3-(2-methanesulfonyloxyethyl)-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione prepared in Reference Example 33 and 4-[bis(4-fluorophenyl)methylene]piperidine in the manner described in Example 76. NMR Spectrum (CDCl₃) δ: 1.8-2.0 (4H, m), 2.3 (4H, m), 2.5-2.8 (8H, m), 3.8 (2H, t), 4.07 (2H, t), 6.96 (4H, d), 7.04 (4H, s) TEST EXAMPLE 1 Antagonistic Activity on Serotonin 2-Receptor A test compound dissolved in purified water was orally administered to an SD-SLC male rat at a dose of 10 mg/kg. After 30 minutes from the administration, the rat was anesthetized with urethane (1 g/kg, i.p.) and α-Chloralose (80 mg/kg, i.p.). A polyethylene cannula was inserted into the carotid artery, and the blood pressure was recorded on a polygraph by using a pressure transducer. After 60 minutes or 180 minutes from the administration of the test compound, 300 µg/kg of serotonin was intravenously injected, and an increase in blood pressure was observed. Serotonin 2 (hereinafter referred to as 5-HT₂) antagonistic activity of the test compound was calculated as a percentage of inhibition of an increase in blood pressure induced by 5-HT₂. The inhibitory effect of the test compound was compared with that of vehicle solution treated group. The results obtained are shown in Table 3 below. TEST EXAMPLE 2 Antagonistic Activity on Sympathetic Nerve α₁-Receptor A test compound dissolved in purified water was orally administered to an SD-SLC male rat at a dose of 10 mg/kg. After 30 minutes from the administration, the rat was anesthetized with urethane (1 g/kg, i.p.) and α-Chloralose (80 mg/kg, i.p.). A polyethylene cannula was inserted into the carotid artery, and the blood pressure was recorded on a polygraph by using a pressure transducer. After 60 minutes from the administration of the test compound, 100 µg/kg of phenylephrine was intravenously injected to observe an increase in blood pressure. Sympathetic nerve α₁-receptor antagonistic activity of the test compound was calculated as a percentage of inhibition of an increase in blood pressure induced by phenylephrine. The inhibitory effect of the test compound was compared with that of vehicle solution treated group. The results obtained are shown in Table 3. TEST EXAMPLE 3 Toxicity in Mice A test compound dissolved or suspended in a 1% methyl cellulose solution was orally administered to ddy male mice (4 or 5 mice per group) at a dose of 200 mg/kg once a day for consecutive 4 days. The number of dead animals per group was counted on the day next to the final administration day. As a control, 10 mℓ/kg of a 1% methyl cellulose solution was orally administered. The results obtained are shown in Table 3. Test Compound Antagonistic Activity Toxicity (Death Rate) 5-HT₂ (%) α₁ (%) Compound of Example 2 93 9 1/5 Compound of Example 3 93 39 0/5 Compound of Example 11 83 0 Compound of Example 18 93 6 0/5 Compound of Example 20 83 1 Compound of Example 21 93 3 Compound of Example 34 90 3 1/4 Compound of Example 36 84 3 0/5 Compound of Example 44 89 2 2/5 Compound of Example 49 82 3 0/5 Compound of Example 51 95 3 0/5 Compound of Example 63 85 0 Compound of Example 67 90 4 Compound of Example 75 83 17 0/3 Ketanserin 96 73 5/5 Ritanserin 84 5 3/5 TEST EXAMPLE 4 Binding Activity to Serotonin 2-Receptor A male SD rat was decapitated under anesthesia, and the frontal cortex was removed to obtain a membrane preparation. ³H-Ketanserin and Methysergide were used as a labelled ligand and a non-specific binding reagent, respectively. These reagents and a test compound thereof were dissolved in a 5% methanol tris-buffer solution. After incubation, this solution was filtered by suction through a GF/B glass filter. Radioactivity of ³H-Ketanserin collected on the filter was measured with a liquid scintillation counter. A Scatchard plot was prepared from the resulting radioactivity values, and a dissociation constant of serotonin 2-receptor and a receptor density of the membrane preparation were obtained. Further, from the receptor-binding inhibition curve of the compound is obtained a 50% inhibitory concentration, and a dissociation constant indicative of the binding affinity to serotonin 2-receptor was calculated. As a result, the dissociation constant of a hydrochloride of 3-[2-[4-(fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione (hereinafter referred to as compound A) was found to have a dissociation constant of 15 nM for serotonin 2-receptor. TEST EXAMPLE 5 Effect in Acute Cardiac Infarction Model Experimental Preparation: Mongrel dogs (body weight: 8 to 20 kg) under anesthesia were ventilated artificially and