نتایج جستجو برای: organocatalysis
تعداد نتایج: 465 فیلتر نتایج به سال:
The effects of hydrogen-bonding organocatalysts and water for the acceleration of epoxide openings with a variety of nucleophiles are additive and lead to excellent yields of the catalyzed reactions in water.
In the investigation of efficient chemical transformations, the carbon-carbon bond-forming reactions play an outstanding role. In this context, organocatalytic processes have achieved considerable attention.1 Beside their facile reaction course, selectivity, and environmental friendliness, new synthetic strategies are made possible. Particularly, the inversion of the classical reactivity (Umpol...
A practical approach for the α-stereoselective synthesis of deoxyglycosides using cooperative Brønsted acid-type organocatalysis has been developed. The method is tolerant of a wide range of glycoside donors and acceptors, and its versatility is exemplified in the one-pot synthesis of a trisaccharide. Mechanistic studies suggest that thiourea-induced acid amplification of the chiral acid via H-...
The first highly enantioselective α-fluorination of ketones using organocatalysis has been accomplished. The long-standing problem of enantioselective ketone α-fluorination via enamine activation has been overcome via high-throughput evaluation of a new library of amine catalysts. The optimal system, a primary amine functionalized Cinchona alkaloid, allows the direct and asymmetric α-fluorinati...
In the presence of alkynes (CH?C–R2), iodide chain-end polymers (Polymer–I) were successfully transformed to vinyl (Polymer–CH?CR2–I) in a single step via organocatalysis.
The aldol reaction of the endogeneous compounds acetone and methylglyoxal has been studied using organocatalysis in relation to biologically relevant non-enzymatic reactions. Under preparative conditions, 3-hydroxy-2,5-hexadione, known as Henze's ketol, is formed in high yield and with enantioselectivities up to 88% ee. Furthermore, Henze's ketol is also formed under simulated physiological con...
A sterically demanding unsymmetrical pentafluorophenyl-triisopropylphenyl-λ(3)-iodane was developed as an effective reagent for the electrophilic pentafluorophenylation of various β-keto esters and a β-keto amide. 17 examples of α-pentafluorophenylated 1,3-dicarbonyl compounds 3 having a quaternary carbon center are provided. The resulting compounds were nicely transformed into chiral α-pentafl...
Selective modification of unprotected carbohydrates is difficult due to the similar reactivity of the hydroxyl groups. In carbohydrate synthesis, therefore, even straightforward transformations often require multiple synthetic steps. The development of selective methods for carbohydrate modification is consequently highly desired. This review describes the methods for the regio- and chemoselect...
An N-heterocyclic carbene (NHC) catalyzed domino reaction triggered by a δ-LUMO activation of α,β-γ,δ-diunsaturated enal has been developed for the formal [4 + 2] construction of multisubstituted arenes and 3-ylidenephthalide. These two products, formed in a highly chemo- and regioselective manner, were obtained via different catalytic pathways due to a simple change of the substrate. The activ...
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