UVA Light‐promoted Catalyst‐free Cyclization of Vinyl Selenides: Green and Efficient Synthesis of C3‐Unsubstituted 2‐Selanyl Benzochalcogenophenes.

A metal‐ and catalyst‐free photo‐promoted cyclization of properly substituted vinyl selenides was developed using UVA irradiation. A total of eighteen new C3‐unsubstituted 2‐selanyl benzochalcogenophenes (benzofurans, benzothiophenes and benzoselenophenes) were prepared in 30–86% yield after irradiation with UVA at room temperature. The usefulness of the title compounds was demonstrated in the easy functionalization of the remaining free C−H bond of the benzochalcogenophenes to form new C−Se and C−Br bonds by simple procedures. Furthermore, the reaction can be performed under natural sunlight irradiation and the solvent is easily reused further in several subsequent runs. [ABSTRACT FROM AUTHOR]