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Kinetic Resolution (kinetic + resolution)
Kinds of Kinetic Resolution Selected AbstractsKinetic Resolution of Racemic Secondary Alcohols Mediated by N -Methylimidazole in the Presence of Optically Active Acyl ChloridesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2010Loïc Leclercq Abstract N -Methylimidazole was used to promote the acylation of secondary racemic alcohols and to carry out their kinetic resolution through intermediate chiral acyl imidazolium chlorides. The kinetic resolution could be turned into a catalytic process in the presence of a catalytic amount of N -methylimidazole. [source] Dynamic Enzymatic Kinetic Resolution of Methyl 2,3-Dihydro-1H -indene-1-carboxylateEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2009Jörg Pietruszka Abstract A new reaction setup for kinetic enzymatic resolution was established and is demonstrated for the case of the hydrolase-catalysed conversion of methyl 2,3-dihydro-1H -indene-1-carboxylate (1) in conjunction with a base-catalysed racemisation. The system allows controlled racemisation, resulting in efficient dynamic kinetic resolution (DKR) of the title compound. Short reaction times and high enantioselectivities were obtained with CAL-B and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene). Compound (R)- 1 (ee 95,%) served as a starting material in a domino reaction that led to the biaryl indanyl ketone (R)- 8, a lead compound for novel inhibitors of peptidyl-prolyl- cis/trans -isomerases, in 94,% ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Asymmetric Homoaldol Reactions with Cyclohex-2-enyl N,N -Diisopropylcarbamate: Kinetic Resolution, Elucidation of the Stereochemical Course and Applications in the Synthesis of Hexahydroisobenzofuran-4-(1H)-onesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2007Jochen Becker Abstract Enantio-enriched cyclohex-2-enyl N,N -diisopropylcarbamate (5) is stereospecifically deprotonated by sec -butyllithium/(,)-sparteine (9) to form the configurationally stable lithium complex 7·9. A kinetic resolution of rac - 5 by n -butyllithium/(,)-sparteine (9) yielded (R)- 5 with up to 99,% ee. Electrophilic substitution with tin electrophiles proceeds in a anti -SE, fashion as shown by chemical correlations. The synthesized allylstannanes 10 undergo a highly stereospecific TiCl4 -mediated homoaldol reaction with various aldehydes, yielding syn -configured homoaldol products 12. These were transferred into all - cis -configured hexahydroisobenzofuran-4(1H)-ones 22 by BF3·OEt2 -mediated reactions with aldehydes. The configurations of several products were determined by X-ray structure analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis of An Enantioenriched C2 -Symmetric Molecule by a Chiral-Base-Mediated Kinetic Resolution of an (Arene)tricarbonylchromium(0) ComplexEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2006M. Paola Castaldi Abstract Trimethylsilyl substituents have been used to control the conformational preferences of a 1,2-disubstituted (arene)tricarbonylchromium(0) complex. The kinetic resolution of the mono-methyl derivative (±)- 11 using a chiral base/iodomethane quench sequence led to the synthesis of the enantioenriched C2 -symmetric bis-ether (+)- 13. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Lactone Kinetic Resolution by Acylation , Application to the Enantioselective Synthesis of Estrane DerivativesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2005Serge Wilmouth Abstract The acylation of an excess of racemic spirolactone 1 (6,9-divinyl-1-oxaspiro[4.4]nonan-2-one) enolate by protected methyl (S)-lactate or (,)-bornyl carbonate occurs with a kinetic resolution. The resulting lactones were alkylated with 1-iodobenzocyclobutenes to afford compounds that serve as precursors to nonracemic steroids such as 11,-alkyloxycarbonyl-11,,13,-(,-carbolactone)-17,-vinylgonatri-1,3,5(10)-enes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Cu(II)-Azabis(oxazoline)-Complexes Immobilized on Superparamagnetic Magnetite@Silica-Nanoparticles: A Highly Selective and Recyclable Catalyst for the Kinetic Resolution of 1,2-DiolsADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Alexander Schätz Abstract Two different types of azide functionalized magnetite@silica nanoparticles are synthesized, which are ideally suited as inexpensive supports for catalysts and reagents as demonstrated with the grafting of copper(II)-azabis(oxazoline) complexes via a copper(I) catalyzed azide/alkyne cycloaddition (CuAAC) reaction. The potential of the immobilized complexes as catalysts is tested in the desymmetrization of racemic 1,2-diols through asymmetric benzoylation. Compared to