Protonated Porphyrins: Bifunctional Catalysts for the Metal-Free Synthesis of N-Alkyl-Oxazolidinones

The protonation of commercially available porphyrin ligands yields a class of bifunctional catalysts able to promote the synthesis of N-alkyl oxazolidinones by the CO2cycloaddition to corresponding aziridines. The catalytic system does not require the presence of any Lewis baseor additive and shows interesting features both in terms of cost-effectiveness and eco-compatibility. The metal-freemethodology is active by using the low catalytic loading of 1% mol and the chemical stability of the protonated porphyrin allowed its recycle for three consecutive times without any decrease of performances. In addition, a DFT study was performed in orderto suggest how a simple protonated porphyrin can mediate the CO2cycloaddition to aziridines yielding oxazolidinones.