Stannous chloride quinones

Stannous chloride is used most frequently for the reduction of nitro compounds [177, 178, 179] and of quinones [180, 181], It is also suitable for conversion of imidoyl chlorides [182] and of nitriles [183] to aldehydes, for transformations of diazonium salts to hydrazines [184], for reduction of oximes [f[Pg.30]

Lithium aluminum hydride reduced p-benzoquinone to hydroquinone (yield 70%) [576] and anthraquinone to anthrahydroquinone in 95% yield [576]. Tin reduced p-benzoquinone to hydroquinone in 88% yield [174] Procedure 35, p. 214). Stannous chloride converted tetrahydroxy-p-benzoquinone to hexa-hydroxybenzene in 70-77% yield [929], and 1,4-naphthoquinone to 1,4-di-hydroxynaphthalene in 96% yield [180]. Other reagents suitable for reduction of quinones are titanium trichloride [930], chromous chloride [187], hydrogen sulfide [248], sulfur dioxide [250] and others. Yields are usually good to excellent. Some of the reagents reduce the quinones selectively in the presence of other reducible functions. Thus hydrogen sulfide converted 2,7-dinitro-phenanthrene quinone to 9,10-dihydroxy-2,7-dinitrophenanthrene in 90% yield [248]. 

Complete deoxygenation of quinones to hydrocarbons is accomplished in yields of 80-85% by heating with a mixture of zinc, zinc chloride and sodium chloride at 210-280° [932]. Refluxing with stannous chloride in acetic and hydrochloric acid followed by refluxing with zinc dust and 2 N sodium hydroxide reduced 4 -bromobenzo[5. 6 1.2]anthraquinone to 4 -bromo-benzo[5. 6 1.2]anthracene in 95% yield [181], and heating with iodine, phosphorus and 47% hydriodic acid at 140° converted 2-chloroanthraquinone to 2-chloroanthracene in 75% yield [222]. Also aluminum in dilute sulfuric add can be used for reductions of the same kind [151]. 

Di(phenylethynyl)-2,3-dihydrobenzo[6]thiophene-2,3-diol (165) is obtained on treating benzo[6]thiophene-2,3-quinone with lithium phenylacetylide. It is converted into 2,3-di(phenylethynyl)benzo[6]-thiophene on treatment with stannous chloride.472... 

One hundred grams (0.44 mole) of stannous chloride dihydrate is added to a boiling solution of 10 g. (0.0S8 mole) of tetrahydroxy-quinone in 200 ml. of 2.4iV hydrochloric add contained in a 1.5-1. beaker. The initial deep-red color disappears, and grayish crystals of hexahydro-xybenzene precipitate. Two hundred fifty milliliters of 12iV hydrochloric acid is added, and the mixture is heated... 

The acid/base properties of carbons are of particular interest in the present context, since it will be seen that catalytic activity of carbons may often be related to amounts of oxygen adsorbed or to the acid/base characteristics of carbons. Thus, for example, the carbon catalysed rate of auto-oxidation of stannous chloride in acid was found to be maximal when the carbons were activated at 550 °C (high oxygen adsorption), but the carbon catalysed oxidation of hydroquinone to quinone was maximal for activation at 875 °C (low oxygen adsorption). It would obviously be of considerable interest to relate catalytic activity with specific surface groups, and such cases will be discussed later in this Chapter. However, the difficulty of analysing surface groups does make the correlation difficult to make. 

Reduction of a quinone beyond the hydroquinone stage is noted only in the anthracene series. In the preferred laboratory procedure for the preparation of anthrone a mixture of anthraquinone, stannous chloride in coned, hydrochloric acid. 

Some of the materials which have been used to stabilize ethers and inhibit formation of peroxides include the addition of 0.001% of hydroquinone or diphenylamine, polyhydroxyl-phenols, aminophenols, and arylamines. Addition of 0.0001 g of pyrogallol in 100 cc ether was reported to prevent peroxide formation over a period of 2 years. Water will not prevent the formation of peroxides in ethers, and iron, lead, and aluminum will not inhibit the peroxidation of isopropyl ether, although iron does act as an inhibitor in ethyl ether. Dowex- 1 has been reported effective for inhibiting peroxide formation in ethyl ether, 100 parts per million (ppm) of 1-naphthol for isopropyl ether, hydroquinone for tetrahydrofuran, and stannous chloride or ferrous sulfate for dioxane. Substituted stilbene-quinones have been patented as a stabilizer against oxidative deterioration of ethers and other compounds. 

Actibomycin. Actinomycin A (164,170), CM-nHia-ssNT-sOs-in m.p. 250 C., red platelets, [ ]b — —320°, absorption peaks at 2400 and 4500 A soluble in acetone, alcohol, benzene, 10% hydrochloric acid slightly soluble in water and ether insoluble in dilute acids, dilute alkalies, and petroleum ether. It is readily reduced by sodium hydrosulfite and by stannous chloride but not by sodium bisulfite. Several groups can be acetylated. It seems to be a quinone containing free hydroxyl groups. Oxford (120) thinks that it may not be a true para quinone and that it might contain a polypeptide chain, like gramicidin, as well as a chromo-... 

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