Valeria Bugatti

New pyridine-derived N-oxides as chiral organocatalysts in asymmetric allylation of aldehydes

Abstract New chiral pyridine-type N -oxides 5a – e have been synthesized from (+)-α-pinene (+)- 6 in four steps including photochemical oxidation, followed by Krohnke annulation, α-alkylation, and N -oxidation. The methoxy derivative (+)- 5d exhibited the highest enantioselectivity as a catalyst in the title reaction, producing ( S )-(–)- 3 of 68% e.e.

Pectins filled with LDH-antimicrobial molecules: Preparation, characterization and physical properties

Nanohybrids of layered double hydroxide (LDH) with intercalated active molecules: benzoate, 2,4-dichlorobenzoate, para-hydroxybenzoate and ortho-hydroxybenzoate, were incorporated into pectins from apples through high energy ball milling in the presence of water. Cast films were obtained and analysed. X-ray diffraction analysis showed a complete destructuration of all nanohybrids in the pectin matrix. Thermogravimetric analysis showed a better thermal resistance of pectin in the presence of fillers, especially para-hydroxybenzoate and ortho-hydroxybenzoate. Mechanical properties showed an improvement of elastic modulus in particular for LDH-para-hydroxybenzoate nanohybrid, due probably to a better interaction between pectin matrix and nanohybrid layers. Barrier properties (sorption and diffusion) to water vapour showed improvement in the dependence on the intercalated active molecule, the best improvement was achieved for composites containing para-hydroxybenzoate molecules, suggesting that the interaction between the filler phase and the polymer plays an important role in sorption and diffusion phenomena. Incorporation of these active molecules gave antimicrobial properties to the composite films giving opportunities in the field of active packaging.

New procedures for the enantioselective oxidation of sulfides under stoichiometric and catalytic conditions

Abstract Acid-catalyzed oxidation of 2-furylcarbinols with hydrogen peroxide affords alternatively 2-(1-hydroperoxyalkyl)-furans 2 or 6-hydroperoxy-2H-pyran-3(6H)-ones 3. Compounds of the type 2 and 3 have been used as oxygen donors in efficient stoichiometric or catalytic procedures for the asymmetric sulfoxidation of prochiral sulfides in the presence of Ti(O-i-Pr)4/L-DET or Ti(O-i-Pr)4/(R)-BINOL/H2O systems. Positive non linear effects, (+)-NLE, were observed in the enantioselective oxidation of methyl p-tolyl sulfide, promoted by enantiomerically enriched Ti(IV)/BINOL/H2O complexes.

Physical and water sorption properties of chemically modified pectin with an environmentally friendly process.

A synthetic process was developed to modify pectin samples under solvent free conditions, obtaining pectin at increasing concentration of palmitic, oleic, and linoleic acids. The weight loss of the modified powders showed a degradation path very similar to the pure pectin, indicating that the pristine structure was preserved after the chemical modification. A decreasing mass of evaporating water on increasing the fatty acid concentration, in particular for the palmitic acid modification, indicated a reduced water sorption by the modified powders. Differential scanning calorimetry confirmed the thermogravimetric results and in addition indicated the crystallization of the lateral chains in the case of palmitic-acid-modified pectins. This result was confirmed by X-ray diffractograms of the palmitic acid samples, indicating the main crystallization of the form C, although possible orientation phenomena can be inferred. The sorption curves of either the pristine pectin or the modified samples showed a dual sorption behavior. The sorption curves were interpreted by the BET and GAB equations, both giving very similar results. Palmitic acid modification was very effective in reducing all sorption parameters, whereas in the case of oleic and linoleic acids, only at high concentrations was the hydrophobic influence detected.

Solvent-Free Synthesis of Modified Pectin Compounds Promoted by Microwave Irradiation

Microwave-assisted solvent-free modification of pectin was successfully accomplished, consisting in the esterification of several fatty acids by pectin alcoholic functions. The reaction was performed by simply mixing the reagents with a catalytic amount of the inorganic base (potassium carbonate) and irradiating the obtained mixture with microwaves for a short time (3–6 min). The replacement of the traditional heating with a microwave source allowed the development of a new synthetic protocol which provided increased yield of the final products, since it eliminates the small amount of degraded polysaccharide produced during traditional oil bath heating. The desired esters were fully characterized by FT-IR spectroscopy and thermogravimetric analysis.

