Recent Progress on[3+2] Ring-Expansion Reaction of Cyclopropane with Unsaturated Compounds

Abstract

Due to its high ring strain, cyclopropanes can react with a variety of unsaturated compounds to construct fivemembered carbo-and hetero-cycles through [3＋2] ring-expansion reaction. These five-membered compounds are key skeletons of many drugs, natural products and bioactive molecules, and are also an important class of organic intermediates which have wide applications in medicine, agriculture, chemical engineering, organic synthesis and other related areas. Recently, more and more chemists have constructed a lot of complex five-membered carbo-and hetero-cycles by using cyclopropane as a three-carbon synthon, which has promoted the rapid development of focus area. This review summarizes the most recent [3＋2] ring-expansion reaction of cyclopropanes with compounds containing unsaturated bonds such as olefins, aldehydes, ketones and nitriles in the past decade. Moreover, the prospects of future development are also discussed. Keywords cyclopropane; unsaturated bond; [3＋2] ring-expansion reaction; five-membered ring 环丙烷是结构最简单的环烷烃, 由于其环 C-C 的 键角远远小于正常 C(sp 3 )-C(sp 3 )的键角, 导致其键角 的弯曲程度增大, 因此具有很强的环张力 [1～3] (应变能为 121.4 kJ•mol -1 [3] ). 环丙烷可被具有不同电子特性的基 团取代, 并生成一系列环丙烷衍生物. 经实验测定和理 论计算 [2][3][4]