- Solvent-free Diels-Alder reaction in a closed batch system
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Solvent-free Diels-Alder reactions were carried out by heating a mixture of a volatile diene, such as 1,3-butadiene, isoprene, or 2,3-dimethyl-1,3- butadiene, and a dienophile, such as methyl vinyl ketone, methyl acrylate, or maleic anhydride, in a closed batch reactor. High yields of Diels-Alder products were obtained without using solvents and catalysts within a short reaction time in most of the reactions. In particular, several reactions of dienophiles with 1,3-butadiene, which is known as a diene with low reactivity because of its gaseous form, also proceeded with high yields of Diels-Alder products in the closed batch reactor under conditions pressured by the reactant vapor. Solvent-free reactions provided high yields compared to reactions in solvent since the reaction heat directly resulted in increasing the reaction temperature and pressure. Energy in the exothermic reaction was used effectively in the closed batch system under solvent-free conditions.
- Sun, Daolai,Sato, Fumiya,Yamada, Yasuhiro,Sato, Satoshi
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p. 276 - 282
(2013/05/08)
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- Stoichiometric and catalytic cross dimerization between conjugated dienes and conjugated carbonyls by a ruthenium(0) complex: Straightforward access to unsaturated carbonyl compounds by an oxidative coupling mechanism
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A series of stoichiometric and catalytic cross dimerizations between conjugated dienes and conjugated carbonyls are studied. The reaction of Ru(η4-cisoid-1,3-butadiene)(η4-1,5-COD)(NCMe) (2a) with methyl acrylate gives a Ru(0) complex, Ru[methyl η4-cisoid- (2E,4E)-hepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3aa) in 97% yield. Similar treatments of 2a with a series of tert-butyl acrylate, methyl crotonate, 3-buten-2-one, and N,N-dimethylacrylamide produce similar analogues of 3ac. When (E)-1,3-pentadiene complex 2d is employed in the reaction with methyl acrylate, the branched coupling product Ru[methyl η4- cisoid-(2E,4E)-4-methylhepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3da-b) is dominantly obtained in 65% yield along with the linear product in 19% yield. In the case of the (E)-2,5-dimethylhexa-1,3-diene complex 2e, the corresponding branch product is exclusively obtained in 86% yield. The catalytic cross dimerizations between conjugated dienes and conjugated carbonyls are established by 2. The origin of the present chemoselectivity is the η4-coordination of a conjugated diene and η2- coordination of an electron-deficient alkene to formal 6e coordination sites at Ru(0), and the regioselectivity being prone to giving branched products is interpreted as an oxidative coupling mechanism, involving nucleophilic attack of the coordinated diene to the coordinated electron-deficient alkene.
- Hirano, Masafumi,Arai, Yasutomo,Hamamura, Yuka,Komine, Nobuyuki,Komiya, Sanshiro
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experimental part
p. 4006 - 4019
(2012/07/13)
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- Regioselective epoxidation of different types of double bonds over large-pore titanium silicate Ti-β
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Regioselective epoxidation of different types of double bonds located within the cyclic and acyclic parts of bulky olefins has been investigated using large-pore titanium silicate Ti-β in the presence of dilute aqueous H 2O2 as oxidant under mild liquid-phase conditions. Our experimental results revealed that side-chain vinylic double bonds are selectively epoxidized than those in the cyclohexene-ring. The epoxidation tendency of various bulky olefins with different positional and/or geometric isomers over Ti-β follows the order: terminal -CC- > ring -CC- ≈ bicyclic ring -CC- > allylic C - H bond. Unlike 4-vinyl-1-cyclohexene, epoxidation of an equimolar mixture of cyclohexene and 1-hexene under identical conditions using Ti-β exhibits completely different selectivity and product distributions. Steric factor and accessibility of reactants to active Ti-sites are responsible for the observed regioselectivity of bulky alkenes.
