| 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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MedLine Citation:
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PMID: 15549819 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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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 PdCl(2)(PPh(3))(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. |
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Authors:
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Thiruvellore Thatai Jayanth; Masilamani Jeganmohan; Chien-Hong Cheng |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: The Journal of organic chemistry Volume: 69 ISSN: 0022-3263 ISO Abbreviation: J. Org. Chem. Publication Date: 2004 Nov |
Date Detail:
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Created Date: 2004-11-19 Completed Date: 2005-01-13 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985193R Medline TA: J Org Chem Country: United States |
Other Details:
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Languages: eng Pagination: 8445-50 Citation Subset: - |
Affiliation:
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Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 30013, ROC. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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