Visible light-induced bromine radical enhanced hydrogen atom transfer (HAT) reactions in organic synthesis

Abstract

Hydrogen atom transfer (HAT) reactions have gained prominence in organic synthesis for providing a straightforward approach towards C–H bond activation for the formation of C-centered radical intermediates. However, halogen radical-assisted hydrogen atom transfer (HAT) reactions have become an interesting tool for C–H bond activation, facilitating the formation of C–C and C–X bonds. In particular, the bromine radical (Br˙) has garnered attention because of its remarkable capability as a hydrogen acceptor, which abstracts an H-atom from a C–H bond and generates a C-centered radical intermediate. Typically, transition metal- and organo-photocatalysts are commonly used to generate a bromine radical (Br˙) from a bromine anion (Br⁻). This newly generated bromine radical (Br˙) is useful in several organic transformations via C–H bond activation. In this review, we provide recent updates on bromine radical (Br˙) assisted hydrogen atom transfer (HAT) reactions with their scope, mechanism, and limitations.