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We are reporting a simple, efficient and green protocol for the synthesis of chromenes and dihydropyrimidines (products of Knoevenagel and Biginelli reaction, respectively) by the use of silica-supported perchloric acid (HClO 4-SiO 2) as an effective heterogeneous catalyst. Short reaction times, high product yields, simple procedure and reusability of the catalyst are the superior characteristics of this protocol.

In the last decade, silica-supported heterogeneous catalysts have emerged as efficient green catalysts for the development of synthetic protocols of bioactive heterocycles. These catalysts possess better significant features when compared with the activities of homogeneous catalysts. Azoles are five-membered nitrogen-containing heterocyclic compounds that possess a wide range of medicinal properties. In this review, a summary of the recent progress on silica-supported heterogeneous catalyzed synthetic methods of azoles and related five-membered heterocycles is presented.

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Synthetic application of Silica–ZnCl2 , as an efficient and eco‐friendly catalyst for the synthesis of a small library of dihydropyrimidinones is described in this report. The reaction involves a one pot, multicomponent reaction of β‐oxodithiocarboxylates, aldehydes, and urea under solvent‐free conditions. The experimental procedure is simple, environmental benign, tolerated with many functional groups, and results in good to excellent yield of the products.

An eco‐friendly method is developed for preparation of the title compounds by one‐pot three‐component reaction of β‐oxodithiocarboxylates, benzaldehydes, and urea.