Construction of a Homonaphthazarin Skeleton and Synthesis of Hydroquinone-annelated Cycloheptatriene Derivatives

摘要

1,4-Dihydroxy-7,8-dihydro-5H-benzo[a]cycloheptene-5,9(6H)-dione(7)was synthesised from hydro-quinone and glutaric acid chloride via an acylation reaction.The reaction of dione(7)with bromine followed by treatment with NEt_3 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 LiAlH_4 gave 2 isomeric alcohols,17 and 18.Reaction of these alcohols with SOCl_2 followed by HCl elimination with NEt_3 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.