Comparison of alumina and boehmite in (APP/MPP/metal oxide) ternary systems on the thermal and fire behavior of PMMA

A comparison of alumina (Al₂O₃) and boehmite (AlOOH) in (ammonium polyphosphate/melamine polyphosphate/metal oxide) ternary system was performed in poly(methyl methacrylate) on thermal and fire‐resistance properties. A Design of Experiments (DoE) was then done for highlighting the best formulation out of both ternary systems. Laser flash analysis and scanning electron microscopy helped to explain some of the observations made by DoE. Mechanisms in both ternary systems during degradation also were investigated and modes of action could be presented based on pyrolysis‐combustion flow calorimetry, Raman spectroscopy and X‐ray diffraction. Copyright © 2011 John Wiley & Sons, Ltd.     

Photocatalytic α‐Tertiary Amine Synthesis via C−H Alkylation of Unmasked Primary Amines

A practical, catalytic entry to α,α,α‐trisubstituted (α‐tertiary) primary amines by C?H functionalisation has long been recognised as a critical gap in the synthetic toolbox. We report a simple and scalable solution to this problem that does not require any in situ protection of the amino group and proceeds with 100 % atom‐economy. Our strategy, which uses an organic photocatalyst in combination with azide ion as a hydrogen atom transfer (HAT) catalyst, provides a direct synthesis of α‐tertiary amines, or their corresponding γ‐lactams. We anticipate that this methodology will inspire new retrosynthetic disconnections for substituted amine derivatives in organic synthesis, and particularly for challenging α‐tertiary primary amines.     

Liquid chromatography coupled to tandem mass spectrometry for the analysis of inositol hexaphosphate after solid-phase extraction

Inositol hexaphosphate, a naturally occurring component in cereals and plants, is the main reserve and principal carrier of phosphate. Inositol hexaphosphate is also found in biological fluids such as urine, plasma, or whole blood. Moreover, inositol hexaphosphate is studied for its pharmaceutical applications. Liquid chromatography coupled to mass spectrometry is now the reference method for small analyte determination. However, the specific quantitation of polyanionic molecules in the biological matrix is still challenging.

In this article, a bioanalytical method for the extraction and determination of inositol hexaphosphate in whole blood is described by using solid-phase extraction followed by liquid chromatography–mass spectrometry/mass spectrometry using selected reaction monitoring mode for its specificity.

Using pentylamine in excess, an ion pair is created, enhancing sensitivity by avoiding the presence of many Na adducts on the phosphate functions of inositol hexaphosphate. Moreover, hexafluoroisopropanol was added to stabilize the ion pairs that were created. Then, a specific extraction of inositol hexaphosphate by anion-exchange solid-phase extraction was developed, resulting in an extraction recovery of 89%. The linearity of the method was verified between 0.78 and 100 µg/mL, and both accuracy and precision were greater than 85%. Finally, the endogenous rate of inositol hexaphosphate was measured in the whole blood of mice and was estimated at 2 µg/mL.     

Process for preparing Ezetimibe intermediate by enantioselective CBS catalyzed ketone reduction with BH3-DEA prepared in situ

The (S) alcohol in the benzylic position of compound 2, a key intermediate in the synthesis of the cholesterol lowering agent Ezetimibe, was introduced by the (R)-MeCBS catalyzed asymmetric carbonyl reduction of ketone 1 using borane diethylaniline complex (BDEA) as the reducing agent. The latter was prepared in situ from sodium borohydride (NaBH₄), diethylaniline (DEA) and dimethylsulfate (DMSO₄). BDEA prepared in situ offers considerable advantages from the industrialization standpoint (cost and stability on storage of the reagents) over commercial solutions of BH₃-THF (BTHF) or BH₃-DMS (BMS). The effect of critical reaction parameters such as addition mode of reagent, temperature, solvent, reaction quenching as well as LiCl addition on the selectivity has been examined. This reaction has been successfully applied in the process for the preparation of key intermediate 2 for Ezetimibe.     

