- Highly enantioselective rhodium-catalyzed hydrogenation of 2-(2-methoxy-2-oxoethyl)acrylic acid - A convenient access of enantiomerically pure isoprenoid building blocks
-
Asymmetric catalytic hydrogenation of 2-(2-methoxy-2-oxoethyl)acrylic acid (5) to give (2S)-4-methoxy-2-methyl-4-oxobutanoic acid [(S)-6] was studied. An enantiomeric excess of 99.7% ee was achieved with a catalyst formed in situ from [Rh(COD)2]BF4 and the chiral phosphite L2 in 1,2-dichloroethane as solvent. In addition, enzyme-catalyzed semi-saponification of dimethyl 2-methylsuccinate was investigated. Mono ester (S)-6 was transformed into a few compounds which can serve as C 5-building blocks in natural product syntheses. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Ostermeier, Markus,Brunner, Bernhard,Korff, Christian,Helmchen, Guenter
-
-
Read Online
- NOVEL BISPHOSPHANE CATALYSTS
-
In the present Application protection is sought for compounds of the general formula (I) as ligands for reactions catalysed by transition metals. The preparation thereof and use thereof, in particular for the preparation of β-amino acids, is also discusse
- -
-
Page/Page column 21-22
(2008/06/13)
-
- Expanding the scope of atropisomeric monodentate P-donor ligands in asymmetric catalysis: Hydrogen-transfer reduction of α,β-unsaturated acid derivatives by rhodium/Ph-binepine catalysts
-
A range of α,β-unsaturated acids and esters have been selectively reduced to the corresponding saturated acid derivatives by hydrogen transfer. As the reducing agent, formic acid was used in the presence of Rh 1 complexes formed with the powerful chiral ligand Ph-binepine (1), an axially chiral binaphthalene-type monodentate P-donor ligand. Very high stereoselectivities (up to 97% ee) were obtained in the case of itaconic acid (2a).
- Alberico, Elisabetta,Nieddu, Ilenia,Taras, Rossana,Gladiali, Serafino
-
p. 1716 - 1729
(2007/10/03)
-
- Asymmetric Hydrogenation Catalyzed by (S,S)-R-BisP*-Rh and (R,R)-R-MiniPHOS Complexes: Scope, Limitations, and Mechanism
-
A new class of chiral C2-symmetric bis(trialkyl)phosphine ligands has been prepared and used in Rh(I)-catalyzed asymmetric hydrogenation reactions. The ligands, 1,2-bis(alkylmethylphosphino)ethanes 1 a-g (abbreviated as BisP*, alkyl = t-butyl, 1-adamantyl, 1-methylcyclohexyl, 1,1-diethylpropyl, cyclopentyl, cyclohexyl, isopropyl) and 1,2-bis(alkylmethylphosphino)methanes 2 a-d (abbreviated as MiniPHOS, alkyl = t-butyl, cyclohexyl, isopropyl, phenyl) are prepared by a simple synthetic approach based on the air-stable phosphine-boranes. These new ligands give the corresponding Rh(I) complexes, which are effective catalytic precursors for the asymmetric hydrogenation of a representative series of dehydroamino acids and itaconic acid derivatives. Enantioselectivities observed in these hydrogenations are universally high and in many cases exceed 99%. X-Ray characterization of four precatalysts, study of the pressure effects, deuteration experiments, and characterization of the wide series of intermediates in the catalytic cycle are used for the discussion of the possible correlation between the structure of the catalysts and the outcome of the catalytic asymmetric hydrogenation.
- Gridnev, Ilya D.,Yamanoi, Yoshinori,Higashi, Natsuka,Tsuruta, Hideyuki,Yasutake, Masaya,Imamoto, Tsuneo
-
p. 118 - 136
(2007/10/03)
-
- Hybrid P-chiral diphosphines for asymmetric hydrogenation
-
A family of diphosphine ligands has been prepared by Michael addition of o-anisylphenyl phosphide to diethyl vinylphosphonate and elaboration to phospholanes based on hexane-2,5-diol or mannitol; some preliminary results of Rh-complex catalysed hydrogenations are reported.
- Carmichael, Duncan,Doucet, Henri,Brown, John M.
-
p. 261 - 262
(2007/10/03)
-
- 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 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 percent 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.
- Kawano, Hiroyuki,Ikariya, Takao,Ishii, Youichi,Saburi, Masahiko,Yoshikawa, Sadao,et al.
-
p. 1571 - 1575
(2007/10/02)
-
- OPTICALLY ACTIVE 2-VINYLCYCLOBUTANONES
-
Enzymatic resolution of dimethyl 2-methylsuccinate, acyloin cyclization and base induced ring contraction provided 1-hydroxycyclopropanecarboxylic acids with high optical purity (>95percent e.e).Their derivatives opened a regio- and stereoselective way to optically active 2-vinylcyclobutanones (>84-90percent e.e), providing useful building blocks for further ring expansions.
- Salaun, J.,Karkour, B.,Ollivier, J.
-
p. 3151 - 3162
(2007/10/02)
-
- Selectivity in the transesterification of esters by supported enzymes
-
The regio and enantioselectivities of the transesterification of racemic dimethyl esters by supported enzymes in absence of solvent are studied: preparations of chiral succinates and N-acetyl aminoesters are reported.
- Gubie-Jampel, E.,Rousseau, G.
-
p. 3563 - 3564
(2007/10/02)
-
- RUTHENIUM(II)-BINAP COMPLEX CATALYZED ASYMMETRIC HYDROGENATION OF UNSATURATED DICARBOXYLIC ACIDS
-
Asymmetric hydrogenation of unsaturated dicarboxylic acids employing ruthenium-BINAP complexes as catalyst gave optically active 2-alkylsuccinic acids with high enantioselectivities.
- Kawano, Hiroyuki,Ishii, Youichi,Ikariya, Takao,Saburi, Masahiko,Yoshikawa, Sadao,et. al
-
p. 1905 - 1908
(2007/10/02)
-