3,3-Dialkyltriazencarbonsäure-Derivate durch oxydative Hydro-Acyl-Elimination von 3,3-Dialkyltriazan-1,2-dicarbonsäure-Derivaten

3,3-Dialkyltriazenecarboxylic Derivatives by Oxidative Hydro-Acyl-Elimination from 3,3-Dialkyltriazane-1,2-dicarboxylic Derivatives The preparation and some properties of esters and amides of 3,3-dialkyltriazenecarboxylic acids ( 6 ) are described. These novel triazenes 6 were obtained by treatment of diesters, diamides and ester-amides of 3,3-dialkyltriazane-1,2-dicarboxylic acids ( 3 ) with lead tetraacetate, when an elimination of the COOR- or the CONHR-group at N(2) together with the H-atom at N(1) took place. The precursor triazanes 3 were readily available from the addition of secondary amines 2 to diesters, diamides or ester-amides of diazenedicarboxylic acid ( 1 ). The spectral properties of the triazanes 6 , including the ¹⁵N-NMR signals of one example, are compared with those of the triazanes 3 . They express the structural features due to conjugation in 3,3-dialkyltriazenecarboxylic derivatives, including the resistance to rotation around the N(2), N(3)-bond.     

Analysis and calculation of the 31P and 19F NMR spectra of hexafluorocyclotriphosphazene

The higher order high-resolution (31)P and (19)F NMR spectra of hexafluorocyclotriphosphazene (F(2)PN)(3) were measured at 183 K and interpreted using subspectral analysis and iterative fitting computation. (F(2)PN)(3) forms a rigid nine-spin system [A[X](2)](3) with D(3h) symmetry. Two complete and very similar sets of six experimental spin-spin coupling constants, (1)J(P,F), (2)J(P,P), (2)J(F,F), (3)J(P,F), (4)J(F,F)(cis) and (4)J(F,F)(trans), were determined for the first time. Theoretical DFT calculations of chemical shifts and coupling constants were performed to assess their predictive value. The PP/aug-cc-pVDZ treatment rendered the best agreement with experimental data.     

One-pot synthesis of 2,4-benzodiazepin-1-ones using benzotriazole methodology

2, 4-Benzodiazepin-1-ones were prepared in moderate to good yields by reaction of bis(benzotriazolylmethyl)amines with ortho-metalated N-substituted benzamides.     

Normal,abnormal and pseudo-abnormal reaction pathways for the imine-peroxyacid reaction

Steric and mesomeric effects have a marked influence upon the formation of oxaziridine (normal pathway) or nitrone (abnormal pathway) products from the imine-peroxyacid reaction; n.m.r. studies of the thermal isomerization of oxaziridines to nitrones provide evidence of a pseudo-abnormal oxidation pathway.     

Copper hydroxydiphosphate with a one-dimensional arrangement of copper polyhedra: Cu3[P2O6OH]2

A new copper hydroxydiphosphate Cu3(P2O6OH)2 was synthesized, by soft chemistry. The crystal structure was solved ab initio from X-ray powder diffraction data in the triclinic space group P. The structure is built up from [Cu3O10]infinity zigzag chains linked by P2O6(OH) groups to form a tridimensional framework. The [Cu3O10]infinity chains consist of edge-sharing polyhedra. The structure contains two sorts of copper polyhedra: one CuO6 octahedron and two CuO5 pyramids. Magnetization measurements confirm the presence of divalent copper and suggest antiferromagnetic interactions at low temperature.     

Triaziridine. II. Erste Beispiele: 2, 3-Dialkyl-triaziridin-1-carbonsäurealkylester

