Photocatalytic Branched Allylic C-H Oxygenation of Terminal Alkenes with Free Oxygen-Based Nucleophiles

Allylic ethers are important functional motifs widespread in bioactive molecules and natural products and serve as versatile synthetic intermediates for value-added target molecules. Therefore, developing general and direct methods to allylic ethers from feedstocks is highly desirable. Direct cross-coupling of alkenes with free alcohols by allylic C-H functionalization under mild conditions represents the most ideal way for the synthesis of branched allylic ethers. Herein, a dual catalysis of visible-light and cobaloxime enables allylic C-H direct oxygenation of alkenes with alcohols to afford branched allylic ethers has been developed. Notably, exclusive regio- and chemoselective mono-etherification of C-H bond to give branched allylic ethers with primary, secondary, and tertiary free alcohols. Moreover, other oxygen-based nucleophiles, such as carboxylate and cyclic 1,3-diketones, are also compatible in the reaction, providing a mild and robust allylic oxygenation of more steric hindered C-H from easily available alkenes.