Hydroxy sodalite zeolite as a recyclable catalyst for the green synthesis of tetrahydrobenzo[b]pyrans via one-pot three-component condensation reaction

The utilization of hydroxy sodalite (H-SOD) as catalyst under solvent-free condition is described for the efficient preparation of tetrahydrobenzo[b]pyrans. These compounds are synthesized by three-component reactions of aldehydes, alkylnitriles and dimedone. H-SOD that is the waste-product of zeolite manufacturing process is used as an efficient and a very inexpensive catalyst. Furthermore, it can be reused for several rounds without significant loss of activity. The key features of this reported protocol are neutral conditions, excellent yields, short reaction time, simple work-up and recovery and reusability of catalyst. Small E-factor and large percent of reaction mass efficiency, which are very useful metrics for industry, are advantages of this environmentally benign process.