Upcycling of Polystyrene to 1,2-Disubstituted Oxygenated Aromatics Through Backbone Rearrangement and Oxidation...

Upcycling polystyrene (PS) into economically-viable, industrially-relevant single-, and multi-substituted oxygenated aromatic compounds is an attractive option to address the current unsustainable end-of-life of this high-volume waste plastic. However, 1,2-disubstituted oxygenated aromatics (e.g., phthalic anhydride), possessing a multi-billion dollar annual market, have thus far been inaccessible from PS. This is due to unsurmountable steric constraints conferred by the polymer backbone hindering ortho-functionalization of its pendant phenyl groups. Herein, to overcome this challenge, we report a strategy to convert PS directly into 1,2-disubstituted aromatics, first by PS backbone rearrangement into polyindanes, followed by organocatalyzed aerobic oxidations. Our approach is applicable to mixed real-life PS waste on multi-gram scales, allowing convenient access to ortho-substituted aromatics used as catalysts, dyes, and drug precursors with different structural complexities previously inaccessible from PS. Furthermore, this versatile strategy was also applicable on PS-like polymers such as poly(4-methylstyrene), producing trimellitic, terephthalic, and isophthalic acids. This approach significantly expands the range of high-value substituted aromatic products accessible from PS, further enhancing its utility as a feedstock in a circular economy.