The halogen dance rearrangement is an organic reaction in which a halogen substituent moves to a new position on an aromatic ring system. It was discovered through investigations on the conversion of 1,2,4-Tribromobenzene to 1,3,5-tribromobenzene catalyzed by sodium amide at -33 °C. The "reaction is seldom used" however.
The reaction proceeds by an SE1 mechanism involving an aryl carbanion.
The halogen dance concept can be extended from benzene derivatives to other aromatic systems. For instance furan, thiophene, and oxazoles.
Further reading
References
General references Participation of oligochlorobenzenes in the base-catalyzed halogen dance Martin H. Mach, Joseph F. Bunnett; J. Org. Chem.; 1980; 45(23); 4660-4666.