- Sasidharan, Manickam,Bhaumik, Asim
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experimental part
p. 60 - 67
(2010/12/18)
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- Na+-dependent high affinity binding of [3H]LY515300, a 3,4-dimethyl-4-(3-hydroxyphenyl)piperidine opioid receptor inverse agonist
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Analogues of 3,4-dimethyl-4-(3-hydroxyphenyl)piperidines are high affinity inverse agonists for μ-, δ- and κ-opioid receptors. To characterize inverse agonist binding, we synthesized a high specific activity radioligand from this series, [3H]LY
- Statnick, Michael A.,Suter, Todd M.,Gackenheimer, Susan L.,Emmerson, Paul J.,Quimby, Steve J.,Gehlert, Donald R.,Wheeler, William J.,Mitch, Charles H.
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p. 139 - 150
(2007/10/03)
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- Palladium(II)-catalyzed oxidation of terminal alkenes to methyl ketones using molecular oxygen
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Palladium(II) acetate catalyzes the aerobic oxidation of terminal alkenes in toluene into the corresponding methyl ketones in the presence of a catalytic amount of pyridine using propan-2-ol as a reductant and molecular oxygen as an oxidant. Two catalytic cycles sharing a Pd(II)-OOH species are proposed. One is the formation of a Pd(II)-H species in the oxidation of propan-2-ol to acetone, followed by reaction with molecular oxygen to give a Pd(II)-OOH species, and the other is peroxypalladation of an alkene with the Pd(II)-OOH species produced to afford a methyl ketone in the presence of H2O2 produced by the former catalytic cycle. The Royal Society of Chemistry 2000.
- Nishimura, Takahiro,Kakiuchi, Nobuyuki,Onoue, Tomoaki,Ohe, Kouichi,Ucmura, Sakae
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p. 1915 - 1918
(2007/10/03)
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- Clemmensen Reduction. XI. Fragmentation Reactions of Some 3-Acetylcycloalkanones
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Clemmensen reduction of a series of 3-acetylcycloalkanones yields, as the major product, an acyclic unsaturated ketone, the product of fragmentation.Some normal carbonyl-methylene reduction also occurs.A mechanistic rationale for the fragmentation is advanced.
- Bailey, Karen E.,Davis, Brian R.
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p. 1827 - 1834
(2007/10/03)
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- Strong Lewis acids derived from molybdenum and tungsten nitrosyls containing the tri-2-pyridylmethane ligand. Dynamic NMR studies of their adducts with aldehydes, ketones, and esters
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The doubly charged Lewis acid percursors [HC(py)3M(NO)2(CO)](SbF6)2 (M = Mo, W; HC(py)3 = tri-2-pyridylmethane) are conveniently synthesized by reaction of HC(py)3M(CO)3 and 2 equiv of NOSbF6. Facile loss of CO from the precursors generates the [HC(py)3M(NO)2](SbF6)2 Lewis acids. The Lewis acidity of the tungsten complex is greater than that of the molybdenum complex. With the 1H NMR chemical shifts of bound crotonaldehyde as a qualitative assessment of relative acidity, the acidity of the tungsten species is comparable to that of BF3 and AlCl3, while that of the molybdenum species is similar to that of TiCl4. Analysis of the NMR spectra of the Lewis acid-organic carbonyl base adducts, which include the adducts of aldehydes, ketones, and esters, showed that η1-M(O=C) interactions dominate the chemistry. The barriers of rotation about the aldehyde C1-C2 bonds in the p-anisaldehyde adducts of the molybdenum and tungsten species were measured to be 12.8 and 13.7 kcal/mol, respectively, which are significantly higher than that for the free p-anisaldehyde. The exchange behavior between the E and Z isomers of the acetate adducts could be observed on the NMR time scale. The E to Z interconversion barriers of 12.2 ± 0.1 and 12.3 ± 0.1 kcal/mol for the methyl acetate and ethyl acetate complexes, respectively, were calculated from the results of variable-temperature proton NMR experiments. The free energy differences between the E and Z conformers of the methyl acetate and ethyl acetate adducts are 1.27 ± 0.01 and 0.96 ± 0.01 kcal/mol at 229 K, respectively.
- Faller,Ma, Yinong
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p. 1579 - 1586
(2007/10/02)
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- EFFICIENT CYCLOADDITION DURING ADSORPTION ON CHROMATOGRAPHIC SOLVENTS
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An essentially new method was developed for carrying out cycloaddition on the surface of chromatographic adsorbents in the absence of solvent.This method permits the use of much milder reaction conditions and to increase the reaction's selectivity.
