Cyclopropyl building blocks in organic synthesis. Part 81: Striving for unusually strained oxiranes: epoxidation of spirocyclopropanated methylenecyclopropanes
作者:Daniel Frank、Sergei I Kozhushkov、Thomas Labahn、Armin de Meijere
DOI:10.1016/s0040-4020(02)00695-6
日期:2002.8
1-Oxa[3]triangulane 13, the epoxide of methylenespiropentane, is thermally stable up to 300°C, but immediately rearranges to spiro[2.3]hexan-4-one (7) in the presence of lithium iodide at ambient temperature. The permethylated bicyclopropylidene 10 is simply less reactive than the parent bicyclopropylidene (6a) towards dimethyldioxirane, but yields the isolable epoxide 11 (94%) with mCPBA. In contrast
1-Oxa [3] triangulane 13(亚甲基螺戊烷的环氧化物)在高达300°C的温度下具有热稳定性,但在环境温度下在碘化锂存在下立即重排为螺[2.3]己烯-4-酮(7)。全甲基化的二环亚丙基10对母体二环二环氧乙烷的反应性仅低于母体双环亚丙基(6a),但是以m CPBA产生可分离的环氧化物11(94%)。相比之下,部分或完全spirocyclopropanated bicyclopropylidenes 18,20,和22,在与治疗米CPBA或二甲基二,没有提供相应的环氧化物,但重排为相应的cyclobutanones后行氧化19,21和23中的分别为59,100和97%,产率。