Tetrahalogenomethanes: simple reagents for the synthesis of monohalogenated and mixed dihalogenated aromatic heterocycles via metal–halogen exchange from lithium compounds

Tetrabromo- or tetrachloromethane and 2-lithio derivatives of aromatic heterocycles rapidly produce the corresponding 2-bromo or 2-chloro derivatives in high yields through a metal–halogen exchange mechanism. This kind of reaction was also used to obtain, in good yields, 5-bromo-2-chlorothiazole and 5-bromo-2-chloro-N-methylimidazole.