Home About us Contact
|
Home About us Contact | ||
|
|
||
Michael Addition (michael + addition)
Kinds of Michael Addition Terms modified by Michael Addition Selected AbstractsSynthesis of Binaphthyl Sulfonimides and Their Application in the Enantioselective Michael Addition of Ketones to NitroalkenesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2010Shurong Ban Abstract Novel types of L -proline-based binaphthyl sulfonimides and sulfonamides were found to be efficient organocatalysts for the asymmetric Michael addition of ketones to nitroalkenes to provide optically active ,-nitroketone derivatives of synthetic and biological importance. After the fine optimization of solvents, temperature, and additive, good to excellent enantioselectivities and diastereoselectivities (71,96,%,ee, up to >99:1,dr) can be achieved. [source] Enantioselective Michael Addition of Aromatic Ketones to Nitroolefins Catalyzed by Bifunctional Thioureas and Mechanistic InsightEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2010Bai-Lin Li Abstract A highly enantioselective Michael reaction of aromatic ketones with nitroolefins was accomplished in the presence of a chiral bifunctional primary amine,thiourea catalyst and 4-nitrobenzoic acid as the co-catalyst; the corresponding adducts were obtained in excellent enantioselectivities (up to 99,%,ee) and yields (up to 98,%). The catalytic mechanism of the Michael reaction was confirmed through the ESI-MS detection of proposed reaction intermediates and the 1H NMR detection of hydrogen bonding between thiourea and the nitroolefins. DFT calculations showed that chiral moieties of the thiourea impacted the yields and enantioselectivities of the adducts remarkably, which corresponds to the observed experimental results. [source] Organocatalytic Enantioselective Michael Addition of 4-Hydroxycoumarin to ,,,-Unsaturated Ketones: A Simple Synthesis of WarfarinEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 30 2009Zhenhua Dong Abstract A type of C2 -symmetric secondary amine amide catalysts were developed for the asymmetric Michael addition of 4-hydroxycoumarin to ,,,-unsaturated ketones. A series of important biologically and pharmaceutically active compounds were obtained in excellent yields (up to 99,%) with high enantioselectivities (up to 89,%,ee) under mild conditions. In addition, enantiopure product could be obtained by a single recrystallization. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] 2-[(Imidazolylthio)methyl]pyrrolidine as a Trifunctional Organocatalyst for the Highly Asymmetric Michael Addition of Ketones to NitroolefinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2008Dan-Qian Xu Abstract The direct asymmetric Michael addition of ketones to nitroolefins catalyzed by 2-[(imidazol-2-ylthio)methyl]pyrrolidine, constructed from natural L -proline and imidazolylthio platforms, with salicylic acid as a co-catalyst has been developed to give the products in high yields (up to 95,%) and with excellent enantioselectivities (up to 99,% ee). The highly efficient catalytic performance may be attributed to the dual activation of the Michael substrates by the trifunctional organocatalysts and the co-catalyst salicylic acid, leading to the formation of a stable transition state complex through the synergic effect of hydrogen-bonding and electrostatic interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] A Versatile Solvent-Free "One-Pot" Route to Polymer Nanocomposites and the in situ Formation of Calcium Phosphate/Layered Silicate Hybrid NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Hans Weickmann Abstract Poly(methyl methacrylate) (PMMA), polystyrene (PS), and polyurethane (PU) nanocomposites containing well-dispersed calcium phosphate/layered silicate hybrid nanoparticles were prepared in a versatile solvent-free "one-pot" process without requiring separate steps, such as organophilic modification, purification, drying, dispersing, and compounding, typical for many conventional organoclay nanocomposites. In this "one-pot" process, alkyl ammonium phosphates were added as swelling agents to a suspension of calcium/layered silicate in styrene, methyl methacrylate, or polyols prior to polymerization. Alkyl ammonium phosphates were prepared in situ by reacting phosphoric acid with an equivalent amount of alkyl amines such as stearyl amine (SA) or the corresponding ester- and methacrylate-functionalized tertiary alkyl amines, obtained via Michael Addition of