Cationic silicon Lewis acids in catalysis

Abstract

Silylium ions, or, to be more precise, donor-stabilized silylium-ion-like species, were once only the domain of computational and structural chemists. This was mainly due to the difficulties in generating and isolating these reactive species in a condensed phase. Even chemists focused on reactivity stayed away from such delicate ions. The state of affairs has changed in recent years as methods for their preparation have become more accessible and strategies for their stabilization more effective. Silylium ions have high electrophilicity, oxophilicity and fluorophilicity that have seen them emerge as useful catalysts, including for unique transformations not accessible to metal catalysts. This Perspective aims to provide a concise and conceptual summary of breakthroughs in this emerging area. Silylium ions are highly reactive, strongly Lewis acidic and have historically been tricky to isolate. This Perspective highlights the range of methods available for their preparation and the latest examples of their use as catalysts or reagents in organic synthesis.