underwent a left thracotomy. A needle type platinum electrode was placed in the myocardium nourished by the left anterior descending coronary artery (hereinafter referred to as LDA) to a depth of about 1 cm, and the blood flow in the myocardial tissue was determined by a hydrogen gas clearance method. A polyethylene cannula was inserted into the femoral artery, and the blood pressure and heart rate were recorded. A cannula was inserted into the femoral artery for administration of a drug and also into the carotid artery from which a blood sample was to be taken. After stabilization period of the test preparation, LDA was ligated with a clamp. After 2 hours from the ligature, the clamp was released for reperfusion. After observation for the following 4 hours, the heart was excised. A 1% triphenyltetrazolium chloride solution was infused from the left coronary anterior descending branch, while retrogressively infusing a 0.5% Evans' Blue solution from the aorta, each at a pressure of about 80 mmHg, and they were perfused through the heart for 15 minutes for double staining. Then, the heart was washed and sliced at 1 cm intervals from the apex in the direction vertical to the longer axis. Each slice at the left ventricle was divided into a part which was in risk of cardiac infarction indicated by Evans' Blue stain (hereinafter referred to as risk area) and a normal area, and each area was weighed. The weight of the left ventricle (the sum of the risk area and the normal area) and that of the risk area of each slice were individually added up to obtain the weight of the whole left ventricle and the total weight of the risk area. Further, of each slice, the area of the risk area which was not stained with Evans' Blue and that of a cardiac infarction area within the risk area which remained white, i.e., which was stained neither in blue with Evans' Blue nor in red with triphenyltetrazolium chloride, were measured to obtain a ratio of cardiac infarction part to the whole left ventricle (infarction size). Administration of Drug: A hydrochloride of compound A or physiological saline was infused by an intravenous drip at a rate of 1 mℓ/kg/hr from 20 minutes before the ligature of the left coronary anterior descending branch through the end of the experiment. The dose of Compound A hydrochloride was 1 mg/kg/hr. The experiment was conducted for the following groups. 1) Control Group (11 cases): treated with saline 2) Test Group (12 cases): treated with hydrochloride of compound A Test Result: The results obtained are shown in Table 4. Control Group Test Group Myocardial Blood Flow (mℓ/min/100 g) 62 ± 9 89 ± 14 Infarction Size: Left Ventricle Weight (g) 68 ± 5 65 ± 5 Dangerous part Weight (g) 21 ± 3 19 ± 2 Infarction Size (%) 30 ± 7 11 ± 3* Blood Pressure (mmHg) 118 ± 4 103 ± 4* Heart Rate (beats/min) 158 ± 8 150 ± 9 Note: The values indicate mean ± S.E.M. As is apparent from the results in Table 4, after the ligature at LDA,reperfusion of blood restored the myocardial blood flow to only 60% of the initial value before the ligature in the control group, whereas in the test group the once deteriorated myocardial blood flow was restored to a level significantly higher than that of the control group. Since there was no substantial difference between the two groups in the left ventricle weight and the risk area weight, the degree of injure given to each heart was considered equal. Under these conditions, compound A significantly reduced the myocardial infarction size. It was thus proved that compound A acts to improve microcirculatory disturbances accompanied by ischemia, preventing the myocardium from necrotizing changes. It was also confirmed that compound A has only a slight influence on blood pressure. Accordingly, compound A was proved useful for prevention and treatment of ischemic heart diseases. TEST EXAMPLE 6 Effect in Angina Pectoris Model Experimental Preparation: Mongrel dogs (body weight: 8 to 20 kg) under anesthesia with pentobarbital (30 mg/kg, i.v.) were ventilated artificially and underwent a left thoracotomy. LDA was separated from connected tissues. A silicone tube for partial occlusion was placed around the LDA, and a probe for blood flow rate measurement was fixed in the neighborhood. The blood flow rate was measured with a pulse Doppler blood flow meter. A cannula was inserted into a branch distal to the occlusion site of the left coronary artery, and the coronary blood pressure was measured. A polyethylene cannula was inserted into the femoral artery, and the systemic blood pressure and heart rate were recorded. A cannula was inserted