| 1. |
- Aas, Wenche, et al.
(författare)
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Equilibria and dynamics in binary and ternary uranyl oxalate and acetate/fluoride complexes
- 1999
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Ingår i: Journal of the Chemical Society - Dalton Transactions. - : Royal Society of Chemistry (RSC). - 0300-9246 .- 1364-5447. ; :8, s. 1311-1317
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Tidskriftsartikel (refereegranskat)abstract
- The formation of ternary UO2(ac)pFq2-p-q (p = 1 or 2 and q = 1-3) complexes, and their equilibrium constants were investigated by potentiometric titrations and 19F NMR spectroscopy. The equilibrium constants have been determined from the emf data in a NaClO4 medium at constant sodium concentration, [Na+] = 1.00 M at 25°C, except for the UO2(ac)F32- complex where 19F NMR at -5°C was used. The magnitude of the equilibrium constant for the stepwise addition of fluoride indicates that prior co-ordination of acetate has only a small effect on the subsequent bonding of fluoride. The acetate exchange in the ternary UO2(ac)F32- complex was studied using 19F NMR. Through magnetisation transfer experiments, it was possible to confirm the provisional mechanism from a previous study and also the consistency of the rate constants for the five different exchange pathways required to describe the fluoride exchange. The exchange takes place via the intermediate UO2F3(H2O)2-, indicating that the acetate exchange follows an interchange mechanism with solvent participation in the transition state. The rates and mechanisms of the ligand exchange reactions in UO2(ox)2(H2O)2- and UO2(ac)2(H2O) have been studied using 13C NMR techniques at -5°C. The rate law is v = k-[complex][ligand], and the second order rate constant and the activation parameters for both systems have been determined. The reactions most likely take place through an Eigen-Wilkins type of mechanism, where the first step is a pre-equilibrium of an outer-sphere complex followed by a rate determining exchange of water. The rate constants for the water exchange reactions are very similar to that in UO2(H2O)52+. The information from the binary oxalate system rules out the formation of UO2(ox)2(H2O)2- as an intermediate in the exchange reactions in the previously studied UO2(ox)2F3-, also in this case confirming a previously suggested exchange mechanism. The H+/D+ isotope effects and a linear free energy relationship suggest that the main catalytic effect of H+ on ligand exchange rates is due to the formation of a protonated precursor. Hence, the catalytic effect depends on the basicity of the ligand and the site for the proton attack.
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| 2. |
- Csende, F., et al.
(författare)
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Copper(II) chloride as an efficient reagent for the dehydrogenation of pyridazinone derivatives
- 1995
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Ingår i: Synthesis (Stuttgart). - : Georg Thieme Verlag KG. - 0039-7881 .- 1437-210X. ; :10, s. 1240-1242
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Tidskriftsartikel (refereegranskat)abstract
- A new procedure is described for the preparation of pyridazinones from 4,5-dihydropyridazinones under mild conditions with CuCl2 in MeCN via halogenation and spontaneous HCl elimination. For the trans-hexahydrophthalazin-8(1H)-one 1B*, the HCl elimination is five times faster than for the corresponding cis isomer 1B.
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| 3. |
- Csende, F., et al.
(författare)
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Synthesis and structural study of novel 1,2-diazepinones and azabicyclooctane derivatives
- 1996
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Ingår i: Heterocyclic Communications. - : Walter de Gruyter GmbH. - 0793-0283 .- 2191-0197. ; 2:5, s. 453-461
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Tidskriftsartikel (refereegranskat)abstract
- Condensation of 3-toluoyl-1,2,2-trimethylcyclopentane-1-carboxylic acid 2 with hydrazine, diamines or 3-aminopropanol afforded the novel bicyclic 1,2-diazepinone 3 or various condensed azabicyclooctane derivatives 4-6, respectively. Further transformations of the 1,2-diazepinone 3 to its perhydro 7 and N-methyl 8 derivatives are also described. Compound 3 when treated with Zn/HC1 resulted in the azabicyclo[3.2.1] octanone derivative 9 by a stereoselective ring contraction. Lactone formation from 3 on treatment with acetic anhydride has also been attempted.
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| 4. |
- Cziáky, Z., et al.
(författare)
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Synthesis of 2H‐pyrano[2,3‐b]quinolines. Part II. Preparation and 1H‐nmr investigations of 4‐hydroxy‐2‐methyl‐3,4‐dihydro‐2H‐pyrano[2,3‐b]quinolines
- 1995
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Ingår i: Journal of Heterocyclic Chemistry. - : Wiley. - 0022-152X .- 1943-5193. ; 32:3, s. 755-760
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Tidskriftsartikel (refereegranskat)abstract
- Diastereoisomers of 4‐hydroxy‐2‐methyl‐3,4‐dihydro‐2H‐pyrano[2,3‐b]quinolines 8 and 9 were synthesized starting from the appropriate 2‐chloroquinoline‐3‐carboxaldehydes 1. The relative configuration of the 1,3‐diol intermediates 4 and 5 was determined on the basis of the 13C‐nmr spectra of their acetonides. The relative stereochemistry of title compounds was confirmed by using homonuclear NOE and selective decoupling experiments, as well as by analysis of the coupling patterns observed in their 1H‐nmr spectra.
