Etude de la décomposition thermique d'azido dithiényl-1,2 éthènes et éthanes

Thermal decomposition of azido-1,2-dithienylethenes 1 gave thienyl 4H-thieno[3,2-b]pyrroles 3 . For the 3,4-disubstituted thiophene derivatives 2 , the same reaction led to the amino-1,2-dithienylethenes 4 . In contrast, only azido-1,2-dithienylethanes 7 led to thienyl-5,6-dihydro-4H-thieno[3,4-b]pyrroles 8 . The structure of the obtained derivatives was established on the basis of ¹H nmr, ir, and mass spectral data.     

Polymérisation radicalaire du pentadiène-1,3. II. Microstructure des résidus pentadiéniques dans les homo- et copolymères des cis et trans pentadiènes-1,3 avec l'acrylonitrile

The microstructure of diene units was investigated in radical homopolymers of the cis and trans isomers of 1,3-pentadiene and copolymers with acrylonitrile, synthetized in bulk and emulsion. Experiments were carried out by infrared spectroscopy, 100 MHz ¹H-NMR, and 25 MHz ¹³C-NMR studies. No difference between the bulk and emulsion samples was noted. The microstructure of poly(1,3-pentadiene) is practically independent of the cis or trans configuration of the diene monomer and is as follows: 56–59% trans-1,4, 15–17% cis-1,4, 16–20% trans-1,2 7–10% cis-1,2 and 0% 3,4. On the other hand, up to about 30% of incorporated acrylonitrile (10% in the feed), the microstructure of the pentadiene fraction in the copolymers is not affected. This finding suggests that the penultimate unit has very little influence on the polymerization process involving the terminal pentadienly unit. Beyond 10% of acrylonitrile in the feed, the proportions of the structural units were linearly dependent upon the acrylonitrile content: trans-1,4 content increased whereas the amounts of cis-1,4 trans-1,2 and cis-1,2 decreased (except the cis-1,2 fraction, constant in the copolymers from the cis-diene). These results are discussed on the assumption that the microstructure of pentadiene residues is strongly associated with the acrylonitrile comonomer in the feed.     

Fluorénacènes et fluorénaphènes Synthèses dans la série des indéno-fluorènes,XIX Dérivés tétraméthylés du trans-fluorénaphène et du trans-fluorénacène

By condensation of isophthaloyldichloride resp. of terephthaloyldichloride with 4-bromo-1,2-xylene according Friedel-Crafts, followed in each case by a double cyclisation and a final reduction, the 2,3,9,10-tetramethyl-7,12-dihydro-indeno[1,2-a]fluorene resp. the 2,3,8,9-tetramethyl-6, 12-dihydro-indeno[1,2-b]fluorene are synthesized.     

Systèmes aromatiques à 10 électrons π dérivés de l'aza-3a penlalène. VIII. Recherches dans la série du pyrazolo[3,2-c]-s-triazole

It has been shown that the reaction of β-ketoesters with 1,2-diamino-1,3,4-triazoles affords pyrazolo[3,2-c]-s-triazoles. These results induces us to propose a 7,8-dihydro-9H-s-triazolo[4,3–6]-[1,2,4] triazepin-8-one structure for the intermediate in this synthesis.     

Synthèse de sucres aminés ramifiés III. Synthèse et réactions de 1′α-amino-nitrile dérivé du di-O-isopropylidène-1,2:5,6-α-D-ribo-hexofurannosul-3-ose

The addition of cyanohydric acid to 1,2:5,6-di-O-isopropylidene-α-D -ribo-hexofurannos-3-ulose can be sterically controlled. Under kinetic conditions, the allo cyanohydrine epimer is formed, under thermodynamic conditions, the gluco epimer is formed. The configuration of these two products is proved by their chemical reactions. Hydration followed by hydrolysis of the nitrile group of the allo epimer (O-acetyl derivative) gives the 3-C-carboxy-1,2-O-isopropyloidene compound. This product forms the corresponding γ or δ-lactone with hydroxyl ( 5 ) or ( 6 ). On the other hand, after hydrolysis of 5,6-isopropylidene, the 3-O-acetyl derivative of the gluco epimer gives an acetyl migration from position 3 to position 5 and finally to position 6. By reaction of the allo epimer with NH₃ and CN^?, an aminonitrile is formed. The allo configuration is deduced from the above mentioned reaction and from IR. and NMR. data. Several acetylated and trifluoracetylated derivatives of these products are described. The oxidation of the nitrile group to the amide group is possible with both epimeric cyanohydrines and the amino-nitrile.     

Synthèse de nouveaux types de dérivés C-glycosyliques à partir de sucres acétyléniques ou de leurs équivalents synthétiques partiels

Synthesis of Novel Types of C-Glycosyl-derivatives from Acetylenic Sugars or Partial Synthetic Equivalents thereof The concept of synthetic equivalent is not unequivocal and, for example, α-fluoroenamines may behave in some cases as synthetic equivalents of ynamines and, in other situations, quite differently. Some uses of these α-fluoroenamines, ‘partial synthetic equivalents’ of ynamines, for the synthesis of C-glycosyl derivatives of coumarins, chromones, quinolines, quinolones, thietenes and isoxazoles are described. We also report the preparation of a series of mono- and diglycosylthiophenes by reacting HS^? with mono- and diglycosylbutadiynes. Acetylenic sugar derivatives have also been used for the synthesis of a diglycosylazaphosphorine and a spirooxolenone.     

