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) [3] 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.