SYNTHESIS OF NITROGEN-CONTAINING COMPOUNDS VIA NITRENE-TRANSFER CATALYSED BY PORPHYRIN COMPLEXES

In this Ph.D. thesis several aspects around the topic of metal porphyrins-catalysed nitrene transfer reactions were investigated. It is worth to remark the importance of this sustainable synthetic methodology, it affords valuable nitrogen-containing compounds using cheap starting materials and, if organic azides are employed as nitrene source, molecular nitrogen is the only by-product of the reaction. The scope of ruthenium porphyrin-catalysed amination reaction was extended to the synthesis of important compounds from a biological and pharmaceutical point of view. New strategies to obtain amino acid derivatives and indoles by C-N bond formation were developed. In particular, the reported synthesis of the latter compounds was the first example of intermolecular reaction between an alkyne species and an organic azide affording the indole motif instead of triazoles; thus, it was demonstrated that a great control on the reaction selectivity can be achieved using metal porphyrin catalysts. The optimisation of these transformations was carried out also by studying the mechanism of the catalytic reaction. The generality of a previously performed mechanistic investigation concerning ruthenium porphyrin catalysed allylic amination was assessed. The point of view of Resonance Raman allowed the study of the catalytic system from a different perspective, whilst kinetic and theoretical studies shed some light into the mechanism of ruthenium-porphyrin catalysed aziridination of olefins and benzylic amination to give α- and β-aminoesters. The development of new catalysts to improve the catalytic performances and the process sustainability was also considered. Glycoporphyrin complexes, being potentially active compounds in promoting asymmetric synthesis or reactions in aqueous media, seem suitable for the accomplishment of this target. A preliminary study revealed the good catalytic activity in nitrene and carbene transfer reaction of this biocompatible substances, moreover the basis for a catalyst recovery/reuse system were laid.