The CO2 cycloaddition to epoxides and aziridines promoted by porphyrin-based catalysts

Abstract

Thanks to its intrinsic eco–compatibility and high atom economy, the direct insertion of CO2 into three–membered rings, such as epoxides and aziridines, has become one of the most investigated strategies for the synthesis of cyclic carbonates and oxazolidin-2-ones. In this view, the following short account summarizes our recent results regarding the use of ruthenium porphyrin complexes and metal-free porphyrins, in combination with TBACl (tetrabutyl ammonium chloride), to promote the CO2 conversion into cyclic carbonates as well as N–alkyl and N-aryl oxazolidin-2-ones. Experimental data are described in combination with performed DFT studies that allowed proposing a reaction mechanism for the CO2 cycloaddition to aziridines promoted by metal-free porphyrins in which the adduct formed by TPPH2 and TBACl represents the real catalytic active species.