1,4-Dihydropyridines

Abstract: The invention concerns compounds of formula or salts thereof; wherein: α and β together represent a bond and additionally when B is an electron withdrawing group α can also represent OH and β can represent hydrogen; Ar is an optionally substituted aryl radical; R represents hydrogen or an optionally substituted alkyl or aralkyl group; R¹ and R² are the same or different and are selected from hydrogen and saturated or unsaturated, cyclic or acyclic aliphatic hydrocarbon residues optionally substituted by one or more groups selected from halogen, OH, carboxy, CN, alkoxy, alkylthio, aryloxy, alkoxycarbonyl, amino, substituted amino, and optionally substituted aryl; A represents a group of formula -XR³ wherein X is a group of formula -(CHR⁶) p -Y-(CHR⁷) q - ­ in which formula : Y represents -O-, -S-, NR⁸ or a direct bond, p and q each represent 0, 1 or 2 R⁶, R⁷ and R⁸ independently represent hydrogen or lower alkyl and R³ is an optionally substituted nitrogen ring heteroaryl radical optionally containing other ring heteroatoms selected from oxygen, nitrogen or sulphur; B represents haloalkyl, optionally substituted phenyl, -CN, -CHO, -CH(Olower­ alkyl)₂ or -CH²OH.

Description: This invention relates to heterocyclic compounds possessing pharmaceutical activity, more particularly to 1,4-dihydropyridines, processes for preparing them and pharmaceutical compositions containing them. EP Publication Nos 1054, 174131 and 225175 disclose antihypertensive 1,4-dihydropyridines having substituted N-heterocyclic groups linked to the 2 position. None of the aforementioned publications disclose thromboxane synthetase or blood platelet inhibitory activity for the 1,4-dihydropyridines. In one aspect this invention provides use of a compound of formula or a pharmaceutically acceptable salt thereof; wherein; α and β together represent a bond and additionally when B is an electron withdrawing group α can also represent -OH and β can represent hydrogen; Ar is a C₆-C₁₀ aryl or heteroaryl of 5 to 10 ring atoms, each group optionally substituted on carbon atoms by one or more substituents selected from halogen, C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ haloalkyl, C₁-C₆ haloalkoxy, NO₂, NH₂, CN, C₁-C₆ alkylamino, di(C₁-C₆)alkylamino, carboxy, C₂-C₇ alkoxycarbonyl, acyl, acylamino, aryl of 6 to 10 carbon atoms, heteroaryl of 5 to 10 ring atoms or C₁-C₆ aminoalkyl; R represents hydrogen or a C₁-C₆ alkyl group or benzyl group each optionally substituted by one or more substituents as defined above for Ar; R¹ and R² are the same or different and are selected from hydrogen, saturated C₅-C₇ cyclic aliphatic hydrocarbon residues unsaturated acyclic aliphatic hydrocarbon residues of up to 6 carbon atoms and saturated C₁-C₆ acyclic aliphatic hydrocarbon residues, said residues being optionally substituted by one or more group selected from halogen, OH, carboxy, CN, C₁-C₆ alkoxy, C₁-C₆ alkylthio, C₆-C₁₀ aryloxy, C₂-C₇ alkoxycarbonyl, amino, di(C₁-C₆)alkylamino and C₆-C₁₀ aryl or heteroaryl of 5-10 ring atoms, said aryl and heteroaryl groups being, optionally substituted by one or more substituents as defined above for Ar; A represents a group of formula -XR³ wherein X is a group of formula -(CHR⁶) p -Y-(CHR⁷) q - in which formulae: Y represents -O-, -S-, NR⁸ or a direct bond, p and q each represent 0, 1 or 2 providing that p and q do not both represent zero when Y is a direct bond; R⁶, R⁷ and R⁸ independently represent hydrogen or C₁-C₆ alkyl, and R³ is a mono- or bi-cyclic nitrogen ring heteroaryl radical of 5 to 10 rings atoms optionally containing other ring heteroatoms selected from oxygen, nitrogen and sulphur; said heteroaryl group being optionally substituted optionally substituted by one or more substituents as defined in connection with Ar; and B represents C₁-C₆ haloalkyl, CN, -CHO -CH(C₁-C₆alkoxy)₂, CH₂OH or phenyl optionally substituted as for Ar above, in the preparation of a medicament for inhibiting blood platelet aggregation or thomboxane synthetase in a mammal. By the term aryl and heteroaryl as groups or part of groups (e.g aryloxy, arylalkyl) is meant any monovalent carbcyclic or heterocyclic radical possessing aromatic character such as phenyl, naphthyl, pyridyl (e.g 2-, 3- or 4-pyridyl), thienyl (e.g. 2-thienyl) furyl (e.g. 2-furyl), quinolyl (e.g. 2-, 3- or 4-quinolyl), isoquinolyl (e.g. 2,3- or 4- isoquinolyl) and benzimidazolyl. Preferred heteroatoms are nitrogen, oxygen and sulphur. Examples of heterocyclic aromatic rings containing two heteroatoms are imidazolyl, e.g. 1-imidazolyl, thiazolyl e.g. 5-thiazolyl and pyrimidyl e.g. 5-pyrimidyl. The term alkyl when used to signify a group or part of a group such as arylalkyl or alkyloxy means any straight or branched saturated aliphatic hydrocarbon having 1 to 6 carbon atoms, e.g 1-4 carbon atoms. Examples are methyl, ethyl, n-propyl, isopropyl, n-butyl, hexyl and n-hexyl. By the term 'optionally substituted' is meant optional substitution on carbon atoms by one or more substituents selected from halogen (e.g Cl,Br,F), alkyl, alkyloxy, haloalkyl (e.g. CF₃), or haloalkoxy (e.g. CHF₂O-, CF₃CH₂O-), NO₂, NH₂, CN, alkylamino, dialkylamino, carboxy, alkyloxycarbonyl, acyl, acylamino, aryl (e.g. phenyl) or aminoalkyl. Examples of the group R are groups as described above in connection with alkyl and include hydrogen, methyl, ethyl, n-propyl, isopropyl and benzyl. Preferably R is hydrogen. The groups R¹ and R² can be independently hydrogen, or saturated or unsaturated acylic hydrocarbon chains of 1-6 carbon atoms, e.g C₁-C₆ alkyl or alkenyl, optionally substituted by aryl of 5 to 10 ring atoms,heteroaryl of 5-10 ring atoms C₁-C₆ alkoxy, amino, di(C1-C6)alkylamino, carboxyl or C₂-C₇ alkoxycarbonyl. Examples of R¹ and/or R² are methyl, ethyl, n-propyl, isopropyl, butyl, methoxymethyl, methoxyethyl, ethoxymethyl, ethoxyethyl, methoxypropyl, aminomethyl, 2-aminoethyl, 3-aminopropyl, dimethylaminoethyl, 2-carboxyethyl, ethoxycarbonylmethyl. When R¹ or R² is alkyl substituted by aryl or heteroaryl examples are benzyl, pyridylmethyl or -ethyl (e.g. 3-pyridylmethyl), imidazolylmethyl (e.g. 1-imidazolylmethyl) or imidazolylethyl. Preferred values for R¹ and/or R² are methyl and ethyl. Examples of R³ are imidazolyl (e.g. 1- or 3-imidazolyl), pyridyl (e.g. 2- or 3-pyridyl), thiazolyl (e.g. 2-thiazolyl), pyrrolyl (e.g. 1-pyrrolyl) or bicyclic rings such as benzimidazolyl (e.g. 1-benzimidazolyl), quinolyl (e.g. 2- or 4-quinolyl), isoquinolyl (e.g. 1- or 4-isoquinolyl), imidazopyridyl (e.g. 5-imidazo[1,5-a]-pyridyl). Preferred values are 1-imidazolyl, 3-pyridyl and 5-imidazo[1,5-a]-pyridyl. Examples of X