Bypassing the Inertness of Aziridine/CO2 Systems to Access 5‐Aryl‐2‐Oxazolidinones: Catalyst‐Free Synthesis Under Ambient Conditions

• Published in: ChemSusChem 2020-10, Vol.13 (20), p.5586-5594
• Main Authors: Bresciani, Giulio, Antico, Emanuele, Ciancaleoni, Gianluca, Zacchini, Stefano, Pampaloni, Guido, Marchetti, Fabio
• Format: Article
• Language: English
• Subjects: Ambient temperature; Aromatic compounds; aziridines; Carbon dioxide; carbon dioxide activation; catalyst free organic synthesis; Catalysts; Chemical synthesis; NMR spectroscopy; oxazolidinones; Reaction mechanisms; sustainability; Sustainable development
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202001823

The development of sustainable synthetic routes to access valuable oxazolidinones via CO2 fixation is an active research area, and the aziridine/carbon dioxide coupling has aroused a considerable interest. This reaction features a high activation barrier and thus requires a catalytic system, and may present some other critical issues. Here, the straightforward gram‐scale synthesis of a series of 5‐aryl‐2‐oxazolidinones was developed at ambient temperature and atmospheric CO2 pressure, in the absence of any catalyst/co‐catalyst. The key to this innovative procedure consists in the direct transfer of the pre‐formed amine/CO2 adduct (carbamate) to common aziridine precursors (dimethylsulfonium salts), replacing the classical sequential addition of amine (intermediate isolation of aziridine) and then CO2. The reaction mechanism was investigated by NMR spectroscopy and DFT calculations applied to model cases. In with the new: The largely investigated catalytic process affording 5‐aryl‐2‐oxazolidinones by the two‐step assembly of a C2 precursor with primary amine and carbon dioxide is replaced by the catalyst‐free, direct addition of the amine/CO2 adduct to the C2 unit in isopropanol or water.