A practical synthesis of benzothiophenes via visible-light-promoted cyclization of disulfides and alkynes.

Visible-light-promoted intermolecular radical cyclization of disulfides and alkynes has been developed. Benzothiophenes bearing ester, ketone, aldehyde and aryl substituents were synthesized in good yields. The reaction was carried out in the absence of transition-metal catalysts and extra additives. Oxygen was used as the sole oxidant. In addition, the irradiation of sunlight could also promote the reaction efficiently.