1,2-Bis(trifluoromethyl)ethene-1,2-dicarbonitrile and Vinyl Ethers: Cyclic Ketene Imines on the Pathway to 1 : 2 Cycloadducts
作者:Gonzalo Urrutia Desmaison、Rolf Huisgen、Heinrich Nöth
DOI:10.1002/hlca.201200047
日期:2012.5
to vinyl ether, the pathways leading to mono‐ and bis‐adducts must compete on the level of the intermediate l,4‐zwitterions 1 and 2. The latter either cyclize to the cyclobutanes 3 or to six‐membered cyclic ketene imines 8 which accept a second molecule of vinyl ether to yield the bis‐adducts 6. The occurrence of the highly strained ketene imines 8 gains credibility by comparison to stable seven‐membered
(E)-和(Z)-1,2-双(三氟甲基)乙烯1,2-二甲腈(BTE;(= E)-和(Z)-1,2-双(三氟甲基)丁-2-烯腈)与过量的用作溶剂的甲基乙烯基醚反应,并提供1:2加合物6(54%)和环丁烷3作为1:1加合物(41%)。四个非对映异构双加合物6((E)-和(Z)-BTE的不同比率)是1-氮杂双环[4.2.0] oct-5-ene的衍生物;X射线分析和19 F-NMR光谱揭示了它们的结构。自环丁烷3由于对乙烯基醚具有抗性,因此导致单加合物和双加合物的途径必须在中间体1,4两性离子1和2的水平上竞争。后者要么环化成环丁烷3,要么环化成六元环烯酮亚胺8,后者接受第二个乙烯基醚分子以生成双加合物6。与最近报道的稳定的七元环烯酮亚胺相比,高度紧张的烯酮亚胺8的出现获得了信誉。