Antonino Rizzuti

New "Green" Approaches to the Synthesis of Pyrazole Derivatives

A novel approach to the synthesis of pyrazole derivatives from tosylhydrazones of alpha,beta-unsaturated carbonyl compounds possessing a beta-hydrogen is proposed, exploiting microwave (MW) activation coupled with solvent free reaction conditions. The cycloaddition was studied on three ketones (trans-4-phenyl-3-buten-2-one, beta-ionone and trans-chalcone). The corresponding 3,5-disubstituted-1H-pyrazoles were obtained in high yields and after short reaction times. In order to simplify and point out the green chemistry features of the method, a further improvement was achieved under the same catalytic conditions with a one pot synthesis of these heterocyclic compounds, starting directly from their carbonyl precursors via tosylhydrazones generated in situ. For an exhaustive study, the dielectric properties of the solid reaction mixtures were also measured, in order to obtain input data for the numerical simulation of their heating behaviour in the single mode MW cavity which was used for experimental work. In order to supply a valid methodology and tool for measuring the environmental impact, a comparative study between the synthetic route proposed and the classical synthetic route has been carried out.

Volcanic ash as alternative raw materials for traditional vitrified ceramic products

Abstract Investigation on the use of volcanic ash as 100% raw materials for traditional vitrified ceramic products is reported. X-ray diffraction (XRD), thermogravimetric–thermal differential analyses (DTA–TGA) and chemical analysis were used to characterise raw samples. Fired specimens were used to evaluate their ceramic properties. Volcanic ash contains essentially classical traditional ceramic oxides, plagioclase, pyroxene and olivine as principal minerals. In the temperature range 1100–1150°C, they present dense structure, low open porosity, without isolated quartz grains. The fired materials properties were found to be in agreement with those of stoneware class BI referring to standard ISO 13006 (i.e.the water absorption values were <1·5%). The presence of a sufficiently extended glassy phase capable of embedding crystalline phases developed during sintering allows comparison of the microstructure of fired volcanic ash with that of traditional porcelain or stoneware.

Microwave-Assisted Hydrothermal Synthesis as a Rapid Route Towards Manganite Preparation

In this work attempts to prepare strontium-doped lanthanum manganites La1-xSrxMnO3 using microwave-assisted hydrothermal synthesis were undertaken from a mixture of lanthanum nitrate, strontium nitrate, manganese(II) nitrate, potassium permanganate and potassium hydroxide as a mineralizer. For x = 0.3, and x = 0.5, the perovskite obtained is not defined since both La0.7Sr0.3MnO3 and La0.5Sr0.5MnO3 phases are consistent with XRD spectra. While with x = 1.0, for the first time, hexagonal strontium manganite was prepared as blade-shaped crystallites with a narrow particle length distribution (range 3.75-7.75 μm) at 210°C using a treatment time of only 1 hour. Conventional hydrothermal synthetic routes require at least 24 hrs treatment time.

Dehydration, Dehydroxylation, Densification and Deformation During Sintering of Geopolymers Based on the K 2 O-Al 2 O 3 -SiO 2 System

Based on the principle of stability of geopolymer gel as refractory binder, a geopolymeric paste in the K 2 O-Al 2 O 3 -SiO 2 system was developed and used to produce refractory concretes by adding various amount of α-quartz sand (grain size in the range 0.1μm-1mm) and fine powder alumina (grain size in the range 0.1-100 μm). The consolidated samples were characterized before and after sintering using optical dilatometer, DSC, XRD and SEM. The total shrinkage in the range of 25-900°C was less than 3%, reduced with respect to the most diffused potassium or sodium based systems, which generally records a >5% shrinkage. The maximum shrinkage of the base geopolymer was recorded at 1000°C with a 17% shrinkage which is reduced to 12% by alumina addition. The maximum densification temperature was shifted from 1000°C to 1150°C or 1200°C by adding 75xa0wt% α-quartz sand or fine powder alumina respectively. The sequences of sintering of geopolymer concretes could be resumed as dehydration, dehydroxylation, densification and finally plastic deformation due to liquid phase appearance. The geopolymer formulations developed in this study appeared as promising candidates for high temperature applications.

