3-Nitrobenzaldehyde → Dimethyl 2-methyl-4-(3-nitrophenyl)-6-dimethoxymethyl-1,4-dihydropyridine-3,5-dicarboxylate

Participants

Reaction Steps

To a mixture of 3-nitrobenzaldehyde (7.56 g), methyl 4,4-dimethoxyactoacetate (9.69 g) and acetic acid (600 mg) in benzene (25 ml) was added portionwise each one fifth portion of piperidine (851 mg) in benzene (5 ml) for each 20 minutes interval and the mixture was heated to reflux for 4 hours under azeotropic dehydration. After cooling, the reaction mixture was diluted with benzene (50 ml), washed twice with diluted aqueous sodium bicarbonate solution, and in turn, with water and saturated aqueous solution of sodium chloride, dried over magnesium sulfate and evaporated to dryness under reduced pressure to give crude reddish brown oily methyl (3-nitrobenzylidene)-4,4-dimethylacetoacetate (17.82 g) which was used in the following reaction without any further purification. A mixture of above oil (17.82 g) and methyl 3-aminocrotonate (6.33 g) was heated at 60° to 65° C. for 4.5 hours, at 100° to 105° C. for 8 hours and 45 minutes. The reaction mixture was chroatographed on a column of silica-gel (440 g) and eluted with a mixture of benzene and ethyl acetate (10:1, v/v) to give crystalline product (10.46 g) of dimethyl 2-methyl-4-(3-nitrophenyl)-6-dimethoxymethyl-1,4-dihydropyridine-3,5-dicarboxylate. Thus obtained crystals (720 mg) were recrystallized from diisopropyl ether (10 ml) to give pure specimen (560 mg), mp 99° to 100° C.

Provenance & Evidence