Mechanistic Analysis of Gold(I) Catalysis through Generation and Direct Observation of Reactive Intermediate Analogues

Abstract

Cationic gold carbene complexes have attracted significant attention, being postulated as intermediates in a range of gold-catalyzed transformations. Regardless of the remarkable progress in the gold (I) catalysis, our fundamental understanding on the key intermediate species and the subsequent reactivity, and mechanistic insight is deficient. This is mainly due to the lack of proper model system with sufficient reactivity, as the majority of known gold carbene complexes are heteroatom stabilized or sterically hindered, and because of a dearth of direct intermediate observations in catalytic systems. Lewis acid mediated leaving group abstraction from a neutral gold precursor provides a convenient method for the generation of rare examples of reactive gold carbene species in high yield and purity, addressing the issue with isolation of such transient species as well as allowing in situ spectroscopic analysis. Subsequent trapping experiment with nucleophiles provides kinetic information about relevant catalytic transformations, and the -ionization strategy is further extended toward generation of transient  -cationic propyl gold species for studying gold to alkene carbene transfer reaction.