Acetylenic Vinyllithiums: Consecutive Cycloisomerization−[4 + 2] Cycloaddition Reactions
作者:William F. Bailey、Nanette M. Wachter-Jurcsak、Mark R. Pineau、Timo V. Ovaska、Rachel R. Warren、Carl E. Lewis
DOI:10.1021/jo961437l
日期:1996.11.15
terminal acetylenic carbon. The highly reactive bis-exocyclic 1,3-dienes serve as precursors to polycyclic materials through subsequent Diels-Alder reaction with a wide variety of dienophiles. The consecutive exchange-cyclization-cycloaddition methodology, which can be conducted in one pot without isolation of intermediates, provides an efficient, operationally simple, and diastereoselective route to diverse
由相应的炔属乙烯基溴化物(3)通过低温锂-溴交换生成的乙炔乙烯基锂(2)在加热下环化,用水淬灭后得到异构体纯的共轭双外环1,3-二烯( 1)良品至良品。可以制备五元和六元外环二烯:炔基乙烯基锂的5-exo封闭,其通过顺式加成进行完全立体控制,得到五元外环二烯的E-异构体,耐受远端炔碳上的芳基,甲硅烷基或烷基取代基;相应的6-exo过程较不容易,似乎仅限于在末端炔碳上带有阴离子稳定取代基(例如苯基或三甲基甲硅烷基)的底物。高反应性双环外1,3-二烯通过与多种亲二烯体的随后狄尔斯-阿尔德反应,成为多环材料的前体。可以在一个罐中进行而无需分离中间体的连续交换-环化-环加成方法,为各种多环系统提供了有效,操作简单和非对映选择性的途径。