- Spirobifluorene-based Porous Organic Polymers as Efficient Porous Supports for Pd and Pt for Selective Hydrogenation
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Spirobifluorene-based porous organic polymers (POP) were synthesized following two different protocols; the acetylenic coupling reaction conditions and the Sonogashira cross-coupling reaction. These were utilized as support for the hydrogenation of a series of species containing unsaturated C=C and C=O bonds (4-nitrostyrene, 4-bromobenzophenone, acetophenone, 7-nitro-1-tetralone and 1,2-naphtoquinone confirmed their efficiency). POP1 prepared via a copper-catalysis protocol was completely inactive, while POP2-4 containing residual Pd exhibited different activities in accordance to the accessibility of the substrates to the metal. Further deposition of 0.5 wt% Pd led to active and stable catalysts. They were easily separated by filtration, and after re-dispersion, afforded the same performances for ten successive cycles. This study also evidenced the specific role of the support in these reactions by comparing the behavior of Pd/POP with that of a Pd/C catalyst with the same loading of palladium. The deposition of Pt on these supports led to sub-nanometric particles and, in accordance, to a different catalytic behavior reflected merely by differences in the selectivity.
- Trandafir, Mihaela Mirela,Pop, Lidia,H?dade, Niculina D.,Hristea, Ioana,Teodorescu, Cristian Mihail,Krumeich, Frank,van Bokhoven, Jeroen A.,Grosu, Ion,Parvulescu, Vasile I.
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p. 538 - 549
(2018/10/09)
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- Rhodium(I)-catalyzed domino asymmetric ring opening/enantioselective isomerization of oxabicyclic alkenes with water
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Water-induced asymmetric ring opening: Enantio-enriched 2-hydroxy-1-tetralones are formed from oxabicyclic alkenes through a novel RhI-catalyzed domino reaction. The proposed mechanism involves water-induced asymmetric ring opening to generate chiral trans-1,2-diol intermediates and subsequent enantioselective isomerization (see scheme). Copyright
- Tsui, Gavin C.,Lautens, Mark
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supporting information; experimental part
p. 5400 - 5404
(2012/07/03)
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- Hyperaromatic stabilization of arenium ions
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Benzene-cis- and trans-1,2-dihydrodiols undergo acid-catalyzed dehydration at remarkably different rates: kcis/ktrans = 4500. This is explained by formation of a β-hydroxycarbocation intermediate in different initial conformations, one of which is stabilized by hyperconjugation amplified by an aromatic no-bond resonance structure (HOC6H6 + HOC6H5 H+). MP2 calculations and an unfavorable effect of benzoannelation on benzenium ion stability, implied by pKR measurements of -2.3, -8.0, and -11.9 for benzenium, 1-naphthalenium, and 9-phenanthrenium ions, respectively, support the explanation.
- Kudavalli, Jaya S.,Boyd, Derek R.,Coyne, Dara,Keeffe, James R.,Lawlor, David A.,MacCormac, Aoife C.,More O'Ferrall, Rory A.,Rao, S. Nagaraja,Sharma, Narain D.
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supporting information; experimental part
p. 5550 - 5553
(2011/02/27)
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- Bio-inspired arene cis-dihydroxylation by a non-haem iron catalyst modeling the action of naphthalene dioxygenase
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Reported in this paper is the first example of a biomimetic iron complex, ([FeII(TPA)(NCMe)2]2+ (TPA = tris(2-pyridylmethyl)amine), that catalyses the cis-dihydroxylation of an aromatic double bond, mimicking the action of
- Feng, Yan,Ke, Chun-Yen,Xue, Genqiang,Que Jr., Lawrence
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body text
p. 50 - 52
(2009/03/11)
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- Biotransformation of phenanthrene and 1-methoxynaphthalene with Streptomyces lividans cells expressing a marine bacterial phenanthrene dioxygenase gene cluster.
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The phdABCD gene cluster in a marine bacterium Nocardioides sp. strain KP7 codes for the multicomponent enzyme phenanthrene dioxygenase. phdA encoding an iron-sulfur protein large subunit alpha, phdB encoding its small subunit beta, phdC encoding ferredoxin, and phdD encoding ferredoxin reductase, were replaced in such a way that the termination codons of the preceding open reading frames were overlapped with the initiation codons of the following genes. This manipulated phdABCD gene cluster was positioned downstream of the thiostrepton-inducible promoter PtipA in a high-copy-number vector pIJ6021, and introduced into the gram-positive, soil-inhabiting, filamentous bacterium Streptomyces lividans. The recombinant S. lividans cells converted phenanthrene into a cis-diol form, which was determined to be cis-3,4-dihydroxy-3,4-dihydrophenanthrene by its UV spectral data as well as HPLC property, using the authentic sample for comparison. This biotransformation proceeded very efficiently; 200 microM and 2 mm of phenanthrene were almost completely converted to its cis-diol form in 6 h and 32 h, respectively. In addition, the S. lividans cells carrying the phdABCD gene cluster were found to transform 1-methoxynaphthalene to two products, which were identified to be 8-methoxy-2-naphthol in addition to 8-methoxy-1,2-dihydro-1,2-naphthalenediol by their EI-MS, 1H- and 13C-NMR spectral data.
- Chun,Ohnishi,Misawa,Shindo,Hayashi,Harayama,Horinouchi
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p. 1774 - 1781
(2007/10/03)
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- Bioconversion of substituted naphthalenes to the corresponding 1,2-dihydro derivatives by Escherichia coli recombinant strains
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1,2-dihydroxynaphthalenes are produced by bioconversion of the corresponding hydrocarbons using Escherichia coli recombinant strains containing the naphthalene dioxygenase and dehydrogenase genes cloned from pseudomonas fluorescens N3. Conversions are lead by a two step procedure without isolation of the dihydrodiol intermediate. Conversion rates depend on the position and nature of the naphthalene substituent.
- Di Gennaro, Patrizia,Bestetti, Giuseppina,Galli, Enrica,Orsini, Fulvia,Pelizzoni, Francesca,Sello, Guido
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p. 6267 - 6270
(2007/10/03)
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- Reduction of ortho-Quinones to Dihydrodiols
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1,2-Naphthaquinone, 5-bromo-1,2-naphthaquinone and dibenzanthracene-3,4-quinone in the form of dibromo-intermediates were reduced to a mixture of cis- and trans-diols by the action of sodium borohydride in ethanol.An alternative synthesis of trans-3,4-dihydroxy-3,4-dihydrodibenzanthracene is also reported.
- Kundu, Nitya G.
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p. 1920 - 1923
(2007/10/02)
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