Stabilité dans le méthanol et propriétés thermodynamiques de transfert des cryptates de certains cations de transition et de métaux lourds

Stability in Methanol and Thermodynamic Transfer Properties of the Cryptates of some Transition Cations and Heavy Metals The nature and stability of the macrocyclic and macrobicyclic complexes of Ag⁺, Cd²⁺, and Pb²⁺ (Mⁿ⁺) with 21, 22, 211, 221 and 222 in anhydrous methanol 0.05M in Et₄N⁺ClO^?₄, at 25° (see Scheme) have been determined by potentiometry and spectrophotometry. Binuclear complexes M₂L²ⁿ⁺ have been observed in all cases, besides the mononuclear MLⁿ⁺ complexes. The macrobicyclic 1:1 complexes MLⁿ⁺ exhibit an important ‘cryptate effect’ with Mⁿ⁺=Ag⁺, Pb²⁺ and Cd²⁺, but not with Cu²⁺ and Zn²⁺; their stability is in all cases maximum with 221. The applicability to our results of the recent extrathermodynamic hypothesis involving MLⁿ⁺ cryptates is examined.     

Etude par spectrométrie de masse de l'ionisation de benzonitriles,de phénylacétonitriles et de N,N-diméthylanilines substitués

Molecular ionization potentials for series of compounds of the type X? C₆H₄? CN, X? C₆H₄CH₂? CN and X? C₆H₄? N(CH₃)₂ have been measured using the retarding potential difference technique (RPD. technique). The effect of the various substituents X is better correlated through the electrophilic Brown σ_p⁺ constants than through Hammett's σ_p values. No meta-para orientation effect is observed. For all the disubstituted phenyl compounds studied, the effect of the second substituent is affected by the electron-releasing power of the original substituent. Ionization potentials calculated by using the semi-empirical method of equivalent orbitals are in good agreement with the experimental values.     

Sur le mécanisme de la réaction de meth-cohn-tarnowski de préparation des thiocoumarines

Reaction of 2-t-butylthiobenzaldehyde with N-(2-dialkylaminoethyl)-cyanacetamides followed by heating of the resulting 3-(2-t-butylthiophenyl)-2-cyanoacrylamides in polyphosphoric acid leads to the formation of 3-carboxamido-2-imino-2H-benzo[b][l]thiopyrann intermediates which afford thiocoumarins on hydrolysis. The authors postulate the intermediate formation of a thiophenate ion by an electronic mechanism involving six centers.     

Nouveaux exemples de radicaux libres stables de dérivés hétérocycliques de sucres. Communication préliminaire

Some more examples of stable free radicals of carbohydrate heterocyclic derivatives 2-Glycosyl-4,4,5,5-tetramethylimidazoline- 3-oxide-1-oxyls and 2-glycosyl-4,4,5,5-tetramethylimidazoline 1-oxyls have been prepared in nine carbohydrate series, which proves the generality of the method. The hyperfine coupling constant between the free electron and the α-proton of the glycosyl group is never very large (0-2.3 G) but a correlation between its value and the structure of the aglycone has been noted. Free radicals of that type, stable in aqueous solutions, are potentially interesting for biological studies.     

Synthèse de l'analogue sélénié de la sérotonine

Starting from 2-bromo-5-methoxyacetophenone, an unambiguous synthesis of the selenium analog of serotonine is described with a 25% overall yield. Application of the Wittig reaction to selenoindoxyls appears to be a successful pathway to products of this nature.     

Application de la réaction de Wittig à la synthèse de dérivés de bromoénosuloses et d'esters bromoénuroniques. Note de laboratoire

Use of the Wittig reaction for the synthesis of derivatives of bromoenosuloses and bromoenuronic esters Treatment of 3-O-benzyl (or 3-O-methyl)-1, 2-O-isopropylidene-α-D -xylo-pentodialdo-1, 4-furanoses ( 2 or 1 ) with acetylbromomethylidenetriphenylphosphorane ( 3 ), benzoylbromomethylidenetriphenylphosphorane ( 4 ) or bromoethoxycarbonylmethylidenetriphenylphosphorane ( 5 ) gave in good to excellent yields the expected enose ( 6--11 ). In all cases but one ( 8 where some 10% of the E-isomer was formed) the reaction led to the exclusive formation of the Z-isomer whose configuration was established by NMR.     

