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.
Serrano
Isabel
I
Departament de Química, Universitat de Girona, Campus de Montilivi, E-17071 Girona, Spain.
Rodríguez
Montserrat
M
Romero
Isabel
I
Llobet
Antoni
A
Parella
Teodor
T
Campelo
Juan M
JM
Luna
Diego
D
Marinas
José M
JM
Benet-Buchholz
Jordi
J
D000577:Amides / Q000737:chemistry*; D002384:Catalysis; D002412:Cations; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction; D017975:Ruthenium Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D013386:Succinates / Q000737:chemistry*
D000577:Amides; D002412:Cations; D009942:Organometallic Compounds; D017975:Ruthenium Compounds; D013386:Succinates; C518953:dimethyl itaconate; C005229:itaconic acid; C038365:ruthenium chloride