Purification-Free Preparation of Trifluoroacetimidoyl Chlorides and Their Use in Catalytic Chemical Glycosylation

This Letter describes a purification-free method for synthesizing 2,2,2-trifluoro-N-phenylacetimidoyl chloride and several related congeners from their corresponding amides using POCl3 and pyridine. N-(2,4-Dichlorophenyl)-2,2,2-trifluoroacetimidoyl chloride demonstrated superior stability compared to 2,2,2-trifluoro-N-phenylacetimidoyl chloride, which is commonly used for glycosyl donor synthesis of the Yu-type. The described method also enabled a general and highly β-selective synthesis of trifluoroacetimidate glycosyl donors using DABCO in toluene. The donors were shown to undergo efficient glycosylation with various glycosyl acceptors.