New Syntheses of Substituted Pyridines via Bromine–Magnesium Exchange

Bromine–magnesium exchange using iPrMgCl in THF at room temperature on 2-, 3- and 4-bromopyridines allowed the synthesis of various functionalized pyridines. The methodology was successfully used for the synthesis of 4-azaxanthone. Moreover, single exchange reactions observed on 2,6-, 3,5-, 2,3- and 2,5-dibromopyridines, with complete regioselectivity in the case of 2,3- and 2,5-dibromopyridines, afforded substituted bromopyridines, which were then involved in a second exchange step to provide difunctionalized pyridines.