The SmI2 mediated cascade cyclisations of several methylenecyclopropyl ketones have been examined and found to proceed with high diastereoselectivity, which is critically dependent on the presence of HMPA in the reaction. In one case the radical species at the end of the cascade sequence underwent an unexpected and highly stereoselective dimerisation. The cascade methodology has been applied to a short synthesis of (±)-paeonilactone B and of (±)-6-epi-paeonilactone A.
我们研究了
SmI2 介导的几种亚甲基环丙基酮的级联环化反应,发现这种反应具有很高的非对映选择性,而这种选择性主要取决于反应中 HMPA 的存在。在一个案例中,级联序列末端的自由基发生了意想不到的高立体选择性二聚反应。级联方法已应用于 (±)-paeonilactone B 和 (±)-6-epi-paeonilactone A 的简短合成。