- 19F NMR non-equivalence of diastereomeric amides of 2,2,2-trifluoro-1-phenylethylamine
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An alternate synthesis and resolution is reported for 2,2,2-trifluoro-1-phenylethylamine. The 19F NMR of a series of amide derivatives of chiral acids is described. The diastereomeric non-equivalence of the 19F NMR signals (0.05-0.09 ppm) of these amides permits use of these derivatives for determination of enantiomeric purity of alpha-substituted acids. The potential for configurational correlations is discussed.
- Wang,Mosher
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- The effect of chiral: N-substituents with methyl or trifluoromethyl groups on the catalytic performance of mono-and bifunctional thioureas
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We evaluated thiourea organocatalysts that incorporate a chiral group which includes a trifluoromethyl moiety and contrasted their performance with non-fluorinated analogs. The comparison between such systems allows the direct study of the NH acidity of a thiourea bonded to an aliphatic substituent. In principle,-CF3 systems feature an enhanced hydrogen bond (HB) donor capacity that is undoubtedly beneficial for HB-catalysis applied to the Baylis-Hillman reaction. We found that the thiourea substituted on both nitrogens with this group accelerates this reaction like Schreiner's thiourea. On the other hand, we observed a different behavior in reactions promoted by bifunctional catalysts (thiourea-primary amine). In the Michael addition of isobutyraldehyde to methyl benzylidenepyruvate, the-CF3 containing catalysts were better than the-CH3 systems, whereas the conjugate addition to N-phenylmaleimide showed the opposite behavior. Theoretical calculations of the transition states indicated that the phenylethyl group in fluorinated and non-fluorinated compounds have different kinds of interactions with the electrophile. These interactions are responsible for a different arrangement of the electrophile and thereby the selectivity of the catalyst. Therefore, it cannot be generalized that in all cases NH acidity correlates with the performance of the catalyst, particularly, with aliphatic substituents that unlike the aromatic ones possess groups that are outside the plane of the thiourea.
- Vazquez-Chavez, Josué,Luna-Morales, Socorro,Cruz-Aguilar, Diego A.,Díaz-Salazar, Howard,Vallejo Narváez, Wilmer E.,Silva-Gutiérrez, Rodrigo S.,Hernández-Ortega, Simón,Rocha-Rinza, Tomás,Hernández-Rodríguez, Marcos
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supporting information
p. 10045 - 10051
(2019/12/23)
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- Bifunctional Thioureas with α-Trifluoromethyl or Methyl Groups: Comparison of Catalytic Performance in Michael Additions
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Thioureas are an important scaffold in organocatalysis because of their ability to form hydrogen bonds that activate substrates and fix them in a defined position, which allows a given reaction to occur. Structures that enhance the acidity of the thiourea are usually used to increase the hydrogen-bonding properties, such as 3,5-bis(trifluoromethyl)phenyl and boronate ureas. Herein, we report the synthesis of bifunctional thioureas with a chiral moiety that include either a trifluoromethyl or methyl group. Their catalytic performance in representative Michael addition reactions was used in an effort to compare the electronic effects of the fluorination at the methyl group. The observed differences concerning yields and ee values cannot be attributed solely to the different steric environments; theoretical results indicate distinct interactions within the corresponding transition states. The calculated transition states show that the fluorinated catalysts have stronger N-H···O and C-H···F hydrogen bonds, while the nonfluorinated systems have C-H···π contacts. These results have shown that a variety of hydrogen-bonding interactions are important in determining the yield and selectivity of thiourea organocatalysis. These details can be further exploited in catalyst design.
- Jiménez, Eddy I.,Vallejo Narváez, Wilmer E.,Román-Chavarría, Carlos A.,Vazquez-Chavez, Josue,Rocha-Rinza, Tomás,Hernández-Rodríguez, Marcos
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p. 7419 - 7431
(2016/09/09)
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- Asymmetric Biocatalytic Amination of Ketones at the Expense of NH3 and Molecular Hydrogen
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A biocatalytic system is presented for the stereoselective amination of ketones at the expense of NH3 and molecular hydrogen. By using a NAD+-reducing hydrogenase, an alanine dehydrogenase, and a suitable ω-transaminase, the R- as well as the S-enantiomer of various amines could be prepared with up to >99% ee and 98% conversion. (Chemical Equation Presented).
