Amino-p-quinones

The red products obtained from the interaction of tyrosine and either o- or p-benzoquinone described by Bouchilloux 285 are probably 4-amino-o-quinone and 3-amino-p-quinone derivatives, respectively. 

In support of this view the p-amino-phenols themselves readily yield quinones. Also most p-substituted primary amines, e.g., p-diamines, p-alkylamines, such as p-toluidine, sulphanilic acid and its derivatives, behave similarly. In fact, the reaction can be used as a test for p-substi-tuted primary amines. p-Benzoquinone is usually made from aniline for the other p-quinones the p-amino-phenols, which are easily obtained by reduction of the p-nitroso-phenols and of azo-phenols, are employed. These reactions also apply, but not so widely, in the naphthalene series. 

A complex reaction mixture was obtained when the amino compound 39 was oxidized with Fremy s salt. In addition to the anticipated quinone 40 (6.9% yield), the dimeric quinones 41 (2.9% yield) and 42 (4.9% yield) were also obtained. On the other hand, the aromatic analog 43 gave only 40 in 43% yield and the compound rearranged under the influence of acid into the p-quinone 44 (72CPB1785). 

A similar mechanism operates in quinone methides with an amino substituent in the methide group. The p-quinone methide 22 has a C=C barrier of 14.5 kcal mol" and a C—N barrier of 114 kcal mol ... 

Reactions of aldehydes and their derivatives have been the subject of several reports. Benzene-1,2-dicarboxaldehyde condenses" with 2,3-dihydro-naphthazarone to give the p-quinone (75), and a similar reaction occurs between diketones such as PhCOCH2CH2COPh and naphthalene-1,4-diol. 4-Nitrobenzaldehyde undergoes disproportionation in the presence of cyanide ions and methanol, resulting in methyl 4-nitrobenzoate as the main product. The acid-catalysed rearrangement of arylhydrazones (76) derived from aromatic aldehydes and diaryl ketones leads to amino-biphenyls (77). 

The Nenitzescu reaction generally occurs under relatively mild reaction conditions. Moreover mono-, di-, and tri-substituted quinones react with equal facility. Many enamines including p-aminoacrylonitriles, p-aminoacrylamides, and p-amino-a,p-unsaturated ketones react with quinones to form indole nuclei as well. The mild reaction conditions and the availability of the starting material render it attractive even in those instances where the yield of the product is low. ... 

Oxidations of pyridopyrimidines are rare, but the covalent hydrates of the parent compounds undergo oxidation with hydrogen peroxide to yield the corresponding pyridopyrimidin-4(3 T)-ones. Dehydrogenation of dihydropyrido[2,3-(i]pyrimidines by means of palladized charcoal, rhodium on alumina, or 2,3-diehloro-5,6-dicyano-p-benzo-quinone (DDQ) to yield the aromatic derivatives have been reported. Thus, 7-amino-5,6-dihydro-1,3-diethylpyrido[2,3-d]-pyri-midine-2,4(lif,3f/)-dione (177) is aromatized (178) when treated with palladized charcoal in refluxing toluene for 24 hours. 

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