Cross [2 + 2] Cycloaddition of Bicyclic Alkenes with Alkynes Mediated by Cobalt Complexes: A Facile Synthesis of Cyclobutene Derivatives
作者:Kuan Cheng Chao、Dinesh Kumar Rayabarapu、Chun-Chih Wang、Chien-Hong Cheng
DOI:10.1021/jo010609y
日期:2001.12.1
Bicyclic alkenes 1a-e and 5 undergo [2 + 2] cycloaddition with a variety of alkynes PhC(triple bond)CPh, (TMS)C(triple bond)CH, HC(triple bond)C(CH(3))(2)OH, (TMS)C(triple bond)CCO(2)Et, PhC(triple bond)CCH(3), C(2)H(5)C(triple bond)CC(2)H(5), CH(3)C(triple bond)CC(3)H(7), and CH(3)C(triple bond)CC(2)H(5) in the presence of Co(PPh(3))(2)I(2), PPh(3), and Zn powder in toluene to afford the corresponding
双环烯烃1a-e和5与各种炔烃PhC(三键)CPh,(TMS)C(三键)CH,HC(三键)C(CH(3))(2)进行[2 + 2]环加成反应)OH,(TMS)C(三键)CCO(2)Et,PhC(三键)CCH(3),C(2)H(5)C(三键)CC(2)H(5),CH (3)C(三键)CC(3)H(7)和CH(3)C(三键)CC(2)H(5)在Co(PPh(3))(2)I存在下(2),PPh(3)和Zn粉在甲苯中制得相应的外环丁烯衍生物3a-m,6和8a-g,具有相当好的收率。该环加成反应的产率对所用的钴催化剂,溶剂,配体和温度高度敏感。提出了一种涉及金属环戊烯中间体的机理来解释这种钴催化的环化反应。