azabis(oxazolines) "clicked" to common polymeric supports such as MeOPEG or Merrifield resin, Fe3O4@SiO2 proves to be superior with respect to activity and selectivity, as exemplified by employing the catalysts in up to five runs with consistent high activity and selectivity. Recycling of the catalysts is achieved quantitatively by magnetic decantation. [source] Enantioselective Synthesis of , -Blockers via Hydrolytic Kinetic Resolution of Terminal Oxiranes by Using Bimetallic Chiral {{2,2,-[Cyclohexane-1,2-diylbis(nitrilomethylidyne)]bis[phenolato]}(2,)}cobalt ([Co(salen)])-Type ComplexesHELVETICA CHIMICA ACTA, Issue 2 2008Rahul Abstract The synthesis of chirally pure , -blockers was successfully achieved via hydrolytic kinetic resolution of butyl (±)-4-(oxiran-2-ylmethoxy)benzeneacetate ((±)- 1) and (±)-4-(oxiran-2-ylmethoxy)benzeneacetonitrile ((±)- 2) in the presence of bimetallic chiral [Co(salen)]-type complexes. The newly synthesized bimetallic chiral [Co(salen)]-type complexes exhibited excellent enantioselectivities of up to >98% ee in good yields (Tables,1,3). [source] Efficient Tandem Biocatalytic Process for the Kinetic Resolution of Aromatic ,-Amino AcidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Bian Wu Abstract We describe a simple and efficient enzymatic tandem reaction for the preparation of enantiomerically pure , -phenylalanine and its analogues from the corresponding racemates. In this process, phenylalanine aminomutase (PAM) catalyzes the stereoselective isomerization of (R)- , -phenylalanines to (S)- , -phenylalanines, which are in situ transformed to cinnamic acids by phenylalanine ammonia lyase (PAL). Preparative scale conversions are done with a mutated PAM with enhanced catalytic activity. [source] Enantioselective Synthesis of Chiral ,-Aryloxy Alcohols by Ruthenium-Catalyzed Ketone Hydrogenation via Dynamic Kinetic Resolution (DKR)ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Wen-Ju Bai Abstract A highly efficient enantioselective synthesis of chiral ,-aryloxy alcohols by the {RuCl2[(S)-SDP][(R,R)-DPEN]} [(Sa,R,R)- 1a; SDP=7,7,-bis(diarylphosphino)-1,1,-spirobiindane; DPEN=trans -1,2-diphenylethylenediamine] complex-catalyzed asymmetric hydrogenation of racemic ,-aryloxydialkyl ketones via dynamic kinetic resolution (DKR) has been developed. Enantioselectivities of up to 99% ee with good to high cis/anti -selectivities (up to>99:1) were achieved. [source] Cooperative Activation in the Hydrolytic Kinetic Resolution of Epoxides by a Bis-Cobalt(III)salen-Calix[4]arene HybridADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Sander Abstract A chiral, bimetallic cobalt(III)salen-calix[4]arene hybrid structure was prepared and tested in the hydrolytic kinetic resolution (HKR) of racemic epoxides. Kinetic studies have revealed that the two catalytic units on the upper rim of the calixarene scaffold are able to activate the reactants in a cooperative and primarily intramolecular mode. High enantioselective behaviour was observed and besides, a higher stability was found for the bimetallic catalyst as compared to a monometallic reference complex. [source] Homobenzotetramisole-Catalyzed Kinetic Resolution of ,-Aryl-, ,-Aryloxy-, and ,-Arylthioalkanoic AcidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Xing Yang Abstract Effective kinetic resolutions of ,-aryl-, ,-aryloxy-, and ,-arylthioalkanoic acids have been achieved via in situ generation of their symmetrical anhydrides and enantioselective alcoholysis in the presence of homobenzotetramisole (HBTM) 3. [source] Effects of Methyl Substituents on the Activity and Enantioselectivity of Homobenzotetramisole-Based Catalysts in the Kinetic Resolution of AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Yuhua Zhang Abstract Substitution of the tetrahydropyrimidine ring in the enantioselective acyl transfer catalyst homobenzotetramisole (HBTM) 6 with methyl groups exerts a dramatic influence on its performance in the kinetic resolution of secondary alcohols. The syn- 3-methyl analogue of HBTM (9a) has proved to be superior to the parent compound in terms of catalytic activity, enantioselectivity, and synthetic accessibility. [source] Kinetic Resolution of P-Chirogenic Compounds by Palladium-Catalyzed Alcoholysis of Vinyl EthersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Hisashi Itoh Abstract The palladium-catalyzed asymmetric alcoholysis of vinyl ethers of P-chirogenic compounds has been achieved. The kinetic resolution of aryl tert -butyl(2-vinyloxyaryl)phosphinates was catalyzed by palladium/chiral diamine complexes with high selectivities (krel: 12,196). [source] Enantioselective Synthesis of Chiral ,-Aryloxy Alcohols by Asymmetric Hydrogenation of ,-Aryloxy Aldehydes