An Yb(OTf)₃‐catalyzed, convergent synthesis of new pyranyl‐ and chromenyl‐substituted quinolines through an eco‐friendly approach

Abstract

A one‐pot, multicomponent, convergent microwave synthesis of some new pyranyl‐ and chromenyl‐substituted quinolines has been reported. Twenty compounds were prepared by the reaction of 2‐methoxy‐3‐formyl quinoline (1a‐d), malononitrile (2), and kojic acid (4a‐d)/1,3‐cyclohexadione or dimedone (6a‐h)/α‐ or β‐naphthol (8a‐d, 8e‐h). The structures were confirmed by infrared (IR), 1H nuclear magnetic resonance (NMR), 13C NMR, mass, and single‐crystal X‐ray analyses. On comparison with the use of conventional Lewis acid catalysts and various metal triflates under microwave conditions, the latter contributed to good yields, in specific use of the recyclable Yb(OTf)3 catalyst attributed to high yields of the desired product. The protocol reported herein is solvent free, cost effective, and eco‐friendly.