are independently -NH; -O-; -S-; -CH₂-; -CH(CH₃)-; -OCH₂-; -CH₂O-; -(CH₂)₂-O-; -CH₂CH(CH₃)-; CH(CH₃)CH₂-; or a group of formula -CH₂-Z-CH₂-, -CH₂-Z-(CH₂)₂-, -(CH₂)₂-Z-CH₂- where Z is S, NH or a direct bond. Examples of B are -CN, -CHO, -CH₂(OMe)₂ or alkyl groups of 1 to 3 carbon atoms substituted by one or more halogen atoms such as fluorine, chlorine and/or bromine especially mono-, di or tri-fluoromethyl, mono, di- or tri-chloromethyl. Preferred examples of X are -CH₂-, -(CH₂)₂-, -CH(CH₃)-, -CH₂CH(CH₃)-, -CH(CH₃)CH₂-, -CH₂O-, -CH₂NH- and -CH₂-S-. Preferably B is -CH₂F. Examples of Ar are groups mentioned above for the definitions of aryl and included in the preferred values are 2- and/or 3-substituted phenyl groups,e.g. 2- and/or 3-nitrophenyl; 2,3-dichlorophenyl; 2-trifluoromethylphenyl, pentafluorophenyl, naphthyl (e.g. 1-naphthyl), pyridyl (e.g. 2-pyridyl), halopyridyl (e.g. 2-chloropyrid-3-yl), benzimidazolyl (e.g. 4- or 7-benzimidazolyl). Particularly preferred compounds provided by this invention have formula Ia: wherein α, β, R, R¹ and R² have the meanings given above, R⁵ is H or lower alkyl, X³ is -CH₂-, -CH₂NHCH₂-, -CH₂NH(CH₂)₂-, -CH₂CH₂-, -(CH₂)₂O, or -CH₂O-, -CH(CH₃)-; R¹¹ and R¹² are each selected from hydrogen, nitro, halo or trifluoromethyl and R¹³ is CN, chloro- or fluoro-alkyl especially -CH₂F, CHF₂, CF₃ or -CH₂Cl or a salt thereof, or an optically active isomer thereof. In formula Ia preferably R is hydrogen. Examples of R¹ are H, Me, Et n Pr or i Pr. Examples of R² are Me and Et. When R¹¹ is hydrogen examples of R¹² are 3-nitro, 2-trifluoromethyl. Examples of R¹¹ and R¹² when substituents are 2,3-dihalo, e.g. are 2,3-dichloro, 3-nitro-2-halo and 3-halo-2-nitro. The term "lower" as used herein denotes 1 to 6 carbon atoms. Other preferred compounds are compounds of formula Ia in which 1-imidazolyl is replaced by a pyridine ring, preferably pyrid-3-yl. In the compounds of the invention α and β together preferably represent a bond. The compounds of formula I possess pharmaceutical activity in particular antihypertensive and/or hypotensive activity when tested on warm blooded animals and hence are indicated for the treatment of high blood pressure. In addition since the compounds of this invention antagonise calcium movement into the cell they are also vasodilators and useful in the treatment of a variety of cardiac conditions such as heart attacks, angina pectoris, cardiac arrythmias, cardiac hypertrophy and coronary vasospasm. Furthermore the compounds of formula I also inhibit blood platelet aggregation and inhibit thromboxane synthetase. These latter activities in combination with their antihypertensive properties makes these compounds potentially very useful for the treatment of cardiovascular disorders, especially thrombosis. Antihypertensive activity is demonstrated by the following standard procedure: The blood pressures of male or female spontaneously hypertensive rats are measured in a 37°C constant temperature housing by means of a tail cuff. Rats with systolic pressures below 155mmHg are discarded. Groups of rats are dosed orally with the test substance in a suitable vehicle or with vehicle alone. Systolic pressures are recorded before dosing and at selected time points afterwards. Heart rates are derived from caudal artery pulses. Results are analysed statistically by means of 2 way analysis of variance (within group). Calcium antagonist activity is demonstrated by examining drug effect on the response of isolated rat portal vein to increasing calcium ion concentration in vitro. Ability to inhibit blood platelet aggregation is tested for by a modification of the procedure of Fantl, Australian J.Exp.Biol.Med.Sci. 45 , 355-62 1967. Since platelet aggregation is the initial step in thrombus formation it is considered that compounds which prevent aggregation or reduce platelet adhesiveness may inhibit the initiation of the atherosclerotic process. The effect of drugs on adhesiveness is measured in platelet-rich plasma containing a small amount of arachidonic acid which markedly increases aggregation in vitro and may be a physiological agent for doing so in vivo . The actual test procedure used is described below. New Zealand White rabbits (2.5-3kg) are anaesthetised with an injection, via the marginal ear vein, of sodium pentobarbitone 30-40 mg/kg. The carotid artery is cannulated and blood (100-150 ml) is withdrawn into 50 ml syringes containing 3.8% sodium citrate (Ratio blood: citrate = 9:1). Blood is centrifuged at 200g (1500 r.p.m.) for 10 minutes at 5°C. and the platelet rich plasma (PRP) removed. The platelets are then kept at room temperature in a screw topped plastic centrifuge tube for the duration of the experiment. A twin channel platelet aggregometer - (HU aggregometer, A.Browne Ltd, Leicester, UK) is used. 1.0 ml aliquots of PRP are prewarmed for 5-10 minutes and stirred continuously at 1100rpm. Aggregation is induced by addition of 250µM arachidonic acid, (8µl volume) to the PRP samples. The aggregometer output is set at maximum and the chart recorder sensitivity is altered to give a full scale deflection to this arachidonic acid response. Control responses are recorded as the maximum deflection obtained after addition of 250µM arachidonic acid. PRP samples are preincubated for 5 minutes with the test compounds followed by arachidonic acid addition. The maximum deflection after the addition of arachidonic acid is then recorded. All drugs are screened initially at 10⁻⁴M (final concentration), i.e. 10µl of a 1 x 10⁻²M stock solution of the drug dissolved in distilled water is added to the PRP. Dazoxiben, a thromboxane synthetase inhibitor (Randall, M.J. et al Research 23 145-162, 1981) is used as a positive control and all test components are compared with Dazoxiben. Compounds possessing thromboxane synthetase inhibitory activity are useful in the treatment or prevention of diseases responsive to the inhibition of thromboxane synthetase especially cardiovascular disorders such as thrombosis, atherosclerosis, cerebral ischaemic attacks; and angina pectoris; peripheral vascular diseases and migraine. The ability to inhibit thromboxane production is demonstrated by the following standard test: a) Generation of thromboxanes Blood (approx. 