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

An eco-friendly and efficient binary catalyst system of superbases and amino acids was developed for the synthesis of cyclic carbonates from epoxides and CO₂ under metal-free and halide-free conditions. Among the various amino acids and superbases systems tested, the _L-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 _L-histidine synergized with DBU in the ring opening of epoxide and DBU introduced CO₂ activation. The process herein represents a green, simple and cost-effective route for the chemical fixation of CO₂ into cyclic carbonates.