Cyclobutadiene: The antiaromatic paradigm?
Cyclobutadiene: The antiaromatic paradigm?
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DOI：
10.1002/anie.200602279
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Bally, Thomas
中科院分区：
文献类型：
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作者：
Bally, Thomas
过去 40 年来，可能没有任何其他单一分子能够像环丁二烯 (CBD) 那样始终如一地让实验和理论化学家如此着迷。平均而言，在此时间跨度内每年都会出现 16 篇以某种形式涉及母体化合物 C4H4 的出版物和 40 篇涉及一般环丁二烯的出版物，而且可能还有更多关于衍生物和金属络合物的出版物。没有迹象表明人们对 CBD 的兴趣即将减弱，因为每年的论文数量最多出现在 2000 年和 2002 年，并且在过去五年中，《化学评论》的两期完整专题都大量提及 CBD，都致力于芳香性/反芳香性 [1] 和定位/离域化问题，[2] 即 CBD 辩论的核心主题。最近，首次直接且相当准确地测定了生成焓Kass 小组已经实现了 CBD 的研究。[3, 4] 因此，他们为反芳香性热化学后果的讨论提供了坚实的基础，我借此机会反思该领域的最新发展，并指出由此产生的讨论充满的陷阱。尽管在开头段落中记录了许多伟大的活动，但围绕这个迷人的分子有许多神话，其中大部分与其 π 电子的离域程度和/或反芳香性程度有关。这是
There is probably no other single molecule that has fascinated experimental and theoretical chemists so consistently over the past 40years as has cyclobutadiene (CBD). On average, 16 publications which deal, in one form or another, with the parent compound C4H4 and 40 which deal with cyclobutdienes in general have appeared in every year of this time span, and there are probably many more on derivatives and metal complexes. There is no sign that interest in CBD is about to wane, as the highest number of papers per year appeared in 2000 and 2002, and in the last five years two entire thematic issues of Chemical Reviews, both with many references to CBD, were dedicated to issues of aromaticity/antiaromaticity [1] and localization/delocalization,[2] that is, topics that are central to the debate on CBD.Recently the first direct and reasonably accurate determination of the enthalpy of formation of CBD has been achieved by the group of Kass.[3, 4] Thus they have provided a solid foundation for the discussion on the thermochemical consequences of antiaromaticity, and I take this occasion to reflect on recent developments in this field and to point out the pitfalls with which the resulting discussion is fraught. In spite of the great activity documented in the opening paragraph, many myths surround this fascinating molecule, most of which relate to the extent of delocalization of its π electrons and/or the degree of antiaromaticity. It is