Nitro-3-hydroxybenzoic acid

Hydroxybenzoic Acid, 3-Diazo-5-nitro or 3-Diazo-5-Nitro-Hydroxybenzoic Acid (called 5-Nitro-3-diazo-salicyls aure in Ger). 

Nitration of ///-hydroxybenzoic acid with filming nitric acid in the presence of sulfuric acid and acetic anhydride gives a mixture of the 2-nitro [602-00-6] and 4-nitro [619-14-7] substitution products. Bromination and iodination yield the 4-halogenated derivatives (4-bromo [14348-38-0] and 4-iodo [58123-77-6]). When ///-hydroxybenzoic acid is treated with formalin in the presence of hydrochloric acid, 4-hydroxyphthalide [13161 -32-5] is obtained as shown in equation (10). 

Nitro-2-hydroxybenzoic acid n-Butyl benzenesulfonate Nickel Raney... 

A stired mixture of 4-nitro-2-hydroxybenzoic acid, anhydrous potassium carbonate and n-butyl benzenesulfonate in xylene was refluxed under a continuous water separator for about 19 h. The insoluble potassium salts were filtered off and washed with hot dry toluene. The combined filtrate and washings were distilled under reduced pressure to remove the solvents, thereby leaving a residual oil which solidified on cooling. The solid yields of greater than 95% of n-butyl 4-nitro-2-n-butoxybenzoate (recrystallized from methanol). 

Chemical Name 4-Hydroxybenzoic acid [(5-nitro-2-furanyl)methylene]-hydrazide... 

Nitro- and halo-benzoic acids are obtained from the corresponding aldehydes in 84-90% yield.500 In a KOH melt at 190° w-hydroxybenzaldehyde gives 773-hydroxybenzoic acid almost quantitatively since the intermediate benzyl alcohol reacts with the potassium hydroxide according to the equation ... 

Nitration of p-cymene by fuming nitric add leads to 2,4-dinitrotoluene.1184 Heating 1,6-dihydro-l-methyl-6-oxonicotinic acid with nitric acid (d 1.52) under reflux gives 1-methyl-3,5-dinitro-2(li/)-pyridone in good yield.1185 2,6-Dibromo-4-nitrosophenol is formed quantitatively from 3,5-dibromo-4-hydroxybenzoic acid and sodium nitrite in aqueous alcohol.166,1183 Nitrous acid replaces hydroxymethyl groups in phenols by nitro groups,1186 and diazonium salts replace them by diazo groups.1187... 

The relation between the constant of the para acid and that of the ortho or meta acid varies with the nature of the substituent. While p-nitrobenzoic acid is a slightly stronger acid than m-nitro-benzoic acid, the constant of p-chlorobenzoic acid is only about one-half that of the meta acid. The case of p-hydroxybenzoic acid is a striking one while o-hydroxybenzoic acid and m-hy-droxybenzoic acid are more highly ionized than benzoic acid, the constant of the para acid is less than half that of benzoic acid. A satisfactory explanation of such facts as these would, no doubt, materially advance organic chemistry. The effect of a phenyl radical on a carboxyl group in a side-chain, is shown by the constants for phenylacetic acid, hydrocinnamic acid, and cinnamic acid. 

The Smiles-mediated aryl transfer requires the presence of strong electron-withdrawing substituents such as nitro on the phenol, yet no reaction was observed with a cyano or a phosphonate group. 4-Hydroxybenzoates and 2- and 4-hydroxybenzamides are not reactive in this reaction, but salicylic acid esters give the desired Ugi-Smiles adducts in good yields. The high acidity of nitrophenols could justify their good reactivity, but the behavior of other phenols could not be simply correlated with their pKg. For instance, 4-hydroxybenzoic acid... 

Literature procedures were employed in the synthesis of 4-amlno-3-hydroxybenzoic acid 1 (9) and 3-amlno-4-hydroxyphenylace-tic acid (10). The propanoic and propenoic compounds were obtained as outlined in Figure 1. In both Isomeric systems, the intermediate hydroxynitrobenzaldehydes were cleanly converted to the cinnamic acid derivatives by Knoevenagel condensation with malonic acid followed by spontaneous decarboxylation. Reduction of the nitro groups with sodium dithionate then gave the alkene... 

