EXPERIMENTAL AND THEORETICAL STUDIES TO DEVELOP SUSTAINABLE METHODS IN HOMOGENEOUS GOLD(I) AND GOLD(III) CATALYSIS

Green processes have become an import topic for Chemistry in the last decade. Gold has been proved to play an important role to replace hazardous material thanks to its non-toxicity and biocompatibility. In this thesis, gold(I) complexes were employed in homogeneous catalysis for the transformations involving the activation of carbon‐carbon π-systems. Great results in term of catalytic activity (TON and TOF) and green parameters (E-factor and EMY) were achieved in the hydration of alkynes in neat conditions using NBu4OTf as the only additive. Volatile organic solvents were replaced with success by green solvents in the Meyer-Schuster rearrangement of 1-phenyl-2-propyn-1-ol and in the cyclization of propargylamide, reaching also better performances. These two studies were corroborated also by computational mechanistic investigations, unraveling the unexpected formation of a gold-oxetene intermediate for the Meyer-Schuster reaction. Unlike gold(I), gold(III)-catalyzed reactions are still in their infancy and the vast majority of reports describe the use of inorganic salts. As done for Au(I), the development of knowledge on Au(III) catalysis and stoichiometric reactions is mandatory. Based on our studies about the hydration of alkynes catlyzed by L-Au-X complexes, a [AuIII-(ppy)-IPr]2+ catalyst was engineered to promote this kind of reaction, while maintaining its stability. Structure, reactivity and catalytic properties have been addressed in this thesis by means of multinuclear solution NMR and computational (DFT) studies, with an important focus for the preequilibrium step. NMR spectroscopy combined with DFT calculation has proved successful for the comprehension of reaction mechanisms and to better understand the chemical structure of the catalytic species, thus allowing the development of sustainable homogeneous gold catalysis.