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

Abstract

The coupling of CO₂ 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-[FeCl₃Br] catalyst outperforming the homogeneous counterpart under mild conditions (25 °C, CO₂ 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 CO₂ valorization into cyclic carbamates, highlighting experimentally the combined effect of polystyrene supports and ammonium ferrate active species.