Developing a strategy to synthesize an unprecedented and previously unknown organic molecule is especially appealing. The design, synthesis, and development of a new class of spiro-cyclic carbonates are reported. An efficient process involving the cycloaddition reaction of spiro-epoxyoxindoles with CO₂ (balloon) has been demonstrated using deep eutectic solvent (DES). The reaction can be carried out under mild reaction conditions to afford desired spiro-cyclic carbonates in excellent yields (up to 98%). The product could be separated easily, and the DES was reusable four times with retention of its activity.