Search results for "functional"

Recent Developments in the Chiral Brønsted Acid-catalyzed Allylboration Reaction with Polyfunctionalized Substrates

2016

Asymmetric allylboration has played a central role in organic synthesis ever since the pioneering work by Hoffman and Brown, having found applications in the total synthesis of many natural products. A new dawn for this 40 year-old reaction occurred with the beginning of the new century when the first catalytic asymmetric methods came into play. In less than one decade, several methodologies, able to achieve the desired homoallylic alcohols with ee ranges in the high 90s, were developed. Among them, in the present account, we will disclose our contribution to the development of the chiral binolphosphoric-derived BrOnsted acid-catalyzed allylboration of aldehydes originally reported by Antil…

Lithium Cation-Catalyzed Benzene Diels-Alder Reaction: Insights on the Molecular Mechanism Within the Molecular Electron Density Theory.

2020

The lithium cation Li+-catalyzed Diels-Alder (DA) reactions of benzene toward a series of acetylenes of improved nucleophilicity can be described within the context of the molecular electron density theory (MEDT) at the ωB97XD/6-311G(d,p) level. Conceptual density functional theory indices characterize the crown ether solvated complex benzene-lithium Bz-Li-Cro as a superelectrophile. Coordination of a lithium cation to benzene does not change substantially the electron localization function electronic structure of benzene. The DA reaction of Bz-Li-Cro with acetylene shows a reduction of the energy of activation of 6.9 kcal·mol-1, which is not sufficient for the reaction to take place, thus …

Theoretical Studies of the Reactivity of Cyclopentadienyl Nitrosyl Alkyl Species of Molybdenum and Tungsten

2000

International audience; The reactivity differences observed experimentally for Cp*W(NO)(CH2CMe3)2 and CpMo(NO)(CH2CMe3)2 have been investigated using density functional theory (DFT) techniques. The reactions of the CpW(NO)(CH2) model complex with NH3 and CH4 are more exothermic and have lower activation barriers than the corresponding processes for CpMo(NO)(CH2). The η2(C,H) methane complex CpM(NO)(CH2)(CH4) (M = Mo, W) can undergo two competitive processes:  C−H activation to afford CpM(NO)(CH3)2 or loss of methane. The relative barrier heights are almost identical for M = W, whereas the formation of CpM(NO)(CH3)2 is significantly disfavored for M = Mo. The activation of C−H and N−H bonds …

Influence of structural elements on iron(III) chelating properties in a new series of amino acid-derived monohydroxamates

2018

Abstract A series of amino acid-derived monohydroxamate compounds A1 – A7 was synthesized and characterized for their coordination properties of Fe(III). The series varies in their skeletal lengths and compositions; some compounds lack external substituents, others are substituted with external functional amino or carboxylic groups, or alternatively inert methyl. Undertaken investigations allowed the determination of stoichiometry, stability constants and spectroscopic parameters of formed ferric complexes. Incorporation of an external functional group with a dissociable proton affects the coordination behavior; the presence of carboxylic or amino groups hampers the formation of mono-, di- …

Bifunctional coordination polymers as efficient catalysts for carbon dioxide conversion

2019

Tri- and tetranuclear heteropivalate complexes with core {Fe2Ni O} (x = 1, 2): Synthesis, structure, magnetic and thermal properties

2019

Abstract The reactions of complex [Fe2Ni(O)(Piv)6(Et2O)(H2O)2] (1) with 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) gave the following new coordination compounds: the trinuclear complex [Fe2Ni(O)(Piv)6(phen)H2O]·(C2H5)2O (2), the tetranuclear ones [Fe2Ni2(OH)2(Piv)8(phen)2] (3) and [Fe2Ni2(OH)2(Piv)8(bpy)2] (4), depending on the crystallization conditions. According to single crystal X-ray diffraction data, all the compounds have molecular structures. The Mossbauer spectra of 1–3 correspond to high-spin Fe3+ ions in an octahedral environment consisting of oxygen atoms. The DC magnetic susceptibility studies and quantum-chemical analysis of intra- and intermolecular J pathways using…

Synthesis of CO2-responsive polymers by post-polymerization modification

2014

Abstract We describe a general method to synthesize a double responsive polymer, exhibiting a temperature and CO 2 responsive behavior. The polymer derived from a controlled radical polymerization technique of pentafluorophenyl acrylate (PFPA), followed by a sequential post-polymerization modification of a CO 2 responsive- and thermo-responsive amines. Utilizing this approach three double responsive copolymers were synthesized, poly(3- N′,N′ -dimethylaminopropyl acrylamide- co - N -isopropyl acrylamide) (poly(DMPA- co -NIPAM)), poly( L -Arginine methyl ester acrylamide- co - N -isopropyl acrylamide) (poly(AME- co -NIPAM)) and poly( L -Arginine methyl ester acrylamide- co - N -cyclopropyl ac…

C2-Symmetric Ferrocene-Bis(ureido)peptides : Synthesis, Conformation and Solid-State Structure

2009

The extension of peptide derivatives of ferrocene-1,1'-dicarboxylic acid by formal insertion of NH units between ferrocene and peptide strands results in ferrocene-bis(ureido)-peptides. Experimentally, alanine and dialanine methyl esters were attached to the 1- and 1'-position of 1,1'-diiso-cyanoferrocene to give the corresponding bis(ureido)peptide derivatives 3 and 4. The conformation of 3 has been determined in the solid state by X-ray crystallography. In solution the preferred conformation of 3 and 4 has been elucidated by NMR, IR and CD spectroscopy in concert with DFT calculations. The secondary structure of ferrocene―bis(ureido)peptides 3 and 4 is determined by double bifurcated intr…

Extraction of dansylated amino acids using the supported liquid membrane technique

1997

Extraction using the supported liquid membrane (SLM) technique demands conditions where the extracted compounds can be made uncharged allowing them to pass through the membrane. For amino acids, being bifunctional, such conditions can not be obtained directly. One way to overcome this problem is to block one of the functionalities by derivatization, utilising the other group for the transport. The SLM extraction of dansylated amino acids was investigated and optimized. It was possible to obtain high extraction efficiencies (>90%) for most amino acids. For amino acids with polar side chains, such high extraction efficiencies were only obtained at low analyte concentrations ( 10 nmol 1-l). Fo…

Extruded Expanded Polystyrene Sheets Coated by TiO2 as New Photocatalitic Materials for Foodstuffs Packaging

2012

Nanostructured, photoactive anatase TiO2 sol prepared under very mild conditions using titanium tetraisopropoxide as the precursor is used to functionalise extruded expanded polystyrene (XPS) sheets by spray-coating resulting in stable and active materials functionalised by TiO2 nanoparticles. Photocatalytic tests of these sheets performed in a batch reactor in gas-solid system under UV irradiation show their successful activity in degrading probe molecules (2-propanol, trimethylamine and ethene). Raman spectra ensure the deposition of TiO2 as crystalline anatase phase on the polymer surface. The presence of TiO2 with respect to polymer surface can be observed in SEM images coupled to EDAX …