Metal-free n-Et4NBr-catalyzed radical cyclization of disulfides and alkynes leading to benzothiophenes under mild conditions

A novel n-Et4NBr-catalyzed method for the synthesis of benzothiophene derivatives via cascade reactions of substituted disulfides with alkynes through S-S bond cleavage and alkenyl radical cyclization reactions has been developed. The reaction has a high functional-group tolerance. The new method is environmental and practical, and the starting materials are readily available. These advantages, relative to previous methods, provide an opportunity for the construction of diverse and useful benzothiophene motifs.