C-Methylation of Alcohols, Ketones, and Indoles with Methanol Using Heterogeneous Platinum Catalysts
C-Methylation of Alcohols, Ketones, and Indoles with Methanol Using Heterogeneous Platinum Catalysts
复制标题
使用多相铂催化剂用甲醇对醇、酮和吲哚进行 C-甲基化
DOI：
10.1021/acscatal.7b04442
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发表时间：
2018
期刊：
影响因子：
12.9
通讯作者：
Shimizu Ken-ichi
中科院分区：
文献类型：
--
作者：
Siddiki S. M. A. Hakim;Touchy Abeda S.;Jamil Md. A. R.;Toyao Takashi;Shimizu Ken-ichi
报道了一种多用途、选择性和可回收的非均相催化方法，用于醇、酮和吲哚中的C-H键与甲醇在无氧化剂条件下在NaOH存在下使用载铂碳（Pt/C）催化剂的甲基化。该催化体系对各种甲基化反应都是有效的：（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，以及（3）吲哚的选择性C3-甲基化。这些反应是由双氢机制驱动的。反应开始于醇的脱氢以得到醛，其随后经历与亲核试剂（醛、酮或吲哚）的缩合反应，然后通过Pt-H物质氢化缩合产物以得到所需产物。在本研究中探索的所有甲基化反应中，Pt/C催化剂表现出比其他先前报道的均相催化体系显着更高的周转数。此外，它表明，Pt的高催化活性可以合理化的氢在金属表面上的吸附能，所揭示的密度泛函理论计算在不同的金属表面。
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 selectiveC3-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.