Carlo Pastore

Nb(V) compounds as epoxides carboxylation catalysts: the role of the solvent

The synthesis of organic cyclic carbonates from epoxides and CO2 is described. The role of the solvent is discussed, together with that of Nb(V) catalysts (Nb2O5 and NbCl5). The reaction is very selective and affords the conversion of epoxides into the relevant carbonates in high yield.

Enantioselective synthesis of organic carbonates promoted by Nb(IV) and Nb(V) catalysts

In this paper, we describe the use of Nb(IV) and Nb(V) catalysts in the carboxylation of either pure enantiomers of chiral epoxides or racemic mixtures. The carboxylation of pure enantiomers with Nb(V)-oxide is very selective (100%), proceeds with a good TON and occurs with total retention of the configuration. Optically active Nb(IV) complexes have been synthesised and used in the conversion of a racemic mixture of epoxides. An enantiomeric excess (ee, up to 22%) has been observed, that varies with the catalyst and the reaction conditions. The enantiomeric excess depends on the liability of the chiral ligands on Nb(IV).

Conversion of fructose into 5-HMF: a study on the behaviour of heterogeneous cerium-based catalysts and their stability in aqueous media under mild conditions

In this paper, we present the results of a study on 5-HMF production from fructose by means of heterogeneous catalysts in aqueous media. Mild conditions were used, setting the temperature between 393 K and 443 K. Cerium(IV) phosphates, different from other metal(IV)-phosphates, such as titanium and zirconium, have been characterized only recently. Ce-phosphates are quite complex structures as they show several arrangements. They undergo leaching of the phosphate group as phosphoric acid with consequent slow de-activation of the catalysts. The leaching rate depends on the nature and on the temperature of the calcination of the original phosphates. This opened the question whether the conversion was driven by the heterogeneous catalysts or by the soluble phosphoric acid. A specific test has demonstrated that the solid catalysts are responsible for the conversion of fructose into 5-HMF, more than the liquid phase. We have also demonstrated that the leached phosphate is substituted by fructose on the solid catalyst. A best yield of 52% with selectivity of 93% in batch and 24% in a flow reactor at 443 K (single pass) with a selectivity also >95% were obtained.

Synthesis and X-ray characterization of [RhCl(C2H4)(PiPr3)]2. Multinuclear NMR and DFT investigation of its solid-state and solution reaction with dihydrogen. Ethene and propene hydrogenation by the solid Rh-hydrides

[RhCl(C(2)H(4))(PiPr(3))](2) has been synthesised and structurally characterised. It shows an unusual planar Rh(2)Cl(2) system, with the two phosphine and the two ethene molecules disposed trans to each other. It easily reacts with dihydrogen in solution and in the solid state to afford ethane and a dimeric complex of formula [RhCl(H)(2)P](2). The latter exhibits a high fluxionality both in solution and in the solid state making impossible the identification of a single limiting structure even at 183 K. 25 different hydride structures are possible, four of which have very low interconversion barriers (1-3 kcal mol(-1)) and cannot be blocked even at 183 K. A multinuclear NMR study and HECTOR experiments have allowed to identify the most probable structures that interconvert at 198 K. The solid hydrides are able to hydrogenate quite selectively ethene and propene at room temperature. A TON higher than 5600 and a TOF of 97 h(-1) was observed with ethene (for propene the values were 5200 and 79, respectively). Toluene was hydrogenated to methylcyclohexane at 323 K under an atmospheric pressure of H(2) with a TOF h(-1) equal to 15.

Tunable Mixed Oxides: Efficient Agents for the Simultaneous Trans-Esterification of Lipids and Esterification of Free Fatty Acids from Bio-Oils for the Effective Production of Fames

In this paper we describe our approach to solving t he problem of the simultaneous trans -esterification of lipids (that require a basic catalyst) and esterifi cation of FFAs (that require an acid catalyst), usi ng mixed oxides ad hoc prepared. New mixed oxides based on calcium, cerium and aluminium have been used as catalysts in the reaction of trans -esterification of oils of different composition an d quality, namely: i) extra virgin olive oil as a test case (low acidity) and ii) non-edible oil (high acidity), such as tha t extracted from aquatic biomass ( Nannochloropsis sp microalgae). Among the several catalysts used, 12C aO 7Al 2O3 7CeO 2 has shown unprecedented properties in terms of act ivity and resistance in the simultaneous trans esterification/esterification.