Umpolung reactivity of difluoroenol silyl ethers with amines and amino alcohols. Application to the synthesis of enantiopure alpha-difluoromethyl amines and amino acids

摘要

Difluoroenol silyl ethers, produced in situ from acylsilanes and CF3TMS, react as electrophiles with amines to give difluoroimines, via the corresponding hemiaminal adduct, as evidenced by F-19 NMR spectroscopy. Reaction with (R)-phenylglycinol led to 2-difluoromethyloxazolidines. After separation of the diastereomers, reduction with LAH and Strecker-type synthesis gave enantiopure alpha-difluoromethy-lamines and alpha-difluoromethyl-alpha-amino acids, respectively.