SA with methyl acrylate or ethylene 2-methacryloxyethyl acrylate. Upon contact with the calcium bentonite suspension, the cation exchange of Ca2+ in the silicate interlayers for alkyl ammonium cations rendered the bentonite organophilic and enabled effective swelling in the monomer accompanied by intercalation and in situ precipitation of calcium phosphates. According to energy dispersive X-ray analysis, the calcium phosphate precipitated exclusively onto the surfaces of the bentonite nanoplatelets, thus forming easy-to-disperse calcium phosphate/layered silicate hybrid nanoparticles. Incorporation of 5,15,wt% of such hybrid nanoparticles into PMMA, PS, and PU afforded improved stiffness/toughness balances of the polymer nanocomposites. Functionalized alkyl ammonium phosphate addition enabled polymer attachment to the nanoparticle surfaces. Transmission electron microscopy (TEM) analyses of PU and PU-foam nanocomposites, prepared by dispersing hybrid nanoparticles in the polyols prior to isocyanate cure, revealed the formation of fully exfoliated hybrid nanoparticles. [source] A New Autocatalytic Thioacetate-Enal Addition Reaction: A Michael Addition or Not?ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Gennadiy Ilyashenko Abstract Rather than proceeding through a Michael-type or 1,4-addition, thioacetic acid adds across unsaturated aldehydes in an autocatalytic manner and involving a double exotherm, as demonstrated by both adiabatic and reaction calorimetry. NMR studies show that an intermediate acylthio-hemiacetal is involved and that the product continues to react competitively with thioacetic acid. [source] Highly Enantioselective Michael Addition of Cyclic 1,3-Dicarbonyl Compounds to ,,,-Unsaturated ,-Keto EstersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Xing-Kuan Chen Abstract A highly enantioselective Michael addition of cyclic 1,3-dicarbonyl compounds to ,,,-unsaturated ,-keto esters catalyzed by amino acid-derived thiourea-tertiary-amine catalysts is presented. Using 5,mol% of a novel tyrosine-derived thiourea catalyst, a series of chiral coumarin derivatives were obtained in excellent yields (up to 99%) and with up to 96% ee under very mild conditions within a short reaction time. [source] Asymmetric Synthesis of 2,3,4-Trisubstituted Functionalised Tetrahydrofurans via an Organocatalytic Michael Addition as Key StepADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010Dieter Enders Abstract The organocatalytic Michael addition of various aldehydes to (2E,4E)-ethyl 5-nitropenta-2,4-dienoate has been achieved under the catalysis of diphenylprolinol trimethylsilyl ether furnishing the products in good to excellent yields (61,94%) and high stereoselectivities (dr up to >98:2, ee=97 to >99%). Starting from these Michael adducts, 2,3,4-trisubstituted functionalized tetrahydrofurans are available in two steps by reduction of the aldehyde followed by an intramolecular oxa-Michael addition in good yields (54,76%) and stereoselectivities (dr up to >95:5, ee=97 to >99%). [source] Organocatalytic Asymmetric Michael Addition of Pyrazolin-5-ones to Nitroolefins with Bifunctional Thiourea: Stereocontrolled Construction of Contiguous Quaternary and Tertiary StereocentersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Yu-Hua Liao Abstract The first organocatalytic diastereo- and enantioselective Michael addition reaction of 4-substituted-pyrazolin-5-ones to nitroolefins has been developed with a chiral bifunctional thiourea as organocatalyst. A wide variety of desired multi-substituted pyrazolin-5-one derivatives with contiguous quaternary and tertiary stereocenters are smoothly obtained in very good yields (up to 98%) with excellent enantioselectivities (up to>99% ee) and acceptable diastereoselectivities (up to 80:20). This experimentally simple process facilitates the access to various enantioenriched, multiply substituted pyrazolin-5-one derivatives, potential biologically active molecules, starting from readily available starting materials. [source] Prolylprolinol-Catalyzed Asymmetric Michael Addition of Aliphatic Aldehydes to NitroalkenesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2010Dengfu Lu Abstract Several novel prolylprolinol catalysts have been designed and synthesized. This type of compound showed high catalytic efficiency on promoting the direct addition of unmodified aldehydes to nitroalkenes. Among the catalysts surveyed, the least bulky member (8d) exhibited the best