Use of Limonene Epoxides and Derivatives as Promising Monomers for Biobased Polymers.

(R)-Limonene, a renewable terpene, and its epoxidized derivatives, i. e. limonene epoxides, have prompted growing attention over the last decade as building blocks for the synthesis of biobased monomers and polymers. With the goal of replacing petroleum-based polymers several polymerization techniques have been applied on limonene oxide and limonene dioxide monomers. This paper aims to contribute to the literature by presenting a review dedicated to limonene oxide and dioxide as raw monomers of renewable origin for the development of biobased polymers. The polymerization techniques described are namely the homopolymerization, the copolymerization with carbon dioxide and anhydrides, and the copolymerization of limonene epoxide-based monomers. Limonene oxide polymerizations will be investigated first, followed by limonene dioxide polymerizations.

Quality Control of a Functionalized Polymer Catalyst by Energy Dispersive X-ray Spectrometry (EDX or EDS).

Energy dispersive X-ray spectrometry (EDX or EDS) is a technique often implemented on scanning electron microscopes and a regularly used method for qualitative characterization of solid catalysts. This Technical Note reports a method for the determination of the metal content in a sulfonated polyether ether ketone in the form of an indium(III) salt. The possibility of quantitative determination of the sulfur/indium ratio by EDX was assessed by calibration with two indium salts (sulfide and sulfate) readily available in good purity. The accuracy of the uncorrected instrument response was better than 1% under our conditions. A protocol for investigating the metal content of the solid catalyst is proposed, also providing information about the homogeneity of the metal distribution. Because of the simplicity of the sample preparation, the small quantity of material needed, and the rapidity of the EDX measurements, the method appears to be promising for quantitative characterization of solid catalysts.

Quantitative Ligand Affinity Scales for Metal Triflate Salts: Application to Isomer Differentiation.

Owing to the importance of metal triflates in catalysis, the affinity of the cationic center for a selection of organic ligands was explored for InIII and ZnII triflates. The organic Lewis bases include a variety of carbonyls (amides, unsaturated ketones, a lactone) and cyclic 1,2-diols. The relative affinity of the ligands for the cationic center in triflates was quantitatively determined on the basis of relative ion concentrations determined by electrospray-ionization mass spectrometry. The affinity scales were discussed with reference to gas-phase proton basicity and Lewis basicity scales. Structural isomers and stereoisomers display significant affinity differences in several cases. In the case of isomer mixtures, a model describing the relative peak intensities in the mass spectra was developed. On this basis, an isomer titration method was set up. Remarkably, this MS-based method overcame the blindness of mass spectrometry to isomers without the need for isotope labeling or MS/MS experiments. This model may prove to have applications in analytical chemistry and catalysis.

Application of cooperative iron/copper catalysis to a palladium-free borylation of aryl bromides with pinacolborane.

A new cooperative copper/iron catalysis for the borylation of various aryl bromides with pinacolborane, at -10 °C, is reported. Use of the toxic, precious metal Pd is avoided. The mechanism of the protodebromination side reaction is discussed.

A quantitative approach of the interaction between metal triflates and organic ligands using electrospray mass spectrometry.

The interaction between two Lewis "superacid" catalysts Zn(OTf)(2) and In(OTf)(3) and series of amide and phosphate ligands is quantitatively characterized by electrospray ionization mass spectrometry (ESI-MS). A specific feature of the ESI-MS spectra of the mixture of metal triflates and Lewis bases is the formation of ionic adducts resulting from the displacement of one triflate anion by two neutral ligands. A ligand competition model is developed, which describes the relative intensities of the ionic adducts as a function of relative ligand concentrations. The relative affinities deduced from the ligand competition method are combined in an affinity scale for the metal triflate.

Biomimetic cationic polyannulation reaction catalyzed by Bi(OTf)3: cyclization of 1,6-dienes, 1,6,10-trienes, and aryl polyenes.

Nonactivated trienes and aryltrienes were cyclized into polycyclic compounds in good to excellent yields under bismuth triflate catalysis in a biomimetic fashion. The reaction showed broad applicability and allowed for the formation of functionalized bicyclic to tetracyclic structures from simple precursors in one pot. For some specific substrates, the cyclization was followed by a methyl shift as encountered in terpenoid biosynthesis.

Relative basicities toward metal triflates Lewis acids by electrospray mass spectrometry.

The relative Lewis basicity of a series of phosphoryl compounds toward cations M(n+)(OTf)(n-1) derived from triflate salts, M(OTf)(n), is ranked using electrospray mass spectrometry according to competitive adduct formation.

Mass spectrometric characterization of metal triflates and triflimides (Lewis superacid catalysts) by electrospray ionization and tandem mass spectrometry.

Trifluoromethylsulfonate (triflate) and bis(trifluoromethylsulfonyl)imide (triflimide) salts, well-known Lewis acid catalysts, present some difficulty in their characterization. By using nitromethane as the solvent, useful electrospray mass spectra in positive and negative ion mode were obtained for salts of metals in oxidation states +2 and +3. In positive mode, addition of a strong Lewis base (triphenylphosphine oxide, TPPO), capable of displacing a triflate (TfO(-)) or a triflimide (Tf(2)N(-)) anion, is necessary for obtaining useful spectra. Under these conditions of solvent and added ligand, the most abundant ions were [M(2+)(A(-))(TPPO)(2)](+) or [M(3+)(A(-))(2)(TPPO)(2)](+) with A(-) = TfO(-) or Tf(2)N(-). The MS/MS spectra of these diagnostic ions provide additional analytical information. The breakdown curves, in the form of % dissociated as a function of the ion activation energy, offer a mean for investigating the bonding in these ions.

An opportunity for Mg-catalyzed Grignard-type reactions: direct coupling of benzylic halides with pinacolborane with 10 mol % of magnesium.

Mg in catalytic amounts as the only metal permits the reductive coupling between benzyl halides and pinacolborane. HBpin acts both as an electrophile and as a reducing agent to regenerate an organomagnesium species in situ. An hydride oxidation mechanism is proposed on the basis of DFT calculations.

Aluminium(III) trifluoromethanesulfonate as an efficient catalyst for the intramolecular hydroalkoxylation of unactivated olefins: experimental and theoretical approaches.

The Al(OTf)(3)-catalyzed cycloisomerization of unactivated unsaturated alcohols was studied from experimental and theoretical points of view. A series of cyclic ethers was obtained in excellent yields and regioselectivities. This catalyst system provides one of the most straightforward routes to cyclic ethers with Markovnikov-type regioselectivity under mild conditions. Theoretical and NMR studies were carried out in order to better determine the mechanism of this reaction. The NMR studies were in agreement with preferential complexation of Al(OTf)(3) to the oxygen atom of the unsaturated alcohol, but did not exclude complexation to the double bond of the alcohol. Theoretical calculations indicated strong acidification of the hydroxyl proton when Al(OTf)(3) was complexed to the alcohol oxygen atom. A plausible catalytic cycle for the Al(OTf)(3)-catalyzed intramolecular hydroalkoxylation of unactivated olefins is proposed.