One-flow syntheses of diverse heterocyclic furan chemicals directly from fructose via tandem transformation platform

Abstract

The sustainable green chemistry associated with lignocellulosic biomass is of current interest for producing various chemical feedstocks via multi-step transformation processes. Here we introduce a chemical platform system for the multicomponent cascade transformation of natural lignocellulosic biomass resources. We demonstrate the concept by developing an integrated continuous two-step microfluidic system as a tandem transformation platform for direct conversion of fructose to diverse furan chemicals with excellent yields up to 99% via decarbonylation, etherification, oxidation and hydrogenolysis of a 5-hydroxymethylfurfural (HMF) intermediate. A sequential two-step process is utilized to complete the dehydration of fructose in the surface acid catalyst at 150 °C for 6 min, which is followed by the four types of HMF conversion in a binary or ternary phase to produce furfuryl alcohol (94% yield), 5-ethoxymethylfurfural (99%), 2,5-diformylfuran (82%) and 2,5-dimethylfuran (90%) with magnetic-based heterogeneous catalysts at 70–150 °C for 6–60 min. This innovative tandem microfluidic platform enables precise control of the reaction temperature and time for each individual biomass conversion step in a one-flow manner with no separation and purification steps for intermediates and catalysts. An innovative microfluidic platform can directly convert fructose biomass into valuable feedstocks. Dong-Pyo Kim's team from Pohang University of Science and Technology in Korea have developed a direct transformation device that pushes liquid solutions of sugars derived from waste cellulose through two sets of narrow tubes known as capillary microreactors. The first microreactor is loaded with sulfonic acid catalysts that dehydrate fructose molecules into smaller ring complexes called hydroxymethylfurfurals with complete conversion and 99% selectivity. The second stage features a clever system of external magnets that position iron-oxide-supported catalysts inside the microreactor to further transform the hydroxymethylfurfural into versatile furan chemicals widely used as synthetic building blocks. The team attributes the remarkable efficiency of their synthetic process to the one-flow design that eliminates the need for separation and purification steps. We report a tandem transformation platform for one-flow syntheses of diverse heterocyclic furan chemicals.