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.
Generation and Reaction of Metal Free Trifluoroacetimidoyl Carbanion