Enantioselective Contrathermodynamic Olefin Isomerization

A light-driven method for the enantioselective contrathermodynamic positional isomerization of olefins based on excited-state electron transfer is reported. Sequential oxidation and deprotonation of a tetrasubstituted enol ether generates an allylic radical which is captured by a Cr(II) cocatalyst bearing a chiral bioxazoline (BiOX) ligand. Regio- and enantioselective protodemetalation of the nascent Cr(III) allyl complex by methanol yields the terminal olefin product with enantioselectivities of up to 95:5 er. Kinetic and isotopic labeling studies support an enantiodetermining protodemetalation and reveal the presence of two primary KIEs within the same catalytic manifold.