一锅法合成苯并噁唑类化合物

A one-pot synthetic route to substituted benzoxazoles

以三氯氧磷(POCl_3)为缩合剂,将邻氨基苯酚和羧酸在CHCl_3中回流一锅法合成4个系列的2-烷基、2-芳基、2-苯乙烯基取代的苯并噁唑类化合物,并研究其可能的反应历程;通过考察反应过程中邻氨基苯酚和羧酸以及POCl_3的物质的量比、羧酸的结构及活性、反应温度以及溶剂种类对目标化合物产率的影响,得到最佳的反应条件参数,并对目标化合物进行1HNMR和MS表征。研究结果表明:邻氨基苯酚和羧酸以及POCl_3的物质的量比、羧酸的结构及活性对苯并噁唑的产率影响比较大;当温度达到或超过60℃时,所选的溶剂对其产率的影响比较小;2-烷基取代苯并噁唑的产率整体比2-芳基和2-苯乙烯基取代的苯并噁唑产率高;该方法是一种简便、高效的合成2-取代苯并噁唑类化合物的方法。

Aliphatic acids, aromatic acids and β-aryl-α,β-unsaturated acids were selected to react with o-aminophenol in the presence of phosphorus oxytrichloride（POCl3） in refluxing CHCl3 to afford four series of 2-alkyl,2-aryl and 2-styryl benzoxazoles,respectively, and a possible reaction mechanism for their synthesis was proposed. The reaction conditions including the molar ratio of substrates and POCl3, the structure and activity of carboxylic acid, the reaction temperature and the different solvents were optimized. All the structures of the target products were confirmed by 1HNMR and MS.The results show that the molar ratio of substrates and the different carboxylic acid structures play an important role in the yields of benzoxazoles. The impact of the selected solvent on yield is relatively small when the reaction temperature equals or surpasses 60 ℃. The yields of 2-alkyl substituted benzoxazoles are significantly higher than those of 2-phenyl and 2-styryl substituted benzoxazoles. The method is concise and efficient for the synthesis of 2-substituted benzoxazoles.