A one-pot chemoselective synthesis of secondary amines by using a biomimetic electrocatalytic system

Abstract

A one-pot electrochemically induced oxidation-imine formation-reduction route to secondary amines is described in detail. The key step of the process consists of the oiminoquinone-mediated chemoselective catalytic oxidation of a primary aliphatic amine substrate, in the presence of a second amine used as the alkylating agent. Through the examination of the scope of the reaction by systematically varying both amine substrate and amine alkylating agent, it can be shown that this reaction sequence, leaving ammonia as the sole by-product, allows the rapid synthesis of various secondary amines in moderate to good yields. This process, that highlights the pre-eminent green advantages of electrochemical synthesis, especially the utilization of electricity as energy instead of chemical reagents, high atom economy as well as ambient temperature and pressure, could be a mild alternative to already reported synthetic methods.

Quinone‐Catalyzed Selective Oxidation of Organic Molecules

“…(A) Electrochemical oxidation of amines to imines [107] and (B) secondary amines, [108] by CAO mimics Q1 red and Q2 red . (C) When Cu I is added as a co-catalyst, the aerobic oxidation of primary amines is also achieved.…”

“…Electrolysis at −1.6 V for 1 h reduced the cross-coupled imines to secondary amines, which could be isolated after workup (Scheme 35B). [108] …”

Substituted o-Aminophenols as Redox-Mediators in the Thiol Oxidation to Unsymmetrical Disulfides

“…It is known that these compounds have been successfully investigated as redox mediators of amine oxidation. [42][43][44][45] The electrooxidation of N-acetyl-p-aminophenol leads to N-acetyl-p-iminobenzoquinone formation which can react with N-cysteine or glutathione to form the corresponding disulfides. 46 In turn, the anodic activation of N,N-diphenylbenzene-1,4-diamine in the presence of various thiols leads to thioethers.…”