Theoretical Mechanism For Selective Catalysis Of Ruthenium Complex Catalyzed Hydroboration Of Terminal Alkynes To Z-Vinylboronates

Detailed mechanism of the hydroboration of terminal alkynes catalyzed by ruthenium complex was studied using density functional theory. The calculated results suggest that the reaction proceeds in two steps: alkyne rearrangement and catalyst regeneration. Vinylboronate products with E and Z configuration are formed in this reaction. Path A forming Z-vinylboronate is the preferred pathway. Noncovalent interaction between BH bond and Ru centre determines the preferred pathway of the reaction. The E-gap of HOMO-LUMO for the reactant is lowered with the assistance of ruthenium-borane complex (Ru-Cat) formation. A hypothetical control model using 1, 2-dimethyl acetylene (internal alkyne) and styrene (terminal alkene) as the reaction substrates was designed. The calculated results suggest that the activation barrier of the rate-determining process is too high, which make the hydroboration reaction of styrene and 1, 2-dimethyl acetylene (CH3C-CCH3) hard to occur. The results uncover the selectivity of the ruthenium complex for hydroboration of terminal alkynes. (c) 2014 Wiley Periodicals, Inc.