to the femoral vein for administration of a drug. After stabilization of the preparation, LDA was partially occluded so as to reduce the blood flow rate by 20% to induce an angina pectoris-like condition in which the blood flow rate of LDA is cyclically reduced. Administration of Drug: One hour after the above-described angina pectoris-like condition was presented, a maleate of compound A was administered into the femoral vein at a dose of 0.1 mg/kg. Then, the cyclic coronary flow reduction was disappeared. The effect of the drug was expressed in terms of frequency of the periodic reduction of blood flow rate. The maleate of compound A was used as dissolved in physiological saline. Test Results: The results obtained are shown in Table 5 below. Dose of Compound A Frequency of Periodic Reduction in Blood Flow Rate Before Admin. After Admin. 0.1 mg/kg, i.v. 9.9 ± 2.5 2.3 ± 1.2 Note: Values are means ± S.E.M. It can be seen from Table 3 that compound A, administered at a low dose, significantly reduces the frequency of the cyclic coronary flow reduction as compared with that before administration. Compound A was thus proved effective to suppress anginal attacks. TEST EXAMPLE 7 Toxicity in Rats Toxicity of the maleate of compound A in rats in oral administration for 10 days is shown in Table 6. Dose Number of Test Animals Number of Dead Animals 50 mg/kg (p.o.) 5 0 200 mg/kg (p.o.) 5 0 800 mg/kg (p.o.) 5 0 While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims: Claims for the following Contracting States : AT, BE, CH, DE, DK, FR, GB, IT, LI, LU, NL, SE A heterocyclic compound represented by formula (I) wherein R¹ represents a hydrogen atom, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; ℓ represents 0 or 1; ring A represents a 5- to 7-membered heterocyclic ring which may contain one hetero atom selected from the group consisting of an oxygen atom and a sulfur atom in addition to the nitrogen atom shared with the triazine ring or triazole ring, and which may contain one or more double bonds; Y represents an alkylene group having from 1 to 15 carbon atoms which may be substituted with one or more substituents selected from a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; and Q represents a group represented by formula (II): Wherein R² represents a hydrogen atom, a hydroxyl group, an alkyl group or an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, a hydroxyl group, an alkyl group, an alkoxy group and a trihalogenomethyl group; and R³, R⁴ and R⁵, which may be the same or different, each represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a nitrogen containing 5- to 7-membered alicyclic heterocyclic group which in addition may contain one or more hetero atoms selected from a nitrogen atom, an oxygen atom and a sulfur atom or a trihalogenomethyl group, or a group represented by formula (III): wherein Ar¹ and Ar², which may be the same or different, each represents an aryl group or an aromatic heterocyclic group, selected from pyridyl, pyrimidinyl, thienyl, furyl, pyrazolyl, imidazolyl, thiazolyl oxazolyl, isothiazolyl and isoxazolyl, each of which may be substituted with one to three substituents selected from the group consisting of a halogen atom, a hydroxyl group, an alkoxy group, an alkyl group and a trihalogenomethyl group, whereby in the above meanings the alkyl and alkoxy groups contain 1 to 6 carbon atoms and aryl is phenyl, naphthyl or biphenyl, and salts thereof. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein ℓ is 0. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein ℓ is 1. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein Y is an alkylene group having from 2 to 7 carbon atoms. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein Y is a group of formula: wherein R⁶ represents a hydrogen atom, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; and n and m each represents 0 or an integer of from 1 to 6. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein Q is represented by formula: wherein R⁷ and R⁸, which may be the same or different, each represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxy group, a halogen atom or a trihalogenomethyl group. