Direct Synthesis of Benzoselenophene and Benzothiophene Derivatives from 1,1-Diarylethenes and Biaryls by Chalcogen Cation-Mediated Successive Bond Formation

A Tf2O-mediated sequential C-Se bond-forming reaction of 1,1-diarylethenes and biaryls with methaneselenic acid has been developed. Upon demethylation workup with ethanolamine, the corresponding benzoselenophene derivatives are obtained directly. The related synthesis of benzothiophene derivatives with sodium methanesulfinate is also possible with the unique assistance of the ball milling technique. The active species is considered to be a highly electrophilic chalcogen cation, which enables successive bond formation even at room temperature.