|
| ||
|
|
||
Bifunctional Organocatalyst (bifunctional + organocatalyst)
Selected AbstractsA Novel Cost-Effective Thiourea Bifunctional Organocatalyst for Highly Enantioselective Alcoholysis of meso -Cyclic Anhydrides: Enhanced Enantioselectivity by Configuration InversionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Su-Xi Wang Abstract A novel inexpensive thiourea bifunctional organocatalyst which can promote the highly enantioselective (up to 95% ee) alcoholysis of meso -cyclic anhydrides has been developed. Computational studies on the catalytic process as well as a synthetic application of this new catalyst are also presented. [source] Enantioselective Aza-Henry Reaction with Acyclic Guanidine-Thiourea Bifunctional OrganocatalystADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Keisuke Takada Abstract A highly enantioselective aza-Henry reaction of imines with nitromethane was achieved with a reactive guanidine-thiourea bifunctional organocatalyst affording ,-nitroamines with high enantioselectivity (up to 96% ee). The diastereo- and enantioselective version of this reaction with nitroalkanes also proceeded selectively (up to 99:1 dr with 99% ee). [source] ChemInform Abstract: Enantioselective Aza-Henry Reaction with Acyclic Guanidine-Thiourea Bifunctional Organocatalyst.CHEMINFORM, Issue 26 2009Keisuke Takada 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: N-Tosyl-(Sa)-binam-L-prolinamide as Highly Efficient Bifunctional Organocatalyst for the General Enantioselective Solvent-Free Aldol Reaction.CHEMINFORM, Issue 15 2009Gabriela Guillena 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: Oxazoline,Thiourea as a Bifunctional Organocatalyst: Enantioselective aza-Henry Reactions.CHEMINFORM, Issue 3 2008Yu-wei Chang 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] Enantioselective Cyanosilylation of ,,,-Dialkoxy Ketones Catalyzed by Proline-Derived in situ Prepared N-Oxide as Bifunctional Organocatalyst.CHEMINFORM, Issue 32 2007Bo Qin 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] Enantioselective Michael Addition to ,,,-Unsaturated Imides Catalyzed by a Bifunctional Organocatalyst.CHEMINFORM, Issue 44 2005Yasutaka Hoashi Abstract For Abstract see ChemInform Abstract in Full Text. [source] A Novel Cost-Effective Thiourea Bifunctional Organocatalyst for Highly Enantioselective Alcoholysis of meso -Cyclic Anhydrides: Enhanced Enantioselectivity by Configuration InversionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Su-Xi Wang Abstract A novel inexpensive thiourea bifunctional organocatalyst which can promote the highly enantioselective (up to 95% ee) alcoholysis of meso -cyclic anhydrides has been developed. Computational studies on the catalytic process as well as a synthetic application of this new catalyst are also presented. [source] First Enantioselective Synthesis of (R)-Convolutamydine B and E with N -(Heteroarenesulfonyl)prolinamidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2009Noriyuki Hara Crossed-aldol reaction: The synthesis of (R)-convolutamydine E has been achieved by the crossed-aldol reaction of acetaldehyde with 4,6-dibromoisatin (1: X = Y = Br) by using a bifunctional organocatalyst. This strategy allows the enantioselective synthesis of (R)-convolutamydine E derivatives and convolutamydine B. [source] Enantioselective Alcoholysis of meso -Glutaric Anhydrides Catalyzed by Cinchona -Based Sulfonamide CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Sang Eun Park Abstract The bifunctional Cinchona -based sulfonamide catalysts showed the highest levels of enantioselectivity reported to date in the alcoholytic desymmetrization of meso -glutaric anhydrides. Density functional theory (DFT) computational studies provide detailed insight into the observed sense of enantioselectivity. Moreover, detailed experimental studies and single crystal X-ray analysis confirmed that these bifunctional organocatalysts 3 do not form H-bonded self-aggregates in both solution and solid state. The synthetic utility of this methodology was also demonstrated in the synthesis of pharmaceutically important ,-amino acids, such as (S)-pregabalin. Of the many asymmetric syntheses of enantiomerically pure (S)-pregabalin reported to date, our synthesis requires the least number of and the simplest steps. [source] Novel Cinchona -Aminobenzimidazole Bifunctional OrganocatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Lei Zhang Abstract Efficient Cinchona -derived chiral 2-aminobenzimidazole catalysts were prepared by the coupling of 5,7-bis(trifluoromethyl)-2-chlorobenzimidazole with C(9S)-aminodihydroquinine or C(9R)-aminodihydroquinidine and successively applied to the Michael addition of dimethyl malonate to nitroolefins as very efficient chiral Lewis acid bifunctional organocatalysts (up to >99% ee). [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] Polymer-Supported Highly Enantioselective Catalyst for Nitro-Michael Addition: Tuning through Variation of the Number of H-Bond Donors and Spacer LengthADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Lital Tuchman-Shukron Abstract Two series of polymer-bound bifunctional organocatalysts, based on chiral diamine scaffolds, were prepared by solid-phase synthesis. The series, incorporating a single hydrogen bond donor carbamate functionality, was notably more enantioselective in the Michael reaction of acetone and nitrostyrene than the series that includes a double hydrogen bond donor urea moiety, or the polymer-bound diamine that lacks sufficiently acidic protons. The best aminocarbamate catalyst promoted the addition of acetone to nitroolefins with enantioselectivity unmatched by known heterogeneous catalysts. Introduction of a short linear spacer between the support and the scaffold improves the activity but reduces the selectivity of the catalyst. Alternatively, an increase in the reaction yield could be induced by the benzoic acid additive. [source] | ||||||||||