Stainless steel promoted the electrochemical oxidation of amines into imines

Abstract

We report the electrochemical oxidation of benzylamine (BA) into the imine by applying a bare stainless steel mesh (SSM) as an anode. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) elemental mapping analysis confirmed that there was no corrosion on the surface of SSM after an anodic electrolysis. Based on the gas chromatography (GC) analysis and electrochemical results, it was confirmed that conversion of BA with SSM was approximately 3.3 times higher than with Pt electrode. This work suggests that the anodic electrolysis with a bare SSM could be a promising route to electrochemical oxidation of BA in the absence of oxidizing agents.

Beyond Traditional Synthesis: Electrochemical Approaches to Amine Oxidation for Nitriles and Imines

“…For benzylamine oxidation, stainless steel shows much higher reactivity compared to Pt. 18 In 2022, Huang's group subjected benzylamine to 10 h of self-oxidative coupling reaction under constant voltage (5 V) using tetraethylammonium bromide (TEAB) as an electrolyte. They applied an undivided cell equipped with a carbon anode and carbon cathode at room temperature, resulting in the formation of the target product imine with a yield of 96% (GC, Scheme 20).…”

“…Kwon’s group (2022) used stainless steel as WE and Pt as CE without any added oxidant (Scheme ). For benzylamine oxidation, stainless steel shows much higher reactivity compared to Pt …”

“…16 Imine compounds are as important as amines and play irreplaceable roles in agriculture, medicine, and chemical biology. 18 The traditional reaction of amino oxidation to imine requires an equal molar amount of oxidant (e.g., Dess−Martin periodinane, Swern oxidant, metal catalysts, 19,20 Lewis acid catalysts, 21 and TEMPO 22,23 ) or higher reaction temperature; 24,25 furthermore, due to the low atom efficiency, these processes will generate a significant quantity of potentially toxic byproducts. Therefore, efficient, economical, and green control of oxidation conditions to oxidize amines into the desired target compound has become a goal pursued by some researchers.…”

Mechanistic Aspects of the Electrochemical Oxidation of Aliphatic Amines and Aniline Derivatives

“…The electrochemical oxidation of benzylamine in acetonitrile at a stainless-steel mesh anode in the presence of 0.1 M tetrabutylammonium perchlorate as the supporting electrolyte was studied [ 34 ]. Due to the absence of methyl groups, the formation of an intermediate equivalent to 2b occurs, which reacts with starting material (Equation (10)), resulting in the formation of N-benzylidenebenzylamine ( 7 ) and a small percentage of benzonitrile [ 34 ]. …”