Synthesis of 4, 5-Dihydroxy-l, 3, 6, 8-tetramethylphenanthrene
Bromination of 4, 6-dimethyl-3-hydroxybenzoic acid (4) yielded exclusively 2-bromo-4, 6-dimethyl-3-hydroxybenzoic acid (5), which was methylated to yield methyl 2-bromo-4,6-dimethyl-3-methoxybenzoate (6). Ullman coupling of 6 afforded dimethyl 6, 6'-dimethoxy-3, 3',5, 5'-tetramethyldiphenate (7). Reduction of 7 with LiAIPU yielded 2, 2'-di(hydroxymethyl)-6, 6'-dimethoxy-3, 3', 5, 5'-tetramethylbiphenyl (8), which was converted into 2, 2'-di(chlo-romethyl)-6.6'-dimethoxy-3,3', 5, 5'-tetramethylbiphenyl (9) via the dimesylate of 8. A new phenanthrene synthesis which involved treatment of 9 with sodamide in ammonia afforded 4, 5-dimethoxy-l, 3, 6, 8-tetramethylphenanthrene (11) in almost quantitative yield. Demethylation of 11 by heating with pyridine hydrochloride or with anhy-drous sodium sulfide yielded 4, 5-dihydroxy-l, 3, 6, 8-tetramethylphenanthrene (1), which could not be oxidized to a monomeric quinone. © 1977, American Chemical Society. All rights reserved.