Mechanism of Silylation of Vinyl Arenes by Hydrodisiloxanes Driven by Stoichiometric Amounts of Sodium Triethylborohydride-A Combined DFT and Experimental Study

The reactions of vinyl arenes with hydrodisiloxanes in the presence of sodium triethylborohydride were studied using experimental and computational methods. The expected hydrosilylation products were not detected because triethylborohydrides did not exhibit the catalytic activity observed in previous studies; instead, the product of formal silylation with dimethylsilane was identified, and triethylborohydride was consumed in stoichiometric amounts. In this article, the mechanism of the reaction is described in detail, with due consideration given to the conformational freedom of important intermediates and the two-dimensional curvature of the potential energy hypersurface cross sections. A simple way to reestablish the catalytic character of the transformation was identified and explained with reference to its mechanism. The reaction presented here is an example of the application of a simple transition-metal-free catalyst in the synthesis of silylation products, with flammable gaseous reagents replaced by a more convenient silane surrogate.

Automated summary

The reactions of vinyl arenes with hydrodisiloxanes in the presence of sodium triethylborohydride were studied. The catalytic activity of triethylborohydrides observed in previous studies was not detected, and instead, the product of formal silylation with dimethylsilane was identified. The reaction mechanism, including the conformational freedom of intermediates and the potential energy hypersurface cross sections, was described in detail, and a simple way to restore the catalytic character of the transformation was identified and explained. This study demonstrates the application of a transition-metal-free catalyst in the synthesis of silylation products, replacing flammable gaseous reagents with a more convenient silane surrogate.