An oxidant-free and mild approach to fluorenones via direct excitation of aldehyde

In a recent issue of Angewandte Chemie International Edition, Wu and co-workers reported a novel C(sp2)–H bond-activation approach to synthesizing fluorenones, xanthones, and thioxanthones. It features cobaloxime as the redox catalyst to stabilize the active triplet-state intermediate and eliminate the β-H under mild conditions through a single-electron-transfer pathway.