Highly selective oxidation of amines to imines by Mn2O3 catalyst under eco-friendly conditions

Publication date: Available online 5 September 2019Source: Chinese Chemical LettersAuthor(s): Fushan Chen, Tao Yang, Songlin Zhao, Taotao Jiang, Lu Yu, Houfeng Xiong, Liu Liu, Jian Zhou, Pengxiang Tu, Jun Ni, Qunfeng Zhang, Xiaonian LiAbstractEnhancing the selectivity of imines for the oxidative self-coupling of primary amines was found to be challenging in the heterogeneous catalysis. Three different manganese oxides (M-3, M-4, M-5) were synthesized by controlling the calcination temperature using a simple template-free oxalate route. The prepared manganese oxides were systematically characterized using XRD, N2 sorption, SEM, TEM, XPS, H2-TPR techniques. M-4 gave 96.2% selectivity of imine at 100% conversion of benzylamine, which was far more superior than other existing protocols. Mn3+/Mn4+ ratio was found to affect the selectivity of the imines. The probable reaction pathway for amines oxidation catalyzed by manganese oxides was proposed for the first time.Graphical abstractMn2O3 calcined at 450 °C by a simple template-free oxalate route gave 96.2% selectivity of imine at 100% conversion of benzylamine. The high selectivity of the imines clearly depended on the Mn3+/Mn4+ ratio. The probable reaction pathway for amines oxidation catalyzed by manganese oxides was proposed for the first time. This catalytic process was carried out under milder conditions, no base additives, and air as the only oxidant.
Source: Chinese Chemical Letters - Category: Chemistry Source Type: research