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Coupling Products (coupling + products)
Selected AbstractsSynthesis and Structure Elucidation of Oxidative Coupling Products of 2-Hydroxy-1,4-naphthoquinones.CHEMINFORM, Issue 46 2006A. Ya. Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Silylene/Oxazolidinone Double-Locked Sialic Acid Building Blocks for Efficient Sialylation Reactions in DichloromethaneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Shinya Hanashima Abstract We describe efficient sialylation reactions in CH2Cl2 with the use of silylene/oxazolidinone double-locked sialic acid building blocks. The building blocks were synthesized from 4,5-oxazolidinone-protected phenylthiosialoside. In sialylation reactions towards primary and relatively reactive secondary hydroxy groups on the galactosides, the double-locked building blocks provided desired coupling products in good yields with excellent ,-selectivities. In the sialylation reaction with the C3-OH of the galactoside, the double-locked building blocks expressed significantly better ,-selectivity in comparison with the results obtained by using the oxazolidinone-locked building block. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] The Use of a Bifunctional Copper Catalyst in the Cross-Coupling Reactions of Aryl and Heteroaryl Halides with Terminal AlkynesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2008Minyan Wu Abstract Copper-catalyzed cross-coupling reactions of aryl halides and heteroaryl halides with terminal alkynes were carried out in DMF at 110,130 °C to provide the corresponding coupling products in satisfactory-to-good yields by using inexpensive 8-hydoxyquinoline as the ligand. Noteworthy is that the bifunctional copper catalyst was successfully applied in this alkynylation reaction for the first time.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Formation of Pyridazinium Salts by Azo Coupling of N -Substituted 3-Amino-1-phenylbut-2-en-1-ones and Diazonium SaltsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2004Abstract Treatment of 3-(2,4-dimethoxyphenylamino)- and 3-methylamino-1-phenylbut-2-en-1-ones with some benzenediazonium tetrafluoroborates gives, besides the usual azo coupling products [i.e., 3-(substituted imino)-1-phenylbutane-1,2-diones 2-(4-substituted phenylhydrazones) and 2-(4-methoxyphenyldiazenyl)-3-methylamino-1-phenylbut-2-en-1-one, respectively], the previously unreported 1,4,5,6-tetrasubstituted pyridazinium tetrafluoroborates. The pyridazinium salts have been identified by X-ray analysis and by their 1H, 13C, 15N, 11B and 19F NMR spectra. Their formation is most probably the result of nucleophilic attack on the carbonyl carbon by the nitrogen of the hydrazone group and subsequent dehydration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A Mild and Efficient Method for N -Arylnucleobase Synthesis via the Cross-Coupling Reactions of Nucleobases with Arylboronic Acids Catalyzed by Simple Copper SaltsHELVETICA CHIMICA ACTA, Issue 6 2008Lan Tao Abstract A simple and efficient copper-salt catalyzed N -arylation of nucleobases is reported. In a mixed solvent of MeOH and H2O, the coupling products were obtained in moderate to excellent yields at room temperature within a short time. A variety of substituted N -aryl nucleobases can be prepared through this procedure. [source] Extremely Efficient Cross-Coupling of Benzylic Halides with Aryltitanium Tris(isopropoxide) Catalyzed by Low Loadings of a Simple Palladium(II) Acetate/Tris(p -tolyl)phosphine SystemADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Chi-Ren Chen Abstract Highly efficient coupling reactions of benzylic bromides or chlorides with aryltitanium tris(isopropoxide) [ArTi(O- i- Pr)3] catalyzed by a simple palladium(II) acetate/tris(p -tolyl)phosphine [Pd(OAc)2/ P(p -tolyl)3] system are reported. The coupling reactions proceed in general at room temperature employing low catalyst loadings of 0.02 to 0.2,mol%, affording coupling products in excellent yields of up to 99%. For benzylic bromides bearing strong electron-withdrawing cyano (CN) or trifluoromethyl (CF3) substituents, the reactions require a higher catalyst loading of 1,mol%, or the reactions are carried out at 60,°C. The catalytic system also tolerates (1-bromoethyl)benzene bearing ,-hydrogen atoms while using a catalyst loading of 1,mol% to afford the coupling product in a 70% yield. [source] Samarium Powder-Catalyzed Palladium-Free and Ligand-Free Sonogashira Coupling ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Jincheng Mao Abstract A study of samarium powder-catalyzed cross-coupling reactions of aryl halides with terminal alkynes is described. The couplings performed in the polyethylene glycol PEG-600 provided the corresponding coupling products in good yields. The first example of palladium-free, copper-free