Studio di sistemi catalitici innovativi per la sintesi di prodotti della chimica fine

Abstract

The aim of this work of thesis was the synthesis, characterization and use of new catalytic species in different types of reactions, on both model substrates and in the preparation of some fine chemicals. These new catalytic species were then designed, prepared and characterized in collaboration with some Italian and foreign research laboratories. The new catalytic species obtained during this work of thesis are: a) heterogeneous catalysts (Pd-, Pt- and Rh-based) supported on alumina, characterized by very low contents of precious metal (from 0.18 up to 0.28%), easy preparation and high activity and selectivity; b) Pd and Rh nanostructured bio-generated catalysts, eventually in the co-presence of ferric oxide, embedded in a polysaccharidic matrix and active in aqueous or in organic solvent-water biphasic system. These new catalytic species were obtained, in collaboration with the microbiology laboratory of the DSMN of Ca' Foscari, by using a strain of Klebsiella oxytoca BAS-10 which is capable to produce a particular exopolysaccharide (EPS) able to bind metal nanoparticles if an appropriate metal salt is added during the stationary growth phase of the microorganism; c) Lewis acids heterogeneous catalysts obtained by a simple and innovative method by using a perfluorosulphonate ionomer (Aquivion®) d) a water-soluble and recyclable Rh based catalyst obtained by employing a cheap bis-thiol ligand; e) a biocatalyst able to selectively reduce carboxylic acids to the corresponding aldehydes. This biocatalyst was prepared by fermentation of an engineered microorganism and subsequently purified. This work was carried out during a three month stage in a biotechnological company in Scotland The main and most significant studied reactions in this project were: hydrogenation of carbon-carbon double bonds, reduction of some functional groups, hydrodehalogenation, carbonylation, hydroformylation, Friedel-Crafts alkylations and acylations and other acid-catalyzed reactions. The reactions were carried out both on model substrates and on molecules of industrial interest. The studied catalytic processes were employed to obtain some industrial products such as aldehydic and ketonic fragrances (HelionalTM and LioralTM, 5-isopropylthiophene-2-carbaldehyde, 2-propionyl-5-ethylthiophene, 3-phenylpropanal) , flavours (5-ethylthiophene-2-carbaldehyde), drugs and intermediates for drugs (Nabumetone®, m-chloroaniline), intermediates for agrochemicals (beta-keto-aryl esters) and intermediates for bulk chemicals such as cyclohexanone. The performances of these new catalytic species were compared to those of commercial catalysts and, very interestingly, in some cases, these new homemade catalysts showed higher activity and selectivity. Basing on the results obtained we can assert that the strategies developed during this research work appear suitable for a possible commercial development.