- Ionization Equilibria in Dicarboxylic Acids Undergoing Conformational Transitions
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Succinic acid and substituted succinic acids undergo conformational transitions during ionization, and these are expected to affect their ionization equilibrium.An analysis of this effect is presented. 1H NMR data on the dependence of the conformational e
- Morawetz, Herbert,Choi, Ling-Siu
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- Low-barrier hydrogen bonding in aqueous and aprotic solutions of dicarboxylic acids: Spectroscopic characterization
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We present additional spectroscopic evidence for the formation of low- barrier hydrogen bonds (LBHBs) within vicinal and geminal dicarboxylic acid monoanions. Hydrogen cis-cyclohexane 1,2-dicarboxylate, displays low-field 1H NMR signals in apro
- Cassidy, Constance S.,Lin, Jing,Tobin, John B.,Frey, Perry A.
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- Highly-efficient Ru/Al-SBA-15 catalysts with strong Lewis acid sites for the water-assisted hydrogenation of: P -phthalic acid
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Ruthenium nanoparticles supported onto aluminum-doped mesoporous silica catalysts (Ru/Al-SBA-15) are fabricated using hydrothermal and impregnation methods for catalysis application. The Ru/Al-SBA-15-3 catalyst at a Si/Al molar ratio of 3 exhibited excellent catalytic performance for the hydrogenation of p-phthalic acid with high conversion efficiency (100.0%) and cis-isomer selectivity (84.0%) in water. Moreover, this system displays exceptional stability and recyclability through preserving the conversion efficiency, as well as a cis-isomer selectivity of 90.2 and 83.3%, respectively, after reusing it fourteen times. Such an exceptional system can also be ideal for the hydrogenation of aromatic dicarboxylic acids and their ester derivatives in water. Strong Lewis acid sites due to doped Al species play significant roles in the hydrogenation reaction. Moreover, isotope labeling studies indicated that water molecules effectively participated in the hydrogenation reaction. Hydrogen and water contributed half of the hydrogen atoms for this hydrogenation reaction. In the end, a plausible mechanistic pathway for the hydrogenation of p-phthalic acid using the Ru/Al-SBA-15-3 catalyst in water is proposed.
- Ahamad, Tansir,Kankala, Ranjith Kumar,Mao, Cong,Matsagar, Babasaheb M.,Wu, Kevin C.-W.,Yang, Yucheng,Zhang, Xueqin,Zheng, Jingwei
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p. 2443 - 2451
(2020/05/14)
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- Enantioselective Synthesis of ((1 R,2 R)-Cyclohexane-1,2-diyl)bis(methylene)dimethanesulfonate, a Lurasidone Hydrochloride Intermediate
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A concise, economical, and highly enantioselective synthesis of bismesylate intermediate of lurasidone HCl, an antipsychotic, has been developed. The key steps involved in the synthesis are thionyl chloride-catalyzed esterification of tetrahydrophthalic anhydride in MeOH, epimerization of cis to trans isomer, hydrolysis of the diester, resolution of the diacid, reduction with Red-Al, and finally bismesylation of the corresponding diol, which provided the desired intermediate ((1 R,2 R)-cyclohexane-1,2-diyl)bis(methylene) dimethanesulfonate in overall good yield.
- Ravi Ganesh,Pachore, Sharad S.,Pratap,Umesh,Basaveswara Rao,Murthy,Suresh Babu
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supporting information
p. 2676 - 2682
(2015/12/18)
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- Straightforward synthesis of 1,2-dicyanoalkanes from nitroalkenes and silyl cyanide mediated by tetrabutylammonium fluoride
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A straightforward synthesis of 1,2-dicyanoalkanes by reacting nitroalkenes with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride is described. The reaction proceeds through a tandem double Michael addition under mild conditions. Employing the hypervalent silicate generated from trimethylsilyl cyanide and tetrabutylammonium fluoride is essential for achieving this transformation. Mechanistic studies suggest that a small amount of water included in the reaction media plays a key role. This protocol is applicable to various types of substrates including electron-rich and electron-deficient aromatic nitroalkenes, and aliphatic nitroalkenes. Moreover, vinyl sulfones were found to be good alternatives, particularly for electron-deficient nitroalkenes. The broad substrate scope and functional group tolerance of the reaction makes this approach a practical method for the synthesis of valuable 1,2-dicyanoalkanes.
