Efficient preparation of (Z)-alkenyl derivatives from (Z)-vinyl (N,N-diisopropyl)carbamate via Ni-catalysed coupling reactions

A (Z)-vinyl (N,N-diisopropyl)carbamate treated with Grignard reagents, under Wenkert Nickel-catalysed conditions, gave access to several substituted (Z)-alkenyl derivatives. These Nickel-catalysed reactions, carried out with vinyl-, phenyl-, p-methoxyphenyl-, trimethylsilylmethylmagnesium bromide and benzylmagnesium chloride, led to the corresponding (Z)-alkenyl derivatives in good yields and high stereoselectivities.     

Deposition of long-lived radionuclides after the chernobyl accident in the forestal massif of boreon

After the reactor accident at Chernobyl, samples of soil, moss, lichen and fern were collected in the forest around the Vesubie valley in the South East of France and analyzed by low energy photon and gamma spectrometry. Activity concentrations as high as 42.8, 9.4 and 3.8 kBq.m^–2 were measured for¹³⁷Cs,¹³⁴Cs and¹⁰⁶Ru, respectively, in soil, in October 1988.¹²⁵Sb and^110mAg were also detected. The contamination was found to be the most important between 1400 and 1700 m altitude.     

Simultaneous non-destructive determination of long-lived radionuclides in contaminated seaweed by X-ray spectrometry

Summary Planar high purity germanium detectors have been used for activity determination of fission nuclides, as well as transuranic elements, in a contaminated seaweed. The activity of a given isotope was deduced from the absolute detection efficiency of the detector and from the branching ratioR=N _k /N of the K-X photons emitted by desintegration; in case of monoenergeticy emitters, these branching ratios have been calculated from nuclear data decay. These low-energy measurements require one standard sample only for simultaneous determination of several isotopes. The data obtained in this work for the¹³⁷Cs specific activity by non-destructive analysis are in good agreement with the results of an intercomparison exercise performed by the IAEA. Moreover, this method allows us to measure in this seaweed the specific activity of the previously not detected¹²⁹I nuclide, both by destructive and nondestructive analysis, and that of²⁴¹Pu which generally needs complicated radiochemical separations.

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Gleichzeitige nicht-destruktive Bestimmung langlebiger Radionuklide in verunreinigtem Seetang durch Röntgenspektrometrie

Zusammenfassung Planäre hochreine Germanium-Detektoren wurden zur Aktivitätsbestimmung von Spaltnukliden und von Transuranen in Seetang verwendet. Die Aktivität eines bestimmten Isotops wurde abgeleitet aus der absoluten Nachweisanzeige des Detektors und aus dem VerhältnisR=N _k /N der durch Desintegration freigesetzten K-X-Photonen; bei monoenergetischen Gammastrahlen wurde dieses Verhältnis aus der Abnahme der nuklearen Daten berechnet. Diese Messungen geringer Energien erfordern nur eine Standardprobe für die gleichzeitige Bestimmung verschiedener Isotoper. Die von uns durch nichtdestruktive Analyse ermittelten Werte für die spezifische Aktivität von¹³⁷Cs stimmen mit den Ergebnissen einer vergleichenden Untersuchung der IAEA gut überein. Außerdem konnten wir mit diesem Verfahren in diesem Seetang die spezifische Aktivität des bisher nicht festgestellten Nuklids¹²⁹J sowohl durch destruktive wie durch nicht-destruktive Analyse messen und ebenso die von²⁴¹Pu, wozu im allgemeinen komplizierte radiochemische Trennverfahren nötig sind.

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Presented in part at the 9th International Microchemical Symposium, Amsterdam, August 28–September 2, 1983.     

Use of uranium isotopes for the determination of river tributary flow rates: Case of the Var and the Vésubie

When a river flow rate is known on one point, it is possible to determine the one of upstream tributaries. This can be done by measuring the concentrations of a dissolved element (for example Ca²⁺), provided that no chemical precipitations have occurred in mixture waters. In this later case, the determination of flow rate is however possible by isotopic geochemistry, by knowing isotopic ratios of an element, for ex. ²³⁴U/²³⁸U, in each river considered and the ratio of the concentrations in dissolved ²³⁸U in two of them. A study of the Var and its tributary the Vésubie is performed: in January 31st, 2001, the flow rate D₃, downstream the confluence was 35 m³/s. The ratio of the ²³⁸U concentrations in the Vésubie river and in the Var upstream (²³⁸U₁/²³⁸U₂) was 5.5. The isotopic ratios ²³⁴U/²³⁸U measured in the Var, downstream the confluence were R₃ = 1.51, upstream R₂ = 1.75, and in the Vésubie R₁ = 1.08. We have calculated the Vésubie flow rate as D₁ = 3.2 m³/s.     

Alkoxyallene‐ynes: Selective Preparation of Bicyclo[5.3.0] Ring Systems Including a δ‐Alkoxy Cyclopentadienone

The development of an intramolecular rhodium(I)‐catalyzed Pauson–Khand reaction of alkoxyallene‐ynes with a proximal alkoxy group is reported. This reaction, in the presence of a [Rh(cycloocta‐1,5‐diene)Cl]₂/propane‐1,3‐diylbis(diphenylphosphane) system under a CO atmosphere, constitutes a powerful tool for selectively accessing carbo‐ and heterobicyclo[5.3.0] frameworks featuring an enol ether moiety. Through this procedure, a straightforward access to guaiane skeletons with a tertiary hydroxy group at the C10 position was achieved.     

On the γ-spectrum following225Ac α-decay

The decay of a²²⁵Ac source in equilibrium mixture with its decay products was investigated using high-resolution HP/Ge/ detectors. Energies and intensities of more than 78 -photons were measured with an improved accuracy; 44 of them are reported for the first time. A tentative²²¹Fr level scheme was built on the basis of good energy sum relationships; seven new²²¹Fr excited levels are proposed at 496.9, 570.9, 603.5, 630.7, 637.7, 649.0 and 758.9 keV.     

Tin(IV) complexes with 2-pyridineformamide-derived thiosemicarbazones: Antimicrobial and potential antineoplasic activities

Reaction of tin tetrachloride with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives gave [Sn(2Am4DH)Cl₃] (1), [Sn(2Am4Me)Cl₃] (2), [Sn(2Am4Et)Cl₃] (3) and [Sn(2Am4Ph)Cl₃] (4) as products, in which an anionic thiosemicarbazone coordinates to the metal centre along with three chloride ions. The crystal structures of 1 and 2 were determined. The thiosemicarbazones were moderately active against Candida albicans and Pseudomonas aeruginosa. Upon coordination to tin(IV) the antimicrobial activity of the thiosemicarbazones increases. The studied compounds proved to be toxic to Artemia salina, suggesting that they could present cytotoxic activity against solid tumors.