Catalytic activity and recyclability of polymer supported palladium or nickel nanoparticles in organic reactions in water

B is a clean, renewable and abundant resource that can be converted to bio-char, bio-oil and fuel gas through various thermochemical processes. Conversion of biomass for high value products is an important development direction for biomass utilization, which has attracted more attention. In this study, a new method of biomass pyrolysis with exogenous nitrogen introduced was proposed. The influence of NH3 on the property of bamboo pyrolysis process and products characteristics was investigated with variant approaches (e.g. elemental analysis, automatic adsorption equipment, X-ray photoelectron spectroscopy and CHI760 electrochemical workstation) and as well as the influence of KOH (as activator). The results showed that, the specific surface area, the content of nitrogen and nitrogen-containing functional groups of bio-char increased significantly with NH3 introduced in. On the other hand, with the addition of KOH, the yield of bio-char increased obviously and it increased gradually with increasing KOH amount, and the specific surface area increased dramatically to 1873.17 m2 g-1. The content of nitrogen in bio-char increased greatly with KOH introduced in, especially the content of pyridinic-N and pyrrolic/pyridone-N, while it decreased slightly with increasing KOH amount, but nitrogen content was still relative high (9.1-10.4 wt.%). The formation mechanism of nitrogen-containing functional groups was proposed. Besides, electrochemical analysis showed that the specific capacitance of bio-char electrodes increased with increasing KOH content, and the largest specific capacitance could reach to 187 F g-1 at 1 A g-1 with good cycling stability. Therefore, it could be concluded that biomass nitrogen-enriched pyrolysis was a promising method for more efficient utilization of biomass resources.A insoluble palladium catalyst (Pd-pol) was obtained by copolymerization of the metal containing monomer Pd(AAEMA)2 [AAEMA− = deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] with ethyl methacrylate (co-monomer) and ethylene glycol dimethacrylate (cross-linker), followed by in situ reduction of Pd(II) to Pd(0), to give polymer stabilized metal nanoparticles. The good swellability in water exhibited by Pd-pol rendered it an ideal potential catalyst for reactions carried out in a green solvent, such as water, since the migration of the reagents to the active sites would not be hampered by the solid support. With the aim to develop innovative catalytic processes that enable chemical transformations to be performed under mild and sustainable conditions with high efficiency, we decided to evaluate the catalytic activity of Pd-pol for several important organic reactions using water as solvent. Pd-pol resulted highly active and selective in catalyzing (figure 1): the Suzuki-Miyaura coupling between aryl bromides or activated aryl chlorides and phenylboronic acid; the oxidation of benzyl alcohols to aldehydes; the reduction of quinolines and nitroarenes by H2 or NaBH4. Pd-pol was recyclable for several consecutive runs (for example, at least 12 times in the nitroarene reduction). TEM analyses carried out on the catalyst showed that the active species were supported palladium nanoparticles having a mean size of 4 nm, which did not aggregate with the recycles. Recently, due to their low cost, Ni catalysts have been employed in several organic reactions (mainly hydrogenations). In this context, we synthetized a Ni catalyst similar to Pd-pol, starting from Ni(AAEMA)2 and we employed it as active and recyclable, insoluble catalyst for the reduction of different nitroarenes to give the corresponding anilines, under sustainable conditions. All these results proved that the proposed Pd or Ni based composite materials are excellent hybrid structures as efficient and reusable catalysts.A amino acids are versatile structures readily available by a number of methods and are accessible using very few transformations from economical starting materials. They can be functionalized by many chemical functions and offer a wide range of possible transformations. Particularly, unsaturated α-amino acids give access to many synthetic applications in all fields of chemistry. Among them, metal catalyzed cross-coupling reactions and cross metathesis are commonly used to generate peptide modifications and cyclization. They are very interesting and useful tools for “Click” Chemistry in peptidomimetic drug design or covalent modification of proteins. They can also be incorporated in compounds as beta-turn inducer to promote secondary structures. Finally they can be used for the preparation of stapled peptides. Some such amino acids are commercially attainable in enantiomerically pure form. Here, we present a stereoselective approach to synthesize unsaturated α-amino acids in optically active form. As a starting amino acid synthon for the asymmetric synthesis of amino acids NiII square-planar complexes of Schiff ’s bases of propargylglycine with chiral auxiliary (S)-2-N-(N`-benzyl-prolyl)aminobenzophenone (BPB) (1) was taken. As a result effective methods of asymmetric synthesis for novel enantiomerically enriched derivatives of (S)-propargylglycine (S)-propargylglycine (ee > 80%) was developed.