نتایج جستجو برای: asymmetric catalyst
تعداد نتایج: 108514 فیلتر نتایج به سال:
a novel acrylic acid-functionalized fe3o4 magnetic nanoparticle with a core-shell structure was developed for utilization as a heterogeneous organosuperacid in chemical transformations. the structural, surface, and magnetic characteristics of the nanosized catalyst were investigated by various techniques such as transmission electron microscopy (tem), thermogravimetric analysis (tga), and ft-ir...
Since the innovative work of Terada and Akiyama, asymmetric reaction using chiral Brønsted acid has attracted great attention. Asymmetric aldol reactions are extensively studied in different organocatalysis. acid-catalyzed may be carried out directly without modification substrates or Mukaiyama type silyl enol ether as nucleophiles. The proceed through formation intermediate followed by attack ...
in this thesis, we exploit a simple and suitable method for immobilization of copper(ii) complex of 4?-phenyl-terpyridine on activated multi-walled carbon nanotubes [amwcnts-o-cu(ii)-phtpy]. this nanostructure was characterized by various physico-chemical techniques. to ensure the efficiency and fidelity of copper species, the implementation of three-component strategies in click-chemistry all...
A conjugate addition/asymmetric protonation/aza-Prins cascade reaction has been developed for the enantioselective synthesis of fused polycyclic indolines. A catalyst system generated from ZrCl4 and 3,3'-dibromo-BINOL enables the synthesis of a range of polycyclic indolines in good yields and with high enantioselectivity. A key finding is the use of TMSCl and 2,6-dibromophenol as a stoichiometr...
Sulfoxides are uncommon substrates for transition-metal catalysis due to their propensity to inhibit catalyst turnover. In a collaborative effort with Ken Houk, we developed the first dynamic kinetic resolution (DKR) of allylic sulfoxides using asymmetric rhodium-catalyzed hydrogenation. A detailed mechanistic analysis of this transformation using both experimental and theoretical methods revea...
Novel pyridylalkylamine and aminopyridinato ligand stabilized iridium complexes with no P ligand are introduced. These complexes have been investigated as catalysts for asymmetric hydrogenation of simple ketones, resulting in an active catalyst for bulky alkyl aryl ketones that is a-methylpropiophenone. The ligands were synthesized from inexpensive starting materials and their modular design al...
To date, effective nickel-catalyzed enantioselective cross-couplings of alkyl electrophiles that bear oxygen leaving groups have been limited to reactions of allylic alcohol derivatives with Grignard reagents. In this Communication, we establish that, in the presence of a nickel/pybox catalyst, a variety of racemic propargylic carbonates are suitable partners for asymmetric couplings with organ...
The first enantioselective organocatalytic hydride reduction has been accomplished. The use of iminium catalysis has provided a new organocatalytic strategy for the enantioselective reduction of beta,beta-substituted alpha,beta-unsaturated aldehydes to generate beta-stereogenic aldehydes. The use of imidazolidinone 2 as the asymmetric catalyst has been found to mediate the transfer of hydrogen ...
Studies are described that were designed to determine the structure of the active catalyst in the asymmetric catalytic aziridination of imines with ethyl diazoacetate (AZ reaction). Evidence suggests that the active catalyst contains a boroxine ring in which one of the three boron atoms is spiro-fused with the two phenol groups of the VAPOL ligand. (11)B and (1)H NMR evidence supports the borox...
The Jacobsen catalyst, N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese (III) chloride is covalently immobilized on mesoporous phenolic resin through a direct and simple procedure. The immobilization is evident from nitrogen sorption and quantitative XRF measurements. A complex loading of 0.09 mmol/g is obtained, corresponding to well dispersed Mn-complexes on the surface...
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