Radical cyclization of alkynyl aryl ketones for the synthesis of 3-seleno-substituted thiochromones and chromones.

We report a strategy for the direct synthesis of 3-organylselanylthiochromones and 3-organylselanylchromones the radical cyclization reaction between alkynyl aryl ketones containing an -thiopropyl/methoxy group and diorganyl diselenides promoted by Oxone®. This method allows the construction and -functionalization of thiochromones and chromones using Oxone® as a stable and non-hazardous oxidizing agent in the presence of CHCN at 82 °C. These reactions tolerate a variety of substituents, and allowed the synthesis of twenty-one new 3-organylselanylthiochromones and selanylchromones in good to excellent yields (55-95%).

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.

Synthesis of 4-Selanyl- and 4-Tellanyl-1-isochromen-1-ones Promoted by Diorganyl Dichalcogenides and Oxone.

A new method was developed for the synthesis of 4-chalcogenyl-1-isochromen-1-ones through the 6-- electrophilic cyclization of 2-alkynylaryl esters and diorganyl dichalcogenides under ultrasound irradiation. The reactions were performed under mild conditions, using Oxone as a green oxidant to promote the cleavage of the chalcogen-chalcogen bond in diorganyl diselenides and ditellurides to generate electrophilic species . A total of 25 compounds were selectively obtained after 30-70 min, in good to excellent yields (74-95%).