Treatment of glycosyl trichloroacetimidates in nitriles as solvent at low temperatures with trimethylsilyl trifluoro-methanesulfonate (SN1-type conditions) leads under α-face attack to fast nitrilium-nitrile conjugate formation. These intermediates are converted rapidly in the presence of various acceptors into β-disaccharides in high yields and diastereoselectivities.
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Schmidt et al. (1990) studied this question.