Imidazole hydrochloride as an additive promotes the reaction of amidoximes and DMA derivatives to generated 3,5-disubstituted-1,2,4-oxadiazoles in low to excellent yields without the use of coupling reagents, oxidants, strong acids or bases and other additives.
Formation and thermal reaction of O-(N-acetylbenzimidoyl)benzamidoxime: comparison with the formation of 3,5-disubstituted 1,2,4-oxadiazoles from O-acetylarylamidoximes and O-aroylacetamidoximes
作者:Ngan Sim Ooi、David A. Wilson
DOI:10.1039/p29800001792
日期:——
Acetylation of the free base gave the title compound, which underwent a thermalcyclisation, with loss of acetamide, to give 3,5-diphenyl-1,2,4-oxadiazole. The mechanism of this reaction, in diphenyl ether, closely paralleled the thermalcyclisation of O-acetylarylamidoximes and O-aroylacetamidoximes, and is thought to involve a polar cyclisation step followed by rate-determining proton transfer. 13C N.m.r.
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。
The reaction of amidoximes with carboxylic acids or their esters under high-pressure conditions
作者:S. V. Baikov、G. A. Stashina、E. I. Chernoburova、V. B. Krylov、I. V. Zavarzin、E. R. Kofanov
DOI:10.1007/s11172-019-2391-9
日期:2019.2
Abstract3,5-Disubstituted 1,2,4-oxadiazoles were synthesized by the reaction of amidoximes with carboxylic acids or their esters under high-pressure conditions (10 kbar). The reaction proceeds without the use of other reagents or catalysts. Both aliphatic and aromatic carboxylic acids undergo this reaction. The obtained 1,2,4-oxadiazoles possess high fungicidal activity.
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
The first one-pot ambient-temperature synthesis of 1,2,4-oxadiazoles from amidoximes and carboxylic acid esters
作者:Sergey Baykov、Tatyana Sharonova、Anton Shetnev、Sergey Rozhkov、Stanislav Kalinin、Alexey V. Smirnov
DOI:10.1016/j.tet.2017.01.007
日期:2017.2
The first one-pot room-temperature protocol for the synthesis of 3,5-disubstituted-1,2,4-oxadiazoles via the condensation between amidoximes and carboxylic acid esters in superbase medium MOH/DMSO is reported. A broad spectrum of alkyl, aryl and hetaryl amidoximes and esters was examined. This reaction route provides convenient access to 1,2,4-oxadiazoles, which is highly desirable because in the light