Naphthoquinone, sodium hydroxide

Alkannin occurs in the roots of the plant as the alkah-sensitive ester of angelic acid (62). It may be extracted from the roots by using boiling light petroleum ether. Treatment of this extract with dilute sodium hydroxide gives a blue solution from which the dye is precipitated by the addition of acid. The cmde product is purified by vacuum sublimation (63). Its stmcture (11) is a hydroxylated naphthoquinone with a long, unsaturated side chain (64,65) it has the (3)-configuration. 

In the case of diuretics the chromatogram is Erst sprayed with sodium hydroxide solution (c = 1 mol/L) and then with a saturated solution of l,2-naphthoquinone-4-sulfonic acid sodium salt in ethanol — water (50-1-50) [11]. Stable orange-colored chromatogram zones appear over a period of ca. 15 min, their intensity increases on storage in the dark (1-2 days) [11]. 

Condensed derivatives have also been prepared. Reaction of 2-aminothi-azoles with 2,3-dichloro-l,4-naphthoquinone yields naphth[2,3-h]im-idazo[2,l-h]thiazole-5,10-dienones 62 via thiazolylaminoquinones 61. Cycli-zation can be effected either with diethylaniline (method a) [77IJC(B)356] or with sodium hydroxide and tetrabutylammonium bromide (TBAB) catalyst (method b) (82H333). Following route b, compound 62 (R = Et) can be isolated in 92% yield. Reactions between 2-aminothiazoles and chloranil leading to dithiazolobenzobisimidazolediones have also been reported [79IJC(B)523]. 

The Williamson synthesis, using a sodium phenoxide and allyl bromide in methanol solution, is more rapid than the procedure using acetone and potassium carbonate and gives good results.16-36 441 66 Aqueous acetone also has been used as the reaction medium with allyl bromide and sodium hydroxide this method likewise is rapid and sometimes leads to better yields than the procedure using potassium carbonate and acetone.34 Allylation of 2-hydroxy-l,4-naphthoquinone has been carried out by treating the silver salt, in benzene, with allyl bromide 84 some C-alkylation as well as O-alkylation was observed. 

To a stirred suspension of 2-amino-1,4-naphthoquinone (173 mg, 1 mmol) in dichloromethane (15 ml) was added [hydroxy(tosyloxy)iodo]benzene (411 mg, 1.05 mmol). After 20 min, the yellow iodonium salt which separated was collected, washed with dichloromethane and dried (520 mg, 95%). This salt (547 mg, 1 mmol) was added to a cold aqueous solution of 2% sodium hydroxide (2 mmol). The mixture was stirred until the yellow colour turned red, about 20 min the precipitate was collected, washed with water and ether and dried to give 2-phenyliodonio-l,4-naphthoquinone-3-imide (263 mg, 70%), m.p. 115-117°C. 

Pd-C.198 A high yield of o-hydrazotoluene was obtained by hydrogenation over 5% Pd-C in a two-phase solution containing alcohol/THF and aqueous sodium hydroxide in the presence of 2,3-dichloro-1,4-naphthoquinone (eq. 9.70). 

Synthetically, 2,3-dihydro-l,4-benzoxazine-6,7-diones (391) can be prepared from 2,5-bisanilino-3-acetyl- (or methoxycarbonyl)-l,4-benzoquinones and substituted 2-hydroxyethylamines (73T2881). 2-Amino-3-aziridino-1,4-naphthoquinone, when heated in aqueous sodium hydroxide, is claimed to give 392 (69FES732), and the benzo analog was prepared from 2,3-dichloro-... 

Dissolve 1 g of the aminonaphthoquinonimine hydrochloride (2) reserved from Experiment 2 in 25 mL of water, add 2 ml of concentrated ammonia solution (den 0.90), and boil the mixture for 5 min. The free quinonimine initially precipitated is hydrolyzed to a mixture of the aminoquinone 7 and the isomer 6. Cool, collect the precipitate and suspend it in about 50 mL of water, and add 25 mL of 10% sodium hydroxide solution. Stir well, remove the small amount of residual 2-amino-1,4-naphthoquinone (6) by filtration, and acidify the filtrate with acetic acid. The orange precipitate of 7 is collected, washed, and crystallized while still wet from 500-600 mL of hot water (the separation is slow). The yield of orange needles, which decomposes about 270°C, is about 0.4 g. 

Electrochemistry427 can be used to regenerate an expensive or toxic reagent in situ. An example is the electrical regeneration of periodate that is used for the oxidation of vicinal diols such as sugars. When used with osmium oxidations, it can keep the level of the toxic metal reagent quite low. In Chap. 4, an example of the conversion of a naphthoquinone to its epoxide by electrolysis of aqueous sodium iodide was given. The sodium hydroxide and iodine produced by electrolysis react to form hypoiodite that adds to the double bond to form the hydroxyiodide, which then eliminates sodium iodide by the action of the sodium hydroxide to re-form the sodium iodide.428 Electricity can be used in oxidations and... 

Sodium Hydroxide and Methyl Alcohol. On reacting nitrobenzene with methanol and caustic soda, azoxybenzene is the main reduction product formed. Sodium formate is obtained as the oxidation product of the methanol used. Naphthoquinone and its substitution products are promoters of this reaction. ... 

Stabilization of a radical anion of humic acid may be caused by an adsorption effect. Bijl (3) observed that solid barium hydroxide octahydrate turned blue when placed in a solution of quinhydrone the blue solid was highly paramagnetic. Under the conditions we used for preparing these salts, insoluble sodium humate (with a large surface area) could have stabilized the anion radical by adsorption from the basic solution. Weiss and McNeil (18) observed a similar phenomenon with base soluble xanthenes, and proposed that biradicals may be formed in such a system. His compounds, however, do not appear to have the structural requirements to satisfy such a stabilized system. The recent report by Weber (29) on the spin content increase associated with the basification of a naphthoquinone-naphthohydroquinone system seems to parallel our observations quite closely. 

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