Overview of the synthetic routes of 2-alkyl-4-hydroxy-2H-1,2-benzothiazine-3-carboxamides-1,1-dioxides (oxicams) and their analogues

The biological and medicinal properties of oxicams and its analogues have prompted enormous research aimed at developing synthetic routes to these heterocycles. This review focuses on the chemical properties associated with this system.     

Reaction between benzoyl isothiocyanate and 2,6-dimethylphenyl isocyanide: synthesis of a sterically congested ten-membered ring containing the S–S–S moiety

Abstract  

2,6-Dimethylphenyl isocyanide reacts with benzoyl isothiocyanate in a clean one-pot reaction to afford a sterically congested ten-membered ring containing the S–S–S moiety in nearly quantitative yield. Dynamic effects are observed in the ¹H nuclear magnetic resonance (NMR) spectrum of this compound for the restricted rotation around two of the Ar–N single bonds.     

Electrical conductivity studies on some dibenzoylmethane arylhydrazones (DBMAH)

Electrical conductivity of some dibenzoylmethane arylhydrazones (DBMAH) were measured during heating and reheating runs. The observed variation of the conductance of the polycrystalline sample during thermal agitation was found to depend on the ordering and disordering of molecules which in turn cause the lattice dipole to distort. A semiconducting behavior was detected for these systems as it was deduced from their conductance values (1.7 × 10⁻⁶ − 8.25 × 10⁻⁷ ohm⁻¹ cm⁻¹). The presence of substituents affects markedly the measured electrical conductivity and calculated activation energy values.     

Self-assembly of CuSO4 nanoparticles and bending multi-wall carbon nanotubes on few-layer graphene surfaces

When a colloidal suspension is allowed to wet a suitable substrate, various patterns emerge that can be varied from isolated island-like structures to fractal patterns. In this work we investigate the patterns arising from the interplay of colloidal copper sulfate suspensions containing carbon nanotubes with few-layer graphene substrates. The compositions of the thin film samples were investigated using X-ray photoelectron spectroscopy, surface topography and the nanostructure of the thin films were probed with atomic force microscope and transmission electron microscope respectively. The colloidal suspensions were characterized using contact angle and viscosity measurements. The colloidal suspensions when dip coated on few-layer graphene substrates exhibited fractal like morphology with the aggregation of copper sulfate crystallites to hexagonal platelets. This aggregation is explained invoking the depletion attraction theory. The various patterns observed experimentally were reproduced using a Monte Carlo simulation.     

PV Cohomology of the Pinwheel Tilings, their Integer Group of Coinvariants and Gap-Labeling

In this paper, we first remind how we can see the “hull” of the pinwheel tiling as an inverse limit of simplicial complexes (Anderson and Putnam in Ergod Th Dynam Sys 18:509–537, 1998) and we then adapt the PV cohomology introduced in Savinien and Bellissard (Ergod Th Dynam Sys 29:997–1031, 2009) to define it for pinwheel tilings. We then prove that this cohomology is isomorphic to the integer Čech cohomology of the quotient of the hull by S ¹ which let us prove that the top integer Čech cohomology of the hull is in fact the integer group of coinvariants of the canonical transversal Ξ of the hull. The gap-labeling for pinwheel tilings is then proved and we end this article by an explicit computation of this gap-labeling, showing that m^t ( C(X,\mathbb Z) ) = \frac1264\mathbb Z [ \frac15]{\mu^t \left( C(\Xi,\mathbb {Z}) \right) = \frac{1}{264}\mathbb {Z} \left [ \frac{1}{5}\right ]}.     

Electrometric, spectroscopic and thermogravimetric studies on lanthanide-arylhydrazones of benzoylacetone and dibenzoylmethane complexes

The chelate formation reaction of La^III, Pr^III, Nd^III, Gd^III, Ho^III and Er^III ions with some arylhydrazones of benzoylacetone (BAAH) and dibenzoylmethane (DBMAH) has been investigated by conductimetric and pH-metric titration. The chelates formed have 1:1 and 1:2 stoichiometries (M³⁺: L). The stability constants of the metal chelates are correlated to the atomic numbers Z, the ionic radii r, the ionization potentials and the electronegativities of the lanthanide ions.

The solid complexes have been isolated and their structures have been assigned on the basis of elemental analysis, IR and NMR spectroscopy and thermogravimetric analysis (TG). It has been determined that the chelation occurs through the -NH group and one carbonyl group of the β-diketone, in addition to the OH⁻ group. The coordination number ranges from six to eight according to the number of coordinated water molecules which are confirmed by thermogravimetric analysis. The structural formulae are suggested.     

One‐Pot Synthesis of Pentaalkyl 7‐[(Alkylamino)carbonyl]‐2‐oxa‐1‐azabicyclo[3.2.0]hept‐3‐ene‐3,4,5,6,7‐pentacarboxylate

Dialkyl acetylenedicarboxylates react with alkyl 2‐nitroethanoates in the presence of alkyl isocyanides in a one‐pot reaction to afford the title compounds in 78–90% yield.     

On the Reaction between Alkyl Isocyanides and Ethynyl Phenyl Ketone in the Presence of N,N′-Dimethylbarbituric Acid

Summary.  The reactive 1:1 intermediate produced in the reaction between alkyl isocyanides and ethynyl phenyl ketone was trapped with N,N ′-dimethylbarbituric acid to produce alkyl 1,3-dimethyl-2,4-dioxo-7-phenyl-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-5-carboxamides in good yields. Corresponding author. E-mail: isayavar@yahoo.com Received January 8, 2002. Accepted January 14, 2002