Abstract
ABSTRACTWe 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 (HClO4–SiO2) 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.
Highlights
Among the solid-supported catalytic systems, perchloric acid adsorbed on silica gel (HClO4–SiO2) is found in various organic functional group transformations and in the synthesis of many bioactive heterocycles [5-15]
Knoevenagel condensation reactions have been employed as convenient methods of synthesis of coumarin derivatives [21-23]
Development of versatile, simple, and environmentally friendly processes for the synthesis of these compounds. These reports prompted us to study the catalytic role of HClO4–SiO2 in our present investigations, in the synthesis of coumarins and dihydropyrimidines
Summary
Solid-supported catalysts have been increasingly attracting synthetic chemists as unique acid catalysts in terms of green chemical methodologies over the last two decades [1,2]. Among the solid-supported catalytic systems, perchloric acid adsorbed on silica gel (HClO4–SiO2) is found in various organic functional group transformations and in the synthesis of many bioactive heterocycles [5-15].
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