نتایج جستجو برای: nucleophile

تعداد نتایج: 1574  

2015
Pavel Kočovský Jan-E Bäckvall

In this review the stereochemistry of palladium-catalyzed addition of nucleophiles to alkenes is discussed, and examples of these reactions in organic synthesis are given. Most of the reactions discussed involve oxygen and nitrogen nucleophiles; the Wacker oxidation of ethylene has been reviewed in detail. An anti-hydroxypalladation in the Wacker oxidation has strong support from both experimen...

2011
Benan Kilbas Metin Balci

Oxazolidinones can be synthesized starting from cyclic biscarbamates via a palladium-catalyzed reaction. To test the proposed mechanism of this reaction, first, bicyclonorcarene endoperoxides derived from cyano and carbomethoxy cycloheptatrienes were synthesized and converted into the corresponding diols. The reaction of diols with toluenesulfonyl isocyanate followed by a palladium catalyzed re...

Journal: :Journal of the American Chemical Society 2010
Z Jane Wang Diego Benitez Ekaterina Tkatchouk William A Goddard F Dean Toste

The intermolecular hydroamination of allenes occurs readily with hydrazide nucleophiles, in the presence of 3-12% Ph(3)PAuNTf(2). Mechanistic studies have been conducted to establish the resting state of the gold catalyst, the kinetic order of the reaction, the effect of ligand electronics on the overall rate, and the reversibility of the last steps in the catalytic cycle. We have found the ove...

2017
Christopher D Bayer Bert van Loo Florian Hollfelder

Catalytic promiscuity can facilitate evolution of enzyme functions-a multifunctional catalyst may act as a springboard for efficient functional adaptation. We test the effect of single mutations on multiple activities in two groups of promiscuous AP superfamily members to probe this hypothesis. We quantify the effect of site-saturating mutagenesis of an analogous, nucleophile-flanking residue i...

2014
Hugh Heldenbrand Pawel A. Janowski George Giambaşu Timothy J. Giese Joseph E. Wedekind Darrin M. York

The hairpin ribozyme accelerates a phosphoryl transfer reaction without catalytic participation of divalent metal ions. Residues A38 and G8 have been implicated as playing roles in general acid and base catalysis, respectively. Here we explore the structure and dynamics of key active site residues using more than 1 μs of molecular dynamics simulations of the hairpin ribozyme at different stages...

Journal: :Journal of the American Chemical Society 2007
Nathan D Shapiro F Dean Toste

Recently, gold-carbenoid species have been proposed as intermediates in gold-catalyzed enyne rearrangements.1 Additionally, the reaction of gold complexes with propargyl esters has been developed as an alternative approach to metal carbenoids capable of effecting olefin cyclopropanation;2,3 however, to date, the reaction of electrophilic metals with alkynes has not been amenable to the generati...

2015
Miguel Ribeiro Fernando M. Nunes Sofia Guedes Pedro Domingues Amélia M. Silva Jose Maria Carrillo Marta Rodriguez-Quijano Gérard Branlard Gilberto Igrejas

Protein engineering of gluten, the exogenous effector in celiac disease, seeking its detoxification by selective chemical modification of toxic epitopes is a very attractive strategy and promising technology when compared to pharmacological treatment or genetic engineering of wheat. Here we present a simple and efficient chemo-enzymatic methodology that decreases celiac disease toxic epitopes o...

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