Home About us Contact
|
Home About us Contact | ||
|
|
||
Enantio
Kinds of Enantio Selected AbstractsEnantio- and Diastereomerically Pure Decalins by Deslongchamps-Type Annulation of Dienolates Containing a Chiral Lactone SubstituentEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2007Thomas Tricotet Abstract A conceptionally novel 1,3-asymmetric induction has been established. It controls the relative and absolute configuration of up to 5 stereocenters. They emerge from the anionic Diels,Alder reactions ("Deslongchamps annulations") between oxocyclohexenecarboxylates 25, 29 and dienolates 26, 30. The latter contain a ,-lactone. A Ph3Si,CH2 substituent therein controls the asymmetry of C,C bond formation with ds , 10:1. Strangely, the preferred sense of attack of the dienophile is contrasteric. Cycloadduct 31 was processed by an unprecedented fluoride-induced ambient-temperature tandem fragmentation. It turned the lactone moiety into an allyl group and the ,-oxo (trimethylsilyl)ethyl ester into a ketone. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Highly Enantio- and Diastereoselective One-Pot Reactions in Aqueous Media: Combined Asymmetric Rh-Catalyzed Conjugate Addition/Metal-Mediated AllylationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2006Sara Källström Abstract 1,3-Disubstituted, enantiopure cyclohexanols have been prepared in very high diastereoselectivities and good yields by a concise one-pot method combining the enantioselective rhodium-catalyzed conjugate addition of arylboronic acids with indium-mediated allylation into a highly efficient one-pot reaction in aqueous media. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Enantio- and Diastereoselective Mannich-Type Reactions of ,-Cyano Ketones with N -Boc Aldimines Catalyzed by Chiral Bifunctional UreaADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Ju Hee Lee Abstract The catalytic enantioselective electrophilic Mannich-type reaction promoted by chiral bifunctional organocatalysts is described. The treatment of ,-cyano ketones with N -Boc-aldimines under mild reaction conditions afforded the corresponding ,-amino-,-cyano ketones with excellent diastereoselectivities (up to syn/anti=100/0), and excellent enantioselectivities (up to 99% ee). [source] Highly Enantio- and Diastereoselective Inverse Electron Demand Hetero-Diels,Alder Reaction using 2-Alkenoylpyridine N -Oxides as Oxo -HeterodienesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Santiago Barroso Abstract A general catalytic inverse electron demand hetero-Diels Alder reaction for 2-alkenoylpyridine N -oxides is presented. 2-Alkenoylpyridine N -oxides react very efficiently with alkenes in the presence of bisoxazolidine-copper(II) [BOX-Cu(II)] complexes to give chiral dihydropyrans bearing a pyridine ring at the 6-position with very high yields and excellent diastereo- and enantioselectivity. These heterodienes exhibited higher reactivity and enantioselectivity than the corresponding non-oxidized 2-alkenoylpyridines. [source] Asymmetric Nazarov Reaction Catalyzed by Chiral Tris(oxazoline)/Copper(II),ANGEWANDTE CHEMIE, Issue 26 2010Peng Cao Dr. In Gegenwart eines dreizähnigen Liganden führte die Titelreaktion hoch effizient zu chiralen O-Heterohexahydroindenonen. Die Produkte wurden mit ausgezeichneten Ausbeuten, Enantio- und Diastereoselektivitäten erhalten. HFIP=Hexafluor-2-propanol, BArF= Tetrakis[3,5-bis(trifluormethyl)phenyl]borat. [source] Catalytic Enantio- and Diastereoselective Alkylations with Cyclic Sulfamidates,ANGEWANDTE CHEMIE, Issue 3 2010Thomas Erfolgreich selektiv: Die enantio- und diastereoselektive nucleophile Ringöffnung fünf- und sechsgliedriger cyclischer Sulfamidate unter asymmetrischer Phasentransferkatalyse wird beschrieben. Eine Vielzahl an Pränucleophilen konnte mit guten Ausbeuten und Enantioselektivitäten alkyliert werden. [source] Rhodium-Catalyzed Enantioselective and Diastereoselective Hydrogenation of ,-Ketoenamides: Efficient Access to anti 1,3-Amino Alcohols,ANGEWANDTE CHEMIE, Issue 33 2009Huiling Geng Nützliche chirale Bausteine werden mit ausgezeichneter Enantio- und Diastereoselektivität bei einer Tandemhydrierung von (Z)-,-Ketoenamiden gebildet, die wiederum durch direkte Kondensation von 1,3-Diketonen mit Acetamid erhalten werden (siehe Schema). Die chiralen Aminoalkoholprodukte können durch Hydrogenolyse mit Pd/C in nützliche ,-Arylisobutylamine überführt werden. R1=Aryl, Heteroaryl, Methyl; R2=Alkyl. [source] Enantio- and Diastereoselective Chemoenzymatic Synthesis of C2-Symmetric Biaryl-Containing DiolsCHEMCATCHEM, Issue 1 2010Edyta Burda Abstract An enantio- and diastereoselective synthesis of C2-symmetric diols bearing a biphenyl-framework