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein Q is represented by formula: wherein R² represents a hydrogen atom, a hydroxyl group, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of an alkyl group, an alkoxy group, a halogen atom, and a trihalogenomethyl group; and R³, R⁴ and R⁵, which may be the same or different, each represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or an alicyclic heterocyclic group. A heterocyclic compound and salts thereof as claimed in claim 1, wherein ring A is a pyrrolidine, a piperidine, a homopiperidine or a thiazole, Y is an alkylene group having 1 to 6 carbon atoms and Q is a group represented by formula (II') or (III') or wherein R²¹ represents a hydrogen atom or a hydroxyl group; X represents a halogen atom; and X¹ and X², which may be the same or different, each represents a halogen atom. 3-[2-[4-(4-fluorobenzoyl) piperidin-1-yl]ethyl-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione and acid addition salts thereof according to claim 1. The compounds of formula I of anyone of claims 1 - 9 for pharmaceutical use, in particular as serotonin 2-receptor antagonist or for preventing or treating heart diseases. A pharmaceutical composition, in particular for preventing or treating heart diseases, or as a serotonin 2-receptor antagonist, comprising at least one of the compounds of anyone of claims 1 - 9 as active ingredient, optionally together with a pharmaceutical carrier. A process for preparing the pharmaceutical composition of claim 11 which comprises providing at least one compound of anyone of claims 1 - 9 in a form suitable for administration, optionally incorporated into a pharmaceutical carrier. A process for preparing the compounds of formula I of anyone of claims 1 - 9 which comprises the steps of: 1) reacting a compound of formula (VII): wherein R¹, ring A and ℓ are as defined above, with a compound of formula (VIII): HO-Y-Q (VIII) wherein Q and Y are as defined above, in the presence of dehydrating reagents, 2) reacting the above compound of formula (VII) with a compound of formula (IX) or salts thereof: X³-Y-Q (IX) wherein Y and Q are as defined above; and X³ represents a halogen atom, a trifluoromethanesulfonyloxy group, an alkylsulfonyloxy group or an arylsulfonyloxy group which may be substituted with an alkyl group, a halogen atom or an alkoxy group in the aryl group moiety thereof, in the presence of a base, or 3) reacting a compound of formula (XI): wherein R¹, ring A, ℓ and Y are as defined above; and X⁴ represents a halogen atom, a trifluoromethanesulfonyloxy group, an alkylsulfonyloxy group or an arylsulfonyloxy group which may be substituted with an alkyl group, an alkoxy group or a halogen atom in the aryl group moiety thereof with a compound of formula (XII) or salts thereof: H-Q (XII) wherein Q is as defined above, in the presence of a base. Claims for the following Contracting State : ES A process for prearing a heterocyclic compound represented by formula (I) wherein R¹ represents a hydrogen atom, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; ℓ represents 0 or 1; ring A represents a 5- to 7-membered heterocyclic ring which may contain one hetero atom selected from the group consisting of an oxygen atom and a sulfur atom in addition to the nitrogen atom shared with the triazine ring or triazole ring, and which may contain one or more double bonds; Y represents an alkylene group having from 1 to 15 carbon atoms which may be substituted with one or more substituents selected from a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; and Q represents a group represented by formula (II): Wherein R² represents a hydrogen atom, a hydroxyl group, an alkyl group or an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, a hydroxyl group, an alkyl group, an alkoxy group and a trihalogenomethyl group; and R³, R⁴ and R⁵, which may be the same or different, each represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a nitrogen containing 5- to 7-membered alicyclic heterocyclic group which in addition may contain one or more hetero atoms selected from a nitrogen atom, an oxygen atom and a sulfur atom or a trihalogenomethyl group, or a group represented by formula (III): wherein Ar¹ and Ar², which may be the same or different, each represents an aryl group or an aromatic heterocyclic group, selected from pyridyl, pyrimidinyl, thienyl, furyl, pyrazolyl, imidazolyl, thiazolyl, oxazolyl, isothiazolyl and isoxazolyl, each of which may be substituted with one to three substituents selected from the group consisting of a halogen atom, a hydroxyl group, an alkoxy group, an alkyl group and a trihalogenomethyl group, whereby in the above meanings the alkyl and alkoxy groups contain 1 to 6 carbon atoms and aryl is phenyl, naphthyl or biphenyl, and salts thereof, which comprises the steps of: 1) reacting a compound of formula (VII): wherein R¹, ring A and ℓ are as defined above, with a compound of formula (VIII): HO-Y-Q (VIII) wherein Q and Y are as defined above, in the presence