Mechanistic Investigations of Gold(I) Catalyzed Hydrofunctionalizations of C-C Multiple Bonds

1243 FFSCThe mechanisms of gold catalyzed pi activation catalysis were investigated in two parts. (1) The kinetics and stereochemistry of the hydroamination of 1-aryl-1,2-butdienes with aniline catalyzed by gold(I) have been investigated. The rate of hydroamination displayed first-order dependence on [Au] and [allene] but zero-order dependence on aniline. The kinetics and stereochemistry of hydroamination are consistent with a mechanism involving the displacement of aniline from {(L)Au[aniline]}+ with allene to form {(L)Au[allene]}+ complex followed by outer sphere nucleophilic attack of the pi-allene complex with aniline to form a vinyl gold complex which undergoes protodeauration with retention of configuration. Importantly, ligand exchange and nucleophilic attack were found to occur at competitive rates, and the turnover limiting step depended on the electron density of the allene. (2) Hydride abstraction from a gold cylcoheptatriene complex and a gold (disilyl)ethylacetylide complex lead to the formation of a gold cycloheptatrienylidene complex and a gold (disilyl)vinylidene complex respectively. Both complexes are among the first non pi conjugated heteroatom stabilized gold carbenes and the gold (disilyl)vinylidene is the first gold(I) vinylidene complex reported. Both complexes were fully characterized in solution by multinuclear NMR spectroscopy, and the gold cycloheptatrienylidene complex was characterized in the solid state by single crystal X-ray diffraction.