水／有机两相体系中杂多酸催化氧化芳香腈反应研究

Study on oxidation of aryl nitriles to amides catalyzed by heteropolyacids in aqueous/organic biphasic system

考察了以杂多酸为催化剂,廉价、清洁、易得的氧气为氧化剂催化氧化腈生成酰胺的反应。实验结果表明,以氧气为氧化剂,杂多酸为催化剂的体系具有较高的活性和良好的选择性;磷钼酸较其它杂多酸有更佳的催化性能;底物芳环上带吸电子基时能加快反应速率,而腈基邻位基团的空间位阻引起反应速率下降。在优化的反应条件下,苯甲腈氧化反应的转化率和选择性分别达到了88%和99%,并且产品与催化剂易于分离,便于操作。

Oxidation of aryl nitriles catalyed by heteropolyacide is investigated with oxygen gas as an oxidant. The results show that H7 [PMo12O42 ]·xH2O is the most efficient catalyst among the investigated heteropolyacids. The increase of oxygen pressure obviously improves the catalytic performance. The oxidation of the substrate containing an electron - withdrawing group is more easy than that containing an electron - donating group. Due to steric factors, a substituent in the ortho - position of nitrile group decreases dramatically the reaction activity of the substrate. Under optimum conditions, the conversion and seleetivity of oxidation of benzonitrile to benzamide are up to 81.0% and 99.0%, respectively. At the end of reaction, the separation of the catalyst from product is easy.