A Simple and Environmentally Benign Protocol for Biginelli Reactions Catalyzed by Silica-Bonded S-Sulfonic Acid

Abstract

A protocol for the synthesis of 3,4-dihydropyrimidin-2(1 H )-ones and -thiones was developed by means of a three-component condensation of an aldehyde, a β-dicarbonyl compound, and urea or thiourea in acetic acid catalyzed by silica-bonded S -sulfonic acid. Compared to the classical Biginelli reaction conditions, this new protocol has the advantages of consistently excellent yields and short reaction times. After the reaction, the catalyst could be recovered easily and reused with little change in its activity. We report a simple, efficient protocol for the synthesis of 3,4-dihydropyrimidin-2(1 H )-ones and -thiones by means of a three-component condensation of an aldehyde, a β-dicarbonyl compound, and urea or thiourea in acetic acid catalyzed by silica-bonded S -sulfonic acid (SBSSA), a green, reusable heterogeneous catalyst.