Visible Light-Driven Radical trans-Hydrosilylation of Electron-Neutral and -Rich Alkenes with Tertiary and Secondary Hydrosilanes.

A visible light-driven radical hydrosilylation of electron-neutral and -rich alkenes has been investigated on the basis of a newly developed catalytic reaction system composed of eosin Y, thiol, and base additives. A variety of linear and cyclic alkenes with different substitution patterns were found to undergo such metal-free hydrosilylation with tertiary and secondary hydrosilanes in a chemo-, regio-, and stereoselective manner. Comparison of the reactivity of diene compounds and late-stage hydrosilylation of steroid drugs were also explored. Deuterium labeling experiments reveal that a stepwise formation of C-Si and C-H bonds with a trans stereochemistry is preferred, in which the thiol may behave as a hydrogen atom transfer agent.