A Convenient Synthesis of N-Arylanthranilic Acids Using Ultrasonics in the Ullmann-Goldberg Condensation

Ultrasonics efficiently promotes the Ullmann-Goldberg condensation of 2-halogenobenzoic acids and primary aromatic amines to obtain various N-arylanthranilic acids.     

Mass Spectrometry Study of Coumarins: Correlation Between Charges of Atoms and Fragmentation Processes

The mass spectrometry of a number of 6-substituted coumarins was studied in the context of correlating fragmentation pathways and electronic charges of atoms performed by AM₁ semiempirical method. The atomic charges of atoms are found to be good predictors of the fragmentation pathways.     

Rational interpolation to solutions of Riccati difference equations on elliptic lattices

It is shown how to define difference equations on particular lattices {x_n}, n∈Z, where the x_ns are values of an elliptic function at a sequence of arguments in arithmetic progression (elliptic lattice). Solutions to special difference equations (elliptic Riccati equations) have remarkable simple (!) interpolatory continued fraction expansions.     

Palladium-mediated phosphine-dependent chemoselective bisallylic alkylation leading to spirocarbocycles

Cycles everywhere: The selectivity in the transformations of 1,3-diones to carbocycles by palladium-catalyzed bisallylic alkylations is strongly dependent on the phosphine that is employed. Moreover, synthesized vinylcyclopentenes can be easily transformed into cycloheptadiene derivatives through a carbon?carbon allylic bond cleavage.     

Freud equations for Legendre polynomials on a circular arc and solution of the Grünbaum–Delsarte–Janssen–Vries problem

One establishes inequalities for the coefficients of orthogonal polynomials

which are orthogonal with respect to a constant weight on the arc of the unit circle S={e^iθ,απ<θ<2π-απ}, with 0<α<1. Recurrence relations (Freud equations), and differential relations are used. Among other results, it is shown that Φ_n(0)>0,n=1,2,…     

3-manifolds whose universal coverings are Lie groups

We classify those closed 3-manifolds whose universal covering space naturally admits the structure of a Lie group     

On representing block designs in terms of their automorphisms

Block designs are analyzed in terms of the structure imposed upon them by their automorphisms. An extension of the notion of a difference set is used to describe necessary and sufficient conditions for the existence of a given automorphism acting on the design. In addition, it is shown that the possible point and block orbit configurations relative to an automorphism acting on a design are rather limited. The development is carried out with a view toward finding unknown designs and studying the automorphism groups of known designs.     

A bis(η-cyclopentadienyl)cobalt complex of a bis-dithiolene: a chemical analogue of the metal centres of the DMSO reductase family of molybdenum and tungsten enzymes, in particular ferredoxin aldehyde oxidoreductase

The synthesis is described of a bis-ene-1,2-dithiolate pro-ligand, designed to model the stereochemical situation in the cofactor of the tungsten enzyme ferredoxin aldehyde oxidoreductase from Pyrococcus furiosus. Each masked ene-1,2-dithiolate unit is mounted on a pyrano[2,3-b]tetrahydroquinoxaline tricycle, comparable to the pyrano[2,3-g]tetrahydropteridines found in all molybdoenzymes and tungsten analogues. Hydrolytic release of the bis-ligand was confirmed by its entrapment as a double (η⁵-C₅H₅)Co complex.     

Etude du mecanisme de la cyclotrimerisation catalytique de l'hexyne-3 par l'intermediaire d'un complexe cyclobutadienique du nickel

The reduction of nickel halide by metals in low oxidation states, in a boiling solution of 3-hexyne in tetrahydrofuran leads to catalytic and quantitative cyclotrimerisation of the unsaturated compound. During the reaction, tetraethylcyclobutadienenickel(II) dibromide can be isolated in appreciable yield. A mechanism is proposed for the cyclotrimerisation.