A convergent synthesis of 1,3,4-oxadiazoles from acyl hydrazides under semiaqueous conditions
作者:Kazuyuki Tokumaru、Jeffrey N. Johnston
DOI:10.1039/c7sc00195a
日期:——
aromatic heterocycle valued for its low-lipophilicity in drug development. Substituents at the 2- and/or 5-positions can modulate the heterocycle's electronic and hydrogen bond-accepting capability, while exploiting its use as a carbonyl bioisostere. A new approach to 1,3,4-oxadiazoles is described wherein α-bromo nitroalkanes are coupled to acyl hydrazides to deliver the 2,5-disubstituted oxadiazole directly
1,3,4-恶二唑是一种芳香杂环,因其低亲脂性而在药物开发中具有重要价值。2-和/或5-位的取代基可以调节杂环的电子和氢键接受能力,同时利用其作为羰基生物等排体的用途。描述了一种制备 1,3,4-恶二唑的新方法,其中 α-溴硝基烷烃与酰肼偶联以直接提供 2,5-二取代恶二唑,避免了 1,2-二酰肼中间体。通过利用手性 α-溴硝基烷或氨基酸酰肼底物,可以改善恶二唑取代仲胺新结构单元的获得。与依赖高亲氧性试剂来实现不对称 1,2-二酰肼环化的替代方案相比,恶二唑合成的非脱水条件尤其值得注意。通过标准水洗直接去除副产物,打破了温和的条件。