Acetylene derivatives of 1,2,4-oxadiazoles, 5-(2-arylethynyl)-3-aryl-1,2,4-oxadiazoles, have been obtained, for the first time, 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. Reaction of the acetylene 1,2,4-oxadiazoles with arenes in neat triflic acid TfOH (CF3SO3H) at room temperature for 1 h result 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. Addition of TfOH to acetylene bond of these oxadiazoles gives rise quantitatively to E-/Z-vinyl triflates. Reaction cationic intermediates have been studied by DFT calculations. The reaction mechanisms have been discussed.
Keywords: acetylene oxadiazoles, hydroarylation, Friedel-Crafts reaction, superelectrophilic activation, triflic acid
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Puzanov, A. I.; Ryabukhin, D. S.; Zalivatskaya, A. S.; Zakusilo, D. N.; Mikson, D. S.; Boyarskaya, I. A.; Vasilyev, A. Beilstein Arch. 2021, 202149. doi:10.3762/bxiv.2021.49.v1
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