Hemisquaramide Tweezers as Organocatalysts: Synthesis of Cyclic Carbonates from Epoxides and CO2

Hemisquaramide tweezers, a new family of H-bond donor organocatalysts, are reported. The catalysts could be synthesized within two steps. Among them, H-8-binaphthyl-linked hemisquaramide 7 markedly accelerated the synthesis of cyclic carbonates from epoxides and CO2. The reactions proceeded well under mild and solvent-free conditions. Kinetic resolution was also achieved at -20 degrees C (s = 3.0). The adjustable bite angle and orientation of the two NH groups of the catalysts are important for the high activity.