Synthesis and properties of cyclohepta[cd]benzothiophenes

Cyclohepta[cd]benzothiophene 3, a new heterocyle, was synthesized starting from benzothiophene via eight steps in 14% total yield. Chemical reactions of 3 were examined on formylation, acetylation, bromination, catalytic hydrogenation and Diels‐Alder reactions. The results show that the benzothiophene moiety of 3 has aromatic character and the carboncarbon double bonds in a seven‐membered ring posseses alkene‐1ike character.