PROCESS FOR PREPARING DIHYDROPYRIDINE DERIVATIVES

The invention relates to a process for the preparation of dimethyl-1,4-dihydro-2,6-dimethyl-4-(2'-nitro- -phenyl)-pyridine-3,5-dicarboxylate of the Formula I (see fig. I) wich comprises a) reacting a compound of the general Formula II (see fig. II) (wherein n is 1 or 3; if n is 1, then R stands for a group of the Formula (a) or (b) and if n is 3, then R represents hydrogen) with methyl acetoacetate of the Formula III CH3-CO-CH2-COOCH3 (III) and optionally with an amino compound of the general Formula IV (wherein Z is a group of the Formula (c), k is 1 and both symbols p are 0; or Z stands for a C1-5 straight or branched chain alkanoyloxy group or a carbonate, hydrocarbonate or hydroxy anion, k is 1 and both symbols p are 1; or k is 0, one of both symbols p is 0 and the other is 1) in an inert solvent; or b) reacting 2-nitro-benzaldehyde and methyl aceto-acetate of the Formula III and aqueous ammonium hydroxide in the presence of an inert solvent in one step, at a temperature of 101-120 .degree.C, under a pressure of 2.0 - 6.0 bar. The dimethyl-1,4-dihydro-2,6-dimethyl-4-(2'-nitro- -phenyl)-pyridine-3,5-dicarboxylate of the Formula I is a known calcium antagonist useful in the treatment of hypertension. The process of the present invention is suitable for industrial scale manufacture and provides highly pure product with excellent yields. The reaction time is shorter than in case of the known methods and the more expensive starting materials are partially or completely replaced by cheaper components.