Photocatalytic Metal Hydride Hydrogen Atom Transfer Mediated Allene Functionalization by Cobalt and Titanium Dual Catalysis

Catalytic metal hydride hydrogen atom transfer (MHAT) reactions have proven to be a powerful method for alkene functionalization. This work reports the discovery of Co‐porphines as highly efficient MHAT catalysts with a loading of only 0.01 mol % for unprecedented chemoselective allene functionalization under photoirradiation. Moreover, the newly developed bimetallic strategy by the combination of photo Co‐MHAT and Ti catalysis enabled the successful carbonyl allylation with a wide range of amino, oxy, thio, aryl, and alkyl‐allenes providing expedient access to valuable β‐functionalized homoallylic alcohols in over 100 examples with exceptional regio‐ and diastereoselectivity. Mechanism studies and DFT calculations supported that selectively transferring hydrogen atoms from cobalt hydride to allenes and generating allyl radicals is the key step in the catalytic cycle. Reported is on the photo Co metal hydride hydrogen atom transfer (MHAT) reaction for chemoselective allene functionalization by using Co‐porphines as catalysts and the Hantzsch ester as an H atom and electron donor. The merger of Co MHAT and Ti catalysis under photoredox conditions enabled successful carbonyl allylation, providing access to valuable β‐functionalized homoallylic alcohols with exceptional regio‐ and diastereoselectivity.