Asymmetric Hydrogenation
Mostrando 1-12 de 14 artigos, teses e dissertações.
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1. Asymmetric transfer hydrogenation of ketones in aqueous solution catalyzed by rhodium(III) complexes with C2-symmetric fluorene-ligands containing chiral (1R,2R)-cyclohexane-1,2-diamine
Dois ligantes C2-simétricos bis(sulfonamide) contendo o fluoreno-quiral (1R,2R)-ciclohexano-1,2-diamina foram complexados com RhIII(Cp*) e usados como catalizador para redução aromática de cetonas. Os alcoois secundários correspondentes foram obtidos com ee 87-100% e rendimento de 85-99%, sob condições de transferência de hidrogenio assimétrica (THA
Journal of the Brazilian Chemical Society. Publicado em: 2010
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2. The asymmetric total synthesis of (+)- and (-)-trypargine via Noyori asymmetric transfer hydrogenation
Uma síntese total e eficiente da (+) e (-)-tripargina, alcalóide β-carbolínico isolado da pele da rã africana K. Senegalensis, foi realizada em 6 etapas e 38% de rendimento global, a partir da triptamina, tendo como base a construção do sistema β-carbolínico via reação de Bischler-Napieralski e a redução enantiosseletiva do intermediário diidro
Journal of the Brazilian Chemical Society. Publicado em: 2009
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3. Síntese assimétrica do (+)- e do (-)-mutisiantol e obtenção de 1-tetralóis opticamente ativos / Asymmetric synthesis of (+)- and (-)-mutisianthol and preparation of optically active 1-tetralols
Esta tese descreve a primeira síntese assimétrica do sesquiterpeno fenólico (+)-(1S, 3R)-mutisiantol, assim como de seu enantiômero não-natural. O (+)-mutisiantol foi obtido em 11 etapas a partir do 2-metil-anisol, em rendimento global de 14% e excesso enantiomérico de 90%. Estas sínteses permitiram determinar a configuração absoluta deste produto n
Publicado em: 2008
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4. Ligantes quirais nitrogenados em reações de hidrogenação catalitica assimetrica e redução enantiosseletiva com oxazaborolidinas / Nitrogen chiral ligants in asymmetric hydrogenation and enantioselective reduction using oxazaborolidine
O presente trabalho tem como objetivo a síntese e aplicação de novos aminoálcoois e ligantes quirais fosforados derivados desses e sua aplicação em catálise assimétrica. Com este intuito, foram sintetizados os aminoálcoois (2R)-2-[(2R) azolan-2-il]-2-feniletan-1-ol (4) e (2R)-2-[(2R) hexaidro-2-piridinil]-2-feniletan-1-ol (6) que são inéditos na l
Publicado em: 2005
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5. A Interação substrato-modificador e sua importância para a hidrogenação enantiosseletiva de alfa-cetoésteres
The heterogeneous asymmetric catalysis plays an important and crucial role in many chemical processes and has therefore become a growing and interesting field. The enantioselective hydrogenation of α-ketoesters is one of the best known examples of such process. Methyl pyruvate, which can be converted to (R)- and (S)-methyl lactate with an enantioselecti
Publicado em: 2004
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6. Estudo quimioenzimatico da sintese de um analogo do residuo N-terminal de nikkomicinas
Nikkomycins belong to a group of nucleoside peptides antibiotics produced by streptomycets. These compounds are potent chitin synthetase inhibitors and they exhibit fungicidal, insecticidal, and acaricidal activities. Our approach began with an asymmetric reduction of ethyl benzoylacetate 37. We evaluate the biocatalytic potential of some brazilian microorga
Publicado em: 2003
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7. Enantioselective synthesis of aziridines using asymmetric transfer hydrogenation as a precursor for chiral derivatives used as bonding agent for rocket solid propellants
A rapid, expedient and enantioselective method for the synthesis of beta-hydroxy amines and monosubstituted aziridines in up to 99% e.e., via asymmetric transfer hydrogenation of a-amino ketones and cyclisation through treatment with tosyl chloride and base, is described. (1R,2R)-N-(para-toluenesulfonyl)-1,2-ethylenediamine with formic acid has been utilised
Química Nova. Publicado em: 2002-11
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8. Asymmetric hydrogenation of α,β-unsaturated phosphonates with Rh-BisP* and Rh-MiniPHOS catalysts: Scope and mechanism of the reaction
Optically active 1,2-bis(alkylmethylphosphino)ethanes and bis(alkylmethylphosphino)methanes are unique diphosphine ligands combining the simple molecular structure and P-stereogenic asymmetric environment. This work shows that these ligands exhibit excellent enantioselectivity in rhodium-catalyzed asymmetric hydrogenation of α,β-unsaturated phosphonic acid
National Academy of Sciences.
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9. Toward efficient asymmetric hydrogenation: Architectural and functional engineering of chiral molecular catalysts
Asymmetric hydrogenation uses inexpensive, clean hydrogen gas and a very small amount of a chiral molecular catalyst, providing the most powerful way to produce a wide array of enantio-enriched compounds in a large quantity without forming any waste. The recent revolutionary advances in this field have entirely changed the synthetic approach to producing per
National Academy of Sciences.
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10. Chiral biphenyl diphosphines for asymmetric catalysis: Stereoelectronic design and industrial perspectives
Two original chiral diphosphines, SYNPHOS and DIFLUORPHOS, have been synthesized on multigram scales. Their steric and electronic profiles have been established in comparison with the commonly used 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl and 6,6′-dimethoxy-2,2′-bis(diphenylphosphino)-1,1′-biphenyl ligands. A screening study of the four ligands
National Academy of Sciences.
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11. Remarkably diastereoselective synthesis of a chiral biphenyl diphosphine ligand and its application in asymmetric hydrogenation
Essentially complete atropdiastereoselectivity was realized in the preparation of biaryl diphosphine dioxide by asymmetric intramolecular Ullmann coupling and oxidative coupling with central-to-axial chirality transfer. A bridged C2-symmetric biphenyl phosphine ligand possessing additional chiral centers on the linking unit of the biphenyl groups was synthes
National Academy of Sciences.
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12. Catalysis-based enantioselective total synthesis of the macrocyclic spermidine alkaloid isooncinotine
A concise and efficient total synthesis of the spermidine alkaloid (-)-isooncinotine (1) incorporating a 22-membered lactam ring is outlined. The approach is largely catalysis-based, involving a selective iron-catalyzed alkyl–aryl cross-coupling reaction of a difunctionalized pyridine substrate, a heterogeneous asymmetric hydrogenation step to set the chir
National Academy of Sciences.