Abstract:

Hydroboration of olefins is a concerted addition reaction involving only one step. It is generally considered to proceed via a four-center cyclic transition state. We performed theoretical studies on the reaction mechanism of the hydroboration of propene using quantum chemistry calculations, which led to a unique transition state that was inconsistent with the so-called four-center cyclic structure. In the computed transition state, the boron atom is bonded to both of the olefinic carbon atoms, and the degree of the hydrogen shift event is very low. All of these observations are consistent with those reported in the literature. Further theoretical studies revealed that the reaction might involve certain structures similar to the four-center cyclic structure, appearing as the transient states between the transition state and the product. Finally, the reaction mechanism of hydroboration was analyzed from the perspective of the orbital interaction model.

Key words: Hydroboration, Reaction mechanism, Transition state, Orbital interaction, Olefin