Aromatic Hydroxylation and Deacylation of 9-Acylanthracenes by Copper(II)-peroxydisulfate

Article abstract of DOI:10.1021/jo00223a008

The Cu²⁺-S2O8^2- oxidations of 9-acylanthracenes (1) and 9-acyl-10-methylanthracenes (10) having formyl (a), acetyl (b), or benzoyl (c) groups were studied in refluxing acidic acetonitrile-water.Radical cations 1a-c, 10a, and 10c reacted with water to produce 10-hydroxyl adduct radicals which were oxidized by Cu²⁺ to produce the corresponding hydroxylated products: 10-acylanthrols (5) from 1 and 9-acyl-10-methyl-9,10-dihydroxy-9,10-dihydroanthracenes (15) from 10.Compounds 5 and 15 were unstable to reaction conditions and underwent subsequent reactions.Compound5 underwent tautomerization competitive with oxidation to respectively produce 10-acyl-9-anthrones (6) and 10-acyl-10-hydroxy-9-anthrones (8).Compounds 6 and 8 were hydrolytically unstable, yielding respectively anthrone and 9,10-dihydroxyanthracene, at rates dependent on acidity (6a, 6b, and 6c exhibited 2.6, 44. and 45 min half-lives, respectively, in 0.1 M HClO4).Compounds 15a and 15c solvolyzed in the acidic media to give 10-methylanthrol which was further oxidized to produce 10-methyl-10-hydroxy-9-anthrone (12).Partial dehydration of 12 produced 10-methylene-9-anthrone.Little product was formed by proton loss from the radical cations of 1a, 10a, and 10c.