Upgrading of Biobased Lactones with Dialkylcarbonates

Four renewable lactones, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone (GBL, GVL, DVL, ECL, respectively) were shown to react with dimethyl-, diethyl-, and dibenzyl-carbonate (DMC, DEC, DBnC, respectively) in the presence of K2CO3 as basic catalyst, to yield selectively either the α-alkyl derivatives 1c–6c in the case of the five-membered ring GBL and GVL or the highly oxygenated acyclic monomeric derivatives 7a, 8a, and 9a in the case of the six- and seven-membered rings DVL and ECL. Selectivity and reaction conditions are investigated and a reaction mechanism is proposed. The organic carbonates act both as reagent and as reaction solvents, and the catalyst can be recovered by filtration and recycled.