Synthesis of Chalcogenophenes via Cyclization of 1,3‐Diynes Promoted by Iron(III) Chloride and Dialkyl Dichalcogenides

In this paper, we report the iron(III) chloride and dibutyl diselenide‐mediated cyclization of 1,3‐diynes which leads to 3,4‐bis(butylselanyl)selenophenes. The optimization studies showed that the reaction was best performed with equimolar amounts of iron(III) chloride and dibutyl diselenide in dichloromethane at 40 °C for 4 h. The method allows the synthesis of symmetrical and unsymmetrical selenophenes in moderate to good yields. A similar protocol was also extended to the synthesis of thiophene derivatives using dimethyl disulfide instead of dibutyl diselenide. The resulting selenophenes and thiophenes were further functionalized by selenium–halogen exchange reactions, Sonogashira cross‐coupling reactions and electrophilic cyclizations.