Free-ZnO nanoparticles: a mild, efficient and reusable catalyst for the one-pot multicomponent synthesis of tetrahydrobenzo[b]pyran and dihydropyrimidone derivatives

Free-ZnO nanoparticles have been employed as a mild, efficient and reusable catalyst for the one-pot multicomponent synthesis of tetrahydrobenzo[b]pyrans and dihydropyrimidones in excellent yields. The ZnO NPs were recycled and reused eight times.