Zr(OH)4-Catalyzed Controllable Selective Oxidation of Anilines to Azoxybenzenes, Azobenzenes and Nitrosobenzenes
Graphical Abstract
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.
Abstract
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.
Conflict of interest
The authors declare no conflict of interest.
