Reaction and application of perfluoroimidates

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We designed and synthesized the perfluoro analogues of benzyl-type, allyl, epoxy and glycosyl imidates in order to improve the chemical properties of trichloroacetimidates. Volatile perfluoronitriles were generated from perfluoroamides with an "activated" dimethyl sulfoxide (DMSO) species at -78 ℃. The key step in perfluoroimidate synthesis was envisioned to be the in situ alcohol addition to perfluoronitriles containing electron-withdrawing substituents on the imidate under dehydration conditions in the presence of DBU.The obtained trifluoroacetimidates were more stable than the trichloro analogue and were easily purified by SiO_2 column chromatography and/or distillation. Obtained MPM- and DMPM- perfluoroimidates could serve as stable protecting reagents for hydroxy functions in place of the trichloroacetimidate with excellent chemical properties and in comparable yields. The 3,3-sigmatropic rearrangement of allylic analogues, acid-catalyzed cyclization of the epoxy analogues and glycosylation of sugar analogues were next studied. Allyl, epoxy and glycosyl trifluoroacetimidates can serve as an exchangeable precursor for the corresponding trichloro analogues.