Robinson Annulation-Directed Synthesis of Jet-Fuel-Ranged Alkylcyclohexanes from Biomass-Derived Chemicals

Robinson annulation may be useful for converting biomass-derived compounds into jet-fuel-ranged alkylcyclohexanes, but it has not been fully developed until now. Herein, a strategy for the synthesis of highly branched C15 alkylcyclohexanes with lignocellulose-derived furfural and 2,4-pentanedione was developed with Robinson annulation as the key step. Low-freezing-point (−81 °C) and high-density (0.8139 g/mL) highly branched alkylcyclohexanes were produced by two steps, namely, a one-pot cyclization process including the aldol condensation of furfural with 2,4-pentanedione and the subsequent Robinson annulation of the aldol adducts with 2,4-pentanedione over CoCl2·6H2O catalyst, then following with the Pd/NbOPO4-catalyzed hydrodeoxygenation.