An efficient and safe procedure for the large-scale Pd-catalyzed hydrazonation of aromatic chlorides using Buchwald technology

A convenient, optimized and safe synthesis of N-arylhydrazines, useful as intermediates for active ingredients in agricultural and pharmaceutical applications, is reported. Starting from aryl halides (chlorides and bromides), a palladium-catalyzed carbon-nitrogen coupling reaction followed by an acidic treatment afforded the target molecules in good to excellent yields using low catalyst loadings. This technology has then been successfully applied on a large scale in a pilot plant. This contribution also describes the major improvements in ligand synthesis and the thermal data required to develop a process on a pilot scale.