Photo‐ and Cerium‐Mediated C─C Bond Cleavage for the Deconstructive Diversification of Cyclic Acids

The selective cleavage of inert carbon-carbon bonds in unstrained rings continues to pose a formidable challenge in chemical synthesis. Current methods for C(sp³) ─C(sp³) bond cleavage are highly limited, typically relying on transition-metal catalysis to facilitate ring-opening via small-ring strain or inducing β-fragmentation after generating radicals from oxygen or nitrogen atoms pre-installed in the substrate. Herein, we introduce an effective strategy for the decarboxylative ring-opening functionalization of α-trisubstituted carboxylic acids, mediated by both light and cerium. This method enables the ring-opening of carboxylic acids with ring sizes ranging from 3 to 12 members, allowing the construction of C─CN, C-halide, C─C, C─Se, and C─oxime bonds. Notably, this reaction does not require the pre-installation of an oxygen atom in the substrate, as the carbonyl group is derived from atmospheric oxygen. Furthermore, late-stage modification establishes distally functionalized carbonyl compounds, which serve as versatile synthons for accessing valuable building blocks.