Other Pyridine-fused Thiophen-containing Systems

Other Pyridine-fused Thiophen-containing Systems.—A number of thieno-quinolines such as (557) and (558) have been prepared by applying the 

Skraup and Conrad-Limpach reactions to appropriate benzo[6]thiophen derivatives. Substitution reactions of thieno[3,2-/]quinoline (559), which was prepared by a Skraup synthesis from 5-aminobenzo[6]thiophen, have been studied. The same method has also been used earlier for the synthesis of the 7- and 9-methyl derivatives of (559). Nitration, bromina-tion, and acylation of (559) occur in the 2-position. Some reactions of 

The thio-Claisen rearrangement of propargyl 4-quinolyl sulphide (566) gives 2-methylthieno[3,2 c]quinoline (567) in high yield. By allowing (552) to react with hydrazine, followed by treatment with ethyl orthoformate, (568) was obtained, which upon treatment with base in ethylene 

---