Zr(OH)4‐Catalyzed Controllable Selective Oxidation of Anilines to Azoxybenzenes, Azobenzenes and Nitrosobenzenes

• Published in: Angewandte Chemie International Edition Vol. 61; no. 2; pp. e202112907 - n/a
• Main Authors: Qin, Jiaheng, Long, Yu, Sun, Fangkun, Zhou, Pan‐Pan, Wang, Wei David, Luo, Nan, Ma, Jiantai
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 10.01.2022; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Additives; Aniline; anilines; Azo compounds; Catalysts; Chemical synthesis; Chemistry; Chemistry, Multidisciplinary; heterogeneous catalysis; Hydrogen peroxide; Hydroxyl groups; Industrial applications; Oxidants; Oxidation; Oxidizing agents; Physical Sciences; Science & Technology; Selectivity; unsymmetric catalysis; Zirconium; zirconium hydroxide; SURFACE-PROPERTIES; unsymmetric catalysis; heterogeneous catalysis; AROMATIC AZO-COMPOUNDS; CATALYZED SYNTHESIS; oxidation; ZIRCONIUM-OXIDE; anilines; zirconium hydroxide
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202112907

The selective oxidation of aniline to metastable and valuable azoxybenzene, azobenzene or nitrosobenzene has important practical significance in organic synthesis. However, uncontrollable selectivity and laborious synthesis of the expensive required catalysts severely hinders the uptake of these reactions in industrial settings. Herein, we have pioneered the discovery of Zr(OH)4 as an efficient heterogeneous catalyst capable of the selective oxidation of aniline, using either peroxide or O2 as oxidant, to selectively obtain various azoxybenzenes, symmetric/unsymmetric azobenzenes, as well as nitrosobenzenes, by simply regulating the reaction solvent, without the need for additives. Mechanistic experiments and DFT calculations demonstrate that the activation of H2O2 and O2 is primarily achieved by the bridging hydroxyl and terminal hydroxyl groups of Zr(OH)4, respectively. The present work provides an economical and environmentally friendly strategy for the selective oxidation of aniline in industrial applications. Zr(OH)4 can catalyze the selective oxidation of anilines to azoxybenzenes, symmetric/unsymmetric azobenzenes and nitrosobenzenes for a wide range of substrates. Control experiments and DFT calculations reveal that the activation of H2O2 and O2 can be attributed to the bridging hydroxyl and terminal hydroxyl groups of Zr(OH)4, respectively.