Silica-Immobilized NHC-Gold(I) Complexes: Versatile Catalysts for the Functionalization of Alkynes under Batch and Continuous Flow Conditions

Abstract

Immobilized sterically demanding NHC-Au(I) complexes silica-[(IPrR)Au]Cl and silica-[(IAdPrR)Au]Cl are synthesized and characterized. These complexes are suitable catalysts in typical homogeneous Au(I)-catalyzed alkyne reactions such as hydration, hydroamination, hydroarylation, or cycloisomerization. The results obtained with the immobilized catalysts in reactions in batch are comparable to those obtained with their homogeneous counterparts with the advantage of easily recovered and recycled in successive reactions. Their catalytic activity decreases when reused in batch reactions, probably because of crushing that is associated with magnetic stirring. In contrast, these immobilized catalysts are very effective when used under continuous flow conditions in which the same cartridge can be used to catalyze different types of reaction successively for a long period without any noticeable loss of activity.