[GRAPHICS]Additions of terminal alkynes to electrophiles are important transformations in organic chemistry. Generally, activated terminal alkynes react with epoxides in an S(N)2 fashion to form homopropargylic alcohols. We have developed a new synthetic method to form propargylic alcohols from epoxides and terminal alkynes via 1,2-shifts. This method involves cationic zirconium acetylides as both the activator of epoxides and nucleophiles. line to the mild conditions to pre-activate alkynes with silver nitrate, this synthetic method is useful for both electron-rich and electron-deficient alkynes with other acid- and base-sensitive functional groups.
Asymmetric Organocatalytic 1,4-Addition Reactions Starting from Enals with<i>gem</i>-Difluoroalkyl Side Chains
gem-Difluoroenals are excellent substrates for asymmetricorganocatalytic 1,4-additions of thiols and anilines. By using diarylsilylprolinol ether as a catalyst, good to excellent yields with ee values in the same range (up to 98 %) were obtained. The CF2R group strongly activates the enals towards these organocatalytic additions.
gem-Difluoroenals 是硫醇和苯胺的不对称有机催化 1,4-加成的极好底物。通过使用二芳基甲硅烷基脯氨醇醚作为催化剂,在相同范围内的 ee 值(高达 98%)下获得了良好到极好的收率。CF2R 基团对这些有机催化添加物强烈激活烯醛。