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Of Functional Groups (of + functional_groups)

Distribution by Scientific Domains
Chemistry100%

Kinds of Of Functional Groups

  • variety of functional groups
    		•

    Selected Abstracts

    Palladium-Catalyzed C2 or C5 Direct Arylation of 3-Formylthiophene Derivatives with Aryl Bromides

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2010
    Jia Jia Dong
    Abstract The system Pd(OAc)2/dppb was found to be an efficient catalyst precursor for the direct arylation of 3-formylthiophene derivatives. When using 3-formylthiophene, the 2-arylated thiophenes were obtained with regioselectivities of 76,86,%, whereas the arylation of 3-formylthiophene diethyl acetal gave the 5-arylated thiophenes with regioselectivities of 64,88,%. These reactions were performed by using only 0.1 mol-% of the catalyst. Moreover, this procedure has been found to be tolerant to a variety of functional groups on the aryl bromide such as formyl, propionyl, benzoyl, nitrile, or nitro. [source]

    1,3-Diethynylallenes: Stable Monomers, Length-Defined Oligomers, Asymmetric Synthesis, and Optical Resolution

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2007
    Matthijs K. J. ter Wiel
    Abstract A series of differently substituted 1,3-diethynylallenes (DEAs) have been synthesized, confirming that the previously introduced construction protocols tolerate a variety of functional groups. The new DEAs bear at least one polar group to facilitate enantiomer separations on chiral stationary phases and to allow further functionalization. They are thermally and environmentally stable compounds since bulky substituents next to the cumulene moiety suppress the tendency to undergo [2+2] cyclodimerization. A series of length-defined oligomers were obtained as mixtures of stereoisomers by oxidative coupling of a monomeric DEA under Glaser,Hay conditions. The electronic absorption data indicate a lack of extended ,-electron conjugation across the oligomeric backbone due to the orthogonality of the allenic ,-systems. Remarkably, even complex mixtures of stereoisomers only yield one single set of NMR signals, which underlines the low stereodifferentiation in acyclic allenoacetylenic structures. Optical resolution of DEAs represents an amazing challenge, and preliminary results on the analytical level are reported. Asymmetric synthesis by Pd-mediated SN2,-type cross-coupling of an alkyne to an optically pure bispropargylic precursor opens another promising route to optically active allenes with stereoselectivities currently reaching up to 78,% ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Reaction mechanisms between methylamine and a few Schiff bases: Ab initio potential energy surfaces of a catalytic step in semicarbazide sensitive amino oxidases (SSAO)

    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2001
    Giuliano Alagona
    Abstract The potential energy surfaces for the transamination reaction catalyzed by SSAO were explored for some of the possible reactants considered in a preliminary investigation (Comput Chem 2000, 24, 311). The proton transfer to methylamine (as a model of the catalytic base belonging to the enzyme active site),either from the keto or enol form of the reactant Schiff bases with one of the possible cofactors, pyridoxal phosphate, PLP (using as a model the pyridoxal ring protonated at N),was investigated. The enol form seems to be preferred in the region of the neutral intermediate, because even the keto form undergoes a spontaneous rearrangement to the enol form once the C, proton is delivered to methylamine, producing methylammonium. When the proton is returned back to the Schiff base (on C1), the adduct is about 1.4 kcal/mol more stable than the reactants, while a canonical electron distribution is obtainable only for the enol form. The proton transfer to methylamine was also studied in the presence of the other possible cofactor (para or ortho) topaquinone, TQ. A steep uphill pathway, similar to the keto-pyridoxal Schiff base one, is obtained using the Schiff base with pTQ, which requires a rearrangement to the final intermediate. On the contrary, using the oTQ structures with the quinonoid O on the same side of methylamine, the proton abstracted from the Schiff base goes spontaneously onto the other quinonoid oxygen. The effect on the barrier heights produced by the presence of a variety of functional groups in the vicinity of the pyridoxal ring nitrogen was also examined. © 2001 John Wiley & Sons, Inc. Int J Quant Chem, 2001 [source]

    Nickel-Catalyzed Synthesis of Phosphonium Salts from Aryl Halides and Triphenylphosphine

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2008
    David Marcoux
    Abstract An efficient method to synthesize functionalized tetraarylphosphonium salts is described. The nickel-catalyzed coupling reaction between aryl iodides, bromides, chlorides, or triflates and triphenylphosphine generates tetraarylphosphonium salts in high yields. The coupling is wide in scope and tolerates a variety of functional groups such as alcohols, amides, ketones, aldehydes, phenols, phosphines and amines. [source]

    Palladium-Catalyzed Direct C-4 Arylation of 2,5-Disubstituted Furans with Aryl Bromides

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2008
    Aditya
    Abstract A simple and atom-economic procedure for the selective C-4 arylation of 2,5-disubstituted furans via CH bond activation using electron-deficient aryl bromides is reported. Only 0.5 mol% of the commercially available dimeric (allene)palladium chloride, [Pd(C3H5)Cl]2, was employed as catalyst. This environmentally attractive procedure has been found to be tolerant to a variety of functional groups on the aryl bromide such as carbonyl, nitrile, nitro, fluoro, ester or trifluoromethyl. [source]

    1H chemical shifts in NMR: Part 23,, the effect of dimethyl sulphoxide versus chloroform solvent on 1H chemical shifts

    MAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2006
    Raymond J. Abraham
    Abstract The 1H chemical shifts of 124 compounds containing a variety of functional groups have been recorded in CDCl3 and DMSO- d6 (henceforth DMSO) solvents. The 1H solvent shift ,, = ,(DMSO) , ,(CDCl3) varies from ,0.3 to +4.6 ppm. This solvent shift can be accurately predicted (rms error 0.05 ppm) using the charge model of ,, ,, , and long-range contributions. The labile protons of alcohols, acids, amines and amides give both, the largest solvent shifts and the largest errors. The contributions for the various groups are tabulated and it is shown that for H.C.C.X ,-effects (X = OH, NH, O, NH.CO) there is a dihedral angle dependence of the ,-effect. The group contributions are discussed in terms of the possible solvent,solute interactions. For protic hydrogens, hydrogen bonding is the dominant interaction, but for the remaining protons solvent anisotropy and electric field effects appear to be the major factors. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Applications of Multicomponent Reactions to the Synthesis of Diverse Heterocyclic Scaffolds

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2009
    James
    Abstract The sequencing of multicomponent reactions (MCRs) and subsequent cyclization reactions is a powerful stratagem for the rapid synthesis of diverse heterocyclic scaffolds. The optimal MCR is sufficiently flexible that it can be employed to generate adducts bearing a variety of functional groups that may then be selectively paired to enable different cyclization manifolds, thereby leading to a diverse collection of products. The growing interest in diversity-oriented synthesis has led to increased attention to this paradigm for library synthesis, which has inspired many advances in the design and implementation of MCRs for the construction of diverse heterocyclic scaffolds. [source]