1.3- Dihydroxy-4- benzene

Hydorxy benzene 1,4 Dihydroxy benzene 1,3 Dihydroxy benzene... 

Diazo coupling involves the N exocyclic atom of the diazonium salt, which acts as an electrophilic center. The diazonium salts of thiazoles couple with a-naphthol (605). 2-nitroresorcinol (606), pyrocatechol (607-609), 2.6-dihydroxy 4-methyl-5-cyanopyridine (610). and other heteroaromatic compounds (404. 611) (Scheme 188). The rates of coupling between 2-diazothicizolium salts and 2-naphthol-3.6-disulfonic acid were measured spectrophotometrically and found to be slower than that of 2-diazopyridinium salts but faster than that of benzene diazonium salts (561 i. The bis-diazonium salt of bis(2-amino-4-methylthiazole) couples with /3-naphthol to give 333 (Scheme 189) (612). The products obtained from the diazo coupling are usuallv highly colored (234. 338. 339. 613-616). 

Monoesterification of a symmetrical dihydroxy aromatic compound can be effected by reaction with polymer-bound benzoyl chloride (Pyr, benzene, reflux, 15 h) to give a polymer-bound benzoate, which can be alkylated with diazomethane to form, after basic hydrolysis (0.5 M NaOH, dioxane, H2O, 25°, 20 h, or 60°, 3 h), a monomethyl ether. ... 

Chloranilic acid (2,5-dichloro-3,6-dihydroxy-l,4-benzoquinone)/57-5S-77 M 209.0, m 283-284° pK l.22, pK 3.01. A soln of 8g in IL of boiling water was filtered while hot, then extracted twice at about 50° with 200mL portions of benzene. The aq phase was cooled in ice-water. The crystals were filtered off, washed with three lOmL portions of water, and dried at 115°. It can be sublimed in vacuum. [J Phys Chem 61 765 1957.] The diacetate has m 182-185° [7 Am Chem Soc A6 1866 1924 Thamer and Voight J Phys Chem 56 225 7952]. 

Dihydroxy-3-methylanthraquinone (chrysophanic acid) [481-74-3] M 245.3, m 196 , PKesi(I) 8.2, pKest(2) 12.4. Crystd from EtOH or benzene and sublimed in a vacuum. 

Oxidation of the 3-hydroxy-A systenli with manganese dioxide in refluxing benzene affords a moderate yield of the corresponding 4,6-dien-3-one. These vigorous conditions also suffice to cleave the corticoid side chain (17a,21-dihydroxy-20-ketones) to give 17-keto steroids. ... 

The enamine (1 g) in 30 ml of benzene and 5 ml of toluene is treated, with cooling, with a solution of 0.33 g (1.04 eq.) of perbenzoic acid in 2.1 ml of benzene. The reaction is complete in a few minutes. Ether (30 ml) is added, then the solution is washed with 2 N sodium hydroxide and with water to neutrality, dried over sodium sulfate and evaporated under reduced pressure. Crystallization from acetone gives 0.51 g of crude product mp 230°. One further crystallization from methanol gives 0.38 g (50%) of 3J5,17a-dihydroxy-5a-pregnan-20-one rap 265°. 

The three dihydroxy derivatives of benzene may be naned as 1,2-, 1,3-, and 1,4-benzenediol, respectively, but each is more faniliaily known by the common nane indicated in parentheses below the structures shown here. These common names are permissible lUPAC nfflnes. 

Nevertheless the Elbs reaction is a valuable method for the preparation of dihydroxy benzenes. The experimental procedure is simple, and the reaction conditions are mild a variety of functional groups is tolerated. 

A solution of 1.0 g of A -3,11-diketo-20-cyano-21-acetoxy-pregnene in 10 cc of benzene is treated with 1.0 g of osmium tetroxide and 0.43 g of pyridine. After standing at room temperature for 18 hours, the resulting solution is treated successively with 50 cc of alcohol, and with 50 cc of water containing 2.5 g of sodium sulfite. The mixture is stirred for 30 hours, filtered, and the filtrate acidified with 0.5 cc of acetic acid and concentrated to small volume in vacuo. The aqueous suspension is then extracted four times with chloroform, the chloroform extracts are combined, washed with water and concentrated to dryness in vacuo. Recrystallization of the residue from acetone gives 3,11,20-triketo-17(a)-21-dihydroxy-pregnane MP 227° to 229°C. This compound is then treated with acetic anhydride and pyridine for 15 minutes at room temperature to produce 3,11,20-triketo-17(a)-hydroxy-21-acetoxy-pregnane or cortisone acetate. 

