involved. In the first case the effect of X is meagre and 3-acetylamino-5-aryl-1,2,4-oxadiazoles are more stable than the 3-aroylamino-5-methyl isomers. Vice-versa, when anions are involved the substituent effect is remarcable and the equilibrium can be, for strongly electron-withdrawing X-groups, even largely shifted towards the anions of the 3-aroylamino-5-methyl-1,2,4-oxadiazoles.
通过1 H NMR测量,已经在CD 3 OD和t BuOK / CD 3 OD中研究了标题反应。已经发现,无论涉及中性或阴离子形式,平衡组成和芳基部分中X-取代基对其施加的作用都完全不同。在第一种情况下,X的作用微不足道,3-乙酰
氨基-5-芳基-
1,2,4-恶二唑比3-芳酰基
氨基-5-甲基异构体更稳定。反之亦然,当涉及阴离子时,取代基的作用是可区分的,并且对于强烈吸电子的X-基团,其平衡甚至可能朝着3-aroylamino-5-methyl-1,2,4-的阴离子转移。恶二唑。