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Synthesis, Reactivity, and Properties of Benz[a]azulenes via [8 + 2] Cycloaddition of 2H-cyclohepta[b]furan-2-ones with an Enamine
No full textStarting with the reaction of 2H-cyclohepta[b]furan-2-ones with an enamine, which was prepared from 4-tert-butylcyclohexanone and pyrrolidine, benz[a]azulenes having both formyl and tert-butyl groups were obtained in the three-step sequence. Subsequently, both the formyl and tert-butyl groups were eliminated by heating the benz[a]azulene derivatives in 100% H3PO4 to give benz[a]azulenes without these substituents in high yields. In terms of the product yield, this method is the best one ever reported for the synthesis of the parent benz[a]azulene so far. The conversion of the benz[a]azulene derivatives with a formyl group into cyclohept[a]acenaphthylen-3-one derivatives was also investigated via Knoevenagel condensation with dimethyl malonate, followed by Brønsted acid-mediated intramolecular cyclization. The structural features including the bond alternation in the benz[a]azulene derivatives were revealed by NMR studies, NICS calculations, and a single-crystal X-ray structural analysis. The optical and electrochemical properties of a series of benz[a]azulene derivatives were evaluated by UV/Vis, fluorescence spectroscopy and voltammetry experiments. As a result, we found that some benz[a]azulene derivatives showed remarkable luminescence in acidic media. In addition, the benz[a]azulene derivatives with the electron-withdrawing group and cyclohept[a]acenaphthylen-3-one derivative displayed good reversibility in the spectral changes under the electrochemical redox conditions
Benz[a]azulenequinones: Reaction of Benz[a]azulenes with Pyridinium Hydrobromide Perbromide
No full textA series of benz[a]azulenes reacted with pyridinium hydrobromide perbromide (PHBPB) in hydrous tetrahydrofuran yielding the corresponding benz[a]azulenequinones in moderate yields. The detailed structure of the benz[a]azulenequinone derivative obtained was clarified by single crystal X-ray analysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Milieurisicogrenzen voor benz[a]antraceen
No full textHet RIVM heeft in opdracht van het ministerie van Infrastructuur en Milieu (I&M), milieurisicogrenzen voor benz[a]antraceen bepaald. Dit was nodig omdat de huidige norm voor benz[a]antraceen voor waterkwaliteit niet is afgeleid volgens de meest recente methodiek. Benz[a]antraceen is een stof die behoort tot de stofgroep PAK's. De stof is opgenomen in de Regeling Monitoring Kader Richtlijn Water, waarin staat aan welke eisen oppervlaktewater in Nederland moet voldoen. De Stuurgroep Stoffen stelt deze nieuwe normen vast op basis van de wetenschappelijke advieswaarden in dit rapport. Het Maximaal Toelaatbaar Risiconiveau (MTR) is de concentratie in water waarbij geen schadelijke effecten te verwachten zijn, gebaseerd op jaargemiddelde concentraties. Hiervoor zijn drie routes onderzocht: directe effecten op waterorganismen, indirecte effecten op vogels en zoogdieren via het eten van prooidieren en indirecte effecten op mensen via het eten van visserijproducten. De laatste van de drie levert de laagste waarde en bepaalt daarmee het MTR voor zoet- en zoutwater (0,23 nanogram per liter). De Maximaal Aanvaardbare Concentratie (MACwater, eco), die het ecosysteem beschermt tegen kortdurende concentratiepieken, is 0,1 microgram per liter voor zoetwater en 0,01 microgram per liter voor zoutwater. De nieuw afgeleide milieurisicogrenzen voor water en in water zwevend stof zijn lager dan de nu geldende milieurisicogrenzen. Dit kan direct worden verklaard doordat consumptie van waterdieren door vogels and zoogdieren en menselijke visconsumptie in de nieuwe norm zijn meegewogen. Gebaseerd op monitoringsgegevens worden de nieuwe MTR en MACeco voor water, zwevend stof en sediment naar verwachting overschreden. Bij deze beoordeling is mengseltoxiciteit voor het totaal aantal PAK's nog niet in beschouwing genomen.RIVM has derived environmental risk limits (ERLs) for benz[a]anthracene. This derivation has been performed because the current ERLs have not been derived according to the current valid methodology. Benz[a]anthracene is a substance belonging to the group of PAHs and is included in the Dutch decree on water quality objectives in the context of the Water Framework Directive (WFD). The ERLs in this report are advisory values that serve as a scientific background for the Dutch Steering Committee for Substances, which is responsible for setting those standards. The maximum permissible concentration in water (MPCwater) is the level at which no harmful effects are expected, based on annual concentrations. This MPC is based on three routes: direct toxicity, secondary poisoning and consumption of fish by humans. The latter of the three routes is the most critical of these three routes and determines the overall MPC for fresh- and saltwater (0.23 nanogram per liter). The Maximum Acceptable Concentration (MACwater, eco), that protects the ecosystem from effects of short term concentration peaks, is 0.1 microgram per liter for freshwater and 0.01 microgram per liter for saltwater. The newly derived ERLs for water and suspended matter are lower than the currently valid ERLs. This can be explained by the fact that the risk through exposure of humans by consumption of fish and exposure of birds and mammals by consumption of water animals have been considered for these new ERLs. Monitoring data indicate that the new MPC and MACeco for water, suspended matter and sediment are being exceeded. In this observation, mixture toxicity for the total of PAHs has not been included.Directoraat-Generaal Milieubehee
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