Spectres de rotation de la molécule de chlorobenzène : II. Variétés isotopiques multisubstituées et structure géométrique précise

In order to complete the r_s structure of chlorobenzene given in a preceding paper, a variety of isotopic species of this molecule were synthesized and their microwave spectra studied. This made twenty isotopic species available, enabling the determination of the geometrical parameters by a least squares method. Fitting only differences of moments of inertia either for monosubstituted species or to multiply substituted species gave the same result. They hardly differ from the r_o values and agree with the r_s values obtained by the Kraitchman equations. The resulting error limits were reduced, however.

The following structural parameters were obtained, C₁C₂ = 1.399 Å, C₂C₃ = 1.386 Å, C₃C₄ = 1.3976 Å, C₁Cl = 1.7248 Å, C₂H₂ = 1.080 Å, C₃H₃ = 1.081 Å, C₄H₄ = 1.081 Å, C₆C₁C₂ = 120° 16, C₁C₂C₃ = 119°78, C₂C₃C₄ = 120°24, C₃C₄C₅ = 119°80, C₁C₂H₂ = 119°45, C₂C₃H₃ = 119°76.

The structure of the ring differs significantly from C₆ symmetry. The deformation can be regarded as a compression of the position C₁ while the angle of C₂H₂ bond is also changed.     

Synthèse par cyclisation nucléophile de dérivés de sucres portant un hétérocycle inséré en spiro. Note de Laboratoire

Synthesis of Sugar Derivatives Bearing a Spiro Heterocycle via Nucleophilic Cyclization Treated with the 1,4-binucleophiles 1,2-diaminoethane, 2-aminoethanol, 2-aminoethanethiol, L -cysteine, o-phenylenediamine, o-aminophenol or o-aminothiophenol the ketosugar derivative 1 gave in good yields the corresponding spiro derivatives 2–8 . In each case, the reaction was stereospecific leading to the isomer bearing the N-atom on the endo face of the bicyclic starting material. Starting from the sugar enone 9 , the aromatic 1,4-binucleophiles led stereospecifically to the spirobenzo [b]-diazepine 10 , -oxazepine 11 or -thiazepine 12 . In one case, an imine (13) was isolated. As 13 cyclized to 6 , the intermediate formation of these kind of derivatives could be considered as a common step for all these reactions.     

Spectres photoélectroniques de la dithiole-1,3-thione-2 et de son dérivé benzosubstitué

The photoelectron spectra of 1,3-dithiol-2-thione and its benzo-substituted derivative have been analysed in terms of orbital interactions. Comparison of the P.E. spectra of these compounds and ethylene trithiocarbonate and 2-methyl, ethyl-benzo-1,3-dithiol permitted the influence of the spatial configuration of molecules and of the C=S group on the electronic structure of these cycles to be evaluated.     

Obtention de phosphore élémentaire et de phosphures de nickel par électrolyse de solutions de pentoxyde de phosphore dans des bains à base de cryolithe

By electrolysis of cryolitic solutions of P₂O₅, elementary pure phosphorus is obtained on carbon cathode and Ni phosphides on Ni cathode. The most probable mechanism of phosphorus formation in these conditions seems to be the final dissociation of P₂O₅ in P⁵⁺ and O^2? and the primary electrodic discharge of these ions.     

Substitution électrophile aromatique dans l'anhydride sulfureux liquide. Etude cinétique de la réaction de bromation d'anisoles monosubstitués. Transmission des effets électroniques et caractéristiques de l'état de transition

Reactivity-structure correlations for anisole and eleven of its substituted derivatives established from bromination rate constants in liquid SO₂, unlike observations in water, show the reaction to be highly sensitive to substituent effects, (ρ = ?7.1; ρ = ?10.51). This result is ascribed to the solvation of the methoxy group which decreases the conjugation of para-substituted (ρ = ?9.70) compared to that of ortho-substituted derivatives (ρ = ?8.86). The highly solvated transition state lies far from reactants on the reaction coordinate and the positive charge developed in this state is nearly unity.     

Etude par RMN. de polyaminocarboxylates de terres rares,III. Hydroxyéthyliminodiacétates de praséodyme

¹H—NMR. has been used to study the chemistry of the hydroxyethyliminodiacetate complexes of praseodymium in aqueous solution. The ligand exchanges by spontaneous dissociation of the metal-bis-hydroxyethyliminodiacetate (1:2 complex) and of the metal-bis-hydroxyethyliminodiacetate hydroxocomplex, by acid catalysed dissociation of the 1:2 complex, and by a bimolecular process involving the free ligand and the 1:2 complex or the ternary hydroxo-complex. The ligand exchange rate constants are given and the mechanisms discussed.     

