Halogen-free fixation of carbon dioxide into cyclic carbonates via bifunctional organocatalysts

Abstract

Bifunctional organocatalysts bearing diamine and carboxylic acid groups were used for the preparation of cyclic carbonates by cycloaddition reactions of CO₂ and epoxides. Hydrogen-bonding interactions originating from carboxylic acids are of enormous importance due to their contribution in enabling the opening of the epoxide ring. In addition, the diamine can activate the CO₂via carbamate formation and accelerate its transformation to cyclic carbonates. As a result of this synergy, this metal-free system shows excellent catalytic activities with high yields (92–99%) and selectivities (99%), and thus, provides a promising halogen-free and green pathway for the synthesis of cyclic carbonates from CO₂ and epoxides.