Visible-Light Photoredox-Catalyzed Hydroalkoxymethylation of Activated Alkenes Using α‑Silyl Ethers as Alkoxymethyl Radical Equivalents

A new neutral silicon-based traceless activation group (TAG) for visible-light photoredox-catalyzed hydroalkoxymethylation of alkenes is presented. This reaction involves in-situ-generated alkoxymethyl radical via single electron oxidation (SET) of α-TMS-substituted ethers, followed by subsequent conjugate addition to activated alkenes. Various functional groups were tolerated both under mild metal and metal-free conditions to provide good to excellent yields. Furthermore, the addition products were transformed to valuable synthetic building blocks, such as carboxylic acids, γ-butyrolactones, and complex aryl alkyl ethers.