An Improved Scalable Process for the Synthesis of (S,S)-DACH-Ph Trost Ligand

An improved chemical process has been developed for the synthesis of (S,S)-DACH-Ph Trost ligand. The amidation of 2-diphenylphosphinylbenzoic acid and (S,S)-diaminocyclohexarie is promoted by stoichiometric CDI and catalytic imidazole hydrochloride. The resulting product, (S,S)-DACH-Ph Trost ligand, is isolated as a white solid in 80% yield with >99% ee by simple filtration without column chromatography. The current facile process is also demonstrated on kilogram scale.