Continuous process for preparation of 2,3-dimethyl-4-methylsulfonylbromobenzene via oxidation by in situ formed peracetic acid

2,3-dimethyl-4-methylsulfonylbromobenzene(BDSO) is an important intermediate of topramezone, a highly effective corn herbicide. However, its synthesis requires peroxyacetic acid as oxidant and poses a safety risk. In this work, a continuous flow to in situ generations of peroxyacetic acid and thioether oxidation for the preparation of BDSO was developed using a three-stream micromixing process. By in-situ generation and consumption of peroxyacetic acid, the safety hazard of peroxyacetic acid was eliminated, and a green and efficient preparation of BDSO was also achieved. Compared to the batch reactor, the three-stream micromixing process has a shorter residence time(6 min), and higher space-time yield(8.56 mol L −1 h −1 ). This method has great potential in industrial applications.