of dehydrating reagents, 2) reacting the above compound of formula (VII) with a compound of formula (IX) or salts thereof: X³-Y-Q (IX) wherein Y and Q are as defined above; and X³ represents a halogen atom, a trifluoromethanesulfonyloxy group, an alkylsulfonyloxy group or an arylsulfonyloxy group which may be substituted with an alkyl group, a halogen atom or an alkoxy group in the aryl group moiety thereof, in the presence of a base, or 3) reacting a compound of formula (XI): wherein R¹, ring A, ℓ and Y are as defined above; and X⁴ represents a halogen atom, a trifluoromethanesulfonyloxy group, an alkylsulfonyloxy group or an arylsulfonyloxy group which may be substituted with an alkyl group, an alkoxy group or a halogen atom in the aryl group moiety thereof with a compound of formula (XII) or salts thereof: H-Q (XII) wherein Q is as defined above, in the presence of a base. A process as claimed in claims 1 for preparing a heterocyclic compound and salts thereof, wherein ℓ is 0. A process as claimed in claim 1 for preparing a heterocyclic compound and salts thereof, wherein ℓ is 1. A process as claimed in claim 1 for preparing a heterocyclic compound and salts thereof, wherein Y is an alkylene group having from 2 to 7 carbon atoms. A process as claimed in claim 1 for preparing a hetereocyclic compound and salts thereof, wherein Y is a group of formula: wherein R⁶ represents a hydrogen atom, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; and n and m each represents 0 or an integer of from 1 to 6. A process as claimed in claim 1 for preparing a heterocyclic compound and salts thereof, wherein Q is represented by formula: wherein R⁷ and R⁸, which may be the same or different, each represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxy group, a halogen atom or a trihalogenomethyl group. A process as claimed in claim 1 for preparing a heterocyclic compound and salts thereof, wherein Q is represented by formula: wherein R² represents a hydrogen atom, a hydroxyl group, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of an alkyl group, an alkoxy group, a halogen atom, and a trihalogenomethyl group; and R³, R⁴ and R⁵, which may be the same or different, each represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or an alicyclic heterocyclic group. A process as claimed in claim 1 for preparing a heterocyclic compound and salts thereof, wherein ring A is a pyrrolidine, a piperidine, a homopiperidine or a thiazole, Y is an alkylene group having 1 to 6 carbon atoms and Q is a group represented by formula (II') or (III') or wherein R²¹ represents a hydrogen atom or a hydroxyl group; X represents a halogen atom; and X¹ and X², which may be the same or different, each represents a halogen atom. A process as claimed in claim 1 for preparing 3-[2-[4-(4-fluorobenzoyl) piperidin-1-yl]ethyl-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione and acid addition salts thereof, A process for preparing a pharmaceutical composition, in particular for preventing or treating heart diseases, or as a serotonin 2-receptor antagonist, which comprises providing at least one compound of anyone of claims 1 - 9 in a form suitable for administration, optionally incorporated into a pharmaceutical carrier. Claims for the following Contracting State : GR A heterocyclic compound represented by formula (I) wherein R¹ represents a hydrogen atom, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; ℓ represents 0 or 1; ring A represents a 5- to 7-membered heterocyclic ring which may contain one hetero atom selected from the group consisting of an oxygen atom and a sulfur atom in addition to the nitrogen atom shared with the triazine ring or triazole ring, and which may contain one or more double bonds; Y represents an alkylene group having from 1 to 15 carbon atoms which may be substituted with one or more substituents selected from a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; and Q represents a group represented by formula (II): Wherein R² represents a hydrogen atom, a hydroxyl group, an alkyl group or an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, a hydroxyl group, an alkyl group, an alkoxy group and a trihalogenomethyl group; and R³, R⁴ and R⁵, which may be the same or different, each represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a nitrogen containing 5- to 7-membered alicyclic heterocyclic group which in addition may contain one or more hetero atoms selected from a nitrogen atom, an oxygen atom and a sulfur atom or a trihalogenomethyl group, or a group represented by formula (III): wherein Ar¹ and Ar², which may be the same or different, each represents an aryl group or an aromatic heterocyclic group, selected from pyridyl, pyrimidinyl, thienyl, furyl, pyrazolyl, imidazolyl, thiazolyl, oxazolyl, isothiazolyl and isoxazolyl, each of which may be substituted with one to three substituents selected from the group consisting of a halogen atom, a hydroxyl group, an alkoxy group, an alkyl group and a trihalogenomethyl group, whereby in the above meanings the alkyl and alkoxy groups contain 1 to 6 carbon atoms and aryl is phenyl, naphthyl or biphenyl, and salts thereof. