Hypervalent iodine-mediated oxygenative phenol dearomatization reactions

Both λ³- and λ⁵-iodanes have proven to be useful reagents in the oxygenative dearomatization of phenols, and exploitations of their chemistry in the conception of both substrate- and reagent-controlled asymmetric variants of such a transformation of great value for natural product synthesis have shown evident signs of success. Moreover, the use of stabilized IBX (i.e., SIBX) in our methodology for O-demethylation of 2-methoxyphenols, which relies on the same key oxygenating dearomatization event, is reported here to be much more efficacious than that of IBX itself in the chemoselective one-step conversion of homovanillyl alcohol into hydroxytyrosol, and bergenin into norbergenin.     

Dilatation thermique anormale et caractere en couches des metavanadates MV2O6 (M = Ca,Cd, Zn,Mg, Pb)

The variations of cell parameters and thermal expansion tensors of metavanadates MV₂O₆ have been measured in the range 77–295 K. The thermal expansion anisotropy is characteristic of layer structures especially for brannerite-type structures (M = Cd, Zn, Mg); this anisotropy is explained by the presence of [VO₅] polyhedra, such as occur in the V₂O₅ layer structure. For CaV₂O₆ the variation of thermal expansion as a function of temperature is abnormal: peaks, typical of a diffuse transition, are observed at 260 K for α₁(T) and α₃(T) curves. The temperature anomaly is reduced when cadmium is substituted for calcium.     

Reaction de metathese des olefines induite photochimiquement en presence d'un complexe de metal de transition. IV.- etude cinetique de l'interconversion catalysee cis-trans du butene-2.

The cis-trans interconversion of olefins in the system W(CO)₆ + CCl₄ + 2-butene is studied, both with initial irradiation of a solution of W(CO)₆ in CCl₄ (photoinduction), and with continuous irradiation of the system, for cis- and trans-butene concentrations between 0.09 and 6.0 M. Analysis of the results of the photoinduction experiments (rate of conversion and kinetic law as a function of the initial concentration of the olefin) allowed us to propose a simple kinetic scheme comprising a cis-trans interconversion of 2-butene and olefin-catalyzed destruction of the catalytic entity (k₂ = (0.62 ± 0.06)x10^?4 M s^?1). In the continuous irradiation experiments the final distribution of the olefin was independent of the initial butene concentration (cis-2-butene/trans-2-butene 3.0) and the reaction kinetics are of first-order (k_obs = (3±1) x10^?4 s^?1. Comparison of the two experiments suggests continuous photochemical regeneration of the catalytically active entity. The first-order reaction kinetics are in agreement with a carbene-metal carbonyl structure of the intermediate     

Preparation,analyses et etudes thermochimiques du tetrafluorure de tellure

Tellurium Tétrafluoride has been prepared and various analysis (chemical, thermal, Xray) have been performed. Heat of fusion (δH_fus = 3,02 Kcal.mol^-1), and calorific capacity of solid TeF₄ from 298 to 402°K (Cp_s = 30 cal.K^-1. mol^-1) and of liquide TeF₄ at 423°K (Cp₁ = 31, 1 cal.K.^-1.mol^-1) have been determined Enthalpic values are given.     

Effect of tethered and free microfibrillated cellulose (MFC) on the properties of paper composites

High strength and low gas permeability cellulosic composites were produced using the papermaking technology with a commercial microfibrillated cellulose (MFC). The effect of blending MFC with hardwood fibers was compared to the direct refining of the fibers with and without polyamideamine-epichlorohydrin (PAE) addition. The addition of MFC, free or tethered, to pulp fibers combined with PAE can increase the dry strength and wet strength of cellulosic materials by an order of magnitude. Air permeability of the composites decreases by up to orders four of magnitude with MFC addition. The hypothesis that refining wood fibers can produce tethered MFC which provides equivalent strength properties but significant drainage benefits was proven. Furthermore, major benefits in paper formation uniformity (fiber distribution homogeneity) were achieved with refined fibers.     

Synthesis of Thiophene-Substituted Spiropyrans and Spirooxazines,Precursors of Photochromic Polymers

The synthesis of spiropyrans 11 and 12 and spirooxazines 13–17 containing a thiophene moiety is described. Two different synthetic approaches were used. The spectrokinetic properties of these new compounds are reported.     

Engineering paper as a substrate for blood typing bio-diagnostics

The effect of paper structure on blood typing visualization was quantified and analyzed to engineer low-cost diagnostics. Commercial and experimental papers varying in fibre composition, basis weight, density and porosity were investigated for their ability to separate agglutinated (blood interacted with specific antibodies) from non-agglutinated (blood interacted with non-specific antibodies) red blood cells (RBCs). Antibodies solutions and blood samples were sequentially absorbed on paper, allowed to interact, eluded with a saline solution, and the intensity of the remaining blood spot was quantified by image analysis. The efficiency and clarity of RBC separation was quantified with the relative intensity (R.I.) index defined as the intensity ratio of the non-specific test over the specific system; the lower the R.I., the better is the separation between a positive from a negative test. Thick and dense papers are improper for blood typing as they retain indiscriminately both agglutinated and non-agglutinated RBCs. Thin and porous papers provided the best performance. The R.I. index (the lower the better) increased fairly linearly with paper density and thickness but inversely proportionally with paper pore size. The type of fibres played a minor role. The paper structure is critical in the design of blood typing assay. However, it is only one element of the diagnostic system to engineer with the interactions RBC-antibody-paper.     

Solid-state of pharmaceutical compounds

This article summarizes the different steps needed for a proper design and monitoring of the solid-state in pharmaceutical industry in order to fulfill the requirements of the guideline dealing with polymorphism of the International Conference of Harmonization. This revised version was published online in July 2006 with corrections to the Cover Date.     

Functionalized Conducting Polymers—Towards Intelligent Materials

Organic conjugated polymers and oligomers constitute a three-dimensional network of molecular wires, in which all monomeric units can be functionalized with various prosthetic groups. By varying the nature of these groups, specific interactions with external physical or chemical phenomena can be developed in these materials, leading to molecular devices such as sensors, transducers, memories and logic operators. Chemists have already mastered the realization of many of these functional elements, which mimic those existing in organized beings.The further assembly of these elements in multifunctionalized organic conducting polymers and oligomers will represent the next step towards intelligent materials.