Design and synthesis of new fluorinated ligands for the rhodium-catalyzed hydroformylation of alkenes in supercritical CO 2 and fluorous solvents

Abstract

Novel fluorous biphenols, 5,5′-[ n-C 4F 9(CH 2) 3] 2-2,2′-biphenol and 5,5′-[ n-C 4F 9(CH 2) 3O] 2-3,3′-di- tert-butyl-2,2′-biphenol, as well as enantiopure BINOLs, ( S)-6,6′-[ n-C 4F 9(CH 2) 3] 2-BINOL, ( R)-6,6′-[ n-C 6F 13(CH 2) 3] 2-BINOL, and ( S)-6,6′-[ n-C 8F 17(CH 2) 3] 2-BINOL, are synthesized. These compounds serve as key intermediates for the syntheses of a variety of new fluorous ligands for regioselective and enantioselective catalytic reactions. Novel fluorous [Rf(CH 2) 3] 2-BINAPHOS ligands (Rf= n-C 4F 9, n-C 6F 13, and n-C 8F 17) are successfully synthesized. These new fluorous chiral ligands when used with a rhodium catalyst can achieve comparable or even higher regioselectivity and enantioselectivity in the asymmetric hydroformylation of styrene as compared to those by the Rh-BINAPHOS system.