N-Aryl trifluoroacetimidoyl lithiums. synthetic equivalent of trifluoroacetyl carbanion, are prepared from N-aryl trifluoroacetimidoyl iodides by iodine-lithium exchange reaction with n-BuLi in ether at -78-degrees-C and react with various electrophiles, leading to synthetic blocks for trifluoromethylated nitrogen heterocycles.
(Trifluoroacetimidoyl)lithiums and Their Reaction with Electrophiles
N-Aryltrifluoroacetimidoyl iodides have been lithiated with n-butyllithium in ether. Because of the highly ionic nature of a carbon-lithium bond, the imidoyl carbanions are only stable below -60 degrees C. The reaction temperature, solvent, and steric bulkiness of the N-aryl substituents greatly affected alkylation. [N-(2,6-dimethylphenyl)trifluoroacetimidoyl] lithium in ether is stable enough to be alkylated and silylated on the imino carbon with electrophiles such as acyl chlorides, aldehydes, ketones, chloroformate, and trimethylsilyl chloride.