75 ml) is obtained from an anaesthetised rabbit and centrifuged at 200g for 10 minutes to obtain platelet rich plasma (PRP). An aliquot of PRP is incubated for 10 minutes at 37°C in the presence of vehicle or drug. Platelet aggregation is induced by the addition of adenosine diphosphate and adrenaline. The tubes are incubated for 3 minutes, centrifuged at 10,000g for 3 minutes and a 50 ml aliquot of the supernatant taken for radio-immunoassay of thromboxane B₂ (TxB₂). b) Radio-immunoassay of TxB₂ The total incubation volume is 150µl containing 50µl of ³H -TxB₂ (0.005 µCi), 50 µl of sample or authentic TxB₂ ranging from 5 to 300 pg per tube as standards and 50µl of rabbit anti-sera to TxB₂ (in a concentration which will bind 50% of H-TxB₂). After incubation for 1 hour at room temperature the tubes are further incubated for 16-20 hours at 4°C. 1ml of dextran-coated charcoal (2.5% w/v suspension in phosphate buffer pH 7.4) is then added to the tubes which are further incubated on ice for 10 minutes. Following the incubation the samples are centrifuged at 10,000g for 10 minutes and 500 µl of the supernatant added to 5ml of scintillation cocktail. Measurement of the radioactivity in the supernatant quantifies the amount of [³H]-TxB₂ bound by the antibody. The concentration of unlabelled TxB₂ in the sample is then determined from a linear standard curve. This invention also provides processes for preparing the compounds of formula I. In general both the compounds of formula I and intermediates of analogous structure may be prepared by processes which are known or are analogous to known processes; see for example Drugs of the Future, Vol. VI, No. 7, 1981 pps 427-440. A first general process for preparing compounds of formula I as hereinbefore defined wherein B is fluoroalkyl, -CN, -CHO, -CH₂OH,-CH(O lower alkyl)₂ or optionally substituted phenyl with the proviso (a) that when y is O, -S- or -NR⁸- then p is 1 or 2, comprises reacting corresponding compounds of formula wherein Ar, R, R¹ and R² are as defined above, and one of T¹ and T² is A, the other is B wherein A and B are as defined immediately above. The process is conveniently carried out by heating, e.g. at reflux, in an inert solvent preferably polar such as ethanol, toluene, dimethylformamide, isopropanol, acetonitrile. A second general process for preparing compounds of formula I as hereinbefore defined and subject to the proviso (a) in the first process mentioned above, comprises reacting a corresponding compound of formula II as shown above with a corresponding compound of formula wherein Ar, R, R¹ and R² are as defined above, and one of T¹ and T² is A, the other is B. This process may conveniently be carried out by heating e.g. at reflux in an inert solvent (preferably polar) such as ethanol, acetonitrile, isopropanol, toluene or dimethylformamide. In yet a further process compounds of formula I wherein the proviso (a) above applies may be prepared by reacting a compound of formula ArCHO with corresponding compounds of formula VI and V shown below wherein Ar, R, R¹ and R² are as defined above and one of T¹ and T² is A, the other is B. Such a process may be carried out by heating the reactants, e.g. at reflux, in an inert solvent (preferably polar) such as ethanol, acetonitrile, isopropranol, toluene or dimethylformamide. In the aforementioned processes when B is an electron withdrawing group compounds of formula I can be prepared wherein α and β are a) a bond or b) α is hydroxy and β is hydrogen. If dehydrating conditions e.g. high reaction temperatures are simultaneously employed then the process favours the production of a 1,4-dihydropyridine product. Compounds of formula I may be prepared by reacting compounds of formula and Z²(CHR⁷) w R³ (VIII) in which formulae B is fluoroalkyl,CN, CHO, CH₂OH, CH(O lower alkyl)₂ or optionally substituted phenyl; α,β,R,R¹,R²,R³,R⁶ and R⁷ are as defined above, one of Z¹ and Z² is halogen (other than fluorine when B is fluoroalkyl) or a sulphonyloxy group; the other of Z¹ and Z² is -YH or Y⁻ as appropriate (wherein Y is as defined above) and v and w are each 0, 1 or 2 with the proviso that (i) when v is 2 and Z² is YH or Y⁻ then Z¹ can also represent dialkylamino, e.g. -NMe₂ or a quaternary ammonium group, e.g. -NMe + / 3 I⁻. The reaction may be carried out in an inert solvent in the presence of base, e.g. K₂CO₃ or a tertiary amine, e.g. triethylamine. Anions of the requisite starting materials may be generated by the usual methods known in the art and reacted. Examples of sulphonyloxy are alkyl- or aralkyl- or aryl-sulphonyloxy, e.g. tosyloxy or mesyloxy. When α is OH and/or β is -CH₂OH,the hydroxy group(s) may be protected e.g. as a benzyl ether before the reaction and deprotected afterwards. The starting materials of formula VII wherein Z¹ is halogen, sulphonyloxy as defined above may be prepared by known methods, e.g. from corresponding compounds of formula by methods known for the conversion of OH to halogen or sulphonyloxy. Compounds of formula IX wherein v=O may be prepared by reacting a compound of formula X wherein R, R¹ and B are as hereinbefore defined with compounds of formulae in which formula Ar and R² are as defined above. Compounds of formula IX wherein v is 1 or 2 may be prepared by reacting a compound of formula wherein v is 1 or 2 and Ar and R² are as defined above with a compound of formula (X) as hereinbefore defined. Compounds of formula VII wherein v is 1, R⁶ is hydrogen and Z¹ is chlorine or bromine may also be prepared by halogenating a corresponding compound of formula wherein Ar, R, R¹, R², α and β are as defined above, e.g. using phenyl trimethylammonium tribromide. Compounds having formula XII are disclosed in EP Publication No. 125803A. Compounds of formula VII wherein v is 2 and Z¹ is -N(alkyl)₂ or a quaternary ammonium group may be prepared by performing a Mannich reaction on a compound of formula using formaldehyde and secondary amine and if required reacting the product with an alkyl halide. Compounds of formula VII wherein Z¹ is Y⁻ may be prepared by known methods. For example, when Z¹ is -OH, -NHR⁸ or -SH anions may be formed in the presence of a strong base, e.g. an alkali metal hydride such as NaH or BuLi. When Y is a direct bond carbanions may be prepared from the corresponding halo compound using for example, lithium diisopropylamine or BuLi. Compounds of formula I wherein α and β are a bond may also be prepared by dehydrating a compound of formula I wherein α represents OH and β represents hydrogen and Ar,A,B,R,R¹ and R² are as defined above. This process may be carried out in a solvent which is inert under the reaction conditions, e.g. CH₂Cl₂ and in the presence of a dehydrating agent, e.g. (CF₃CO)₂O, and a base, e.g. pyridine. The dehydration may also be effected using diethylaminosulphur trifluoride. When the latter reagent is used and B is CH₂OH or CHO then these groups will be converted during the reaction to -CH₂F and -CHF₂ respectively. When B is -CHO in a compound of formula I selective reduction e.g. using an alkali