Bicyclic and Polycyclic 1,4-Dihydroxy Compounds

In the bicyclic series the Diels-Alder adduct of 2-acetyl-1,4-benzoquinone and 

By the reaction in tetrahydrofuran at 45°C over 12 hours of 3-ethynylphthalide and a pentacarbonyl chromium carbene complex of the cyclohexenone ketal depicted, followed by treatment of the product with ferric chloride-dimethylformamide (2 moles) a 74% yield of an anthracycline-type structure was obtained (ref.51). 

5-diacetoxydiphenyl with hexamethylenetetramine in acetonitrile by refluxing for 6 hours (under nitrogen) followed by solvent removal and hydrolysis for 1 hour in aqueous methanol containing concentrated hydrochloric acid, 4 -formyl-2,5-dihydroxybiphenyl was obtained in 61% yield (ref.52). 

5 -Trihydroxybiphenyls have been synthesised by coupling benzo-1,4-quinones with phenolates. Thus the dichloroaluminium salt of 4-tert-butylphenol (formed by reaction of the phenol in carbon disulphide with aluminium chloride) upon addition to the 2-methyl-benzo-1,4-quinone/ aluminium chloride (1 2) 

In the polycyclic field a number of anthraquinones with 1,4-dihydroxy groups have been synthesised by Diels-Alder reactions. 2-Chloronaphthazarin with the bis-trimethylsilyldieneshown,2,4-bis-trimethylsiloxy-3-alkoxycarbonylpenta-2,4-diene (R = Me, Et, i-Pr) affords the corresponding alkyl 

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