Dérivés de sucres à groupement gem-dihalogénoéthényle

Carbohydrate Derivatives Bearing a gem-Dihalogenoethenyl Group Treated with the appropriate Wittig reagent, aldehydosugar derivatives ( 1–13 ) led in good to excellent yields to the expected gem-difluoro, gem-chlorofluoro-and/or gem-dichloroenoses ( 14–29 ). Examples of their dibromo analogues had been previously described (see e.g. [1]) but the diiodo derivatives could not be isolated, The influence of the conditions on the yields is reported as well as spectroscopic properties (particularly the long-range ¹³C, ¹⁹F- and ¹H, ¹⁹F-coupling constants) of these new enoses.     

Biosynthèse de la farnésylacétone-(E,E) par les glandes androgènes du crabe carcinus maenas

Biosynthesis of E, E-farnesylacetone by the andogenic glands of the crab Carcinus maenas Using sodium acetate-1,2-[¹⁴C] or mevalonic acid-2-[¹⁴C], the biosynthesis of (E,E)-farnesylacetone 1 by the androgenic glands of the crab Carcinus maenas, kept as organ subculture is demonstrated. Ozonolysis of the NaBH₄ reduction product 3 leads to three fragments the radioactivity of which has been measured after isolation by GC. It is thus established that the biosynthesis of 1 proceeds through geranylgeraniol. The hexahydroderivative 2 is not labelled in the two experiments.     

Synthèse électrochimique du cycle époxydique. Communication préliminaire

The polarographic behaviour of ditosyloxy alkanes TsO(CH₂)_nOTs in aprotic medium suggests that intramolecular cyclisation takes place after reductive cleavage of a single SO₂? O bond at the dropping electrode. This hypothesis was verified by controlled potential electrolysis of the lower homologues at a mercury cathode. High yields of epoxy compounds are obtained by this method.     

Isomérisations en chimie des sucres. II Fermetures de cycles par attaque nucléophile intramoléculaire sur des carbones sp2 à caractère électrophile: Furannoses hybridés sp2 en C3

When heated with one equivalent of H₂O, the 1,2: 5,6-di-O-isopropylidene-α-D-ribo- and -xylo-hexofuranos-3-uloses loose one molecule of acetone and yield the 3, 6-anhydro-1, 2-O-isopropylidene-α-D-ribo- and -xylo-hexofuranos-3-ulose ketohydrols. The carbonyl group of the starting material seems to provide some kind of intramolecular electrophilic assistance to the hydrolysis of the 5, 6-O-isopropylidene group. When the oxygen of the carbonyl group is replaced by cyanomethylene, an analogous cyclisation takes place under base catalysis, provided that C6 bears a free hydroxyl group.     

Résonance Magnétique Nucléaire en phase nématique. Exploration de la barrière d'empêchement à la libre rotation pour le fluorure d'acroyle et l'acroléine

The NMR spectrum of acrolein and acroyl fluoride (CH₂?CH? COX with X?H and F) oriented in a nematic phase has been measured and information about conformational equilibrium s-cis ? s-trans has been obtained. The barrier to internal rotation of the COX group has been studied with various hypotheses. Good agreement between experimental and calculated spectra has been obtained using the potential equation V(?) = Σ_nV_n(1 – cos n?)/2, with V₁ = ?200 cal mol^?1, V₂ = 1500 cal mol^?1 and V₃ = 400 cal mol^?1 for the fluorine compound, and V₁ = 1200 cal mol^?1, V₂ = 3000 cal mol^?1 and V₃ = 2000 cal mol^?1 for acrolein; this last compound is found to be mostly in the s-trans conformation.     

Fluorénacènes et fluorénaphènes Synthèses dans la série des indéno-fluorènes XIV [1] Nouvelle synthèse du trans-fluorénacène

A new synthesis of 6, 12-dihydro-indeno [1,2-b] fluorene (trans-fluorenacene) in 9 steps starting from fluorene (overall yield 24,5%) is recorded. By partial oxidation of the hydrocarbon its 6-oxo derivative is also obtained.     

Utilisation d'ylides du phosphore non stabilisés en chimie des sucres VI. Sucres ramifiés dérivés des di-O-isopropylidène-1,2:5,6-α-D-ribo-et-α-D-xylo-hexofurannosul-3-oses

The cis and trans isomers of 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methylthiomethylene-α-D -xylo- and -α-D -ribo-hexofuranoses have been prepared by treatment of 1,2:5,6-di-O-isopropylidene-α-D -xylo- and -α-D -ribo-hexofuran-3-uloses with methylthiomethylene-triphenylphosphorane. Configurations are assigned by NMR. A new type of ⁴J is described. Hydrogenation-desulfurization of the methylthiovinylic sugars affords 3-deoxy-3-methyl sugars of the D -allo, D -gulo, and D -galacto series. Derivatives of 3-deoxy-3-methyl-D -lyxose and 3-deoxy-3-methyl-D -ribose are prepared by chain-shortening of derivatives of the corresponding 3-deoxy-3-methyl-hexoses.     

