Acetoacetic Acid → 2,6-Dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid

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Reaction Steps

In 400 ml of benzene there are dissolved 100 g of menthol, added with 1 ml triethylamine, at refluxing and stirring for one hour there are added 55 ml of diketene and benzene is distilled-off under a reduced pressure (150 mm Hg). The remaining oily product consisting mainly of methyl ether of acetoacetic acid is dissolved in 400 ml of ethanol, added with 28 g of hexamethylenetetramine and 5 g of ammonium acetate and the reaction mixture is boiled on a water bath for 30 minutes. After cooling, the precipitated yellow substance is filtered-off and recrystallized from ethanol. There are obtained 105 g (69% of the theoretical value) of menthyl ester of 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid in the form of a bright-yellow crystalline substance having its melting temperature of from 180°-182° C.

Provenance & Evidence