2-Methoxy-1,4-naphthoquinone

Identical kinetics are exhibited in the analogous oxidations of 1- and 2-methoxynaphthalene to 4-methoxyl-l-naphthyl acetate and 2-methoxy-1,4-naphthoquinone respectively . In these cases the radical-cations may react with acetate ion thus... 

Fig. 10. The structures of 2-methoxy-1,4-naphthoquinone and stigmasta-7,22-diene-3P-ol (spinasterol) with anti-HP activities, isolated from Impatiens balsamina L.

The reaction of diazo(trimethylsilyl)methane (1) with quinones leads mainly to indazoles, the products of a [3 + 2] cycloaddition between the diazo function and a C-C double bond followed by desilylation and oxidation.In contrast, 2-methyl-l,4-naphthoquinone and 2-methoxy-1,4-naphthoquinone require higher reaction temperatures, and no trace of a heterocyclic compound can be detected, rather the trimethylsilyl-substituted cyclopropanes 5 are formed as a mixture of diastereomers. 

Cultured plant cells may also serve as sources of various naphthoquinones and benzoquinones, whether or not they are present in the whole plants. For example, suspension cultures of Panax ginseng C. A. Meyer were treated with either an elicitor preparation from the phytopathogenic Botrytis cinerea or a yeast elicitor preparation, and the accumulation of a new compound (2,5-dimethoxy-l,4-benzoquinone), which was not detected in non-elicited cultures, was observed [345], Induction of naphthoquinone formation in Impatients balsamina cell cultures was achieved by using parent plants yielding high levels of 2-methoxy- 1,4-naphthoquinone as initiated explants. The cell cultures were capable of producing two naphthoquinones, lawsone... 

Photocycloaddition. Synthesis of the highly carcinogenic polycycHc hydrocarbons, eg (51) [72735-91-2] may be affected by photocycloaddition of 2-bromo-3-methoxy naphthoquinone [26037-61-6] with 1,1-diarylethylenes such as l,l-bis(p-methoxyphenyl)ethene (41). 

Nucleophilic Substitution Reactions. Many of the transformations reali2ed through Michael additions to quiaones can also be achieved usiag nucleophilic substitution chemistry. In some iastances the stereoselectivity can be markedly improved ia this fashion (100), eg, ia the reaction of ben2enethiol with esters (R = CH C O) and ethers (R = 3) 1,4-naphthoquiaones. 2-Bromo-5-acetyloxy-l,4-naphthoquiQone [77189-69-6J, R = Br, yields 75% of 2-thiophenyl-5-acetyloxy-l,4-naphthoquinone [71700-93-1], R = SC H. 3-Bromo-5-methoxy-1,4-naphthoquinone [69833-10-9], R = Br, yields 82% of 3-thiophenyl-5-methoxy-l,4-naphthoquinone [112740-62-2] R = SC H. ... 

The aqueous [4+2] cycloaddition reaction of 1,4-naphthoquinones 115 with methoxy cyclohexadiene performed in the presence of bovine serum albumin (BSA) is one of the first examples of protein-promoted Diels Alder reactions [79]. Some results are reported in Table 4.18. The globular protein does not affect the regioisomer ratio of adducts. The highest enantiomeric excess was obtained in the cycloaddition of juglone 115 (R = H) with 1-methoxy-1,3-cyclohexadiene 116. 

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). 

Wang YC, Li WY, Wu DC, Wang JJ, Wu CH, Liao JJ, Lin CK. (2009) In vitro activity of 2-methoxy-l, 4-naphthoquinone and stigmasta-7,22-diene-3P-ol from Impatiens balsamina L. against multiple antibiotic-resistant Helicobacter pylori. Evid Based Complement. Alternat Med 9 1-8. 