- Kiyokawa, Kensuke,Nagata, Takaya,Hayakawa, Junpei,Minakata, Satoshi
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p. 1280 - 1285
(2015/02/19)
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- Lipophilic oligopeptides for chemo- and enantioselective acyl transfer reactions onto alcohols
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Inspired by the extraordinary selectivities of acylases, we envisioned the use of lipophilic oligopeptidic organocatalysts for the acylative kinetic resolution/desymmetrization of rac- and meso-cycloalkane-1,2-diols. Here we describe in a full account the discovery and development process from the theoretical concept to the final catalyst, including scope and limitations. Competition experiments with various alcohols and electrophiles show the full potential of the employed oligopeptides. Additionally, we utilized NMR and IR-spectroscopic methods as well as computations to shed light on the factors responsible for the selectivity. The catalyst system can be readily modified to a multicatalyst by adding other catalytically active amino acids to the peptide backbone, enabling the stereoselective one-pot synthesis of complex molecules from simple starting materials.
- Mueller, Christian E.,Zell, Daniela,Hrdina, Radim,Wende, Raffael C.,Wanka, Lukas,Schuler, Soeren M. M.,Schreiner, Peter R.
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p. 8465 - 8484
(2013/09/24)
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- Efficient and Practical Arene Hydrogenation by Heterogeneous Catalysts under Mild Conditions
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An efficient and practical arene hydrogenation procedure based on the use of heterogeneous platinum group catalysts has been developed. Rh/C is the most effective catalyst for the hydrogenation of the aromatic ring, which can be conducted in iPrOH under neutral conditions and at ordinary to medium H 2 pressures (10 atm). A variety of arenes such as alkylbenzenes, benzoic acids, pyridines, furans, are hydrogenated to the corresponding cyclohexyl and heterocyclic compounds in good to excellet yields. The use of Ru/C, less expensive than Rh/C, affords an effective and practical method for the hydrogenation of arenes including phenols. Both catalysts can be reused several times after simple filtration without any significant loss of catalytic activity.
- Maegawa, Tomohiro,Akashi, Akira,Yaguchi, Kiichiro,Iwasaki, Yohei,Shigetsura, Masahiro,Monguchi, Yasunari,Sajiki, Hironao
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experimental part
p. 6953 - 6963
(2010/02/28)
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- Spontaneous formation and stabilization of radicals during the cocrystallization of alicyclic and peroxyalicyclic dicarboxylic acids
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The cocrystallization of di(cis-2-carboxycyclohexylcarbonyl) peroxide and cyclohexane-1,2-dicarboxylic acid from aqueous solution affords stable 1-carboxycyclohexyl radicals, which were identified by EPR spectroscopy.
- Starostin, Evgenii K.,Lalov, Andrei V.,Ignatenko, Anatolii V.,Nikishin, Gennady I.
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p. 123 - 125
(2008/09/21)
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- Rational tuning chelate size of bis-oxazoline ligands to improve enantioselectivity in the asymmetric aziridination of chalcones
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Chalcones were asymmetrically aziridinated with [N-(p-toluenesulfonyl) imino]phenyliodinane (PhI=NTs) as a nitrene source under catalysis of CuOTf and a series of cyclohexane-linked bis-oxazolines (cHBOXes), which are chelate size rationally tuned bis-oxazolines. The results indicate that highly enantioselective aziridination of chalcones with up to >99% ee have been achieved under catalysis of (S,S)-1,2-bis[(S)-(4-phenyl)oxazolin-2-yl] cyclohexane, which is the most-matched stereoisomer among cyclohexane-linked bis-oxazolines. It was also found that the enantioselectivity is not substituent-dependent with respect to chalcones in the present case, unlike with 1,8-anthracene-linked bis-oxazolines (AnBOXes).
