Pd-Catalysed Suzuki‒Miyaura cross-coupling of aryl chlorides at low catalyst loadings in water for the synthesis of industrially important fungicides

The Suzuki-Miyaura coupling reaction of electron-poor aryl chlorides in the synthesis of crop protection-relevant active ingredients in water is disclosed. Optimisation of the reaction conditions allowed to run the reaction with 50 ppm of Pd-catalyst loading without an additional organic solvent in the cross-coupling reaction step in short reaction times. The system was optimised for the initial cross-coupling step of the large scale produced fungicides Boscalide, Fluxapyroxad and Bixafen up to 97% yield. It is also shown that the Suzuki-Miyaura reaction can be easily scaled up to 50 g using a simple product separation and purification using environmental begin solvents in the work-up. To show the usability of this method, it was additionally applied in the three steps synthesis of the desired active ingredients.