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
Ra. Mekheimer, 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, SYNTHESIS-S, (14), 2000, pp. 2078-2084
An easy and efficient synthesis of the versatile, hitherto unreported methy
l 3-amino-4-chloro-1-ethyl-pyrrolo[3,2-c]quinoline-2-carboxylate (9) is des
cribed. 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, re
spectively. Refluxing 9 with an excess of morpholine (15a) in boiling ethan
ol yields the corresponding pyrrolo[3,2-c]quinolines 16a which react with i
sothiocyanates 13a,c to afford the new 5,7,9,11-tetraazabenzo[a]fluorenes 1
7a,b. Refluxing 9 with an excess of butylamine affords the corresponding in
termediate 16b, which reacts with ethyl chloroformate and triethyl orthofor
mate to furnish the novel 1,3,5,6-tetraazaaceanthrylenes 18 and 19, respect
ively. 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 obtaind.