- How does aqueous solubility of organic reactant affect a water-promoted reaction?
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It was widely reported that under the "on water" condition, various water-promoted organic reactions can proceed with very high speed. Thus, it is considered that the aqueous solubility of reactant is not an important issue in these reactions. Three types of water-promoted organic reactions were investigated in the current study to distinguish whether the reaction rate of an aqueous reaction was affected by the aqueous solubilities of the reactants. The results showed that, for a Diels-Alder reaction which was fast under the neat conditions, the aqueous solubilities of reactants had little influence on the reaction. However, for the reactions which proceeded slowly under the neat conditions, such as [2σ+2σ+2π] cycloaddition reactions and epoxide aminolysis reactions, the reactants with good aqueous solubilities proceeded fast in water. Poorly aqueous soluble reactants reacted slowly or did not react under the "on water" condition, and an appropriate amount of organic cosolvent was needed to make the reaction become efficient. This evidence suggested that for these two types of reactions, the dissolution of the reactants in water was required.
- Zuo, Yi-Jie,Qu, Jin
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p. 6832 - 6839
(2014/08/18)
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- Preparation of ecological catalysts derived from Zn hyperaccumulating plants and their catalytic activity in Diels-Alder reaction
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Zn hyperaccumulating plants Noccaea caerulescens and Anthyllis vulneraria were used as the starting material for preparation of novel Lewis ecological catalysts. Those catalysts efficiently mediate the Diels-Alder reaction. High yields, very good regio- a
- Escande, Vincent,Olszewski, Tomasz K.,Grison, Claude
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p. 731 - 737
(2014/07/21)
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- Microwave-assisted solvent-free Diels-Alder reaction - A fast and simple route to various 5,6-substituted norbornenes and polychlorinated norbornenes
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A series of 5,6-substituted norbornenes and 5,6-substituted polychlorinated norbornenes was prepared by using a microwave-assisted Diels-Alder reaction. This procedure proved very versatile, fast, and with an easy workup step, and therefore suitable even for large-scale synthesis. Georg Thieme Verlag Stuttgart · New York.
- Dejmek, Milan,Hrebabecky, Hubert,Sala, Michal,Drainsky, Martin,Nencka, Radim
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experimental part
p. 4077 - 4083
(2012/01/05)
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- Remote Exo/Endo selectivity in selective monohydrolysis of dialkyl bicyclo[2.2.1]heptane-2,3-dicarboxylate derivatives
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Figure presented High exo-facial selectivity was observed in the selective monohydrolysis of a series of near-symmetric diesters that possess an exo-ester group and an endo-ester group attached on a norbornane or norbornene skeleton. The selectivities were found to be clear-cut, although the reaction center in these reactions is one covalent bond distant from the norbornane or norbornene ring, where the difference of the environment between the exo face and endo face is therefore expected to be negligible. The effect of the co-solvent we studied earlier for the selective monohydrolysis reaction was also confirmed and contributed to improvement of the yields of the half-esters.
- Niwayama, Satomi,Cho, Hanjoung,Zabet-Moghaddam, Masoud,Whittlesey, Bruce R.
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supporting information; experimental part
p. 3775 - 3780
(2010/09/03)
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- Self-immobilizing precatalysts: Norbornene-bridged zirconium ansa-metallocenes
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We report here the synthesis of new tethered biscyclopentadienyl and bisindenyl zirconocenes, bearing one unsaturation on the interannular bridge, and their use as self-immobilizing catalysts. They proved to be active catalysts towards ethylene polymerization in solution, with activities comparable to those displayed by commercial rac-Et-(Ind)2ZrCl2. When tested as self-polymerization catalysts under suitable experimental conditions, they gave colored precipitates that, once reactivated with MAO, were significantly active in ethylene polymerization, although lower than those of the corresponding catalytic systems in solution. The molecular weights of the produced polymers were similar to those obtained with the same catalysts in solution, but their distribution resulted to be broader, with values typical of heterogeneous catalytic systems. From 13C NMR studies we had the first spectroscopic evidence of the actual incorporation of a metallocene of this type into a polymeric chain.
- Polo, Eleonora,Forlini, Fabrizio,Bertolasi, Valerio,Boccia, Antonella Caterina,Sacchi, Maria Carmela
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experimental part
p. 1544 - 1556
(2009/07/30)
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- Diels-Alder reactions using supercritical water as an aqueous solvent medium
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A variety of Diels-Alder reactions have been performed in supercritical water as a reaction medium. The rapid reaction of Diels-Alder reactions of cyclopentadiene and various electron poor dienophiles such as diethyl fumarate and acrylonitrile is observed in supercritical water, and leads to high yields of clean products without added catalysts.
- Korzenski, Michael B.,Kolis, Joseph W.
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p. 5611 - 5614
(2007/10/03)
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- Stereospecificity and concertedness of Retro-Diels-Alder fragmentation in some diester systems upon chemical ionization
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Retro-Diels-Alder (RDA) fragmentation of cis- and trans-2,3-diethoxycarbonyl-5,6,7,8-dibenzobicyclo[2.2.2] octanes under isobutane and methane chemical ionization conditions is highly stereospecific, giving rise to protonated diethyl maleate and fumarate, respectively. This behaviour indicates a single-step concerted mechanism, analogous to the ground-state RDA process that occurs in neutral molecules in the condensed phase. The analogous dissociation is partially stereospecific in stereoisomeric endo-, exo- and trans-2,3-diethoxycarbonylbicyclo [2.2.1]heptanes and non-stereospecific in endo-, exo- and trans-2,3-diethoxycarbonyl-5,6-benzobicyclo [2.2.2]octanes, indicating the involvement of a stepwise mechanism in the latter two systems. The different behaviour of the above systems is explained in terms of the energy of the RDA fragmentation. The differentiation and quantitative estimates of protonated diethyl maleate and fumarate were obtained from collision-induced dissociation measurements.
- Denekamp,Weisz,Mandelbaum
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p. 1028 - 1032
(2007/10/03)
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- A stereoselective biocatalytic Diels-Alder reaction
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Baker's yeast catalyzes the stereoselective Diels-Alder reaction of cyclopentadiene 1 with dienophiles 2, 4 and 6. A predominant formation of exo isomer is observed in some cases.
- Rao,Srinivasan,Bhanumathi
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p. 5959 - 5960
(2007/10/02)
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