			Home About us Contact

Novel Organocatalysts (novel + organocatalyst)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Highly Efficient Organocatalyzed Direct Asymmetric Aldol Reactions of Hydroxyacetone and Aldehydes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
Xiaoyu Wu
Abstract Novel organocatalysts derived from L -threonine and L -leucine have been synthesized for catalyzing direct aldol reactions of hydroxycetone and unactivated aliphatic aldehydes with as low as 2,mol% loading of the catalyst, good to excellent yields and excellent enantioselectivities have been achieved for aliphatic aldehydes, whereas aromatic aldehydes yield only moderate enantioselectivities. [source]

,-Aminophosphonates as novel organocatalysts for asymmetric Michael addition of carbonyl compounds to nitroolefins

CHIRALITY, Issue 7 2008
Qin Tao
Abstract A cyclic ,-aminophosphonate was found to be a novel organocatalyst for Michael type addition reactions of carbonyl compounds to nitroolefins to afford the corresponding adducts in high enantio- and diastereoselectivities. Chirality, 2008. © 2008 Wiley-Liss, Inc. [source]

Nucleophilicities and Carbon Basicities of Pyridines

CHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2007
Frank Brotzel Dipl.-Chem.
Abstract Rate and equilibrium constants for the reactions of pyridines with donor-substituted benzhydrylium ions have been determined spectrophotometrically. The correlation equation log,k(20,°C)=s(N+E), in which s and N are nucleophile-specific parameters and E is an electrophile-specific parameter, has been used to determine the nucleophilicity parameters of various pyridines in CH2Cl2 and aqueous solution and to compare them with N of other nucleophiles. It is found that the nucleophilic organocatalyst 4-(dimethylamino)pyridine (DMAP) and tertiary phosphanes have comparable nucleophilicities and carbon basicities despite widely differing Brønsted basicities. For that reason, these reactivity parameters are suggested as guidelines for the development of novel organocatalysts. The Marcus equation is employed for the determination of the intrinsic barriers of these reactions. Geschwindigkeits- und Gleichgewichtskonstanten der Reaktionen von Pyridinen mit Donor-substituierten Benzhydrylium-Ionen wurden spektralphotometrisch bestimmt. Die Korrelationsgleichung log,k(20,°C)=s(N+E), die mit s und N Nucleophil-spezifische und mit E einen Elektrophil-spezifischen Parameter enthält, wurde verwendet, um die Nucleophilie-Parameter von verschiedenen Pyridinen in CH2Cl2 und in wässrigen Lösungen zu bestimmen und um diese mit N anderer Nucleophile zu vergleichen. Es wurde gefunden, dass der nucleophile Organokatalysator 4-(Dimethylamino)pyridin (DMAP) und tertiäre Phosphane vergleichbare Nucleophilien und Kohlenstoffbasizitäten haben, obwohl ihre Brønsted-Basizitäten sehr unterschiedlich sind. Daher wird vorgeschlagen, die Reaktivitätsparameter als Richtgrößen zur Entwicklung neuer Organokatalysatoren heranzuziehen. Die Marcus-Gleichung wird eingesetzt, um die intrinsischen Barrieren dieser Reaktionen zu bestimmen. [source]