Study of the Acylation Reaction of 2(3H)-Benzothiazolones in the Mixture of ZnCl 2 -DMF

The use of polyphosphoric acid and the complex AlCl 3 -DMF in 6-acylation of 2(3H)-benzothiazolones previously have been reported. Instead of the frequently used AlCl 3 as a catalyst in the Friedl-Crafts reactions, we conducted the acylation of 2(3H)-benzothiazones using zinc chloride as a catalyst in DMF as solvent and acid chlorides or anhydrides as acylating agents.     

Synthesis and complexation properties towards metal ions of new tri-substituted thiacalix[4]arenes

New thiacalix[4]arenes appended with three amide functions have been prepared. Their conformations have been solved thanks to ¹H NMR 2D correlation spectroscopy (COSY) and nuclear overhauser and exchange spectroscopy (NOESY). The complexation ability of these ligands towards various metal ions (Cd^2 + , Pb^2 + , Pd^2 + , Ni^2 + , Hg^2 + , Hg⁺, Ag⁺, Zn^2 +  and Cu^2 + ) has been investigated by the UV–vis absorption and the stoichiometry of the metal–ligand complexes was determined.     

Application of the "Fries Like" Rearrangement Using ZnCl 2 for the Synthesis of 6-Acyl-2(3H)-benzothiazolones

In this work we report another method of acylation on the 6-position of the 2(3H)-benzothiazolone ring with Fries-like rearrangement catalyzed by zinc chloride instead of aluminium chloride and 3-acyl-2(3H)-benzothiazolones derivatives as starting materials. This method is advantagous in regard to other acylation methods as it requires only three equivalents of ZnCl 2 to produce 6-acyl-derivatives with yields of 82-94%.     

An inverse source problem with multiple frequency data

The Note is concerned with an inverse source problem for the Helmholtz equation, which determines the source from measurements of the radiated field away at multiple frequencies. Our main result is a novel stability estimate for the inverse source problem. Our result indicates that the ill-posedness of the inverse problem decreases as the frequency increases. Computationally, a continuation method is introduced to solve the inverse problem by capturing both the macro and the small scales of the source function. A numerical example is presented to demonstrate the efficiency of the method.     

Synthesis and X‐Ray Analysis of a New [6]Helicene

A new disubstituted hexahelicene derivative 3 bearing methoxy functions at positions 3 and 14 has been prepared in racemic form through a Heck reaction followed by photocyclodehydrogenation. Suitable crystals of rac‐3 were analyzed by X‐ray crystallography and showed similar geometry to the structure of hexahelicene itself. Deprotection of 3 using boron tribromide led to 3,14‐dihydroxyhexahelicene 4 in quantitative yield. The complexation of transition metal atoms seemed to be quite possible by these two bidentate hexahelicene derivatives.     

The Plasmonic Resonances of a Bowtie Antenna

Metallic bowtie-shaped nanostructures are very interesting objects in optics,due to their capability of localizing and enhancing electromagnetic fields in the vicinity of their central neck.In this article,we investigate the electrostatic plasmonic resonances of two-dimensional bowtie-shaped domains by looking at the spectrum of their Poincare variational operator.In particular,we show that the latter only consists of essential spectrum and fills the whole interval[0,1].This behavior is very different from what occurs in the counterpart situation of a bowtie domain with only close-totouching wings,a case where the essential spectrum of the Poincare variational operator is reduced to an interval oess strictly containing in[0,1].We provide an explanation for this difference by showing that the spectrum of the Poincare variational operator of bowtie-shaped domains with close-to-touching wings has eigenvalues which densify and eventually fill the remaining parts of[0,1]\σess as the distance between the two wings tends to zero.     

Effects of a low frequency parametric excitation

The effects of a slowly varying parametric excitation on a shallow arch model are investigated. The delay bifurcation and the sequence of visited equilibria are analyzed. The method of Melnikov and a method proposed by Berglund [Adiabatic dynamical systems and hysteresis, Ph.D. thesis, Institut de Physique Théorique EPRFL, Lausanne, Switzerland, 1998] are used to determine chaotic regions.     

A new one-dimensional hybrid material lattice: AC conductivity and structural characterization of [C<Subscript>7</Subscript>H<Subscript>12</Subscript>N<Subscript>2</Subscript>][CdCl<Subscript>4</Subscript>]

The present paper reports the synthesis, crystal structure, ¹³C and ¹¹¹Cd cross-polarization magic-angle spinning nuclear magnetic resonance(CP-MAS-NMR) analysis and ac conductivity for a new organic–inorganic hybrid salt, [C₇H₁₂N₂][CdCl₄]. The compound crystallizes in the triclinic system, space group P\( \overline 1 \), with unit cell dimensions: a?=?7.1050(3) Å, b?=?8.9579(3) Å, c?=?9.4482(3) Å, α?=?81.415(1)°, β?=?89.710(2)°, γ?=?85.765(1)°, V?=?592.97(4) Å³, and Z?=?2. The asymmetric unit is composed of one-2,4-diammonium toluene cation and one [CdCl₄]^2? anion. The Cd atom is in a slightly distorted octahedra coordination environment. Its structure can be described by infinite chains of CdCl₆ octahedron linked to organic cations by a strong charge-assisted N–H???Cl interactions in order to build organic–inorganic layers staked along \( \left[ {0\overline 1 1} \right] \) direction. The solid state ¹³C CP-MAS-NMR spectra has shown seven isotropic resonances, confirming the existence of seven non-equivalent carbon atoms, which is consistent with crystal structure determined by X-ray diffraction. As for ¹¹¹Cd MAS-NMR, it has shown one cadmium site with isotropic chemical shift observed at 167.2 ppm. The complex impedance of the compound has been investigated in the temperature range of 403–460 K and in the frequency range of 200 Hz–5 MHz. The impedance plots have shown semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance R _p and constant phase elements.     

Chemoselective preparation of disymmetric bistriazoles from bisalkynes

Best of both worlds, molecules bearing two alkyne groups, activated and unactivated, can selectively react on the activated one in a copper-free version of Huisgen’s reaction to form a first triazole ring, with a good selectivity toward the 1,4-isomer, which is solely isolated by a simple trituration procedure. The other alkyne function is then submitted to the selective reaction using a polymer-supported copper(I) catalyst to form a second triazole ring. This gave access to disymmetric bistriazoles without the need of protection using simple, easy, and fast procedures.