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.

Abstract

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 °C, while a 30 : 70-45 : 55 exo/endo ratio was produced at room temperature. A large-scale reaction was also performed.