Halogen ‘dance’: a way to extend the boundaries of arene deprotolithiation

The base-catalyzed arene halogen ‘dance’ was discovered in 1959 when, upon reaction of sodium amide with polyhalogenobenzenes in liquid ammonia, 1,2,4-tribromobenzene was converted to its 1,3,5-isomer.1 The group of Bunnett next identified more satisfactory isomerization catalysts, but could not avoid formation of arynes and dismutation, at the origin of a large numbers of unwanted products.2 In spite of such issues, by showing that the isomerization of available compounds containing heavy halogens into less accessible ones was feasible, this study has attracted interest from chemists.