Tertiary C(sp3)–Si Bond Formation via Reactivity Umpolung of Silyl Reagents

A transition-metal-free decyanative silylation of malononitriles with silyl chlorides enabled by a silyl umpolung strategy is described. This reaction involves NaOtBu-promoted silylboranes addition to malononitriles to generate electrophilic silyl cyanide and nucleophilic ketenimine intermediates in situ, which recombine to form sterically congested C­(sp3)–Si bonds. This method expands silylborane reactivity and provides a general route to alkylsilanes.