Water-promoted selective cycloaddition of CO2 and aziridine in confined nanospaces of hierarchical porous silica: synergetic effect of chemical function and physical microenvironment

Abstract On the basis of a synergistic strategy for CO2 activiation and conversion, a water-promoted selective synthesis of 5-aryl-2-oxazolidinones from aziridines and CO2 has been exploited in a metal- and base-free system in confined nanospaces of hierarchical porous silica, affording moderate to good conversions and yields. In this process, carbonic acid in-situ generated interacts with and ingeniously activates the aziridine ring, facilitating its subsequent transformation and promoting the selectivity of 5-substituted products. DFT calculations, FTIR spectroscopy and pH value monitoring reveal that the excellent 5-postion regio-selectivity is dictated by kinetics, which is attributed to the formation of a latent benzyl carbocation in the transition state. The confined nanospaces of hierarchical porous silica can be considered as plenty of nanoreactors, which would change concentrations of reagents and activation parameters, stabilize transition states and enhance the kinetics process. This environment-friendly system provides a synergistic strategy of optimizing both the chemical function and physical microenvironment to enhance CO2 activation, and enriches the carbon capture and utilization (CCU) coupling process by conversion of the waste (water-fixed CO2) into value-added compounds.