Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.
Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Göttingen, Germany.
Angew Chem Int Ed Engl. 2017 Aug 21;56(35):10559-10563. doi: 10.1002/anie.201705438. Epub 2017 Jul 26.
Ionic liquids (ILs) are versatile solvents and catalysts for the synthesis of quinazoline-2,4-dione from 2-aminobenzonitrile and CO . 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 pK of the IL anion (conjugate acid) and the reaction rate was identified with maximum catalyst efficiency observed at a pK 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 pK 14.7). Neutralization of the original catalyst and formation of the quinazolide anion catalyst leads to the observed reaction limit.
离子液体 (ILs) 是一种多功能溶剂和催化剂，可用于从 2-氨基苯甲腈和 CO 合成喹唑啉-2,4-二酮。然而，IL 在该反应中的作用还不太清楚。因此，我们研究了该反应，并表明 IL 阳离子在激活底物方面没有起到重要作用，而是在控制 IL 的物理性质方面起到次要作用。我们发现 IL 阴离子 (共轭酸) 的 pK 与反应速率之间存在线性关系，在 DMSO 中 pK >14.7 时观察到最大的催化剂效率。该碱催化反应受到喹唑啉-2,4-二酮产物酸度的限制，该产物被更碱性的催化剂去质子化，形成喹唑啉阴离子 (共轭酸 pK 14.7)。原始催化剂的中和和喹唑啉阴离子催化剂的形成导致观察到的反应限制。