performance on both efficiency and stereoselectivity, providing the products with up to 97% ee value with 1.5,5,mol% catalyst loading. Additionally, computational studies of the transition state have been conducted to explain the high diastereo- and enantioselectivity. [source] Back to Natural Cinchona Alkaloids: Highly Enantioselective Michael Addition of Malononitrile to EnonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Alessio Russo Abstract An efficient and convenient highly enantioselective Michael addition of malononitrile to enones has been developed by using quinine as the organocatalyst. The adducts were isolated in excellent yield and high asymmetric induction (up to 95% ee). An easy route to difficultly accessible ester derivatives has been also disclosed. [source] Highly Efficient Ion-Tagged Catalyst for the Enantioselective Michael Addition of Aldehydes to NitroalkenesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Marco Lombardo Abstract The ion-tagged diphenylprolinol silyl ether 6 very efficiently catalyzes the asymmetric Michael addition of aliphatic aldehydes to nitroalkenes with ee of up to>99.5% at low catalyst loadings (0.25,5,mol%) and using only a slight excess of aldehydes (1.2,2,equiv.). This new organocatalyst can be used with the same outstanding efficiency in a wide variety of solvents and reaction conditions. [source] Highly Enantioselective Michael Addition of ,-Substituted Cyano Ketones to ,,,-Unsaturated ,-Keto Esters using Bifunctional Thiourea-Tertiary Amine Catalysts: An Easy Access to Chiral DihydropyransADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Sheng-Li Zhao Abstract An asymmetric Michael addition of ,-substituted cyano ketones to ,,,-unsaturated ,-keto esters to form chiral dihydropyrans catalyzed by a series of ,-amino acid-derived thiourea-tertiary amines is presented. A novel tyrosine-derived thiourea catalyst was identified as the optimal catalyst providing the desired product in 91,95% yields and with 90,96% ee at a low catalyst loading of 2.0,mol%. The utility of the reaction was exemplified by facile conversion of the dihydropyran product into pharmaceutically useful dihydropyridine. [source] Organocatalytic Activity of N-Heterocyclic Carbenes in the Michael Addition of 1,3-Dicarbonyl Compounds: Application to a Stereoselective Spirocyclization SequenceADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Thomas Boddaert No abstract is available for this article. [source] Organocatalytic Activity of N-Heterocyclic Carbenes in the Michael Addition of 1,3-Dicarbonyl Compounds: Application to a Stereoselective Spirocyclization SequenceADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Thomas Boddaert Abstract An eco-compatible diversity-oriented synthesis of ,-spirolactones and ,-spirolactams is described. The overall transformation involves an olefin cross-metathesis followed by an intramolecular organocatalytic Michael-induced spirocyclization. Under microwave irradiation, the Hoveyda,Grubbs precatalyst can be iteratively used as the source of both the metathesis ruthenium-based catalyst, and the spirocyclization N-heterocyclic carbene catalyst. [source] A New Stereoselective Synthesis of Cyclopropanes Containing Quaternary Stereocentres via Organocatalytic Michael Addition to Vinyl SelenonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Francesca Marini Abstract A novel organocatalytic method for the stereoselective synthesis of highly substituted cyclopropanes is reported. The Michael adducts, generated through the addition of ,-substituted cyanoacetates to easily accessible vinyl selenones catalyzed by a bifunctional ureidic catalyst, smoothly cyclize by intramolecular alkylation induced by a de-ethoxycarbonylation process. The one-pot sequence generates cyclopropanes bearing adjacent tertiary and quaternary stereocentres as single Z -isomers in moderate to high yields and good enantiomeric excesses. [source] Enantioselective Organocatalytic Michael Addition of ,-Substituted Cyanoacetates to ,,,-Unsaturated SelenonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Francesca Marini Abstract A novel enantioselective (up to 90% ee) Michael addition of ,-substituted cyanoacetates to ,,,-unsaturated selenones in the presence of bifunctional urea and thiourea organocatalysts is described. The Michael adducts, containing an all-carbon quaternary stereocenter, are smoothly converted into synthetically useful polyfunctional compounds by taking