- Optical Resolution of (+/-)-Phenylsuccinic Acid by Using (-)-Proline as Resolving Agent
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A solution of equimolar mixture of (+/-)-phenylsuccinic acid ((+/-)-PSA) and (-)-proline ((-)-Pro) in ethanol or its suspension in 2-propanol selectively gave a salt composed of 1-molar amount of PSA and 2-molar amount of (-)-Pro.The salt purified gave (+)-PSA with an optical purity of about 100percent.A salt composed of equimolar amounts of PSA and (-)-Pro was obtained from the ethanolic mother liquor, and gave (-)-PSA with an optical purity of 98percent.
- Shiraiwa, Tadashi,Sado, Yujin,Fujii, Shigeru,Nakamura, Mitsuhiro,Kurokawa, Hidemoto
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- Enantioseparation of Phenylsuccinic Acid Enantiomers by Solvent Sublation with Collaborative Selectors
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A new solvent sublation (SS) system for chiral separation is introduced by using phenylsuccinic acid (H2A) as the model enantiomers. The experiments were carried out in a traditional SS apparatus but with collaborative chiral selectors: dibenzoyl-L-tartaric acid (L-DBTA) in the organic phase and hydroxypropyl-β-cyclodextrin (HP-β-CD) in the aqueous phase. The chiral recognition abilities of the two selectors are opposite for the H2A enantiomers. Several important parameters were investigated. The results demonstrate that enantioselective sublation and partitioning behavior are mainly dependent on the pH of the solution, the concentrations of chiral selectors and H2A. Furthermore, the flow rate of air and flotation time also have some effects on the enantioseparation. Under the optimized conditions, the enantioselectivity expressed by the separation factor (β) and enantiomer excess (e.e.%) are 2.47 and 29.50%, and the yields of R-H2A and S-H2A are 0.23 and 0.13?g·L?1, respectively. Compared with the SS system with the single selector HP-β-CD in the aqueous phase (or L-DBTA in the organic phase), the increased values of β and e.e.% in the new SS system with collaborative selectors are 1.31 (or 1.38) and 5.90% (or 13.82%), respectively.
- Meng, Huiwen,Yan, Tao,Jiao, Feipeng,Wang, Shuai
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- Palladium-Catalyzed Asymmetric Hydroesterification of α-Aryl Acrylic Acids to Chiral Substituted Succinates
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A palladium-catalyzed asymmetric hydroesterification of α-aryl acrylic acids with CO and alcohol was developed, preparing a variety of chiral α-substituted succinates in moderate yields with high ee values. The kinetic profile of the reaction progress revealed that the alkene substrate first underwent the hydroesterification followed by esterification with alcohol. The origin of the enantioselectivity was elucidated by density functional theory computation.
- Ji, Xiaolei,Shen, Chaoren,Tian, Xinxin,Dong, Kaiwu
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supporting information
p. 8645 - 8649
(2021/10/25)
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- Chiral amorphous metal–organic polyhedra used as the stationary phase for high-resolution gas chromatography separations
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Herein, we describe a new chiral amorphous metal–organic polyhedra used as the stationary phase for high-resolution gas chromatography (GC). The chiral stationary phase was coated onto a capillary column via a dynamic coating process and investigated for a variety of compounds. The experimental results showed that the chiral stationary phase exhibits good selectivity for linear alkanes, linear alcohols, polycyclic aromatic hydrocarbons, isomers, and chiral compounds. In addition, the column has the advantages of high column efficiency and short analysis time. The present work indicated that amorphous metal–organic polyhedra have great potential for application as a new type of stationary phase for GC.
- Tang, Bo,Sun, Chenyu,Wang, Wei,Geng, Lina,Sun, Liquan,Luo, Aiqin
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p. 1178 - 1185
(2020/07/09)
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- An enantioselective claisen rearrangement catalyzed by N-heterocyclic carbenes
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In the presence of a chiral azolium salt (10 mol %), enols and ynals undergo a highly enantioselective annulation reaction to form enantiomerically enriched dihydropyranones via an N-heterocyclic carbene catalyzed variant of the Claisen rearrangement. Unlike other azolium-catalyzed reactions, this process requires no added base to generate the putative NHC-catalyst, and our investigations demonstrate that the counterion of the azolium salt plays a key role in the formation of the catalytically active species. Detailed kinetic studies eliminate a potential 1,4-addition as the mechanistic pathway; the observed rate law and activation parameters are consistent with a Claisen rearrangement as the rate-limiting step. This catalytic system was applied to the synthesis of enantioenriched kojic acid derivatives, a reaction of demonstrated synthetic utility for which other methods for catalytic enantioselective Claisen rearrangements have not provided a satisfactory solution.
- Kaeobamrung, Juthanat,Mahatthananchai, Jessada,Zheng, Pinguan,Bode, Jeffrey W.