via Dynamic Kinetic ResolutionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Zhang-Tao Zhou Abstract A catalytic enantioselective hydrogenation of racemic ,-aryloxy aldehydes via dynamic kinetic resolution has been developed by using (diamine)(spirodiphosphine)ruthenium(II) chloride [RuCl2(SDPs)(diamine)] catalysts. Employing this new reaction system a variety of optically active ,-aryloxy primary alcohols were synthesized in high yields and moderate to good enantioselectivities. [source] Stereoselective Synthesis of Three Isomers of tert -Butyl 5-Hydroxy-4-methyl-3-oxohexanoate through Alcohol Dehydrogenase-Catalyzed Dynamic Kinetic ResolutionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Steffen Lüdeke Abstract Regioselective reduction of the 5-keto group of tert -butyl 4-methyl-3,5-dioxohexanoate (1) leads to a stereodiad of tert -butyl 5-hydroxy-4-methyl-3-oxohexanoate (2). Alcohol dehydrogenases from Lactobacillus brevis (LBADH), Rhodococcus sp. (RS 1-ADH) and Saccharomyces cerevisiae (YGL157w) reduce 1 under dynamic kinetic resolution conditions, thereby establishing two chiral carbons with a single reduction step. While it had been shown previously that LBADH reduction of 1 stereoselectively leads to syn -(4S,5R)- 2, alcohol dehydrogenase-mediated dynamic kinetic resolution now allows easy access to syn -(4R,5S)- 2 (RS 1-ADH; 97.6% ee, syn:anti=92:8, 66% conversion, 37% isolated yield) and anti -(4S,5S)- 2 (YGL157w; 90% ee, anti:syn=93:7, 64% conversion, 42% isolated yield), as well. Thus three out of four possible stereoisomers were formed selectively upon reduction of 1. [source] One-Pot, Regioselective Synthesis of Substituted Arylglycines for Kinetic Resolution by Penicillin G AcylaseADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2008Peter Grundmann Abstract Amido-alkylation of electron-rich arenes with phenylacetamide and glyoxylic acid offers an inexpensive route to a large variety of N -phenylacetylated arylglycines that are suited for immediate enzymatic resolution by penicillin G acylase. When performed under mild conditions at 5,°C in acetic acid/HCl, this simple one-pot operation resulted in the formation of single regioisomers only (,98%). Subsequent kinetic resolution of the amino acid derivatives by penicillin G acylase at pH,8.0 occurred generally with E values>100 and thus furnished free (S)-configurated arylglycines with high enantiomeric purity. The corresponding enantiopure (R)-substrates, easily separable by a phase-selective extraction process, provided the corresponding (R)-enantiomers upon conventional hydrolysis. This one-pot, two-step procedure for arylglycine synthesis, resolution and work-up requires a minimum of equipment and grants rapid access to both enantiopure (S)- and (R)-antipodes of non-natural ,-amino acids in small- to large-scale quantities. [source] Enhanced Cooperativity in Hydrolytic Kinetic Resolution of Epoxides using Poly(styrene) Resin-Supported Dendronized Co-(Salen) CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2008Poorva Goyal Abstract Excellent enantioselectivities and isolated yields have been achieved for the hydrolytic kinetic resolution of epoxides using a resin-supported dendronized R,R-(salen)Co catalyst with catalyst loadings as low as 0.04 mol%, the lowest metal loadings of any heterogeneous resin-supported (salen)Co catalyst reported to date. In addition, the supported catalysts can be recycled and reused with comparable enantioselectivities. It is hypothesized that the high catalytic activity can be attributed to the flexible linker and the dendronized framework supporting the (salen)Co moieties on the resin thereby promoting cooperativity between two metal centers. This work opens up new opportunities for the design of highly active resin-supported catalysts that catalyze transformations through a bimetallic pathway. [source] Cooperative Catalysis in the Hydrolytic Kinetic Resolution of Epoxides by Chiral [(salen)Co(III)] Complexes Immobilized on Gold ColloidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2008Thomas Belser Abstract Chiral salen ligands were incorporated into self-assembled thiolate monolayers (SAMs) on gold colloids. Treatment of the immobilized ligand with Co(OAc)2,4,H2O yielded the corresponding [(salen)Co(II)] complex, and aerobic oxidation in the presence of triflic acid afforded the catalytically active [(salen)Co(III)] complex. Functionalized gold colloids with a diameter of 3.4,nm, coated with a mixed monolayer of n -octanethiolates and thiolates with chiral [(salen)Co(III)] end groups were studied as catalysts in the hydrolytic kinetic resolution (HKR) of hexene-1-oxide. Extremely high selectivitiy and significant rate acceleration