نتایج جستجو برای: enantiomeric excess
تعداد نتایج: 75059 فیلتر نتایج به سال:
We report the chiral diene ligated rhodium-catalyzed dynamic kinetic asymmetric transformation (DYKAT) of racemic secondary allylic trichloroacetimidates with a variety of N-methyl anilines, providing allylic N-methyl arylamines in high yields, regioselectivity, and enantiomeric excess. The rhodium-catalyzed DYKAT method addresses limitations previously associated with this particular class of ...
The reaction between 3-methyl-4-nitro-5-styrylisoxazoles and ethyl isocyanoacetate proceeded under phase transfer catalysis to give enantioenriched monoadducts in high enantiomeric excess (up to 99% ee). The resulting adducts were subsequently cyclised to give 2,3-dihydropyrroles and substituted pyrrolidines in identical high ees and as a single diastereoisomer.
This study reports (1S,2S)-N,N'-dihydroxy-N,N'-bis(diphenylacetyl)-1,2-cyclohexanediamine, a C2 symmetric chiral hydroxamic acid ((S)-CBHA-DPA), as a unique probe for discrimination of molecules with diverse functionalities. The proposed CSA is also utilized for the accurate measurement of enantiomeric excess.
This work features first asymmetric Ni-catalyzed reductive coupling of allylic carbonates with aldehydes, which may proceed via allyl-Ni intermediates although Zn was used as the terminal reductant. Moderate to excellent enantiomeric excess was obtained with excellent functional group tolerance.
A method is presented to determine the enantiomeric excess (ee) of phosphoric acids 1, which are extensively used as resolving agents, by means of diastereomeric salt formation with chiral amines. The unexpected dynamic behaviour of these systems leads us to postulate a model, which we refer to as non-reciprocal behaviour.
Catalytic synthesis of nonracemic P-chiral phosphine derivatives remains a significant challenge. Here we report Cu-catalyzed enantioselective arylation of secondary phosphine oxides with diaryliodonium salts for the synthesis of tertiary phosphine oxides with high enantiomeric excess. The new process is demonstrated on a wide range of substrates and leads to products that are well-established ...
This report details the synthesis and characterization of the first chiral diNHC cyclophane ligand and its palladium allyl complex. The complex was tested for 1,4-conjugate addition of phenylboronic acid to 2-cyclohexen-1-one and provides R-3-phenylcyclohexanone in 50% enantiomeric excess.
Enantiomerically enriched hydroxy-substituted beta-amino esters have been synthesized through CAL-B-catalyzed enantioselective hydrolysis in organic media. Moderate to good enantiomeric excess values (ee > or = 52%) were obtained when the CAL-B-catalyzed reactions were performed in t-BuOMe, at 60 degrees C with 0.5 equiv. of added H(2)O as nucleophile.
A mild catalytic asymmetric direct fluoro-arylation of styrenes has been developed. The palladium-catalyzed three-component coupling of Selectfluor, a styrene and a boronic acid, provides chiral monofluorinated compounds in good yield and in high enantiomeric excess. A mechanism proceeding through a Pd(IV)-fluoride intermediate is proposed for the transformation and synthesis of an sp(3) C-F bond.
A series of fused tetracycles with a benzene or cyclohexadiene core (2a-h) is satisfactorily prepared by intramolecular [2 + 2 + 2] cycloadditions of triynic and enediynic macrocycles (1a-h) under RhCl(PPh3)3 catalysis; the enantioselective cycloaddition of macrocycles 1b and 1e and gives chiral tetracycles with moderate enantiomeric excess.
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