Development of large-scale oxidative Bromination with HBr-DMSO by using a continuous-flow microwave system for the subsequent synthesis of 4-Methoxy-2-methyldiphenylamine

An efficient procedure of continuous-flow microwave reactor, for oxidative bromination with HBr (hydrogen bromide) -DMSO (dimethyl sulphoxide) in large scale is described herein. The reaction is carried out in a metal-free manner, with the use of water as solvent under microwave irradiation conditions. The productivity of this continuous step attains 60 g/min under the optimal conditions, implying a theoretical productivity of 8.6 kg/day. The reaction mixture is screened by thermal insulation accelerometer to ensure the safe process of this reaction in these conditions. 4-Bromo-3-methylanisole is further reacted with formanilide in the presence of cuprous iodide (CuI) and potassium carbonate (K2CO3) to give 4-methoxy-2-methyldiphenylamine, a common intermediate in fine chemical industry such as dye and paper chemistry, in an isolated yield of 65.2%. with more than 200 g scale.