Synthèse et caractérisation du phosphate de hafnium comme échangeur d'ions

The preparation, crystalline structure, properties and behaviour of the hafnium bis (monohydrogen phosphate) monohydrate as a cationic exchanger have been studied. The crystalline product has been characterized by elemental analysis, X-ray Powder patterns, thermal analysis, photoelectron spectrometry and infra red spectroscopy. A layered structure in which the hafnium and phosphorus atoms are disposed in such a way as to form zeolitic-type cavities is suggested. The reversibility of the exchange with respect to sodium ions is discussed and can be related to the water content of the exchanger.     

Synthèse d'hétérocycles polycondensés à partir de benzopyranno-1 as-triazinones

From benzopyranno-1-as-triazinones 1 and 2 , chloro, hydrazino and aminobenzopyranno-1-as-triazinehsa ve easily been prepared by transformation of the carbonyl function. These compounds lead to triazolo and imidazolobenzopyranno-1-as-triazines by reaction with acids or α-bromoketones. Tetrazolotriazines have been obtained by reaction of sodium nitrite with hydrazinotriazines.     

Migration 1,2 d''un groupe triméthylsilyle au niveau d''un cation vinylique: synthèse de diènes conjugués silylés à partir de bis(triméthylsilyl)-1,4 alcynes-2

Alkyl -substituted 1,4-bis(trimethylsilyl)-2-alkynes react with electrophilic reagents to give silylated conjugated dienes, which result from a 1,2-shift of a trimethylsilyl group to a vinylic cationic center.     

Synthése totale d'α-disaccharidyles de tridésoxy-2,5,6-streptamine apparentés aux aminosides à partir du maltose et du lactose

Total synthesis of α-disaccharidyl-2,5,6-trideoxy-streptamines related to aminoglycoside antibiotics derived from maltose and lactose The synthesis of the hitherto unknown 4-O-substituted α-linked pseudo-tri-saccharides 1,2 and 3 is described. The key intermediates required in the reaction sequence are the glycals 12, 13 and 14 , prepared from maltose, lactose and the chiral ditosyloxy-cyclohexanol 15 , readily accessible from quinic acid. The pivotal step in the reaction's scheme - a stereospecific α-glycosylution procedure -, is an acid-catalyzed addition of the alcohol 15 to the glycals 12, 13 and 14 leading to the corresponding 2,3-unsaturated trisaccharides. The latter compounds were transformed to the target α-glycosides of 2,5,6-trideoxystreptamine 1, 2 and 3 which were devoid of significant antibacterial activity. These results indicate that the presence of an ether linkage at the position 4′ is probably critical for antibacterial activity.     

Synthèse de nouveaux polyesters insaturés styrèniques à partir de diols isomoléculaires à ponts thio-éthers. Étude par RMN et tenue thermique

The synthesis of unsaturated polyesters cross-linked by means of styrene have been carried out from high isomolecular weight diols containing thio-ether bonds. The ¹H-NMR peaks have been attributed. Those polyesters exhibit softness to a certain extent in conjunction with relatively high degradation temperatures (T_d 400°C).     

Sur la synthèse du pollinastanol à partir du cycloartanol

The partial synthesis of pollinastanol (14) from cycloartanol (3) is reported. The transformation proceeds through the methylenic intermediate 12; the ring enlargement with cyanogen azide affords pollinastanone (13) further reduced to 14, The 4-keto isomer of pollinastanone (17) as well as a series of 5-β isomeric compounds are also described.     

Synthèses d'hétérocycles indoliques à partir de dérivés carbonylés de l'indole et du pyrrole

The reactions of ethyl azidoacetate with 1-methylindole-2-3-dicarboxaldehyde (1) and its monoacetal 2 afforded β and γ carbolines. The regioselectivity of condensation of ethy6l aminoacetate with 1 was investigated and yields a γ-carboline. Derivatives of a new heterocycle, the thiepino[4,5-b]indole and its application of the synthesis of some carbazoles are described.     

Synthèse du virensate de méthyle

Synthesis of Methyl Virensate The synthesis of methyl virensate (=methyl 4-formyl-3,8-dihydroxy-1,6,9-trimethyl-11-oxo-11H-dibenzo-[b, e][1,4]dioxepin-7-carboxylate; 18 ) by the condensation of the substituted β-orcinol and orcinol units 9 and 10 followed by formylation and demethylation of the depsidone 13 is described.     

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.     

Synthèse et réactivité de dihydrotriazines et de dihydrotriazolotriazines

Generally, 4,5-dihydro-3triazinones have been prepared by a basic hydrolysis of 3-methylmercapto-4,5-dihydrotriazines. Of the serveral methylation methods, namely, diazomethane, methyliodide, dimethyl sulfate all in the presence of sodium methylate or silver carbonate, only methyl bromide in the presence of phase transfer catalyst was sucessful in producing all of the N-2 and/or N-4 methylate compounds. Two unequivocal syntheses of dihydrotriazolo[4,3-b]triazine are reported.     

Sels d'aziridinium stables C-fonctionnalisés III: Synthèse et caractérisation d'aziridines protonées épimères à l'azote

Aziridinium ions were prepared from aziridines bearing a functionality on a ring carbon and as isolated crystalline fluorosulfate salts either by protonation in fluorosulfuric acid solution or by alkylation with methyl fluorosulfate. The structural assignement of these ions is based on nmr spectra and on quenching experiments with sodium carbonate. The configurations of the epimeric ions have been assigned by the nuclear Qverhauser effect and the stereoselectivity in protonation is disucussed.     

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.     

Synthèse d'azido dithiényl-1,2 éthènes et éthanes

Two convenient preparations of azido-1,2-dithienylethenes are described. The synthesis of azido-1,2-dithienylethanes proceeds via metalation (n-Buli) and subsequent treatment by tosylazide of bromo-1,2-dithienyl-ethanes. The structures of the obtained derivatives were established on the basis of ¹H nmr, ir, and mass spectral data.