Showing papers by "José Elguero published in 1988"
TL;DR: In this article, the 13C chemical shifts and a large collection of coupling constants have been measured for 169 N-substituted azoles with no other substituents on the ring.
Abstract: The 13C chemical shifts and a large collection of coupling constants have been measured for 169 N-substituted azoles with no other substituents on the ring. Simple additive models have been used to discuss both the chemical shifts and the coupling constants. The chemical shift of the substituent depends on the nature of the azole which can, accordingly, be classified into three to six families. Some structural problems (ring-chain isomerism of 1-trifluoromethylsulphonyl-1,2,3-triazole, silylotropy and stannotropy) are also discussed.
138 citations
121 citations
TL;DR: In this paper, 14 new rhodium and iridium complexes of trispyrazol-1-yl)methane (tpzm) ligand have been prepared.
51 citations
46 citations
TL;DR: In the case of 4-substituted derivatives of 3(5)-methyl pyrazoles, the tautomer present in the solid state is a 4-X-5 methyl pyrazole as mentioned in this paper.
Abstract: Carbon-13 nuclear magnetic resonance spectroscopy in the solid state (cross polarization/magic angle spinning technique) is a very suitable method for studying the annular tautomerism of pyrazoles. In all the compounds studied, the tautomerism is frozen and the signals are well resolved except for 3,5-dimethyl-4-nitro pyrazole, which shows broad signals. In the case of 4-substituted derivatives of 3(5)-methylpyrazoles, the tautomer present in the solid state is a 4-X-5 methylpyrazole. 3-Phenyl-5-methylpyrazole (4H or 4-methyl) is favoured over the 3-methyl-5-phenyl tautomer.
20 citations
TL;DR: In this article, the N-aminoheterocycle 4amino-6-methyl-3-(l-methylhydrazino)-5-oxo-4,5-dihydro[1,2,4]triazine 2 reacts with carbonyl compounds to give 1.2,3,4-tetrahydro(1, 2,4,4)tetrazines 6 which undergo dehydrogenation by the action of DDQ to give 5.
18 citations
TL;DR: In this article, a flash vacuum pyrolysis of bis- and tris-(pyrazol-1-yl) methane was carried out and the products actually formed correspond to a radical reaction.
17 citations
TL;DR: The 2-benzothienyl-bis-(4,4'-dimethylaminophenyl) derivative proved to be the most interesting, because of its high selectivity in killing parasites, and a structure-activity relationship for these compounds is proposed.
Abstract: Several heterocyclic analogues of triphenylmethane dyes have been synthesized. Their in vitro activity has been evaluated using the epimastigote forms of Trypanosoma cruzi as an assay system. The m...
14 citations
TL;DR: In this article, 14 N-azolylpropanamides have been prepared by Michael addition of azoles on acrylamide and the compounds have been fully characterized by IR and by 1H and 13C-nmr.
14 citations
TL;DR: In this paper, X-ray diffraction analysis of the "fixed" N-methyl derivative 4 shows that it corresponds to the Z-sE isomer 4b2.
Abstract: Tautomerism of dibenzothiazolylmethane (1) and its C-methyl derivative (2) has been studied by 1H nuclear magnetic resonance, ultraviolet, and infrared spectroscopy using C,C-dimethyl (3) and N-methyl (4) derivatives as model compounds of the "CH" and "NH" forms, respectively. X-ray diffraction analysis of the "fixed" N-methyl derivative 4 shows that it corresponds to the Z-sE isomer 4b2. The CH tautomers are unstable in solution and they slowly isomerize into a mixture of NH tautomers that depends on the solvent and on the C-substituent (H or CH3).
13 citations
TL;DR: In this paper, the results with regard to amino/imino tautomerism, structure of the cations, and slow rotation about a formal C-N double bond were discussed.
Abstract: 13C-NMR chemical shifts have been measured for some 9-aminoacridine derivatives, substituted on positions 9 and 10, in DMSO and for some related salts in D2O. The results are discussed with regard to amino/imino tautomerism, structure of the cations, and slow rotation about a formal C-N double bond.
TL;DR: Fully optimized INDO geometries have been calculated for twelve azoles, their corresponding cations and anions, both isolated and specifically solvated by five water molecules.
