Iodo-Bridged Transition States; New Mechanistic Pathways for Base-Catalyzed Halogen Dance

First reported by Joseph Bunnet et al., base-catalyzed halogen dance reaction has puzzled chemists for decades, to come up with new ideas regarding the mechanism of this chemical reaction. A series of deprotonation followed by fast metal-halogen exchanges are among the most recent mechanisms reported so far. Using density functional theory, DFT, computations and focused on the Bunnet type isomerization halogen dance reactions of iodobenzene derivatives, iodo-bridged transition state, TS, are proposed. The new TS is then used to lay out 8 possible isomerization and 18 possible disproportionation paths. The possible mechanistic pathways are then carefully analyzed based on TS's energy and protonation/deprotonation steps to find the most suitable pathways. These mechanistic pathways, sketch a comprehensive pattern for base-catalyzed halogen dance. There is still a lot to study in the chemistry of poly halogenated aryls.