PROCESS FOR THE PREPARATION OF SYMMETRIC 1,4-DIHYDROPYRIDINE-CARBOXYLIC ESTERS

摘要

1. Processs for the preparation of symmetrical 1,4-dihydropyridines of the formula I see diagramm : EP0124742,P6,F1 in which R represents a phenyl radical which is optionally mono- or disubstituted by nitro and/or chlorine, and R1 represents a C1 -C4 -alkyl radical which is optionally substituted by a C1 -C4 -alkoxy group, by reaction of an ylidene compound of the formula II see diagramm : EP0124742,P6,F2 with an enamine compound of the formula III see diagramm : EP0124742,P6,F3 characterized in that the ylidene compound of the formula II is prepared by reaction of a ketocarboxylic ester of the formula IV see diagramm : EP0124742,P6,F4 with an aldehyde of the formula RCHO in a solvent, in the presence of catalytic amounts of piperidine acetate, at temperatures from - 10 degrees C and up to 100 degrees C.