Organopotassium-Catalyzed Silylation of Benzylic C(sp3)-H Bonds

Benzylsilanes have found increasing applications in organic synthesis as bench-stable synthetic intermediates, yet are mostly produced by stoichiometric procedures. Catalytic alternatives based on the atom-economical silylation of benzylic C(sp(3))-H bonds remain scarcely available as specialized directing groups and catalytic systems are needed to outcompete the kinetically-favored silylation of C(sp(2))-H bonds. Herein, we describe the first general and catalytic-in-metal undirected silylation of benzylic C(sp(3))-H bonds under ambient, transition metal-free conditions using stable tert-butyl-substituted silyldiazenes (tBu-N=N-SiR3) as silicon source. The high activity and selectivity of the catalytic system, exemplified by the preparation of various mono- or gem-bis benzyl(di)silanes, originates from the facile generation of organopotassium reagents, including tert-butylpotassium.

Automated summary

Benzylsilanes are widely used as stable synthetic intermediates in organic synthesis, but are mainly produced by stoichiometric procedures. Catalytic alternatives for silylation of benzylic C(sp(3))-H bonds are scarce due to the need for specialized directing groups and catalytic systems to compete with the kinetically-favored silylation of C(sp(2))-H bonds. In this study, we report the first general and catalytic-in-metal undirected silylation of benzylic C(sp(3))-H bonds under ambient, transition metal-free conditions using stable tert-butyl-substituted silyldiazenes (tBu-N=N-SiR3) as silicon source. The high activity and selectivity of the catalytic system is attributed to the facile generation of organopotassium reagents, including tert-butylpotassium.