Protic ionic liquids-promoted efficient synthesis of quinazolines from 2-aminobenzonitriles and CO2 at ambient conditions

- The catalyst can be prepared through a facile proton transfer from easily accessible materials.
- [HTMG][Im] renders a smooth-performing reaction at room temperature and atmospheric pressure.
- The catalyst can be recovered and reused efficiently.
- Bifunctional role of [HTMG][Im] is verified by NMR, in-situ FT-IR spectroscopy and DFT study.

Despite recent renaissance of CO2 chemistry, transformation of CO2 at ambient conditions remains still of great challenge. In this work, an easily prepared protic ionic liquid e.g. 1,1,3,3-tetramethylguanidinium imidazolide [HTMG][Im] was developed as highly efficient, recyclable and bifunctional catalyst for the carboxylative cyclization of 2-aminobenzonitriles with CO2 at atmospheric pressure and room temperature. The catalytic protocol was found to be applicable to various 2-aminobenzonitriles bearing electron-withdrawing or electron-donating substituents, affording the corresponding quinazoline-2,4(1H,3H)-diones in moderate to excellent yields. In addition, the catalyst could be conveniently recovered and reused for five cycles with almost consistent activity. Consequently, this process represents an alternative approach for the efficient and greener chemical fixation of CO2 to afford valuable heterocycles.

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