PROCESS FOR THE PREPARATION OF ASYMMETRICAL 1,4-DIHYDRO-PYRIDINE-DICARBOXYLIC ACID ESTERS

摘要

The invention relates to an improved process for the preparation of asymmetrical 1,4-dihydro-pyridine-dicarboxylic acid esters of general Formula (I) (wherein R<1> and R<2> each stands for lower alkyl or an ethyl group substituted by methosy or cyano, with the proviso that R<1> and R<2> are different; R3 stands for lower alkyl optionally substituted by hydroxy or halogen, or a benzyloxymethyl group or a group of the general Formula -CH2-O-CH2-CH2-X; X stands for halogen, azido or -NR<4>R<5>; R<4> and R<5> are identical or different and each stands for hydrogen or lower alkyl, or R<4> and R<5> together with the nitrogen atom, they are attached to, form a phthaloyl group; A is nitro or halogen and n is 1 or 2).