Ruthenium-Mediated Cycloaromatization of Acyclic Enediynes and Dienynes at Ambient Temperature

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• 作者：Joseph M. O'Connor ; Seth J. Friese ; and Mark Tichenor
• 刊名：Journal of the American Chemical Society
• 出版年：2002
• 出版时间：April 10, 2002
• 年：2002
• 卷：124
• 期：14
• 页码：3506 - 3507
• 全文大小：48K
• 年卷期：v.124,no.14(April 10, 2002)
• ISSN：1520-5126

文摘

The ruthenium(II) cation, [Cp*Ru(NCMe)<SUB>3]OTf (4), triggers the Bergman cycloaromatization of acyclic endiynes at room temperature in THF solvent. Treatment of 1,2-di(1-alkynynyl)cyclopentenes (13-Me, alkynyl = propynyl; 13-Prⁿ, alkynyl = pentynyl; 13-Buⁱ, alkynyl = 4-methyl-pent-1-ynyl) with 4 in THF solvent at room temperature gives rise to the ruthenium arene complexes: [Cp*Ru{(3a,4,5,6,7,7a-s/gifchars/eta.gif" BORDER=0 >)-2,3-dihydro-5,6-dialkyl-1H-indene}]OTf (15-Me, alkyl = methyl, 64% yield; 15-Prⁿ, alkyl = n-propyl, 73% yield; 15-Buⁱ, alkyl = 4-methyl-1-pentynyl, 88% yield). In a similar fashion, the room-temperature reaction of 4 with 1-ethynyl-2-(1-propynyl)cyclopentene (11) and [2-(1-propynyl)-1-cyclopenten-1-yl]trimethylsilane (14) leads to the formation of [Cp*Ru{(3a,4,5,6,7,7a-s/gifchars/eta.gif" BORDER=0 >)-2,3-dihydro-5-methyl-1H-indene}]OTf (12, 92% yield) and [Cp*Ru{(3a,4,5,6,7,7a-s/gifchars/eta.gif" BORDER=0 >)-2,3-dihydro-6-methyl-1H-inden-5-yl)trimethylsilane}]OTf (16, 77% yield), respectively. The bis(TMS)-substituted enediyne (1-cyclopentene-1,2-diyldi-2,1-ethynediyl)bis(trimethylsilane) (9-TMS) and 4 underwent reaction at 100 s/entities/deg.gif">C to give [Cp*Ru{(3a,4,5,6,7,7a-s/gifchars/eta.gif" BORDER=0 >)-2,3-dihydro-1H-inden-5-yl)trimethylsilane}]OTf (10, 69% yield). Deuterium-labeling studies rule out a mechanism that involves a ruthenium-vinylidene intermediate, and provide support for the involvement of a p-benzyne intermediate. In a similar fashion, complex 4 is shown to trigger the cycloaromatization of the conjugated dienyne, 1-ethenyl-2-(1-pentynyl)cyclopentene (19), at room temperature in chloroform-d₁ solvent to give [Cp*Ru{(3a,4,5,6,7,7a-s/gifchars/eta.gif" BORDER=0 >)-2,3-dihydro-5-(1-propyl)-1H-indene}]OTf (20, 96% yield), with no deuterium enrichment. In the absence of ruthenium the thermal cyclization reactions of unsubstituted acyclic enediynes (Bergman cycloaromatization) and acyclic conjugated dienynes (Hopf cyclization) typically require elevated temperatures (150-250 s/entities/deg.gif">C). Complexes 10 and 15-Prⁿ were characterized structurally by X-ray crystallography.