Conjugate Addition of Perfluoroarenes to alpha,beta-Unsaturated Carbonyls Enabled by an Alkoxide-Hydrosilane System: Implication of a Radical Pathway

Abstract

Conjugate addition of organometallic reagents to alpha,beta-unsaturated carbonyls is a key strategy for the construction of carbon-carbon bond in organic synthesis. Although direct C-H addition to unsaturated bonds via transition metal catalysis is explored in recent years, electron deficient arenes that do not bear directing groups continue to be challenging. Herein we disclose the first example of a conjugate addition of perfluoroarenes to alpha,beta-unsaturated carbonyls enabled by an alkoxide-hydrosilane system. The reaction is convenient to carry out at room temperature over a broad range of substrates and reactants to furnish synthetically versatile products in high to excellent yields. Mechanistic experiments in combination with computational studies suggest that a radical pathway is most likely operative in this transformation. The hypervalent silicate and silanide species, which are relevant to the proposed mechanism, were observed experimentally by NMR and single crystal X-ray diffraction analyses.