Acetic Acid → Methyl 2-(2-nitrobenzylidene)-4,4-dimethoxyacetoacetate

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Reaction Steps

To a solution of 2-nitrobenzaldehyde (6.80 g), methyl 4,4-dimethoxyacetoacetate (8.72 g) and acetic acid (0.54 g) in benzene (30 ml), was added piperidine (0.46 g), in a similar manner to aforementioned examples 1-i) and 2-i), and the mixture was heated to reflux for 2 hours under azeotropic dehydration. The reaction mixture, after cooling, was diluted with benzene (100 ml), washed three times with water, and in turn with diluted aqueous sodium bicarbonate solution and water, dried over magnesium sulfated and evaporated to dryness under reduce pressure to give oily methyl 2-(2-nitrobenzylidene)-4,4-dimethoxyacetoacetate (14.73 g). A mixture of the above obtained oil (14.70 g) and isopropyl 3-aminocrotonate (7.09 g) was heated at 60° to 63° C. for 2 hours and at 85° to 90° C. for about 10 hours. The reaction mixture was treated with ethyl acetate to give yellowish crystals which were collected by filtration and washed with methanol. The filtrate was concentrated and the residue was treated with methanol to give additional crystals. The combined crystals (11.10 g) were recrystallized from methanol to give pure crystals of isopropyl 2-methyl-4-(2-nitrophenyl)-5-methoxycarbonyl-6-dimethoxymethyl-1,4-dihydropyridine-3-carboxylate, m.p. 143°-145° C.

Provenance & Evidence