A choline chloride-based deep eutectic solvent promoted three-component synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-d] pyrimidinone (thione) derivatives

Abstract

An efficient one-pot method for the synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-d]pyrimidinone (thione) derivatives through a three-component reaction between aldehydes, malononitrile and enolizable C–H activated acidic compounds using a new deep eutectic solvent made of choline chloride, urea and thiourea as an environmentally benign catalyst has been reported. The structure of the catalyst was characterized using FT-IR, 1H NMR, and 13C NMR. The present method exhibits some notable advantages such as ease of the preparation and handling of the catalyst, low cost, green reaction conditions, short reaction times, high yields, and simple work-up. Also, the catalyst could be recovered easily and recycled up to four times without significant loss of catalytic activity.