The title carbenoids (7 and 8) prepared by the action of butyllithium on dihalocyclopropanes are smoothly methylated with methyl iodide. The product ratio of cis-methylated product (3)/trans-methylated one (4) (or endo-methylated product (5)/exo-methylated one (6) is found to depend on the aging period of the carbenoids; thermodynamic equilibration gives almost 3 or 5. This procedure has been extended to general alkylation by utilizing HMPA co-solvent. The resulting α-alkylated cyclopropyl halides are converted into allylic acetates or cyclopropyl acetates upon acetolysis and also into alkylidenecyclopropanes upon base treatment. The protonolysis of 8 gives trans- or exo-bromocyclopropanes stereoselectively.
通过二卤
环丙烷与丁基
锂作用制备的碳宾(7和8)能顺利地用甲基
碘进行甲基化。顺式甲基化产物(3)/反式甲基化产物(4)(或内型甲基化产物(5)/外型甲基化产物(6)的产率比取决于碳宾的老化时间;热力学平衡几乎给予3或5。该方法已通过利用六甲基
磷酰胺(HMPA)作为共溶剂扩展到一般烷基化。得到的α-烷基化环丙基卤代物在乙酰解后转化为
烯丙基乙酸酯或
环丙基乙酸酯,并且在碱处理下转化为烷基
亚甲基环丙烷。8的质子分解选择性地得到反式或外型
溴代环丙烷。