The cyclopropane ring in 2-substituted 1, 1-cyclopropanedicarboxylates was regioselectively opened by using samarium(II) diiodide (SmI2) in a hexamethylphosphoric triamide (HMPA)-tetrahydrofuran (THF) (1 : 10) system under mild and neutral conditions to give (2-substituted ethyl)malonates in moderate to good yields. The cyclopropane ring in 2-substituted cyclopropanecarboxylates or 2-substituted 3-(trimethylsilyl)cyclopropanecarboxylates was similarly cleaved regioselectively by using SmI2 in a HMPA-THF (1 : 1) system to give 4-arylbutyrates or 4-aryl-3-(trimethylsilyl)butyrates in 16-89% yields. The reaction mechanism of these ring-opening reactions is discussed.
在温和且中性的条件下,使用二
碘化钐(II)(
SmI2)在六甲基
磷酸三酰胺(HMPA)-
四氢呋喃(THF)(1 : 10)体系中,对2取代的1,1-
环丙烷二
羧酸酯的
环丙烷环进行了区域选择性开环,得到了产率中等到良好的(2取代乙基)
丙二酸酯。而对于2取代的
环丙烷羧酸酯或2取代的3-(三甲基
硅基)
环丙烷羧酸酯,同样使用 在HMPA-THF(1 : 1)体系中进行了区域选择性开环,得到了4-芳基
丁酸酯或4-芳基-3-(三甲基
硅基)
丁酸酯,产率在16%到89%之间。讨论了这些开环反应的机制。