PROCESS FOR PREPARING IMIDAZOLE DERIVATIVES

Abstract: A process for preparing a novel imiddazole derivative expressed by the general formula: where R¹ and R⁴ represent lower alkyl groups, and R² and R³ lower alkylene groups. The process proceeds as follows: where R¹, R², R³ and R⁴ are as defined above, and where X¹ represents a halogen, a mercapto group, a nitrogen-con­ taining 5-membered aromatic-heterocyclic-n-yl group or a expressed by the formula-S(O) n -Z (where z denotes a hydroxy group or alkyl group and n is 1 or 2), X² represents a halogen, a mercapto group, a cyanamide group or a group expressed by the formula -S(O) n -Z, and X³ represents a halogen or a group expressed by the formula -S(O) n -Z. (1) exhibits histamine H₂ antagonism and is useful as a medicine for treating ulcers.

Description: SPECIFICATION PROCESS FOR PREPARING IMIDAZOLE DERIVATIVES - This invention relates to new processes for preparing an imidazole derivative of the formula: EMI1.1 wherein R1 and R4 are each lower alkyl, and R2 and R3 are each lower alkylene, or a salt thereof. An imidazole derivative of the formula (I) or a salt thereof obtained by this invention has been known as a compound having histamine H2-antagonist activity and is useful as an anti-ulcer agent. The processes of this invention are illustrated by the following schemata. Process 1: EMI1.2 Process 2: EMI2.1 Process 3: EMI2.2 wherein R1 R2 R3 and R4 are each as defined above; X1is halogen, mercapto, an aromatic 5-membered N-containing heterocycle-N-yl group or a group of the formula: -S(O) -Z in -which Z is hydroxy or alkyl, and n is 1 or 2; X2 is halogen, mercapto, cyanamide, an aromatic 5-membered N-containing heterocycle-N-yl group or a group of the formula: -S(O) -Z in which Z and n are each as defined above; and X3 is halogen or a group of the formula: -S(O) -Z in which Z and n are each as defined above. Among the processes of this invention, the Process 1 can be carried out by reacting a compound (II) with a compound (III). As to the starting material (II), the lower alkyl group for R1 may be a straight or branched alkyl group having 1 to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl and the like, and lower alkylene group for R2 and R3 may be a straight or branched alkylene group having 1 to 6 carbon atoms such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, 2-methyltrimethylene, 2,2-dimethyltrimethylene and the like. The lower alkylene groups for R2 and R3 may be the same or different from each other. As to the other starting material (III), the lower alkyl group for R4 may be the same as those of R1. Halogen for X1 may be chlorine, bromine and iodine. The aromatic 5-membered N-containing heterocycle-N-yl group for X1 may be l-pyrazolyl, l-iidazolyl, 1pyrrolyl, 1,2,3-triazol-l-yl, 3,5-dimethyl-1-pyrazolyl, 1,2,4-triazol-4-yl or the like. The group of the formula: -S(O) - for X1 may be sulfino, sulfo, alkylsulfinyl having 1 to 6 carbon atoms (e.g. methylsulfinyl, ethylsulfinyl, propylsulfinyl, isopropylsulfinyl, butylsulfinyl, isobutylsulfinyl, tert-butylsulfinyl, pentylsulfinyl, hexylsulfinyl etc.), or alkylsulfonyl having 1 to 6 carbon atoms (e.g. methylsulfonyl, ethylsulfonyl, propylsulfonyl, isopropylsulfonyl, butylsulfonyl, isobutylsulfonyl, tert-butylsulfonyl, pentylsulfonyl, hexylsulfonyl, etc.). The reaction of this process may be generally carried out in a conventional solvent such as alcohol (e.g. methanol, ethanol, propanol, butanol, isopropyl alcohol, etc.), acetonitrile, methylene chloride, dimethylformamide, dimethylsulfoxide, dioxane, tetrahydrofuran, and the like. The reaction temperature is not critical and the reaction is generally carried out at room temperature to the boiling point of the solvent. In case that the compound (III) wherein X is halogen, sulfino or sulfo group is used as a starting material, the reaction is preferably carried out in the presence