Carbohalogenation

The last 20 years has witnessed significant advances in reactions enabling the transfer of a C–X group across a π-bond; commonly referred to as the carbohalogenation reaction. Broadly speaking, there are three approaches to enable this reactivity; (1) radical-type processes often described as an atom-transfer radical addition (ATRA) sequence. (2) transition metal migratory insertion across a π-system, followed by reductive elimination of the C–X bond (3) activation of the π-system with a π-acid, followed by nucleophilic attack and subsequent C–C or C–X bond formation. This chapter will aim to highlight the different strategies leveraged to achieve carbohalogenation including transition metal catalysis (both two-electron and one-electron reactions), hypervalent iodine chemistry, metallaphotoredox catalysis, organophotoredox catalysis, electrochemistry and enzymatic approaches.