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein ℓ is 0. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein ℓ is 1. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein Y is an alkylene group having from 2 to 7 carbon atoms. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein Y is a group of formula: wherein R⁶ represents a hydrogen atom, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of a halogen atom, an alkoxy group, an alkyl group and a trihalogenomethyl group; and n and m each represents 0 or an integer of from 1 to 6. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein Q is represented by formula: wherein R⁷ and R⁸, which may be the same or different, each represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxy group, a halogen atom or a trihalogenomethyl group. A heterocyclic compound and salts thereof as claimed in Claim 1, wherein Q is represented by formula: wherein R² represents a hydrogen atom, a hydroxyl group, an alkyl group, an aryl group which may be substituted with one or more substituents selected from the group consisting of an alkyl group, an alkoxy group, a halogen atom, and a trihalogenomethyl group; and R³, R⁴ and R⁵, which may be the same or different, each represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or an alicyclic heterocyclic group. A heterocyclic compound and salts thereof as claimed in claim 1, wherein ring A is a pyrrolidine, a piperidine, a homopiperidine or a thiazole, Y is an alkylene group having 1 to 6 carbon atoms and Q is a group represented by formula (II') or (III') or wherein R²¹ represents a hydrogen atom or a hydroxyl group; X represents a halogen atom; and X¹ and X², which may be the same or different, each represents a halogen atom. 3-[2-[4-(4-fluorobenzoyl) piperidin-1-yl]ethyl-6,7,8,9-tetrahydro-2H-pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione and acid addition salts thereof according to claim 1. A process for preparing a pharmaceutical composition, in particular for preventing or treating heart diseases, or as a serotonin, 2-receptor antagonist, which comprises providing at least one compound of anyone of claims 1 - 9 in a form suitable for administration, optionally incorporated into a pharmaceutical carrier. A process for preparing the compounds of formula I of anyone of claims 1 - 9 which comprises the steps of: 1) reacting a compound of formula (VII): wherein R¹, ring A and ℓ are as defined above, with a compound of formula (VIII): HO-Y-Q (VIII) wherein Q and Y are as defined above, in the presence of dehydrating reagents, 2) reacting the above compound of formula (VII) with a compound of formula (IX) or salts thereof: X³-Y-Q (IX) wherein Y and Q are as defined above; and X³ represents a halogen atom, a trifluoromethanesulfonyloxy group, an alkylsulfonyloxy group or an arylsulfonyloxy group which may be substituted with an alkyl group, a halogen atom or an alkoxy group in the aryl group moiety thereof, in the presence of a base, or 3) reacting a compound of formula (XI): wherein R¹, ring A, ℓ and Y are as defined above; and X⁴ represents a halogen atom, a trifluoromethanesulfonyloxy group, an alkylsulfonyloxy group or an arylsulfonyloxy group which may be substituted with an alkyl group, an alkoxy group or a halogen atom in the aryl group moiety thereof with a compound of formula (XII) or salts thereof: H-Q (XII) wherein Q is as defined above, in the presence of a base.

Inventors: MORISHIMA YOSHIYUKI C O RESEAR, SHIBANO TOSHIRO C O RESEARCH I, TANAKA TSUYOSHI C O RESEARCH I, USUI HIROYUKI C O RESEARCH INS, WATANABE YOSHIFUMI C O RESEARC, YASUOKA MEGUMI C O RESEARCH IN, MORISHIMA, YOSHIYUKI C/O RESEARCH INSTITUTE, SHIBANO, TOSHIRO C/O RESEARCH INSTITUTE, TANAKA, TSUYOSHI C/O RESEARCH INSTITUTE, USUI, HIROYUKI C/O RESEARCH INSTITUTE, WATANABE, YOSHIFUMI C/O RESEARCH INSTITUTE, YASUOKA, MEGUMI C/O RESEARCH INSTITUTE
Applicants: DAIICHI SEIYAKU CO, DAIICHI PHARMACEUTICAL CO., LTD.
Application year: 1990
Main classification: C07D471
IPC codes: C07D487, C07D498, C07D513, C07D471