When treated with tert-butyllithium in THF at -50 Deg, N-BOC (tert-butoxycarbonyl) protected fluoroanilines and trifluoromethylanilines, e.g., o-, m-, or p-F3CC6H4NHCO2CMe3, undergo metalation at the position adjacent to that carrying the nitrogen. If, however, the nitrogen carries two alkyl or trimethylsilyl groups as substituents and highly polar metalating reagents such as butyllithium activated by N,N,N',N\",N\"-pentamethyldiethylenetriamine (PMDTA) or potassium tert-butoxide are employed, the fluoroaniline derivs. are preferentially deprotonated next to the halogen atom. [on SciFinder (R)]