Ethanol diazonium acids

This gradation is illustrated by the results obtained with the diazonium salts from the isomeric aminobenzoic acids. When the orthQ diazonium nitrate is treated with absolute ethanol only reduction occurs ethyl benzoate is obtained in 53% yield.f The diazonium acid sulfate derived from m-aminobenzoic acid is converted into a mixture of ethyl benzoate and ethyl m-ethoxybenzoate, the former preponderating. - Finally, with the p-diazonium salts the ether reaction is the favored one - from the nitrate the yields of p-ethoxybenzoic acid and ethyl benzoate are 60% and 12%, respectively. 

Diazotization in the presence of sulfuric acid affords a simple means of avoiding the exchange reaction since diazonium acid sulfates do not rearrange. Thus, by treating the diazonium acid sulfate of tribromoaniline with boiling ethanol, pure tribromobenzene is obtained in about 80% yield. Even pentabromoaniline suffers no loss of bromine when deaminated via the diazonium acid sulfate. ... 

This reaction, promoted by ethanolic hydrochloric acid at 0-20 , was discovered by Griess and Martins in 1886, and is important in dyestuffs manufacture . Little controversy has arisen over mechanism, which has since 1885 been accepted as fission to a diazo compound or diazonium ion (characterise by coupling with scavenger) and amine (isolable) and recoupling. The marked catalytic effect of arylamines (in acid media) is attributable to reaction (92) , ... 

Difluorodiphenyl. Bis-diazotise a solution of 46 g. of benzidine (Section IV,88) in 150 ml. of concentrated hydrochloric acid and 150 ml. of water by means of a solution of 35 g. of sodium nitrite in 60 ml. of water add about 200 g. of crushed ice during the process (compare p-Fbtorotoluene above). Filter the solution and add it to a filtered solution of 85 g. of sodium borofluoride in 150 ml. of water. Stir for several minutes, collect the precipitated bis-diazonium borofluoride by suction filtration, wash with 5 ml. of ice-cold water, and dry at 90-100°. Place the dry salt in a flask fitted with an air condenser, immerse the flask in an oil bath, and slowly raise the temperature to 150° (Fume Cupboard ). When decomposition of the salt is complete, steam distil the mixture collect the 4 4 difluoro-diphenyl which passes over and recrystallise it from ethanol. The yield is 21 g., m.p. 92-93°. 

Chlorodiphenyl. Diazotise 32 g. of o-chloroaniline (Section IV,34) in the presence of 40 ml. of concentrated hydrochloric acid and 22 -5 ml. of water in the usual manner (compare Section IV,61) with concentrated sodium nitrite solution. Transfer the cold, filtered diazonium solution to a 1 5 htre bolt-head flask surrounded by ice water, introduce 500 ml. of cold benzene, stir vigorously, and add a solution of 80 g. of sodium acetate trihydrate in 200 ml. of water dropwise, maintaining the temperature at 5-10°. Continue the stirring for 48 hours after the first 3 hours, allow the reaction to proceed at room temperature. Separate the benzene layer, wash it with water, and remove the benzene by distillation at atmospheric pressure distil the residue under reduced pressure and collect the 2-chlorodiphenyl at 150-155°/10 mm. The yield is 18 g. Recrystalliae from aqueous ethanol m.p. 34°. 

It IS possible to replace ammo substituents on an aromatic nucleus by hydrogen by reducing a diazonium salt with hypophosphorous acid (H3PO2) or with ethanol These... 

Reductive deamination of primary arylamines The ammo substituent of an arylamine can be replaced by hydrogen by treatment of its de rived diazonium salt with ethanol or with hypophosphorous acid... 

Both 2- and 3-nitrothiophenes are reduced by tin and hydrochloric acid to the corresponding aminothiophenes. In contrast to anilines, the free bases are very unstable their salts and acyl derivatives, however, are stable. 2-Aminothiophene can be diazotized and the resulting diazonium salt coupled with /3- naphthol. The chemical instability of aminothiophenes compared with aniline is illustrated by the ring opening of 2-amino-3-ethoxycar-bonylthiophenes (157) with ethanolic sodium ethoxide to give cyanothiolenones (158) <75JPR861). 

