Ring Closing Enyne Metathesis: Control over Mode Selectivity and Stereoselectivity
作者:Eric C. Hansen、Daesung Lee
DOI:10.1021/ja045422d
日期:2004.11.1
3-dienes were improved by performing these reactions under ethylene atmosphere. The presence of ethylene induces a selective cross metathesis between the alkyne moiety and ethylene to generate an acyclic 1,3-diene which can undergo ring closing diene metathesis between the isolated olefin and the distal monosubstituted double bond of the 1,3-diene to generate exclusively the endo-product with high E-selectivity
闭环烯炔复分解形成 10-15 元环是通过使用酒石酸盐衍生的接头连接烯和炔亚基来实现的。发现这些底物的闭环反应的外/内选择性是环大小的函数,其中较大的环 (12-15) 选择性地产生内向产物,而较小的环 (5-11) 产生外向产物。除了 10 和 11 元环外,所得大环 1,3-二烯的 E/Z 选择性是不可预测的。然而,通过在乙烯气氛下进行这些反应,闭环的外/内模式选择性和 1,3-二烯的 E/Z 选择性都得到了改善。乙烯的存在诱导炔烃部分和乙烯之间的选择性交叉复分解生成无环 1,