metal borohydride in an alcoholic solvent, gives a compound of formula I wherein B is -CH₂OH. This reaction may be conveniently carried out using sodium borohydride in ethanol. Compounds of formula I wherein B is -CH₂F or -CHF₂ and α and β are a bond may also be prepared by reacting a corresponding compound of formula I wherein B is -CHO or -CH₂L where L is OH or a leaving group with a fluorinating agent such as a dialkylaminosulphur trifluoride, e.g. diethylaminosulphur trifluoride or (2-chloro-1,1,2-trifluoroethyl)diethylamine. Examples of L are organic sulphonyloxy groups such as alkyl, aralkyl- or aryl-sulphonyloxy, especially -OSO₂ lower alkyl, -OSO₂aryl where aryl is for example p-tolyl. The reaction may be carried out with heating in an inert solvent such as methylene dichloride. When B is -CH(O lower alkyl)₂ in a compound of formula I then this group may be hydrolysed selectively to give a compound of formula I wherein B is -CHO. The hydrolysis may be carried out under aqueous acid conditions e.g. hydrochloric acid in a water miscible solvent such as acetone, with or without heating. Compounds of formula I wherein B is CN may be prepared by removing the elements R¹⁰OH from a compound of formula wherein Ar, R, R¹, R², A, α and β are as defined above and OR¹⁰ represents hydroxy or a leaving group, e.g. a 2,4-dinitrophenoxy group using a dehydrating agent e.g. acetic anhydride or thionyl chloride under mild conditions that will not affect other substituents in the molecule. Compounds of formula XIV may be prepared from the corresponding formyl compound by known methods. Compounds of formula I wherein R is other than hydrogen may be prepared by alkylating a compound of formula I wherein R is H in the presence of a strong base, e.g. an alkali metal hydride, with a compound of formula R - halogen where R is as defined above other than hydrogen. Compounds of formula I having ester functional groups, e.g. cyanoethyl- or t-butyl-ester, may be hydrolysed, selectively if appropriate, to give compounds of formula I having carboxyl groups. Alternatively carboxyl groups can be esterified. In any of the aforementioned reactions reactive substituent groups may be protected if susceptible to the reaction conditions and deprotected afterwards. The compounds of formula I possess one or more asymmetric centres and hence optical isomers and mixtures thereof are possible. All such isomers and mixtures thereof are included within the scope of this invention. Where any reaction process produces mixtures of such isomers standard resolution techniques may be applied to separate a specific isomer. In any of the aforementioned reactions compounds of formula I may be isolated in free base form or as acid addition salts as desired. Examples of such salts include salts with pharmaceutically acceptable acids such as hydrochloric, hydrobromic, hydroiodic, sulphuric, phosphoric, nitric, acetic, citric, tartaric, fumaric, succinic, malonic, formic, maleic acid or organosulphonic acids such as methane sulphonic or p-tolyl sulphonic acids. When acidic substituents are present it is also possible to form salts with bases e.g. alkali metal (such as sodium) or ammonium salts. Such salts of the compounds of formula I are included within the scope of this invention. When basic substituents are present then quaternary ammonium salts may be formed by quaternizing with an alkylating agent such as alkyl, or aralkyl halides. Starting materials for the processes described herein are known compounds or can be prepared by analogous methods for known compounds. This invention also provides compounds of formula I and processes for preparing them as described above with the provisos: (i) when Ar is phenyl optionally substituted by by one or more groups selected from halogen, CF₃ CN or NO₂, R is hydrogen or alkyl, R¹ and R² are the same or different alkyl, α and β are a bond, p is 1, q is O or 1 and R³ is a 5 or 6 membered unsaturated nitrogen ring heteroaryl optionally substituted by OH or NH₂ and optionally containing 1 or 2 additional nitrogen ring atoms, then B is other than fluoroalkyl, or (ii) when Ar is phenyl substituted by 3 or 4 substituents or Ar is a 5-membered substituted heteroaryl group in which the heteroatom is selected from oxygen, nitrogen and sulphur and α and β are a bond and B is CHO, haloalkyl or CH₂OH then R³ is other than imidazolyl substituted by three alkyl groups the same or different or 2-amino-6-hydroxypyrimidinyl. This invention also provides pharmaceutical compositions comprising a compound of formula I or a pharmaceutically acceptable salt thereof as defined immediately above. For the pharmaceutical compositions any suitable carrier known in the art can be used. In such a composition, the carrier may be a solid, liquid or mixture of a solid and a liquid. Solid form compositions include powders, tablets and capsules. A solid carrier can be one or more substances which may also act as flavouring agents, lubricants, solubilisers, suspending agents, binders, or tablet disintegrating agents; it can also be encapsulating material. In powders the carrier is a finely divided solid which is in admixture with the finely divided active ingredient. In tablets the active ingredient is mixed with a carrier having the necessary binding properties and compacted in the shape and size desired. The powders and tablets preferably contain from 5 to 99, preferably 10-80% of the active ingredient. Suitable solid carriers are magnesium carbonate, magnesium stearate, talc, sugar, lactose, pectin, dextrin, starch, gelatin, tragacanth, methyl cellulose, sodium carboxymethyl cellulose, a low melting wax and cocoa butter. The term "composition" is intended to include the formulation of an active ingredient with encapsulating material as carrier, to give a capsule in which the active ingredient (with or without other carriers) is surrounded by carriers, which is thus in association with it. Similarly cachets are included. Sterile liquid form compositions include sterile solutions, suspensions, emulsions, syrups and elixirs. The active ingredient can be dissolved or suspended in a pharmaceuitcally acceptable carrier, such as sterile water, sterile organic solvent or a mixture of both. The active ingredient can often be dissolved in a suitable organic solvent, for instance aqueous propylene glycol containing from 10 to 75% of the glycol by weight is generally suitable. Other compositions can be made by dispersing the finely-divided active ingredient in aqueous starch or sodium carboxymethyl cellulose solution, or in a suitable oil, for instance arachis oil. Preferably the pharmaceutical composition is in