Gold-Catalyzed Cyclization/Oxidative [3+2]Cycloadditions of 1,5-Enynes with Nitrosobenzenes without Additional Oxidants
Gold-Catalyzed Cyclization/Oxidative [3+2]Cycloadditions of 1,5-Enynes with Nitrosobenzenes without Additional Oxidants
复制标题
DOI：
10.1002/anie.201209850
复制
发表时间：
2013-01-01
影响因子：
16.6
通讯作者：
Liu, Rai-Shung
中科院分区：
文献类型：
--
作者：
Chen, Chun-Hao;Tsai, Yen-Ching;Liu, Rai-Shung
金属催化的1，9-烯炔（n= 5-7）与小分子的[2+ 2+ m]环加成反应（m= 1-3）是获得复杂杂环和碳环的有力工具。[1，2]这些反应很有吸引力，因为它们的机制可以通过使用不同的金属配合物来改变。如方案1所示，低价金属物质与这些烯炔反应，最初形成二环烯烃中间体（Ia），[3]而金（I）催化剂生成具有共振结构的环丙基金卡宾Ib，即烯基金碳阳离子Ib '。[4]我们寻求一种新的催化1，n-烯炔的[2+ 2+ m]环加成反应，以在所得环加成物上产生额外的官能度。虽然亚硝基苯的催化环加成反应已被深入研究，[5，6]我们知道没有关于亚硝基物种与1，n-烯炔（n= 5-7）的环加成反应的报道。[6]本文报道了金催化的1，5-烯炔与亚硝基苯的环化/氧化[3+ 2]环加成反应。值得注意的是，亚硝基苯不仅提供两个原子的结构单元，而且还导致炔氧化。这种反应模式在金属催化的1，n-烯炔的环加成反应中是前所未有的，这种氧化环加成反应是通过1，5-烯炔1a（1当量）与亚硝基苯的反应实现的5当量）和[P（tBu）2]。（邻联苯基）AuCl]/AgNTf 2（5摩尔%）在1，2-二氯乙烷中的溶液（DCE; 258 ℃，24 h），得到21%产率的氧化环加合物3a，以及70%产率的环异构化产物4a（表1，条目1）。[7]的
Metal-catalyzed [2+ 2+ m] cycloadditions (m= 1–3) of 1, nenynes (n= 5–7) with small molecules are powerful tools for accessing complicated hetero-and carbocycles.[1, 2] These reactions are appealing because their mechanisms can be altered by using different metal complexes. As shown in Scheme 1, low-valent metal species react with these enynes to form metallocycloalkene intermediates (Ia) initially,[3] whereas gold (I) catalysts generate the cyclopropyl gold carbene Ib which has a resonance structure, that is, the alkenylgold carbocation Ib’.[4] We sought a new catalytic [2+ 2+ m] cycloaddition of 1, n-enynes to generate an additional functionality on the resulting cycloadducts. Although catalytic cycloadditions of nitrosobenzenes have been intensively studied,[5, 6] we are aware of no report on the cycloaddition of nitroso species with 1, n-enynes (n= 5–7).[6] We report herein the gold-catalyzed cyclization/oxidative [3+ 2] cycloadditions of 1, 5-enynes with nitrosobenzenes. Notably, nitrosobenzenes not only provide two-atom building units, but also lead to the alkyne oxidation. Such a reaction pattern is unprecedented in metal-catalyzed cycloadditions of 1, n-enynes.This oxidative cycloaddition was realized with the treatment of the 1, 5-enyne 1a (1 equiv) with nitrosobenzene (2a; 1.5 equiv) and [P (tBu) 2 (o-biphenyl) AuCl]/AgNTf2 (5 mol%) in 1, 2-dichloroethane (DCE; 258C, 24 h) to give the oxidative cycloadduct 3a in 21% yield, together with the cycloisomerization product 4a in 70% yield (Table 1, entry 1).[7] The