Silylation of Allylic C(sp3)–H Bonds Enabled by the Catalytic Generation of Allylpotassium Complexes

Allylsilanes have long been recognized as key molecular building blocks in organic synthesis that are routinely employed as nucleophilic allylating reagents. Although a great deal of catalytic and stoichiometric synthetic strategies are available to prepare such allylsilanes from prefunctionalized substrates, the use of stable and widely available alkenes as their direct precursors remains underdeveloped. In particular, a nonoxidative catalytic silylation protocol operating through the direct activation of allylic C­(sp3)–H bonds of alkenes has yet to be reported. Herein, we describe a general protocol for the silylation of allylic C­(sp3)–H bonds under ambient, transition metal-free conditions using stable tert-butyl-substituted silyldiazenes (tBu–NN–SiR3) as a silicon source. We demonstrate that a range of 1-alkenes readily afford the corresponding allylsilanes with nearly complete linear selectivity. A reactivity model that involves experimentally characterized η3-allylpotassium intermediates is also proposed to account for the thermodynamically controlled stereoselectivity of the reaction.