Main Article Content
Bis salicylaldehyde ethylenediamine Schiff base (Salen) and its complexes with three metal ions (Co2+, Ni2+, Zn2+) were prepared, and characterized by infrared spectroscopy(IR). Using air as oxygen source, the optimum reaction conditions for the catalytic oxidation of 0.05 mol benzoin by Co (Salen) were obtained by orthogonal test as follows: base KOH 2 g, catalyst 1.5 g, N, N-dimethylformamide(DMF) as solvent, reaction temperature 40 °C, reaction time 1 h. Under these conditions, the catalytic performances of different metal complexes were investigated. The catalytic activity of Co(Salen) was the best one, the yield of benzil was up to 93.6%, the number of Ni(Salen) and Zn(Salen) was 86.3% and 82.1%, respectively. The reused catalytic performance of M(Salen) complex was also studied. The catalytic activity of Co(Salen), Ni(Salen) and Zn(Salen) was stable after 4 times recycle, the yield of benzil was 71.4%, 63.3% and 57.4%, respectively, and it was easy for catalyst recycling. The oxidation product was certainly benzil with high purity according to the characterization results of melting point(MP), IR, high performance liquid chromatography(HPLC) and 1H nuclear magnetic resonance(1H NMR). Compared with the common synthetic method of benzil, this one has the advantages of friendly environment, low cost and easy operation. It is a simple and green way to synthesize benzoyl efficiently.
Tymonko SA, Nattier BA, Mohan RS. Oxidation of benzoins to benzils using bismuth(III) nitrate-copper(II) acetate. Tetrahedron Letters. 1999;40(43):7657-7659.
Shamim T, Choudhary D, Mahajan S, Gupta R, Paul S. Covalently anchored metal complexes onto silica as selective catalysts for the liquid phase oxidation of benzoins to benzils with air. Catalysis Communications. 2009;10(14):1931-1935.
Safari J, Zarnegar Z, Rahimi F. An efficient oxidation of benzoins to benzils by Manganese(II) Schiff base complexes using green oxidant. Journal of Chemistry. 2013;1-7. Available:http://dx.doi.org/10.1155/2013/765376.
Maurya MR, Mengesha B, Uprety B, Jangra N, Tomar R, Avecilla F. Oxygen atom transfer between DMSO and benzoin catalyzed by cis-dioxidomolybdenum(VI) complexes of tetradentate Mannich bases. New Journal of Chemistry, 2018;42(8): 6225-6235.
Huo YQ, Chen XL, Zhang FX, Li J, Wang SW, Cui HL. Synthesis and crystal structure of iron(II) complex with N, N-bis(salicylidene) ethylenediamine. Journal of Yan'an University (natural science edition). 2010;29(1):62-64. Chinese.
Yuan SJ, Fang HL, Lu CX. Oxidation of benzoin catalyzed by Cu(Salen). Chemical World. 2004;(5):233-235. Chinese.
Xie KY, Chen Q, Wang JY, Lin QQ, Zheng H. One-pot green synthesis of benzil. Chinese Journal of Applied Chemistry, 2016;33(11):1284-1288. Chinese.
Wu GC, Liang LX, Ye ZK, Zhang ZH, Nie JJ, Li N. Oxidation of benzoin using Salen complexes as biomimetic catalysts. Research and Exploration in Laboratory, 2017;36(2):39-43. Chinese.
Ding C, Ni JP, Tang R, Ma D, Qiang GR. Catalytic oxidation of benzoin by green chemistry. Journal of Zhejiang University of Technology. 2009;37(5):542-544. Chinese.