1,4-Naphthoquinone, by oxidation

Benzoquinone ( quinone ) is obtained as the end product of the oxidation of aniline by acid dichromate solution. Industrially, the crude product is reduced with sulphur dioxide to hydroquinone, and the latter is oxidised either with dichromate mixture or in very dilute sulphuric acid solution with sodium chlorate in the presence of a little vanadium pentoxide as catalyst. For the preparation in the laboratory, it is best to oxidise the inexpensive hydroquinone with chromic acid or with sodium chlorate in the presence of vanadium pent-oxide. Naphthalene may be converted into 1 4-naphthoquinone by oxidation with chromic acid. 

CMral tpoxyiutphthoquinones. Pluim and Wynberg1 have prepared a number of Optically active epoxides of 2-alkyl- and 2,3-dialkyl-l,4-naphthoquinones by Oxidation with 30% H202, aqueous NaOH, and benzylquininium chloride. Enantiomeric excesses of 43% can be realized, and these can be improved by Oiyitallization. The authors also report that the most satisfactory method for preparation of 2-alkyl-1,4-naphthoquinones is that of Jacobsen (5, 17 8, 18). 

In 1885, from a detailed study of juglone (52) it was proposed that its stmcture was 5-hydroxy-l,4-naphthoquinone (9). This stmcture was confirmed by oxidizing 1,5-dihydroxynaphthalene with potassium dichromate in sulfuric acid (53). Juglone occurs in walnuts as a glycoside of its reduced form, 1,4,5-trihydroxynaphthalene (54). Later it was deterrnined that the sugar is in the 4-position (10) (55). 

The reaction mechanism has not been elucidated. It is possible that formaldehyde reacts by oxidation as in the Marquis reaction (see formaldehyde — sulfuric acid reagent), whereby colored salts are formed with naphthoquinone sulfonic acid. 

Thor, H., Smith, M.T., Hartzell, P., Bellomo, G., Jewell, S.A. and Orrenius, S. (1982). The metabolism of menadione (2-methyl-1,4-naphthoquinone) by isolated hepatocytes. A study of the impact of oxidative stress in the intact cell. J. Biol. Chem. 257, 12419-12425. 

By contrast, alkylamination of naphthazarin (7) in the presence of sodium dithionite followed by oxidation gives l,4-bis(alkylamino)-5,8-naphthoquinone (31).18,19 However, Kikuchi and co-workers20 obtained isomeric l,5-bis(alkylamino)-4,8-naphthoquinone (32) from the reaction of leuco naphthazarin (33) with alkylamine They also isolated 5-alkylamino-leuco-naphthazarin (34) as an intermediate, which is further aminated at the 1-position to give 32. Bloom and Dudek21 have studied the structure of leuco aminonaphthoquinones and their tautomeric equilibria in solution. They concluded that the reaction of leuco naphthazarin (33) or the leuco compound (35) derived from l,5-diamino-4,8-naphthoquinone (36) with methylamine gives mixtures of l,4-bis(methylamino)-31 (R = Me) and 1,5-bis(methylamino)naphthoquinones 32 (R = Me) after oxidation of leuco aminonaphthoquinones (Scheme 10). Some of the structures of leuco aminonaphthoquinones are shown in Scheme ll.20... 

I. 1.4.1] catalyzes the reaction of 2-methyl-3-phytyl-l,4-naphthoquinone with oxidized dithiothreitol and water to produce 2,3-epoxy-2,3-dihydro-2-methyl-3-phytyl-l,4-naphthoquinone and 1,4-dithiothreitol. In the reverse reaction, vitamin K 2,3-epoxide is reduced to vitamin K and possibly to vitamin K hydroquinone by 1,4-dithioer-ythritol (which is oxidized to the disulfide). Some other dithiols and butane-4-thiol can also act as substrates. This enzyme is strongly inhibited by warfarin. 

Bcnzofuran-4,7-dioncs have been synthesized regioselectively by [3 + 2] photoaddition of 2-hydroxy-1,4-benzoquinones with a range of alkenes (equation 185)664. The reaction occurs in 30-60% yield and is a useful method for the synthesis of the benzofuran ring system, which is important in natural products like acamelin665. Substituted naphthoquinones may also be used in this reaction666,667 and this has lead to a very simple two-step synthesis of maturinone. In a similar reaction, a [3 + 2] photoaddition reaction of 2-amino-1,4-naphthoquinones with electron-rich alkenes gave 13-82% yields of 2,3-dihydro-177-bcn/ /]indole-4,9-diones in a single-step process which involved photolysis followed by oxidation (equation 186)668,669. 

