Innovative and sustainable strategies in asymmetric synthesis and waste recycling: towards a circular economy model

The research activity carried out during my PhD aimed to develop novel processes embracing a greener and more sustainable perspective, by following the 12 Principles of Green Chemistry. This work explored Switchable Solvents (SS), Polydiacetylenes (PDA), and stereoselective cycloadditions, and among these diverse areas of research, a common theme and guideline has been a focus on sustainability and the pursuit of simplification. For Switchable Solvents, I investigated their use as alternative, smart media for organocatalytic reactions, enabling catalyst recycling and reuse. Various asymmetric reactions catalyzed by aminocatalysts were tested, yielding promising results in terms of both efficiency and stereoselectivity. While the solvent was successfully recycled, catalyst recovery was partial but holds potential for improvement. SS were also applied to multilayered packaging waste, enabling the delamination and separation of aluminum and polymeric layers that were efficiently recovered with preserved properties. Regarding PDA, I explored the use of these innovative materials to develop recyclable heterogeneous organocatalysts. Their self-assembly and polymerization properties were exploited to create a robust and manageable supported organocatalyst which was tested in aldol reactions with good results and recyclability. Finally, during my visiting period in professor Jørgensen’s group, I cooperated in the development of two projects. The first concerned the synthesis of heterotropones derivatives, easily obtained through a nucleophilic aromatic substitution on triflated tropolone employing different nucleophiles. The reactivity of these new compounds in [4+2] cycloaddition reactions with dienophiles was also studied and efficiently demonstrated. The second project was targeted to the development of Brønsted-base catalysed (3+2) annulations between donor-acceptor cyclopropanes and nitrosoarenes, accessing chiral substituted isoxazolidines. High conversion and enantiomeric excesses were achieved, allowing for the extension to different substrates, with a broad scope and excellent results.