On the Accessible Reaction Channels of Vinyl Gold(I) Species: Pi- and sigma-Pathways

The potential of vinyl Au species to react either through a controlled pi- or sigma-pathway is demonstrated. This nomenclature is directly derived from the orbitals of the vinyl Au species leading to the newly formed bonds. When the pi-bond of the vinyl Au intermediate is transformed into a sigma-bond, we name it pi-pathway, and a sigma- to sigma- transformation is named s- pathway. Examples of reactions following these pathways are a Au-catalysed [3,3]-sigmatropic rearrangement and a protodeauration reaction. These reactions have been studied using intrinsic bond orbitals (IBOs) and allow for the clear identification of these pathways. Energies for the reaction path of the Au-catalysed [3,3]-sigmatropic rearrangement were in addition computed using CCSD(T)-F12. Analysis of the intrinsic reaction coordinate (IRC) of the [3,3]-sigmatropic rearrangement using IBOs further allows us to refine the previous mechanistic proposal and identifies a hidden intermediate along the reaction path.