Palladium-catalyzed [2+2+2] cocyclotrimerization of benzynes with bicyclic alkenes: An efficient route to anellated 9,10-dihydrophenanthrene derivatives and polyaromatic compounds
Palladium-catalyzed [2+2+2] cocyclotrimerization of benzynes with bicyclic alkenes: An efficient route to anellated 9,10-dihydrophenanthrene derivatives and polyaromatic compounds
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DOI：
10.1021/jo048702k
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发表时间：
2004-11-26
影响因子：
3.6
通讯作者：
Cheng, CH
中科院分区：
文献类型：
--
作者：
Jayanth, TT;Jeganmohan, M;Cheng, CH
介绍了一种由磷钯配合物催化的双环烯烃和苯共环三聚化反应，得到相应的降冰片烷化9,10-二对菲衍生物的有效方法。双环烯烃1a-i在PdCl2(PPh3)(2)存在下，与前体2a-d[2-（三甲基硅基）苯基三氟酸酯（2a）， 4,5-二甲基-2-（三甲基硅基）苯基三氟酸酯（2b）， 6-（三甲基硅基）-2,3-二氢- 1h -5-独立基三氟酸酯（2c）， 4-甲基-2-（三甲基硅基）苯基三氟酸酯（2d）]生成的苯在室温下在乙腈中进行[2 + 2 + 2]共环三聚化反应，以中至优异的产率生成9,10-二氢菲衍生物3a-r。氧和氮杂环烯烃的[2 + 2 + 2]共环三聚化产物可通过简单的路易斯酸介导脱氧芳构化反应合成多芳烃取代苯并[b]三苯（8a-f），收率较高。此外，[2 + 2 + 2]产物容易发生Diels-Alder反应，为取代菲的合成和异苯并呋喃的生成提供了新方法。提出了催化[2 + 2 + 2]环加成反应的合理机理。
An efficient method for the cocyclotrimerization of bicyclic alkenes and benzynes catalyzed by palladium phosphine complexes to give the corresponding norbornane anellated 9,10-dihydrophenanthrene derivatives is described. Bicyclic alkenes 1a-i undergo [2 + 2 + 2] cocyclotrimerization with benzynes generated from precursors 2a-d [2-(trimethylsilyl)phenyl triflate (2a), 4,5-dimethyl-2-(trimethylsilyl)phenyl triflate (2b), 6-(trimethylsilyl)-2,3-dihydro-1H-5-indenyl triflate (2c), 4-methyl-2-(trimethylsilyl)phenyl triflate (2d)] in the presence of PdCl2(PPh3)(2) in acetonitrile at ambient temperature to yield anellated 9,10-dihydrophenanthrene products 3a-r in moderate to excellent yields. The [2 + 2 + 2] cocyclotrimerization products from oxa- and azabicyclic alkenes can be applied for the synthesis of polyaromatics, substituted benzo[b]triphenylenes (8a-f), via a simple Lewis acid mediated deoxyaromatization in good yields. In addition the [2 + 2 + 2] products undergo retro Diels-Alder reaction readily, providing a new method for the synthesis of substituted phenanthrenes and for generating isobenzofurans. A plausible mechanism is proposed to account for the catalytic [2 + 2 + 2] cycloaddition reaction.