通过N-氯-或N-溴-琥珀酰亚胺或卤素在苯甲酰胺肟上的作用,获得了O-(苯甲酰亚胺基)苯甲酰胺肟的盐。游离碱的乙酰化得到标题化合物,将其进行热环化,损失乙酰胺,得到3,5-二苯基-1,2,4-恶二唑。在二苯醚中,该反应的机理与O-乙酰基芳酰胺肟和O-芳酰基乙酰氨基肟的热环化非常相似,并且被认为涉及极性环化步骤,随后是速率确定质子转移。记录了32种肟,a胺肟和恶二唑衍生物的13 C Nmr光谱,并记录了肟,a胺肟的取代基化学位移,计算苯环上的O-乙酰基酰胺肟,5-甲基-1,2,4-恶二唑-3-基和3-甲基-1,2,4-恶二唑-5-基。
通过N-氯-或N-溴-琥珀酰亚胺或卤素在苯甲酰胺肟上的作用,获得了O-(苯甲酰亚胺基)苯甲酰胺肟的盐。游离碱的乙酰化得到标题化合物,将其进行热环化,损失乙酰胺,得到3,5-二苯基-1,2,4-恶二唑。在二苯醚中,该反应的机理与O-乙酰基芳酰胺肟和O-芳酰基乙酰氨基肟的热环化非常相似,并且被认为涉及极性环化步骤,随后是速率确定质子转移。记录了32种肟,a胺肟和恶二唑衍生物的13 C Nmr光谱,并记录了肟,a胺肟的取代基化学位移,计算苯环上的O-乙酰基酰胺肟,5-甲基-1,2,4-恶二唑-3-基和3-甲基-1,2,4-恶二唑-5-基。
Construction of 3,5-substituted 1,2,4-oxadiazole rings triggered by tetrabutylammonium hydroxide: a highly efficient and fluoride-free ring closure reaction of O-acylamidoximes
Tetrabutylammonium hydroxide (TBAH) is an efficient and mild alternative to tetrabutylammonium fluoride (TBAF) for base catalyzed cyclizations of 1,2,4-oxadiazoles from O-acylamidoximes. For most 3,5-substituted 1,2,4-oxadiazoles the reactions were dramatically accelerated by addition of 0.1 equiv of TBAH at room temperature. This method was also more generally applicable allowing for a wider range