Direct Access to Monoprotected Homoallylic 1,2-Diols via Dual Chromium/Photoredox Catalysis

Herein, we present a dual catalytic strategy to efficiently obtain monoprotected homoallylic 1,2-diols by coupling abundant aldehydes with simple (silyl) enol ethers, thus providing direct access to this important motif without the (super) stoichiometric use of prefunctionalized metal-allyl species. The modularity of our approach is shown by the introduction of several silyl- and alkyl-based protecting groups. To highlight functional group tolerance and chemoselectivity, we demonstrate the functionalization of a variety of aliphatic and (hetero)aromatic aldehydes, even in the presence of ketones and esters. Mechanistic studies support a radical mechanism, starting from the single electron oxidation of the enol ether.