Thiophene-Fused π-Systems from Diarylacetylenes and Elemental Sulfur

A simple yet effective method for the formation of thiophene-fused pi-systems is reported. When arylethynyl-substituted polycyclic arenes were heated in DMF in the presence of elemental sulfur, the corresponding thiophene-fused polycyclic arenes were obtained via cleavage of the ortho-CH bond. Thus, arylethynylated naphthalenes, fluoranthenes, pyrenes, corannulenes, chrysenes, and benzo[c]naphtho-[2,1-p]chrysenes were effectively converted into the corresponding thiophene-fused pi-systems. Apart from polycyclic hydrocarbons, thiophene derivatives are also susceptible to this reaction. The practical utility of this reaction is demonstrated by preparations on the decagram scale, one-pot two-step reaction sequences, and multiple thiophene annulations.