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

The development of sustainable synthetic routes to access valuable oxazolidinones via CO2 fixation is
currently a hot topic of research, and the aziridine/carbon dioxide coupling has aroused a particular
interest. This reaction is featured by a high activation barrier, thus it requires a catalytic system and
often presents some other critical issues. Here, we describe the first gram-scale synthesis of a large
number of 5-aryl-2-oxazolidinones at ambient temperature and atmospheric CO2 pressure, in the
absence of any catalyst/co-catalyst and using water as solvent. The key to this innovative procedure
consists in the direct transfer of the CO2/amine 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 has been elucidated by NMR studies and DFT
calculations applied to model cases.