Acetylene derivatives of 1,2,4-oxadiazoles, i.e., 5-(2-arylethynyl)-3-aryl-1,2,4-oxadiazoles, have been obtained, for the first time reported, from 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles by their bromination at the carbon–carbon double bond followed by di-dehydrobromination with NaNH₂ in liquid NH₃. The reaction of the acetylenyl-1,2,4-oxadiazoles with arenes in neat triflic acid TfOH (CF₃SO₃H) at room temperature for 1 h resulted in the formation of E/Z-5-(2,2-diarylethenyl)-3-aryl-1,2,4-oxadiazoles as products of regioselective hydroarylation of the acetylene bond. The addition of TfOH to the acetylene bond of these oxadiazoles quantitatively resulted in E/Z-vinyl triflates. The reactions of the cationic intermediates have been studied by DFT calculations and the reaction mechanisms are discussed.

中文翻译：

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5-芳基乙炔基-1,2,4-恶二唑的合成及其在超亲电活化条件下的转化

1,2,4-恶二唑的乙炔衍生物，即 5-(2-芳基乙炔基)-3-芳基-1,2,4-恶二唑，已首次报道，从 5-(2-芳基乙炔基) )-3-芳基-1,2,4-恶二唑通过在碳-碳双键处溴化，然后在液态NH _{3 中}与NaNH ₂进行二脱溴化氢。乙炔基-1,2,4-恶二唑与芳烃在纯三氟甲磺酸 TfOH (CF ₃ SO ₃ H) 中在室温下反应 1 小时导致形成E / Z -5-(2,2-二芳基乙烯基)-3-芳基-1,2,4-恶二唑作为乙炔键区域选择性加氢芳基化的产物。将 TfOH 添加到这些恶二唑的乙炔键上可定量地产生E/ Z-乙烯基三氟甲磺酸酯。通过DFT计算研究了阳离子中间体的反应，并讨论了反应机理。