共查询到20条相似文献,搜索用时 15 毫秒
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Yamamoto Y Kinpara K Ogawa R Nishiyama H Itoh K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(21):5618-5631
In the presence of a catalytic amount of [Cp*RuCl(cod)] (Cp*=pentamethylcyclopentadienyl, cod=1,5-cyclooctadiene), 1,6-diynes were allowed to react chemo- and regioselectively with nitriles bearing a coordinating group, such as dicyanides or alpha-halonitriles, at ambient temperature to afford bicyclic pyridines. Careful screening of nitrile components revealed that a C[triple chemical bond]C triple bond or heteroatom substituents, such as methoxy and methylthio groups, proved to act as the coordinating groups, whereas C==C or C==O double bonds and amino groups failed to promote cycloaddition. This suggests that coordinating groups with multiple pi-bonds or lone pairs are essential for the nitrile components. 相似文献
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Palladium and gold-palladium catalysts for the direct synthesis of hydrogen peroxide 总被引:1,自引:0,他引:1
Today hydrogen peroxide is produced by an indirect process in which an alkyl anthraquinone is sequentially hydrogenated and oxidized. In this way hydrogen and oxygen are kept separate during the manufacturing process. A process where molecular oxygen is directly hydrogenated could be preferred if control of the sequential hydrogenation can be achieved, particularly if high rates can be attained under intrinsically safe, non-explosive conditions. Herein we describe recent progress in the direct synthesis of hydrogen peroxide using supported palladium and gold-palladium alloy catalysts and consider some of the problems that have to be overcome. 相似文献
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Yang L Mayr M Wurst K Buchmeiser MR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(22):5761-5770
The synthesis of novel ruthenium-based metathesis catalysts containing the saturated 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene ligand, that is, [RuCl2(NHC)[=CH-2-(2-PrO)-5-NO(2)-C6H3]] (1) and [Ru(CF3COO)2(NHC)[=CH-2-(2-PrO)-5-NO2-C6H3]] (2) (NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) is described. Both catalysts are highly active in ring-closing metathesis (RCM) and ring-opening cross-metathesis (ROCM). Compound 1 shows moderate activity in enyne metathesis. Compound 2 is not applicable to enyne metathesis since it shows high activity in the cyclopolymerization of diethyl dipropargylmalonate (DEDPM). Poly(DEDPM) prepared by the action of 2 consists of 95% five-membered rings, that is, poly(cyclopent-1-enevinylene)s, and 5 % of six-membered rings, that is, poly(cyclohex-1-ene-3-methylidene)s. The polymerization proceeds in a nonliving manner and results in polyenes with broad polydispersities (1.9< or =PDI< or =2.3). Supported analogues of 2 were prepared by immobilization on hydroxymethyl-Merrifield resin and a monolithic support derived from ring-opening-metathesis polymerization (ROMP). Catalyst loadings of 1 and 2.5%, respectively, were obtained. Both supported versions of 2 showed excellent reactivity. With 0.24-2% of the supported catalysts, yields in RCM and ROCM were in the range of 76-100%. Leaching of ruthenium was low and resulted in Ru contaminations of the products of less than 0.000014% (0.14 ppm). 相似文献
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Ken Motokura 《Tetrahedron letters》2005,46(33):5507-5510
α-Alkylation of various nitriles with carbonyl compounds successfully proceeded using a hydrotalcite-supported palladium nanoparticle as a multifunctional catalyst. The alkylated nitriles were formed through aldol reaction at base sites on the hydrotalcite surface followed by hydrogenation by molecular hydrogen on the palladium nanoparticle. 相似文献
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