An efficient phosphine-free palladium coupling for the synthesis of new 2-arylbenzo[b]thiophenes

Straightforward and rapid access to 2-arylbenzo[b]thiophenes has been developed. It involved a catalytic coupling of 3-activated benzo[b]thiophenes with several aryl halides in the presence of a phosphine-free palladium system. In case of fragile functional groups such as aldehydes, a quaternary ammonium was used as an additive as with the other substrates, the coupling performed better and faster in the presence of a crown ether, the best one being DCH-18-C-6, with good yields and low reaction times. This method would provide a direct access to novel structures of biological interest.     

Quadratic Padé approximants and the intruder state problem of multireference perturbation methods

Simple and quadratic Padé resummation methods are applied to high‐order series from multireference many‐body perturbation theory (MR‐MBPT) calculations using various partitioning schemes (Møller–Plesset, Epstein–Nesbet, and forced degeneracy) to determine their efficacy in resumming slowly convergent or divergent series. The calculations are performed for the ground and low‐lying excited states of (i) CH₂, (ii) BeH₂ at three geometries, and (iii) Be, for which full configuration interaction (CI) calculations are available for comparison. The 49 perturbation series that are analyzed include those with oscillatory and monotonic divergence and convergence, including divergences that arise from either frontdoor or backdoor intruder states. Both the simple and quadratic Padé approximations are found to speed the convergence of slowly convergent or divergent series. However, the quadratic Padé method generally outperforms the simple Padé resummation. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Comportement thermique de polyamides et polysulfonamides “semi-aromatiques”

Various techniques (thermal analysis, dilatometry, X-ray diffraction, nuclear magnetic resonance, mass spectrometry, electrical measurements) have been used to study the thermal behaviour of several “half-aromatic” polyamides and polysulphonamides. Three transition phenomena were revealed and related to morphological modification of polymers.     

Benzo[b]thiophene as a template for substituted quinolines and tetrahydroquinolines

An original methodology starting from 3-aroyl-2-(2′-nitro-4′-methoxyphenyl)-benzo[b]thiophene allows the synthesis of unusual fused heterocycles. Direct hydrogenation with nickel catalysts followed by desulfurisation led to 2,3-diarylquinolines or 2,3-diaryltetrahydroquinolines.     

New synthetic route to diaminonitropyrazoles as precursors of energetic materials

Treatment of nitropyrimidine derivatives with (N-substituted) hydrazines (2 equiv.) gave 1-(substituted)-3,5-diamino-4-nitropyrazole, providing a very mild conversion of pyrimidines into pyrazoles. This reaction provided a convenient route to precursors for new efficient and insensitive explosives.     

Kinetics and Mechanism of Mineral Respiration: How Iron Hemes Synchronize Electron Transfer Rates

Anaerobic microorganisms of the Geobacter genus are effective electron sources for the synthesis of nanoparticles, for bioremediation of polluted water, and for the production of electricity in fuel cells. In multistep reactions, electrons are transferred via iron/heme cofactors of c‐type cytochromes from the inner cell membrane to extracellular metal ions, which are bound to outer membrane cytochromes. We measured electron production and electron flux rates to 5×10⁵ e s^?1 per G. sulfurreducens. Remarkably, these rates are independent of the oxidants, and follow zero order kinetics. It turned out that the microorganisms regulate electron flux rates by increasing their Fe²⁺/Fe³⁺ ratios in the multiheme cytochromes whenever the activity of the extracellular metal oxidants is diminished. By this mechanism the respiration remains constant even when oxidizing conditions are changing. This homeostasis is a vital condition for living systems, and makes G. sulfurreducens a versatile electron source.     

Inductive heating and E to H transitions in capacitive discharges

Capacitive discharges have classically been modeled in the electrostatic approximation. However, electromagnetic effects become significant if the excitation wavelength lambda and the plasma skin depth delta are not infinite. An electromagnetic model valid in the entire range of lambda and delta of practical interest is solved. We find that the plasma may either be sustained by the usual capacitive (E) field or by an inductive (H) field, and that the discharge experiences E to H transitions as the voltage between the electrodes is raised.     

Going-down functors, the Künneth formula, and the Baum-Connes conjecture

We study the connection between the Baum-Connes conjecture for a locally compact group G with coeefficient A and the Künneth formula for the K-theory of tensor products by the corresponding crossed product . The main tool for this is obtained by an application of a general reduction procedure which allows us to analyze certain functors connected to the topological K-theory of a group in terms of their restrictions to compact subgroups. We also discuss several other interesting applications of this method, including a general extension result for the Baum-Connes conjecture.