Halogen dance rearrangement

The halogen dance rearrangement, also known as halogen scrambling, halogen migration, or halogen isomerization, is the migration of halogen substituents to a different position on an aromatic or heteroaromatic ring, resulting in a net positional shift of the halogen from its original location in the starting material to a new position in the product, effectively “dancing” across the ring. This transformation belongs to the broader class of 1,2-rearrangement reactions. It offers a powerful strategy for achieving functionalization at positions in aromatic and heteroaromatic systems, which are often inaccessible or challenging through conventional synthetic methods.^[1] Moreover, the halogen dance rearrangement enables strategic electrophilic interception at the vacated halogen site, concurrently establishing a newly nucleophilic centre at the halogen’s migrated position, thereby offering dual opportunities for site-selective functionalization. The sole driving force for this reaction is thermodynamics.