- Ma, Linge,Du, Da-Ming,Xu, Jiaxi
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p. 10155 - 10158
(2007/10/03)
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- Enantiomerically pure β-amino acids: A convenient access to both enantiomers of trans-2-aminocyclohexanecarboxylic acid
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Enantiomerically pure trans-2-aminocyclohexanecarboxylic acid is an important building block for helical β-peptides. We report here that this amino acid can be obtained from trans-cyclohexane-1,2-dicarboxylic acid in good yield by a simple one-pot procedure comprising cyclization to the anhydride, amide formation with ammonia, and a subsequent Hofmann-type degradation with phenyliodine(III) bis(trifluoroacetate) (PIFA) as the oxidant. The N-Fmoc- and N-BOC-protected derivatives were obtained by treatment of the amino acid with Fmoc-OSu and BOC2O, respectively. The N-BOC derivative could be prepared in even better overall yield by a one-pot procedure leading directly from trans-cyclohexane-1,2-dicarboxylic acid to the N-BOC-protected amino acid. Both enantiomers of the starting trans-1,2-cyclohexanedicarboxylic acid can be obtained easily and in large quantities by separating commercially available racemic trans-1,2-cyclohexanedicarboxylic acid using either (R)- or (S)-1-phenethylamine. X-ray crystallography of the diastereomerically pure salt obtained from (R)-1-phenethylamine revealed that the configuration of the diacid component is (1R,2R), and not (1S,2S) as reported in the literature. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Berkessel, Albrecht,Glaubitz, Katja,Lex, Johann
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p. 2948 - 2952
(2007/10/03)
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- Rhodococcus rhodochrous IFO 15564-mediated hydrolysis of alicyclic nitriles and amides: Stereoselectivity and use for kinetic resolution and asymmetrization
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The stereocourse and the selectivity of the hydrolysis of alicyclic mono- and dinitriles and amides mediated by Rhodococcus rhodochrous IFO · 15564 has been examined. The stereochemistry of the substrates, as well as the nature of substituents and presence of double bonds in alicyclic rings greatly affected the rate of hydrolysis by nitrile hydratase and amidase. The rate difference between enantiomers or enantiotopic groups, in some cases, enabled kinetic resolution or asymmetrization. The highest enantioselectivity of amidase was observed in the hydrolysis of 5-benzoyloxy-3-cyclohexene-1- carboxamide (E>200), and both enantiomers of methyl 5-hydroxy-3-cyclohexene- 1-carboxylate thus became readily available.
- Matoishi, Kaori,Sano, Akio,Imai, Nori,Yamazaki, Takahiro,Yokoyama, Masahiro,Sugai, Takeshi,Ohta, Hiromichi
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p. 1097 - 1102
(2007/10/03)
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- Synthesis of new C2-symmetrical diphosphines using chiral zinc organometallics
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The new C2-symmetrical diphosphines 1-4 of potential interest for asymmetric catalysis were prepared in protected form by a convergent synthesis based on the use of readily available (S,S)-1,2-cyclohexanedicarboxylic acid 8 and the phosphorus reagent (Et2N)2PLi·BH3.
- Longeau, Alexia,Durand, Sandrine,Spiegel, Anja,Knoechel, Paul
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p. 987 - 990
(2007/10/03)
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- CARBOXY AND SUBSTITUTED CARBOXY ALKANOYL AND CYCLOALKANOYL PEPTIDES
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Peptides of the formula STR1 wherein X is various amino or imino acids or esters are useful as hypotensive agents.
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- Method of preparing permissibly-substituted 1H(and 2H)pyrazolo[3,4-g]quinolines; pyrimido[4,5,g]quinolines; thiazolo[4,5,g]quinolines and intermediates therefore
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Trans-(±)-1-permissibly-substituted-2,6-dioxodecahydroquinoline or enantiomers thereof, intermediates for preparing tautomeric trans-(±)-5-permissibly substituted octahydro-1H(and 2H)pyrazolo[3,4-g]quinolines, 4aR,8aR or 4aS,8aS enantiomers thereof, for p
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- A Study of Stereoselective Hydrolysis of Symmetrical Diesters with Pig Liver Esterase
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Pig liver esterase (PLE) catalyzed hydrolysis of dimethyl esters of symmetrical dicarboxylic acids, including meso-diacids, cis-1,2-cycloalkanedicarboxylic acids, and diacids with a prochiral center, was studied with 14 substrates.The products of these stereoselective hydrolyses are chiral monoesters of dicarboxylic acids, with an enantiomeric excess (e.e.) from 10percent to 100percent.Some of these optically active monoesters are valuable synthons in natural products synthesis.An additivity pattern of α- and β-substituents with the glutaric esters on the stereoselectivity of enzymatic hydrolysis was observed.Analysis of the experimental results leads to a model of enzyme stereoselectivity of diester hydrolysis in which the substitution pattern at α- and β-C-atoms is found to determine the absolute configuration of the resulting monoester.
- Mohr, Peter,Waespe-Sarcevic, Nada,Tamm, Christoph,Gawronska, Krystyna,Gawronsky, Jacek K.
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p. 2501 - 2511
(2007/10/02)
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