2,4-Diaryl-1,3-Chalcogen Azoles Bearing Pentafluorosulfanyl SF₅ Groups: A Synthetic and Structural Study

A series of new 2,4-diaryl-1,3-chalcogen azoles having pentafluorosulfanyl SF₅ functional groups has been prepared by means of the two-component cyclization of the selenoamide or thioamide with alpha-bromoketones. The selenoamides or thioamides were obtained from the reaction of Woollins' reagent or Lawesson's reagent with 4-pentafluorosulfanylbenzonitrile, followed by hydrolysis with water. All new compounds were characterised by H-1, C-13, Se-77, F-19 NMR spectroscopy and accurate mass measurement. X-ray crystal structure analysis of the selenoamide, thioamide and 2,4-diarylpentafluorosulfanyl-1,3-chalcogen azoles reveal that the selenoamide and thioamide have very similar structural features along with similar intermolecular interactions such as the pi-pi stacking and the weak N-H center dot center dot center dot E (E = S or Se) hydrogen bonding. The 2,4-diarylpentafluorosulfanyl-1,3-chalcogen azoles show the newly formed five-membered N(1)-C(2)-E(3)-C(4)-C(5) ring is either perfectly planar (and coplanar with two peripheral aryl ring planes) or near-planar. The pi-pi intermolecular interactions and the weak C-H center dot center dot center dot pi and C-H center dot center dot center dot X (X = Br, F, O) hydrogen bonding are discussed in the cases of 2,4-diarylpentafluorosulfanyl-1,3-chalcogen azoles.