- Veselovskii, V. V.,Gybin, A. S.,Lozanova, A. V.,Moiseenkov, A. M.,Smit, V. A.
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- NEW LEWIS ACID CATALYSTS FOR THE DIELS-ALDER REACTION
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Catechol boron bromide (1) and ferrocenium hexafluorophosphate (2) function as Lewis acid catalysts for the Diels-Alder reaction.
- Kelly, T. Ross,Maity, Sanat K.,Meghani, Premji,Chandrakumar, Nizal S.
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p. 1357 - 1360
(2007/10/02)
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- The Cycloaddition of the 1,3-Butadiene Radical Cation with Acrolein and Methyl Vinyl Ketone
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The 1,3-butadiene radical cation reacts with acrolein and methyl vinyl ketone to produce 'stable' adducts.The nature of the reaction and the structures of the adducts were investigated by collisional activation decomposition (CAD) combined with tandem mas
- Castle, Lyle W.,Gross, M. L.
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p. 637 - 646
(2007/10/02)
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- DRAMATIC ACCELERATION OF THE DIELS-ALDER REACTION BY ADSORPTION ON CHROMATOGRAPHY ADSORBENTS
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The development of a new method for effecting cycloadditions on the surface of chromatographic adsorbents in the absence of solvents that leads to a moderation of the reaction conditions and an increase in selectivity is described.
- Veselovsky, V. V.,Gybin, A. S.,Lozanova, A. V.,Moiseenkov, A. M.,Smit, W. A.,Caple, R.
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p. 175 - 178
(2007/10/02)
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- Oxygen-Transfer Reactions Catalyzed by Nitropalladium(II) Complexes. Reactivity of Bis(μ-chloro)bishept-2-yl-C,N>dipalladium: Cleavage of the C-Pd Bond
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The oxidation of various norbornene derivatives and several mono- and nonconjugated diolefines with the catalyst (CH3CN)2PdCl(NO2) (1) is described.In contrast with the results previously observed with Wacker-type catalysts (PdCl2-CuCl2), the epoxidation process is selective for the strained norbornene double bond with dienes 5 or 7.Methyl ketones such as 14, 16, 18, and 20 are obtained with unhindered terminal olefins (e.g., 20 from 19).The solution structure of bis(μ-chloro)bishept-2-yl-C,N>dipalladium (32) as analyzed by 1H and 13C NMR spectroscopy shows that there is a slight distortion of the palladacycle.The reactivity of isolated complex 32 has been studied.In aprotic solvents (benzene, toluene) and in the absence of any nucleophilic reagents, a pure oxygen-transfer reaction yielding epoxide 4 is the sole process.In the presence of nucleophiles or oxidants like CuCl2 or Pb(OAc)4 in protic or aprotic solvents (HOAc, CH2Cl2), the cleavage mode of the C-Pd bond is quite different.The formation of disubstituted norbornane derivatives 34 and 35 and nonrearranged products 36 and 37 are observed.The formation of various products from isolated complex 32 is discussed in terms of reaction mechanisms, particularly relative to the C-Pd bond reactivity.
- Chauvet, F.,Heumann, A.,Waegell, B.
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p. 1916 - 1922
(2007/10/02)
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- CHEMOSELECTIVE OXIDATION WITH MOLYBDENIUM CATALYST-t-BUTYL HYDROPEROXIDE
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Benzyltrimethylammonium tetrabromooxomolybdate is an excellent chemoselective catalyst to oxidize secondary alcohols to ketones, primary alcohols to esters, and aldehydes to acids or esters with t-butyl hydroperoxide.
- Masuyama, Yoshiro,Takahashi, Masato,Kurusu, Yasuhiko
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p. 4417 - 4420
(2007/10/02)
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- EPOXIDATION WITH MOLECULAR OXYGEN IN THE PRESENCE OF PdCl(NO2)(CH3CN)2
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Several mono or non conjugated diolefins are submitted to the action of oxygen in presence of catalytic amounts of PdCl(NO2)(CH3CN)2.Depending on the olefin structures methylketones or epoxides are obtained.
- Heumann, Andreas,Chauvet, Frederic,Waegell, Bernard
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p. 2767 - 2768
(2007/10/02)
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