Asymmetric hydroformylation and hydrogenation catalyzed by chiral rhodium and ruthenium complexes of phosphorylated 2,2′-bis(diphenyl-phosphino)-1,1′-binaphthyls

Accessible protocol for asymmetric hydroformylation of vinylarenes using formaldehyde

The rhodium(i)/chiral Ph-bpe-catalyzed reaction of vinylarenes with formaldehyde provides an accessible protocol for asymmetric hydroformylation to enantioenriched aldehydes in high yields.

Adsorption of Chiral 2,2‘-Substituted-1,1’-Binaphthalenes onto Silica-Supported Palladium and Nickel

The nature of the adsorption of a series of 2,2‘-substituted-1,1’-binaphthalenes over supported palladium and nickel catalysts has been studied. Adsorption has been shown to occur through the 2,2‘-substituted functional groups. Where this is not possible, no adsorption of the binaphthyl is observed. Adsorption of 2,2’-diamino-1,1’-binaphthalene occurred solely on the metal components of the catalysts. However, total coverage of the metal surface was not obtained, with only specific sites being available for adsorption. Adsorption of 2,2‘-dihydroxy-1,1’-binaphthalene occurred on the metal components but also spilled over onto the support. Adsorption was detected for 2-hydroxy-2‘-methoxy-1,1’-binaphthalene but no spill-over was observed, indicating that both hydroxy groups are involved in the spill-over process. Co-adsorption and sequential adsorption studies revealed that there are a variety of adsorption sites that favour different binaphthyls.

Catalytic Ability of a Cationic Ru(II) Monochloro Complex for the Asymmetric Hydrogenation of Dimethyl Itaconate and Enamides

The synthesis of two Ru chloro complexes, Ru(III)Cl(3)(bpea), 1, and cis-fac-Delta-[Ru(II)Cl{(R)-(bpea)}{(S)-(BINAP)}](BF(4)), cis-fac-Delta-(R)-(S)-2, (bpea = N,N-bis(2-pyridylmethyl)ethylamine; (S)-BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl), is described. Complex 2 is characterized in solution through UV-vis, cyclic voltammetry (CV), and 1D and 2D NMR spectroscopy. X-ray diffraction analysis indicates that in the solid state it possesses the same structure as in solution, as expected for a low-spin d(6) Ru(II)-type complex. The molecular structure of cis-fac-Delta-(R)-(S)-2, consists of a nonsymmetric complex, where the Ru metal center has a significantly distorted octahedral-type coordination because of the bulkiness of the (S)-BINAP ligand. cis-fac-Delta-(R)-(S)-2 has a remarkable catalytic performance at P = 6.8 atm of H2 and T = 70 degrees C toward the hydrogenation of prochiral double bonds both from efficiency and from stereoselectivity viewpoints. As an example, prochiral olefins of technological interest such as dimethyl itaconate, methyl 2-acetamidoacrylate or methyl 2-acetamidocinnamate are catalytically hydrogenated by cis-fac-Delta-(R)-(S)-2, with conversions higher than 99.9% and ee > 99. Furthermore, cis-fac-Delta-(R)-(S)-2, also catalyzes the selective hydrogenation of beta-keto esters, although the reaction rates are lower than those found with the former substrates.

Enolphosphato−Phosphines: A New Class of P,O Ligands

The new bifunctional ligands Ph(2)PCH[double bond]CPh[OP(O)(OR)(2)] (1) (1a, R = Et; 1b, R = Ph) represent the first examples of P,O derivatives resulting from the association of a phosphine moiety and an enolphosphate group. The Z stereochemistry about the double bond provides a favorable situation for these ligands to act as P,O-chelates. Neutral and cationic Pd(II) complexes have been synthesized and characterized, in which 1a or 1b acts either as a P-monodentate ligand or a P,O-chelate, via coordination of the oxygen atom of the P[double bond]O group. In the latter case, it has been observed that phosphines 1a and 1b can display a hemilabile behavior, owing to successive dissociation and recoordination of the O atom. Competition experiments revealed that phosphine 1a presents a higher chelating ability than 1b, a feature ascribed to the more electrodonating properties of the ethoxy groups in 1a compared to the phenoxy groups in 1b. P,O-Chelation affords seven-membered metallocycles, which is unusual for P,O-chelates. Complexes trans-[PdCl(2)[Ph(2)PCH[double bond]C(Ph)OP(O)(OPh)(2)](2)] (2b), [PdCl[Ph(2)PCHdouble bond]C(Ph)OP(O)(OEt)(2)](mu-Cl)](2) (3a), [complex--see text] (8a'), and [complex--see text] (10a) have been structurally characterized. Interestingly, the seven-membered rings in 8a' and 10a adopt a sofa conformation with the double bond lying almost perpendicular to the plane containing the Pd, the two P, and the two O atoms.

Synthesis of a new water-soluble C(2)-symmetric chiral diamine: preliminary investigation of its catalytic properties for asymmetric hydrogenation under biphasic conditions

A water-soluble version of N,N'-dimethyl-1,2-diphenylethane-1,2-diamine was prepared by introduction of phosphonic acid moieties on the para position of the aromatic rings. Preliminary investigation of the catalytic properties of the iridium complex of this ligand under biphasic conditions showed that this system compared well with the homogeneous counterpart for the asymmetric hydrogenation of ketones but with noticeably higher reaction rates for the biphasic system.