Triaziridines. II. First Examples: Alkyl 2,3-Dialkyl-triaziridine-1-carboxylates The first examples of substituted triaziridines 2 are described; they carry an alkoxycarbonyl and two alkyl groups (as in 4 ). The preparation of these novel threemembered nitrogen homocycles was achieved by photolysis of 1-alkoxycarbonylazimines 3c. In this way, methyl 2, 3-(cis-1, 3-cyclopentylene)triaziridine-1-carboxylate ( 6a ), methyl trans-2, 3-diisopropyl-triaziridine- 1 -carboxylate ( 8a ) and their ethyl ester analogues 6b and 8b were obtained in 50, 18, 65 and 21 % yield, respectively. The structure of the triaziridines 6 and 8 was deduced from their spectroscopic properties which reveal several interesting features: 1) N (2) and N (3), carrying alkyl groups, are pyramidal and invert slowly; 2) the isopropyl groups of 8 are situated trans to each other on the three-membered ring, whereas the two alkyl groups of 6 are cis as forced by the C-ring system; 3) N (1) is also pyramidal, despite its «amidic» nature; it inverts with an activation energy of 62 (± 4) kJ/mol; 4) the alkoxycarbonyl, group does not conjugate with N (1) and rotates rapidly. The triaziridines 6 and 8 are thermally labile, isomerizing slowly at room temperature into the corresponding azimines 5 and 7 by cleavage of one of the bonds to N (1 ). The velocity of this ring opening reaction is almost the same for 6 and 8 , so that a dependence on the relative configuration at N (2) and N (3) is not evident. The Arrhenius activation energy for the isornerization of 6a to the corresponding azimine 5a and the enthalpy difference between 6a and 5a were both determined as 100 (± 4) kJ/mol. The photolysis of 1-alkoxycarbonyl-2, 3-diisopropyl-azimines ( 7 ) in diethyl ether was accompanied by a side reaction leading to methyl and ethyl N-(1-ethoxyethyl)carbamate ( 9a and 9b , resp.), presumably by insertion of the alkoxycarbonylnitrene, generated by photofragmentation of the azimines, into the ethereal solvent.     

Reversible pH-Controlled Catenation of a Benzobisimidazole-Based Tetranuclear Rectangle

The development of methodologies to control on demand and reversibly supramolecular transformations from self-assembled metalla-structures requires the rational design of architectures able to answer to an applied stimulus. While solvent or concentration changes, light exposure or addition of a chemical have been largely explored to provide these transformations, the case of pH sensitive materials is less described. Herein, we report the first example of a pH-triggered dissociation of a coordination-driven self-assembled interlocked molecular link. It incorporates a pH sensitive benzobisimidazole-based ligand that can be selectively protonated on its bisimidazole moieties. This generates intermolecular electrostatic repulsions that reduces drastically the stability of the interlocked structure, leading to its dissociation without any sign of protonation of the pyridine moieties involved in the coordination bonds. Importantly, the dissociation process is reversible through addition of a base.     

Die Sichtbarmachung der stehenden Ultraschallwellen in durchsichtigen festen Körpern

Zeitschrift für Physik A Hadrons and nuclei - Die stehenden Ultraschallwellen in festen Körpern werden zunächst in einem Piezo-Quarz optisch abgebildet. Der Streifenabstand im Quarz...     

The use of genetic typing methods to discriminate among strains of Vibrio cholerae, V. parahaemolyticus, and V. vulnificus

This review article summarizes the findings of recent typing studies conducted on Vibrio cholerae, V. parahaemolyticus, and V. vulnificus. The DNA-based methods used to type the Vibrio spp. include whole genome approaches, such as pulsed field gel electrophoresis (PFGE), ribotyping, and repetitive extragenic palindromic (REP)-PCR, single gene targets, and multiple gene targets (multilocus approaches). The goals of these studies include establishing the relatedness of isolates from disease epidemics, discriminating among strains with more or less potential to cause disease or epidemics, and exploring the population biology of these waterborne pathogens. PFGE was consistently among the more discriminatory of the typing methods for all three Vibrio spp., and was useful for tracing the temporal and geographic relatedness of epidemic strains of V. cholerae and V. parahaemolyticus. However, PFGE did not group V. vulnificus strains according to the genotypes that have been proposed as markers of virulence potential. Typing methods that target repetitive elements distributed throughout the genome, such as BOX-PCR and REP-PCR, and DNA sequence-based methods, such as multilocus sequence typing, were also highly discriminatory and, in some cases, superior to PFGE for phylogenetic analysis and identification of strains with high epidemic or virulence potential. As typing methods and strategies are refined and used, the epidemiology, virulence potential, and ecology of these pathogenic Vibrio spp. will become better understood.