The Vapor-Liquid Polycondensation of Cyclohexylphosphoric Dichloride with Hydroquinone

The vapor-liquid polycondensation of cyclohexylphosphoric dichloride with hydroquinone was investigated. The influence of the temperature, reaction time, base concentration, and molar ratio of reagents on the yield, inherent viscosity, and molecular weight of the obtained polymer was studied. Second order, central, composite, rotatable experimental design was used in order to carry out this work and to mark limits of the experimental field for optimal yields and high inherent viscosities.     

A simple calibration procedure for volatile organic compounds sampling in air with adsorptive solid-phase microextraction fibres

Adsorptive solid-phase microextraction (SPME) fibres have proven to be a reliable means of sampling volatile organic compounds (VOCs) in air. In this work, polydimethylsiloxane/carboxen (PDMS/CAR) fibres were used to test a new approach of air sampling strategy with SPME in the lab which could lighten calibration procedure and enhance the use of this already rapid, simple, convenient and cost effective sampling technique. Indeed, only one curve can be used whatever the extraction time chosen by the analyst under constant conditions of air velocity and temperature. Ficks' law of diffusion was used to model SPME grab sampling when the fibre was totally exposed to the air sample. Experimental sampling rates were then determined by GC-FID for different sampling conditions, i.e. in a flowing air stream of known velocity ("dynamic mode") and in a stagnant air ("static mode"). These sampling rates were found to be 3.50 and 17.80 mL min(-1) for acetone, 4.06 and 21.20 mL min(-1) for 1,2-dichloroethane, 5.10 and 27.80 mL min(-1) for toluene and 5.36 and 30.80 mL min(-1) for butyl acetate, for static and dynamic sampling modes respectively. Deviation from linearity of the calibration curves, indicating that a significant fraction of the adsorption sites are occupied, were determined. They were found to be approximately equal to 0.9, 1.57, 3.82 and 4.37 nmol for acetone, dichloroethane, toluene and butyl acetate, respectively. Experimentally determined sampling rates of these isolated compounds were also valid when a complex equimolar gaseous mixture was investigated, but deviation from linearity appears earlier. Then, for a given application, sampling times should be chosen very carefully to avoid competitive adsorption and hence, bad quantitative analysis results.     

Thiazole‐Based γ‐Building Blocks as Reverse‐Turn Mimetic to Design a Gramicidin S Analogue: Conformational and Biological Evaluation

This paper describes the ability of a new class of heterocyclic γ‐amino acids named ATCs (4‐amino(methyl)‐1,3‐thiazole‐5‐carboxylic acids) to induce turns when included in a tetrapeptide template. Both hybrid Ac‐Val‐(R or S)‐ATC‐Ile‐Ala‐NH₂ sequences were synthesized and their conformations were studied by circular dichroism, NMR spectroscopy, MD simulations, and DFT calculations. It was demonstrated that the ATCs induced highly stable C₉ pseudocycles in both compounds promoting a twist turn and a reverse turn conformation depending on their absolute configurations. As a proof of concept, a bioactive analogue of gramicidin S was successfully designed using an ATC building block as a turn inducer. The NMR solution structure of the analogue adopted an antiparallel β‐pleated sheet conformation similar to that of the natural compound. The hybrid α,γ‐cyclopeptide exhibited significant reduced haemotoxicity compared to gramicidin S, while maintaining strong antibacterial activity.     

Antibacterial poly(ethylene terephthalate) surfaces obtained from thymyl methacrylate polymerization

Thymol, an antibacterial agent was used for the preparation of a methacrylic monomer. The conventional and atom transfer radical (ATRP) polymerizations of this monomer were studied using different conditions. Then, the functionalization of poly(ethylene terephthalate) (PET) films by “grafting from” ATRP using this monomer was investigated. In this aim, a three steps procedure was developed. The surfaces were first treated by NH₃ plasma treatment to incorporate primary amino functions. Then, in a second step, ATRP initiator was grafted by reaction with bromoisobutyryl bromide. Surface initiated ATRP of thymyl methacrylate was performed in solution in the presence of a sacrificial initiator. The efficiency of these reactions was confirmed by X‐ray photoelectron spectroscopy. Wetting properties and surface energy were found to vary systematically depending to the type of functionalization and grafting. The poly(thymyl methacrylate)‐grafted PET surfaces exhibit resistance to bacterial adhesion toward Pseudomonas aeruginosa, Listeria monocytogenes, and Staphylococcus aureus strains. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1975–1985     

Photoswitching Kinetics and Phase‐Sensitive Detection Add Discriminative Dimensions for Selective Fluorescence Imaging

Non‐invasive separation‐free protocols are attractive for analyzing complex mixtures. To increase selectivity, an analysis under kinetic control, through exploitation of the photochemical reactivity of labeling contrast agents, is described. The simple protocol is applied in optical fluorescence microscopy, where autofluorescence, light scattering, as well as spectral crowding presents limitations. Introduced herein is OPIOM (out‐of‐phase imaging after optical modulation), which exploits the rich kinetic signature of a photoswitching fluorescent probe to increase selectively and quantitatively its contrast. Filtering the specific contribution of the probe only requires phase‐sensitive detection upon matching the photoswitching dynamics of the probe and the intensity and frequency of a modulated monochromatic light excitation. After in vitro validation, we applied OPIOM for selective imaging in mammalian cells and zebrafish, thus opening attractive perspectives for multiplexed observations in biological samples.     

