treated with an excess amount of olefins at 130°C, the addition of a vinyl radical, which was generated in situ by the denitrogenation of 1,2,3-selenadiazoles, to a carbon–carbon double bond followed by intramolecular cyclization proceeded efficiently giving the corresponding dihydroselenophenenes in moderate to good yields along with the formation of the corresponding 1,4-diselenins and selenophenes