Rhodium/tris-binaphthyl chiral monophosphite complexes: Efficient catalysts for the hydroformylation of disubstituted aryl olefins

A family of threefold symmetry phosphite ligands, P(O–BIN–OR)3 (BIN = 2,2′-binaphthyl; R = Me, Bn, CHPh2, 1-adamantyl), derived from enantiomerically pure (R)-BINOL, was developed. Cone angles within the range 240–270° were calculated for the phosphite ligands, using the computational PM6 Hamiltonian. Their rhodium complexes formed in situ showed remarkable catalytic activity in the hydroformylation of hindered phenylpropenes, under relatively mild reaction conditions, with full chemoselectivity for aldehydes, high regioselectivity, however with low enantioselectivity. The ether substituents at the ligand affected considerably the catalytic activity on the hydroformylation of 1,1- and 1,2-disubstituted aryl olefins. The kinetics of the hydroformylation of trans-1-phenyl-1-propene, using tris[(R)-2′-benzyloxy-1,1′-binaphthyl-2-yl]phosphite as model ligand, was investigated. A first order dependence in the hydroformylation initial rate with respect to substrate and catalyst concentrations was found, as well as a positive order with respect to the partial pressure of H2, and a slightly negative order with respect to phosphite concentration and CO partial pressure.

A family of tris-binaphthyl phosphite ligands demonstrated remarkable activity and regioselectivity in Rh-catalyzed hydroformylation of 1,1- and 1,2-disubstituted aryl olefins. Kinetic studies were performed for the hydroformylation of trans-1-phenyl-1-propene, using tris[(R)-2′-benzyloxy-1,1′-binaphthyl-2-yl] phosphite as model ligand.Figure optionsDownload as PowerPoint slideHighlights
► High yielding synthesis of a family of chiral tris-binaphthyl monophosphites.
► Ligand’s cone angles within 240–270° calculated through PM6 Hamiltonian.
► Remarkably active Rh catalysts for hydroformylation of disubstituted aryl olefins.
► Kinetic studies on the hydroformylation of trans-1-phenyl-1-propene.