- Facile Synthesis of New [1,2,4]Triazolo[4,3-b]pyridazine
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A number of new [1,2,4]triazolo[4,3-b]pyridazines were prepared by either cyclocondesation of substituted hydrazinopyridazines with orthoesters or oxidative cyclization of their hydrazone analogs in nitrobenzene as an oxidizing agent. A host of other new
- Arghiani,Seyedi,Bakavoli,Eshghi
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p. 1099 - 1107
(2015/08/06)
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- Acidity control by on/off switching of an intramolecular NH···O hydrogen bond by E/Z photoisomerization of cinnamate framework
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Acidity control by photoswitching of intramolecular NH·· ·O hydrogen bond using E/Z photoisomerization of cinnamate framework was achieved. According to the photoisomerization, the distance between amide NH and carboxylic oxygen was disgregated, and an in
- Matsuhira, Takashi,Yamamoto, Hitoshi,Okamura, Taka-Aki
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supporting information; scheme or table
p. 666 - 667
(2011/04/22)
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- Synthesis of 1,2- and 1,3-dicarboxylic acids via Pd(II)-catalyzed carboxylation of aryl and vinyl C-H bonds
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A Pd(II)-catalyzed reaction protocol for the direct carboxylation of benzoic and phenylacetic acid derivatives to form dicarboxylic acids has been developed. The reaction conditions are also applicable for the carboxylation of vinyl C-H bonds. The first C-H insertion Pd-aryl complex from carboxylic acids has been characterized by X-ray crystallography. Copyright
- Giri, Ramesh,Yu, Jin-Quan
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supporting information; experimental part
p. 14082 - 14083
(2009/03/11)
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- Synthesis of maleic anhydrides and maleic acids by Pd-catalyzed oxidative dicarbonylation of alk-1-ynes
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We have found that carbon dioxide effectively promotes the Pd-catalyzed oxidative carbonylation of terminal alkynes to give maleic anhydrides in fair yields. Reactions were carried out in aqueous dioxane at 60-80 °C in the presence of catalytic amounts of PdI2 in conjunction with KI and under a 4:1:10 mixture of CO/air/CO2 (60 atm total pressure at 25 °C). By working in the presence of a large excess of water, maleic acids were formed selectively with unprecedented catalytic efficiencies for this kind of reaction. In the latter case, the use of an excess of carbon dioxide tended to inhibit, rather than promote, the reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Gabriele, Bartolo,Veltri, Lucia,Salerno, Giuseppe,Costa, Mirco,Chiusoli, Gian Paolo
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p. 1722 - 1728
(2007/10/03)
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- Preparation of (S)-2-Substituted Succinates by Stereospecific Reductions of Fumarate and Derivatives with Resting Cells of Clostridium formicoaceticum
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Fumarate derivatives have been reduced to (S)-2-methylsuccinate 2a, (S)-2-ethylsuccinate 3a and (S)-2-chlorosuccinate 4a in up to 1 M concentrations with Clostridium formicoaceticum.Formate was the electron donor and viologens or anthraquinone-2,6-disulphonate acted as artificial electron mediators.Reductions with freeze-dried cells in 2H2O-buffers led to the (2R,3S)--dideuterated succinate derivatives.The productivity numbers ranged from 450 to 5000 and the enantiomeric excess of all (S)-2-substituted succinates was >/= 99percent.
- Eck, Richard,Simon, Helmut
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p. 13631 - 13640
(2007/10/02)
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- An Efficient and Selective Pallladium-catalysed Oxidative Dicarbonylation of Akynes to Alkyl- or Aryl-maleic Esters
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Terminal alkyne dicarbonylation can be readily effected under mild conditions by treating alkynes with carbon monoxide and alcohols or water at 25-80 deg C in the presence of PdI2, KI and air, with unprecedented catalytic efficiency.Dicarbonylation products are mainly maleic esters or acids and their ring-chain tautomers.The latter are formed to a large extent at room temperature.Reaction pathways are discussed.
- Gabriele, Bartolo,Costa, Mirco,Salerno, Giuseppe,Chiusoli, Gian Paolo
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- Regioselectivity of metal hydride reductions of unsymmetrically substituted cyclic anhydrides. Systems where "steric hindrance along the preferred reaction path" rationalization is not applicable
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Metal hydride reductions of planar cyclic anhydrides such as methylmaleic or 3-substituted phthalic anhydrides occur preferentially at the sterically more hindered carbonyl function.This regioselectivity cannot be rationalized in terms of "the most favourable pathway for non-perpendicular attack by a nucleophile" since both carbonyl groups present are equally accessible to non-perpendicular approach.A study which takes into account the alkaline cation and inductive, mesomeric, and steric effects has been conducted for the reduction of several conjugated and aromatic anhydrides.A qualitative interpretation for the regioselectivities observed in these reductions (as well as in reductions already reported in the literature) is suggested.An early transition state for the catalyzed versus late transition state for the non-catalyzed process is proposed.
- Kayser, Margaret M.,Morand, Peter
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p. 2484 - 2490
(2007/10/02)
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- The Reactions of Lignin with Alkaline Hydrogen Peroxide. Part IV. Products from the Oxidation of Quinone Model Compounds
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Simple para- and orhto-quinoid structures related to lignin have been oxidized with hydrogen peroxide under mild alkaline conditions.Most of the reaction products, i.e. carboxylic acids formed by oxidative cleavage of the quinoid ring together with acids formed by more extensive degradation of the starting materials, were identified after conversion into esters.In addition, small amounts of hydroxylated quinones were found.Mechanisms for the formation of these products are suggested and the significance of the results for the bleaching of mechanical pulps with hydrogen peroxide is briefly discussed.
- Gellerstedt, Goeran,Hardell, Hanne-Lise,Lindfors, Eva-Lisa
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p. 669 - 674
(2007/10/02)
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