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supporting information; experimental part
p. 8810 - 8812
(2010/08/21)
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- Enantioselective Synthesis of Succinic Acids and γ-Lactones via Palladium Catalysed Allylic Substitution Reactions
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The palladium catalyzed reaction between non-symmetrical allyl acetates and sodiodimethylmalonate proceeds in high yields and enantioselectivities (up to 99percent ee) using a diphenylphosphinoaryl oxazoline ligand.The so-formed substitution products are transformed into enantiomerically enriched succinic acids and also into enantiomerically enriched γ-lactones.
- Dawson, Graham J.,Williams, Jonathan M. J.,Coote, Steven J.
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p. 2535 - 2546
(2007/10/03)
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- Influence of β-arranged substituents in chiral seven-membered rhodium diphosphine rings on asymmetric hydrogenation of amino acid precursors
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Investigations concerning the optical induction in asymmetric hydrogenation reactions confirm the stereochemical control function of mono- and di-substituents in seven-membered chelate ring diphosphines, whereby the bulkiness of substituents in the backbone of the ligands is reflected in higher enantioselectivities.
- Krause, Hanswalter,Sailer, Cornelia
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p. 271 - 279
(2007/10/02)
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- ENANTIOSELEKTIVE KATALYSE, 63 - OPTISCH AKTIVE PHOSPHINE AUS DICARBONSAEUREN UND IHR EINSATZ IN DER ENANTIOSELEKTIVEN HYDRIERUNG
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Two optically active bident phosphine ligands were synthesized from derivatives of succinic acid as starting materials.The optical resolution of the acids was carried out with cinchonidine and (S)-α-phenylethylamine.In the Rh-catalyzed enantioselective hydrogenation of α-acetamidocinnamic acid, the bisphosphine with a phenyl substituent in the 2-position of the four-carbon chain gave enantiomeric excess of 17percent.The enantiomeric excess was twice as high with the corresponding thienyl substituted biphosphine.
- Brunner, H.,Zettlmeier, W.
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p. 259 - 265
(2007/10/02)
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- Asymmetric Synthesis. Part 6. Copper Salt promoted Grignard Reagent Additions to Ethyl 2,3-Dideoxy-4,5:6,7-di-O-isopropylidene-D-arabino-trans-hept-2-enonate and subsequent Formation of Optically Active 2-Alkyl (or Aryl) Butane-1,4-dioic Acids and Butyro-1,4-lactones
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The copper-salt promoted 1,4-additions of aryl and t-butyl Grignard reagents to ethyl 2,3-dideoxy-4,5:6,7-di-O-isopropylidene-D-arabino-trans-hept-2-enonate are highly stereoselective yielding products with the D-manno-configuration.In contrast isopropyl and ethyl Grignarg reagents give products preponderantly with the D-gluco-configuration.Cyclohexylmagnesium bromide does not react stereoselectively but gives a 55:45 mixture of the D-gluco- and D-manno-isomers.Controlled degradation of the carbohydrate molecule affords 2-aryl (alkyl) butane-1,4-dioic acids and 3-aryl (alkyl)-butyro-1,4-lactones.The enantiomeric purity of these products is established by reference to known products or by use of optically active n.m.r. shift reagents.
- Lawston, Ian W.,Inch, Thomas D.
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p. 2629 - 2635
(2007/10/02)
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- On the Absolute Configuration of (+)-Indane-1-carboxylic Acid
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The (R)-configuration, attributed to (+)-indane-carboxylic acid ((+)-1) by Fredga, is unequivocally confirmed (Scheme 1).Configurational doubts, raised by an erroneous ORD. curve of (-)-1-methylindane ((-)-4) published by Brewster and Buta, are unfounded (cf. the following paper of Brewster and the corrections in ).This was further verified by preparing deuteriated 1-methylindanes starting with (-)-(R)-3-phenylbutyric acid ((-)-(R)-5) as well as with (+)-(R)-1 or (-)-(S)-1 (Scheme 2).The ORD. curves of the optically active 4 thus obtained were (disregarding deuterium isotope effects) identical or antipodal, respectively (cf.Fig.1,2, and 7a-e).Optically active methyl indane-1-carboxylates ((-)-(R)-14 or (+)-(S)--14) show a strong solvent dependence of their ORD. and CD. spectra with a sign inversion occuring in going from isooctane to methanol or benzene.The observed changes can be explained by a change in the population of comformations where the ester carbonyl group is eclipsed either with the C(1),C(2)- or C(1),H-bond, with the n,?*-transition having a slightly different energy and the ester group an essentially enantiomeric environment with respect to its orientation relative to the benzene moiety.
- Hansen, Hans-Juergen,Sliwka, Hans-Richard,Hug, Werner
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p. 325 - 343
(2007/10/02)
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