title: Oxidation of primary amines to oximes with molecular oxygen using 1,1-diphenyl-2-picrylhydrazyl and WO3/Al2O3 as catalysts.
abstract: The oxidative transformation of primary amines to their corresponding oximes proceeds with high efficiency under molecular oxygen diluted with molecular nitrogen (O2/N2 = 7/93 v/v, 5 MPa) in the presence of the catalysts 1,1-diphenyl-2-picrylhydrazyl (DPPH) and tungusten oxide/alumina (WO3/Al2O3). The method is environmentally benign, because the reaction requires only molecular oxygen as the terminal oxidant and gives water as a side product. Various alicyclic amines and aliphatic amines can be converted to their corresponding oximes in excellent yields. It is noteworthy that the oxidative transformation of primary amines proceeds chemoselectively in the presence of other functional groups. The key step of the present oxidation is a fast electron transfer from the primary amine to DPPH followed by proton transfer to give the α-aminoalkyl radical intermediate, which undergoes reaction with molecular oxygen and hydrogen abstraction to give α-aminoalkyl hydroperoxide. Subsequent reaction of the peroxide with WO3/Al2O3 gives oximes. The aerobic oxidation of secondary amines gives the corresponding nitrones. Aerobic oxidative transformation of cyclohexylamines to cyclohexanone oximes is important as a method for industrial production of ε-caprolactam, a raw material for Nylon 6.
authors: R&D Planning and Business Development, Asahi Kasei Chemicals Corporation, 1-105 Kanda Jinbocho, Chiyoda-ku, Tokyo 101-0051, Japan. suzuki.kd@om.asahi-kasei.co.jp
authors: Ken
authors: K
authors: Suzuki
authors: Tomonari
authors: T
authors: Watanabe
authors: Shun-Ichi
authors: S
authors: Murahashi
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D001713:Biphenyl Compounds / Q000737:chemistry*; D002209:Caprolactam / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry*; D002384:Catalysis; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D010091:Oximes / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D010851:Picrates / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry*; D014414:Tungsten / Q000737:chemistry*
chemical_list: D000588:Amines; D001713:Biphenyl Compounds; D010087:Oxides; D010091:Oximes; D010851:Picrates; D011108:Polymers; C009916:nylon 6; D002209:Caprolactam; C511604:tungsten oxide; C004931:1,1-diphenyl-2-picrylhydrazyl; D000537:Aluminum Oxide; D010100:Oxygen; D014414:Tungsten