CO2 is an important C1 resource. We report a method for the synthesis of pharmacologically active 2-oxazolidinones by reacting CO2 with allylic amines. As opposed to previous addition reactions, the unsaturated double bonds are preserved. Thus, the product is more plastic and easier to use for subsequent structural modification. Furthermore, this method can also be applied to the synthesis of six-membered heterocycles (1,3-oxazinan-2-ones) and the participation of a low concentration of CO2, indicating it has certain practicability.