Cyclodeshydration d'alcool-phenols induite par l'h.m.p.a. nouvelle voie d'acces aux dihydrobenzofurannes et dihydrobenzopyrannes

Substituted benzodihydrofurans and benzodihydropyrans 2 were obtained by heating alcohol-phenols 1 in HMPA. New cyclic alkyl phenyl dimethylaminophosphoramidates 3 were also isolated. Their thermolysis was studied. This and other considerations show that bis(dimethylamino)phenol alkyl phosphorodiamidate 4 and by-product 3 are intermediates of an alternative two or threestep reaction pathway. This mechanistic study gave indications on choice of best experimental conditions for this new cyclodehydration method.     

Une nouvelle voie d’acces aux indoles par condensation ylure-amide

Abstract-o-Acylaminobenzylidenephosphoranes lead to indoles in good yield by an intramolecular Wittig reaction with the amide carbonyl group. Mechanistic aspects are discussed. A general method is described for the synthesis of indoles from o-nitrobenzyl bromides and o-aminobenzyl alcohols.     

Ouverture d'epoxydes par des acides organiques dans L'H.M.P.T.: nouvelle voie d'acces a des desoxypentopyranosides

The opening of pyranic epoxides with organic acids in HMPA leads to regioselectively esterified methyl deoxy$\text{threo}$pentopyranosides; one of them is a convenient intermediate to provide $\text{erythro}$ isomers.     

Utilisation du borohydrure de sodium pour la reduction assistee de mesylates secondaires de diallylaminoglycosides ; nouvelle voie d'acces a la (=L)-daunosamine

Secondary mesylate in trans relationship with diallylamino group is reduced by means of a participation reaction affording deoxygenated aminoglycosides ; for one of them this reaction is a new pathway leading to (=L)-daunosamine.     

Ouverture acide de bis-(alkylthio)-2,2 cyclopropanols: Une nouvelle methode d'homologation et d'extension de cycle

Solvolysis of 2,2-bis(alkylthio) cyclopropanols by aqueous trifluoroacetic acid occurs easily to yield conjugated α-alkylthio emone and/or β-oxo-S alkylthioesters. The formation of the former most probably involves a disrotary rink opening concerted with the departure of the alkylthio group trans to hydoxyl, or, alternatively with monocyclic compounds, a 1,2-emigration of the same akylthio group synchronous with OH departure and cleavage. A nucleophilic substitution at the thioacetal centre followed by oxidative opening of the intermediate cyclopropandiol accounts for the formation latter. In 70% aqueous perchloric acid the formation of enones in favoured.     

Une nouvelle reaction de photooxydation: transformation de lactames et d'amides en imides et hydroperoxydes

Irradiation of an oxygen-saturated solution of N-methyl 2-pyrrolidone in t-BuOH leads to N-methylsuccinimide. This reaction can be applied to other lactams and amides (2,3,12–16) and gives the corresponding imide. Lactams 27, 28 and 31 which are substituted α to the nitrogen atom give α hydroperoxy or α hydroxyamides 29, 30 and 32. The benzophenone triplet regioselectively abstracts the hydrogen atom α to the amide nitrogen to give radicals which are then oxidized. The decomposition mechanism of the peroxy radicals is discussed.     

Derives de l'imidazo(2,1-b)thiazole—III : Transpositions au cours de la condensation d'acetylacetates d'ethyle α et ω halogenes avec l'ethylenethiouree

Rearrangement accompanies condensation of α and ω halogenated acetylacetic ethyl esters with 2-mercapto imidazoline, giving 5,6-dihydroimidazo(2,1-b) thiazoles with lateral chains substituted in position 2 or 3. ¹³C NMR was used to prove structures of rearranged products.     

