Employing a hydrophobic-bentonite as a highly efficient and versatile catalyst for a green one-pot and rapid synthesis of 4H-benzo-[b]-pyran derivatives

A hydrophobic-bentonite catalyst (cetyltrimethyl ammonium bromide-bentonite) has been used as a very mild, neutral, eco-friendly, reusable, non-toxic, low-cost and easily available catalyst. It was prepared by replacing the exchangeable Na+ cations of a homoionic Na–bentonite with cetyltrimethyl ammonium bromide (CTMAB) cations. The catalyst was characterized by XRD, BET and SEM. The BET data and XRD patterns showed that the surfactant ions enter the interlayer space of catalyst. In order to study the catalytic properties, we carried out a one-pot practical, efficient and green multicomponent synthesis of 4H-benzo-[b]-pyran derivatives in terms of high yield, simple experimental procedure, low reaction time and simple work-up.