Origin of the Anti-Markovnikov Hydroamination of Alkenes Catalyzed by L-Au(I) Complexes: Coordination Mode Determines Regioselectivity

The reaction mechanism and regioselectivity for the gold(I)-catalyzed hydroamination reaction of terminal alkenes are analyzed by means of density functional theory (DFT) calculations. The influence of the nature of the olefin as well as the ligand present in the gold(I) catalyst on the regioselectivity is investigated. The anti-Markovnikov addition is preferred for some alkenes, particularly those having cyclopropyl or good electron-withdrawing groups in their structures. The regioselectivity of the process is quantitatively analyzed with the help of state-of-the-art computational methods, namely, the activation strain model (ASM) of reactivity and natural orbitals for chemical valence (NOCV) method. It is found that the back-bonding interactions in the initially formed pi-complex are directly related to the Gibbs energy barrier difference between the Markonikov and anti-Markovnikov additions. It can be concluded that the coordination mode of the initial pi-complex ultimately controls the regioselectivity outcome of the transformation.