Synthesis of Bis-1,3,4-Oxadiazoles Utilizing Monomers Derived from the Degradation of PET (Polyethylene Terephthalate) in an Eco-Friendly Manner

The chemical recycling process of polyethylene terephthalate (PET) was executed through aminolysis employing N,N-Diisopropylethylamine (DIPEA) as the catalytic agent, commencing with the systematic collection and comprehensive purification of discarded PET bottles to remove contaminants and additives. The depolymerization reaction utilized hydrazine as the primary amine source, facilitating the cleavage of ester bonds within the polymer matrix under controlled temperature and pressure conditions. The synthesis of the diamine compound, terephthalohydrazide, was successfully achieved through this catalytic aminolysis pathway, demonstrating high conversion efficiency and product selectivity.

The resulting terephthalohydrazide served as a crucial intermediate and was subsequently utilized for the further synthesis of BIS-1,3,4-Oxadiazole derivatives through a comprehensive methodology rigorously aligned with the fundamental principles of green chemistry, including atom economy, reduced waste generation, and environmentally benign reaction conditions. A diverse series of six distinct products derived from various carboxylic acids employed in the cyclization synthesis of BIS-1,3,4-Oxadiazoles were systematically produced under optimized reaction parameters. These products were meticulously characterized using advanced nuclear magnetic resonance (NMR) spectroscopy techniques, including both ¹H and ¹³C NMR analyses, confirming their structural integrity and chemical composition. This sequential approach represents a significant advancement in heterocyclic synthesis methodology , using sustainable pathway to find structural diversity.