Electrochemical-promoted Mannich-type three-component reaction of benzo-fused cyclic amides using methanol as C1 source instead of formaldehyde

The three-component N-Mannich reaction is provided in an electrochemical variant. The corresponding N-Mannich base products were obtained by the one-pot method of benzo-fused cyclic amides with secondary amines under a small current of 3 mA using methanol as the carbon source. The reaction is simple to carry out (room temperature and air environment) and requires no supporting electrolytes, using TEMPO as the oxidizing agent. The substrate scope is wide, and the yield is good (39 cases, up to 99 %). CV experiments show that secondary amines are oxidized first at the anode. Moreover, this reaction can be scaled up to the grams.