Search results for "Step"
showing 10 items of 509 documents
Two-Step Route to Indoles and Analogues from Haloarenes: A Variation on the Fischer Indole Synthesis
2012
In a new variation on the Fischer indole synthesis, readily available haloarenes are converted into a wide range of indoles in just two steps by halogen-magnesium exchange and quenching with di-tert-butyl azodicarboxylate, followed by reaction with aldehydes or ketones under acidic conditions. The protocol, which is readily extended to the preparation of indole isosteres, 4- and 6-azaindoles and thienopyrroles, obviates the need to prepare potentially toxic aryl hydrazines, simultaneously avoiding undesirable anilines such as naphthylamines.
Cautionary Note on the Two-Step Transformation to Normality
2019
ABSTRACT Templeton and Burney (2017) proposed a two-step normality transformation as a remedy for non-normally distributed data, which are commonly found in AIS research. We argue that, rather than transforming the data toward normality, researchers should first seek to analyze and understand the sources of non-normality. Using simulated datasets, we demonstrate three sources of non-normality and their consequences for regression estimation. We then demonstrate that the two-step transformation cannot solve any of these problems and that each source of non-normality can be handled with alternative, existing techniques. We further present two empirical examples to demonstrate these issues wit…
Synthesis and structure of the incomplete cuboidal clusters [W3Se4H3(dmpe)3]+, [W3Se4H3−x(OH)x(dmpe)3]+and [W3Se4(OH)3(dmpe)3]+, and the mechanism of…
2004
The novel incomplete cuboidal cluster [W3Se4H3(dmpe)3](PF6), [1](PF6), has been prepared by reduction of [W3Se4Br3(dmpe)3](PF6) with LiBH4 in THF solution. The trihydroxo complex [W3Se4(OH)3(dmpe)3](PF6), [2](PF6), was obtained by reacting [W3Se4Br3(dmpe)3](PF6) with NaOH in MeCN–H2O solution. The complexes [1](PF6) and [2](PF6) were converted to their BPh4− salts by treatment with NaBPh4. Recrystallisation of [1](BPh4) in the presence of traces of water affords the mixed dihydride hydroxo complex [W3Se4H2(OH)(dmpe)3](BPh4). The crystal structures of [1](BPh4), [2](BPh4) and [W3Se4H2(OH)(dmpe)3](BPh4) have been resolved. Although the [1]+ trihydride does not react with an excess of halide s…
Der 2‐(Methylthio)äthoxycarbonyl‐Rest als Zweistufen‐Schutzgruppe für die Aminofunktion in Aminosäuren und Peptiden
1976
Die 2-(Methylthio)athoxycarbonyl(Mtc)-Gruppe wird als neue Amino-Schutzgruppe fur Aminosauren und Peptide beschrieben. Zu ihrer Einfuhrung eignen sich sowohl das Mtc-p-Nitrophenolat als auch das Mtc-Phenolat. Die Mtc-Schutzgruppe ist in Masig alkalischem oder saurem Medium bestandig. Durch zwei unterschiedliche und einfache Reaktionen kann die unempfindliche Mtc-Gruppe in gegenuber Basen sehr empfindliche Schutzgruppen umgewandelt werden und wird deshalb als Zweistufen-Schutzgruppe bezeichnet. Die Methylierung zur 2-(Dimethylsulfonio)-athoxycarbonyl-Schutzgruppe verlauft nicht immer befriedigend, erbringt jedoch oft N-geschutzte Verbindungen, die sehr gut in Wasser loslich sind. Nahezu quan…
Reactive adsorption of thiophene on Ni/ZnO: role of hydrogen pretreatment and nature of the rate determining step.
2008
Abstract Reactive adsorption of thiophene on reduced and unreduced NiO/ZnO adsorbents was studied by thermal gravimetric analysis and by sulfidation in a fixed bed reactor at 330–375 °C and 10–40 mbar of thiophene in hydrogen. The adsorbents (12 wt% Ni) were prepared by co-precipitation of corresponding nitrates with sodium carbonate followed by calcination at 400 °C. We have found that such solids can react with thiophene without any prior reduction. Metallic Ni, indispensable for thiophene decomposition, is formed in this case in situ upon the contact with thiophene/H 2 reaction mixture. The reduction of NiO/ZnO in H 2 (360 °C, 6 h) results in the formation of Ni–Zn alloyed particles (as …
A backward sweep method for power flow solution in distribution networks
2010
Abstract A methodology for the analysis of radial or weakly meshed distribution systems supplying voltage dependent loads is here developed. The solution process is iterative and, at each step, loads are simulated by means of impedances. Therefore, at each iteration, it is necessary to solve a network made up only of impedances; for this kind of network, all the voltages and currents can be expressed as linear functions of a single unknown current (in radial systems) or of two unknown currents for each independent mesh (for meshed systems). The methodology has been called “backward” since the unique equation, in case of radial network, and the linear system of equations, in case of meshed n…
Viisas opettaja elää hetkessä - ja ikuisuudessa
2017
Huumeet ja kirjailijoiden luovuus
2017
Pro gradu -tutkielmani käsittelee huumeiden ja kirjailijoiden luovuuden välistä yhteyttä. Kirjailijat ja alkoholi yhdistetään helposti toisiinsa, ja erityisesti siten, että alkoholi on ollut muusa. Alkoholiin mieltyneiden kirjailijoiden lisäksi historia tuntee myös huumeita käyttäneitä kirjailijoita. Miten huumeet vaikuttivat heidän luovuuteensa? Oliko eri huumeilla erilaisia vaikutuksia? Vai oliko huumeista pikemminkin haittaa luovalle työlle? Tarkastelen neljän hyvin erilaisen kirjailijan päihteidenkäyttöhistoriaa ja tuotantoa. Kirjailijat ovat William S. Burroughs, Jack Kerouac, Hunter S. Thompson ja Stephen King. Heistä vain viimeksi mainittu on vielä elossa. Otan myös huomioon kirjaili…
The Konstostephanos Family - Worst or the best mega douxes of Komnenian Navy in the 12th century?
2018
Vegetation and climate in the eastern Iberian Peninsula during the pre-evaporitic Messinian (late Miocene). Palynological data from the Upper Turolia…
2015
International audience; The present paper reports a complete palynological study of the Upper Turolian sediments outcropping at the Venta del Moro site (eastern Iberian Peninsula). The pollen assemblages observed mainly reflect the local and regional vegetation, which must have formed part of a wetland ecosystem within a general setting of open steppe, as indicated by the great abundance and diversity of herbaceous pollen. This reflects the persistence of open vegetation in the Iberian Peninsula after the Middle Miocene when it became extensive. We here report the most recent record of Disanthus for the Iberian Peninsula. This shrub played an important role in an unusual, edaphically-mediat…