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Amine Catalysts (amine + catalyst)

Distribution by Scientific Domains
Chemistry83%

Selected Abstracts

Highly Enantioselective Michael Addition of ,-Substituted Cyano Ketones to ,,,-Unsaturated ,-Keto Esters using Bifunctional Thiourea-Tertiary Amine Catalysts: An Easy Access to Chiral Dihydropyrans

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009
Sheng-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]

ChemInform Abstract: Enantioselective Synthesis of Multifunctionalized 4H-Pyran Derivatives Using Bifunctional Thiourea-tertiary Amine Catalysts.

CHEMINFORM, Issue 42 2009
Sheng-Li Zhao
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 Enantioselective Direct syn- and anti-Aldol Reactions of Dihydroxyacetones Catalyzed by Chiral Primary Amine Catalysts.

CHEMINFORM, Issue 30 2008
Sanzhong Luo
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]

Rapid Organocatalytic Aldehyde-Aldehyde Condensation Reactions

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2007
Anniina Erkkilä
Abstract We report the results of the systematic optimization of the ,-methylenation of aldehydes with aqueous formaldehyde. A simple combination of a secondary amine catalyst and a weak acid co-catalyst has been identified, allowing access to ,-substituted acroleins in a matter of minutes. In the absence of formaldehyde, the catalytic system promoted the self-condensation reaction of ,,,-unsaturated aldehydes. Both of these reactions exhibited linear relationships between co-catalyst acidities and reaction rates. A second-order dependence of catalyst concentration was observed, pointing to the involvement of two molecules of the ammonium catalyst in the rate-determining step. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Moisture curing kinetics of isocyanate ended urethane quasi-prepolymers monitored by IR spectroscopy and DSC

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
Ana Luísa Daniel-da-Silva
Abstract The study of the kinetics of the curing of isocyanate quasi-prepolymers with water was performed by infrared spectroscopy and differential scanning calorimetry. The influence of the free isocyanate content, polyol functionality, and of the addition of an amine catalyst (2,2,-dimorpholinediethylether) in the reaction kinetics and morphology of the final poly(urethane urea) was analyzed. A second-order autocatalyzed model was successfully applied to reproduce the curing process under isothermal curing conditions, until gelation occurred. A kinetic model-free approach was used to find the dependence of the effective activation energy (Ea) with the extent of cure, when the reaction was performed under nonisothermal conditions. The dependence of Ea with the reaction progress was different depending on the initial composition of the quasi-prepolymer, which reveals the complexity of the curing process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source]

Acid,Base Bifunctional Catalysis of Silica,Alumina-Supported Organic Amines for Carbon,Carbon Bond-Forming Reactions

CHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2008
Ken Motokura Dr.
Abstract Acid,base bifunctional heterogeneous catalysts were prepared by the reaction of an acidic silica,alumina (SA) surface with silane-coupling reagents possessing amino functional groups. The obtained SA-supported amines (SA,NR2) were characterized by solid-state 13C and 29Si,NMR spectroscopy, FT-IR spectroscopy, and elemental analysis. The solid-state NMR spectra revealed that the amines were immobilized by acid,base interactions at the SA surface. The interactions between the surface acidic sites and the immobilized basic amines were weaker than the interactions between the SA and free amines. The catalytic performances of the SA,NR2 catalysts for various carbon,carbon bond-forming reactions, such as cyano-ethoxycarbonylation, the Michael reaction, and the nitro-aldol reaction, were investigated and compared with those of homogeneous and other heterogeneous catalysts. The SA,NR2 catalysts showed much higher catalytic activities for the carbon,carbon bond-forming reactions than heterogeneous amine catalysts using other supports, such as SiO2 and Al2O3. On the other hand, homogeneous amines hardly promoted these reactions under similar reaction conditions, and the catalytic behavior of SA,NR2 was also different from that of MgO, which was employed as a typical heterogeneous base. An acid,base dual-activation mechanism for the carbon,carbon bond-forming reactions is proposed. [source]