Ultrasonication-assisted, multicomponent, green and sustainable synthesis of benzopyrans employing taurine as a bioorganic catalyst

Abstract

Benzopyrans, an important class of fused O-heterocycles, have natural abundance with a broad range of bioactivities. Herein, we report the ultrasonication-assisted, taurine-catalyzed, one-pot, multicomponent, green and sustainable synthesis of diversely functionalized fused benzopyrans at room temperature within a short reaction time. The key reactions include a cascade of Knoevenagel-type condensation and Michael addition, followed by the spontaneous intramolecular 6-exo-trig cyclization of dimedone and salicylaldehydes, affording an array of diversely functionalized fused benzopyrans in excellent yields. The presented protocol meets the criteria of green and sustainable chemistry, and the notable advantages of the presented method include the employment of taurine, a green, nontoxic, inexpensive, and environmentally benign bioorganic catalyst; ultrasonication assisted, one-pot, multicomponent reaction; easy product isolation via filtration; gram-scale synthesis; as well as the recyclability and reusability of the catalyst for up to six consecutive runs without significant loss of its catalytic activity and yield.