Cyclization of 2‐ and 3‐indolythioalkanoic acids to novel indole‐containing tricyclic ring systems

A series of 2‐ and 3‐indolylthioalkanoic acids of various chain lengths were cyclized under dehydrative conditions affording tricyclic indole‐containing ring systems wherein the third ring contains a sulfur atom attached to the 2‐ or 3‐position of the indole ring. This methodology affords entry into the novel thiepino[3,2‐ b ]indole, thiocino[2,3 ‐b ]indole and thiocino[3,2‐ b ]indole ring systems.