Du Xinze, Fan Hongjun, Liu Shenglin, Zhang Z Conrad
State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Nat Commun. 2023 Aug 2;14(1):4479. doi: 10.1038/s41467-023-40101-7.
C-C bond forming reaction by alkylation of aryl rings is a main pillar of chemistry in the production of broad portfolios of chemical products. The dominant mechanism proceeds via electrophilic substitution of secondary and tertiary carbocations over acid catalysts, forming multiple aryl alkylation products non-selectively through all secondary and tertiary carbons in the alkyl chains but producing little α-C alkylation products because primary carbocations are poorly stable. Herein, we report that anatase TiO (TiO-A) catalyzes nucleophilic α-C alkylation of phenols with alcohols in high selectivity to simply linear alkylphenols. Experimental and computational studies reveal the formation of Ti=C- bond with the α-carbon of the alkyl group at oxygen vacancies of the TiO-A surface. The subsequent α-C alkylation by selective substitution of phenol ortho-C-H bond is verified by deuterium exchanged substrate and DFT calculations.
通过芳环烷基化形成碳 - 碳键的反应是化学领域中生产多种化学产品的主要支柱。主要机制是通过酸催化剂上仲碳和叔碳正离子的亲电取代进行，通过烷基链中的所有仲碳和叔碳非选择性地形成多种芳基烷基化产物，但由于伯碳正离子稳定性差，几乎不产生α - 碳烷基化产物。在此，我们报道锐钛矿型TiO（TiO - A）能高选择性地催化酚类与醇类的亲核α - 碳烷基化反应，生成简单的线性烷基酚。实验和计算研究表明，在TiO - A表面的氧空位处，烷基的α - 碳与Ti = C键形成。通过氘交换底物和密度泛函理论计算验证了随后通过酚邻位碳 - 氢键的选择性取代进行的α - 碳烷基化反应。
