Gold(I)-Catalyzed Intramolecular [4+2] Cycloadditions of Arylalkynes or 1,3-Enynes with Alkenes: Scope and Mechanism
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- 作者：Cristina Nieto-Oberhuber ; Patricia Pé ; rez-Galá ; n ; Elena Herrero-Gó ; mez ; Thorsten Lauterbach ; Cristina Rodrí ; guez ; Salomé ; Ló ; pez ; Christophe Bour ; Antonio Rosell&oa
- 刊名：Journal of the American Chemical Society
- 出版年：2008
- 出版时间：January 9, 2008
- 年：2008
- 卷：130
- 期：1
- 页码：269 - 279
- 全文大小：410K
- 年卷期：v.130,no.1(January 9, 2008)
- ISSN：1520-5126
文摘
The cyclizations of enynes substituted at the alkyne gives products of formal [4+2] cyclizationwith Au(I) catalysts. 1,8-Dien-3-ynes cyclize by a 5-exo-dig pathway to form hydrindanes. 1,6-Enynes withan aryl ring at the alkyne give 2,3,9,9a-tetrahydro-1H-cyclopenta[b]naphthalenes by a 5-exo-dig cyclizationfollowed by a Friedel-Crafts-type ring expansion. A 6-endo-dig cyclization is also observed in some casesas a minor process, although in a few cases, this is the major cyclization pathway. In addition to cationicgold complexes bearing bulky biphenyl phosphines, a gold complex with tris(2,6-di-tert-butylphenyl)phosphiteis exceptionally reactive as a catalyst for this reaction. This cyclization can also be carried out very efficientlywith heating under microwave irradiation. DFT calculations support a stepwise mechanism for thecycloaddition by the initial formation of an anti-cyclopropyl gold(I)-carbene, followed by its opening to forma carbocation stabilized by a interaction with the aryl ring, which undergoes a Friedel-Crafts-type reaction.