Valorization of agricultural waste and CO2 into bioderived cyclic carbonates

Abstract

Highly efficient and metal-free bifunctional organocatalysts have been used for the synthesis of waste vegetable oils-derived cyclic carbonates from bio-derived epoxides and CO2. In this contribution, epoxides 2a-k and carbon dioxide have been used as renewable feedstocks for the synthesis of cyclic carbonates 5a-k in excellent isolated yields (85–97%) using the highly efficient and metal-free bifunctional imidazole-based organocatalyst 4b under solvent-free conditions. The preparation of cyclic carbonates 5a-g, in which oleic acid is the major component, has been performed at 100 °C and 20 bar CO2 pressure for 16 h using 1 mol% of catalyst 4b. In addition, cyclic carbonates 5h-k have been synthesized at 80 ºC and 20 bar CO2 pressure for 16 h using different catalyst loading of 4b (2 mol% for 5h-j and 3 mol% for 5k). Finally, a reusability study of organocatalyst 4b was performed under the optimized reaction conditions keeping constant the catalytic activity and stability of 4b for at least 5 days.