Heating o-nitrosophenols with hydroxylamine is reported to give furazans, naphtho[l,2-c]furazan (95) being formed from both l-nitroso-2-naphthol and 2-nitroso-l-naphthol, presumably by oximation of the tautomeric o-naphthoquinone monooximes and subsequent dehydration. Compound (95) has also been prepared by oxidation, using alkaline ferri-cyanide or hypochlorite, of l-amino-2-nitroso- and 2-amino-l-nitroso-naphthalene. This latter approach is suitable for heterocyclic fused furazans thus 4,6-diamino-5-nitrosopyrimidine is converted into the furazanopyrimidine (96) by oxidation with lead tetraacetate (71JOC3211). In a similar reaction alkaline hypochlorite oxidizes o-nitrosoacetaniiide to benzofurazan in quantitative yield. 

Benzo[fe]xanthene-6,l 1,12-triones are readily available through the photo-induced 1,4-acylation of naphthoquinone with 2-hydroxybenzaldehydes followed by oxidation <02H(57)1915>. Chromone-3-carboxaldehyde reacts with o-benzoquinodimethane in a DA reaction with concomitant deformylation to give a diastereoisomeric mixture of tetrahydrobenzo[fc]xanthones oxidation can be accomplished with DMSO/I2 <02T105>. 

Naphthoquinone pesticides are synthesized either starting from naphthalene via chlorination and oxidation, or starting from naphthoquinone by chlorination. 

The a- and p-tetralones are also oxidized to 2-hydroxy-1,4-naphthoquinone by KO, and a crown ether in 75% yield. In the absence of a crown ether, the oxidation proceeds slowly and in low yield (—10%). The a- and p naphthols are intermediates. ... 

Hydroxy-naphthochinon-( 1,2), 7-Hydroxy-1,2-naphthoquinone). (HO).CioHs (0)2, mw 174.16, OB to CO2 —183.74%, dark red microcrysts, mp 203 —204° (decompn). Sol in ale AcOH. Prepn from l-amino-2,7-dioxy-naphthalene by oxidation with chromic-sulfuric acid Refs 1) Beil 8, 299, (634) 2542 2) S. Mededeco O. Bloch, ChemZtr (1935), 2670... 

Dithioacetic acid derivatives add to 1,4-benzo- or 1,4-naphthoquinones to give, after oxidation of the adduct with silver oxide or chloranil, the quinones 217 and 218 (69LA103). Quinones 218 were prepared also from 2,3-dichloro-1,4-naphthoquinone and salts of dithiocarbamic acids (51JA3459) and those of type 219 by oxidation of the corresponding hydroquinones. From reduction potentials and the semiquinone formation constants, it was concluded that their anion radicals are thermodynamically stable (86CC1489). 

Dichlorophthalazine-5,8-dione was obtained in low yield by oxidative chlorination of 5-aminophthalazine (86JMC1329). 1,4-Naphthoquinone reacts with hydrazine to give a black compound, for which the structure of a pentacyclic quinone (289) was establisheii (67T2911). The compound is identical with the product from treatment of binaphthoquinone with hydrazine and for which a hydrazone structure was postulated previously (39CB1623). 

Introduction. The quinones are intermediate products in the oxidation of the aromatic nucleus. They may be prepared in some cases by the direct oxidation of aromatic hydrocarbons. For example, anthracene, naphthalene, and phenanthrene are oxidized to the corresponding quinones by chromic acid mixtures. Quinones are prepared more conveniently by oxidation of primary aromatic amines, particularly the p-substituted amines. p-Benzoquinone is obtained by the oxidation of aniline, p-toluidine, sulfanilic acid, p-aminophenol, and other similar compounds. Similarly the a-naph-thoquinone is obtained by oxidation of 1,4-aminonaphthol, and /9-naphthoquinone by the oxidation of 1,2-aminonaphthol. In the laboratory, although it is possible to prepare p-benzoquinone by the oxidation of aniline with acid-dichromate mixture, the method is tedious and the yield poor. Since hydroquinone is used extensively as a photographic developer and is made industrially, it is more convenient to prepare quinone by its oxidation. 

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