of a base such as triethylamine, pyridine, N-methylaniline, 1,5-diazabicyclof5.4.0]undec-5-ene and the like. And in case that the compound (III) wherein X1is a mercapto group is used as a starting material, the reaction is preferably carried out in the presence of a compound of heavy metal (e.g. mercury, silver, lead, etc.). The compound (III) wherein X1 is a sulfino or sulfo group may be used in a form of a salt such as an alkali metal salt (e.g. sodium salt, potassium salt, etc.), 1,5-diazabicyclo[5.4.0]undec-5-ene salt, and the like. The aforementioned Process 2 may be carried out by reacting a compound (IV) with a compound (V). As to the starting compounds (IV) and (V), the lower alkyl group for R1 and R4, the lower alkylene group for R2 and R3, halogen, an aromatic 5-membered N-containing heterocycle-N-yl group and the group of the formula: -S(O) -Z for X2 may be the same as those illustrated in the above Process 1, respectively. The reaction of this process may be carried out in a solvent as exemplified in the above Process 1, and generally under cooling or at room temperature. The aforementioned Process 3 may be carried out by reacting a compound (VI) with cyanamide (VII) or its salt. As to the starting compound (VI), the lower alkyl group for R1 and R4, the lower alkylene group for R2 and R3, and halogen and the group of the formula: -S(O), Z may be the same as those as exemplified in the aforementioned Process 1, respectively. Suitable salt of the cyanamide (VII) may be nn alkali metal salt such as sodium salt, potassium salt, and the like. The reaction of this process may be generally effected in a conventional solvent such as methylene chloride, acetonitrile, dimethylformamide, or the like. The reaction temperature is not critical, and generally. the reaction may be carried out under warming or heating. In case that the cyanamide (VII) is used in a free form as a starting material, the reaction is preferebly carried out in the presence of a base as exemplified in the aforementioned Process 1. The imidazole derivative (I) produced by the processes of this invention may be isolated and purified, and if desired, converted into its salt such as hydrochloride in a conventional manner. The starting materials to be used in the processes of this invention can be prepared by the method described in the following examples or by a method similar thereto. The following examples illustrate this invention in more detail. Example 1 (1) To a stirred suspension of N-cyano-N',Sdimethylisothiourea (60 g) in CHCl3 (600 ml) was added a solution of chlorine (82.6 g) in CHC13 (500 ml) over 30 min. at 0 - 50C. After stirring for 1.5 hrs. at the same temperature, the solvents were evaporated under a reduced pressure and the residue was washed with dry benzene and dried in vacuum. The resulting white powder was dissolved in hot dry acetone (250 ml). After filtration of the insoluble impurities, the filtrate was passed through a short column of SiO2(60 g) and eluted with CH2Cl2. The eluate was dried up under a reduced pressure and the residue was recrystallized from aceton-petroleum ether to give N-cyano-N'-methylchloroformamidine (36.8 g). Yield 67.4 %. The resultant was recrystallized twice from benzene-acetone to obtain a white crystal, m.p. 130.5 131.5 OC, Anal. Calcd. for C3H4C1N3: C, 30.60; H, 3.43; N, 35.75; C1, 30.16 Found: C, 30.69; H, 3.25; N, 35.63; C1, 29.82 IR (nujol) v max: 3240, 3020, 2220, 1625, 1540, 1403, 1318, 1272, 1257, 1172, 1095, 1048, 1020, 733, 722 cm H-NMR (CD30D) b 2.92 (s, 3H) (2) To a stirred solution of 2-(5-methylimidazol-4-ylmethylthio)ethylamine (1.0 g) and triethylamine (0.71 g) in methanol (20 ml) was added N cyano-N'-methylchloroformamidine (0.82 g) and stirred for 7.5 hrs. at 50 - 55 OC. After evaporation, the residue was subjected to chromatography on SiO2 [eluant: CHC13-MeOH (10:1)]. The resulting crude product was added to water (3 ml) and extracted repeatedly with ethyl acetate. Ethyl acetate extracts were dried over anhydrous MgSO4 and concentrated under a reduced pressure to small volume. The resulting crystals were collected by filteration and washed with ethyl acetate to give N"-cyano-N-methyl-N-[2-(5-methylimidazol- 4-ylmethylthio)ethyl]guanidine (0.33 g). Yield 22.4 %, m.p. 134 - 137 OC. Example 2 A suspension of N-cyano-N'-methylthiourea (DBU salt) (0.534 g), 2-(5-methylimidazol-4-ylmethyl- thio)ethylamine (1.03 g), HgO (0.868 g) and anhydrous sodium sulfate (2 g) in CH3CN (20 ml) was heated under reflux for 20. hrs. with vigorous stirring. The hot reaction mixture was filtered and the filtrate was dried up and subjected to chromatography on SiO2 [eluant: CH3CN-CH30H (4:1)]. The resulting crude product was purified by preparative thin layer chromatography trio2, AcOEt-MeOH- 28 % aq. NH3 (10:1:1)] and recrystallized from CH3CN to give N"-cyano-N methyl-N'-[2-(S-methylimidazol-4-ylmethylthio)ethyl]- guanidine (38.4 mg). Yield 7.6 %, np. 136 - 138 OC. Example 3 (1) To a stirred suspension of N-cyano-N',Sdimethylisothiourea (19.4 g) in acetone (700 ml) was added dropwise a solution of m-chloroperbenzoic acid (80 % purity, 38.8 g) in acetone (120 ml) at 20 - 25 OC, After stirring for 1 hr. at the same temperature, the reaction mixture was cooled in an ice bath for 1 hr. and the precipitate was filtered and washed with acetone to give N-cyano-N' -methyl-methylsulfinylformamidine (13.65 g). Yield 62.8 %, m.p. 115.5 - 116 OC. Anal. Calcd. for C4H7N3 OS: C, 33.09; H, 4.86; N, 28.94; S, 22.07 Found: C, 33.08; H, 4.78; N, 28.79; S, 22.14 IR (nujol) v max: 3240, 2200, 1621, 1512, 1418, 1393, 1282, 1173, 1073, 1033, 883, 743 cm 1 NMR (DMSO-d6) : a 2.82 (s), 2.84 (s) A small crop (2.60 g, m.p. 112 - 112.5 OC) of the same product was further obtained from the filtrate. (2) A solution of N-cyano-N'-methyl-methylsulfinylformamidine (493 mg) and 2-(5-methylimidazol4-ylmethylthio)ethylamine (684 mg) in CH3CN (20 ml) was stirred for 4 hrs. at room temperature. After concentration under a reduced pressure, the residue was subjected to chromatography on SiO2 [eluant: CH3CN-CH30H (4:1)]. The product obtained was recrystallized from CH3CN to give N"-cyano-N-methyl-N'-f2-(5-methylimidazol-4-yl- methylthio)ethyl]guanidine (684 mg). Yield 79.7 %, m.p. 136 - 138 OC. Example 4 (1) To a stirred suspension of NaH (50 % oil suspension, 3.58 g) in THF (160 ml) was added pyrazole (5.84 g) at a temperature below room temperature and stirred for 1 hr. To the mixture was added N-cyano N' -methyl-methylsulfinylformamidine (8.32 g, obtained by the same procedure as in Example 3 (1)) and stirred for 3 hrs. at room temperature. After evaporation under a reduced pressure, the residue was dissolved in water and washed with ether. The aqueous layer was acidified (pH 4) with 10 % HC1 under ice-cooling. The precipitate was filtered, washed with water and dried to give 1- (N- cyano-N'-methylamidino)pyrazole (7.52 g). An additional amount (0.2 g) of the same product was further obtained from the filtrate.. The crude products were combined and recrystallized from ethyl acetate to give the purified product (6.12 g). Yield 71.7 %, m.p. 166.5 - 168 OC. Anal. Calcd. for C6H7N5: C, 48.31; H, 4.73; N, 46.96, Found: C, 48.40; H, 4.69; N, 46.81. IR (nujol) y max: 3280, 2200, 1660, 1645, 1540, 1421, 1387, 1348, 1268, 1207, 1173, 1084, 1040, 985, 922, 908, 838, 765,702 cm 1 NMR (DMSO-d6): a 3.13(s, 3H), 6.65 (dd, J=2Hz, J=3Hz, 1H), 7.95 (d, J=2Hz, 1H), 8.53 (d, J=3Hz, 1H). (2) A solution of l-(N-cyano-N'-methylamidino)- pyrazole obtained above (373 mg) and 2-(5-methylimidazol4-ylmethylthio)ethylamine (503 mg) in CH3CN (15 ml) was heated under reflux for 24 hrs. The reaction mixture was concentrated under a reduced pressure and the residue was subjected to chromatography on SiO2 [eluant: CH3CN-CH30H (4:1)]. The crude product