Pairing Shono-type electro-oxidation with the electro-reduction of dimethyl phthalate in a recycle flow reactor

Shono-type electro-oxidation was paired with the electro-reduction of dimethyl phthalate to achieve excellent atom economy for the first time. When methyl piperidine-1-carboxylate was employed as the anodic substrate, a total faradaic efficiency of up to 160% was achieved with graphite electrodes and solution of tetraalkylammonium salt in methanol as the electrolyte. With the aid of the Design of Experiments method, reaction conditions including temperature, substrate concentration, and current density were efficiently optimized, resulting in the optimal electrolytic conditions of 50 mA cm⁻², 0.8 M of methyl piperidine-1-carboxylate and 0.4 M of dimethyl phthalate at 3 °C. Based on these conditions, a 100-gram-scale reaction was successfully conducted in a recirculating flow electrolytic cell, demonstrating the utility of this green and sustainable electrosynthesis method. The results of the mechanistic investigation rationalized the pattern of the response surface.