I. Takeuchi et al., SYNTHESES OF NAPHTHONAPHTHYRIDINES BY SKRAUP REACTION USING 3-AMINOBENZO[G OR H]QUINOLINE, Chemical and Pharmaceutical Bulletin, 41(4), 1993, pp. 747-751
Naphtho[2,1-f][1,7]naphthyridine (5, angular type) and naphtho[2,1-b][
1,5]naphthyridine (6, linear type) were obtained by the Skraup reactio
n of 3-aminobenzo[h]quinoline (4), but 3-aminobenzo[g]quinoline gave o
nly naphtho-[2,3-f][1,7]naphthyridine (18, angular type).