Reaction and application of perfluoroimidates

为了改善三氯乙酰亚胺的化学性质，我们设计合成了苄基、烯丙基、环氧基和糖基酰亚胺的全氟类似物。在-78℃下，全氟酰胺与“活化的”二甲基亚砜生成挥发性全氟腈。全氟酰亚胺合成的关键步骤是在DBU存在下，在脱水条件下与全氟腈上的含吸电子取代基的全氟腈进行原位醇加成反应。所得的三氟乙酰亚胺比三氯类似物更稳定，易于通过SiO_2柱层析和/或蒸馏进行纯化。合成的MPM-和DMPM-全氟亚胺类化合物可以作为稳定的羟基保护剂，取代三氯乙酰亚胺类化合物，具有较好的化学性质和可比产率。接着研究了烯丙基类似物的3，3-S重排、环氧类似物的酸催化环化反应和糖类似物的糖基化反应。烯丙基、环氧基和糖基三氟乙酰亚胺可以作为相应的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.