Chemoselective Functionalization of Tertiary C‐H Bonds of Allylic Ethers: Enantioconvergent Access to sec,tert‐Vicinal Diols

While enantioenriched alcohols are highly significant in medicinal chemistry, total synthesis, and materials science, the stereoselective synthesis of tertiary alcohols with two adjacent stereocenters remains a formidable challenge. In this study, we present a dual catalysis approach utilizing photoredox and nickel catalysts to enable the unprecedented chemoselective functionalization of tertiary allylic C‐H bonds in allyl ethers instead of cleaving the C‐O bond. The resulting allyl‐Ni intermediates can undergo coupling with various aldehydes, facilitating a novel enantioconvergent approach to access extensively functionalized homoallylic sec,tert‐vicinal diols frameworks. This protocol exhibits nice tolerance towards functional groups, a broad scope of substrates, excellent diastereo‐ and enantioselectivity (up to 20:1 dr, 99% ee). Mechanistic studies suggested that allyl‐NiII acts as the nucleophilic species in the coupling reaction with carbonyls.