B(C6F5)3-Catalyzed (Convergent) Disproportionation Reaction of Indoles,Journal of the American Chemical Society

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B(C6F5)3-Catalyzed (Convergent) Disproportionation Reaction of Indoles
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-05-18 , DOI: 10.1021/jacs.7b03534
Yuxi Han ₁ , Sutao Zhang ₁ , Jianghua He ₁ , Yuetao Zhang ₁

Affiliation

A metal-free B(C6F5)3-catalyzed approach is developed for the disproportionation reaction of a series of indoles with various hydrosilanes, without any additives such as base and production of any small molecule such as dihydrogen. This boron catalyst system also exhibits excellent catalytic performance for practical application, such as catalyst loading as low as 0.01 mol % under solvent-free conditions, and a long-life catalytic performance highlighted by a constant catalytic activity being maintained and excellent yields being achieved for the desired products over 10 sequential additions of starting materials. On the basis of characterization of key intermediates through a series of in situ NMR reactions and detailed experimental data, we proposed a reaction mechanism which illustrated pathways for the formation of different products, including both major products and byproducts. Additional control experiments were conducted to support our proposed mechanism. Understanding the mechanism enables us to successfully suppress side reactions by choosing appropriate substrates and hydrosilanes. More importantly, the use of an elevated reaction temperature for continuous oxidation of the resulting indoline to indole makes the convergent disproportionation reaction an ideal atom-economical process. Near-quantitative conversions and up to 99% yields of C3-silylated indoles were achieved for various indoles with trisubstituted silanes, Ph3SiH (2b) or Ph2MeSiH (2d).

中文翻译：

B(C6F5)3-催化（收敛）吲哚歧化反应

开发了一种不含金属的 B(C6F5)3 催化方法，用于一系列吲哚与各种氢硅烷的歧化反应，无需任何添加剂（如碱）和任何小分子（如二氢）的生产。该硼催化剂体系在实际应用中也表现出优异的催化性能，例如在无溶剂条件下催化剂负载量低至 0.01 mol%，以及通过保持恒定的催化活性和优异的产率而突出的长寿命催化性能所需的产品超过 10 次连续添加起始材料。在通过一系列原位核磁共振反应和详细的实验数据表征关键中间体的基础上，我们提出了一种反应机理，阐明了不同产物的形成途径，包括主要产品和副产品。进行了额外的控制实验以支持我们提出的机制。了解该机制使我们能够通过选择合适的底物和氢硅烷来成功抑制副反应。更重要的是，使用升高的反应温度将所得二氢吲哚连续氧化成吲哚，使收敛歧化反应成为理想的原子经济过程。对于具有三取代硅烷、Ph3SiH (2b) 或 Ph2MeSiH (2d) 的各种吲哚，实现了接近定量的转化率和高达 99% 的 C3 甲硅烷基化吲哚收率。了解该机制使我们能够通过选择合适的底物和氢硅烷来成功抑制副反应。更重要的是，使用升高的反应温度将所得二氢吲哚连续氧化成吲哚，使收敛歧化反应成为理想的原子经济过程。对于具有三取代硅烷、Ph3SiH (2b) 或 Ph2MeSiH (2d) 的各种吲哚，实现了接近定量的转化率和高达 99% 的 C3 甲硅烷基化吲哚收率。了解该机制使我们能够通过选择合适的底物和氢硅烷来成功抑制副反应。更重要的是，使用升高的反应温度将所得二氢吲哚连续氧化成吲哚，使收敛歧化反应成为理想的原子经济过程。对于具有三取代硅烷、Ph3SiH (2b) 或 Ph2MeSiH (2d) 的各种吲哚，实现了接近定量的转化率和高达 99% 的 C3 甲硅烷基化吲哚收率。

更新日期：2017-05-18

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