Photomediated Chromium-Catalyzed Regio-, Diastereo-, and Enantioselective Deoxygenative Coupling of Activated Allylic and Propargylic Alcohols with Aldehydes

Abstract Chromium-catalyzed asymmetric Nozaki–Hiyama–Kishi (NHK) reaction is a powerful tool for constructing synthetically valuable enantioenriched homoallylic alcohols and allenols. However, catalytic asymmetric NHK-type coupling of allylic or propargylic C–O electrophiles remains largely underdeveloped. Herein, we report a photomediated chromium-catalyzed deoxygenative coupling of activated allylic and propargylic alcohols with aldehydes, enabling the synthesis of a variety of chiral homoallylic alcohols with wide structural diversity and allenols. The reactions were performed under mild conditions, and a wide range of synthetically useful functional groups was found to be well tolerated. Importantly, this method provides a straightforward way for the construction of homoallylic alcohols bearing a chiral quaternary carbon center with high ee and dr. Furthermore, stereodivergent access to all four homoallylic alcohol stereoisomers is realized through orthogonal combinations of Z/E-configured allylic alcohols and R/S-configured ligands. Combined experimental and computational mechanistic studies provided insight into the key catalytic intermediate and the origin of stereocontrol.