1‐(5‐(Hydroxymethyl)furan‐2‐yl)‐5‐methylhex‐1‐en‐3‐one was prepared from cellulose or glucose by a sequence of depolymerization/dehydration/aldol condensation reactions. The synthesis of HMF was first performed starting from a highly concentrated feed of glucose and cellulose (31 wt.%) using choline chloride in MIBK/water biphasic media via the formation of a glucoside intermediate. Next, the aldol condensation of HMF with MIBK was investigated over alkaline metal oxides. Among the catalysts used, commercial BaO was highly efficient with a yield of aldol product above 90 %. Under air, BaO instantaneously transformed into Ba(OH)2, H2O and BaO2 which are regarded as active phases for the reaction. The catalyst basicity and solvent were key parameters to govern the selectivity of the reaction by limiting secondary reactions.