Synthesis and physical properties of new layered double hydroxides based on ionic liquids: application to a polylactide matrix.

Ionic liquids based on tetraalkylphosphonium salts combined with different anions (decanoate and dodecylsulfonate) have been used as intercalating agents of layered double hydroxides (LDHs) by ion exchange. The synthesized phosphonium-treated LDHs display a dramatically improved thermal degradation and a significant increase in the interlayer distance as confirmed by thermogravimetric analysis (TGA) and X-ray Diffraction (XRD), respectively. To highlight the effect of thermostable ionic liquids, a very low amount of LDHs has been introduced within a polylactide (PLA) matrix and PLA/LDHs nanocomposites have been processed in melt by twin-screw extrusion. Then, transmission electron microscopy (TEM) analysis has been used to investigate the influence of ILs on the different morphologies of these nanocomposites. Even though the thermal stability of PLA matrix decreased, an excellent stiffness-toughness compromise has been obtained.

Synthesis and physical properties of new layered silicates based on ionic liquids: improvement of thermal stability, mechanical behaviour and water permeability of PBAT nanocomposites

Ionic liquids based on tetraalkylphosphonium and dialkyl imidazolium cations with long alkyl chains have been investigated as new surfactant agents for cationic exchange of lamellar silicates. The effect of the chemical nature of the ionic liquids on the thermal stability and on the surface energies of phosphonium-(MMT-201) and imidazolium-(MMT-I) treated montmorillonites have been studied by thermogravimetric analysis (TGA) and sessile drop method. Poly(butylene adipate-co-terephthalate) (PBAT) nanocomposites filled with a low amount of these modified-montmorillonites (2, 5 wt%) have been processed by melt mixing using a twin screw extruder. The mechanical, thermal, water and gas barrier properties of the corresponding nanocomposites as well as the distribution of the clay layers in PBAT matrix were determined.

Pectin functionalized with natural fatty acids as antimicrobial agent

Several pectin derivatives were prepared by chemical modifications of the polysaccharide with natural fatty acids. The obtained biodegradable pectin-based materials, pectin-linoleate, pectin-oleate and pectin-palmitate, were investigated for their antimicrobial activity against several bacterial strains, Staphylococcus aureus and Escherichia coli. Good results were obtained for pectin-oleate and pectin-linoleate, which inhibit the growth of the selected microorganisms by 50-70%. They exert the better antimicrobial activity against S. aureus. Subsequently, the pectin-oleate and the pectin-linoleate samples were coated on polyethylene films and were assessed for their capacity to capture the oxygen molecules, reducing its penetration into the polymeric support. These results confirmed a possible application of the new materials in the field of active food packaging.

Structuration of ionic liquids in a poly(butylene-adipate-co-terephthalate) matrix: its influence on the water vapour permeability and mechanical properties

The use of new building blocks based on phosphonium ionic liquids to develop polymeric materials combining a structuration on the nanoscale with the dramatic water vapour permeability and mechanical properties has been successfully investigated for the first time in a biopolymer matrix.

Ionic liquids–lignin combination: an innovative way to improve mechanical behaviour and water vapour permeability of eco-designed biodegradable polymer blends

In this work, the potential use of lignin combined with ionic liquids (ILs) has been investigated on the final properties of biodegradable polymer blends. Poly(butylene-adipate-co-terephtalate)–polylactide–lignin (PBAT–PLA–Lig) were melted blending in one pot by using phosphonium ionic liquids as new additives. The effect of incorporating 16 wt% of lignin and PLA and 1 wt% of ILs into PBAT matrix has been explored on the mechanical behaviour, the water vapour permeability, the thermal stability as well as the morphologies of PBAT–PLA–Lig–IL blends. In all cases, the lignin–ionic liquid combination leads to a good mechanical performance coupled with a dramatic increase in water barrier properties. In addition, transmission electron microscopy (TEM) analysis has been used to investigate the influence of ILs on the different morphologies of these sustainable polymer blends.