Delineating the Mechanism of Ionic Liquids in the Synthesis of Quinazoline‐2, 4(1H, 3H)‐dione from 2‐Aminobenzonitrile and CO2. Issue 35 (26th July 2017)

• Record Type: Journal Article
• Authors: Hulla, Martin; Chamam, Sami M. A.; Laurenczy, Gabor; Das, Shoubhik; Dyson, Paul J.
• Is Part Of: Angewandte Chemie international edition. Volume 56:Issue 35(2017)
• Page Start: 10559
• Page End: 10563
• Publication Date: 2017-07-26
• Subjects: base catalysis -- carbon dioxide -- ionic liquids -- organocatalysis -- sustainable chemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201705438
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Ionic liquids (ILs) are versatile solvents and catalysts for the synthesis of quinazoline‐2, 4‐dione from 2‐aminobenzonitrile and CO2 . However, the role of the IL in this reaction is poorly understood. Consequently, we investigated this reaction and showed that the IL cation does not play a significant role in the activation of the substrates, and instead plays a secondary role in controlling the physical properties of the IL. A linear relationship between the p K a of the IL anion (conjugate acid) and the reaction rate was identified with maximum catalyst efficiency observed at a p K a of >14.7 in DMSO. The base‐catalyzed reaction is limited by the acidity of the quinazoline‐2, 4‐dione product, which is deprotonated by more basic catalysts, leading to the formation of the quinazolide anion (conjugate acid p K a 14.7). Neutralization of the original catalyst and formation of the quinazolide anion catalyst leads to the observed reaction limit. Abstract : The ionic liquid (IL) cation does not play a significant role in the activation of the substrates in the synthesis of quinazoline‐2, 4‐dione from 2‐aminobenzonitrile and CO2 . Instead, it plays a secondary role in controlling the physical properties of the IL. A linear relationship between the p K a of the IL anion (conjugate acid) and the reaction rate was identified, with maximum catalyst efficiency observed at a p K a of >14.7 in DMSO.