Diels鈥揂lder Reactions of 9-Ferrocenyl- and 9,10-Diferrocenylanthracene: Steric Control of 9,10- versus 1,4-Cycloaddition

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• 作者：Kirill Nikitin ; Helge M眉ller-Bunz ; Michael J. McGlinchey
• 刊名：Organometallics
• 出版年：2013
• 出版时间：October 28, 2013
• 年：2013
• 卷：32
• 期：20
• 页码：6118-6129
• 全文大小：685K
• 年卷期：v.32,no.20(October 28, 2013)
• ISSN：1520-6041

文摘

Cycloadditions of benzynes, N-methyl- or N-phenylmaleimide, dimethyl acetylenedicarboxylate, and benzoquinone to 9-ferrocenylanthracene (1) and 9,10-diferrocenylanthracene (2) are described. Benzyne and 3-fluorobenzyne add to 1 and 2 to form the corresponding 9-ferrocenyl- or 9,10-diferrocenyltriptycenes; in contrast, bulkier benzynes such as 3-trifluoromethylbenzyne preferentially add to 2 across C₁ and C₄ to form 6,11-diferrocenyl-5,12-etheno-5,12-dihydrotetracenes. The maleimides undergo Diels鈥揂lder reactions with 1 to form the 9-ferrocenylbarrelenes 10 and 11, but cycloaddition to 2 occurs not only across C₉ and C₁₀ to form the barrelene 13 but also across C₁ and C₄ to yield ethenoanthracenes as both endo and exo adducts, 14 and 15, respectively. Likewise, DMAD forms 11,12-dicarbomethoxy-9-ferrocenylbarrelene (16) with 1 but reacts with 2 by addition across C₁ and C₄ to form 17. Hydrolysis of 16 cleaves only the ester distant from the ferrocenyl group. Treatment of the Diels鈥揂lder adduct 20 of 9-ferrocenylanthracene (1) and benzoquinone with base and RX (R = Me, Et, CH₂OMe, CH₂CO₂Me) yields the corresponding 1,4-dialkoxy-9-ferrocenyltriptycenes 22鈥?b>25. The factors influencing the regiochemistry of the cycloadditions are discussed, and several examples of each reaction type have been characterized by X-ray crystallography.