Migration 1.3- iodine, intramolecular

Among the halogens, fluorine does not undergo rearrangement, and what evidence there is suggests that the rearrangement of chlorine is an intramolecular process (1,2 shift) whereas that of bromine appears to take place by both inter-and intramolecular routes. Less is known about iodine migration. 

Substituted (indol-2-yl)-ct-allenols show divergent patterns of reactivity under metal catalysis and an intramolecular 1,3-iodine migration has been reported (Scheme 208). Computational methods have addressed rearrangements of acyl, thioacyl, and imidoyl (thio)cyanates to iso(thio)cyanates, acyl iso(thio)cyanates to (thio)acyl isocyanates, and imidoyl iso(thio)cyanates to (thio)acyl carbodiimides, RCX-YCN RCX-NCY RCY-NCX RCY-XCN (X and Y = O, S, NR ). ... 

Besides iodine migration in fluoropyrazine serie the migration of the tributyl-stannyl group is known. When metalation of 2-fluro-3-tributylstannylpyrazine 383 was performed with 2.1 equiv. of LTMP with a short reaction time and was followed by protonation of the lithio derivative, compound 386, resulting from intramolecular tin/lithium exchange, was isolated in 63 % yield (Scheme 66) [215],... 

Aryl halides can be dehalogenated by Friedel-Crafts catalysts. Iodine is the most easily cleaved. Dechlorination is seldom performed and defluorination apparently never. The reaction is most successful when a reducing agent, say, Br or 1 is present to combine with the I" or Br coming off." Except for deiodination, the reaction is seldom used for preparative purposes. Migration of halogen is also found," both intramolecular and intermolecular." The mechanism is probably the reverse of that of 11-11." ... 

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