Synthesis and reactivity of new transition metal-based catalytic systems in carbonylation reactions

Abstract The aim of this PhD thesis was to explore the activity of new catalytic systems in some carbonylation reactions of organic substrates, like aromatic amines, olefins and/or iodoarenes which are transformed in isocyanates, ureas, esters, amides and polymers, interesting for the chemical industry. In Chapter 1 the study of the synthesis of isocyanates and amides of industrial interest is reported. A catalytic system based on [PdCl2(dppf)]/FeCl3/O2 was studied for the synthesis of phenylisocyanate and N,N diphenylurea (DPU), by oxidative carbonylation of aniline. Also presented is a study of synthesis of cyclohexanoneoxime obtained by reduction of nitrobenzene in the presence of NH2OH.HCl with heterogeneous Pd catalysts, which by Beckmann rearrangement can lead to the formation of Caprolactam. A reactivity study of trifluoroacetate hydroxylamine (NH2OH.CF3COOH) for the synthesis of oximes and amides of industrial interest is also presented. In Chapter 2, a study on the carbonylation of olefins with Pd-based heterogeneous pre-catalysts is presented. Through the study of methoxycarbonylation of cyclohexene these catalysts were compared to the activity of the homogeneous catalyst of [Pd(TsO)2(PPh3)2]. From a study of the reaction mechanism, the possibility of having a mixed homogeneous/heterogeneous catalysis is proposed. In addition, a study of a new heterogeneous magnetic support obtained by decomposition of Fe(CO)5 is presented, which was suitably coated with a polyketone layer. Such a support was employed for the synthesis of a Pd-based heterogeneous catalyst (Pd/MIM) and successfully employed in methoxycarbonylation reaction of cyclohexene, methoxycarbonylation of iodobenzene and for nitrobenzene reduction reaction. In conclusion, the hydration of olefins catalyzed by CF3COOH, which is commonly employed as an acidic promoter in palladium-catalyzed carbonylation reactions, was investigated to delineate possible eddy reactions for olefin carbonylation reactions for industrially employed two-phase systems. In Chapter 3, a study was performed on the carbonylation of iodobenzenes. A new catalytic system based on [PdCl2(Xantphos)] was studied for alkoxycarbonylation reactions. In particular, the effects of some additives on the productivity of the reaction have been studied, defining as the best catalytic system the one formed by [PdCl2(Xantphos)] and the pair Ferrocene/ferrocenium. In addition, a preliminary study of the amino-carbonylation reaction of iodobenzene is presented, the selectivity of the reaction is explored, and the possible competition of the base required for the catalytic cycle and the amine employed as a nucleophile. In Chapter 4, the possibility of employing green surrogates for carbonylation reactions was investigated. A study was carried out on the generation of CO from formic acid, through the Morgan reaction, using heterogeneous acid catalysts. The best setup of the reactor has been studied to optimize the yield of carbon monoxide and avoid the mechanical degradation of acid resins used as catalysts. A new multi-chamber reactor has also been designed to perform simultaneously several Palladium-catalyzed carbonylation reactions, employing CO generated by formic acid. Finally, the first example of polymer obtained by catalytic carbonylation of ethylene (PK), employing CO generated by formic acid and acetic anhydride system, is presented. The HCOOH/CH3COO2 mixture plays both the role of solvent and carbon monoxide generator.