Reactions of trifluoromethylpyridines with alkyllithium reagents. Directing effects of the trifluoromethyl groups

Article abstract of DOI:10.1016/S0040-4020(01)89575-2

Reactions of eight trifluoromethyl substituted pyridines with alkyllithium reagents were examined. 3-Trifluoromethylpyridine, 3,4-, and 3,5-bis(trifluoromethyl)pyridines undergo regioselective lithiation at the 2-position thus providing an easy access to 2-functionalised trifluoromethylpyridines. The reactions of 2-trifluoromethylpyridine, 2,4-, 2,6-bis(trifluoromethyl)-pyridines and 2,4,6-tris(trifluoromethyl)pyridine result exclusively by addition of RLi to the -N=C-bond. 2,5-Bis(trifluoromethylpyridine), depending on the reaction temperature, gives either 2-lithio derivative or an adduct.