- Enantioselective borane reduction of prochiral ketones catalyzed by a chloro-containing chiral β-amino alcohol
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A chloro-containing chiral β-amino alcohol (S)-2-amino-3-(2-chlorophenyl)-1,1-diphenyl-1-propanol (1) was prepared from the related amino acid, which was synthesized via malonic ester method. As a catalyst for the enantioselective borane reduction of prochiral ketones, 1 is better than those that have a similar structure but have no halogen atom in the molecule.
- Shen, Zong-Xuan,Lu, Jun,Zhang, Qing,Zhang, Ya-Wen
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- Rh-catalyzed asymmetric hydrogenation of prochiral olefins with a dynamic library of chiral TROPOS phosphorus ligands
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A library of 19 chiral tropos phosphorus ligands, based on a flexible (tropos) biphenol unit and a chiral P-bound alcohol (11 phosphites) or secondary amine (8 phosphoramidites), was synthesized. These ligands were screened, individually and as a combination of two, in the rhodium-catalyzed asymmetric hydrogenation of dehydro-α-amino acids, dehydro-β-amino acids, enamides and dimethyl itaconate. ee values up to 98% were obtained for the dehydro-α-amino acids, by using the best combination of ligands, a phosphite [4-P(O)2O] and a phosphora midite [13-P(O)2N]. Kinetic studies of the reactions with the single ligands and with the combination of phosphite [4-P(O)2O] and phosphoramidite [13-P(O) 2N] have shown that the phosphite, despite being less enantioselective, promotes the hydrogenation of methyl 2-acetamidoacrylate and methyl 2-acetamidocinnamate faster than the mixture of the same phosphite with the phosphoramidite, while the phosphoramidite alone is much less active. In this way, the reaction was optimized by lowering the phosphite/phosphoramidite ratio (the best ratio is 0.25 equiv phosphite/1.75 equiv phosphoramidite) with a resulting improvement of the product enantiomeric excess. A simple mathematical model for a better understanding of the variation of the enantiomeric excess with the phosphite/ phosphoramidite ratio is also presented.
- Monti, Chiara,Gennari, Cesare,Piarulli, Umberto,De Vries, Johannes G.,De Vries, Andre H. M.,Lefort, Laurent
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- Synthesis and application of peripherally alkyl-functionalized dendritic pyrphos ligands: Homogeneous-supported catalysts for enantioselective hydrogenation
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A new series of dendritic ligands with a chiral diphosphine located at the focal point have been synthesized through coupling of (R,R)-3,4-bis(biphenylphosphino)pyrrolidine (pyrphos) with peripherally alkyl-functionalized benzoic acid dendrons. These ligands were employed in the Rh-catalyzed asymmetric hydrogenation of prochiral dehydroamino acids, exhibiting excellent catalytic activities and enantioselectivities. The second-generation dendritic catalyst could be recovered by simple liquid-liquid biphasic separation and reused four times without serious loss of its activity and selectivity.
- Yi, Bing,He, Hua-Ping,Fan, Qing-Hua
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experimental part
p. 82 - 85
(2010/04/25)
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- Novel atropisomeric bisphosphine ligands with a bridge across the 5,5′-position of the biphenyl for asymmetric catalysis
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A new type of atropisomeric bisphosphine ligand 2 with a bridge across the 5,5′-position of the biphenyl has been developed. The axial chirality of this type of ligands can be retained by macrocyclic ring strain produced from 5,5′-linkage of the biphenyl
- Wei, Hao,Zhang, Yong Jian,Wang, Feijun,Zhang, Wanbin
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p. 482 - 488
(2008/09/19)
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- Synthesis of a novel spiro bisphosphinite ligand and its application in Rh-catalyzed asymmetric hydrogenation
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A novel, chiral bisphosphinite ligand (R)-SpiroBIP has been synthesized. The rhodium complex of the ligand was found to be highly enantioselective in the asymmetric hydrogenation of α-dehydroamino acid derivatives.
- Guo, Zhenqiu,Guan, Xiaoyu,Chen, Zhiyong
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p. 468 - 473
(2007/10/03)
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- Endothelin antagonist
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The instant invention relates to some tripeptide derivatives having activity against endothelin a process for preparing them, pharmaceutical composition containing the same and their use in prevention or treatment of some diseases associated with endothelin.
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- Asymmetric catalysis based on chiral phospholanes and hydroxyl phospholanes
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Chiral phosphine ligands derived from chiral natural products including D-mannitol and tartaric acid. The ligands contain one or more 5-membered phospholane rings with multiple chiral centers, and provide high stereoselectivity in asymmetric reactions.
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Page column 22
(2010/02/06)
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- A comparison of the asymmetric hydrogenation catalyzed by rhodium complexes containing chiral ligands with a binaphthyl unit and those with a 5,5′,6,6′,7,7′,8,8′-octahydro-binaphthyl unit
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The chiral ligands H8-BINAPO and H8-BDPAB were synthesized by reacting chlorodiphenylphosphine with H8-BINOL and H8-BINAM, respectively. Applications of these ligands in the Rh-catalyzed enantioselective hydrogenation of a variety of (Z)-acetamido-3-arylacrylic acid methyl esters provided chiral amino acid derivatives with good to excellent enantioselectivities (H8-BINAPO: up to 84.0% e.e.; H8-BDPAB: up to 97.1% e.e.). In the hydrogenation of acetamidoacrylic acid, 99% e.e. was obtained when a [Rh(H8-BDPAB)]+ catalyst was used. The catalytic activities and enantioselectivities of [Rh(H8-BINAPO)]+ and [Rh(H8-BDPAB]+ are substantially better than those obtained with the corresponding rhodium catalysts containing BINAPO (up to 64% e.e.) and BDPAB (up to 92.6% e.e.).
- Zhang, Fu-Yao,Kwok, Wai Him,Chan, Albert S.C.
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p. 2337 - 2342
(2007/10/03)
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- A highly effective phosphinite ligand derived from D-mannitol for Rh- catalyzed asymmetric hydrogenation
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A novel chiral phosphinite 1,2,5,6-di-isopropylidene-3, 4- bis(diphenylphosphino)-D-mannitol was prepared and its rhodium complex was found to be an effective catalyst for the asymmetric hydrogenation of amidoacrylic acid and its derivatives with product ee's ranging from 90% to 97%.
- Chen, Yixin,Li, Xingshu,Tong, Siu-Kuen,Choi, Michael C.K.,Chan, Albert S.C.
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p. 957 - 960
(2007/10/03)
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