NHCs and Visible Light-mediated Photoredox Co-catalyzed Radical 1,2-Dicarbonylation of Alkenes for 1,4-Diketones

Alkenes are ubiquitous, and radical difunctionalization of alkenes represents one of the most practical approaches to constructing value-added compounds. Dicarbonylation of alkenes provides direct access to value-added 1,4-dicarbonyl compounds. However, selectivity control for unsymmetric 1,2-dicarbonylation is an unclosed challenge. We herein describe NHCs and photocatalysis co-catalyzed three competent radical 1,2-dicarbonylation of alkenes by distinguishing two carbonyl groups, providing structurally diversified 1,4-diketones. Mechanistic studies indicated that NHCs-stabilized ketyl-type radicals originate from aroyl fluorides via oxidative quenching process of excited photocatalysis, and acyl radicals are generated from single-electron-oxidation of α-keto acids. Distinct properties of acyl radical and NHCs-stabilized ketyl radical contributed to selectivity control. Transient acyl radicals are rapidly added to alkenes delivering alkyl radicals, which undergo subsequent radical-radical cross-coupling with ketyl-type radicals, affording 1,2-dicarbonylation products. This transformation features mild reaction conditions, broad substruct scope, and excellent selectivity, providing a general and practical approach for the dicarbonylation of olefins.