Rearrangement of 3,3-Disubstituted 1-Aryl-4,5-dihydro-5-oxo-3<i>H</i>-1,2,4-triazolium Tetrafluoroborates; Part 2. A Convenient Synthesis of 1,5-Annulated 1,2-Dihydro-2-phenyl-3<i>H</i>-1,2,4-triazol-3-ones
作者:Hubert Gstach、Patrick Seil
DOI:10.1055/s-1990-27022
日期:——
1-Isocyanato-1-(phenylazo)cycloalkanes 3 react with tetrafluoroboric acid to yield 3-spiro substituted 4,5-dihydro-5-oxo-1-phenyl-3H-1,2,4-triazolium tetrafluoroborates 4. Compounds 4 rearrange with ring expansion in good yield to give, after basic workup, 1,5-annulated 1,2-dihydro-2-phenyl-3H-1,2, 4-triazol-3-ones 5.
A nickel-promoted cascadeannulation reaction for the facile synthesis of 3H-1,2,4-triazol-3-ones from readily available hydrazonoyl chlorides and sodium cyanate has been developed. The transformation occurs through a cascade nickel-promoted intermolecular nucleophilic addition–elimination process, intramolecular nucleophilic addition, and a hydrogen-transfer sequence. The method has been successfully
已经开发了镍促进的级联环化反应,用于从容易获得的酰肼基氯和氰酸钠容易地合成3 H -1,2,4-三唑-3-酮。通过级联镍促进的分子间亲核加成-消除过程,分子内亲核加成和氢转移序列进行转化。该方法已成功应用于血管紧张素II拮抗剂的核心骨架的构建。