Remote Spin-Center Shift Enables Activation of Distal Benzylic C–O and C–N Bonds

Abstract

A spin-center shift (SCS) is a radical process that commonly involves a 1,2-radical shift along with the elimination of an adjacent leaving group by a two-electron ionic movement. The conventional SCS process is largely limited to 1,2-radical translocation, while a remote SCS event involving 1,n-radical translocation over a greater distance to enable distal bond functionalization remains largely underexplored. Herein, we report the boryl radical-promoted distal deoxygenation and deamination of free benzylic alcohols and simple benzylic amines, respectively, through a remote SCS event. The reaction was initiated by the addition of a 4-dimethylaminopyridine (DMAP)-boryl radical to the carbonyl oxygen atom of a benzoate or benzamide. Then, radical translocation took place across the aromatic ring to promote benzylic C−O or C−N bond cleavage. The resulting radical intermediate subsequently coupled with various alkenes to afford a wide range of alkylated products. The proposed mechanistic pathway was supported by experimental investigations.