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Catalytic Asymmetric Dihydroxylation (catalytic + asymmetric_dihydroxylation)
Selected AbstractsCatalytic Asymmetric Dihydroxylation of Olefins with Recyclable Osmate-Exchanged Chloroapatite Catalyst.CHEMINFORM, Issue 28 2007Sanjay K. Dehury Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Sharpless Asymmetric Dihydroxylation of Olefins in WaterSurfactant Media with Recycling of the Catalytic System by Membrane NanofiltrationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2008Abstract This paper presents a new and more sustainable alternative approach for the Sharpless catalytic asymmetric dihydroxylation (AD) of olefins using a water/surfactant system as reaction media. The AD reaction was performed using several cationic and anionic surfactants allowing yields and enantiomeric excesses higher or comparable with the conventional systems (using organic mixtures). The use of this water/surfactant medium offers the additional advantage of performing the reactions without the need of a slow addition of olefins. Asymmetric dihydroxylation of 1-hexene in a 1.5,mM sodium cholate aqueous solution, using N -methylmorpholine N -oxide (NMO) as co-oxidant was selected as model system to evaluate the feasibility of recycling the Sharpless catalytic system by nanofiltration. The reaction media was processed by nanofiltration, the product was isolated in the permeate, whereas the catalytic system and surfactant were retained by the membrane and recycled through six successive reactions, improving the catalyst turn-over number. The experimental results were compared with the ones calculated on the basis of mass balances, membrane rejections to product and reaction yields. [source] Enantioselective separation of chiral vicinal diols in capillary electrophoresis using a mono-6A -aminoethylamino-,-cyclodextrin as a chiral selectorJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2009Peng Liu Abstract This paper describes an improved access to mono-6A -aminoethylamino-,-CD (,-CDen), a very efficient cationic chiral selector for CZE in the separation of eight chiral aromatic vicinal diols. The ,-CDen concentration has a strong influence on the efficiency of enantioseparation. The effects of the pH and concentration of the BGE, the capillary temperature, and the applied voltage on the resolution and separation selectivity have been studied. Excellent chiral resolution was achieved under the optimal conditions of ,-CDen 10 mM, pH 10, 200 mM borate buffer at 15 kV and 20°C within 20 min. Moreover, the developed method was successfully applied to the determination of the enantiomeric purity of the catalytic asymmetric dihydroxylation (AD) reaction products. [source] Enantioselective Dihydroxylation of Alkenes Catalyzed by a PEG-Bound Bi-Cinchona Alkaloid LigandCHINESE JOURNAL OF CHEMISTRY, Issue 1 2005Xi-Wen Yang Abstract The recyclable PEG-bound bi-cinchona alkaloid ligand has been successfully applied to the homogeneous catalytic asymmetric dihydroxylation of various alkenes; good yields and excellent enantioselectivities were obtained. The ligand could be easily recovered and reused for 10 times without any apparent loss of its catalyst efficiency. [source] Synthesis of chiral vicinal diols and analysis of them by capillary zone electrophoresisCHIRALITY, Issue 2 2008Peng Liu Abstract This paper describes an improved access to 1,4-bis (9- O -quininyl) phthalazine [(QN)2PHAL], a very useful chiral ligand for catalytic asymmetric dihydroxylation (AD), by using CaH2 as acid-binding reagent in a high yield under mild conditions. The application of (QN)2PHAL to the AD reactions of eight olefins exhibited excellent enantioselectivity and activity with corresponding chiral vicinal diols. Furthermore, a capillary zone electrophoresis method was developed to separate the aforementioned chiral vicinal diols by using of neutral ,-cyclodextrin (,-CD) as chiral selector and borate as running buffer. High resolution was achieved under the optimal conditions of ,-CD 2.2% (w/v), pH 10, 200 mM borate buffer at 15 kV, and 20°C within 15 min. The relative standard deviations of the corrected peak areas and migration time were less than 3.9% and 1.3%, respectively. In addition, the developed method was successfully applied to the determination of the purity and the enantiomeric excesses value (%ee) of the AD reaction products. Chirality, 2008. © 2007 Wiley-Liss, Inc. [source] | ||||||||||