Study On Electrocatalytic Secondary Amine N-Nitrosation/N-Nitration

N-nitrification/N-nitrosation can prepare nitro/nitroso compounds and is one of the important organic synthesis reactions.Traditional nitration/nitrosation methods must be performed in a strongly acidic medium environment,and there are disadvantages such as difficulty in subsequent treatment of waste acid and large reaction corrosion.Electrochemical organic synthesis,as a new efficient and environmentally friendly synthesis method,has promoted the development of free radical reactions and new redox reactions,and has received a lot of attention because it does not require external oxidants.In this paper,the N-nitrosation/N-nitrification reaction of secondary amine NH bonds in an acid-free system was studied using Fe(NO₃)₃·9H₂O as the source of nitroso/nitro.The substrate is universal and provides a green,highly selective and high yield method for preparing useful N-nitroso/N-nitro compounds.First,the influencing factors of N-nitrosated secondary amines were examined.The optimal process conditions for the reaction were obtained:1 mmol of secondary amine compound,2 mmol of iron nitrate nonahydrate,0.6 mmol of tetra-n-butylperchlorate,and acetonitrile.16 m L,maintaining a constant current of 12 m A and a constant temperature of70°C.The reaction was performed in a single-tank electrolytic cell protected by nitrogen for a graphite anode and a platinum electrode for 4 h.Under these conditions,the reaction yields were 60%-99%.Nitrosation products were obtained by column chromatography.The nitrosation products were characterized by infrared spectroscopy,nuclear magnetic resonance,and single crystal X-ray diffraction.Secondly,the influencing factors of N-nitrazole compounds were studied and the optimal reaction conditions were obtained:1 mmol of azole compounds,2 mmol of ferric nitrate nonahydrate,0.6 mmol of tetra-n-butyltetrafluoroborate,16 acetonitrile m L,maintaining a constant current of 15 m A and a constant temperature of 70°C,the reaction was performed in a single-tank electrolytic cell protected by argon with a graphite anode and a platinum electrode as the cathode for 7 h.Under these conditions,the reaction yields were 40%-80%.The nitrated product was obtained by column chromatography.The nitrated products were characterized by infrared spectroscopy,nuclear magnetic resonance,and single crystal X-ray diffractometer.In the end,control experiments,free radical capture experiments,cyclic voltammetry scans,and DFT calculations were performed to study the mechanism of electrocatalytic N-nitration/N-nitrosation,and the possible mechanism of this reaction was speculated.These experimental and computational studies indicate that the N-nitrosation reaction of secondary amines is the reaction of N·⁺radicals produced by secondary amine anodization with nitroso radicals produced by metal nitrates.The N-nitrification reaction of azoles is the reaction of N·radicals generated by anodic oxidation of azole compounds with nitro radicals generated by metal nitrates.