Acridine Orange Hemi(Zinc Chloride) Salt as a Lewis Acid‐Photoredox Hybrid Catalyst for the Generation of α‐Carbonyl Radicals.

A readily accessible organic‐inorganic hybrid catalyst is reported for the reductive fragmentation of α‐halocarbonyl compounds. The robust hybrid catalyst is a self‐stabilizing combination of ZnCl2 Lewis acid and acridine orange as the photoactive organic dye. Mechanistic specifics of this hybrid catalyst have been studied in detail using both photophysical and electrochemical experiments. A systematic study enabled the discovery of the appropriate Lewis acid for the effective LUMO stabilization of α‐halocarbonyl compounds and thereby lowering of reduction potential within the range of a standard organic dye. This strategy resolves the issues like dehalogenative hydrogenation or homo‐coupling of alkyl radicals by guiding the photoredox cycle through an oxidative quenching pathway. The cooperativity between the photoactive organic dye and the Lewis acid counterparts empowers functionalization with a wide range of coupling partners through efficient and controlled generation of alkyl radicals and serves as an appropriate alternative to the expensive late transition metal‐based photocatalysts. To demonstrate the application potential of this cooperative catalytic system, four different synthetic transformations of α‐carbonyl bromides were explored with broad substrate scopes. [ABSTRACT FROM AUTHOR]