THE SYNTHESIS OF 2-HYDROXY-3H-CYCLOHEPT[a]AZULEN-3-ONE (AZULENO[2,1-d]TROPOLONE) AND ITS METHYL ETHERS

Abstract
2-Hydroxy-3H-cyclohept[a]azulen-3-one (azuleno[2,1-d]tropolone) (2) was synthesized, starting from 1,2-diformylazulene (3). Methylation of 2 yielded two kinds of methyl ethers (4 and 6), differing from benzotropolones. In trifluoroacetic or dil. sulfuric acid, 2, 4 and 6 exist in cyclohept[a]azulenylium ions (2a, 4a and 6a).

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