obtained was recrystallized from CH3CN to give N"-cyano-N-methyl-N' [2-(5-methylimidazol-4-ylmethylthio)ethyl]guanidine (359 mg). Yield 56.9 %, m.p. 137 - 138.5 OC. Example 5 (1) N-cyano-N-methylthiourea (DBU salt) (10 g) in water (20 ml) was added to a solution of 35 % H202 (21.8 g) and NaWO4.2H2O (0.1 g) in water (40 ml) under ice-cooling. After stirring at room temperature for 1.5 hrs., the precipitate was filtered off. The filtrate was concentrated under a reduced pressure and purified by column chromatography [HP-20 resin (Mitsubishi Chem. Ind. Ltd.)] to obtain DBU salt of cyanoimino-methylaminomethanesulfonic acid (1.5 g, 12.7 %). The product was further recrystallized from (CH3)2CHOH to give purified DBU salt of cyanoiminomethylaminomethanesulfonic acid, m.p. 135 - 136 OC. Anal. Calcd. for C12H21N503S: C, 45.70; H, 6.71; N, 22.21; S, 10.16 Found: C, 45.82; H, 6.71; N, 22.20; S, 10.12 IR (nujol) v max: 3290, 3160, 2190, 1650, 1608, 1523, 1460, 1415, 1380, 1325, 1263, 1232, 1215, 1203, 1105, 1060, 1028, 1003, 727 cm 1 (2) A solution of cyanoimino-methylaminomethanesulfonic acid (DBU salt) (0.70 g) and 2-(5 methylimidzol-4-ylmethylthio)ethylamine (0.57 g) in ethanol (14 ml) was heated under reflux for 7 hrs. After removal of the solvent under a reduced pressure, the residue was purified by column chromatography on SiO2 [eluant: CH3CN-CH30H (4:1)3. After concentration of the eluate under a reduced pressure, the residue was subjected to preparative thin layer chromatography [SiO2, CH3COOCH3-CH30H- 28 % NH3(aq) (10:1:1)] and then recrystallized from CH3OH-CH3CN to give N"-cyano-N methyl-N' - ±2- (5-methylimidazol-4-ylmethylthio) ethyl] - guanidine (0.18 g). Yield 32.4 %, m.p. 140 - 141 OC. Example 6 (1) To a solution of sodium metal (1.01 g) in ethanol (120 ml) were added cyanamide (18.5 g) and N-cyano-S-methyl-N' - [2- (5-methylimidazol-4-ylmethyl- thio)ethyl]isothiourea (10.76 g). The resulting mixture was heated under reflux for 1.5 hrs. After concentration under a reduced pressure, the residue was added to cold water (50 ml) and acidified (pH 4.5) with 10 % HC1 and cooled for 1 hr in an ice bath. The precipitate was filtered, washed with water and dried. The resulting crude product (7.43 g) was recrystallized from C2H5OH-H2O (1:1) to give N,N'-dicyano-N"-[2-(5 methylimidazol-4-ylmethylthio) ethyl] guanidine (5.17 g). Yield 49.2 %, m.p. 183 - 186 OC. Anal. Calcd. for CloHl3N7S: C, 45.61; H, 4.98; N, 37.24; S, 12.18 Found: C, 45.59; H, 4.99; N, 36.51; S, 12.17 IR (nujol) v max: 3330, 3110, 2660, 2170, 1575, 1518, 1435, 1378, 1348, 1310, 1230, 867 cm 1 NMR (DMSO-d6+D20): 8 6 2.32 (s, 3H), 2.4 - 2.7 (m, 2H), 3.26 (t, J=7Hz, 2H), 3.83 (s, 2H), 8.77 (s, 1H) (2) N,N'-Dicyano-N"-[2-(5-methylimidazol- 4-ylmethylthio)ethyl]guanidine (527 mg) was added to a solution of CH3NH2 in ethanol (40 %, 3.1 g) and stirred for 47 hrs. at room temperature. After concentration under a reduced pressure, the residue was triturated with CH3CN. The insuluble starting material was filtered off and the filtrate was concentrated under a reduced pressure and chromatographed on SiO2 [eluant: CH3CN CH3OH (4:1)]. The resulting crude product was purified by preparative thin layer chromatography rio2, C H3- COOC2H5-CH3OH- 28 % NH3 (aq) (10:1:1)] and recrystallized from CH3CN to give N"-cyano-N-methyl-N'-[2-(5-methylimidazol-4-ylmethylthio)ethyl]guanidine (1.0 mg). m.p. 135 - 137 OC. Example 7 (1) A solution of 2-(5-methylimidazol-4-ylmethylthio)ethylisothiocyanate[obtained from its hydrochloride (4.17 g)] in CHC13(20 ml) was added to a solution of cyanamide (1.05 g) and DBU (3.80 g) in CHCl3 (50 ml) and stirred overnight. After concentration, the residue was dissolved in water (30 ml) and washed with ether, decolorized with charcoal and acidified to pH 5 with 10 % HC1 under ice-cooling. The precipitate was filtered, washed with water and dried to give N-cyano-N'-f 