Amino Acids/Superbases as Eco-Friendly Catalyst System for the Synthesis of Cyclic Carbonates Under Metal-Free and Halide-Free Conditions

<p>An eco-friendly and efficient binary catalyst system of superbases and amino acids was developed for the synthesis of cyclic carbonates from epoxides and CO<sub>2</sub> under metal-free and halide-free conditions. Among the various amino acids and superbases systems tested, the <sub>L</sub>-histidine/DBU system achieved the highest conversion of propylene oxide and selectivity of propylene carbonate. The effect of various reaction parameters were evaluated. A possible catalyst mechanism for <sub>L</sub>-histidine synergized with DBU in the ring opening of epoxide and DBU introduced CO<sub>2</sub> activation. The process herein represents a green, simple and cost-effective route for the chemical fixation of CO<sub>2</sub> into cyclic carbonates.</p>