Home About us Contact
|
Home About us Contact | ||
|
|
||
Addition Products (addition + products)
Selected AbstractsSynthesis and Characterization of a Series of New Luminescent NHC-Coordinated AuI,AgI Tetra- and Polymetallic Complexes Containing Benzoate-Bridged Ag2 DimersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2009Amit K. Ghosh Abstract The reaction of [Au(CH3impy)2]PF6 (2), with substituted silver benzoate salts bearing different halide substituents produced a series of new mixed-metal species having two different structural motifs. One structural motif contains discrete tetrametallic Ag2Au2 diamond cores, whereas the other motif contains the same tetrametallic diamond core interconnected by benzoate-bridged silver dimers to form polymers. All the complexes are substitution-inert and stable both in the solid state as well as in solution. We also report the synthesis of oxidative addition products of [Au(CH3impy)2]PF6, which were also obtained during our attempts to oxidize the above-mentioned multimetallic assembly with bromine and iodine. Compounds 3,7 are intensely luminescent in frozen acetonitrile solution, but surprisingly no luminescence is observed at room temperature. All the complexes were completely characterized by 1H, 13C NMR, electronic absorption, emission spectroscopy, elemental analysis and X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Diastereoselective Synthesis of Heteroaromatic Glycine DerivativesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2008Trygve Andreassen Abstract A TMSOTf promoted addition of an N - tert -butanesulfinyl ,-imino ester to five-membered aromatic heterocycles furnishes optically active heteroaromatic glycine derivatives with moderate-to-good yield in diastereomeric ratios up to 99,%. The absolute configuration of two of the addition products were solved by X-ray analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis and Stereochemical Aspects of 2,6-Disubstituted Perhydroazulenes , Core Units for a New Class of Liquid Crystalline MaterialsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2006Zakir Hussain Abstract A novel approach for the synthesis of cis/trans -fused perhydroazulenes 13,19 is reported. The stereochemistry of the derivatives of carbene addition products 9a,c/20,22, of the 2,6-disubstituted perhydroazulenes 12a,c/23,25, and that of compounds 26,27 has been studied by single-crystal X-ray crystallography. The hydrogenation of the tropylidene to the perhydroazulene skeleton under various conditions is described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Preparation and crystal structures of two 3-anthracenyl isoxazolyl sulfonamidesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2008Chun Li Lateral metalation and oxidation of 3-(9,-anthryl)-isoxazoles (1), using Davis' oxaziridine (6), produced the desired hydroxylation (2), along with sulfonamide adduct (3), and in the case of the use of butyl lithium as base, butyl addition products (4) and (5). Structures of isoxazole sulfonamides (3a) and (5a), were obtained as the SR/RS-diastereomer, however, studies indicate that this is a consequence of the crystallization process. Metalation studies with isoxazole (8) demonstrate that hydroxylation (9), can be carried out cleanly, minimizing formation of (10), using camphorsulfonyloxaziridine (7) as an electrophile. [source] Reaction of benzohydroximinoyl chlorides and ,-(trifluoromethyl)-acetylenic esters: Synthesis of regioisomeric (trifluoromethyl)-isoxazolecarboxylate esters and oxime addition productsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2003Bruce C. Hamper The triethylamine induced reaction of benzohydroximinoyl chlorides, precursors of nitrile oxides, with ,-trifluoromethylacetylenic esters gives rise to three products: 5-trifluoromethyl-4-isoxozolecarboxylate esters, regioisomeric 4-trifluoromethyl-5-isoxazolecarboxylate esters and an unexpected oxime 1,4-addition adduct. Product distribution is rationalized in terms of two competing reaction modes, either 1,4 addition of the oxime anion to the acetylenic ester or formation of the nitrile oxide followed by 1,3-dipolar cycloaddi-tion. Anionic 1,4-addition of the oximinoyl chloride to the acetylenic ester is preferred at low temperatures, while nitrile oxide formation followed by cycloaddition is preferred at temperatures above 0 °C. Regioisomeric products from addition of nitrile oxides to various perfluoroalkylacetylenes are compared and assigned by 13C NMR. [source] Thiol,ene coupling reaction of fatty acid monomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2004Johan Samuelsson Abstract The reactivities and reaction rates of the thiol,ene coupling reaction of 2-ethyl-(hydroxymethyl)-1,3-propanediol trimercapto acetate and 2-ethyl-(hydroxymethyl)-1,3-propanediol trimercapto propionate with two common unsaturated fatty acid methyl esters (methyl oleate and methyl linoleate) were evaluated. The reactions were monitored with real-time IR and 1H NMR, which both showed that the mercapto acetate was more reactive than the mercapto propionate. Both thiols were more prone to add to the monounsaturated methyl oleate than to methyl linoleate, which contained two unconjugated double bonds. According to bond energy calculations, the thiol hydrogen of mercapto acetate was somewhat more difficult to abstract than the hydrogen of mercapto propionate. Consequently, the formed SC bond in the acetate case was stronger than in the propionate case, and so the equilibrium was more shifted toward the addition products. The real-time IR measurements also showed that the cis unsaturation in methyl oleate isomerized much more quickly than that in methyl linoleate, and this also had an impact on the overall addition rate of the thiols because a trans unsaturation was more reactive than a cis unsaturation. The higher isomerization rates in the oleate systems, compared with those of the linoleate systems, was suggested to be due to a more restricted rotation along the CC bond of the reacted unsaturation in linoleate. This study showed the importance of trans unsaturations in obtaining reasonable reaction rates in thiol,ene reactions with fatty acid derivatives. