Electrochemical Initiated C-N Coupling of 3-Methylcatechol and n-Hexylamine in a Flow Cell Monitored with ESI-MS

The electrochemical initiated heterocoupling of 3-methylcatechol and n-hexylamine was investigated. The oxidation of 3-methylcatechol was performed in an electrochemical flow cell with glassy carbon as the working electrode. As a result, the two-electron, two-proton oxidised chinone intermediate undergoes a C-N coupling reaction in the presence of an amine (Michael addition). This mono coupling product can undergo a second two-electron, two-proton oxidation depending on acidic or basic conditions and substrate ratios. This flow cell was coupled on-line with electrospray ionisation mass spectrometry to identify the possible coupling products. Higher substrate concentrations were performed off-line as first scale-up experiments in a two-step procedure.