Chloro-5-iodoimidazole

As with other halogenation processes, the monoiodination of imidazole has proved to be a difficult process. A number of recent approaches have shown some success. Thus, imidazoles can be monoiodinated at C-2 via the 2-lithio derivative or Grignard reagent. With iodine and iodic acid 5-chloro-l-methylimidazole was converted to a mixture of 12.8% of the 2,4-diiodo compound and 27.5% of the 4-iodo product. The previously undescribed 2-iodoimidazole (119) has been prepared in low yield by the sequence shown in Eq. (27). ... 

Bromo- and 2-iodoimidazoles are reductively dehalogenated by the sulfite ion. The corresponding chloro and fluoro compounds are stable to this soft reagent (42). It should be noted that the fluorine is easily replaced by hard bases via an SwAr mechanism. 

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