unit dosage form, the composition is sub-divided in unit doses containing appropriate quantities of the active ingredient; the unit dosage form can be a packaged composition, the package containing specific quantities of compositions, for example packeted powders or vials or ampoules. The unit dosage form can be a capsule, cachet or tablet itself, or it can be the appropriate number of any of these in packaged form. The quantity of active ingredient in a unit dose of composition may be varied or adjusted from 10 to 500 mg or more, e.g. 25 mg to 250 mg, according to the particular need and the activity of the active ingredient. The invention also includes the compounds in the absence of carrier where the compounds are in unit dosage form. Based on the results from animal studies the dosage range for the treatment of humans using a compound of formula I will be in the range from about 5 mg to 500 mg per day depending on the activity of the compound. The following Examples illustrate the invention and methods for preparing compounds of the invention. Since the final product may be sensitive to light, light should be excluded whenever possible during and after synthesis of compounds of the invention. Example 1 1,4-Dihydro-2-fluoromethyl-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-methyl 5-ethyl diester A mixture of methyl 3-amino-4-fluoro-2-butenoate, 3-nitrobenzaldehyde and ethyl 4-(imidazol-1-yl) acetoacetate in ethanol solvent is refluxed for several hours to give the title compound. Examples 2-21 Using a procedure analogous to Example 1 according to the reaction scheme the following compounds of formula IIa are prepared: Ex.No. α/β R¹ R² Ar B A 2. bond Me Et 2,3-dichlorophenyl -CH₂F imidazol-1-ylmethyl 3. bond Me Me 2,3-dichlorophenyl -CH₂F imidazol-1-ylmethyl 4. " Et Et 2-nitrophenyl -CH₂F imidazol-1-ylethyl 5. " Me Me " -CH₂F imidazol-1-ylethyl 6. " Me Et 3-nitrophenyl -CH₂F pyrid-3-yloxymethyl 7. " Et Et " -CH₂F imidazol-1-ylethyl 8. " Et Et 2-fluoro-5-nitrophenyl -CH₂F imidazol-1-ylmethyl 9. " Me Me 2-trifluoromethylphenyl -CH₂F imidazol-1-ylmethyl 10. " Et Et 2-trifluoromethylphenyl -CH₂F imidazol-1-ylmethyl 11. OH/H Me Et 3-nitrophenyl -CF₃ imidazol-1-ylmethyl 12. bond Me Et 3-nitrophenol -CHF₂ imidazol-1-ylmethyl 13. " i Pr Et 3-nitrophenol -CH₂F imidazol-1-ylmethyl 14. " Me Et difluoromethoxyphenyl -CH₂F imidazol-1-ylmethyl 15. " Me Et benzofurazan-4-yl -CH₂F imidazol-1-ylmethyl 16. " Me Et 3-nitrophenyl -CH₂(OMe)₂ imidazol-1-ylmethyl 17. " Me Et 3-nitrophenyl -CH₂(OEt)₂ imidazol-1-ylmethyl 18. " Me Me 2,3-dichlorophenyl " " 19. " Me Et 2-trifluoromethylphenyl " " 20. " Me Et benzofurazan-4-yl -CH₂(OMe)₂ " 21. " Me Et 2-difluoromethoxyphenyl " " Example 22 2-Formyl-1,4-dihydro-6-(imidazolyl-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid-3-methyl 5-ethyl ester (a) The compound of Example 16, 1,4-dihydro-2-(imidazol-1-ylmethyl)-6-dimethoxymethyl-4-(3-nitrophenyl)-pyridine 3,5-dicarboxylic acid 3-ethyl 5-methyl diester, is treated with 2M hydrochloric acid at room temperature to give the title compound. (b) By a similar procedure the compounds of Examples 17-21 are hydrolysed to the corresponding formyl derivatives. Example 23 2-Cyano-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-methyl 5-ethyl ester a) 2-Formyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-methyl 5-ethyl ester is mixed with O-(2,4-dinitrophenyl)hydroxylamine in ethanol and 1 drop of concentrated H₂SO₄ is added to give 2-(2,4-dinitrophenoxyiminomethyl)-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-ethyl 5-methyl ester. Treatment of this product with KOH in ethanol solvent whilst refluxing gives the title compound. b) By a similar procedure to Examples 22 and 23 the compounds of Examples 17 to 21 are converted to their corresponding 2-cyano derivatives. Example 24 1,4-Dihydro-2-hydroxymethyl-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-methyl 5-ethyl ester The compound of Example 22 is treated with NaBH₄ in ethanol solvent to give the title compound. In a similar manner to Examples 22 and 24 the compound of Examples 17 to 21 are converted to their corresponding 2-hydroxymethyl derivatives. Example 25 2-Trifluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-methyl 5-ethyl ester The compound of Example 11 is dehydrated using 1:1 v/v pyridine and trifluoroacetic anhydride to give the title compound, m.p. 190-190.5°C (hydrochloride). Example 26 2-Fluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid 5-ethyl-3-methyl ester a) 2-(Fluoromethyl)-1,4-dihydro-6-methyl-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid 5-ethyl-3-methyl ester (prepared according to EP Publication No. 0125803A. Example 8; 3.62g, 10 mmol) in dichloromethane (40 ml) was treated portion wise with phenyltrimethylammonium tribromide (3.76g, 10 mmol) over 5 minutes at room temperature. After 1 hour the mixture was shaken with water (50 ml, then 2 x 25 ml), then with saturated brine (25 ml), dried (NaSO₄) and evaporated, leaving the impure bromo compound (2-bromomethyl-6-fluoromethyl-1,4-dihydro-4-(3-nitrophenyl)pyridine 3,5-dicarboxylic acid 3-ethyl 5-methyl diester) as a yellow foam (4.47g). b) The crude bromo compound (4.47g) was dissolved in THF and poured into a solution of imidazole (6.8g, 0.1 mole, 10 equiv.) in THF (total volume 40 ml). The solution was kept at room temperature for 67 hours and was then concentrated to a yellow oil which was treated with 2 N hydrochloric acid (60 ml). The acid and residual insoluble gum mixture was extracted with ether (2 x 30 ml, extracts discarded) and then with chloroform (5 x 50 ml). The chloroform extracts were washed with water (25 ml), saturated brine (25 ml), dried (Na₂SO₄), and evaporated to a foam (3.917g) which crystallised from propan-2-ol (40ml) giving the title compound as fine yellow crystals (1.553g), m.p. 199-200° (decomp). Example 27 2-Trifluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid diethyl ester A solution of 1,4-dihydro-2-methyl-4-(3-nitrophenyl)-6-trifluoromethylpyridine-3,5-dicarboxylic acid diethyl ester (prepared according to Example 82 of EP Publication No. 125803A) (3.21g, 7.5mmol) in THF (15ml) was treated at room temperature with phenyl trimethylammonium tribromide (2.82g, 7.5mmol) in portions over 15 minutes. The mixture was stirred at room temperature for 1½ hours and then filtered into a warm solution of imidazole (5.216g, 76.7mmol, 10.23 equiv) in THF (15ml). The resulting solid was washed with further THF (2 x 2.5ml), adding the washings to the filtrate and the mixture was allowed to cool over 2½ hours. TLC indicated complete conversion after 1 hour. The solution was concentrated