Photoinduced Nitroarenes as Versatile Anaerobic Oxidants for Accessing Carbonyl and Imine Derivatives

Abstract

Herein, we report a protocol for the anaerobic oxidation of alcohols, amines, aldehydes, and imines promoted by photoexcited nitroarenes. Mechanistic studies support the idea that photoexcited nitroarenes undergo double hydrogen atom transfer (HAT) steps with alcohols and amines to provide the respective ketone and imine products. In the presence of aldehydes and imines, successive HAT and oxygen atom transfer (OAT) events occur to yield carboxylic acids and amides, respectively. This transformation is amenable to a continuous-photoflow setup, which led to reduced reaction times.

Recent Advances in Photoinduced Oxidative Cleavage of Alkenes

“…The ability of photoexcited ni-troarenes to yield oxygen atom transfer reactions was further investigated to furnish a variety of oxidized products in later studies. 56,57 A contemporaneous study by Leonori, Simonetti, and co-workers was also reported (Scheme 13). 58 The methodology is similar to Parasram's protocol in featuring the cleavage of alkenes promoted by electron-deficient nitroarenes.…”

“…Interestingly, trans-stilbene derivatives led to diketone formation 55 instead of the cleavage product owing to the reduced reactivity of the highly conjugated starting material. The authors nicely illustrated that their protocol is amenable to late-stage functionalization of medicinally relevant molecules (56,57).…”

The application of nitroarenes in catalyst‐free photo‐driven reactions

“…In 2023, Parasram [38] disclosed an anaerobic oxidation strategy involving alcohols, aldehydes, and imines, facilitated by photoexcitable nitroarenes (Scheme 18). The methodology demonstrates robust substrate compatibility, particularly with trifluoromethyl and cyano-substituted alcohols, yielding the respective ketones in high yields of 70 % and 98 % (115 a, 115 b).…”

Oxidative cleavage of ketoximes to ketones using photoexcited nitroarenes

“… 27 These initial reports set the stage for additional developments such as the dihydroxylation of alkenes, 28 hydroxylation of aliphatic substrates, 29 and the oxidation of aldehydes and aldimines to carboxylic acids and amides, respectively. 30 Furthermore, Li recently reported a photoinduced cascade process between nitroarenes and amines to form isoxazolidine derivatives. 31 …”