Une nouvelle approche au calcul des diagrammes de phases

A numerical method for the calculation of the composition of two phases in equilibrium is proposed for the case when the composition of one of the phases is known as function of the temperature. The thermodynamic properties of the phases are not needed to be known in the proposed procedure. The feature of this approach is the possibility to use fictitious thermodynamic functions in the intermediate stages of computation. The method has been applied for calculation of solidus in phase diagrams of potassium-rubidium, potassium-cesium and cesium-rubidium systems from experimental liquidus data.

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Zusammenfassung Es wurde ein numerisches Rechenverfahren zur Berechnung der Zusammensetzung zweier im Gleichgewicht befindlichen Phasen für den Fall gegeben, daß die Zusammensetzung der einen Phase eine gegebene Funktion der Temperatur ist. Für das empfohlene Verfahren ist die Kenntnis der thermodynamischen Eigenschaften der Phasen nicht notwendig. Merkmal dieses Herangehens ist, daß während der Zwischenrechnungsschritte die Möglichkeit besteht, fiktive thermodynamische Funktionen anzuwenden. Das Verfahren wurde zur Berechnung des Solidus in Phasendiagrammen der Systeme Kalium-Rubidium, Kalium-Cäsium und Cäsium-Rubidium aus experimentellen Liquidusdaten angewendet.

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Remerciements—L'auteur exprime sa gratitude au Dr. V. Vassiliev pour la traduction de cet article en français.     

Synthese electrochimique de bipyrannylidenes une nouvelle voie d'acces a des systemes fortement donneurs

The electrochemical method is used in the easy synthesis of donating systems by means of the cathodic reduction of thiopyrones in the presence of alkyl halides.     

Complexes acetyleniques de titane(II). Reactivite vis-a-vis de l'hydrogene moleculaire: Une nouvelle approche du titanocene

¹³C NMR measurements were performed on [Re₃(μ-H)₃(CO)₁₀]^2? at various temperatures and field strengths. Selective decoupling allowed assignments of the carbonyl resonances. Spin-lattice relaxation time measurements indicated that two mechanisms, scalar coupling and chemical shielding anisotropy, contribute to the relaxation of carbon-13. Variable temperature experiments revealed that more than one mechanism is responsible for the fluxional behaviour.     

Stereochimie-LV : Etude cinetique de l'hydrocyanation d'enones cycliques

Kinetics of hydrocyanation of various enones are reported. The different behaviour of testosterone and 19-nor-testosterone towards hydrocyanation is explained by a slower partial rate factor on the α-face of testosterone.     

Stereochimie et mecanisme de l'ouverture par les amines d'ions N-alcoxypyridinium : Formation competitive d'un ylure endocyclique; application a une nouvelle conversion heterocyclique

The N-alkoxypyridinium salt 1, with pyrrolidine, piperidine and diethylamine, undergoes reversible ring opening in acetonitrile. This competes with irreversible cyclization of an ylide to the bicyclic intermediate 3 which suffers subsequent ring opening to 3-ω-aminobutadienylisoxazol-4 ones in methanol. The different courses of the reaction is tentantively explained by means of HSAB theory. Stereochemistry of the primary open products is consistent with a disrotatory ring opening of cis-dihydropyridine adducts resulting from amine addition to the salt 1 or to the bicyclic ion 3. These primary products are further isomerized and all-trans structures have been isolated in the case of isoxazoline derivatives. Conversion of an N-alkoxypyridinium salt to substituted butadienylisoxazolones exemplifies a new type of heterocyclic ring transformation that can be described by the PARC-ANRO sequence: Proton Abstraction, Ring Closure—Addition of a Nucleophile, and Ring Opening.     

Étude de l'erreur acide de l'électrode de verre en milieu aqueux: Tome II. Solutions d'acides purs

The acid error of glass electrode is studied in pure acid solutions of different natures by direct comparison with hydrogen electrode. This deviation from the hydrogen function is depending on the nature of both the acid involved and the glass electrode used. The potential of this electrode can be expressed by an empirical formula where two parameters appear: one of them is inversely proportional to molar weight of acid, while the other one is also dependent on the glass electrode used.