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Organometallic Reagents (organometallic + reagent)
Selected AbstractsSynthesis and anti-HIV-1 activity of 1,3-phenylene bis-uracil analogues of MKC-442JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2007Youssef L. Aly Reaction of 1,3-phenylenediacetonitrile with the zinc organometallic reagent of ethyl 2-bromobutyrate afforded the 1,3-phenylene-bis(acetoacetate) 2 which was used as the starting material for the synthesis of 1,3-phenylene-bis[6-(2-thiouracil)] 4. Desulphurization of 4 gave the corresponding bis-uracil 6, which after silylation was N-1 alkylated with bis(allyoxy)methane using TMS-triflate as the catalyst or with chloromethyl ethyl ether to give the MKC-442 analogues 7 and 9. The amino-DABO and S-DABO derivatives 11, 12a,b and 14 were also synthesized. The anti-HIV-1 activity test showed that when MKC-442 analogues were constructed with 1,3-phenylene in all cases they were detrimental to have activity against HIV-1. [source] Diphenyldipyridinezinc(II): partial spontaneous resolution of an organometallic reagentACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Anders Lennartson The title compound, [Zn(C6H5)2(C5H5N)2], (I), forms conformationally chiral molecules residing on a twofold axis. The molecules are stacked along c, and these stacks are associated by edge-to-face ,,, interactions. Crystals of (I) belong to the Sohncke space group P21212 and the crystal lattice of (I) is chiral. The crystal batch that was examined consisted of a mixture of enantiomerically pure crystals and crystals twinned by inversion. [source] Highly Stereoselective Metal-Mediated Entry to Functionalized Tetrahydrothiophenes by Barbier-Type Carbonyl-Addition ReactionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2008Benito Alcaide Abstract Reactions of tetrahydrothiophene-3-carbaldehydes with stabilized organometallic reagents were investigated in aqueous media. Tetrahydrothiophene-3-carbaldehydes and a variety of stabilized organic halides undergo stereocontrolled coupling under Barbier-type conditions in the presence of different metals (zinc, tin, indium) and additives [ammonium chloride, hydrobromic acid, hafnium(IV) chloride, bismuth(III) chloride]. The regiochemistry of the carbonyl addition processes, when applicable, was excellent.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis of Polyfluorinated Nitrogen-Containing Heterocycles from Hemifluorinated Enones or Organofluorosilicon Building Blocks as Synthetic EquivalentsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2004Frédéric Chanteau Abstract A series of polyfluorinated heterocycles has been prepared by heterocyclisation of hemifluorinated enones or organofluorosilicon synthetic equivalents with different bis(nucleophiles). These polyfluorinated building blocks were obtained by treatment of acylsilanes with perfluoro organometallic reagents. The method is general and has been applied to aliphatic, aromatic and carbohydrate derivatives, to give oxazolidines, imidazolidines, benzodia- and -thiazepines, quinolines and pyrimidines bearing both a fluorine atom and a perfluoroalkyl group in vicinal positions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Copper-Catalyzed Asymmetric Allylic Alkylation of Racemic Cyclic Substrates: Application of Dynamic Kinetic Asymmetric Transformation (DYKAT)ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Jean-Baptiste Langlois Abstract The copper-catalyzed asymmetric allylic alkylation (AAA) is of great interest in organic synthesis. This reaction was extensively studied using a broad range of substrates, ligands and organometallic reagents. However, the use of racemic substrates was still limited. Although some processes of kinetic resolution are reported in the literature, no examples of quantitative deracemization are described as is the case for the Pd-catalyzed allylic alkylation. We present here a full account of our investigations through the development of the first example of such a process in copper-catalyzed AAA. High enantioselectivities (up to 99% ee), scope of the reaction and mechanistic considerations are reported herein. [source] The synthesis of CdSe quantum dots with carboxyl group and study on their optical characteristicsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2009Chen Ye Abstract Quantum dots are nanocrystal semiconductors which attract lots of research interests due to their peculiar optical properties. CdSe/ZnS quantum dots have been synthesized via pyrolysis of organometallic reagents. The color of the quantum dot changes from yellow-green to red as their size increases with reaction time. Photoluminescence quantum efficiency of CdSe quantum dots have been enhanced by passivating the surface of CdSe quantum dots with ZnS layers. Quantum dots are nanocrystal semiconductors which attract lots of research interests due to their peculiar optical properties. CdSe/ZnS quantum dots have been synthesized via pyrolysis of organometallic reagents. The color of the quantum dot changes from yellow-green to red as their size increases with reaction time. Photoluminescence quantum efficiency of CdSe quantum dots have been enhanced by passivating the surface of CdSe quantum dots with ZnS layers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Identification of a Highly Efficient Alkylated Pincer Thioimido,Palladium(II) Complex as the Active Catalyst in Negishi CouplingCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2009Jing Liu Dr. Abstract PdIIate complex: A novel alkylated pincer thioimido,Pd complex generated from a catalyst precursor and basic organometallic reagents (RM) was observed by in situ IR, 1H,NMR, and 13C,NMR spectroscopies for the first time and proved to be the active catalyst in stoichiometric and catalytic reactions of aryl iodides with RM (see scheme). The catalyst, as an electron-rich PdII species, promoted the Negishi coupling of aryl iodides and alkylzinc reagents with high efficiency, even at low temperatures (0 or ,20,°C). The induction period of Negishi coupling catalyzed by pincer thioamide,palladium complex 1 was investigated. A heterogeneous mechanism was excluded by kinetic studies and comparison with Negishi coupling reactions promoted by Pd(OAc)2/Bu4NBr (a palladium,nanoparticle system). Tetramer 2 was isolated from the reaction of 1 and organozinc reagents. Dissociation of complex 2 by PPh3 was achieved, and the structure of resultant complex 8 was confirmed by X-ray diffraction analysis. A novel alkylated pincer thioimido,PdII complex, 7, generated from catalyst precursor 1 and basic organometallic reagents (RM), was observed by in situ IR, 1H,NMR, and 13C,NMR spectroscopy for the first time. The reaction of 7 with methyl 2-iodobenzoate afforded 74,% of the cross-coupled product, methyl 2-methylbenzoate, together with 60,% of PdII complex 2. Furthermore, the catalyst, as an electron-rich PdII species, efficiently promoted the Negishi coupling of aryl iodides and alkylzinc reagents without an induction period, even at low temperatures (0,°C or ,20,°C). To evaluate the influence of the catalyst structure upon the induction period, complex 9 was prepared, in which the nBu groups of 1 were displaced by more bulky 1,3,5-trimethylphenyl groups. Trimer 10 was isolated from the reaction of complex 9 and basic organometallic reagents such as CyZnCl or CyMgCl (Cy: cyclohexyl); this is consistent with the result obtained with complex 1. The rate in the induction period of the model reaction catalyzed by 9 was faster than that with 1. Plausible catalytic cycles for the reaction, based upon the experimental results, are discussed. [source] | ||||||||||