- Holzer, Anja K.,Hiebler, Katharina,Mutti, Francesco G.,Simon, Robert C.,Lauterbach, Lars,Lenz, Oliver,Kroutil, Wolfgang
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supporting information
p. 2431 - 2433
(2015/06/02)
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- Chemoenzymatic dynamic kinetic resolution of α-trifluoromethylated amines: Influence of substitutions on the reversed stereoselectivity
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Enzymatic resolution of α-trifluoromethylated amines via kinetic resolution (KR), dynamic kinetic resolution (DKR) employing CALB-Pd/Al 2O3, and a one-pot sequential process of KR/DKR/KR was investigated comparatively for the first time. Although CALB-catalyzed KR of α-trifluoromethylated amines with substituents of methyl (1a), isopropyl (1c), phenyl (1d) and benzyl group (1e) can provide good stereoselectivity factors E from 31 to >200 respectively, DKR and sequential process of KR/DKR/KR possess better practical application potential because of the higher conversion (62%-84%) and the similar enantiomeric excesses (90%-99%). The enantiopreference and inversion for the α-trifluoromethylated amines displayed by CALB were observed and explained by docking modes. Namely, for 1,1,1-trifluoro-2-propylamine (1a), the product amide with R-configuration was obtained, and the enantiopreference was converted to S for the amines (1b-1e) with substituents larger than methyl group. The catalysts recycle, and scale-up experiments were demonstrated successfully. All these results indicated the high efficiency and green feature of this enzymatic process, and its application significance.
- Cheng, Guilin,Xia, Bo,Wu, Qi,Lin, Xianfu
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p. 9820 - 9828
(2013/09/02)
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- TRPV4 ANTAGONISTS
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The present invention relates to quinoline analogs, pharmaceutical compositions containing them and their use as TRPV4 antagonists.
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Page/Page column 40
(2011/10/13)
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- PYRROLO [3, 2 -E] [1,2,4] TRIAZOLO [1,5 -A] PYRIMIDINES DERIVATIVES AS INHIBITORS OF MICROGLIA ACTIVATION
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The invention relates to novel compounds useful in the treatment and prophylaxis of disease. Compounds of the formula (I) wherein X is halogen, independently selected form chlorine and fluorine and n is 0, 1 or 2. and their pharmaceutically acceptable salts are useful in the treatment and prophylaxis of diseases caused by activation of microglia, particularly Alzheimer's disease.
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Page/Page column 16
(2011/04/26)
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- Enantioselective Pd-catalyzed hydrogenation of fluorinated imines: Facile access to chiral fluorinated amines
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An enantioselective hydrogenation of simple fluorinated imines has been developed using Pd(OCOCF3)2/(R)-Cl-MeO-BIPHEP as a catalyst, and up to 94% ee was achieved. This method provides an efficient route to enantioenriched fluorinated amines.
- Chen, Mu-Wang,Duan, Ying,Chen, Qing-An,Wang, Duo-Sheng,Yu, Chang-Bin,Zhou, Yong-Gui
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supporting information; experimental part
p. 5075 - 5077
(2011/02/19)
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- Enantiodivergent approach to trifluoromethylated amines: A concise route to both enantiomeric analogues of calcimimetic NPS R-568
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Reported herein is a straightforward and enantiodivergent synthesis of both enantiomers of trifluoromethylated analogues of calcimimetic NPS R-569 in a highly estereoselective manner. The synthesis features a diastereoselective synthesis of the N-(isopropylsulfinyl)imine unit by the "DAG methodology" and a diastereoselective addition of Ruppert Prakash's reagent to the imine as the key steps. No protecting groups were necessary, permitting an atom economic synthesis in only six steps. Further addition reactions of the CF3 anion to different N-(isopropylsulfinyl)imines were performed to demonstrate the suitability of the sulfinyl substituent to balance perfectly reactivity and diastereoselectivity.
- Fernandez, Inmaculada,Valdivia, Victoria,Alcudia, Ana,Chelouan, Ahmed,Khiar, Noureddine
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experimental part
p. 1502 - 1509
(2010/06/15)
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- Synthesis of Chiral Trifluoromethylated Amines by Palladium-Catalyzed Diastereoselective Hydrogenation-Hydrogenolysis Approach
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The synthesis of chiral 2,2,2-trifluoro-1-phenylethylamines by palladium-catalyzed diastereoselective heterogeneous catalytic hydrogenation is described. The one-pot process involves two steps; the diastereoselective hydrogenation of chiral 2,2,2-trifluoro-1-phenylethyl-N-1'-phenylethylimines and the hydrogenolysis of the methylbenzyl group on the amino function. During both the hydrogenation and hydrogenolysis steps favorable stereoinduction was observed, and the products were obtained in 90-93% ee and 50-55% yield.
- Toeroek, Bela,Prakash, G. K. Surya
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p. 165 - 168
(2007/10/03)
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- Asymmetric addition reactions of Grignard reagents to chiral fluoral hemiacetal: Asymmetric synthesis of 1-substituted-2,2,2-trifluoroethylamines
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Asymmetric synthesis of 1-substituted-2,2,2-trifluoroethylamines is described starting from chiral fluoral hemiacetals derived from fluoral and (R)-phenylglycinol. The asymmetric addition reactions of Grignard reagents to the resultant imine are used in the key reaction step.
- Ishii, Akihiro,Higashiyama, Kimio,Mikami, Koichi
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p. 1381 - 1382
(2007/10/03)
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