Synthesis and reactivity of pyrrolo[3,2-d][1,3]oxazine-2,4-dione. Access to new pyrrolo[3,2-e][1,4]diazepine-2,5-diones

A convenient synthesis of pyrrolo[3,2-d][1,3]oxazine-2,4-dione 4 is described and its reactivity towards various nucleophiles studied. The regioselective ring opening of anhydride 4 or its N-alkylated analog 25 in the presence of alanine or proline afforded, respectively, imidazolidinedione 22 and N-protected pyrrolo[3,2-e][1,4]diazepines 30 and 31 in a one-pot process. In a last part of this study, an alternative route to produce a library of eight non protected pyrrolo[3,2-e][1,4]diazepine-2,5-diones 35a–h is described to overcome the limited reactivity of anhydride 4.     

Synthesis, structure and reactivity of palladium(II) complexes of chiral N-heterocyclic carbene-imine and -amine hybrid ligands

The synthesis and structures of chiral N-heterocyclic carbene (NHC)-N-donor complexes of silver(I) and palladium(II) are reported. The X-ray structure of an NHC-imine silver(I) complex [((nPr)CN(CHPh))AgBr](2) exhibits an Ag(2)Br(2) dimer motif where the imine group is not coordinated to the silver atom. Reaction between 2 and [PdCl(2)(MeCN)(2)] gives the palladium(II) complex [(kappa(2)-(nPr)CN(CHPh))PdCl(2)](3) that contains a chelating NHC-imine ligand as shown by single-crystal X-ray diffraction. Slow hydrolysis of related complexes [(kappa(2)-(nPr)CN(CHPh))PdCl(2)](3) and [(kappa(2)-((Ph)(2)CH)CN(CHPh))PdCl(2)](4) using triethylammonium chloride and water lead to the precipitation of single crystals of insoluble NHC-amino palladium(II) complexes [(kappa(2)-(nPr)CN(H(2)))PdCl(2)](6) and [(kappa(2)-((Ph)(2)CH)CN(H(2)))PdCl(2)](7), respectively. In the solid state, complexes 6 and 7 both exhibit intermolecular hydrogen bonding between chlorine and an amino-hydrogen atom resulting in an infinite chain structure. Substitution of an amino hydrogen for an ethyl group gives the soluble complex [(kappa(2)-(iPr)CN((H)Et))PdCl(2)](12). Reaction between two equivalents of 2 and [PdCl(2)(MeCN)(2)] gives the di-NHC complex [(kappa(1)-(nPr)CN(CHPh))(2)PdCl(2)](5) that does not contain a coordinated imine as shown by single crystal X-ray diffraction. Conproportionation between 5 and an equivalent of [PdCl(2)(MeCN)(2)] to does not occur at temperatures up to 100 degrees C in CD(3)CN.     

Easy access to phosphonothioates

A new and particularly mild method for the formation of phosphorus-sulfur bonds has been achieved through base-catalyzed addition of thiocyanate to the corresponding H-phosphine oxide, phosphinate, or phosphonate. This reaction procedure offers many advantages: the use as starting material of a stable and not oxygen-sensitive phosphorus(v) species, particularly mild and nonaqueous reaction conditions and workup (a pivotal point for these sensitive phosphonothioates), and, through optimized access to thiocyanates, a wider scope of substrates. This method has been applied to achieve the synthesis of substrate analogues for the study of antibody-catalyzed hydrolysis of acetylcholinesterase inhibitor PhX (11).     

Direct infrared absorption spectroscopy of benzene dimer

The direct infrared (IR) absorption spectrum of benzene dimer formed in a free-jet expansion was recorded in the 3.3 μm region for the first time. This has led to the observation of the C-H stretching fundamental mode ν(13) (B(1u)), which is both IR and Raman forbidden in the monomer. Moreover, the IR forbidden and Raman allowed ν(7) (E(2g)) mode has been observed as well. These two modes were found to be red-shifted along with the IR allowed ν(20) (E(1u)) mode, as previously reported by Erlekam et al. [Erlekam; Frankowski; Meijer; Gert von Helden J. Chem. Phys.2006, 124, 171101], using ion-dip spectroscopy, contrary to the blue-shift predicted earlier by theoretical studies. The observation of the ν(13) band indicates that the symmetry is reduced in the dimer, confirming the T-shaped structure observed by Erlekam et al. Our experimental results have not provided any direct evidence for the presence of the parallel displaced geometry, the main objective of the present work, as predicted by theoretical calculations.     

Inductive heating with magnetic materials inside flow reactors

Superparamagnetic nanoparticles coated with silica gel or alternatively steel beads are new fixed-bed materials for flow reactors that efficiently heat reaction mixtures in an inductive field under flow conditions. The scope and limitations of these novel heating materials are investigated in comparison with conventional and microwave heating. The results suggest that inductive heating can be compared to microwave heating with respect to rate acceleration. It is also demonstrated that a very large diversity of different reactions can be performed under flow conditions by using inductively heated flow reactors. These include transfer hydrogenations, heterocyclic condensations, pericyclic reactions, organometallic reactions, multicomponent reactions, reductive cyclizations, homogeneous and heterogeneous transition-metal catalysis. Silica-coated iron oxide nanoparticles are stable under many chemical conditions and the silica shell could be utilized for further functionalization with Pd nanoparticles, rendering catalytically active heatable iron oxide particles.