Stereoretentive Olefin Metathesis Made Easy: In Situ Generation of Highly Selective Ruthenium Catalysts from Commercial Starting Materials.

The in situ preparation of highly stereoretentive ruthenium-based metathesis catalysts is reported. This approach completely avoids the isolation of intermediates and air-sensitive catalysts, thus allowing for the rapid access and evaluation of numerous dithiolate Ru catalysts. A procedure was established to perform cross-metathesis reactions without the use of a glovebox, and on a small scale even Schlenk techniques are not required. Consequently, the chemistry displayed in this report is available to every practicing organic chemist and presents a powerful approach for the identification of new stereoretentive catalysts.

A Two-Step Oxidative Cleavage of 1,2-Diol Fatty Esters into Acids or Nitriles by a Dehydrogenation-Oxidative Cleavage Sequence.

Dehydrogenative oxidation of vicinal alcohols catalyzed by a commercially 64 wt.% Ni/SiO2 catalyst leads to the formation of α-hydroxyketone. This first step was developed without additional solvent according to two protocols: "under vacuum" or "with an olefin scavenger". The synthesis of ketols was carried out with good conversions and selectivities. The recyclability of the supported nickel was also studied. Acyloin was then cleaved with oxidative reagent "formic acid/hydrogen peroxide", which is cheap and can be used on a large scale for industrial oxidation processes. The global yield of this sequential system was up to 80 % to pelargonic acid and azelaic acid monomethyl ester without intermediate purification. By treating the acyloin intermediate with hydroxylamine, nitriles were obtained with a good selectivity.

Bleaching Earths as Powerful Additives for Ru-Catalyzed Self-Metathesis of Non-Refined Methyl Oleate at Pilot Scale.

A practical and cost-effective ruthenium-catalyzed self-metathesis of non-refined methyl oleate (85 %) derived from very high oleic sunflower oils was demonstrated at pilot scale using a robust and kg-scale commercially available SIPr-M71 pre-catalyst. The simple addition of 1 wt % bleaching earths (Tonsil 110FF) to a thermally pretreated oil could efficiently prevent catalyst deactivation. Remarkably, without the need for filtration, the catalytic system was able to achieve a turnover number (TON) of more than 744 000 at a catalyst loading of only 1 ppm. At large scale (up to 200 kg), the equilibrium of the self-metathesis reaction was reached within 1 hour at 50 °C under neat conditions at a very low 5 ppm catalyst loading to produce the expected primary metathesis products (PMP), that is, 9-octadecene and dimethyl-9-octadecenoate, with a productive TON of 94900.

Synthesis of High-Molecular-Weight Multifunctional Glycerol Polyhydroxyurethanes PHUs.

Glycerol carbonate acrylate is a 5-membered cyclic carbonate synthesized from glycerol that is used as a chemical coupling agent and has proven highly suitable for use in the synthesis of multifunctional polyhydroxyurethanes (PHUs). The multifunctionality of the structure of PHUs is determined by the density of the carbon-amine groups generated by the Aza-Michael reaction and that of the urethane groups and adjacent primary and secondary hydroxyl groups generated by aminolysis. Glycerol carbonate acrylate is polymerized with polyfunctional mono-, di-, tri, and tetra-amines, by type-AB polyaddition, either in bulk or in solution, through stepwise or one-pot reaction strategies in the absence of added catalysts. These approaches result in the generation of linear, interchain, and crosslinked structures, through the polyaddition of linear and branched amines to the ethylene and cyclic carbonate sites of glycerol carbonate acrylate. The resulting collection of organic molecules gives rise to polyethylene amino ester PHUs with a high molar mass, exceeding 20,000 g·mol(-1), with uniform dispersity.

An experimental design based strategy to optimize a capillary electrophoresis method for the separation of 19 polycyclic aromatic hydrocarbons.

