Efficient Synthesis of Quinazoline-2,4(1<i>H</i>,3<i>H</i>)-dione via Simultaneous Activated CO<sub>2</sub> and 2-Aminobenzonitrile by 1-Methylhydantoin Anion-Functionalized Ionic Liquid through the Multiple-Site Cooperative Interactions
Tingting Chen, Yunfei Zhang, Yingjie Xu
Abstract
A novel basic anion-functionalized ionic liquid with a 1-methylhydantoin anion ([1-MHy]−) and [P4442]+ cation was synthesized for efficient CO2 capture and catalytic conversion of CO2 to quinazoline-2,4(1H,3H)-dione, and CO2 absorption and conversion mechanisms were investigated by NMR, FT-IR, and DFT calculations. CO2 absorption results show that the capture capacity of [P4442][1-MHy] at 303.15 K and 0.1 MPa is up to 1.58 molCO2/molIL, which is attributed to the multiple-site cooperative interactions between CO2 with N– and C═O of [1-MHy]− originated from the electron conjugation effect, resulting in a decrease in the CO2 absorption enthalpy (−51.4 kJ/mol) and an increase in the activation of CO2. Moreover, the high yield of quinazoline-2,4(1H,3H)-dione obtained by using [P4442][1-MHy] to catalyze 2-aminobenzonitrile with atmospheric-pressure CO2 was 97% and is solvent- and metal-free. The reaction mechanism indicates that [1-MHy]− with the multiple-site cooperative interactions can not only activate CO2 but also can activate 2-aminobenzonitrile by forming two types of hydrogen bonds with −NH2 (N–H···N– and N–H···O═C), thus ensuring the excellent catalytic performance of [P4442][1-MHy]. Furthermore, due to the similar basicity of [1-MHy]− to the quinazolide anion ([Quinazolide]−), it can effectively prevent the deprotonation of the acidic quinazoline-2,4-dione into [Quinazolide]−, thereby improving its yield. In addition, [P4442][1-MHy] has good recycling performance during CO2 capture and conversion. The physicochemical properties of [P4442][1-MHy] are also reported. The obtained results may provide a new strategy for converting CO2 into value-added chemicals under green conditions.