环丙叉环丙烷——一个新的多功能有机合成子

介绍了一个新的多功能有机合成子环丙叉环丙烷及其衍生物的制备和反应，环 丙叉环丙烷现已可从环丙烷羧酸甲酯出发较大量地制备。其单取代衍生物亦可容易 地经对其进行去质子化-亲电取代而制备，环丙叉环丙烷的典型反应性能为：（1） 环丙烷环上四个亚甲基有增强了动力学酸度，易于去质子化；（2）中间双键对环 加成反应有很高活性；（3）环丙烷环上处于双键近端和远端的C-C单键可发生裂解 ；（4）在有些反应中，可同时表现出上述反应性能，介绍了环丙叉环丙烷及其衍 生物的一些反应：对中间C=C双键的[2+n]环加成反应、亲电和自由基加成反应、1 ，3-偶极环加成反应和过渡金属催化的反应。

Bicyclopropylidene-An Evolving Multifunctional Molecular Buiding Block

Synthesis and reactions of the versatile synthetic block bicyclopropylidine and its derivatives are introduced. Bicyclopropylidene can be prepared in practical scale starting from methyl cyclopropanecarboxylate. Monosubstituted derivatives are easily accessible by deprotonation-electrophilic substitution reactions. Reactivity of the highly strained bicyclopropylidene possesses the following characterics : (1) enhanced kinetic acidity as manifested by the facile deprotonation of the four methylene groups; (2) enhanced reactivity of the C= C bond; (3) C-C bond adjacent or opposite to the central C== C bond can be cleaved; (4) possible combination of these reactivities. Several typical reactions of bicyclopropylidene derivatives are described which include [2 + rc] cycloaddition reactions with the central C= C bond, electrophilic and radical reactions, 1,3-dipolar cycloadditions and transition metal catalyzed reactions.