Exploring Rhodium(I) Complexes [RhCl(COD)(PR3)] (COD=1,5-Cyclooctadiene) as Catalysts for Nitrile Hydration Reactions in Water: The Aminophosphines Make the Difference

Several rhodium(I) complexes, [RhCl(COD)-(PR3)], containing potentially cooperative phosphine ligands, have been synthesized and evaluated as catalysts for the selective hydration of organonitriles into amides in water. Among the different phosphines screened, those of general composition P(NR2)(3) led to the best results. In particular, complex [RhCl(COD){P(NMe2)(3)}] was able to promote the selective hydration of a large range of nitriles in water without the assistance of any additive, showing a particularly high activity with heteroaromatic and heteroaliphatic substrates. Employing this catalyst, the antiepileptic drug rufinamide was synthesized in high yield by hydration of 4-cyano-1-(2,6-difluorobenzyl)-1H-1,2,3-triazole. For this particular transformation, complex [RhCl(COD){P(NMe2)(3)}] resulted more effective than related ruthenium catalysts.