and amine-free catalytic system for Sonogashira couplings is presented in the absence of ligand. [source] Palladium-Catalyzed Three-Component 1:2:1 Coupling of Aryl Iodides, Alkynes, and Alkenes to Produce 1,3,5-Hexatriene DerivativesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Hakaru Horiguchi Abstract The intermolecular three-component coupling of aryl iodides, diarylacetylenes, and alkenes effectively proceeds in the presence of palladium acetylacetonate and silver acetate as catalyst and base, respectively, to give the corresponding 1:2:1 coupling products, 1,3,5-hexatriene derivatives. A further homologation of the oligoene chain of the three-component coupling products by a simple procedure is also presented. [source] Copper-Mediated Aryl-Aryl Couplings for the Construction of Oligophenylenes and Related HeteroaromaticsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Masahiko Iyoda Abstract Efficient methods for the syntheses of biaryls by the copper-mediated homocoupling of arylmetals are summarized. First, a smooth transmetallation between arylzinc halides and copper(II) salts has been employed for the selective homocoupling of arylzinc halides to produce either biphenylenes or tetraphenylenes. This reaction has been applied to the synthesis of cyclic oligothiophenes. Second, an efficient method for the homocoupling of aryl halides by the electron-transfer (ET) oxidation of Lipshutz cuprates [Ar2Cu(CN)Li2] with organic electron acceptors has been developed. The ET oxidation of cuprates with 1,4-benzoquinones proceeds smoothly to afford the corresponding coupling products in moderate to high yields. The ET oxidation of cuprates has been applied to the synthesis of either thiophene- or benzene-fused 10-membered ring cyclophanes. For the synthesis of macrocyclic cyclophanes, a linear CCuC structure of Lipshutz cuprates should be maintained in the dimetallacyclic intermediates to efficiently produce large-ring cyclophanes. Moreover, nonaphenylenes and dodecaphenylenes have been synthesized using the ET oxidation of cuprates with duroquinone. Interestingly, hexadodecyloxynonaphenylene exhibits different nanostructures between fibrous materials in solution and cast films on a surface. Films of this compound can detect vaporized nitroaromatics such as dinitrobenzene and trinitrobenzene. [source] Photoreaction Between Benzoylthiophenes and N -BOC-Tryptophan Methyl Ester,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2006Julia Pérez-Prieto ABSTRACT Drug-induced photoallergy requires as the first step formation of covalent drug-protein photoadducts. One of the key amino acids involved in this process is tryptophan (Trp). In this context, several diaryl ketones, including 2-benzoylthiophene (BT), [2-(5-benzoyl-5-thienyl)]-2-methylpropanoic methyl ester (TPA methyl ester) and 4-(2-thienylcarbonyl)phenyl]-2-methylpropanoic methyl ester (SUP methyl ester) have been irradiated in the presence of N -BOC-(L)-tryptophan methyl ester. Laser flash photolysis has allowed to detect three neutral radicals (ketyl, indolyl and skatolyl radicals) resulting from formal hydrogen-atom abstraction. This correlates well with the isolation of homodimers, as well as with cross-coupling products, in the preparative irradiation. The main cross-coupling products were in all cases lactones arising from the reaction of the Trp-derived skatolyl radicals with the corresponding ketyl radicals. These lactones were obtained as the (4R) stereoisomers with remarkable diasteroselectivity. No coupling products through the phenyl p -position of BT or TPA methyl ester were found. By contrast, ketone homodimers and cross-coupling products arising from reaction through the thienyl 5-position were obtained when using BT and SUP methyl ester; this is very interesting, because stable LAT-derived products are difficult to isolate. [source] Accelerated Heck reaction using ortho -palladated complex with controlled microwave heatingAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2009Abdol R. Hajipour Abstract Palladium-catalyzed Heck couplings utilizing [Pd{C6H2(CH2CH2NH2)-(OMe)2,3,4} (µ-Br)]2 palladacycle catalyst and microwave irradiation lead to formation of different coupling products. This complex is an active and efficient catalyst for the Heck reaction of aryl iodides, bromides and even less reactive chlorides. The cross-coupled products were produced in excellent yields. The reaction time was reduced from hours to minutes and full conversion was achieved under microwave irradiation. