Organic charge-transfer complex induces chemoselective decarboxylation to aryl radicals for general functionalization

Aryl radicals are used as versatile intermediates for arylations for the preparation of natural products, drugs, and functional materials. Photoinduced direct decarboxylation of aryl carboxylic acids to aryl radicals is considered attractive because of the wide availability and stability of aryl carboxylic acids and mild conditions. However, direct decarboxylation has been clearly shown to be very challenging because aryl carboxyl radicals favor strongly competitive addition to arene pathways. Herein, we demonstrate a solution to this challenge: a charge-transfer complex of aryl carboxylate via n-π∗ and π-π interactions induces chemoselective decarboxylation to aryl radicals for general functionalization. Presumably, the triplet complex significantly slows the rate of second-order aryl carboxyl radical addition to the aryl ring, resulting in selective decarboxylation to aryl radicals. Our studies should inspire numerous arylations in various fields under mild conditions with the use of easily available and stable aryl carboxylic acids, as well as new photoredox catalytic modes for selective radical transformations.