Abstract
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•An efficient catalyst for the regioselective cycloaddition of CO2 to unreactive N-tosyl aziridines has been developed.•Halogen free and readily available Nb(OEt)5 has been identified as the most active Lewis acidic catalyst.•Systematic DFT calculations support the observed catalytic activity and regioselectivity of the catalyst.
An efficient and facile approach to the regioselective synthesis of N-tosyloxazolidinones from the corresponding N-tosylaziridines and CO2 was developed using dual catalytic systems involving an early transition metal coordination compound as a Lewis acid and a nucleophilic cocatalyst. Among the screened Lewis acids, halogen-free niobium pentaethoxide (Nb(OEt)5) displayed the best catalytic activity when used in the presence of tetrabutylammonium iodide (TBAI). Systematic DFT calculations, supported by catalytic experiments, demonstrate that CO2 insertion is the rate determining step for this process and it is highly dependent on the steric hindrance at the niobium center.