Mechanism of Dehydrogenative Condensation of (<i>o</i>-borylphenyl)hydrosilanes with Methanol

The dehydrogenative condensation of hydrosilanes and alcohols is a facile way of protecting alcohols in chemical synthesis. Recently, Kawachi and co-workers combined the B­(C₆F₅)₃ catalyst and the hydrosilyl group in one molecule, enabling the coupling reaction to take place at room temperature without additional catalyst. In this paper, the mechanism of the reaction of this novel protecting group with methanol is explored using computational techniques. A stepwise reaction pathway was found to be preferred to the concerted one. The mechanism can be interpreted using the FLP framework. In the preferred pathway, the activation of the Si–H and O–H bonds happens simultaneously. While the hydride-like hydrogen on the Si atom is activated by the Lewis acidic boron site, the O–H bond is activated by the π-system of one of the mesityl substituents on the boron atom. Further calculations show that, by changing the acidity of the Lewis acidic site, the activation barrier of the reaction can be tuned