A Strain Induced Change of Mechanism from a [2 + 2 + 2] to a [2 + 1 + 2 + 1] Cycloaddition Reaction

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• 作者：Anne-Florence Tran-Van ; Silas G枚tz ; Markus Neuburger ; Hermann A. Wegner
• 刊名：Organic Letters
• 出版年：2014
• 出版时间：May 2, 2014
• 年：2014
• 卷：16
• 期：9
• 页码：2410-2413
• 全文大小：301K
• 年卷期：v.16,no.9(May 2, 2014)
• ISSN：1523-7052

文摘

While investigating the [2 + 2 + 2] cycloaddition as a tool to build up strained oligophenyl systems with a diyne-ethylene glycol macrocyle, a surprising change of mechanism was observed. Instead of the expected [2 + 2 + 2] para-terphenyl, the ortho-terphenyl product explained by a formal [2 + 1 + 2 + 1] cycloaddition was formed. An 畏⁴-coordinated metal-cyclobutadiene is proposed as the key structure in the catalytic cycle, which is formed to release the induced strain. The optical properties of the ortho-terphenyl products have been measured as well as the coordination ability of Na⁺ and K⁺.