Showing papers by "José Elguero published in 1984"
TL;DR: In this paper, 13C shielding data for 100 derivatives of pyrazole are reported, including methyl, ethyl, n-propyl, tert-butyl, phenyl, hydroxymethyl, carboxyl, ethoxycarbonyl, cyano, amino, hydrazino, nitro, azido, chloro, bromo and iodo groups.
Abstract: 13C shielding data for 100 derivatives of pyrazole are reported. These include methyl, ethyl, n-propyl, tert-butyl, phenyl, hydroxymethyl, carboxyl, ethoxycarbonyl, cyano, amino, hydrazino, nitro, azido, chloro, bromo and iodo groups as substituents on the ring carbon atoms.
42 citations
TL;DR: In this paper, the synthesis and properties of rhodium(I) complexes of formulae [RhCl(diolefin) 2 (L)] (or [RhodiumCl(DIOlefin)(L)] n (ClO 4 ) n) are reported.
28 citations
TL;DR: In this paper, a theoretical study of fourteen N,N-linked biazoles has been carried out using the MNDO method with full optimization of the geometries and the variation of energy as a function of the conformation around the central N-N bond shows in all cases the higher stability of the orthogonal or near-orthogonal form.
Abstract: A theoretical study of fourteen N,N-linked biazoles has been carried out using the MNDO method with full optimization of the geometries. The variation of energy as a function of the conformation around the central N—N bond shows in all cases the higher stability of the orthogonal or near-orthogonal form. The contribution of the three main types of "ortho" interactions and the effect of quaternization have been evaluated. Of the electronic properties calculated, one must emphasize the excellent agreement of dipole moments with experimental values.
27 citations
TL;DR: The chemical shifts and coupling constants of [1,2-15N2] pyrazole, 2-(1, 2- 15N2]-pyrazolyl)-2-[l, 3-2H6]propanol, 1-nitro[1,215N 2] and 3-nitrogen[ 1,2 -15N 2 ]pyrazole are reported in this paper.
Abstract: The chemical shifts and coupling constants of [1,2-15N2]pyrazole, 2-(1-[1,2- 15N2]pyrazolyl)-2-[l,3-2H6]propanol, 1-nitro[1,215N2] and 3-nitro[1,2-15N2]pyrazole are reported.
26 citations
TL;DR: A plot of pKa values for eleven azoles and benzazoles vs the experimental ionization energy of the nitrogen lone pair shows the existence of three groups of compounds: simple unsubstituted azoles, pyrazole, oxazole, isoxazole and benzoxazoles carrying a methyl group α- to the basic centre.
20 citations
19 citations
TL;DR: In this paper, the assignment of the 2JCH and 3JCH coupling constants for N- substituted pyrazoles has been studied, where annular tautomerism is prevented and each carbon atom can have two long-range coupling constants with the ring protons.
Abstract: Although quite a few papers have been devoted to the 13C NMR study of pyrazoles, there is one problem that has not yet been satisfactorily solved, namely the assignment of the 2JCH and 3JCH coupling constants. In general, the 3C chemical shifts and 1JCH coupling constants can be easily attributed, but the assigment of the long-range 2JCH and 3JCH coupling constants is not straight forward. In N- substituted pyrazoles, where annular tautomerism is prevented, each carbon atom can have two long-range coupling constants with the ring protons.
17 citations
01 Jan 1984
TL;DR: In this paper, the RMN de dix complexes pyrazolate-rhodium avec du carbonyle ou du cyclooctadiene-1,5 ont been enregistrés.
Abstract: Les spectres RMN de dix complexes pyrazolate-rhodium avec du carbonyle ou du cyclooctadiene-1,5 ont ete enregistres. La conformation "bateau" du cycle hexagonal central (N 4 Rh 2 ) a ete mise en evidence.
14 citations
TL;DR: In this paper, the cyclohexanospirohydantion reaction products have been studied by 13C nmr in order to indentify mono and disubstituted derivatives and to determine the substituent position.
13 citations
TL;DR: In this paper, a linear relationship exists between the protonation energy, ΔEp, and the charge on the basic centre of a pyrazoles atom, qN2.
Abstract: In opposition to all previous reports, we show in this paper that a linear relationship exists between the protonation energy, ΔEp, and the charge on the basic centre. The unfavourable case of pyrazoles was selected to test the model. Instead of the total charge on the basic nitrogen atom, qN2, we have used a “lone pair charge”, qLPF, which is defined here for the first time.
10 citations
TL;DR: A number of mesoionic compounds derivatives of the bicyclic system 1,2,4-triazolo(4,3-b)-1, 2, 4 triazolium iodide and aryl isothiocyanates have been prepared from 4-amino-1-methyl-3,5-bis(methylthio)-1.
TL;DR: In this article, the bidentate ligands 3,3,5,5′-tetramethyl-4,4′-bi-1H-pyrazole (tmbpz) gave complexes with the formula MCl 2 (LL) (M = Co, LL = mbpz; M = Ni, LL= tmbPz, tmmbpZ, mBPz).
TL;DR: The only sixteen experiments of a fractional factorial design have been necessary to study the influence on the yield of cyclohexanospirohydantoin of the seven following factors: flask volume, cyanide and ammonium carbonate concentrations, quanities of water and ethanol, temperature and reaction time.
TL;DR: In this article, the synthesis of six derivatives of 2-methyl-5-nitroimidazole 1-substituted by a CH2CH2Het group (Het being a pyridinium or a 1substitized imidazolium) has been carried out.
TL;DR: Using Cooks' method, the relative gas phase proton affinities of six azoles (imidazole, benzimide, pyrazole, indazole and 2-methylindazole) have been determined as discussed by the authors.
Abstract: Using Cooks' method, the relative gas phase proton affinities of six azoles (imidazole, benzimidazole, pyrazole, indazole, 1-methylindazole and 2-methylindazole) have been determined. Ab initio calculations have been carried out for these six molecules and the corresponding cations, thus allowing the determination of protonation energies. Even the correlation between these quantities (-log K = 0.438+0.0744δΔEp) is far from perfect (r2 = 0.863), the order of basicity is the same. Aqueous basicities, pKa values, are totally uncorrelated.
TL;DR: In this paper, a relation lineaire entre le deplacement chimique 13 C du N-methyle and the resonance de l'azote-14 dans les sels de N-methyl pyridinium was established.
Abstract: Les deplacements chimiques du 13 C et du 14 N de vingt-trois sels de pyridinium substitues, incluant trois derives N-hydroxyles, ont ete mesures. L'effet des substituants sur les deplacements chimiques 13 C est discute au moyen de l'equation empirique de Paudler. Il existe une relation lineaire entre le deplacement chimique 13 C du N-methyle et la resonance de l'azote-14 dans les sels de N-methyl pyridinium.