has been developed by means of an enzymatic reduction of the corresponding diketones, which were prepared by a Suzuki coupling reaction. Furthermore, a chemoenzymatic one-pot synthesis of a C2-symmetric diol in aqueous media has been realized through combination of the Suzuki coupling reaction and enzymatic reduction. Chiral stereoisomers of the biaryl-containing diols are prepared with diastereomeric ratios in excess of 25:1 and enantiomeric excesses of greater than 99,%. [source] ChemInform Abstract: One-Pot Catalytic Enantio- and Diastereoselective Syntheses of anti-, syn-cis-Disubstituted, and syn-Vinyl Cyclopropyl Alcohols.CHEMINFORM, Issue 28 2010Hun Young Kim Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: One-Pot Catalytic Enantio- and Diastereoselective Syntheses of anti-, syn-cis-Disubstituted, and syn-Vinyl Cyclopropyl Alcohols.CHEMINFORM, Issue 28 2010Hun Young Kim Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Enantio- and Diastereoselective Chemoenzymatic Synthesis of C2-Symmetric Biaryl-Containing Diols.CHEMINFORM, Issue 21 2010Edyta Burda Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Highly Enantio- and Diastereoselective Michael Addition of Cyclohexanone to Nitroolefins Catalyzed by a Chiral Glucose-Based Bifunctional Secondary Amine,Thiourea Catalyst.CHEMINFORM, Issue 51 2009Aidang Lu 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: A Sequential O-Nitrosoaldol and Grignard Addition Process: An Enantio- and Diastereoselective Entry to Chiral 1,2-Diols.CHEMINFORM, Issue 35 2009Peng Jiao 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Highly Enantio- and Diastereoselective Organocatalytic Cascade Aza-Michael,Michael Reactions: A Direct Method for the Synthesis of Trisubstituted Chiral Pyrrolidines.CHEMINFORM, Issue 14 2009Hao Li 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Enantio- and Diastereoselective Synthesis of syn-,-Hydroxyallylsilanes via a Chiral (Z)-,-Silylallylboronate.CHEMINFORM, Issue 13 2008Ricardo Lira 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Mixtures of Chiral Phosphorous Acid Diesters and Achiral P Ligands in the Enantio- and Diastereoselective Hydrogenation of Ketimines.CHEMINFORM, Issue 40 2007Manfred T. Reetz 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] Catalytic Enantio- and Diastereoselective Formation of ,-Sultones: Ring-Strained Precursors for Enantioenriched ,-Hydroxysulfonyl Derivatives.CHEMINFORM, Issue 29 2007Florian M. Koch 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] A Highly Enantio- and Diastereoselective 1,3-Dimethylallylation of Aldehydes.CHEMINFORM, Issue 10 2007Yu Yuan 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] Enantio- and Diastereoselective Synthesis of Tetrahydrofurochromenes by Sequential Asymmetric Homoaldol Reaction and a Mukaiyama-Type Tetrahydrofuran Cyclization.CHEMINFORM, Issue 5 2007Astrid Bruens 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] Enantio- and Diastereoselective Hydrogenation via Dynamic Kinetic Resolution by a Cationic Iridium Complex in the Synthesis of ,-Hydroxy-,-amino Acid Esters.CHEMINFORM, Issue 3 2007Kazuishi Makino 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] High Enantio- and Diastereoselective Induction of BINOL- and TADDOL-Modified Vinyloxy Ethoxides in C,C Coupling Reactions with Aldehydes.CHEMINFORM, Issue 16 2006Peter Maier 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] Enantio- and Diastereoselective Synthesis of Highly Substituted Acylcyclopropanes from Homoaldol Products by Stereospecific Homoallylic Cyclization.CHEMINFORM, Issue 7 2006Rainer Kalkofen Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access the actual ChemInform Abstract, please click on HTML or PDF. [source] Highly Enantio- and Diastereoselective One-Pot Synthesis of Acyclic Epoxy Alcohols and Allylic Epoxy Alcohols.CHEMINFORM, Issue 7 2006Ann Rowley Kelly Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access the actual ChemInform Abstract, please click on HTML or PDF. [source] Enantio- and Diastereoselective Catalytic Mannich-Type Reaction of a Glycine Schiff Base Using a Chiral Two-Center Phase-Transfer Catalyst.CHEMINFORM, Issue 45 2005Akihiro Okada Abstract For Abstract see ChemInform Abstract in Full Text. [source] A Highly Enantio- and Diastereoselective Catalytic Intramolecular Stetter Reaction.CHEMINFORM, Issue 38 2005Javier Read de Alaniz Abstract For Abstract see ChemInform Abstract in Full Text. [source] Catalytic Enantio- and Diastereoselective Aldol Reactions of Glycine-Derived Silicon Enolate with Aldehydes: An Efficient Approach to the Asymmetric Synthesis of anti-,-Hydroxy-,-Amino Acid Derivatives.CHEMINFORM, Issue 47 2004Jun Kobayashi No abstract is available