Green Synthesis of 1,4‐Dihydropyridine Derivative in Water

A simple and environmentally clean synthesis of 4‐methoxycarbonylmethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylic acid dimethyl ester was achieved by heating methyl propiolate with an amine salt in water. Excess amine salt accelerated the reaction in the case of aliphatic amines, while stoichiometric amounts of propiolate ester and amine salt resulted in low yield. In the case of aniline, a 1:3 ratio of amine salt and methyl propiolate afforded 77% yield in 24 h. The free amine is proposed to serve as nucleophile for Michael addition reaction, and the liberated proton acts as an electrophilic catalyst. A simple and environmentally clean synthesis of 4‐methoxycarbonylmethyl −1,4‐dihydropyridine‐3,5‐dicarboxylic acid dimethyl ester was achieved by heating methyl propiolate with an amine salt in water without any other reagents. The free amine is proposed to serve as nucleophile for Michael addition reaction, and the liberated proton acts as an electrophilic catalyst.