Photoredox/nickel cooperatively catalyzed radical allylic silylation of allyl acetates – Scope and mechanism

Abstract

The compatibility between photogenerated silyl radicals and transition metal catalysis remains one of the foremost challenges in modern synthetic organic chemistry. Herein, we present the cooperation of photoredox/nickel catalyzed allylic silylation of diverse allyl acetates (even with multiple alkenyl groups) via a silyl radical intermediate. This protocol successfully surmounts the long-standing challenge and provides straightforward, modular synthetic access to substituted allylsilanes from silanecarboxylic acids. Moreover, this strategy has advantages of green and mild conditions over established nucleophilic substitution methods via a silanion pathway. Mechanistic study shows that the formation of silyl radical initiated by photo-induced decarboxylation of silanecarboxylic acids, and the nickel-catalyzed oxidative addition of allyl acetate, followed by silyl radical addition are critical processes. DFT computation reveals that the regioselectivity is controlled by the silyl radical attack of the sterically less hindered or less substituted terminal allylic carbon atom.