Visible Light-Induced Bromine Radical Enhanced Hydrogen Atom Transfer (HAT) Reactions in Organic Synthesis

Abstract

Hydrogen atom transfer (HAT) reactions have gained a prominent space in organic synthesis for allowing 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 toward C-H bond activation, allowing for the formation of C-C and C-X bond formations. In particular, the bromine radical (Br•) has garnered attention for 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 bromine radical (Br•) from bromine anion (Br-). This newly generated bromine radical (Br•) is useful in several organic transformations via C-H bond activation. Hereby, in this review, we provide recent updates on bromine radical (Br•) assisted hydrogen atom transfer (HAT) reactions with their scope, mechanism, and limitations.