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    2-imidazoline and 1,4,5,6-tetrahydropyrimidine-ruthenium(II) complexes and catalytic synthesis of furan
    (Elsevier Science Sa, 1999) Çetinkaya, B; Alici, B; Özdemir, I; Bruneau, C; Dixneuf, PH
    The complexes RuCl2(L-1)(arene) (3-4) (L1 = HC=NCH2CH2NR, R = Et, arene = p-MeC6H4CHMe2 or C6Me6) and RuCl2(L-2)(arene) (5-6) (L-2 = HC=NCH2CH2CH2NR, R = Me; Ph, CH2Ph, p-MeC6H4) have been synthesized by reaction of [RuCl2(arene)](2), with 1-alkyl-2-imidazoline (1) or 1-alkyl-1,4,5,6-tetrahydropyrimidine (2). In each of these complexes (3-6) the ligand is bound via the imine (N=C) nitrogen atom. The new complexes are capable of catalyzing the activation of (2)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran in very good yield, via intramolecular cyclization, and the 1,4,5,6-tetrahydropyrimidine complexes 5 and 6 appeared to be the best catalyst precursors. Cyclic voltammetry shows that the nature of the arene ligand, rather than that of the nitrogen containing ligand, controls the electron-richness of the complexes. (C) 1999 Elsevier Science Ss.A. All rights reserved.
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    ?6-mesityl,?1-imidazolinylidene-carbene-ruthenium(II) complexes
    (Wiley-V C H Verlag Gmbh, 2003) Çetinkaya, B; Demir, S; Özdemir, I; Toupet, L; Sémeril, D; Bruneau, C; Dixneuf, PH
    The reaction of electron-rich carbene-precursor olefins containing two imidazolinylidene moieties [(2,4,6-Me3C6H2CH2)NCH2CH2N(R)C=](2) (2a: R = CH2CH2OMe, 2b R = CH(2)Mes), bearing at least one 2,4,6-trimethylbenzyl (R = CH(2)Mes) group on the nitrogen atom, with [RuCl2(arene)](2) (arene = p-cymene, hexamethylbenzene) selectively leads to two types of complexes. The cleavage of the chloride bridges occurs first to yield the expected (carbene) (arene)ruthenium(H) complex 3. Then a further arene displacement reaction takes place to give the chelated eta(6)-mesityl,eta'-carbene-ruthenium complexes 4 and 5. An analogous eta(6)-arene-eta(1)-carbene complex with a benzimidazole frame 6 was isolated from an in situ reaction between [RuCl2(p-cymene)](2), the corresponding benzimidazolium salt and cesium carbonate. On heating, the RuCl2(imidazolinylidene) (p-cymene) complex 8, with p-methoxybenzyl pendent groups attached to the N atoms, leads to intramolecular p-cymene displacement and to the chelated eta(6)-arene,eta(1)-carbene complex 9. On reaction with AgOTf and the propargylic alcohol HC=CCPh20H, compounds 4-6 were transformed into the corresponding ruthenium allenylidene intermediates (4-->10, 5-->11, 6-->12). The in situ generated intermediates 10-12 were found to be active and selective catalysts for ring-closing metathesis (RCM) or cycloisomerisation reactions depending on the nature of the 1,6-dienes. Two complexes [RuCl2-{eta(1)-CN(CH2C6H2Me3-2,4,6)CH2CH2N- (CH2CH2OMe)}(C6Me6)] 3 with a monodentate carbene ligand and [RuCl2-{eta(1)-CN[CH2(eta(6)-C6H2Me3-2,4,6)]CH2CH2N-(CH2C6H2Me3-2,4,6)}] 5 with a chelating carbene-arene ligand were characterised by X-ray crystallography.
