Anaerobic Hydroxylation of C(sp3)–H Bonds Enabled by the Synergistic Nature of Photoexcited Nitroarenes

Abstract

A photoexcited nitroarene-mediated, anaerobic C–H hydroxylation of aliphatic systems is reported. The success of this reaction is due to the bifunctional nature of the photoexcited nitroarenes, which serve as the C–H bond activator and the oxygen atom source. Compared to previous methods, this approach is cost and atom economical due to the commercial availability of the nitroarene, the sole mediator of the reaction. Owing to the anaerobic conditions of the transformation, a noteworthy expansion in substrate scope can be obtained compared to prior reports. Mechanistic studies support that the photoexcited nitroarenes engage in successive hydrogen atom transfer and radical recombination events with hydrocarbons, leading to N-arylhydroxylamine ether intermediates. Spontaneous fragmentation of these intermediates leads to the key oxygen atom transfer products.

Photocatalytic Late-Stage C–H Functionalization

“…Estrone acetate and ibuprofen methyl ester were among the complex substrates that successfully delivered their corresponding benzyl alcohol. 516 Itami and co-workers found acridinium species able to reduce (diacetoxyiodo)benzene (PIDA). The hypervalent iodine species forms acetate nucleophiles and, ensuing decarboxylation, hydrogen-atom-abstracting methyl radicals.…”

“…Parasram and co-workers demonstrated that photoexcited nitro-compounds can act as hydrogen-atom abstracting agents and promote the anaerobic oxygenation of C­(sp 3 )–H bonds. Estrone acetate and ibuprofen methyl ester were among the complex substrates that successfully delivered their corresponding benzyl alcohol . Itami and co-workers found acridinium species able to reduce (diacetoxyiodo)­benzene (PIDA).…”