Pyridinylidenaminophosphines: Facile Access to Highly Electron-Rich Phosphines

Electron-rich tertiary phosphines are valuable species in chemical synthesis. However, their broad application as ligands in catalysis and reagents in stoichiometric reactions is often limited by their costly synthesis. Herein, we report the synthesis and properties of a series of phosphines with 1-alkylpyridin-4-ylidenamino and 1-alkylpyridin-2-ylidenamino substituents that are accessible in a very short and scalable route starting from commercially available aminopyridines and chlorophosphines. The determination of the Tolman electronic parameter (TEP) value reveals that the electron donor ability can be tuned by the substituent pattern at the aminopyridine backbone and it can exceed that of common alkylphosphines and N-heterocyclic carbenes. The potential of the new phosphines as strong nucleophiles in phosphine-mediated transformations is demonstrated by the formation of Lewis base adducts with CO₂ and CS₂. In addition, the coordination chemistry of the new phosphines towards Cu^I, Au^I, and Pd^II metal centers has been explored, and a convenient procedure to introduce the most basic phosphine into metal complexes starting from air-stable phosphonium salt is described.     

A Fluorescence-Based Assay System for the Determination of Haloperoxidase-Activity Using a Two-Dimensional Calibration Ap-proach

Screening for an interesting biocatalyst and its subsequent kinetic characterization depends on a reliable activity assay. In this work, a fluorometric assay based on the halogenation of 4-methyl-7-diethylamino-coumarin was established to monitor haloperoxidase-activity. Since haloperoxidases utilize hydrogen peroxide and halide ions to halogenate a broad range of substrates by releasing hypohalous acids, a direct quantification of haloperoxidase-activity remains difficult. With the system presented here, 3-bromo-4-methyl-7-diethylaminocoumarin is preferentially formed and monitored by fluorescence measurements. As starting material and product share similar spectroscopical properties, a two-dimensional calibration ap-proach was utilized to allow for quantification of each compound within a single measurement. To validate the system, the two-dimensional Michaelis-Menten kinetics of a vanadium-dependent chloroperoxidase from Curvularia inaequalis were recorded, yielding the first overall kinetic parameters for this enzyme. With limits of detection and quantification in the low μm range, this assay may provide a reliable alternative system for the quantification of haloperoxidase-activity.     

Influence of benzo-bridging on the stability of 6aλ4-thia-1,2,5,6-tetraazapentalenic systems

Methylation of the phenylhydrazone derived from 8-oxo-8H-indeno[1,2-d]-1,2,3-thiadiazole 5 with Meerwein's reagent furnishes the two methylated products 7 and 8. Single crystal X-ray analyses of these compounds reveal no significant S…NPh interaction, thus excluding a thiapentalene structure.     

Influence of the number of flights on the dilute phase ratio in flighted rotating drums by PTV measurements and DEM simulations

Particle distribution in the cross-section of the flighted rotating drum(FRD)is critical to the analysis of heat and mass transfer between gas and solids.In thi...     

Slope analysis to obtain starting parameters for curve fitting calculations in the special case of the Johnson-Mehl-Avrami model function

The attempt was undertaken to describe analytically isothermal resistivity measurement curves of Al Zn and Al Zn Mg alloys by means of the Johnson-Mehl-Avrami equation. The paper gives a survey of results obtained based on the application of the Extented Slope Analysis. Comparison was performed to results of fitting calculations (Linear Regression). It can be shown that the intersection behaviour after the Extented Slope Analysis leads to reasonable results if rough evaluation is required in a first stage of an investigation. Furthermore this method leads to reliable starting parameters and starting length of the fitting intervals. Additionally the second process with Al Zn Mg alloys can be estimated by use of the Extented Slope Analysis.     

High-spin structure in154Er

High spin states in the nucleus¹⁵⁴Er have been reinvestigated using the¹²³Sb(³⁵Cl, 4n) reaction and a variety of spectroscopic techniques including excitation functions,γ-γ coincidences,γ angular distribution and linear polarization measurements. From the measured energies, relative intensities and transition multipolarities a new level scheme has been deduced up to an excitation energy of ～12 MeV and spin 36. An interpretation of the experimental results is given in terms of the deformed Woods-Saxon orbitals. Gigantic backbending (superdeformation) effect is studied theoretically within the cranking model.     

On the Functional Characterization of the Analytic Wave Front Set of an Hyperfunction

We give a characterization of d-dimensional modulation spaces with moderate weights by means of the d-dimensional Wilson basis. As an application we prove that pseudodifferential operators with generalized Weyl symbols are bounded on these modulation spaces.     

A Biocatalytic Cascade for Versatile One‐Pot Modification of mRNA Starting from Methionine Analogues

Methyltransferases have proven useful to install functional groups site‐specifically in different classes of biomolecules when analogues of their cosubstrate S‐adenosyl‐l ‐methionine (AdoMet) are available. Methyltransferases have been used to address different classes of RNA molecules selectively and site‐specifically, which is indispensable for biophysical and mechanistic studies as well as labeling in the complex cellular environment. However, the AdoMet analogues are not cell‐permeable, thus preventing implementation of this strategy in cells. We present a two‐step enzymatic cascade for site‐specific mRNA modification starting from stable methionine analogues. Our approach combines the enzymatic synthesis of AdoMet with modification of the 5′ cap by a specific RNA methyltransferase in one pot. We demonstrate that a substrate panel including alkene, alkyne, and azido functionalities can be used and further derivatized in different types of click reactions.