نتایج جستجو برای: asymmetric catalyst
تعداد نتایج: 108514 فیلتر نتایج به سال:
A novel strain, Microbacterium sp., which can be used as a catalyst in the asymmetric reduction of simple aromatic ketones to produce chiral aromatic alcohols, was isolated from soil by microbial screening. Using acetophenone as a model substrate for asymmetric reduction, 82 % reaction yield with more than 99 % enantiomeric excess of (R)-1-phenylethanol were achieved under the optimal condition...
A novel ionic liquid-support organocatalyst, which contains the quaternary ammonium ion moiety, was recently developed and successfully applied to the asymmetric Michael reaction in the presence of a newly developed ionic liquid-supported (ILS) benzoic acid as co-catalyst. For the reactions studied, in which various aldehydes and nitroolefins were examined, excellent diastereo- and enantioselec...
An asymmetric ring-opening reaction of meso-aziridines with TMSN3 was developed using a catalyst prepared from Y(OiPr)3 and chiral ligand 2 in a 1:2 ratio. Excellent enantioselectivity was realized from a wide range of substrates with a practical catalyst loading. The products were efficiently converted to enantiomerically enriched 1,2-diamines, which are versatile chiral building blocks for ph...
The catalytic asymmetric hydrogenation of heteroarenes has been intensively studied during the last decade. Nowadays, various heteroaromatics, for example, indoles, pyrroles, and quinolines, can be reduced to the corresponding chiral heterocycles with high stereoselectivity through asymmetric catalysis. Glorius and co-workers recently found that a chiral N-heterocyclic carbene–ruthenium catalys...
A new asymmetric organocatalyzed intramolecular aza-Michael reaction by means of both a chiral auxiliary and a catalyst for stereocontrol is reported for the synthesis of optically active isoindolinones. A selected cinchoninium salt was used as phase-transfer catalyst in combination with a chiral nucleophile, a Michael acceptor and a base to provide 3-substituted isoindolinones in good yields a...
As an alternative to conventional asymmetric hydroformylation (AHF), asymmetric transfer hydroformylation (ATHF) by using formaldehyde as a surrogate for syngas is reported. A catalyst derived from commercially available [Rh(acac)(CO)2 ] (acac=acetylacetonate) and 1,2-bis[(2S,5S)-2,5-diphenylphospholano]ethane(1,5-cyclooctadiene) (Ph-BPE) stands out in terms of both activity and enantioselectiv...
Chiral carbohydrate-based diphosphites were used for Pd-catalysed asymmetric allylic substitution (alkylation, amination, phosphination) in neat ionic liquids (ILs). Pyrrolidinium-based IL led to the best activities, allowing an efficient catalyst immobilization. In the allylic amination (TOF > 3100 h(-1)), the catalyst could be recycled nine times preserving both activity and enantioselectivity.
A new synthetic route to optically active unsaturated γ- and δ-lactones has been demonstrated via asymmetric allylic carboxylation with a planar-chiral Cp'Ru catalyst and ring-closing metathesis reaction with a Grubbs II catalyst, and successfully applied to the enantioselective synthesis of (R)-(-)-massoialactone.
A series of acid-labile, optically pure ε-substituted δ-ketal-β-hydroxy esters were obtained by a Ru-SunPhos catalyzed asymmetric hydrogenation of the corresponding ε-substituted δ-ketal-β-keto esters. CaCO(3) played a dual role in the hydrogenation reaction--removing the acid generated during the formation of the catalyst and maintaining the activity of the catalyst.
A mild catalyst system for the synthesis of chiral amino alcohols via asymmetric transfer hydrogenation (ATH) of α-phthalimide ketones has been developed by using a chiral Ru-TsDPEN complex as the catalyst in DMF/MeOH at 40 °C. The reaction exhibits high reaction activity and excellent enantioselectivity where up to 96% yield and 99% ee of the product were obtained.
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