Ethyl (6-Methoxy-l,2-naphthoquinonyl-6) Cyanoacetate. The above naphthoquinone (21.7 g) is added to a solution of 500 cc of ethanol and 14 cc of ethyl cyanoacetate, followed by the addition of 32 cc triethylamine. A deep purple color will develop and the mixture should be swirled for 4 min to dissolve the quinone completely. A solution of 75.9 g of potassium ferricyanide in 320 cc of water is then added to the solution, causing a thick dark complex to form and separate. Redissolve by adding a soluhon of 24 g of sodium carbonate in 1,600 cc of water. Swirl or stir and filter through diatomaceous filter aid. Acidify the filtrate with 100 cc of 6 M sulfuric acid to precipitate 34.8 g of red-orange powder, which is oven dried at 70°. Reciystallize from ethyl acetate to get 19.3 g, mp 157-158.5°. The remaining filtrate is evaporated to a small bulk and reciystallization from ethyl acetate gives an additional 2.8 g of product. 

Methoxy-4-Cyanomethyl-l,2-Naphthoquinone. 10 g of the above acetate in 50 cc of alcohol is treated with 50 cc of 10% NaOH and 50 cc of water. Swirl or stir the solution for 25 minute to see the color change from purple to deep red. Filter with diatomaceous filter aid and acidify with 6 N hydrochloric acid. A resulting red-brown solid is collected and air dried to give 7.2 g of product. 

Methoxy-9,10-Dioxo-13-Cyanomethyl-5,8,9,10,12,14-Hexahydwphenanthrene. 1.95 g of the above naphthoquinone is suspended in 45 cc of absolute dioxane and 25 cc of butadiene in a glass lined autoclave and is heated for 47 hours. The cooled reaction is concentrated (by evaporation) and the residue is ciystallized from benzene in two crops, to give 1.45 g of product, which is reciystallized twice from methanol. 

N.A. Balsaminones, 2-methoxy-l, 4-naphthoquinone, saponins, quercitin, kaempferol derivatives, balsaminasterol, parinaric acid, hosenkosides.302 Remedy for rashes, pain caused by insect bites, anti-inflammation. 

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. 

A different class of polycyclic naphthoquinone dyes is based on the n apht h 12,361 i ndolizine -6,11 -dione system 14, which is readily accessible by condensation of 2,3-dichloro-l,4-naphthoquinone with active methylene compounds in the presence of pyridine [22], or by reaction of 2-methoxy-3-pyridino-1,4-naphthoquinone with an active methylene compound [23], In 14, the bridgehead nitrogen atom acts as an effective auxochrome, and hence orange to red colors are observed without further substitution. Derivatives of 14 (R = amide group) are of particular value as vat dyes and pigments. Related isomeric heterocyclic structures have also attracted interest, e.g., 15, a yellow disperse dye for polyester [24],... 

Molecular electrostatic potentials have been used to explain the regioselectivity exhibited in the Diels-Alder cycloaddition reactions between 1-trimethylsilyloxy-butadiene and the quinones 5-formyl-8-methyl-1,4-naphthoquinone, 5-methoxy-7-methyl-1,4-phenanthrenequinone, and 5,6,7-trimethyl-1,4-phenanthrenequinone.128 The intramolecular Diels-Alder reaction of masked o-benzoquinones (123) with a variety of dienes provides adducts (124) which rearrange to functionalized ris-decal ins (125) with complete stereocontrol of up to five stereocentres. This methodology ... 

Many synthetic applications have been reported of the photochemical reactions of halogen-substituted 1,4-naphthoquinones with 1,1-diarylethenes487 90, and with related electron-rich alkenes such as 1-aryl-l-trimethylsilyloxyethenes491 93, 2-trimethylsilyloxy-1-alkenes494, 2-methoxy-l-alkenes495 and allyltributylstannane496,497. The process is exemplified by the reaction of 2-bromo-3-methoxy-1,4-naphthoquinone derivatives (152) with 1,1-diphenylethene487 (equation 129). 

Another substitution reaction that is initiated by photochemical hydrogen abstraction is the replacement of the bromine atom in 2-bromo-8-methoxy-l, 4-naphthoquinone by an acyl group757. Irradiation of a solution in benzene of the quinone, butyraldehyde or capraldehyde and pyridine yields mixtures of acylated quinone and acylated hydro-quinone. In the first step, the excited quinone abstracts the aldehyde hydrogen atom and this is followed by bond formation between the acyl radical and C-2 of the quinone. The radical that is formed after departure of a bromine atom may either lose a hydrogen atom and yield acylated quinone or take up a hydrogen atom and become acylated hydro-quinone. 

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