to an oil which was partitioned between ether (50 ml) and 2 N hydrochloric acid (2 x 37.5 ml, then 15 ml). The acid phases (including a heavy oil that separated below the acid phase in the first extraction) were combined and washed with further ether (25ml), causing the crystallisation of a solid (A) which was collected and washed with ether (20ml). The ether phases were discarded and the filtered acid phases were extracted with chloroform (3 x 25ml). The combined extracts were dried (Na₂SO₄) and evaporated, leaving a solid (B; 0.448g). Solids A and B were combined, dissolved in ethyl acetate (80ml), and washed with 10% w/v aqueous potassium carbonate (2 x 25ml), saturated brine (2 x 25ml), dried (Na₂SO₄), and evaporated giving the title base as a gum which crystallised on trituration with ether (3.284g). This solid was redissolved in ethyl acetate (30ml) and treated with excess ethereal hydrogen chloride. A solid crystallised slowly. The supernatant was decanted and the solid was recrystallised from ethyl acetate-methanol giving the hydrochloride salt of the title compound (2.583g, mp. 190-190.5°. Found: C, 49.8; H, 4.4; N, 10.8; C₂₂H₂₁F₃N₄O₆.HCl requires C, 49.8; H, 4.2; N, 10.55%

Claims: Claims for the following Contracting States : BE, CH, LI, DE, FR, IT, LU, NL, SE Use of a compound of formula or a pharmaceutically salt thereof; wherein: α and β together represent a bond and additionally when B is an electron withdrawing group α can also represent -OH and β can represent hydrogen; Ar is a C₆-C₁₀ aryl or heteroaryl of 5 to 10 ring atoms, each group optionally substituted on carbon atoms by one or more substituents selected from halogen, C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ haloalkyl, C₁-C₆ haloalkoxy, NO₂, NH₂, CN, C₁-C₆ alkylamino, di(C₁-C₆)alkylamino, carboxy, C₂-C₇ alkoxycarbonyl, acyl, acylamino, aryl of 6 to 10 carbon atoms, heteroaryl of 5 to 10 ring atoms or C₁-C₆ aminoalkyl; R represents hydrogen or a C₁-C₆ alkyl group or benzyl group each optionally substituted by one or more substituents as defined above for Ar; R¹ and R² are the same or different and are selected from hydrogen, saturated C₅-C₇ cyclic aliphatic hydrocarbon residues unsaturated acyclic aliphatic hydrocarbon residues of up to 6 carbon atoms and saturated C₁-C₆ acyclic aliphatic hydrocarbon residues, said residues being optionally substituted by one or more group selected from halogen, OH, carboxy, CN, C₁-C₆ alkoxy, C₁-C₆ alkylthio, C₆-C₁₀ aryloxy, C₂-C₇ alkoxycarbonyl, amino, di(C₁-C₆)alkylamino and C₆-C₁₀ aryl or heteroaryl of 5-10 ring atoms, said aryl and heteroaryl groups being, optionally substituted by one or more substituents as defined above for Ar; A represents a group of formula -XR³ wherein X is a group of formula -(CHR⁶) p -Y-(CHR⁷) q - in which formulae: Y represents -O-, -S-, NR⁸ or a direct bond, p and q each represent 0, 1 or 2 providing that p and q do not both represent zero when Y is a direct bond; R⁶, R⁷ and R⁸ independently represent hydrogen or C₁-C₆ alkyl, and R³ is a mono- or bi-cyclic nitrogen ring heteroaryl radical of 5 to 10 rings atoms optionally containing other ring heteroatoms selected from oxygen, nitrogen and sulphur; said heteroaryl group being optionally substituted by one or more substituents as defined in connection with Ar; and B represents C₁-C₆ haloalkyl, CN, -CHO -CH(C₁-C₆alkoxy)₂, CH₂OH or phenyl optionally substituted as for Ar above, in the preparation of a medicament for inhibiting blood platelet aggregation or thromboxane synthetase in a mammal. A use according to Claim 1 in which the medicament is for the prevention of thrombosis. A use as claimed in Claim 1 or Claim 2 in which R³ is imidazolyl, pyridyl, thiazolyl, pyrrolyl, benzimidazolyl, quinolyl, isoquinolyl or imidazopyridyl. A use as claimed in Claim 1 or Claim 2 wherein X represents -NH-, -O-, -S-, -CH₂, -CH(CH₃), -CH(CH₃)CH₂-, -CH₂CH(CH₃)-, -OCH₂-, -CH₂O-, -(CH₂)₂-O-, or a group of formula -CH₂-Z-CH₂, -(CH₂)₂Z-CH₂ or CH₂-Z-(CH₂)₂- where Z is -S-, -NH- or a direct bond. A use as claimed in any one of claims 1 to 4 wherein Ar is optionally substituted phenyl, pyridyl, quinolyl or benzimidazolyl. A use as claimed in claim 5 wherein Ar is 2- or 3-nitrophenyl, 2,3-dichlorophenyl, 2-trifluoromethylphenyl, pentafluoromethyl, pentafluorophenyl, naphthyl, pyridyl or halopyridyl. A use as claimed in any one of Claims 1 to 6 wherein B is -CN, -CHO, -CH₂(OMe)₂ or a C₁-C₃ alkyl group substituted by one or more halogen atoms. A use as claimed in any one of Claims 1 to 7 wherein R is hydrogen, methyl, ethyl, n-propyl, isopropyl, benzyl, carbethoxymethyl or carbmethoxymethyl. A use as claimed in any one of Claims 1 to 8 wherein R¹ and/or R² is hydrogen, methyl, ethyl, n-propyl, isopropyl, butyl, methoxymethyl, ethoxymethyl, methoxy propyl, aminomethyl, 2-aminoethyl, 3-aminopropyl, dimethylaminoethyl, 2-carboxyethyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, pyridylmethyl, pyridylethyl, imidazolylmethyl or imidazolylethyl. A use as claimed in Claim 1 in which the compound of formula I is 2-trifluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid diethyl ester or a pharmaceutically acceptable salt thereof, or 2-fluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid-3-methyl 5-ethyl diester or a pharmaceutically acceptable salt thereof. A compound of formula I shown and defined in Claim 1 providing that (i) when Ar is phenyl optionally substituted by by one or more groups selected from halogen, CF₃ CN or NO₂, R is hydrogen or alkyl, R¹ and R² are the same or different alkyl, α and β are a bond, p is 1, q is O or 1 and R³ is a 5 or 6 membered unsaturated nitrogen ring heteroaryl optionally substituted by OH or NH₂ and optionally containing 1 or 2 additional nitrogen ring atoms, then B is other than fluoroalkyl; or (ii) when Ar is phenyl substituted by 3 or 4 substituents or Ar is a 5-membered substituted heteroaryl group in which the heteroatom is selected from oxygen, nitrogen and sulphur and α and β are a bond and B is CHO, haloalkyl or CH₂OH then R³ is other than imidazolyl substituted by three alkyl groups the same or different, or 2-amino-6-hydroxypyrimidinyl. A compound of formula I as defined in Claim 1 which is 2-trifluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicaboxylic acid or a pharmaceutically acceptable salt thereof or 2-fluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid-3-methyl 5-ethyl diester or a pharmaceutically acceptable salt thereof. A process for preparing a compound of formula I as claimed in Claim 11 which comprises one of the following: (i) reacting compounds of formulae II, III and IV: in which formulae Ar, R, R¹ and R² are as defined in Claim 11 and one of T¹ and T² is A, the other is B wherein A is as defined in Claim 11 and B is fluoroalkyl, -CN, -CHO, -CH₂OH, -CH(C₁-C₆ alkoxy)₂ providing that when Y is -O-, -S- or -NR⁸- then p is 1 or 2 to give a corresponding compound of formula I; or (ii) reacting a compound of formula (II) with a compound of formula (V) in which formulae Ar, R, R¹ and R² are as defined in Claim 11 and one of T¹ and T² is A, the other is B wherein A and B are as defined in Claim 11 providing that when Y is -O-, -S- or -NR⁸- then p is 1 or 2, to give a corresponding compound of formula I; or (iii) reacting a compound of formula ArCHO with compounds of formulae V and VI in which formulae Ar, R, R¹ and R² are as defined above and one of T¹ and T² is A, the other B wherein A and B are as defined in Claim 11 providing that when Y is -O-, -S- or -NR⁸- then p is 1 or 2, to give a corresponding compound of formula I, or (iv) reacting a compound of formula VII with a compound of formula VIII Z²(CHR⁷) w R³ (VIII) in which formulae α, β, R, R¹, R², R³, R⁶ and R⁷ are as defined in Claim 11; B is fluoroalkyl, CN, CHO, CH₂OH, CH(C₁-C₆alkoxy )₂ or optionally substituted phenyl; one of Z¹ and Z² is halogen (other than fluorine when B is fluoroalkyl) or a sulphonyloxy group, the other of Z¹ and Z² is -YH, -Y⁻ as appropriate wherein Y is as defined in Claim 11; and v and w are each independently 0, 1 or 2 with the proviso that when v is 2 and Z² is -YH or Y⁻ then Z¹ can also represent dialkylamino or a quaternary ammonium group, or (v) alkylating in the presence of a strong base a compound of formula I as defined in Claim 11 wherein R is hydrogen with an alkylating agent of formula R - Z³ where R is as defined in Claim 11 except hydrogen and Z³ is halogen or a sulphonyloxy group to give a corresponding compound of formula I, or (vi) dehydrating a compound of formula I wherein α and β represent OH and H respectively to give a corresponding compound of formula I wherein α and β together represent a bond, (vii) selectively reducing a compound of formula I wherein B is CHO to give a corresponding compound of formula I wherein B is -CH₂OH, (viii) reacting a compound of formula I wherein α and β together represent a bond and B is -CHO or -CH₂L where L is OH or a leaving group with a fluorinating agent to give a corresponding compound of formula I wherein B is -CH₂F or -CHF₂, (ix) hydrolysing a compound of formula I wherein B is CH(C₁-C₆alkoxy )₂ to give a compound of formula I wherein B is CHO, (x) removing the elements R¹⁰OH from a compound of formula wherein Ar, R, R¹, R², A, α and β are as defined in Claim 11 and OR¹⁰ represents hydroxy or a leaving group, or (xi) hydrolysing a compound of formula I as defined in Claim 11 having an ester group to give a compound of formula I having a carboxyl group, or (xii) esterifying a compound of formula I as defined in Claim 11 having a carboxy group to give a compound of formula I as defined in Claim 1 having an ester group, or (xiii) reacting a compound of formula I as defined in Claim 11 having a carboxyl group with a base to form a salt thereof or acidifying a salt carboxylate of a compound of formula I to give the free acid, or (xx) converting a compound of formula I as defined in Claim 11 to an acid addition salt thereof by addition of acid or basifying an acid addition salt to give a compound of formula I, or (xi) converting a compound of formula I as defined in Claim 11 having basic substituent to a quaternary ammonium salt thereof by reaction with an alkylating agent. A pharmaceutical composition comprising a compound of formula I or a pharmaceutically acceptable salt thereof as claimed in Claim 11 or Claim 12 and a pharmaceutically acceptable carrier. Claims for the following Contracting States : AT, GR, ES Use of a compound of formula or a pharmaceutically a salt thereof; wherein: α and β together represent a bond and additionally when B is an electron withdrawing group α can also represent -OH and β can represent hydrogen; Ar is a C₆-C₁₀ aryl or heteroaryl of 5 to 10 ring atoms, each group optionally substituted on carbon atoms by one or more substituents selected from halogen, C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ haloalkyl, C₁-C₆ haloalkoxy, NO₂, NH₂, CN, C₁-C₆ alkylamino, di(C₁-C₆)alkylamino, carboxy, C₂-C₇ alkoxycarbonyl, acyl, acylamino, aryl of 6 to 10 carbon atoms, heteroaryl of 5 to 10 ring atoms or C₁-C₆ aminoalkyl; R represents hydrogen or a C₁-C₆ alkyl group or benzyl group each optionally substituted by one or more substituents as defined above for Ar; R¹ and R² are the same or different and are selected from hydrogen, saturated C₅-C₇ cyclic aliphatic hydrocarbon residues unsaturated acyclic aliphatic hydrocarbon residues of up to 6 carbon atoms and saturated C₁-C₆ acyclic aliphatic hydrocarbon residues, said residues being optionally substituted by one or more group selected from halogen, OH, carboxy, CN, C₁-C₆ alkoxy, C₁-C₆ alkylthio, C₆-C₁₀ aryloxy, C₂-C₇ alkoxycarbonyl, amino, di(C₁-C₆)alkylamino and C₆-C₁₀ aryl or heteroaryl of 5-10 ring atoms, said aryl and heteroaryl groups being, optionally substituted by one or more substituents as defined above for Ar; A represents a group of formula -XR³ wherein X is a group of formula -(CHR⁶) p -Y-(CHR⁷) q - in which formulae: Y represents -O-, -S-, NR⁸ or a direct bond, p and q each represent 0, 1 or 2 providing that p and q do not both represent zero when Y is a direct bond; R⁶, R⁷ and R⁸ independently represent hydrogen or C₁-C₆ alkyl, and R³ is a mono- or bi-cyclic nitrogen ring heteroaryl radical of 5 to 10 rings atoms optionally containing other ring heteroatoms selected from oxygen, nitrogen and sulphur; said heteroaryl group being optionally substituted by one or more substituents as defined in connection with Ar; and B represents C₁-C₆ haloalkyl, CN, -CHO CH(C₁-C₆alkoxy)₂, CH₂OH or phenyl optionally substituted as for Ar above, in the preparation of a medicament for inhibiting blood platelet aggregatlon or thromboxane synthetase in a mammal. A use according to Claim 1 in which the medicament is for the prevention of thrombosis. A use as claimed in Claim 1 or Claim 2 in which R³ is imidazolyl, pyridyl, thiazolyl, pyrrolyl, benzimidazolyl, quinolyl, isoquinolyl or imidazopyridyl. A use as claimed in Claim 1 or Claim 2 wherein X represents -NH-, -O-, -S-, -CH₂, -CH(CH₃), -CH(CH₃)CH₂-, -CH₂CH(CH₃)-, -OCH₂-, -CH₂O-, -(CH₂)₂-O-, or a group of formula -CH₂-Z-CH₂, -(CH₂)₂Z-CH₂ or CH₂-Z-(CH₂)₂- where Z is -S-, -NH- or a direct bond. A use as claimed in any one of claims 1 to 4 wherein Ar is optionally substituted phenyl, pyridyl, quinolyl or