Catalyst- and chromatography-free multi-component domino synthesis of 5-alkyl barbituric acids at room temperature

Abstract

5-Alkylated barbituric acids are an important class of compounds that constitute the basic moiety of several clinically used hypnotic drugs. Here we report a catalyst-free domino Knoevenagel-Michael addition involving barbituric acid, aldehyde, and N,N-disubstituted aniline in solvent acetonitrile to synthesize 5-alkylated barbituric acid derivatives (72–94% yield) without using any chromatographic separation techniques. The C-4 position of aniline acts as the Michael donor. All the reactions are successfully performed without catalysts, providing an environment-friendly and economical route for the synthesis. Moreover, catalyst-free reactions are less sensitive to air and moisture unlike many metal catalysts, with easy separation of products, and simple operating procedures as there is no need for catalyst weighing, recovery, and removal. A plausible mechanism is also proposed based on control experiments.