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis and catalytic activity of novel xylyl-linked benzimidazolium saltsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2009Serpil Demir Abstract The reaction of 1-alkylbenzimidazole derivatives with o -/p -di(chloromethyl)benzene results in the formation of the new o -/p -xylyl-linked bis(benzimidazolium) salts, 1 and 2, respectively. The salts were characterized by NMR spectroscopy and elemental analysis. The in situ prepared complexes derived from Pd(OAc)2,1 and 2 exhibit catalytic activity (61,98%), to give the Heck coupling products of aryl bromides and styrene. Copyright © 2009 John Wiley & Sons, Ltd. [source] Dichloro-Bis(aminophosphine) Complexes of Palladium: Highly Convenient, Reliable and Extremely Active Suzuki,Miyaura Catalysts with Excellent Functional Group ToleranceCHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2010Jeanne Abstract Dichloro-bis(aminophosphine) complexes are stable depot forms of palladium nanoparticles and have proved to be excellent Suzuki,Miyaura catalysts. Simple modifications of the ligand (and/or the addition of water to the reaction mixture) have allowed their formation to be controlled. Dichlorobis[1-(dicyclohexylphosphanyl)piperidine]palladium (3), the most active catalyst of the investigated systems, is a highly convenient, reliable, and extremely active Suzuki catalyst with excellent functional group tolerance that enables the quantitative coupling of a wide variety of activated, nonactivated, and deactivated and/or sterically hindered functionalized and heterocyclic aryl and benzyl bromides with only a slight excess (1.1,1.2,equiv) of arylboronic acid at 80,°C in the presence of 0.2,mol,% of the catalyst in technical grade toluene in flasks open to the air. Conversions of >95,% were generally achieved within only a few minutes. The reaction protocol presented herein is universally applicable. Side-products have only rarely been detected. The catalytic activities of the aminophosphine-based systems were found to be dramatically improved compared with their phosphine analogue as a result of significantly faster palladium nanoparticle formation. The decomposition products of the catalysts are dicyclohexylphosphinate, cyclohexylphosphonate, and phosphate, which can easily be separated from the coupling products, a great advantage when compared with non-water-soluble phosphine-based systems. [source] Can Weakly Coordinating Anions Stabilize Mercury in Its Oxidation State +IV?CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2005Sebastian Riedel Dipl.-Chem. Abstract While the thermochemical stability of gas-phase HgF4 against F2 elimination was predicted by accurate quantum chemical calculations more than a decade ago, experimental verification of "truly transition-metal" mercury(IV) chemistry is still lacking. This work uses detailed density functional calculations to explore alternative species that might provide access to condensed-phase HgIV chemistry. The structures and thermochemical stabilities of complexes HgIVX4 and HgIVF2X2 (X,=AlF4,, Al2F7,, AsF6,, SbF6,, As2F11,, Sb2F11,, OSeF5,, OTeF5,) have been assessed and are compared with each other, with smaller gas-phase HgX4 complexes, and with known related noble gas compounds. Most species eliminate F2 exothermically, with energies ranging from only about ,60 kJ,mol,1 to appreciable ,180 kJ,mol,1. The lower stability of these species compared to gas-phase HgF4 is due to relatively high coordination numbers of six in the resulting HgII complexes that stabilize the elimination products. Complexes with AsF6 ligands appear more promising than their SbF6 analogues, due to differential aggregation effects in the HgII and HgIV states. HgF2X2 complexes with X,=OSeF5, or OTeF5, exhibit endothermic fluorine elimination and relatively weak interactions in the HgII products. However, elimination of the peroxidic (OEF5)2 coupling products of these ligands provides an alternative exothermic elimination pathway with energies between ,120 and ,130 kJ,mol,1. While all of the complexes investigated here thus have one exothermic decomposition channel, there is indirect evidence that the reactions should exhibit nonnegligible activation barriers. A number of possible synthetic pathways towards the most interesting condensed-phase HgIV target complexes are proposed. [source] Highly Efficient Pd/C-Catalyzed Suzuki Coupling Reaction of p -(un)Substituted Phenyl Halide with (p -Substituted phenyl) Boronic AcidCHINESE JOURNAL OF CHEMISTRY, Issue 8 2007Ming-Gang Hu Abstract A highly efficient Pd/C-catalyzed ligandless, heterogeneous Suzuki reaction of p -(un)substituted phenyl halide with (p -substituted phenyl)boronic acid in DMF/H2O solvent in a short reaction time (0.5 h) at 75 °C was developed. The key for such a catalytic system was the addition of 1 equivalent of tetrabutylammonium bromide. A wide variety of substituents can be tolerated and high yields of cross coupling products were achieved. The palladium catalyst can be easily recovered and reused without significantly decreasing its efficiency. [source] | ||||||||||||||||||||||