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%). This procedure was extended to prepare 5-selenopheno[3,2-]isochromen-5-ones. Additionally, for the first time, the 4-chalcogenyl-1-isochromen-1-ones were used as substrates in the thionation reaction, using Lawesson's reagent and microwave irradiation under solvent-free conditions, obtaining the thio derivatives in yields of up to 99% in only 15 min.