Efficient and Facial Synthesis of Tetrahydrobenzo[b]pyrans using Sodium Cyclamate as a Green Catalyst

Since its discovery in 1996 by Strecker, multicomponent reactions (MCRs) have been recognizedas a powerful tool in synthetic chemistry to enable expedient access to various heterocyclesand bioactive compounds. Since then, significant efforts have been devoted to expandingscope of the MCRs and achieving a number of molecules using various catalysts including,organocatalysts, natural catalysts, nanocatalysts, acidic organic and inorganic reagents,and ionic liquids [1]. Tetrahydrobenzo[b]pyrans as fused pyran scaffolds constitute an importantclass of heterocycles represent a drug-like structural motif with a wide range of applicationsin organic synthesis and medicinal chemistry. They display a wide range of biologicaland pharmaceutical activities. The MCRs of dimedone, aldehydes, and malononitrile towardthe synthesis of tetrahydrobenzo[b]pyrans is catalyzed by a wide variety of catalysts,such as nanoparticles, Lewis acids, ionic liquids, and organocatalysts [1-3]. Herein, we reportsodium cyclamate as a new organocatalyst for the synthesis of tetrahydrobenzo[b]pyrans inaqueous media under reflux conditions. Under the optimized conditions, various aldehydes,malononitrile, and dimedone substrates are able to provide good to high yields of the desiredheterocyclic products. The structures of synthesized compounds were confirmed by IR, NMRspectroscopy, and melting point data.