Constantes d'acidité de quelques bihétérocycles

The pKa₁ and pKa₂ of 19 biheterocycles A-(CH₂)-n B(in which A and B represent pyrazole, imidazole, or pyridine rings, and n=0 or 1) were determined in water at 25° using poterntiometry and UV spectroscopy methods.     

Etude de la fragmentation par impact électronique en ions positifs et négatifs de dérivés nitrés de l'amino-2-benzothiazole

Study of Positive and Negative Ions Electron Impact Fragmentation of 2-Amino-benzothiazole Nitro Derivatives The positive and negative ions mass spectra of 2-amino-4,6-dinitrobenzothiazole ( 1 ), 2-amino-4-nitrobenzothiazole ( 2 ), 2-amino-6-nitrobenzothiazole ( 3 ) are reported and discussed. These compounds give an intense molecular ion and show interesting fragmentations in both positive and negative ions spectra. Specific ¹⁵N-labelling was used in order to confirm the fragmentation patterns.     

Préparation de quelques 4-nitroisoxazoles à partir de pseudonitrosites de cétones éthyléniques du type chalcone

The Synthesis of some 4-Nitroisoxazoles from Pseudonitrosites of Chalcones The action of dinitrogen trioxide with α,β-unsaturated ketones of the chalcone type leads to pseudonitrosites (Table 1) which are cyclized to 4-nitro-3,5-diarylisoxazoles (Table 2).     

Spectrographie de Masse de Diazastéroïdes Possédant le Motif Tétrahydroisoquinoléique

We have determined the characteristic fragmentations in a series of 3,4-dihydroisoquinoline and of 8,13 diazaestrones, with the aid of metastable ions, ‘simili’ mass analysed ion kinetic energy spectra (E/V² constant) and some deuterated compounds. In the diazasteroidal series, we could distinguish three essential types of fragmentation, as well as preferential abstraction of the hydrogen situated on the 14-carbon.     

Régiospécificite et stéréosélectivite de la cycloaddition de l'oxyde de benzonitrile sur la phényl-5 A-3-pyrazoline

An example of stereospecific and stereoselective reactions is described concerning the cycloaddition of benzonitrile oxyde with 1,2-dimethyl-5-diphenyl-3-pyrazoline. The structure of the two epimeric 5,6-dimethyl 3,4-dimethyl[4,3-d]pyrazolidinoisoxazo-lines-2 was proved by the means of chemical and physical methods. The conversion of one epimeric product to another more stable is achieved and discussed.     

Substitution directe de l'azote N-9 de la théophylline

In alkaline medium, 8-(2-chloroethyl)aminotheophylline (1) cyclizes into two imidazopurines: the imidazo[1,2-e]purine (2A) (cyclization on 9-N) and the imidazo[2,1-f]purine (2B) (cyclization on 7-N). The structure of each compound was determined by an unambiguous synthesis and confirmed by spectrographic methods. Synthesis of one pyrrlo[2,1-f]purine, a novel heterocycle, is described.     

Préparation de dithiényl-2-éthène-1,2, de dithiényl-2-pyrimidine-2,4 et de dithiényl-2-pyridazine-3,6

The condensation of 2-thienylmagnesium bromide with (Z)-1,2-dichloroethene 2,4-dichloropyrimidne, 3,6-dichloropyridazine and with a transition metal catalyst is described. The yields of these reactions are very good; 1,2-bis(2-thienyl)ethene and two new heterocyclic compounds 2,4-bis92-thientyl)pyrimidine and 3,6-bis(2-thienyl)pyridazine were obtained in one step from commercial products.     

Oxydations et halogénations régiosélectives et réactions carbéniques de dérivés de sucres portant un groupement thioéther

Regioselective Oxidations, Regioselective Halogenations and Carbene Reactions of Sugar Derivatives Bearing a Thioether Group Regioselective stoechiometrically controlled procedures are described for the oxidation of thiosugars either at the sulfur atom (to sulfoxides or sulfones) or at a hydroxymethylene group (to ketosugars). Ruthenium tetraoxide reacted at both sites. Chloration (SO₂Cl₂) of β-ketothioether sugar derivative 3 took place exclusively at C(6). Evidence is given that a chlorosulfonium intermediate C was formed when the dichloroketothiosugar derivative 6 was treated with SO₂Cl₂. The carbene generated from the tosylhydrazone 16 rearranged to the enoses 17–20 , the migrating group coming in equal proportions from C(4) and C(6). Some stereochemical aspects of these reactions are discussed.