Highly Recyclable Fluoride for Enhanced Cascade Hydrosilylation-Cyclization of Levulinates to γ-Valerolactone at Low Temperatures

A facile and benign catalytic route has been developed to quantitatively yield gamma-valerolactone (GVL; ca. 97%) from biomass-based levulinates at room temperature to 80 degrees C by using easily available polymethylhydrosiloxane (PMHS) and KF as the liquid H-donor and recyclable catalyst, respectively. No extra step was required to liberate GVL from the in situ-formed siloxane, and this catalytic system exhibited a lower activation energy (40.9 kJ/mol) compared to previously reported ones. The deuterium-labeled study further demonstrated the reaction proceeding through cascade hydrosilylation and cyclization with fluoride successively acting as the nucleophile and base. In addition, the PMHS-derived resin was extremely favorable to restrain the leaching of fluoride and maintain its constant activity for at least six cycles.