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| 5. |
- Farkas, I., et al.
(författare)
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Crystal structure of the sodium salt of the uranyl-oxyacetate-fluoride dimer, Na4(UO2)2(OCH2COO)2F 4 · 6H2O
- 1999
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Ingår i: Acta Chemica Scandinavica. - : Danish Chemical Society. - 0904-213X .- 1902-3103. ; 53:11, s. 1009-1012
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Tidskriftsartikel (refereegranskat)abstract
- The structure of the ternary uranyl-oxyacetate-fluoride dimer, (UO2)2(OCH2COO)2F4 4-, was studied by single crystal X-ray diffraction. The space group is P1̄, and the structure contains discrete dimers with a double pentagonal bipyramid geometry, linked by octahedrally coordinated sodium ions. The uranyl ion has a coordination number of five with two fluorides and three oxygens coordinated in a plane perpendicular to the linear UO2 axis. The dimer is formed via bridging oxygen atoms from the deprotonated hydroxyl groups of the glycolate ligands.
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| 6. |
- Kálai, T., et al.
(författare)
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Synthesis and reactions of new nitronyl nitroxides
- 1997
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Ingår i: Synthesis (Stuttgart). - : Georg Thieme Verlag KG. - 0039-7881 .- 1437-210X. ; 1997:09, s. 1049-1055
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Tidskriftsartikel (refereegranskat)abstract
- Various new 2-substituted 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-yloxyl 3-oxide mono- 1b, 7, 13a,b, 14, 15, 16, 17, 22 and biradicals 8, 9 were prepared. The nitronyl nitroxide functions were selectively reduced by Fe/HOAc to 1-hydroxyimidazoline derivatives 3b, 11, 21. The reductions by Zn/HCl led to imidazolines 4, 12. The nitronyl nitroxide functions remained inert when the 2-phenyl compound was nitrated by H2SO4/HNO3 to give nitrophenyl nitronyl nitroxide derivatives 13a,b, 14.
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| 7. |
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| 8. |
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| 9. |
- Kćrćdi, F., et al.
(författare)
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Fused 1,2,4-triazole heterocycles. ii : Reaction of 2-chloro-3-(1,3-dioxolan-2-yl)quinolines with 1,2,4-triazole-5-thiol
- 1995
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Ingår i: Heterocyclic Communications. - : Walter de Gruyter GmbH. - 0793-0283 .- 2191-0197. ; 1:2-3, s. 195-198
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of 2-chloro-3-(1,3-dioxolan-2-yl)quinolines 1 with 1,2,4-triazole-5-thiol 2 leads to the formation of a mixture of 11-(2-hydroxyethyl)oxy-11H-[1,2,4]triazolo[5',1':2,3][1,3]thiazino[6,5-b]quinolines 3 and 11-(2-hydroxyethyl)oxy-11/-/-[1,2,4]triazolo[3',4':2,3][1,3]thiazino[6,5-£>]quinolines 4. The structures of the separated regioisomers were determined by homonuclear NOE difference spectroscopy and the results were further confirmed by desulfurisation.
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| 10. |
- Kóródi, F., et al.
(författare)
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Fused 1,2,4-TriazoIe Heterocycles. IV. Synthesis of Four New Heterocyclic Ring Systems of [1,2,4]Triazolo[1,3]thiazinoquinolines
- 1997
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Ingår i: Journal of Heterocyclic Chemistry. - : Wiley. - 0022-152X .- 1943-5193. ; 34:4, s. 1275-1281
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Tidskriftsartikel (refereegranskat)abstract
- Syntheses of 5H-[1,2,4]triazolo[5′1′:2,3][1,3]thiazino[5,4-c]quinolines 8, 5H-[1,2,4]triazolo[3′,4′:2,3][1,3]thiazino[5,4-c]quinolines 9, 5H-[1,2,4]triazolo[5′1′:2,3][1,3]thiazino[5,6-c]quinolines 14 and 5H-[1,2,4]triazolo[3′,4′:2,3][1,3]thiazino[5,6-c]quinolines 15 are described starting from 4-chloro-3-chloromethylquinaldine (4) and 1,2,4-triazole-5-thiols 5 taking advantage of different reactivity of the chlorine atoms of 4 under different reaction conditions. The structures of products 8, 9, 14 and 15 and the intermediates leading to them were confirmed by desulfurization, unequivocal syntheses and nmr spectroscopy as well.
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