“…In particular, cyclopentynes, five-membered cyclic alkynes, are highly reactive and short-lived species. Hydrocarbyl cyclopentyne and thiacyclopentyne [4] have been prepared, and the formation was spectroscopically detected [5][6][7] or confirmed by trapping them by subsequent chemical reactions, such as 2 + 2 cycloaddition [8], metal complexation [9][10][11], and so on. However these compounds are so reactive that they have not been isolated in a pure form.…”