Hide/Show Apps

Construction of a homonaphthazarin skeleton and synthesis of hydroquinone-annelated cycloheptatriene derivatives

Sengul, M. Emin
Menzek, Abdullah
Balcı, Metin
1,4-Dihydroxy-7,8-dihydro-5H-benzo[a]cycloheptene-5,9(6H)-dione (7) was synthesised from hydroquinone and glutaric acid chloride via an acylation reaction. The reaction of dione (7) with bromine followed by treatment with NEt3 gave homonaphthazarin 8 as well as the brominated derivatives 9 and 10. Reduction of 1,4-dimethoxy-7,8-dihydro-5H-benzo[a]cycloheptene-5,9(6H)-dione (16) with LiAlH4 gave 2 isomeric alcohols, 17 and 18. Reaction of these alcohols with SOCl2 followed by HCl elimination with NEt3 afforded dimethoxybenzocycloheptatriene 19 as the sole product. For the synthesis of the isomeric cycloheptatriene 20, the double bond in 19 was isomerised with KOt-Bu.