- Wednesday, July 29, 1992
- The Synthesis of Novel Polycyclic Heterocyclic Ring Systems via Photocyclization.10 .Synthesis and Structure Determination of Naphtho[1',2':4,5]thieno[3,2-a]-4,7-phenanthroline
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As a part of an extension of our synthetic work on photoinduced cyclization reactions[la-i] we now wish to report the synthesis of another hitherto unknown heterocvclic ring system namely naphtho[1',2':4,5]thieno[3,2-a]-4,7phenanthroline (6).
The reaction of 1-chloronaphtho[2,1-b]thiophene-2carbonyl chloride (1)  with 6-aminoquinoline(2)provided1-chloro-N-(quinolin-6-yl)naphtho[2,1-b]ihiophene-2carboxamide (3) in 85% yield. Photocyclization of 3 afforded naphtho[l',2':4,a"]thieno[3,2-a]-4,7-phenanthrolin8(7H)-one (4) in 29% Yield. Lactam 4 was chlorinated in refluxing phosphorus oxvchloride to give 8-chloronaphtho[l',2':4,5]thieno[3,2-a]-4,7-phenanthroline (5) in 40% yield. Catalytic dechlorination of compound 5 was accomplished with 10% Pd/C in a solution of potassium hydroxide, methanol, and benzene under a hydrogen atmosphere to yield naphtho[1',2':4,5]thieno,[3,2-a]-4,7-phPnanthroline (6) in 63% yield.