A New Process to Prepare Thiophene-2-Carbonyl Chloride, a Key Raw Material in the Synthesis of Tioxazafen, Utilizing a Catalytic Liquid Phase Aerobic Oxidation Reaction

Thiophene-2-carbonyl chloride (TCC) is the key raw material in the preparation of tioxazafen, a proprietary seed treatment that was being developed by Bayer AG as a broad-spectrum nematicide. Current manufacturing routes to TCC suffer from side product formation and significant waste generation, which lead to high manufacturing costs. A new and potentially more cost-effective process to prepare TCC from thiophene has been developed. The key step in the process utilizes homogeneous liquid-phase aerobic oxidation of 2-acetylthiophene (AcT). This article describes development details for each of the three steps involved in the new process.