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Asymmetric Michael Reactions (asymmetric + michael_reaction)
Selected AbstractsHighly Efficient Asymmetric Michael Reaction of Aldehydes to Nitroalkenes with Diphenylperhydroindolinol Silyl Ethers as OrganocatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Ren-Shi Luo Abstract New dihydroindole and perhydroindole derivatives were synthesized in good yields and evaluated as chiral catalysts in the asymmetric Michael reaction of aldehydes to nitroalkenes. (2S,3aS,7aS)-Diphenylperhydroindolinol silyl ether 10 facilitated the reaction of a wide range of aldehyde and nitroalkene substrates, providing Michael adducts in nearly optically pure form (99% ee), good yields and high diastereoselectivities (syn/anti up to 99:1). These results show for the first time that perhydroindole derivatives can also be highly efficient organocatalysts for the asymmetric Michael reaction, exhibiting comparable or even better enantioselectivities than proline derivatives. [source] ChemInform Abstract: Highly Efficient Asymmetric Michael Reaction of Aldehydes to Nitroalkenes with Diphenylperhydroindolinol Silyl Ethers as Organocatalysts.CHEMINFORM, Issue 6 2010Ren-Shi Luo 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] Asymmetric Michael Reaction: Novel Efficient Access to Chiral ,-Ketophosphonates (III).CHEMINFORM, Issue 34 2007Sandrine Delarue-Cochin 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] Asymmetric Michael Reaction Between a Chiral ,,,-Dimethyl-,-enamino Ester and ,-Substituted Acrylates.CHEMINFORM, Issue 28 2004Frederic Hendra Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Asymmetric Michael Reaction of Diethyl Malonate with Crotonaldehyde Catalyzed by Chiral Aminocarboxylates, Amino Alcoholates, and Amino Phenolates.CHEMINFORM, Issue 23 2002K. A. Kochetkov 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] Synthesis and Characterisation of New Iridium Complexes with the (4S)-2-[2-(Diphenylphosphanyl)phenyl]-4-isopropyl-1,3-oxazoline Ligand That Catalyse Asymmetric Michael ReactionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2005Daniel Carmona Abstract The chiral iridium compounds [IrCl(COE){(S)-PN}] {COE = cyclooctene, PN = (4S)-2-[2-(diphenylphosphanyl)phenyl]-4-isopropyl-1,3-oxazoline, (1)}, [Ir(acac)ClH{(S)-PN}] {Hacac = acetylacetone, (2)} and [Ir{(S)-PN}2]A {A = Cl (3a,b); BF4 (4a,b); PF6 (5a,b)} have been prepared, characterised and employed as catalysts for the asymmetric Michael addition of keto or cyano esters to ,,,-unsaturated carbonyl compounds. The X-ray molecular structures of compounds 2 and 5b are reported. The model catalytic intermediates [IrH(NCCHCO2R){(S)-PN}2]Cl {R = Me (12), Et (13)} have also been isolated and characterised. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Transition States of the Asymmetric Michael Reactions of Aldehydes Catalyzed by Trimethylsilyl-Protected DiphenylprolinolEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2009Jian-Qiang Zhao Abstract The asymmetric Michael reactions of aldehydes and nitroalkenes catalyzed by trimethylsilyl-protected diphenylprolinol were investigated by using density functional theory calculations. As a result of the stereospecific blockade of the bulky diphenylsiloxymethyl group on the pyrrolidine ring, the Re face of the enamine double bond is effectively shielded. For acetaldehyde, there are two different conformers of the enamine intermediate. On the basis of the two conformers of the enamine intermediate, four different reaction pathways were considered and four different transition states were searched for the enantioselective asymmetric Michael reaction of acetaldehyde and nitroalkene. The lowest- and second-lowest-energy transition states are both formed via the same intermediate IM2. The enantiomeric excess, calculated to be 96,%,ee, is in good agreement with the experimental value. For propanal, on the basis of the four different conformers of the prolinol,enamine intermediate, eight different reaction pathways were considered and eight transition states were searched for the enantioselective asymmetric Michael reaction. The calculated ee value is 99.5,%, which is in good agreement with the experimental ee value of 99,%. The lowest- and second-lowest-energy transition states are formed via different enamine intermediates, which is different from the case of acetaldehyde. The calculations also reveal that the intermediates play an important role in the reactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] anti -Selective Asymmetric Michael Reactions of Aldehydes and Nitroolefins Catalyzed by a Primary Amine/Thiourea,ANGEWANDTE CHEMIE, Issue 52 2009Hisatoshi Uehara Dr. "anti" geht auch: Hoch anti -selektive Michael-Reaktionen eines funktionalisierten Aldehyds mit Nitroolefinen gelangen in Gegenwart eines Katalysators mit primärer Amino- und Thioharnstoff-Funktion (siehe Schema; TBS=tert -Butyldimethylsilyl). Die Reaktion beruht auf der Bildung eines Z -konfigurierten Enamin-Intermediats. [source] Bifunctional Guanidine via an Amino Amide Skeleton for Asymmetric Michael Reactions of ,-Ketoesters with Nitroolefins: A Concise Synthesis of Bicyclic ,-Amino Acids,ANGEWANDTE CHEMIE, Issue 44 2009Zhipeng Yu No abstract is available for this article. [source] ChemInform Abstract: Catalytic, Asymmetric Michael Reactions of Cyclic Diketones with ,,,-Unsaturated ,-Ketoesters.CHEMINFORM, Issue 40 2009Michael A. Calter 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: Calcium-BINOL: A Novel and Efficient Catalyst for Asymmetric Michael Reactions.CHEMINFORM, Issue 9 2002G. Kumaraswamy 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] Transition States of the Asymmetric Michael Reactions of Aldehydes Catalyzed by Trimethylsilyl-Protected DiphenylprolinolEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2009Jian-Qiang Zhao Abstract The asymmetric Michael reactions of aldehydes and nitroalkenes catalyzed by trimethylsilyl-protected diphenylprolinol were investigated by using density functional theory calculations. As a result of the stereospecific blockade of the bulky diphenylsiloxymethyl group on the pyrrolidine ring, the Re face of the enamine double bond is effectively shielded. For acetaldehyde, there are two different conformers of the enamine intermediate. On the basis of the two conformers of the enamine intermediate, four different reaction pathways were considered and four different transition states were searched for the enantioselective asymmetric Michael reaction of acetaldehyde and nitroalkene. The lowest- and second-lowest-energy transition states are both formed via the same intermediate IM2. The enantiomeric excess, calculated to be 96,%,ee, is in good agreement with the experimental value. For propanal, on the basis of the four different conformers of the prolinol,enamine intermediate, eight different reaction pathways were considered and eight transition states were searched for the enantioselective asymmetric Michael reaction. The calculated ee value is 99.5,%, which is in good agreement with the experimental ee value of 99,%. The lowest- and second-lowest-energy transition states are formed via different enamine intermediates, which is different from the case of acetaldehyde. The calculations also reveal that the intermediates play an important role in the reactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Highly Efficient Asymmetric Michael Reaction of Aldehydes to Nitroalkenes with Diphenylperhydroindolinol Silyl Ethers as OrganocatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Ren-Shi Luo Abstract New dihydroindole and perhydroindole derivatives were synthesized in good yields and evaluated as chiral catalysts in the asymmetric Michael reaction of aldehydes to nitroalkenes. (2S,3aS,7aS)-Diphenylperhydroindolinol silyl ether 10 facilitated the reaction of a wide range of aldehyde and nitroalkene substrates, providing Michael adducts in nearly optically pure form (99% ee), good yields and high diastereoselectivities (syn/anti up to 99:1). These results show for the first time that perhydroindole derivatives can also be highly efficient organocatalysts for the asymmetric Michael reaction, exhibiting comparable or even better enantioselectivities than proline derivatives. [source] Pyrrolidine-Camphor Derivative as an Organocatalyst for Asymmetic Michael Additions of ,,,-Disubstituted Aldehydes to ,-Nitroalkenes: Construction of Quaternary Carbon-Bearing Aldehydes under Solvent-Free ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Chihliang Chang Abstract A novel pyrrolidine-camphor organocatalyst 3 was designed, synthesized and proven to be an efficient catalyst for the asymmetric Michael reaction. Treatment of ,,,-disubstituted aldehydes with ,-nitroalkenes in the presence of 20,mol% organocatalyst 3 and 20,mol% benzoic acid under solvent-free conditions provided the desired Michael product possessing an all-carbon quaternary center with high chemical yields (up to 99% yield) and high levels of enantioselectivities (up to 95% ee). [source] | ||||||||||