2-Chlorobenzaldehyde → Methyl 2-(2-chlorobenzylidene)-4,4-dimethoxy-3-oxovalerate

A mixture of 2-chlorobenzaldehyde (2.81 g), methyl 4,4-dimethoxy-3-oxovalerate (3.81 g) and piperidine (0.2 ml) in benzene (20 ml) was refluxed under azeotropic dehydration for 7.5 hours. A small amount of benzene was added to the reaction mixture and the resultant solution was washed with water and dried over magnesium sulfate. The solvent was removed from the solution to give a reddish oil (7.04 g) of methyl 2-(2-chlorobenzylidene)-4,4-dimethoxy-3-oxovalerate. The mixture of the oily product (6.39 g) obtained above and methyl 3-aminocrotonate (2.33 g) was heated at 132° C. for 3.5 hours, allowed to stand and then dissolved in ethyl acetate. The resultant solution was washed with water and an aqueous sodium chloride solution, and dried over magnesium sulfate. The solvent was removed from the solution under reduced pressure to give a viscous and brown oil (8.28 g). This oil was subjected to column chromatography on silica gel with an eluent (a mixture of 20 parts of benzene and one part of ethyl acetate by volume) to give an oily substance (5.26 g). This substance was dissolved in a mixture of ethyl acetate and diethyl ether and the solvent was removed under reduced pressure to give colorless powder (1.0625 g). This powder was recrystallized from a mixture of n-hexane and ethyl acetate to give faint yellow granules of dimethyl 2-methyl-4-(2-chlorophenyl)-6-(1,1-dimethoxyethyl)-1,4-dihydropyridine-3,5-dicarboxylate, m.p. 145° to 146° C.