Hectogram-Scale Synthesis of Carbamates Using Electrochemical Hofmann Rearrangement in Flow.

The Hofmann rearrangement of alkyl and aryl carboxamides can be achieved electrochemically on a hectogram scale. The necessary halogen species and base equivalents are generated from sodium bromide in methanol by electrolysis. Both the supporting electrolyte and the solvent fulfill the role of mediator, conductivity-enabling agent, and reaction partners. This electrochemical conversion can be carried out in simple and commercially available plate-frame cells if a simple glassy carbon anode is used. A productivity of 104 mmol per h is obtained with 162 cm2 of anode surface.