Annulation of metallabenzenes: from osmabenzene to osmabenzothiazole to osmabenzoxazole.
Annulation of metallabenzenes: from osmabenzene to osmabenzothiazole to osmabenzoxazole.
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DOI：
10.1002/anie.200902738
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发表时间：
2009-08
影响因子：
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通讯作者：
Tongdao Wang;Shunhua Li;Hong Zhang;Ran Lin;Feifei Han;Yu-Mei Lin;T. Wen;H. Xia
中科院分区：
文献类型：
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作者：
Tongdao Wang;Shunhua Li;Hong Zhang;Ran Lin;Feifei Han;Yu-Mei Lin;T. Wen;H. Xia
含过渡金属的金属芳香族化合物的研究目前引起了相当大的关注。自从罗珀等人报道了第一个金属苯类的例子以来。1982年，已成功分离和表征了多种单环金属芳香族化合物。然而，稠合金属芳香族化合物的化学不太发达。已报道的大多数稠合金属芳香族化合物都是通过不饱和前体的环金属化反应来构建的。7]仅报道了一个基于苯并噻吩金属插入反应的特例。原则上，从单环金属芳烃合成稠合金属芳烃可能是另一种有效的方法；然而，到目前为止，这种可能性还没有实现。本文报道了一种基于金属苯1的分子内亲核芳香取代(SNAR)反应生成第一金属苯并恶唑2的新的环化反应。此外，我们还介绍了2向第一金属苯并恶唑4和5的转化(方案1)。现在公认的是，如果吸电子取代基与环上的离开基团(通常是卤素)垂直或平行，芳烃，特别是杂芳烃，可以进行Snar反应。最近，我们报道了金属环上含膦取代基和活性硫氰基的欧姆苯-1的合成。在该体系中，金属中心和吸电子膦基团对芳香环的电子密度有重要影响。在这一点上，化合物1有望进行分子内SNAR反应来构建新的金属芳香族化合物。带着这个想法，我们研究了欧姆苯1与MeONa/MeOH的反应，从中分离出了绿色固体欧姆苯并噻唑2(方案1)。这种新产品是空气稳定的，在室温下无论是在固体状态下还是在溶液中都可以保存几天，没有明显的分解。2的结构经X-射线衍射法确证。如图1所示，它包含一个完美的平面金属苯并噻唑单元。与整个金属苯并噻唑体系最小二乘平面的最大偏差为0.0096。正如预期的那样，OS1C1(1.954(7))和OS1C5(1.953(8))以及欧姆苯环内的CC键的长度在观察到的其他欧姆苯环的长度范围内。9]噻唑基团的C、N和C-S键长与
Research into transition-metal-containing metallaaromatics is attracting considerable current attention. Since the first example of metallabenzenes were reported by Roper et al. in 1982, a wide variety of monocyclic metallaaromatics have been successfully isolated and characterized. However, the chemistry of fused metallaaromatics is less developed. Most of the reported fused metallaaromatics were constructed by the cyclometalation of an unsaturated precursor. 7] Only one exceptional example, based on the metal insertion reaction of benzothiophene, has been reported. In principle, it may be another efficient approach to construct fused metallaaromatics from monocyclic metallaaromatics; however, such a possibility has not been realized to date. Herein, we report a novel annulation reaction leading to the first metallabenzothiazole 2 based on the intramolecular nucleophilic aromatic substitution (SNAr) reaction of metallabenzene 1. Furthermore, transformation of 2 to the first metallabenzoxazoles 4 and 5 is also presented (Scheme 1). It is now well-established that arenes, and especially heteroarenes, could undergo SNAr reaction if electron-withdrawing substituents are positioned ortho or para to the leaving group (typically a halogen) on the ring. Recently, we reported the synthesis of osmabenzene 1 bearing a phosphonium substituent and a reactive thiocyano group on the metallacycle. In this system, the metal center and the electron-withdrawing phosphonium group may exert significant influence on the electron density of the aromatic ring. In this regard, complex 1 might be expected to undergo intramolecular SNAr reactions to construct new metallaaromatic compounds. With this idea in mind, we studied the reaction of osmabenzene 1 with MeONa/MeOH, from which osmabenzothiazole 2 was isolated as a green solid (Scheme 1). This new product is air-stable and can be kept for several days without appreciable decomposition either in the solid state or in solution at room temperature. The structure of 2 has been confirmed by X-ray diffraction. As shown in Figure 1, it contains a perfectly planar metallabenzothiazole unit. The maximum deviation from the least-squares plane of the whole metallabenzothiazole system is 0.0096 . As expected, the lengths of the Os1 C1 (1.954(7) ) and Os1 C5 (1.953(8) ) and the C C bonds within the osmabenzene ring are within the range of those observed for other osmabenzenes. 9] The C N and C S bond lengths of the thiazole moiety are similar to those