Hansen Eric C, Lee Daesung
Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
J Am Chem Soc. 2004 Nov 24;126(46):15074-80. doi: 10.1021/ja045422d.
Ring closing enyne metathesis to form 10-15-membered rings was achieved by using a tartrate-derived linker to attach ene and yne subunits. The exo/endo selectivity of the ring closure reaction of these substrates was found to be a function of ring size, whereby larger rings (12-15) give endo-products selectively, while smaller rings (5-11) give exo-products. The E/Z selectivity of the resultant macrocyclic 1,3-dienes was not predictable except for 10- and 11-membered rings. However, both the exo/endo-mode selectivity of the ring closure and the E/Z selectivity of the 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.
通过使用源自酒石酸盐的连接基连接烯基和炔基亚基，实现了关环烯炔复分解反应以形成10至15元环。发现这些底物的关环反应的外型/内型选择性是环大小的函数，其中较大的环（12至15元）选择性地生成内型产物，而较小的环（5至11元）生成外型产物。除了10元和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，关环的外型/内型模式选择性和1,3-二烯的E/Z选择性都得到了改善。乙烯的存在诱导炔基部分与乙烯之间发生选择性交叉复分解，生成无环1,3-二烯，该无环1,3-二烯可在孤立的烯烃与1,3-二烯的远端单取代双键之间进行关环二烯复分解，以高E选择性专一性地生成内型产物。
