CO fixation to stable acyclic and cyclic alkyl amino carbenes: Stable amino ketenes with a small HOMO-LUMO gap
CO fixation to stable acyclic and cyclic alkyl amino carbenes: Stable amino ketenes with a small HOMO-LUMO gap
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DOI：
10.1002/anie.200600987
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Bertrand, Guy
中科院分区：
文献类型：
--
作者：
Lavallo, Vincent;Canac, Yves;Bertrand, Guy
活性中间体在现代化学中起着核心作用。[1]自1900年起，贡伯格发现了一种稳定的自由基，[2]许多被认为寿命太短而无法观察的物种已经被分离出来。稳定版本的活性中间体的可获得性使人们能够更好地控制它们的反应性，并更好地了解化学反应的机理。更重要的是，已经发现了这些物种的新应用，例如，成功地将稳定的卡宾用作过渡金属催化剂的配体[3]，甚至用作有机催化剂。[4]仍然有几类具有合成重要性的活性中间体，它们的制备因认为它们不能存在而受阻，或躲避了研究人员的合成技能。由于具有很高的反应活性，烯类化合物是合成有机化学中的关键中间体，甚至在工业上也有应用。[5-7]尽管早在20世纪初就分离出了二苯基烯酮，但[8]大多数烯类化合物本质上是不稳定的，不能分离。[5]计算预测，σ-吸电子取代基以及π-供体基团会使烯类化合物不稳定。[9]相应地，烷氧基烯类化合物只能在低温下或用快速光谱方法进行表征，[10]而氨基酮类化合物从未被观察到。
Reactive intermediates play a central role in modern chemistry.[1] Since 1900, and the discovery by Gomberg of a stable radical,[2] many species that were thought to be too shortlived for observation have been isolated. The availability of stable versions of reactive intermediates has allowed for a superior control of their reactivity and a better understanding of the mechanism of chemical reactions. Even more importantly, new applications of these species have been found, for example, the successful use of stable carbenes as ligands for transition-metal catalysts,[3] and even as organic catalysts.[4]There are still several families of synthetically important reactive intermediates, the preparation of which has been impeded by the belief that they are incapable of existence, or has eluded the synthetic skills of investigators. Because of their very high reactivity, ketenes are key intermediates in synthetic organic chemistry, and have even found industrial applications.[5–7] Despite the isolation of diphenylketene as early as the beginning of the 20th century,[8] most ketenes are intrinsically unstable and cannot be isolated.[5] Calculations have predicted that σ-electron-withdrawing substituents, as well as π-donor groups destabilize ketenes.[9] Accordingly, alkoxy ketenes have only been characterized at low temperature or by fastspectroscopic methods,[10] whereas amino ketenes have never been observed.[11]