Heterogeneously catalyzed asymmetric hydrogenation of α-arylenamides over immobilized RhBPE and RhDUPHOS complexes

Optically active α-1-arylalkylamine derivatives were successfully synthesized through heterogeneous asymmetric hydrogenation of α-arylenamides over immobilized RhBPE and RhDUPHOS complexes on aluminum-containing M41S and SBA-15 type materials. The heterogeneous chiral catalysts were prepared by immobilization of rhodium diphosphine complexes on Al-MCM-41, Al-MCM-48, and Al-SBA-15. The complexes were bonded to the carrier by the interaction of the cationic rhodium of the organometallic complex with the anionic host framework, as well as between Al Lewis acid sites and P Lewis basic sites. The catalysts were characterized with XRD, FT-IR and MAS-NMR, as well as thermoprogramed desorption of ammonia, thermogravimetric analysis, and nitrogen sorption experiments. The immobilized catalysts showed high activities and excellent chemo- and enantioselectivities. Up to 99% e.e. at 99% conversion and >99% chemoselectivity were observed in the case of studied α-arylenamides. The catalysts could be reused up to four times without loss of catalytic activity or enantioselectivity.