Tandem Catalysis for the Direct Synthesis of Cyclic Organic Carbonates from Olefins and CO₂

Driven by the multitude of environmental, economic and social challenges that humanity and our planet have faced to this day, the concept of promoting a sustainable mindset with particular attention to the principles of Green Chemistry has gained increasing importance in both academic and industrial contexts over the years. The use of a non-toxic, renewable and abundant reagent such as CO₂ as a building block for chemical reactions represents an approach perfectly aligned with the idea of sustainability. Among the products obtainable from CO₂ are cyclic organic carbonates (COCs), which are particularly versatile compounds that can be used as solvents, electrolytes for batteries, monomers for polymers and more. The most widely investigated reaction for the synthesis of COCs is the CO₂ insertion into epoxides, which can be obtained via the oxidation of olefins. This Thesis studies a tandem catalytic process for the one-pot synthesis of propylene carbonate (PC) from propylene without the need to isolate the epoxide intermediate, which is highly toxic. Several tungsten- and molybdenum-based catalysts were synthesized, characterized and their catalytic activity was studied for both steps of the tandem process. Moreover, the investigation included a parametric analysis based on a selected catalytic species for each of the two separate reactions, along with oxidant and substrate scopes. A gram-scale process for the CO₂ insertion into propylene oxide (PO) was also performed. Finally, the tandem process was tested on various substrates beyond propylene to explore the general reactivity of the system.