Strong Influence of the Nucleophile on the Rate and Selectivity of 1,2-Epoxyoctane Ring-Opening Catalyzed by Tris(pentafluorophenyl)borane, B(C6F5)3

Density functional theory (DFT) calculations, experimental data, and microkinetic modeling are used to extend a triple-pathway (Lewis acid, water-mediated, and alcohol-mediated) mechanism for tris(pentafluorophenyl)borane-catalyzed ring opening of 1,2-epoxyoctane by alkyl alcohol nucleophiles previously applied to 2-propanol to 1-propanol. Although simpler models may capture overall rates, the reaction schemes proposed here are required to explain the increasing regioselectivity to the primary product with conversion and the dependence of the overall regioselectivity on residual water concentration and additives as a function of reaction conditions. The model indicates that the different reaction conditions (nucleophile, water concentration, temperature, and conversion) lead to different amounts of flux through alcohol-mediated pathways, different speciation of tris(pentafluorophenyl)borane adducts, and differences among the inherent selectivities of water-mediated mechanisms.