Amine-tethered DMAP Cation Catalysts: An Efficient Organocatalytic System for the Chemical Fixation of CO2 to Five-Membered Cyclic

Introduction: In this study, three amine-tethered DMAP cation bromide catalysts were prepared using two different mole ratios of 4-dimethylpyridine (DMAP) and 3-bromopropylamine hydrobromide (BPA·HBr) in two different solvents, namely, acetonitrile and ethanol. Then, prepared catalysts were employed for CO2 cycloaddition with styrene and propylene epoxides under metal- and solvent-free conditions. Method: The impact of mole ratio and solvent selection to prepare the designed product using a simple and cost-effective procedure was demonstrated systematically and was discussed in detail. Moreover, the influence of amine-tethered DMAP cation catalyst structures and reaction conditions on the cycloaddition was investigated, and the CO2 conversion proceeded smoothly at 80°C and 0.2 MPa for the synthesis of cyclic carbonates in good to excellent yields and high selectivity. Results: The current protocol could be a promising process at an industrial scale due to the high recyclability of the catalyst (10 cycles). Conclusion: In summary, three catalytic systems bearing amine-tethered DMAP cation have been investigated for the chemical fixation of CO2 into five-membered cyclic carbonates at mild conditions.