Abstract: Fully optimized INDO geometries have been calculated for twelve azoles, their corresponding cations and anions, both isolated and specifically solvated by five water molecules The protonation and deprotonation energies of the isolated molecules do not show any characteristic trend but those of the solvated species show a behaviour similar to that found experimentally in solution From these calculations it is possible to explain the particular behaviour of 1,2-diazoles compared with all other azoles with regard to acid-base equilibria in water
TL;DR: The mean hydrophobic contributions, pi*m, of substituents in a sample of 34 monosubstituted pyridines has been determined by using reversed-phase high-performance liquid chromatography.
TL;DR: All 1, 1'-bis-azolylarylmethanes have minima inhibitory concentrations higher than that of chlotrimazol, used as positive control, and the antifungal activity has been tested, in vitro, against Botrytis cinerea, Aspergillus flavus, Mucor rouxii and Candida albicans.
Abstract: A series of 1, 1'-bis-azolylarylmethanes has been prepared by reaction of azoles and their benzoderivatives with ortho-, and para-chlorobenzaldehydes, thiophene-2-carbaldehyde and furan-2-carbaldehyde in the presence of zinc chloride as catalyst. The antifungal activity has been tested, in vitro, against Botrytis cinerea, Aspergillus flavus, Mucor rouxii and Candida albicans. All 1, 1'-bis-azolylarylmethanes have minima inhibitory concentrations (MIC) higher than that of chlotrimazol, used as positive control.
TL;DR: In this article, the relatively stable 1H-isomer was isolated in pure state as a 1:1 complex with 1, 1-bis(2, 4-dimethylphenyl)but-2-yn-1-ol.
Abstract: From an equilibrium mixture of two tautomers, 1H- and 2H-1,2,3-triazole, the relatively unstable 1H-isomer was isolated in pure state as a 1:1 complex with 1, 1-bis(2,4-dimethylphenyl)but-2-yn-1-ol. The two equilibrating tautomers of almost the same stability, 3- and 5-methyltriazole, were also isolated in pure state as a 1:1:1 complex of these and the host compound.
TL;DR: In this paper, the effect of solvent concentration, temperature, and the nature of the substituents on the KT variation has been investigated for 2H-1,2,6-thiadiazin-3-one derivatives and pyrazol-5-ones.
Abstract: Tautomerism of 2,5-disubstituted (4), 4,5,6-substituted (5), and 5-substituted 2H-1,2,6-thiadiazin-3-one 1,1-dioxides (6) has been studied by u.v., 1H, 13C and natural-abundance 15N n.m.r. spectroscopies. The effect of solvent concentration, temperature, and the nature of the substituents on the KT variation has been investigated. Comparison between the tautomeric behaviour of 2H-1,2,6-thiadiazin-3-one derivatives and the related pyrazol-5-ones provides some conclusions about the role of aromaticity on the stability of the different tautomers.
TL;DR: In this paper, the crystal structures of 1a, 1b, 1.EtOH, 1c, 1.iPrOH and 1d, 1 2tBuOH have been studied by X-ray diffraction.
TL;DR: In this paper, a three-dimensional network of hydrogen bonds involving all O and N atoms with an H 3 O + ion counteracting the final charge of the fused system is described.
Journal Article•
TL;DR: In this article, four basis sets, i.e.g., minimal, split-valence, without and with d functions, were used to determine the unknown molecular structure of amidosulfurous acid.
Abstract: Four different basis sets, i.e. minimal, split-valence, without and with d functions (STO-3G, 4-31G, STO-3G* and 6-31G*) have been used to determine the unknown molecular structure of amidosulfurous acid. Boys' localized orbitals provide a picture of the electronic distribution, particularly useful for this kind of molecule with so many lone pairs. Without d functions, the calculation leads to an ylide picture, whereas the inclusion of d functions provides a description in terms of an S O double bond.
TL;DR: Synthese de pyridinio-5' azolures and pyride-2' benzimidazolures a partir des heteryl-1 pyridine correspondants: calculs MNDO, structures cristalline, moleculaire et electronique as mentioned in this paper.
Abstract: Synthese de pyridinio-5' azolures et de pyridinio-2' benzimidazolures a partir des heteryl-1 pyridiniums correspondants: calculs MNDO, structures cristalline, moleculaire et electronique
TL;DR: The iminophosphorane (III) reacts with acyl chlorides to give the desired ring system (VI) in moderate to good yields as mentioned in this paper, which is the most similar to ours.
Abstract: The iminophosphorane (III) reacts with acyl chlorides to give the desired ring system (VI) in moderate to good yields.