Utilisation d'ylides du phosphore en chimie des sucres,X. Synthèse stéréospécifique de l'épimère en C3 du streptose et d'autres sucres ramifiés,dérivés de désoxy-5-pentoses, à groupements gem-hydroxy-formyle ou gem-hydroxy-hydroxyméthyle

The synthesis of branched-chain sugars of the gem-hydroxy-formyl and the gem-hydroxy-hydroxymethyl types is described. A 5-deoxy-1,2-O-isopropylidene-furanos-3-ulose is treated with cyanomethylene-triphenyl-phosphorane, yielding the two geometrical isomers of the corresponding branched-chain unsaturated sugar. Cis-dihydroxylation(KMnO₄) of these cyanomethylenic compounds affords stereoselectively and in high yield the gem-hydroxy-formyl branched chain sugars whose formyl group is on the more hindered face of the furanose ring. The hydroxymethyl analogues of the latter compounds are readily prepared by their borohydride reduction. This method constitutes a new general route to type A branched-chain sugars epimeric at the branching-point with the sugars which would have been obtained by the classical procedure involving Grignard reagents.     

Résonance Magnétique Nucléaire en phase nématique. Exploration de la barrière d'empêchement à la libre rotation de la monofluoroacétone

The NMR spectra of monochloro-, monobromo- and monofluoroacetone (CH₃? CO? CH₂X with X = Cl, Br, F) oriented in a nematic phase have been measured and the direct dipolar coupling constants determined. The barrier to internal rotation for the CH₂F group has been studied for fluorine compound using various hypotheses. The best agreement with IR data has been obtained using the potential equation V(θ) = Σ_n V_n × (1 – cos nθ)/2 and a Boltzmann distribution of the CH₂F group (V₁ = 250 ± 50 cal.mol^?1, V₂ = 1650 ± 100 cal.mol^?1, V₃ = ?1000 ± 100 cal.mol^?1).     

Identification de stérols à chaîne latérale oxygénée dans une éponge de l'espèce Hyrtios

Thirty-two sterols are identified in the sponge Hyrtios sp. In addition to fourteen monohydroxylated compounds, the sterol fraction contains eight functionalized sidechain sterols, three of them new: 3 β-hydroxy-24-norchol-5-en-23-al (19) , (22-trans)-3 β-hydroxycholest-5, 22-dien-24-one (20) and (22R, 23R, 24S) or (22S, 23S, 24S)- 22,23-epoxy-24-methylchoest-5-en-3 β-ol (24). The probable biological origin, rather than artifact production, of these undescribed components is discussed.     

Propriétés électriques du trioxyde de tungstène a proximité de sa composition stoechiométrique. Influence des conditions thermodynamiques de préparation et phénomènes de trempe

The experimental study of variations in electrical conductivity of WO_3−x vs oxygen partial pressure and temperature shows evidence of interstitial W⁶_i· as being the major defect. Under certain conditions, point defects can order themselves in extended defects. The behavior of electrical conductivity can be interpreted in terms of thermodynamic equilibrium between point defects and extended defects, the latter leading to structural modifications beyond a certain departure from stoichiometry. Moreover, WO_3−x shows evidence of quenching phenomena allowing it to keep electrical features characteristic of high temperatures down to room temperature. These properties may explain discrepancies between previous data.     

Réactions de substitution nucléophile de l'hydroxyurée. Synthèse et étude des oxa-6 dihydrouraciles

Hydroxyurea, an N-protected hydroxylamine, reacts with α-bromoesters to give α-ureidoxyesters. Some of these have been isolated. Their cyclisation is a synthetic route to 6-oxadihydrouraciles which structure has been well established by means of physicochemical methods. Especially, ¹³C nmr spectroscopy has been used to show only the presence of the diketone tautomeric form.     

Equation de Karplus appliquée à des systèmes sp2–sp3

A method of best fitting for the calculation of vicinal coupling constants is presented for sp²-sp³ systems. Results for 68 vicinal coupling constants from 32 different products are presented. We obtain the best Karplus-type equation to date with a dispersion factor of 31,01%.     

Pyrazines. 2ème communication [1]. II. Synthèse de dihydro-6,7-5H-cyclopenta[b]pyrazines alkylées

Alkyl-5H-6,7-dihydrocyclopenta[b]pyrazines are prepared by condensation of cyclopentenolones with alkylenediamines or of aliphatic α-diketones with 1,2-diaminocyclo pentanes. Products so obtained were dehydrogenated using palladium on activated charcoal, or copper chromite. NMR. and mass spectra are given for 21 bicyclic pyrazines and intermediates, and their IR. spectra are compared.