advantage of the excellent leaving group ability of the selenone group. [source] One-Pot Synthesis of Highly Substituted Allenylidene Derivatives via Palladium- or Nickel-Catalyzed Tandem Michael Addition,Cyclization ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Yun Shi Abstract A simple and tandem synthetic approach, which offers an efficient, direct route to highly substituted indenes, has been developed by palladium- or nickel-catalyzed cyclization of propargylic compounds and nitrogen nucleophiles. The reaction takes place under mild conditions, and a possible mechansim is proposed. [source] Enantioselective Michael Addition of Dicyanoolefins to ,,,-Unsaturated Aldehydes in Aqueous MediumADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2008Jun Lu Abstract A pool of water-compatible catalysts, namely dialkyl-(S)-prolinols, has been developed for the enantioselective direct vinylogous Michael addition reaction of vinylmalononitriles to ,,,-unsaturated aldehydes in aqueous medium. In many cases, the products can be obtained in almost optically pure form (>96% ee) after a single recrystallization. [source] Organocatalytic Michael Addition of Aldehydes to Protected 2-Amino-1-Nitroethenes: The Practical Syntheses of Oseltamivir (Tamiflu) and Substituted 3-Aminopyrrolidines,ANGEWANDTE CHEMIE, Issue 27 2010Shaolin Zhu Über drei verschiedene Übergangszustände können organokatalytische Michael-Additionen von Aldehyden mit geschütztem 2-Amino-1-nitroethen verlaufen und so Addukte mit gewöhnlichen wie auch ungewöhnlichen Konfigurationen ergeben. Diese Methode eröffnet einen einfachen Zugang zu Tamiflu (siehe Schema) und substituierten 3-Aminopyrrolidinen. TMS=Trimethylsilyl, Ac=Acetyl. [source] Squaramide-Catalyzed Enantioselective Michael Addition of Diphenyl Phosphite to Nitroalkenes,ANGEWANDTE CHEMIE, Issue 1 2010Ye Zhu Einfach zugänglich ist der im Schema gezeigte Squaramidkatalysator, der die hoch enantioselektive Michael-Addition von Diphenylphosphit an Nitroalkene vermittelt. Dieser Ansatz führt zu chiralen ,-Nitrophosphonaten, die Vorstufen für biologisch aktive ,-Aminophosphonsäuren sind. [source] ChemInform Abstract: Organocatalyzed Enantioselective One-Pot Three-Component Access to Indoloquinolizidines by a Michael Addition,Pictet,Spengler Sequence.CHEMINFORM, Issue 36 2010Xiaoyu Wu Abstract The title method is potentially useful in combinatorial library construction and the synthesis of natural alkaloids. [source] ChemInform Abstract: Noyori,s Ts-DPEN Ligand: Simple Yet Effective Catalyst for the Highly Enantioselective Michael Addition of Acetone to Nitroalkenes.CHEMINFORM, Issue 35 2010Lin Peng No abstract is available for this article. [source] ChemInform Abstract: Platinum-Catalyzed Michael Addition and Cyclization of Tertiary Amines with Nitroolefins by Dehydrogenation of ,,,-sp3 C,H Bonds.CHEMINFORM, Issue 35 2010Xiao-Feng Xia Abstract Mild, one-pot methods to prepare trisubstituted enamines and chromanopiperidines are reported. [source] ChemInform Abstract: Chiral Bifunctional Thiourea-Catalyzed Enantioselective Michael Addition of Ketones to Nitrodienes.CHEMINFORM, Issue 25 2010Hai Ma 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: Michael Addition,Lactonization Reaction of Electron-Deficient Alkynes with N-(Diphenylmethylene)glycinates: An Efficient Synthesis of 3-Amino-2-pyrone Derivatives.CHEMINFORM, Issue 21 2010Qing-Fa Zhou 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 Unusual Michael Addition of 3,3-Dimethoxypropanenitrile to 2-Aryl Acrylates: A Convenient Route to 4-Unsubstituted 5,6-Dihydropyrido[2,3-d]pyrimidines.CHEMINFORM, Issue 20 2010Xavier Berzosa 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: Enantioselective Michael Addition to ,,,-Unsaturated Aldehydes: Combinatorial Catalyst Preparation and Screening, Reaction Optimization, and Mechanistic Studies.CHEMINFORM, Issue 19 2010Ivana Fleischer 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: Double Michael Addition of Dithiols to Acetylenic Carbonyl Compounds under the Influence of Molecular Sieve and Dimethyl Sulfoxide.CHEMINFORM, Issue 17 2010Tomoko Kakinuma 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: Enantioselective Michael Addition of Malononitrile to Chalcones Catalyzed by a Simple Quinine,Al(OiPr)3 Complex: A Simple Method for the Synthesis of a Chiral 4H-Pyran Derivative.CHEMINFORM, Issue 51 2009Jian Shi 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] | ||||||||||||||||||||||||||||