Further metalations and functionalizations of chloro-, bromo- and iodo(trifluoromethyl)pyridines

In accordance with the concept of regioexhaustive functionalization, both 3-chloro-2-(trifluoromethyl)pyridine and 2-bromo-6-(trifluoromethyl)pyridine were converted each time into the three possible carboxylic acids. 2-Bromo-4-(trifluoromethyl)pyridine, 2-bromo-5-(trifluoromethyl)pyridine, 2-iodo-4-(trifluoromethyl)pyridine, and 4-iodo-2-(trifluoromethyl)pyridine were selectively deprotonated and subsequently carboxylated at the resp. 3-positions. Finally, the N-pivaloyl-protected 2-amino-3-chloro-5-(trifluoromethyl)pyridine was deprotonated at the 4-position and the intermediate trapped with iodine and benzaldehyde. [on SciFinder (R)]