Synthesis of 4-Selanyl- and 4-Tellanyl-1<i>H</i>-isochromen-1-ones Promoted by Diorganyl Dichalcogenides and Oxone
Helen A. Goulart, José S. S. Neto, Angelita M. Barcellos, Krigor B. Silva, Maiara C. Moraes, Raquel G. Jacob, Eder J. Lenardão, Thiago Barcellos, Gelson Perin
Abstract
A new method was developed for the synthesis of 4-chalcogenyl-1H-isochromen-1-ones through the 6-endo-dig 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 in situ. 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 5H-selenopheno[3,2-c]isochromen-5-ones. Additionally, for the first time, the 4-chalcogenyl-1H-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.