1,2,4-三唑和1,2,4-三唑啉是有机合成中使用的生物活性分子和催化剂的重要组分。因此,这些组分的高效合成受到了广泛的研究关注。然而,对其结构多样性的研究仍然缺乏。以前,我们开发了手性相转移催化的α-亚氨基羰基化合物与α,β-不饱和羰基化合物和卤代烷烃。在这项研究中,我们证明了在布朗斯台德碱催化下α-亚氨基酯与偶氮化合物的形式[32]环加成反应,以高产率产生相应的1,2,4-三唑啉。结果表明,可以应用广泛的底物和反应物,不管它们的空间和电子特性。本反应首次使3-芳基五取代的1,2,4-三唑啉的一般制备成为可能。此外,一项机理研究表明,该反应在没有异构化成醛亚胺形式的情况下进行。
1,2,4-Triazole and 1,2,4-triazoline are important components of bioactive molecules and catalysts employed in organic synthesis. Therefore, the efficient synthesis of these components has received significant research attention. However, studies on their structural diversity remain lacking. Previously, we developed chiral phase-transfer-catalyzed asymmetric reactions of α-imino carbonyl compounds with α,β-unsaturated carbonyl compounds and haloalkanes. In this study, we demonstrate the formal [3 + 2] cycloaddition reaction of α-imino esters with azo compounds under Brønsted base catalysis, resulting in the corresponding 1,2,4-triazolines in high yields. The results revealed that a wide range of substrates and reactants can be applied, irrespective of their steric and electronic characteristics. The present reaction made the general preparation of 3-aryl pentasubstituted 1,2,4-triazolines possible for the first time. Furthermore, a mechanistic study suggested that the reaction proceeds without isomerization into the aldimine form.