Reaction and application of perfluoroimidates

为了提高三氯乙酸酯的化学性能，设计并合成了苯基、烯丙基、环氧和糖基类的全氟类似物。在-78℃下，由具有“活化”二甲基亚砜（DMSO）的全氟酰胺生成挥发性全氟腈。设想全氟咪酯合成的关键步骤是在DBU存在的脱水条件下，在咪酯上含有吸电子取代基的全氟腈上原位加成醇。所得的三氟乙酸酯比三氯类似物更稳定，易于用SiO_2柱层析和/或蒸馏纯化。所制得的MPM-和DMPM-全氟酰亚胺可作为稳定的羟基保护试剂代替三氯乙酸酯，具有优异的化学性能和相当的产率。接下来研究了丙烯基类似物的3,3-异位重排、环氧类似物的酸催化环化和糖类似物的糖基化。烯丙基、环氧和糖基三氟乙酸酯可作为相应三氯类似物的可交换前体。

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.