Because of their high toxicity, international regulatory institutions recommend monitoring specific polycyclic aromatic hydrocarbons (PAHs) in environmental and food samples. A fast, selective and sensitive method is therefore required for their quantitation in such complex samples. This article deals with the optimization, based on an experimental design strategy, of a cyclodextrin (CD) modified capillary zone electrophoresis separation method for the simultaneous separation of 19 PAHs listed as priority pollutants. First, using a central composite design, the normalized peak-start and peak-end times were modelled as functions of the factors that most affect PAH electrophoretic behavior: the concentrations of the anionic sulfobutylether-ß-CD and neutral methyl-ß-CD, and the percentage of MeOH in the background electrolyte. Then, to circumvent computational difficulties resulting from the changes in migration order likely to occur while varying experimental conditions, an original approach based on the systematic evaluation of the time intervals between all the possible pairs of peaks was used. Finally, a desirability analysis based on the smallest time interval between two consecutive peaks and on the overall analysis time, allowed us to achieve, for the first time in CE, full resolution of all 19 PAHs in less than 18 min. Using this optimized capillary electrophoresis method, a vegetable oil was successfully analyzed, proving its suitability for real complex sample analysis.

Optimizing separation conditions of 19 polycyclic aromatic hydrocarbons by cyclodextrin-modified capillary electrophoresis and applications to edible oils.

For the first time, the separation of 19 polycyclic aromatic hydrocarbons (PAHs) listed as priority pollutants in environmental and food samples by the United States Environmental Protection Agency (US-EPA) and the European Food Safety Authority was developed in cyclodextrin (CD)-modified capillary zone electrophoresis with laser-induced fluorescence detection (excitation wavelength: 325 nm). The use of a dual CD system, involving a mixture of one neutral CD and one anionic CD, enabled to reach unique selectivity. As solutes were separated based on their differential partitioning between the two CDs, the CD relative concentrations were investigated to optimize selectivity. Separation of 19 PAHs with enhanced resolutions as compared with previous studies on the 16 US-EPA PAHs and efficiencies superior to 1.5 × 10(5) were achieved in 15 min using 10mM sulfobutyl ether-ß-CD and 20mM methyl-ß-CD. The use of an internal standard (umbelliferone) with appropriate electrolyte and sample compositions, rinse sequences and sample vial material resulted in a significant improvement in method repeatability. Typical RSD variations for 6 successive experiments were between 0.8% and 1.7% for peak migration times and between 1.2% and 4.9% for normalized corrected peak areas. LOQs in the low µg/L range were obtained. For the first time in capillary electrophoresis, applications to real vegetable oil extracts were successfully carried out using the separation method developed here.

Use of response surface methodology to optimize the simultaneous separation of eight polycyclic aromatic hydrocarbons by capillary zone electrophoresis with laser-induced fluorescence detection.

Polycyclic aromatic hydrocarbons (PAHs) are among the most targeted contaminants by international regulatory institutions. There is thus a need for fast, selective and sensitive analytical methods to quantify these compounds at trace levels in complex samples. This article focuses on the optimization by means of an experimental design of a CE method with laser-induced fluorescence detection for the fast simultaneous separation of 8 heavy PAHs among food and environmental priority pollutants: benzo(a)pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene, benzo(k)fluoranthene, and benzo(ghi)perylene. In this method, capillary zone electrophoresis with a mixture of an anionic sulfobutyl ether-ß-cyclodextrin (SBE-ß-CD) and a neutral methyl-ß-cyclodextrin (Me-ß-CD) was used to separate PAHs, on the basis of their differential distribution between the two CDs. First, the factors most affecting PAH electrophoretic behavior were identified: SBE-ß-CD and Me-ß-CD concentrations and percentage of methanol added to the background electrolyte. Then, a response surface strategy using a central composite design was carried out to model the effects of the selected factors on the normalized migration times. To optimize the separation, desirability functions were applied on modeled responses: normalized migration time differences between peak end and peak start of two consecutive peaks, and overall analysis time. From the model, predicted optimum conditions were experimentally validated and full resolution of all 8 PAHs was achieved in less than 7min using a borate buffer composed of 5.3mM SBE-ß-CD, 21.5mM Me-ß-CD and 10.3% MeOH. This CE separation method was successfully applied to real edible oil analysis.

Selective synthesis of 1-O-alkyl(poly)glycerol ethers by catalytic reductive alkylation of carboxylic acids with a recyclable catalytic system.

(Poly)glycerol monoethers were synthesized in good yield and selectivity by the catalytic reductive alkylation of glycerol, diglycerol, and triglycerol with readily available, cheap and/or bio-sourced carboxylic acids. The reaction was catalyzed by 1 mol % of Pd/C under 50 bar H(2) using an acid ion-exchange resin as a recyclable cocatalyst. The catalytic system was recycled several times, and a mechanism is proposed for this transformation.