Masahiko Saburi

Synthesis of novel chiral ruthenium complexes of 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl and their use as asymmetric catalysts

Reactions of [RuCl2(COD)]n(COD = cyclo-octa-1,5-diene) with the chiral bidentate phosphine ligands 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl, BINAP, and 2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl, p-tolyl-BINAP, give new chiral ruthenium(II) complexes, Ru2Cl4(BINAP)2(NEt3)and Ru2Cl4(p-toly-BINAP)2(NEt3) respectively, which serve as excellent catalysts for asymmetric hydrogenation of alkenes and some cyclic anhydrides.

Asymmetric hydrogenation of 3,5-Dioxoesters catalyzed by Ru-binap complex: A short step asymmetric synthesis of 6-substituted 5,6-dihydro-2-pyrones

Abstract Asymmetric hydrogenation of 3,5-dioxoesters 1a-c using Ru2Cl4((R) or (S)-binap)2(NEt3) as the catalyst gave dominantly anti 3,5-dihydroxyesters 2, which were then converted into unsaturated lactones 5a-b (ca. 80% e.e.). The pathway of the hydrogenation reaction was also investigated by asymmetric hydrogenation of (R)- or (S)-5-hydroxy-3-oxoester 8a-c. It was revealed that the Ru-binap catalyzed hydrogenation of 1a-b proceed dominantly via the β-diketone mode. A convenient asymmetric synthesis of hydroxylactone 3c and unsaturated lactone 5c was presented.

Catalytic asymmetric hydrogenation of cyclic anhydrides using ruthenium (II) chiral phosphine complex

Abstract Optically active γ- and δ-lactones are obtained by the hydrogenation of five- and six-membered cyclic anhydrides using a Ru(II) complex with chiral phosphine ligand, DIOP, as a catalyst.

Asymmetric hydrogenation of 2-fluoro-2-alkenoic acids catalyzed by Ru-binap complexes: A convenient access to optically active 2-fluoroalkanoic acids☆

Abstract Asymmetric hydrogenation of ( Z )-2-fluoro-2-alkenoic acid, ( Z )- 1a and ( Z )- 1b , was carried out, employing Ru 2 Cl 4 (binap) 2 (NEt 3 ) as a catalyst to afford 2-fluoroalkanoic acids, 2a and 2b , having high enantiomeric purities (up to 90% e.e.) When the ( R )-binap catalyst was used, not only ( Z )- 1a but ( E )- 1a was hydrogenated smoothly to give ( R )- 2a with comparable asymmetric induction.

Asymmetric hydrogenation of prochiral carboxylic acids catalyzed by the five-coordinate ruthenium(II)-hydride complex [RuH(binap)2]PF6 (binap = (R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl)

Abstract The five-coordinate complex [RuH(binap)2]PF6 (I, binap = (R)- or (S)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) has been found to have sufficient catalytic activity for asymmetric hydrogenation of itaconic acid and other prochiral carboxylic acids under mild conditions. The catalytic hydrogenation of itaconic acid by I was examined under a variety of conditions, and the addition of triethylamine was found to effect high enantioselectivities (> 90% ee). 1H and 31P NMR examinations of reaction mixtures of I and itaconic acid under conditions similar to the hydrogenation suggested the formation of ruthenium species containing one binap chelate.

Asymmetric hydrogenation of methyl 3,5-dioxohexanoate catalyzed by ru-binap complex: a short step asymmetric synthesis of dihydro-60methyl-2-H-pyran-2-one

Abstract Hydrogenation of methyl 3,5-dioxohexanoate 3 using Ru 2 Cl 4 ((R) or (S)-binap) 2 (NEt 3 ) as the catalyst gave dominantly anti 3,5-dihydroxyester 9 , which was then converted into unsaturated lactone 4 . The pathway of the hydrogenation reaction was also investigated.

Asymmetric hydrogenation of prochiral alkenes catalysed by ruthenium complexes of (R)-(+)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl

Two chiral ruthenium(II) complexes containing (R)-(+)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl[(R)-BINAP] were found to be effective catalysts for the asymmetric hydrogenation of 2-acylaminoacrylic and 2-acylaminocinnamic acids under mild conditions, to afford N-acyl-(R)-α-amino acids with 49–95% optical purity. The differences between the asymmetric hydrogenations effected by RuII- and RhI-(R)-BINAP systems are discussed. Asymmetric hydrogenation of methylenesuccinic acid and its derivatives with Ru-(R)-BINAP is also described.

Ruthenium(II)–BINAP catalysed stereoselective homogeneous hydrogenation of 1,3-diketones

Ruthenium–BINAP catalysed hydrogenation of 1,3-diketones gives 1,3-diols with extremely high diastereo- and enantio-selectivity.

Asymmetric transfer hydrogenation of prochiral carboxylic acids catalyzed by a five-coordinate Ru(II)-binap complex☆

Abstract Asymmetric transfer hydrogenation of representative prochiral carboxylic acids was performed, using [RuH(binap) 2 ]PF6 as a catalyst and 2-propanol or ethanol as a hydrogen source.

Asymmetric hydrogenation of prochiral carboxylic acids and functionalized carbonyl compounds catalysed by ruthenium(II)-binap complexes with aryl nitriles (binap = (R)- or (S)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl)

Abstract Complexes RuCl2(ArCN)2(binap), II (binap = (R)- or (S)-2,2′-bis(diphenylphosphino)- 1,1′-binaphthyl; ArCN = benzonitrile, a; 2-furancarbonitrile, b; pentafluorobenzonitrile, c) were prepared, and their solution properties were investigated by 31P NMR measurements. The catalytic activities and enantioselectivities for IIa–c catalysed hydrogenation of some prochiral acids were very similar to those provided by Ru2Cl4(binap)2(NEt3), I. In the hydrogenation of β-functionalized carbonyl compounds, however, IIa–c showed considerably lower activities and/or selectivities, compared with complex I. The differences in IIa–c catalysed reactions are discussed in relation to the coordinating abilities of ArCN in II.