relative to homogeneous monomeric catalysts were observed. Recovery of the immobilized catalyst was accomplished by simple filtration, and catalyst reoxidation and repeated recycling (seven times) was possible with no loss of reactivity or enantioselectivity. [source] Kinetic Resolution of 1-Biaryl- and 1-(Pyridylphenyl)alkan-1-ols Catalysed by the Lipase B from Candida antarcticaADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2005Robert Kourist Abstract Lipase B from Candida antarctica (CAL-B) catalyses the highly enantioselective (E>200) transesterification of some 1-biaryl-2-yl-, -3-yl-, and -4-ylethanols and -propan-1-ols, as well as 1-(o -, m -, and p -pyridylphenyl)ethanols, 6, with vinyl acetate, Kazlauskas' rule being obeyed in all cases. meta and para -Substituted substrates were transformed within several hours (conversion degree ranging from 23,50%), reaction rates for propan-1-ol derivatives being slower than those for ethanol derivatives. Transesterifications of ortho -substituted alcohols took several days and were accompanied by a chemoenzymatic side reaction: the formation of another acetate derived from the hemiacetal between 6 and acetaldehyde coming from vinyl acetate. This side reaction was suppressed in the presence of isopropenyl acetate as acyl donor, conversion degrees for transesterification ranging from 20,40% after ten days (E>200). The usefulness of (R)- 6p as ligand in the asymmetric addition of diethylzinc to benzaldehyde was also demonstrated. [source] Kinetic Resolution of Quaternary and Tertiary ,-Hydroxy Esters,ANGEWANDTE CHEMIE, Issue 44 2009Derek Einfach selektiv: In Gegenwart von (1S,2R)- N -methylephedrin gelingt die Racematspaltung von tertiären und sekundären Alkoholen, die bei Aldoladditionen mit Ketonen und Aldehyden entstehen (siehe Beispiel). Die Methode ist einfach ausführbar und leicht auf einen größeren Maßstab zu übertragen, und sie liefert tertiäre und sekundäre Alkohole mit hohen Enantiomerenverhältnissen. [source] ChemInform Abstract: Efficient Kinetic Resolution of Racemic 3-Nitro-2H-chromene Derivatives Catalyzed by Takemoto,s Organocatalyst.CHEMINFORM, Issue 38 2010Jian-Wu Xie Abstract Kinetic resolution of nitrochromene derivatives (I) in the presence of benzylidene imine (II) proceeds smoothly in the presence of Takemoto,s bifunctional thiourea catalyst to give a mixture of enantioenriched nitrochromenes ((R)-I) and cycloadduct (III). [source] ChemInform Abstract: Kinetic Resolution of trans-Cycloalkane-1,2-diols via Steglich Esterification.CHEMINFORM, Issue 32 2010Radim Hrdina Abstract A chiral tetrapeptide is successfully applied as catalyst for the kinetic resolution of diols (I) by enantioselective Steglich esterification. [source] ChemInform Abstract: Highly Efficient Dynamic Kinetic Resolution of Secondary Aromatic Alcohols with Low-Cost and Easily Available Acid Resins as Racemization Catalysts.CHEMINFORM, Issue 32 2010Yongmei Cheng Abstract A combination of Novozym435 with an acidic polystyrene resin CD8604 affords a new and efficient dynamic kinetic resolution of acetophenones to give the corresponding benzylic alcohols with good to excellent enantioselectivities. [source] ChemInform Abstract: Dynamic Kinetic Resolution: Asymmetric Transfer Hydrogenation of ,-Alkyl-Substituted ,-Ketoamides.CHEMINFORM, Issue 26 2010John Limanto 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: An Effective Kinetic Resolution of Racemic Secondary Benzylic Alcohols Using 3-Pyridinecarboxylic Anhydride and a Chiral Acyl-Transfer Catalyst in the Absence of Tertiary Amine.CHEMINFORM, Issue 21 2010Kenya Nakata 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: Kinetic Resolution of ,-Chromenyl-,-Hydroxy Esters for Asymmetric Preparation of Flavene Derivatives.CHEMINFORM, Issue 39 2009Dajung Kim 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: Preparation of Novel Axially Chiral NHC,Pd(II) Complexes and Their Application in Oxidative Kinetic Resolution of Secondary Alcohols.CHEMINFORM, Issue 35 2009Shi-Jia Liu 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: Kinetic Resolution of Allylic Esters (I) in Palladium-Catalyzed Asymmetric Allylic Alkylations Using C,N Bond Axially Chiral Aminophosphine Ligands.CHEMINFORM, Issue 24 2009Takashi Mino 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: Kinetic Resolution of 1,2-Diols Using Nitrogen-Tethered Bisimidazoline-Copper(I) Catalyzed Benzoylation.CHEMINFORM, Issue 18 2009Takayoshi Arai 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: Kinetic Resolution of Cyanohydrins via Enantioselective Acylation Catalyzed by Lipase PS-30.CHEMINFORM, Issue 6 2009Qing Xu 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] | ||||||||||||||||||||||||||||