Synthesis and some properties of 7H-naphth[3,2,1-cd]azulen-7-ones and related compounds

7H-Naphth[3,2,1-cd]azulen-7-ones are synthesized by the intramolecular Friedel–Crafts cyclization of diethyl 4-phenylazulene-1,3-dicarboxylate derivatives with polyphosphoric acid (PPA). Treatment of 7H-naphth[3,2,1-cd]azulen-7-one with methyl trifluoromethanesulfonate or perchloric acid gives 7-methoxynaphth[3,2,1-cd]azulenium trifluoromethanesulfonate or 7-hydroxynaphth[3,2,1-cd]azulenium perchlorate. Both spectroscopic inspection and molecular orbital calculations for 7-hydroxynaphth[3,2,1-cd]azulenium ion show that the tropylium moiety is a main contributor to the ground state in the resonance structure. The syntheses of 7H-azuleno[1,8-bc]phenanthren-7-ones and 5,7-dihydrodinaphth[3,2,1-cd:1′,2′,3′-ij]azulene-5,7-diones are also described.