On the synthesis of a phenanthrene-2,7-quinone
Abstract
Oxidative coupling of 2,2′,4,4′-tetramethoxystilbene-3,3′-diol 51 gave a 51% yield of 1,3, 6,8-tetramethoxyphenanthrene-2,7-quinone 52, the first isolated example of a quinone of this type. Similar oxidation of the corresponding diphenylethane 55 gave the 9,10-dihydrophenanthrene-2,7-quinone 56. Attempts to synthesize the tetramethoxyphenanthrene-2, 7-diol 25 from a 2, 2′bis(hydroxymethyl)hexamethoxybiphenyl precursor 28 were thwarted by the ease of intramolecular cyclization to 2,3, 4,8,9,10-hexamethoxydibenz[c,e]oxepine 32. Selective demethylation of the 3-and 9-methoxy groups of this compound, and oxidation of the resulting diol 58 gave the dibenzoxepine quinone 59.
The synthesis of 3,6-di-tert-butylphenanthrene-2, 7-diol 3 is also described, but this could not be oxidized to the quinone. However, the preparation of 3,6-di-tert-butyl-9,10-dihydrophenanthrene2,7-quinone 12 was successful.