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    Access to 3-methyl-4-methylene-N-tosylpyrrolidine and 3,4-dimethyl-N-tosylpyrroline by ruthenium-catalyzed cascade cycloisomerization/isomerization reactions
    (Wiley-V C H Verlag Gmbh, 2004) Özdemir, I; Çetinkaya, E; Çetinkaya, B; Çicek, M; Sémeril, D; Bruneau, C; Dixneuf, PH
    New RuCl2(benzimidazole)(arene) complexes have been prepared. Upon reaction with 1,1-diphenylprop-2-ynol they generate catalyst precursors which perform the cycloisomerization of diallyltosylamide into 3-methyl-4-methylene-N-tosylpyrrolidine. The presence of N-(2,4,6-trimethyl-benzyl)benzimidazole as ligand leads to a subsequent isomerization and gives the 3,4-dimethyl-N-tosylpyrroline. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
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    Benzimidazole, benzothiazole and benzoxazole ruthenium(II) complexes;: Catalytic synthesis of 2,3-dimethylfuran
    (Wiley-V C H Verlag Gmbh, 2000) Çetinkaya, B; Özdemir, I; Bruneau, C; Dixneuf, PH
    Fourteen ruthenium(II) complexes of the type [RuCl2(eta(6)-arene)L], (arene = 1,4-MeC6H4Pri or C6Me6; L = benzimidazole derivative in which the NH group is substituted by N-alkyl or isoelectronic O or S atoms) have been prepared by cleavage of [RuCl2(eta(6)-arene)](2) with the N-heterocycle L. Their spectroscopic and electrochemical properties are described. The effect of the nature of the benzazole (L) on the catalytic activity of these complexes for the intramolecular cyclization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran has also been studied; the benzimidazole complexes were found to be the most active.
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    First ruthenium complexes with a chelating arene carbene ligand as catalytic precursors for alkene metathesis and cycloisomerisation
    (Royal Soc Chemistry, 2001) Çetinkaya, B; Demir, S; Özdemir, I; Toupet, L; Sémeril, D; Bruneau, C; Dixneuf, PH
    Electron-rich carbene precursors 2 and 3, containing the imidazolidin-2-ylidene moiety with one (2) and two (3) pendent N-(2,4,6-trimethylbenzyl) groups, on reaction with [RuCl2(arene)](2) lead to ruthenium(II) complexes 5 and 6 containing the chelating 8-electron mixed arene-carbene ligand; the X-ray diffraction crystal structure of RuCl2{eta (1)- CN[CH2(eta (6)-2,4,6-Me3C6H2)]CH2CH2N(CH2CH2OMe)} 6, was established. These complexes are precursors of the unstable ruthenium-allenylidene intermediates 7 and 8, but are active catalysts either for selective catalytic alkene metathesis or cycloisomerization, depending on the nature of the 1,6-diene.
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    Regioselective allylic alkylation and etherification catalyzed by in situ generated N-heterocyclic carbene ruthenium complexes
    (Pergamon-Elsevier Science Ltd, 2006) Gürbüz, N; Özdemir, I; Çetinkaya, B; Renaud, JL; Demerseman, B; Bruneau, C
    Benzimidazolium halides are used for the first time as ligand precursors in ruthenium-catalyzed substitution of allylic carbonates and chlorides by carbon nucleophiles and phenols, respectively. After generation of diaminocarbene species upon deprotonation by tBuOK, their association with [Cp*Ru(MeCN)(3)]PF6 induces a very high regioselectivity in favor of the branched isomers when cinnamyl derivatives are used as starting substrates. They also provide good regioselectivities for the allylation of phenols by unsymmetrical aliphatic allylic substrates such as 3-chloro-4-phenylbut-1-ene, and thus provide a straightforward access to new allylic phenyl ethers. (c) 2005 Elsevier Ltd. All rights reserved.
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    Ruthenium-carbene catalysts for the synthesis of 2,3-dimethylfuran
    (Elsevier Science Bv, 1997) Cetinkaya, B; Ozdemir, I; Bruneau, C; Dixneuf, PH
    A variety of neutral arene-ruthenium-carbenes of type (arene)RuCl2(=C(NR)CH(2)CH(2)NR) have been used for the catalytic transformation of (Z)-3-methylpent-2-en-4-yn-l-ol into 2,3-dimethylfuran. The catalytic reaction takes place at 80 degrees C with mononuclear complexes III-V to afford the furan in similar to 90% yield. The binuclear catalysts VIa and VIIa having a linked bis-carbene bridge operate at room temperature to initiate an exothermic reaction offering 90-97% of furan.