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. 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.