Practical Application of Ketene Acetal-type Reactive Acylating Reagents

点击翻译按钮获取中文摘要

Usually, the acylation reaction has been carried out by the use of activated carboxylic acid derivatives such as acid halides. However, due to the reaction conditions and formation of acidic and/or non volatile by-products, several problems including side-reactions, decomposition and/or difficult purification of the products have often been encountered. In this project, we have aimed at the resolution of these problems and the development of novel synthetic methods by the use of the ketene acetal-type acylating reagents 1 which feature mild reaction conditions and formation of volatile esters as the single by-product. According to the research proposals, the following results were obtained.1.Various types of 1 are prepared by the ruthenium-catalyzed addition of caboxylic acids to ethoxyacetylene. Preparation of the silyloxyacetylenes, potent precursors for preparation of novel ketene acetal-type reagents, from silylketenes was established.2.The enzymatic resolution of alcohols by trans … More acylation has been carried out by the use of vinyl esters. However, this method has a serious drawback of deactivation of the enzyme by the by-product, acetaldehyde. We have elucidated that the use of the reagents 1 overcomes this problem to act as novel, high reactive, and reliable acyl donors for enzymatic resolution of racemic alcohols and for asymmetrization of prochiral diols.3.Various types of 1 were applied to highly asymmetric Pummerer-type rearrangement reaction of aliphatic chiral sulfoxides and to similar Pummerer-type cyclization reactions. It was elucidated that increasing the electron-donating ability of the acyl group in 1 tended to increase enantioselectivity.4.We have developed the aromatic Pummerer-type reactions of p-sulfinylphenol derivatives by using trifluoroacetic anhydrides (TFAA), which caused the first ipso-substitution of the sulfur functional groups into the oxygen functional groups on the aromatic rings and provided a novel preparation of quinones and dihydroquinones. The use of 1 instead of TFAA allowed us the first isolation of the quinone mono O,S-acetal intermediates. Less