Vinylic cations from solvolysis. Part 36. Vinylation of aromatic substrates with solvolytically generated trisubstituted vinyl cations
Vinylic cations from solvolysis. Part 36. Vinylation of aromatic substrates with solvolytically generated trisubstituted vinyl cations
复制标题
溶剂分解产生的乙烯基阳离子。
DOI：
10.1021/jo00146a033
复制
发表时间：
1982
影响因子：
3.6
通讯作者：
Z. Rappoport
中科院分区：
文献类型：
--
作者：
T. Kitamura;Shinjiro Kobayashi;H. Taniguchi;Z. Rappoport
在银盐、2，6-二叔丁基-4-甲基吡啶或2，6-二叔丁基-4-甲基吡啶存在下，α-芳基-0，/3-二取代乙烯基溴化物(3a-I)高产率地进行了芳香族化合物的乙烯基化反应。三氟化银辅助反应优于四氟硼酸银辅助反应。L-苯甲基-2，2-二苯基溴乙烯反应的p+值为-4.08，具有较高的分子内选择性，k0/kp为6.2~78。认为反应是通过中间芳基乙烯基阳离子进行的，分子间和分子内的选择性是在相同的过渡状态下决定的。早期对乙烯基阳离子34的研究大多集中在它们的生成和行为的机理方面。然而，近年来，涉及中间乙烯基阳离子的反应的合成应用越来越多。其中一些反应，特别是由炔烃的亲电加成引发的反应，需要温和的条件，因为中间阳离子的高能被它们的三键前体的高能所补偿。相反，乙烯基阳离子从其乙烯基-X前驱体(X=
Vinylations of aromatic compounds by a-aryl-0,/3-disubstituted vinyl bromides (3a-i) in the presence of silver salts and 2, 6-lutidine or 2, 6-di-tert-butyl-4-methylpyridine proceed with high yields. The silver triflate assisted reaction is preferable to the silver tetrafluoroborate assisted reaction. The reaction of l-anisyl-2, 2-diphenylvinyl bromide gives a p+ value of-4.08 and high intramolecular selectivitywith k0/kp ratios of 6.2-78. It is suggested that the reaction proceeds via intermediate-arylvinyl cations and that the inter-and intramolecular selectivities are determined in the same transition state.Most of the early studies of vinyl cations3 4were con-centrated on mechanistic aspects of their generation and behavior. However, in recent years there has been an increasing number of synthetic applications of reactions involving intermediate vinyl cations. 4, 5 Some of these reactions, especially those initiated by electrophilic ad-ditions to alkynes (eg, cyclizations5®), require mild con-ditions since thehigh energy of the intermediate cations is compensated by the high energy of their triply bonded precursors. In contrast, the solvolytic generation of vinyl cations from their vinyl-X precursors (X=