Cross-coupling reaction between alcohols through sp3 C-H activation catalyzed by a ruthenium/Lewis acid system.
Cross-coupling reaction between alcohols through sp3 C-H activation catalyzed by a ruthenium/Lewis acid system.
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DOI：
10.1002/chem.200801317
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发表时间：
2008-11
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通讯作者：
Shu‐Yu Zhang;Y. Tu;Chun‐An Fan;Yi-Jun Jiang;Lei Shi;K. Cao;E. Zhang
中科院分区：
文献类型：
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作者：
Shu‐Yu Zhang;Y. Tu;Chun‐An Fan;Yi-Jun Jiang;Lei Shi;K. Cao;E. Zhang
C3 C键的形成是有机化学中分子结构和复杂性的关键和基础;使用醇的直接C3 C交叉偶联是实现这一目标的理想反应之一，因为它不仅产生新的C3 C键[1-6]，而且还显示原子经济和环境友好的化学。[7]在碱性条件下，过渡金属催化的直接利用醇类的C2 H4-C交叉偶联反应已经取得了一些开创性的工作。[6]例如，仲醇与伯醇的季铵盐催化的[8]/碱介导的交叉偶联仅提供b-烷基化仲醇[Eq. (1)]其中“氢自转移过程”是基于串联氧化-缩合-还原过程提出的。[9]然而，最近我们发现，在刘易斯酸BF 3·OEt 2存在下，由[RuCl 2 ACHTUNGTRENNUNG（PPh 3）3]催化的上述相同类型的醇的偶联反应，如反应式（2）所示，主要得到完全不同的异构产物4-苯基-2-丁醇，尽管产率为42%，[10]而不是上面得到的反应式（1）中的b-烷基化产物。据我们所知，这构成了关于伯醇2与脂族醇1通过过渡金属催化的C12 C交叉偶联的化学选择性分子间α-烷基化的第一个实施例（方案1）。与我们以前报道的烯烃/醇偶联反应[4]相比，本反应的显著区别和优点包括：1）使用易得的醇，特别是叔醇作为绿色材料代替烯烃; 2）发现了一种新的有效的醇间偶联催化剂[RuCl_2-ACHTUNGTRENNUNG（PPh_3）_3]，但其在先前的烯烃/醇偶联中不太有效; 3）以良好至优异的产率形成作为产物的官能化仲醇。这种Ru催化的/刘易斯酸促进的交叉偶联证明了以环境友好的方式直接从简单醇到高级醇的新型合成转化。在这里，我们详细介绍了我们的实验结果。最初，为了从容易获得和处理的醇开始广泛探索上述新的转化，我们选择1，1-二苯基乙醇（1a）和乙醇（2a）作为我们初步研究的底物，用各种过渡-[a] S. Y.张玉- Q. Tu，C.- A.范，Y.-江湖，澳-地Shi，K. Cao，E.兰州大学应用有机化学国家重点实验室，兰州大学化学系，兰州730000传真：（+ 86）931-8915557电子邮箱：salq @ lzu. edu. cn本文的辅助信息可在http：//dx下的WWW上获得。doi。org/10.1002/chem.200801317。
The CÀC bond formation is pivotal and fundamental to molecular architecture and complexity in organic chemistry; the direct CÀC cross-coupling using alcohols is one of ideal reactions for achieving this goal, since it not only makes new CÀC bonds,[1–6] but also displays atom-economic and environmentally benign chemistry.[7] Some pioneering work on the transition-metal-catalyzed CÀC cross-coupling directly utilizing alcohols has been made extensively under basic conditions.[6] For example, ruthenium-catalyzed [8]/base-mediated cross-coupling of secondary alcohols with primary alcohols exclusively afforded b-alkylated secondary alcohols [Eq.(1)],[6a] wherein the “hydrogen autotransfer process” was proposed on the basis of the tandem oxidation-condensation-reduction processes.[9] However, most recently we found that the coupling reaction of the same type of above-mentioned alcohols catalyzed by [RuCl2ACHTUNGTRENNUNG (PPh3) 3] in the presence of Lewis acid BF3· OEt2, as shown in Equation (2), mainly delivered a totally different isomeric product 4-phenyl-2-butanol, despite in moderate yield of 42%,[10] instead of the above-obtained b-alkylation product in Equation (1). To our knowledge, this constitutes the first example concerning the chemoselective intermolecular a-alkylation of primary alcohols 2 with aliphatic alcohols 1 through transition-metal-catalyzed CÀC cross-coupling (Scheme 1). In comparison with our previous report concerning the olefin/alcohol coupling reaction,[4] the significant difference and advantage of the present sequence include the following: 1) employment of easily available alcohols, especially tertiary alcohols, as green materials instead of alkenes; 2) discovery of new effective catalyst,[RuCl2-ACHTUNGTRENNUNG (PPh3) 3], for the cross-coupling between alcohols, but which is less effective in previous alkene/alcohol coupling; 3) formation of functionalized secondary alcohols as product in good to excellent yields. This Ru-catalyzed/Lewis acid promoted cross-coupling demonstrates a novel synthetic transformation directly from simple alcohols to advanced alcohols in an environmentally benign fashion. Herein, we present our experimental results in detail. Initially to widely explore the above novel transformation commencing from easily available and handled alcohols, we selected 1, 1-diphenylethanol (1a) and ethanol (2a) as substrates for our initial investigation with various transition-[a] S.-Y. Zhang, Y.-Q. Tu, C.-A. Fan, Y.-J. Jiang, L. Shi, K. Cao, E. Zhang State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University Lanzhou 730000 (PR China) Fax:(+ 86) 931-8915557 E-mail: tuyq@ lzu. edu. cn Supporting information for this article is available on the WWW under http://dx. doi. org/10.1002/chem. 200801317.