Additive‐Free Synthesis of Cyclic Carbamates From Aziridines and CO₂ Catalyzed by IER Supported Iron(III) Halides

The coupling of CO 2 with aziridines offers an efficient, 100% atom‐economic route to synthesize high‐value cyclic carbamates. In this study, we present a heterogeneous catalytic system based on readily available iron(III) metallates supported on commercially available ion‐exchange resins (IERs) for the selective synthesis of 1,3‐oxazolidin‐2‐ones. Two polystyrene‐based IERs with different porosities, Amberlyst™ 26‐Cl (A26‐Cl, macroreticular) and Amberlite™ IRA‐400‐Cl (IRA400‐Cl, microporous) were evaluated. The results reveal a synergistic interaction between the iron metallate and the resin support, with the A26‐[FeCl 3 Br] catalyst outperforming the homogeneous counterpart under mild conditions (25 °C, CO 2 pressure = 0.8 MPa, 2 h), achieving up to >99% yield of the target oxazolidinone. A Design of Experiments (DoE) approach was applied to optimize reaction parameters, and the system's versatility was confirmed using aziridines with different substitution patterns. Overall, this work presents a scalable (up to 1 g) and cost‐effective method for CO 2 valorization into cyclic carbamates, highlighting experimentally the combined effect of polystyrene supports and ammonium ferrate active species.