Shao Jingna, He Rongxing, Shen Wei, Li Ming
College of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, China.
J Mol Model. 2014 May;20(5):2239. doi: 10.1007/s00894-014-2239-z. Epub 2014 May 7.
A computational study with the B3LYP functional was carried out to elucidate the mechanisms of AuCl₃- and AgOTf-catalyzed cyclization of 1-(indol-2-yl)-3-alkyn-1-ols. The theoretical studies suggested that the two main processes, cycloaddition and hydrogen-transfer, are included in all possible reaction pathways. Calculations revealed that AuCl₃ is more effective in catalytic ability than AgOTf to catalyze the cyclization of 1-(indol-2-yl)-3-alkyn-1-ols into carbazole derivatives. More importantly, we found that the ligands of catalysts, Cl⁻ and OTf⁻, are critical in a stepwise proton-transport process involved in intramolecular nucleophilic addition because they act as a proton shuttle to lower the activation free energy barrier of the rate-determining step. The theoretical discovery of the role of ligands of catalysts in hydrogen shift process suggests that AuCl₃- and AgOTf-catalyzed cyclization of 1-(indol-2-yl)-3-alkyn-1-ols can be accelerated when ligands with the property of nucleophile are used. Our theoretical calculations reproduced the experimental results very well. The present study is expected to help understand other transition metal-catalyzed reactions and to give guidance for future design of new catalysts.
采用B3LYP泛函进行了一项计算研究，以阐明AuCl₃和AgOTf催化1-(吲哚-2-基)-3-炔-1-醇环化反应的机理。理论研究表明，所有可能的反应途径都包含环加成和氢转移这两个主要过程。计算结果表明，在催化1-(吲哚-2-基)-3-炔-1-醇环化生成咔唑衍生物方面，AuCl₃的催化能力比AgOTf更有效。更重要的是，我们发现催化剂的配体Cl⁻和OTf⁻在分子内亲核加成所涉及的逐步质子转移过程中起着关键作用，因为它们充当质子穿梭体，降低了速率决定步骤的活化自由能垒。催化剂配体在氢转移过程中作用的理论发现表明，当使用具有亲核性质的配体时，AuCl₃和AgOTf催化的1-(吲哚-2-基)-3-炔-1-醇环化反应可以加速。我们的理论计算很好地重现了实验结果。本研究有望有助于理解其他过渡金属催化的反应，并为未来新型催化剂的设计提供指导。
