نتایج جستجو برای: nucleophile
تعداد نتایج: 1574 فیلتر نتایج به سال:
Bleach oxidizes trimethylsilyl cyanide to generate an electrophilic cyanating reagent that readily reacts with an amine nucleophile. This oxidative N-cyanation reaction allows for the preparation of disubstituted cyanamides from amines without using highly toxic cyanogen halides.
SNi-like mechanisms, which involve front-face leaving group departure and nucleophile approach, have been observed experimentally and computationally in chemical and enzymatic substitution at α-glycosyl electrophiles. Since SNi-like, SN1 and SN2 substitution pathways can be energetically comparable, engineered switching could be feasible. Here, engineering of Sulfolobus solfataricus β-glycosida...
Anthranilate synthase (AS), aminodeoxychorismate synthase (ADCS), isochorismate synthase (IS), and salicylate synthase (SS) are structurally homologous chorismate-utilizing enzymes that carry out the first committed step in the formation of tryptophan, folate, and the siderophores enterobactin and mycobactin, respectively. Each enzyme catalyzes a nucleophilic substitution reaction, but IS and S...
The dissimilatory nitrite reductase (cytochrome c,d1) from Pseudomonas aeruginosa was observed at pH 7.5 to catalyze nitrosyl transfer (nitrosation) between [15N]nitrite and several N-nucleophiles or H2 18O, with rate enhancement of the order of 10(8) relative to analogous chemical reactions. The reducing system (ascorbate, N,N,N',N'-tetramethylphenylenediamine) could reduce nitrite (but not NO...
This work deals with exploring some empirical scales of nucleophilicity. We have started evaluating the experimental indices of nucleophilicity proposed by Legon and Millen on the basis of the measure of the force constants derived from vibrational frequencies using a probe dipole H-X (X = F,CN). The correlation among some theoretical parameters with this experimental scale has been evaluated. ...
The organocatalytic generation of a strong base by the action of a good nucleophile is the base for the in situ catalytic generation of conjugated acetylides in the presence of aldehydes or activated ketones. The method is affordable in a multicomponent, domino format able to generate a chemically diverse set of multifunctionalized adducts that are very well suited for diversity-oriented molecu...
[reaction: see text]. We describe a superior procedure for the catalytic, asymmetric synthesis of beta-lactams using a bifunctional catalyst system consisting of a chiral nucleophile and an achiral Lewis acid.
This article describes the aza-Piancatelli rearrangement with hydroxylamines to 4-aminocyclopentenones and subsequent transformations that highlight the versatility of the cyclopentene scaffold and the value of the hydroxylamine nucleophile in this transformation.
The ability of triazolium salts to serve as a precatalyst for both an acid and a powerful base/nucleophile (controlled by additives) has been exploited in a process characterised by a unique in situ catalyst modification strategy.
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