Insights into the mechanism and origin of solvent-controlled chemodivergence in the synthesis of Au-catalyzed bicyclo[2.2.1]heptanes from 3-alkoxy-1,6-diynes: a DFT perspective

Abstract

Density functional theory (DFT) calculations reveal a distinct mechanism for the Au(I)-catalyzed synthesis of bicyclo-[2.2.1]heptanes through cycloisomerizations of 3-alkoxyl-1,6-diynes. The proposed mechanism highlights the crucial involvement of an allyl-gold species and rationalizes all experimental observations, including the solvent-controlled chemodivergence of the reaction. Specifically, in the less polar toluene solvent, the reaction involves a key allyl-gold species with an energy barrier of 24.1 kcal mol⁻¹, leading to the bridged ring product. Conversely, in the polar 1,2-dichloroethane solvent, the reaction occurs via an alkyl-gold species with an energy barrier of 29.2 kcal mol⁻¹, delivering the monocyclic product. This new reactivity concept could potentially assist the exploration of new and unconventional strategies for the preparation of bridged ring systems.