Synthesis of novel 5 H , 11 H ‐pyrido[2′,3′:2,3]thiopyrano[4,3‐ b ]‐indoles by fischer‐indole cyclization

The synthesis of the title compounds 5 H , 11 H ‐pyrido[2′,3′:2,3]thiopyrano[4,3‐ b ]indoles was accomplished by the Fischer indole cyclization of some 2,3‐dihydrothiopyrano[2,3‐ b ]pyridin‐4(4 H )‐one phenylhydrazones and 7‐methyl‐2,3‐dihydrothiopyrano[2,3‐ b ]pyridin‐4(4 H )‐one phenylhydrazones. The synthesis of the new 2,3‐dihydrothiopyrano[2,3‐ b ]pyridin‐4(4 H )‐one, which was used as one of the starting compounds, is also described.