benzimidazolyl. A use as claimed in claim 5 wherein Ar is 2- or 3-nitrophenyl, 2,3-dichlorophenyl, 2-trifluoromethylphenyl, pentafluoromethyl, pentafluorophenyl, naphthyl, pyridyl or halopyridyl. A use as claimed in any one of Claims 1 to 6 wherein B is -CN, -CHO, -CH₂(OMe)₂ or a C₁-C₃ alkyl group substituted by one or more halogen atoms. A use as claimed in any one of Claims 1 to 7 wherein R is hydrogen, methyl, ethyl, n-propyl, isopropyl, benzyl, carbethoxymethyl or carbmethoxymethyl. A use as claimed in any one of Claims 1 to 8 wherein R¹ and/or R² is hydrogen, methyl, ethyl, n-propyl, isopropyl, butyl, methoxymethyl, ethoxymethyl, methoxy propyl, aminomethyl, 2-aminoethyl, 3-aminopropyl, dimethylaminoethyl, 2-carboxyethyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, pyridylmethyl, pyridylethyl, imidazolylmethyl or imidazolylethyl. A use as claimed in Claim 1 in which the compound of formula I is 2-trifluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid diethyl ester or a pharmaceutically acceptable salt thereof, or 2-fluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid-3-methyl 5-ethyl diester or a pharmaceutically acceptable salt thereof. A process for preparing a compound of formula I shown and defined in Claim 1 providing that (i) when Ar is phenyl optionally substituted by by one or more groups selected from halogen, CF₃ CN or NO₂, R is hydrogen or alkyl, R¹ and R² are the same or different alkyl, α and β are a bond, p is 1, q is O or 1 and R³ is a 5 or 6 membered unsaturated nitrogen ring heteroaryl optionally substituted by OH or NH₂ and optionally containing 1 or 2 additional nitrogen ring atoms, then B is other than fluoroalkyl, or (ii) when Ar is phenyl substituted by 3 or 4 substituents or Ar is a 5-membered substituted heteroaryl group in which the heteroatom is selected from oxygen, nitrogen and sulphur and α and β are a bond and B is CHO, haloalkyl or CH₂OH then R³ is other than imidazolyl substituted by three alkyl groups the same or different, or 2-amino-6-hydroxypyrimidinyl. which comprises one of the following: (i) reacting compounds of formulae II, III and IV: in which formulae Ar, R, R¹ and R² are as defined in Claim 1 and one of T¹ and T² is A, the other is B wherein A is as defined in Claim 1 and B is fluoroalkyl, -CN, -CHO, -CH₂OH, -CH(C₁-C₆ alkoxy)₂ providing that when Y is -O-, -S- or -NR⁸- then p is 1 or 2 to give a corresponding compound of formula I; or (ii) reacting a compound of formula (II) with a compound of formula (V) in which formulae Ar, R, R¹ and R² are as defined in Claim 1 and one of T¹ and T² is A, the other is B wherein A and B are as defined in Claim 1 providing that when Y is -O-, -S- or -NR⁸- then p is 1 or 2, to give a corresponding compound of formula I; or (iii) reacting a compound of formula ArCHO with compounds of formulae V and VI in which formulae Ar, R, R¹ and R² are as defined above and one of T¹ and T² is A, the other B wherein A and B are as defined in Claim 1 providing that when Y is -O-, -S- or -NR⁸- then p is 1 or 2, to give a corresponding compound of formula I, or (iv) reacting a compound of formula VII with a compound of formula VIII Z²(CHR⁷) w R³ (VIII) in which formulae α, β, R, R¹, R², R³, R⁶ and R⁷ are as defined in Claim 1; B is fluoroalkyl, CN, CHO, CH₂OH, CH(C₁-C₆alkoxy )₂ or optionally substituted phenyl; one of Z¹ and Z² is halogen (other than fluorine when B is fluoroalkyl) or a sulphonyloxy group, the other of Z¹ and Z² is -YH, -Y⁻ as appropriate wherein Y is as defined in Claim 1; and v and w are each independently 0, 1 or 2 with the proviso that when v is 2 and Z² is -YH or Y⁻ then Z¹ can also represent dialkylamino or a quaternary ammonium group, or (v) alkylating in the presence of a strong base a compound of formula I as defined in Claim 1 wherein R is hydrogen with an alkylating agent of formula R - Z³ where R is as defined in Claim 1 except hydrogen and Z³ is halogen or a sulphonyloxy group to give a corresponding compound of formula I, or (vi) dehydrating a compound of formula I wherein α and β represent OH and H respectively to give a corresponding compound of formula I wherein α and β together represent a bond, (vii) selectively reducing a compound of formula I wherein B is CHO to give a corresponding compound of formula I wherein B is -CH₂OH, (viii) reacting a compound of formula I wherein α and β together represent a bond and B is -CHO or -CH₂L where L is OH or a leaving group with a fluorinating agent to give a corresponding compound of formula I wherein B is -CH₂F or -CHF₂, (ix) hydrolysing a compound of formula I wherein B is CH(C₁-C₆alkoxy )₂ to give a compound of formula I wherein B is CHO, (x) removing the elements R¹⁰OH from a compound of formula wherein Ar, R, R¹, R², A, α and β are as defined in Claim 1 and OR¹⁰ represents hydroxy or a leaving group, or (xi) hydrolysing a compound of formula I as defined in Claim 1 having an ester group to give a compound of formula I having a carboxyl group, or (xii) esterifying a compound of formula I as defined in Claim 1 having a carboxy group to give a compound of formula I as defined in Claim 1 having an ester group, or (xiii) reacting a compound of formula I as defined in Claim 1 having a carboxyl group with a base to form a salt thereof or acidifying a salt carboxylate of a compound of formula I to give the free acid, or (xx) converting a compound of formula I as defined in Claim 1 to an acid addition salt thereof by addition of acid or basifying an acid addition salt to give a compound of formula I, or (xi) converting a compound of formula I as defined in Claim 1 having basic substituent to a quaternary ammonium salt thereof by reaction with an alkylating agent. A process as claimed in Claim 1 in which the product is which is 2-trifluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(3-nitrophenyl)pyridine-3,5-dicaboxylic acid or a pharmaceutically acceptable salt thereof or 2-fluoromethyl-1,4-dihydro-6-(imidazol-1-ylmethyl)-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid-3-methyl 5-ethyl diester or a pharmaceutically acceptable salt thereof. A process for preparing a pharmaceutical composition which comprises bringing a compound of formula I or a pharmaceutically acceptable salt thereof as defined in Claim 11 or Claim 12 into association with a pharmaceutically acceptable carrier.

Inventors: ARCHIBALD JOHN LEHEUP, OPALKO ALBERT, WARD TERENCE JAMES, ARCHIBALD, JOHN LEHEUP, OPALKO, ALBERT, WARD, TERENCE JAMES
Applicants: WYETH JOHN & BROTHER LTD, JOHN WYETH & BROTHER LIMITED
Application year: 1987
Main classification: C07D401
IPC codes: C07D211, C12N9, C07D521, A61P9, C07D413, C07D401, A61K31, A61P7