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-Ni^II acts as the nucleophilic species in the coupling reaction with carbonyls.