for this article. [source] Highly Enantio- and Diastereoselective Organocatalytic Asymmetric Domino Michael,Aldol Reaction of ,-Ketoesters and ,,,-Unsaturated Ketones.CHEMINFORM, Issue 26 2004Nis Halland Abstract For Abstract see ChemInform Abstract in Full Text. [source] Enantioselective analysis of pheniramine in urine by charged CD-mediated CZE provided with a fiber-based DAD and an on-line sample pretreatment by capillary ITPELECTROPHORESIS, Issue 15 2007Jozef Marák Abstract Application potentialities of CZE on-line coupled with capillary ITP and DAD to the identification and determination of trace concentration levels (,g/L) of pheniramine (PHM) enantiomers and their metabolites present in complex ionic matrices of biological origin (urine) are shown. An enhanced (enantio)selectivity of the CZE separation system obtained by the addition of carboxyethyl-,-CD (CE-,-CD) to the carrier electrolyte provided CZE conditions for a reliable identification of similar/identical DAD spectra of structurally related compounds (PHM enantiomers and their metabolites) in clinical urine samples differing in qualitative and quantitative composition of sample matrix constituents. A high sample loadability (a 30,,L sample injection volume), partial sample clean-up (removing macroconstituents from the sample), and preconcentration of the analytes in ITP stage resulted in the decrease of concentration LOD for PHM enantiomers in urine to 5.2 and 6.8,,g/L (2.2×10,8 and 2.8×10,8,mol/L), without using any sample pretreatment technique. The background correction and smoothing procedure applied to the raw DAD spectra provided analytically relevant DAD spectra of PHM enantiomers and their metabolites also when they were present in urine sample (30,,L injection volumes of ten-times diluted urine sample) at a 9×10,8,mol/L concentration. DAD spectra of PHM enantiomers present in urine samples matched their reference spectra with reasonable certainties. DAD spectra of PHM metabolites were compared with the reference spectra of PHM enantiomers and a good match was found which indicates the similarities in the structures of enantiomers and their metabolites detected in the urine samples. This fact allows performing the quantitative analyses of PHM metabolites in the urine samples by applying the calibration parameters of PHM enantiomers also for PHM metabolites and the results show the possibilities of using the ITP,CZE,DAD combination for the direct analysis of PHM enantiomers and/or their metabolites in urine without any sample pretreatment. ITP,CZE,DAD method with oppositely charged selector is suggested to use in clinical research as it provides favorable performance parameters including sensitivity, linearity, precision, recovery, and robustness with minimal demands on sample preparation. [source] Enantioselective CpRu-Catalyzed Carroll Rearrangement , Ligand and Metal Source ImportanceEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2008David Linder Abstract The addition of unstabilized carbonyl nucleophiles to unsymmetrical allyl-metal fragments still represents a challenge to generate stereogenic centers enantio- and regioselectively. In this context, the decarboxylative Carroll rearrangement of allyl ,-keto esters is particularly interesting, since chiral ,,,-unsaturated ketones are obtained. Herein, we show that CpRu half-sandwich complexes can, with selected enantiopure pyridine-monooxazoline ligands, catalyze this transformation and afford complete conversions along with good levels of regioselectivity and enantioselectivity. Even more challenging (electron-poor) substrates react (up to 86,% ee, branched/linear ratio , 97:03). In addition, the use of an air-stable metal precursor, namely [CpRu(,6 -naphthalene)][PF6], allows the reaction to be carried out reproducibly evenin non-anhydrous THF with a catalyst loading as low as2 mol-%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Combination of Enantioselective Metal Catalysis and Organocatalysis: Enantioselective Sequential Hydroformylation/ Aldol ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2010Serghei Chercheja Abstract This work reports the possibility of controlling the sense of enantio- and diastereoinductions in the sequential hydroformylation and aldol reactions via the judicious combination of a chiral metal catalyst with a chiral organocatalyst. The diastereoselectivity of the reaction between styrene, syngas and acetone can be increased by using a matched pair of catalysts, [rhodium/(2S,4S)-Chiraphite]/(S)-organocatalyst and decreased, but not inverted, by using a mismatched pair of catalysts, [rhodium/(2R,4R)-Chiraphite]/(S)-organocatalyst. [source] | |||||||||||||||||||||||||