Subscribe to RSS
Fused Quinoline Heterocycles III: Synthesis of First Annulated 1,4,5,6,6a-Pentaazabenzo[a]indacenes, 1,3,5,6-tetraazaaceanthrylenes and 5,7,9,11-Tetraazabenzo[a]fluorenes
31 December 2000 (online)
An easy and efficient synthesis of the versatile, hitherto unreported methyl 3-amino-4-chloro-1-ethyl-pyrrolo[3,2-c]quinoline-2-carboxylate (9) is described. Reaction of 9 with sodium azide gives the corresponding tetracyclic ring system 10 in near quantitative yield. With isothiocyanates 13a,b the corresponding new 1,3,5,6-tetraazaaceanthrylenes 14a and 14b are formed, respectively. Refluxing 9 with an excess of morpholine (15a) in boiling ethanol yields the corresponding pyrrolo[3,2-c]quinolines 16a which react with isothiocyanates 13a,c to afford the new 5,7,9,11-tetraazabenzo[a]fluorenes 17a,b. Refluxing 9 with an excess of butylamine affords the corresponding intermediate 16b, which reacts with ethyl chloroformate and triethyl orthoformate to furnish the novel 1,3,5,6-tetraazaaceanthrylenes 18 and 19, respectively. On the other hand, reacting 16b with acetic anhydride does not give the expected tetracyclic compound 20, but instead, the interesting pyrrolo[3,2-c]-quinolines 21 is obtained.
1,4,5,6,6a-pentaazabenzo[a]indacenes - 1,3,5,6-tetraazaaceanthrylenes - 5,7,9,11-tetraazabenzo[a]fluorenes - cyclizations - heterocycles - sodium azide