Procedure. Urine (20 ml.) acidified with 2 N sulfuric acid (2 ml.) is continuously extracted with ether. The extract, after removal of the ether, is neutralized with 0.02 N sodium hydroxide uang phenol red as the indicator and is diluted so that concentration of p-hydroxybenzoic acid is between 0.2 and 2 mg./lOO ml. This solution (5 ml.) is mixed with ethanol (5 ml.) and diazotized p-nitro-anlline (1 ml.). After 2 minutes sodium carbonate (3 ml.) is added and the solution is made up to 25 ml. with water. The absorption is measured immediately on a photoelectric absorptiometer uang a Chance OBI blue filter. The calibration curve is constructed using solutions containing 0.01 to 0.10 mg. of p-hydroxy-benzoic acid in 5 ml. 

In sulfuric acid and in the presence of nitrogen oxides, phenols give colored indophenols. In the reaction medium they give a blue or green solution, which after dilution with water turns red, and after alkalization becomes blue. A positive reaction is given by phenols with a free para-position, unless they are substituted with —OH, — NH2, — OCH3, — NO2, — CHO, — COOH, or — COCH3. For example, 3,5-xylenol, o-aminophenol, o-nitro-phenol, m-hydroxybenzaldehyde, m-hydroxybenzoic acid, and similar compounds do not react. 

Oxide, in N-00017 Nevazol NS, N-00067 3,3, 3"-[Nitrilotris(4,l-phenyleneazo)]tris[6-hydroxybenzoic acid], N-00075 Nitroanisole blue, N-00078 Nitroanthranilazo, N-00079 4 -Nitro-4-azobenzenecarboxylic acid ... 

Another MOF constructed from Cu paddlewheel SBUs and with 5-nitro-1,3-benzenedicarboxylate as the ligand can be used for the acetylation of methyl 4-hydroxybenzoate with acetic acid anhydride. The framework did not remain intact upon exposure to acetic acid, one of the reaction products [53]. 

These derivatives may be obtained by reduction of the appropriate nitro derivative catalytically or with a metal-acid system, or by Beckmann or Hofmann rearrangements of suitable acyl or carboxamido derivatives. 4-Aminobenzo[6]thiophene has also been prepared by means of a Bucherer reaction with 4-hydroxybenzo[6 Jthiophene. Several 5-aminobenzo[6]thiophenes have been prepared by cyclization reactions of p-acetamino-phenylthio derivatives. 6-Acetaminobenzo[6 Jthiophenes may be obtained from the corresponding 6-acetyl derivative by Schmidt or Beckmann rearrangements. 7-Aminobenzo[6 ]thiophene can also be prepared from 7-hydroxybenzo[6 ]thiophene by a Bucherer reaction (70AHC(ll)l77). 

Aminobenzo[6]thiophene is prepared from 7-hydroxybenzo[6]-thiophene by means of the Bucherer reaction it may be converted into 7-nitrobenzo[6]thiophene via the diazonium salt.84 5,7-Diamino-3-phenylbenzo[6]thiophene and its 2-carboxylic acid are prepared by reduction of the corresponding dinitro compound.334 Partial reduction of o,7-dinitro-3-phenylbenzo[6]thiophene-2-carboxylic acid with ethanolic ammonium sulfide affords 7-amino-5-nitro-3-phenylbenzo-[6]thiophene-2-carboxylic acid, the amino group of which may be replaced by hydrogen or iodine via the diazonium salt.334 7-Amino-4-methoxybenzo[6]thiophene is mentioned in the patent literature.560... 

Further bromination of 3,4,6-tribromo-5-hydroxybenzo[6]thio-phene affords the 2,3,4,6-tetrabromo derivative in the absence of acetate ion, and 3,4,4,6-tetrabromo-4,5-dihydrobenzo[6]thiophen-5-one in the presence of acetate ion. 421 On treatment of 3,4-dibromo-, 4,6-dibromo-, 3,4,6-tribromo-, or 2,3,4,6-tetrabromo-5-hydroxybenzo-[6]thiophene with nitric acid in acetic acid, the corresponding unstable orange crystalline 4-bromo-4-nitro-4,5-dihydrobenzo[6]thio-phen-5-one is obtained.152,421 Hence, once both positions ortho to the hydroxyl group in 5-hydroxybenzo[6]thiophene are occupied by bromine, the properties of these compounds are analogous to the properties of l-bromo-2-naphthol which, on bromination in acetic acid in the presence of acetate ion, affords l,l-dibromo-l,2-dihydro-naphthalen-2-one whereas, in its absence, it affords l,6-dibromo-2-naphthol.616 The behavior of l-bromo-2-naphthol and its derivatives on nitration is similar to that of 4,0-dibromo-5-hydroxybenzo[6]thio-phene and its derivatives.162,616... 

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