REACTIONS OF TRIFLUOROMETHYLPYRIDINES WITH ALKYLLITHIUM REAGENTS - DIRECTING EFFECTS OF THE TRIFLUOROMETHYL GROUPS

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(trifluoromethy)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.