Chiral Pyrrolidine Bridged Polyhedral Oligomeric Silsesquioxanes as Heterogeneous Catalysts for Asymmetric Michael Additions

Abstract

A chiral pyrrolidine bridged polyhedral oligomeric silsesquioxane (SQ) was synthesized, characterized, and used as an effective heterogeneous catalyst. The synthesis involves two simple steps: nucleophilic substitution between benzylchloride functionalized SQ and imidazoyl pyrrolidine carboxylate and subsequent deprotection. The catalyst was isolated by simple filtration. The SQ-supported chiral pyrrolidine catalyst was used as a heterogeneous catalyst in an asymmetric Michael addition into nitrostyrenes under room temperature and neat condition, giving the product in excellent yields (85–91%), diastereoselectivities (up to 99:1) and enantioselectivities (95–98%). The catalyst can be recycled by a simple filtration without a significant loss in its reactivity and selectivity.