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

摘要

The 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.