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6346,6352, 2004 [source] Characterization of covalent addition products of chlorogenic acid quinone with amino acid derivatives in model systems and apple juice by high-performance liquid chromatography/electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2008Susanne Schilling High-performance liquid chromatography (HPLC) coupled to electrospray ionization tandem mass spectrometry (ESI-MSn) was used to study the covalent interactions between chlorogenic acid (CQA) quinone and two amino acid derivatives, tert -butyloxycarbonyl-L-lysine and N -acetyl-L-cysteine. In a model system at pH 7.0, the formation of covalent addition products was demonstrated for both derivatives. The addition product of CQA dimer and tert -butyloxycarbonyl-L-lysine was characterized by LC/MSn as a benzacridine structure. For N -acetyl-L-cysteine, mono- and diaddition products at the thiol group with CQA quinone were found. In apple juice at pH 3.6, covalent interactions of CQA quinone were observed only with N -acetyl-L-cysteine. Taking together these results and those reported by other groups it can be concluded that covalent interactions of amino side chains with phenolic compounds could contribute to the reduction of the allergenic potential of certain food proteins. Copyright © 2008 John Wiley & Sons, Ltd. [source] Asymmetric 1,4-Addition of Oxazolones to Nitroalkenes by Bifunctional Cinchona Alkaloid Thiourea Organocatalysts: Synthesis of ,,,-Disubstituted ,-Amino AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2008José Alemán Dr. Abstract An easy and simple synthetic approach to optically active ,,,-quaternary ,-amino acids using asymmetric organocatalysis is presented. The addition of oxazolones to nitroalkenes catalyzed by thiourea cinchona derivatives provides the corresponding ,,,-quaternary ,-amino acid derivatives with good yields, excellent diastereoselectivities (up to 98,% dr), and from moderate to good enantioselectivities (up to 92,% ee). The reaction can be performed on a large scale. The optically active oxazolone,nitroalkene addition products can be opened in a one-pot reaction to the corresponding ester,amide derivatives. Additional transformations are also presented, such as the synthesis of amino esters, amino acids, and transformation into 3,4-disubstituted pyrrolidin-2-ones. [source] Bifunctional-Thiourea-Catalyzed Diastereo- and Enantioselective Aza-Henry ReactionCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2006Xuenong Xu Dr. Abstract Bifunctional thiourea 1,a catalyzes aza-Henry reaction of nitroalkanes with N -Boc-imines to give syn -,-nitroamines with good to high diastereo- and enantioselectivity. Apart from the catalyst, the reaction requires no additional reagents such as a Lewis acid or a Lewis base. The N-protecting groups of the imines have a determining effect on the chirality of the products, that is, the reaction of N -Boc-imines gives R adducts as major products, whereas the same reaction of N -phosphonoylimines furnishes the corresponding S adducts. Various types of nitroalkanes bearing aryl, alcohol, ether, and ester groups can be used as nucleophiles, providing access to a wide range of useful chiral building blocks in good yield and high enantiomeric excess. Synthetic versatility of the addition products is demonstrated by the transformation to chiral piperidine derivatives such as CP-99,994. [source] Nickel-Catalyzed Mizoroki,Heck- versus Michael-Type Addition of Organoboronic Acids to ,,,-Unsaturated Alkenes through Fine-Tuning of LigandsCHEMISTRY - AN ASIAN JOURNAL, Issue 11 2007Pao-Shun Lin Abstract Various arylboronic acids reacted with activated alkenes in the presence of [Ni(dppe)Br2], ZnCl2, and H2O in CH3CN at 80,°C to give the corresponding Mizoroki,Heck-type addition products in good to excellent yields. Furthermore, 1,equivalent of the hydrogenation product of the activated alkene was also produced. By tuning the ligands of the nickel complexes and the reaction conditions, Michael-type addition was achieved in a very selective manner. Thus, various p- and o- substituted arylboronic acids or alkenylboronic acid reacted smoothly with activated alkenes in CH3CN at 80,°C for 12,h catalyzed by Ni(acac)2, P(o -anisyl)3, and K2CO3 to give the corresponding Michael-type addition products in excellent yields. However, for m- substituted arylboronic acids, the yields of Michael-type addition products are very low. The cause of this unusual meta -substitution effect is not clear. By altering the solvent or phosphine ligand, the product yields for m- substituted arylboronic acids were greatly improved. In contrast to previous results in the literature, the present catalytic reactions required water for Mizoroki,Heck-type products and dry reaction conditions for Michael-type addition products. Possible mechanistic pathways for both addition reactions are proposed. [source] Theoretical Study of the Reactions M++CH3F (M=Ge, As, Se, Sb)CHEMPHYSCHEM, Issue 9 2010Oscar Méndez Abstract CASSCF,MRMP2 calculations have been carried out to analyze the reactions of the methyl fluoride molecule with the atomic ions Ge+, As+, Se+ and Sb+. For these interactions, potential energy curves for the low-lying electronic states were calculated for different approaching modes of the fragments. Particularly, those channels leading to CH and CF oxidative addition products, H2FCMH+ and H3CMF+, respectively were explored, as well as the paths which evolve to the abstraction (MF++CH3) and the elimination (CH2M++HF) asymptotes. For the reaction Ge++CH3F the only favorable channel leads to fluorine abstraction by the ion. As+ and Sb+ can react with CH3F along pathways yielding stable addition products. However, a viable path joining the oxidative addition product H3CMF+ with the elimination asymptote CH2M++HF was found for the reaction of the fluorocarbon compound with As+. No favorable channels were detected for the interaction of fluoromethane with Se+. The results discussed herein allow rationalizing some of the experimental data found for these interactions through gas-phase mass spectrometry. [source] | ||||||||||||||||||||||