2- (5-methylimidazol-4-ylmethyl- thio)ethyl]thiourea(mono-hydrate, 3.57 g). Yield 78.1 %, m.p. 158 - 161 OC. Anal. Calcd. for C9H13N5 S 2.H2O: C, 39.54; H, 5.53; N, 25.62; S, 23.46, Found: C, 39.71; H, 5.44; N, 25.69; S, 22.73 IR (nujol) v max: 3400, 3270, 3130, 2760, 2650, 2190, 1652, 1540, 1470, 1430, 1381, 1362, 1278, 1237, 1217, 1205, 1103, 1088, 967, 837 cm 1 NMR (DMSO-d6+D2O) : 8 2.32 (s, 3H), 2.4 - 2.8 (m, 2H), 3.0 - 3.67 (m, 2H), 3.87 (s,'2H), 8.93 (s, 1H). (2) To a suspension of N-cyano-N'-f2-(5- methylimidazol-4-ylmethylthio) ethyl] thio;urea (monohydrate, 765 mg) in CH2C12 (7 ml) was introduced dry HC1 gas for a few minutes under ice-cooling. PC15 (1.25 g) was added to the mixture and stirred at room temperature for 3 hrs. The reaction mixture containing N'-cyano-N-t2-(5-methylimidazol-4-ylmethylthio)ethyl]- chloroformamidine was concentrated to small volume, diluted with CH2C12 (5 ml) and cooled to -5 OC. To the mixture was added a solution of CH3NH2 in C2H5OH (40 %, 15 ml) below 30 OC. After stirring for 20 hrs. at room temperature, the reaction mixture was filtered and the filtrate was concentrated to small volume, diluted with CH3CN and filtered agein. The filtrate was dried up and the residue was purified with column chromatography [SiO2, CH3CN-CH3OH (4:1)], preparative thin layer chromatography [SiO2, CH3COOC2H5-CH3OH28 % NH3(aq) (10:1:1)] and then recrystallization from CH3CN to give N"-cyano-N-methyl-N' - [2-' (5-methylimidazol- 4-ylmethylthio)ethyl]guanidine (10.4 mg). Yield 1.5 %, m.p. 136.5 - 138 OC. Example 8 A solution of N-methyl-chloroformimidoyl chloride (1.12 g), 2- (5-methylimidazol-4-ylmethylthio) - ethylamine (0.855 g) and DBU (0.988 g) in CH2C12 (16 ml) was heated under reflux for 6 hrs. To the reaction mixture containing N '-methyl-N- [2- (5-methylimidazol- 4-ylmethylthio)ethylichloroformamidine was added a solution of cyanamide (0.84 g) and DBU (3.04 g) in CH2C12 (16 ml). After refluxing for 15 hrs., the solvent was removed and the residue was chromatographed [SiO2, CH3CN-CH30H (4:1)]. The crude product was purified by preparative chromatography [SiO2, CH3COOC2H5 CH30H- 28 % NH3 (aq) (10:1:1)] and then recrystallization from CH3CN to give N"-cyano-N-methyl-N'-[2-(5-methyl- imidazol-4-ylmethylthio)ethyl]guanidine (0,24 g). Yield 19.0 %, m.p. 139 - 141 OC.

Claims: CLAIMS 1. A process for preparing an imidazole derivative of the formula: EMI16.1 wherein R1 and R4 are each lower alkyl, and R2 and R3 are each lower alkylene, which comprises reacting a compound of the formula: EMI16.2 wherein R1, R2 and R3 are each as defined above, with a compound of the formula: EMI16.3 wherein R4 is as defined above, and xl is halogen, mercapto, aromatic 5-membered N-containing heterocycle-N-yl or a group of the formula: -S(O) -Z in which Z is hydroxy or alkyl, and n is 1 or 2. 2. A process for preparing an imidazole derivative of the formula: EMI17.1 wherein R1 and R4 are each lower alkyl, and R2 and R3 are each lower alkylene, which comprises reacting a compound of the formula: EMI17.2 wherein R1 R2 and R3 are each as defined above, and X2 is halogen, mercapto, cyanamide, aromatic 5-membered N-containing heterocycle-N-yl or a group of the formula: -S(O) -Z in which Z is hydroxy or alkyl, and n is 1 or 2, with a compound of the formula: R4-NH2 wherein R4 is as defined above. 3. A process for preparing an imidazole derivative of the formula: EMI17.3 wherein R1 and R4 are each lower alkyl, and R2 and R3 are each lower alkylene, which comprises reacting a compound of the formula: EMI18.1 wherein R1, R2, R3 and R4 are each as defined above, and X3 is halogen or a group of the formula: -S(O) -Z in which Z is hydroxy or alkyl, and n is 1 or 2, with cyanamide or its salt.

Inventors: DURANT, GRAHAM JOHN, NAKAI, YOSHIHARU, TERAJI, TSUTOMU
Applicants: SMITHKLINE BECKMAN CORPORATION
Application year: 1981
Main classification: C07D233
IPC codes: C07D233, C07D521