Synthesis of Biobased Diethyl Terephthalate via Diels–Alder Addition of Ethylene to 2,5-Furandicarboxylic Acid Diethyl Ester: An Alternative Route to 100% Biobased Poly(ethylene terephthalate)

Poly­(ethylene terephthalate) (PET) is a ubiquitous thermoplastic currently produced from nonrenewable fossil resources; as such, sustainable biobased routes to the key terephthalate monomer are being widely pursued. Herein is demonstrated a greener solventless route to biobased diethyl terephthalate via a one-pot heterogeneous Lewis acid catalyzed Diels–Alder addition and dehydration of 2,5-furandicarboxylic acid diethyl ester with ethylene, giving yields of terephthalate up to 59% for the key Diels–Alder addition step. A metrics-based comparison against alternative published biobased routes (available from sugars, cellulose and hemicellulose) shows that the clean synthetic pathway developed herein gives a practical atom economy, overall yield and selectivity, making it a viable alternative to routes currently under development.