Water-soluble arene ruthenium catalysts containing sulfonated diamine ligands for asymmetric transfer hydrogenation of α-aryl ketones and imines in aqueous solution

A new family of nine cationic organometallic aqua complexes of the type [(arene)Ru(RSO2N∩NH2)(OH2)]+ (1–9), containing chiral N,N-chelating ligands, has been synthesised and isolated as the tetrafluoroborate salts, which are water-soluble and stable to hydrolysis. The enantiopure complexes 1–9 catalyse the transfer hydrogenation of prochiral aryl ketones and imines in aqueous solution to give the corresponding alcohols and amines with good conversion and enantioselectivity. This method gives an environmentally friendly access, for instance, to isoquinoline alkaloids by asymmetric catalysis in water.