Oxidative cross-coupling of arenes induced by single-electron transfer leading to biaryls by use of organoiodine(III) oxidants
Oxidative cross-coupling of arenes induced by single-electron transfer leading to biaryls by use of organoiodine(III) oxidants
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DOI：
10.1002/anie.200704495
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Kita, Yasuyuki
中科院分区：
文献类型：
--
作者：
Dohi, Toshifumi;Ito, Motoki;Kita, Yasuyuki
biaryls的科学重要性和价值很容易从这些化合物作为液晶、有机器件和导体、染料、金属催化剂配体，甚至在医学领域的广泛工业应用中得到认识，因为这些结构在生物活性、自然产生的产品中无处不在最重要的是，许多合成工作已经致力于这些双芳基化合物的实际获取和合成过程中具体问题的解决。[2,3]考虑到目前减少合成步骤数量和废物产生的压力，合成联芳基化合物的最理想和最有吸引力的途径似乎是两个非活化芳烃的直接氧化偶联。[4 - 9]强酸中的重金属氧化剂（如VV、MnIII、MoV、FeIII、TlIII和PbIV）、[4]硝酸基氧化剂、[5]和阳极氧化[6]通常用于直接获得联芳基化合物。最近，高价碘（III）试剂[7]和钯催化剂和氧化剂[8]的组合已被使用。然而，这些方法中的大多数仍然具有有限的应用，因为难以获得交叉偶联产物，因为会发生不希望的均匀偶联二聚体的竞争性形成（Scheme1）。为了解决这个问题，Stuart和Fagnou b[10]以及Canesi和同事b[11]提出了通过利用氮官能团的双电子氧化活化选择性吲哚或苯胺交叉偶联的解决方案。尽管有一些前所未有的直接交叉耦合的例子，[12,13]仍然强烈要求进一步开发新的直接交叉耦合系统，包括可选择的机械概念，允许其他结构类型的耦合组合。在此，我们报告了一种新的萘和亚甲基交叉偶联的直接氧化方法，后者代表了最终亲核伙伴的选择。这是由单电子转移（SET）氧化诱导的非官能化芳烃之间选择性交叉偶联的第一个成功例子，利用高价碘（III）试剂产生芳香阳离子自由基中间体的不寻常选择性。
The scientific importance and value of biaryls are easily recognized from the broad industrial utilization of these compounds as versatile building blocks for liquid crystals, organic devices and conductors, dyes, ligands for metal catalysts, and even in medical fields, since these structures are ubiquitous in biologically active, naturally occurring products.[1] Above all, many synthetic efforts have already been devoted to the practical access of these biaryls and the resolution of specific problems during their syntheses.[2, 3] Considering current pressure to reduce the number of synthetic steps and the production of waste, the most ideal and attractive route to biaryl compounds appears to be the direct oxidative coupling of two non-activated arenes.[4–9] Heavy-metal oxidants (ie VV, MnIII, MoV, FeIII, TlIII, and PbIV) in strong acids,[4] nitric acid based oxidants,[5] and anodic oxidations [6] have typically been employed for direct access to biaryl compounds. More recently, hypervalent iodine (III) reagents [7] and combinations of palladium catalysts and oxidants [8] have been used. However, the majority of these methods still have limited applications owing to the difficulty in obtaining cross-coupling products, because the undesired competitive formation of homocoupling dimers occurs (Scheme1). To address this issue, solutions have recently been provided by Stuart and Fagnou [10] and by Canesi and coworkers [11] regarding selective indole or aniline cross-couplings by two-electron oxidative activation utilizing the nitrogen functionalities. Despite a few examples of unprecedented direct cross-couplings,[12, 13] there remains a strong demand for the further development of new direct crosscoupling systems involving alternative mechanistic conceptions, which permit other structural types of coupling combinations. Herein, we report a novel direct oxidative approach for the cross-coupling of naphthalenes and mesitylenes, with the latter representing a selection of the ultimate nucleophilic partners. This is the first successful example of selective cross-coupling between unfunctionalized arenes induced by single-electron transfer (SET) oxidation, taking advantage of the unusual selectivity for the generation of aromatic cation radical intermediates using hypervalent iodine (III) reagents.