Halogen shuffling in pyridines: site selective electrophilic substitutions of 2-chloro-6-(trifluoromethyl)pyridine

When treated with lithium diisopropylamide in THF at -85 Deg and subsequently with iodine, 2-chloro-6-(trifluoromethyl)pyridine is neatly converted into its 3-iodo deriv. The latter can be quant. isomerized to afford 2-chloro-4-iodo-6-(trifluoromethyl)pyridine. Either iodo compd. can serve as the starting material for further manipulation in reaction sequences consisting of halogen/metal exchange and electrophilic trapping. [on SciFinder (R)]