A Nickel-Catalyzed Benzannulation Approach to Aromatic Boronic Esters
A Nickel-Catalyzed Benzannulation Approach to Aromatic Boronic Esters
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DOI：
10.1002/anie.201007598
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发表时间：
2011-01-01
影响因子：
16.6
通讯作者：
Harrity, Joseph P. A.
中科院分区：
文献类型：
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作者：
Auvinet, Anne-Laure;Harrity, Joseph P. A.
苯环化反应是组装高度取代芳香族化合物的最有效、最直接的方法之一。[1]尽管如此，这种策略提供了一些相当大的挑战，涉及化学选择性和区域选择性。关于利用此类反应生产合成有用的有机化合物，芳族硼酸代表重要的目标，因为它们被广泛认为是合成化学中最有用和通用的中间体之一。[2]事实上，这类化合物已经通过涉及过渡金属催化[3]和周环[4]过程的苄环化技术获得。我们在这一领域的初步工作表明，Dötz苄环化反应可以以良好的产率和优异的区域控制水平获得醌硼酸酯。[5]由于醌硼酸可以作为生物活性醌的前体，[6]并且最近已经成为区域和立体控制的Diels-Alder反应的有用底物，[7]这种技术具有一些显着的合成潜力。然而，与Dötz benzannulation反应中需要化学计量的有机铬试剂相关的缺点促使我们寻找过渡金属催化的方法。如方案1中所概述，Cr-介导的苄环化反应可以设想为Cr-模板化的烯酮电环化。我们认为金属模板乙烯基烯酮[4+ 2]环加成是含氧芳族硼酸酯体系的替代策略。的确，
Benzannulation reactions are one of the most efficient and direct methods for assembling highly substituted aromatic compounds.[1] Nonetheless, this strategy provides a number of considerable challenges that relate to chemoselectivity and regioselectivity. With regard to exploiting such reactions for the production of synthetically useful organic compounds, aromatic boronic acids represent an important target as they are widely acknowledged as being amongst the most useful and versatile intermediates in synthetic chemistry.[2] Indeed, such compounds have been accessed by benzannulation techniques involving transition metal catalysis [3] and pericyclic [4] processes.Our preliminary work in this area showed that the Dötz benzannulation reaction could be exploited to access quinone boronic esters in good yield and with excellent levels of regiocontrol.[5] As quinone boronic acids can serve as precursors to bioactive quinones,[6] and have recently emerged as useful substrates for regio-and stereocontrolled Diels–Alder reactions,[7] this technique held some significant synthetic potential. However, drawbacks associated with the requirement for a stoichiometric organochromium reagent in the Dötz benzannulation reaction prompted us to search for a transition metal catalyzed approach. As outlined in Scheme 1, the Cr-mediated benzannulation reaction can be envisaged to be a Cr-templated ketene electrocyclization. We considered a metal-templated vinylketene [4+ 2] cycloaddition to be an alternative strategy to oxygenated aromatic boronic ester systems. Indeed, such