Intramolecular meerwein reactions of the anthraquinone system. Synthesis,X-ray structural analysis and spectroscopic properties of anthra[9,1-bc:10,5-b'c']tetrahydrodipyran derivatives

Meerwein reactions of 1,5-anthraquinone bis(diazonium hydrogen sulfate) with sufficiently activated olefins, such as acrylonitrile, acrylic esters, methacrylonitrile and its esters, styrene and α-methylstyrene yielded derivatives of the new heterocyclic system anthra[9,1-bc:10,5-b'c']-2,3,7,8-tetrahydrodipyran. Isolation of derivatives was realized and yields enhanced by using dimethyl methylphosphonate as reaction medium. Compounds 5–18 were isolated as mixtures of diastereomers, some of which were separated by crystallization. Proof of structure and stereochemistry was obtained for some of the compounds by X-ray crystallographic analysis. The ¹H- and ¹³C-nmr data provided further support. Surprisingly large chemical shift differences between some of the proton signals of isomers were observed although the two asymmetric centers are far apart through bonds and through space. The mechanism of formation is explained on the basis of redox modulation of a charge transfer complex in which the aliphatic radical attacks the oxygen atom of the anthraquinone. It is proposed to classify this new type of reaction as an intramolecular Meerwein reaction.     

Azo initiators for the preparation of hydroxyl-terminated polybutadienes

Azo compounds such as di(4-hydroxybutyl)-2,2′-azobisisobutyrate, di(3-hydroxybutyl)-2,2′-azobisisobutyrate, di(2-hydroxypropyl)-2,2′-azobisisobutyrate, and di(2-hydroxyethyl)-2,2′-azobisisobutyrate were prepared and used as initiators for the preparation of hydroxyl-terminated polybutadienes (HTPBs) of molecular weight (M?_n) ranging from 2000 to 7500 and functionality between 1.90 and 3.0. The polymers were prepared by free-radical solution polymerization in dioxane and toluene. The polymers obtained were characterized for their molecular weight, hydroxyl number, functionality, and instrinsic viscosity.     

Modellrechnungen zum Dendriten-Wachstum in partiell-kristallinen Hochpolymeren

Zusammenfassung Überstrukturen in partiell-kristallinen Thermoplasten liegen oft in Gestalt von Sphärolithen vor. Es wird versucht, ihre Entstehung auf behindertes Dendritenwachstum zurückzuführen. Die durch das Simulationsmodell beschriebenen Strukturen werden mit experimentell beobachteten verglichen.

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Superstructures in partial-crystalline thermoplastics often show the shape of spherulites. The reason of this can be a handicapped growth of dendrites. The structures obtained by a simulation model are compared with those obtained by experiments.

     

Photocycloadditions to 3-phenyl-1,2-benzisothiazole

Photocycloaddition reactions of 3-phenyl-1,2-benzisothiazole alkenes yield derivatives of 2,3-dihydro-1,4-benzothiazepine in one step reactions. The photoadditions are both regio and stereospecific.     

Transposition des oxirannes-ethanols par l'intermediaire d'alcoxyetains. Influence de la configuration de l'oxiranne

The transposition of oxirane-ethanols, through alkoxytin compounds, into oxetane-2-methanols and/or oxolan-3-ols (tetrahydrofuran-3-ols) is dependent upon the oxirane configuration. Cis configuration is more suitable for the formation of the smallest ring. Steric hindrance is not sufficient enough to explain the results.     

Aktivierungsanalytische Sauerstoffbestimmung mit schnellen Reaktorneutronen

Summary Oxygen can be determined by the nuclear reaction ¹⁶O (n, p) ¹⁶N initiated by fast reactor neutrons. The automatic irradiation and counting system which is used in the Munich research reactor for non-destructive oxygen determination is described. The activation by thermal neutrons is suppressed by the installation of a cadmium shield around the pneumatic tube at the irradiation position. Oxygen has been determined in the presence of many elements to find out which elements disturb the oxygen activation analysis.Zusammenfassung Sauerstoff läßt sich aktivierungsanalytisch mit schnellen Reaktorneutronen über die Kernreaktion ¹⁶O (n, p) ¹⁶N bestimmen. Die automatische Bestrahlungs- und Meßanlage, die die Durchführung solcher zerstörungsfreier Sauerstoffanalysen am Forschungsreaktor München erlaubt, wird beschrieben. Die Aktivierung durch thermische Neutronen wurde durch Einbau eines Cadmiumschildes am Bestrahlungsort unterdrückt. Sauerstoffanalysen wurden in Gegenwart zahlreicher Matrixelemente durchgeführt, um zu ermitteln, welche Elemente die aktivierungsanalytische Sauerstoffbestimmung mit schnellen Reaktorneutronen erschweren oder unmöglich machen.Wir danken der Betriebsleitung und der Bestrahlungsgruppe des FRM für deren verständnisvolles Eingehen auf unsere Wünsche, Herrn Dr. Köhler für seine wertvollen Hinweise beim Aufbau der schnellen Rohrpost und Herrn E. Pfeffermann für seine Mithilfe bei einem Teil der Messungen.