How stereochemistry influences the taste of wine: Isolation,characterization and sensory evaluation of lyoniresinol stereoisomers

Wine expresses its beauty by sending a sensory message to the taster through molecules coming from grapes, yeast metabolism or oak wood. Among the compounds released during barrel aging, lyoniresinol has been recently reported as a relevant contributor to wine bitterness. As this lignan contains three stereogenic carbons, this work aimed at investigating the influence of stereochemistry on wine taste by combining analytical and sensorial techniques. First, an oak wood extract was screened by Liquid Chromatography–High Resolution Mass Spectrometry to target isomers separable in a symmetric environment and a diastereoisomer called epi-lyoniresinol was isolated for the first time. Then, an original racemic resolution based on natural xylose-derivatives was carried out to obtain lyoniresinol enantiomers. Chiroptical spectroscopic measurements associated with theoretical calculations allowed the unambiguous determination of their absolute configuration. The taste properties of all these stereoisomers revealed that only one lyoniresinol enantiomer is strongly bitter whereas the other one is tasteless and the diastereoisomer is slightly sweet. The presence of these three compounds was established in an oaked Bordeaux wine by chiral and non-chiral chromatography, suggesting the significant influence of stereochemistry on wine taste.     

Optimization of a molecular mechanics force field for type-II polyoxometalates focussing on electrostatic interactions: a case study

In this study, we have focussed on type-II polyanions such as [M(7)O(24)](6-), and we have developed and validated optimized force fields that include electrostatic and van der Waals interactions. These contributions to the total steric energy are described by the nonbonded term, which encompasses all interactions between atoms that are not transmitted through the bonds. A first validation of a stochastic technique based on genetic algorithms was previously made for the optimization of force fields dedicated to type-I polyoxometalates. To describe the new nonbonded term added in the functional, a fixed-charged model was chosen. Therefore, one of the main issues was to analyze that which partial atomic charges could be reliably used to describe these interactions in such inorganic compounds. Based on several computational strategies, molecular mechanics (MM) force field parameters were optimized using different types of atomic charges. Moreover, the influence of the electrostatic and van der Waals buffering constants and 1,4-interactions scaling factors used in the force field were also tested, either being optimized as well or fixed with respect to the values of CHARMM force field. Results show that some atomic charges are not well adapted to CHARMM parameters and lead to unrealistic MM-optimized structures or a MM divergence. As a result, a new scaling factor has been optimized for Quantum Theory of Atoms in Molecules charges and charges derived from the electrostatic potential such as ChelpG. The force fields optimized can be mixed with the CHARMM force field, without changing it, to study for the first time hepta-anions interacting with organic molecules.     

Simultaneous determination of uranium carbide dissolution products by capillary zone electrophoresis

Separation and simultaneous determination of a number of organic acid anions (oxalate, mellitate, trimellitate and benzoate) and U(VI) with direct UV detection is developed for analysis of uranium carbide (UC) dissolution products by capillary zone electrophoresis (CZE). Reverse polarity mode is used. It is found that complex formation of U(VI) with carbonate, used as a carrier electrolyte, allows U(VI) to be determined, as negatively charged species, in a single run with organic acid anions. Some parameters such as pH value, composition of electrolyte and detection wavelength are optimized. Under the chosen conditions (carbonate buffer (ionic strength of 100 mM), pH 9.8, 0.15 mM tetradecyltrimethylammonium bromide (TTAB)) a complete separation is achieved. Calibration plots are linear in two ranges of concentration for U(VI) (∼1 × 10⁻⁵ to 1 × 10⁻³), mellitate and trimellitate (∼5 × 10⁻⁶ to 5 × 10⁻⁴), and about one range (∼1 × 10⁻⁴ to 5 × 10⁻³) for oxalate and benzoate. Accuracy of the procedure is checked by the “added-found” method in standard mixture solutions. Relative standard deviation is within the range of 2–10% and the recovery is in the range of 90–110%. This method is applied for the analysis of real UC dissolution samples.     

Organomanganese (II) reagents XIX. Acylation of organomanganese chlorides by carboxylic acid chlorides in THF: A clear improvement in the field of the preparation of ketones from organomanganese compounds

Organomanganese chloride reagents react with carboxylic acid chlorides, in THF, to give the corresponding ketones in excellent yields. The reaction is of broad scope, it is very interesting from practical and economical point of view since organomanganese chlorides (in THF) are the most stable and cheap organomanganese reagents. With methyl, aryl, alkenyl and s- or t-alkylmanganese chlorides, the acylation is advantageously performed in the presence of a catalytic amount of copper chloride. This new procedure allows to prepare methyl, aryl and alkenylketones as well as s- or t-alkylketones in good yields.