Synthesis of Eugenol-Derived Dicyclic Carbonates toward Sustainable Non-Isocyanate Polyurethanes

Introduction The growing environmental and health concerns associated with conventional polyurethane production have accelerated the development of sustainable non-isocyanate polyurethanes (NIPUs). Traditional polyurethane synthesis relies heavily on petrochemical feedstocks and toxic isocyanates, which pose significant ecological and toxicological risks. Bio based cyclic carbonates have emerged as promising precursors for greener polyurethane systems. Among renewable resources, eugenol, a naturally occurring phenolic compound derived from clove oil and lignin, represents an attractive platform molecule due to its reactive allylic functionality and renewable origin.
Methods In this study, eugenol-derived dicyclic carbonates were synthesized through a sequential three-step pathway. First, eugenol-based dienes were prepared via allylation reactions using allyl bromide. Subsequently, the obtained dienes were epoxidized in situ using dimethyldioxirane (DMDO), generated from acetone and Oxone®. Different solvents and surfactant-assisted microemulsion systems were evaluated to optimize epoxidation efficiency. Finally, the resulting diepoxides underwent cycloaddition with carbon dioxide in the presence of phosphonium-based catalysts to produce the targeted dicyclic carbonates. Structural characterization of intermediates and final products was performed using proton nuclear magnetic resonance (¹H NMR) spectroscopy.
Results The proposed synthetic strategy successfully generated eugenol-derived diepoxides and dicyclic carbonates with high selectivity. NMR analyses confirmed the formation of epoxide and cyclic carbonate functionalities. Optimization of solvent conditions and surfactant ratios significantly improved epoxidation performance and product homogeneity. The cycloaddition reaction with CO₂ efficiently yielded bio-based dicyclic carbonates suitable for further NIPU synthesis.
Conclusions This work demonstrates an effective and sustainable route for producing bio-based dicyclic carbonates from renewable eugenol feedstocks. The developed methodology provides a promising platform for the future fabrication of environmentally friendly non-isocyanate polyurethanes with potential applications in coatings, adhesives, and advanced polymer materials.