4- phenol 4-Methoxy-1,2-naphthoquinone

The synthesis of the naphthoquinone 116 is shown in Scheme 3.24. Bromination of juglone (118) afforded the dibromojuglone derivative 134. Protection of the phenol group as its methoxymethyl ether formed the product 135 (50 % yield over two steps). Finally, the C-3 bromide substituent was regioselectively substituted with methoxide by heating 135 in methanol in the presence of sodium carbonate (96 %). The methoxy group was installed to impart electronic bias to the naphthoquinone in the TASF(Et) coupling (vide infra). 

When hypofluorous acid reacts with aromatic substrates 7 the isomeric distribution of phenols formed suggests the nature of the transformation is electrophilic, rather than radical 4-methoxy(2-2H)phenol (8) isolated from (4-2H)anisole shows a marked NIH effect (77% incorporation of deuterium).11 A similar reaction with naphthalene gives a mixture of up to three products in low yield (1-naphthol 2.9%, 2-naphthol 0.75% and 1.4-naphthoquinone 7.4%).9... 

Phenoxazin-3-ones and phenothiazin-3-ones can be prepared by the oxidation of the parent heterocycles in acidic media, but it is often more practical to employ condensation reactions between 2-amino-phenols or -thiols and quinones. Alizarin Green G (263), for example, is obtained from the aminophenol (261) and the 1,2-naphthoquinone (262). Similarly, 2-aminothiophenols (264) and 6-chloro-2-methoxy-l,4-benzoquinone (265) afford phenothiazin-3-ones (266) bearing methoxyl groups at position 1. 

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