Direct Diels-Alder Reaction of Biomass-Derived Furfurol with Maleimides in a Bio-Based Green Solvent

Environmental concern has motivated an inclination to exploit waste and upgrade it into high-added-value chemicals. Biomass is an excellent carbon source that provides a variety of raw materials as building blocks, such as furans. Herein, we report the upcycling of furfurol, a known biomass by-product, through a Diels-Alder cycloaddition with maleimides that is performed in a green bio-derived solvent, 2-MeTHF. We provide two alternative sets of reaction conditions to promote exo or endo selectivity, which depends on the temperature employed. A variety of products were obtained in 70-96 % yield and high exo selectivity at 80 degrees C, while a 30 : 70-45 : 55 exo/endo ratio was produced at room temperature. A large-scale reaction was also performed. The upconversion of biomass-derived furfurol through a direct Diels-Alder reaction with maleimides in 2-Me-THF enabled the construction of various heterocyclic compounds, while switching the reaction selectivity depending on the temperature. image