Selective Cleavage of Carbon–Carbon Bonds of Aryl Ketones by Photocatalysis

Abstract Selective cleavage of inert C─C bonds in unstrained molecules under mild conditions remains a long-standing challenge in synthetic chemistry. In preorganized unstrained aryl ketones, Ar─C(O) bonds are particularly recalcitrant because of their high bond dissociation energy and low polarization, and their selective activation typically requires strained rings, directing groups, or harsh conditions. Here, we report a visible-light-driven triplet energy-transfer strategy that enables selective cleavage of the Ar─C(O) bond in these preorganized aryl ketones through intramolecular 1,3-acyl migration, thereby providing direct access to aliphatic ketones embedded in 9,10-dihydrophenanthrene scaffolds under mild conditions. Mechanistic experiments and density functional theory (DFT) calculations support a sequence involving triplet-state 6π photocyclization, dearomatization, and rearomatization-driven 1,3-acyl migration. This work provides a conceptually distinct photochemical solution to Ar─C(O) bond cleavage in preorganized unstrained aryl ketones and highlights rearomatization-enabled acyl migration as a useful design principle for C─C bond activation.