A solution of 30 parts by weight of pinacolin alcohol in ether is saturated with hydrogen chloride at room temperature and the ether solution then agitated with bicarbonate. After concentration by evaporation it leaves behind the crude diethylstilbestrol [a,j3-(p,p -dihydroxy-diphenyl)-Oi, 3from benzene, melts at 170°C to 171 °C. The yield amounts to 75% of the calculated. The total y eld of diethylstilbestrol, calculated on p-hydroxypropiophenone, is 68% of the theoretical. 

Dione 21-Acetate To a stirred solution of 500 mg of 9o-fluoro-11(3,21-dihydroxy-16-methyl-1,4,16-pregnatriene-3,20-dione 21-acetate in 5 ml of benzene and 5 ml of chloroform are added 0.50 ml of t-butyl hydroperoxide and 0.1 ml of a 35% methanolic solution of benzyl-trimethyl ammonium hydroxide. After 18 hours at room temperature, water is added and the mixture thoroughly extracted with chloroform. The chloroform extract is washed with saturated aqueous sodium chloride and dried over magnesium sulfate. Evaporation of the Solvent and crystallization of the residue from acetone-ether gives Bo-fluoro-... 

Alternatively, 25.0 g of either 3j3,5a-dihydroxy-17a-methyl-17j3-carbomethoxyandrostan-6-one (Ilia) or 25.0 g of its 3)3-acetate (Hlb), are dissolved in dry tetrahydrofuran (1,250 ml, freshly distilled over lithium aluminum hydride) and dry benzene (2,000 ml) is added. Methyl magnesium bromide in ether solution (3 M, 750 ml) is added to the stirred solution and the resulting mixture is stirred at room temperature for 16 hours. An additional quantity of methyl magnesium bromide solution in ether (2M, 375 ml) is added, and 1,250 ml of the solvent mixture are distilled off. The resulting mixture is refluxed for 5 hours and worked up as described above, yielding compound (V) as a colorless oil. 

The combined benzene layers were dried over anhydrous sodium carbonate and the solvent was removed at reduced pressure to give 90.5 g of crude crystalline 5a,17a-dihydroxy-6j3-methylallopregnane-3,20-dione 3,20-bis-(ethylene ketal). Half of the residue, 45.2 g, was... 

Dihydroxy benzene sulfonic acid Sultosilic acid piperazine salt... 

Benzenediol, quinol, or p-dihydroxy benzene [CgH4-l,4-(OH)2] has a MW of 110.1. It is a white crystalline powder formed by the reduction of p-benzoquinone [quinone, CgH4 ( 0)2],... 

A new approach to the resolution of sulphoxides 242 was recently reported by T oda and coworkers282. It takes advantage of the fact that some sulphoxides form crystalline complexes with optically active 2,2 -dihydroxy-l, 1-binaphthyl 243. When a two-molar excess of racemic sulphoxide 242 was mixed with one enantiomeric form of binaphthyl 243 in benzene-hexane and kept at room temperature for 12 h, a 1 1 complex enriched strongly in one sulphoxide enantiomer was obtained. Its recrystallization from benzene followed by chromatography on silica gel using benzene-ethyl acetate as eluent gave optically pure sulphoxide. However, methyl phenyl sulphoxide was poorly resolved by this procedure and methyl o-tolyl, methyl p-tolyl, s-butyl methyl and i-propyl methyl sulphoxides did not form complexes with 243. 

In contrast to the difluorobenzenes, the ortho isomer of the dihydroxy-substituted benzenes is the most stable followed by the meta and then the para isomer. The meta isomer is 0.9 kcal/mol above the ortho isomer and the para is 2.4 kcal/mol higher. The para/ortho ratio has been measured as 6 94 over HZSM-5 catalysts.2 Although the temperature at which this measurement was made was not originally reported, the ratio is approximately invariant over the range of 250-350°C. Taking 250°C as the temperature, we obtain AG (ortho-para) =2.9 kcal/mol. 

It is a lipophilic compound which removes intercellular lipids that are covalently linked to the cornified envelope surrounding epithelial cells [3]. It also enhances penetration of other agents. Resorcinol (m-dihydroxy benzene) is structurally and chemically similar to phenol. It disrupts the weak hydrogen bonds of keratin [4]. Lactic acid is an alpha hydroxy acid which causes corneocyte detachment and subsequent desquamation of the stratum corneum [5]. 

Silver nitrate 1,2- and 1,4-dihydroxy-benzene oxidation to corresponding benzoquinones [208]... 

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