C-Methylation of Alcohols, Ketones, and Indoles with Methanol Using Heterogeneous Platinum Catalysts,ACS Catalysis

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C-Methylation of Alcohols, Ketones, and Indoles with Methanol Using Heterogeneous Platinum Catalysts
ACS Catalysis ( IF 11.3 ) Pub Date : 2018-02-21 00:00:00 , DOI: 10.1021/acscatal.7b04442
S. M. A. Hakim Siddiki ₁ , Abeda S. Touchy ₁ , Md. A. R. Jamil ₁ , Takashi Toyao _{1,

2} , Ken-ichi Shimizu _{1,

2}

Affiliation

A versatile, selective, and recyclable heterogeneous catalytic method for the methylation of C–H bonds in alcohols, ketones, and indoles with methanol under oxidant-free conditions using a Pt-loaded carbon (Pt/C) catalyst in the presence of NaOH is reported. This catalytic system is effective for various methylation reactions: (1) the β-methylation of primary alcohols, including aryl, aliphatic, and heterocyclic alcohols, (2) the α-methylation of ketones, and (3) the selective C3-methylation of indoles. The reactions are driven by a borrowing-hydrogen mechanism. The reaction begins with the dehydrogenation of the alcohol(s) to afford aldehydes, which subsequently undergo a condensation reaction with the nucleophile (aldehyde, ketone, or indole), followed by hydrogenation of the condensation product by Pt–H species to yield the desired product. In all of the methylation reactions explored in this study, the Pt/C catalyst exhibits a significantly higher turnover number than other previously reported homogeneous catalytic systems. Moreover, it is demonstrated that the high catalytic activity of Pt can be rationalized in terms of the adsorption energy of hydrogen on the metal surface, as revealed by density functional theory calculations on different metal surfaces.

中文翻译：

使用多相铂催化剂，用甲醇将醇，酮和吲哚进行C-甲基化

一种通用，选择性和可循环利用的非均相催化方法，是在无氧化剂的条件下，使用载有Pt的碳（Pt / C）催化剂在NaOH的存在下，用甲醇在醇，酮和吲哚中的C–H键进行甲基化的方法是报告。该催化体系对各种甲基化反应均有效：（1）伯醇（包括芳基，脂肪族和杂环醇）的β-甲基化；（2）酮的α-甲基化；（3）选择性C3-吲哚的甲基化。反应由借氢机制驱动。反应开始于将醇脱氢得到醛，然后将其与亲核试剂（醛，酮或吲哚）进行缩合反应，然后通过Pt–H物种将缩合产物氢化以生成所需的醛。产品。在这项研究中探讨的所有甲基化反应中，Pt / C催化剂的周转率均比以前报道的其他均相催化体系高得多。而且，证明了如在不同金属表面上的密度泛函理论计算所揭示的，Pt的高催化活性可以根据氢在金属表面上的吸附能而合理化。

更新日期：2018-02-21

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