Metal‐Free Radical CH Functionalization via Aldehyde Auto‐Oxidation

Abstract

Oxidative functionalization of CH bond involving free‐radical intermediate offers a great opportunity for selective conversion of abundant chemicals to value‐added materials under mild conditions with remarkably high functional group tolerance. Accordingly, radical‐mediated synthesis receives considerable interest in pharmaceutical, agrochemicals, and polymer sciences. Numerous effective strategies for the functionalization of CH bonds through free‐radical intermediate have been developed. Despite these advancements in radical CH functionalization chemistry, the generation of free‐radical intermediate via oxidative homolytic activation of unactivated CH bond under sustainable conditions remains challenging. In this connection, the auto‐oxidation of organic compounds that enables selective generation of reactive free‐radical intermediate upon exposure of organic compounds to O 2 is of particular attraction. The auto‐oxidation of organic feedstocks has already been applied in the industrial production of commodity chemicals such as phenols and terephthalic acid. Nevertheless, the utilization of aerobic oxidation of chemical feedstocks in organic synthesis under reagent‐free conditions is very rare, particularly for small‐scale synthesis of functionalized molecules. Recently, a significant advancement in aerobic radical functionalization of CH bond using aldehyde auto‐oxidation has been achieved. This article provides an overview of the current development on selective functionalization of CH bond using aldehyde auto‐oxidation that proceeds via a radical pathway under reagent‐free conditions.