نتایج جستجو برای: ketoesters
تعداد نتایج: 289 فیلتر نتایج به سال:
Inhibition of cyclooxygenase-2 (COX-2) has been extensively studied as an approach to reduce proinflammatory markers in acute brain diseases, but the anti-neuroinflammatory role cyclooxygenase-1 (COX-1) inhibition rather neglected. We report that m-terphenylamine derivatives are selective COX-1 inhibitors, able block microglia inflammatory response and elicit a neuroprotective effect. These com...
α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursor: enol carbonates, enol silanes, and racemic β-ke...
Chiral metal catalysts have been widely applied to asymmetric transformations. However, the electronic structure of the catalyst and how it contributes to the activation of the substrate is seldom investigated. Here, we report an empirical approach for providing insights into the catalytic activation process in the distorted Ni(II)-catalysed asymmetric [3+2] cycloaddition of α-ketoesters. We qu...
This study describes the combined experimental and computational elucidation of the mechanism and origins of stereoselectivities in the NHC-catalyzed dynamic kinetic resolution (DKR) of α-substituted-β-ketoesters. Density functional theory computations reveal that the NHC-catalyzed DKR proceeds by two mechanisms, depending on the stereochemistry around the forming bond: 1) a concerted, asynchro...
Starting from γ-ketoesters with an o-iodobenzyl group we studied a palladium-catalyzed cyclization process that stereoselectively led to bi- and tricyclic compounds in moderate to excellent yields. Four X-ray crystal structure analyses unequivocally defined the structure of crucial cyclization products. The relative configuration of the precursor compounds is essentially transferred to that of ...
Asymmetric Michael additions of 1,3-dicarbonyl compounds to N-substituted maleimides were carried out using primary amine-(thio)phosphoramide bifunctional chiral organocatalysts derived from optically pure C2-symmetric 1,2-diamines. The addition ethyl 2-fluoroacetoacetate the 1,2-diphenylethane-1,2-diamine thiophosphoramide catalyst afforded various succinimides substituted with fluorine bearin...
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