Heterogeneous Copper‐Catalyzed Cascade Three‐Component Reaction Towards Imidazo[1,2‐a]pyridines: Efficient and Practical One‐Pot Synthesis of Alpidem

Abstract

AbstractThe heterogeneous cascade three‐component reaction of 2‐aminopyridines, aldehydes and terminal alkynes was achieved in toluene at 120 °C in the presence of 3‐(2‐aminoethylamino)propyl‐functionalized MCM‐41‐immobilized copper(I) complex [MCM‐41‐2 N‐CuCl] (5 mol%) and copper(II) complex [MCM‐41‐2N−Cu(OTf)2] (5 mol%), yielding a wide variety of imidazo[1,2‐a]pyridines in mostly good to excellent yields. These two heterogeneous copper catalysts can be facilely prepared via a simple procedure from readily available and inexpensive reagents, and recovered by filtration and recycled up to eight times with almost consistent activity.