Can be prepd by the nitration of 1-phenyltetrazole with fuming nitric acid, or by heating sym diformyl-hydrazine, OHC.HN.NH.CHO, and p-nitrobenzene-diazonium chloride, 02N.C6H4.N2C1, with dil Na hydroxide soln. Insol in w and ligr, diff sol in benz and eth, sol in ethanol and methanol, v sol in acet. Puffs off when heated above its mp Refs 1) Beil 26, 347 (109) 2)M. Freund ... 

In most cases diazonium salts are not isolated, but are converted into products by reactions that can be carried out in situ. Moreover, it is actually recommended not to isolate these salts, not even for purification purposes, as many of them have a tendency to explode. In addition, the high solubility of most diazonium salts in water makes precipitation from this medium difficult. Therefore, to obtain solid diazonium salts the recommended method for many decades was to carry out diazotizations in ethanol followed by precipitation with ether. As inorganic salts of nitrous acid are scarely soluble in ethanol, Knoevenagel recommended alkyl nitrites (ethyl or isopentyl nitrite) as diazotization reagents as long ago as 1890. Various other solvents have subsequently been used for diazotizations with alkyl nitrites (see Saunders and Allen, 1985, p. 23 ff.), but as a method for obtaining solid diazonium salts this has been superseded by the isolation of diazonium tetrafluoroborates and, to a lesser degree, of hexafluorophosphates. 

In 1988 Masoud and Ishak demonstrated that ( -arenediazo methyl ethers do not react with 2-naphthol in dry organic solvents such as dioxan, ethanol, 2-propanol, but only in the presence of water. The reactions are catalyzed by hydrochloric acid (even in the absence of water). Under such conditions almost quantitative yields of azo compounds were obtained. A careful and extensive kinetic investigation of the HCl-catalyzed dediazoniation of substituted benzenediazo methyl ethers, varying the HC1 concentration and the diazo ether/2-naphthol ratio (the latter either absent or in large excess), and comparing the observed rate constants with Hammett s acidity functions for dioxane and ethanol (see Rochester, 1970) indicated the mechanism shown in Schemes 12-8 to 12-10 (DE = diazo methyl ether, D+ = diazonium ion). 

Scheme 11.6 gives some examples of the various substitution reactions of aryl diazonium ions. Entries 1 to 6 are examples of reductive dediazonization. Entry 1 is an older procedure that uses hydrogen abstraction from ethanol for reduction. Entry 2 involves reduction by hypophosphorous acid. Entry 3 illustrates use of copper catalysis in conjunction with hypophosphorous acid. Entries 4 and 5 are DMF-mediated reductions, with ferrous catalysis in the latter case. Entry 6 involves reduction by NaBH4. 

As the anhydride of nitrous and perchloric acids, it is a very powerful oxidant. Pinene explodes sharply acetone and ethanol ignite, then explode ether evolves gas, then explodes after a few s delay. Small amounts of primary aromatic amines-aniline, toluidines, xylidines, mesidine-ignite on contact, while larger amounts exploded dangerously, probably owing to rapid formation of diazonium perchlorates. Urea ignites on stirring with the perchlorate, (probably for a similar reason). 

Heat 85.5 g 3-carbethoxy-2-piperidone and 30 g KOH in 1 L water for twelve hours at 30°. Filter, cool to 0°, add 50 ml 6N HCI. Prepare a fresh solution by diazotizing at 0-5° a mixture of 85 g 3-amino-4-Cl-acetophenone, 250 ml concentrated HCI and 750 ml water with a solution of 36 g Na nitrite in 125 ml water. Add the piperidone solution at 0° to the diazonium salt solution and stir five hours at 10°. Filter, wash precipitate with water to get 80% yield of the hydrazone (1) (recrystallize-95% ethanol). Reflux 62 g (I) in 310 ml 88% formic acid to get 40 g of the carboline (II) (recrystallize-absolute ethanol) (test for activity). Reflux 40 g (II), 100 g KOH, 480 ml ethanol and 360 ml water for eighteen hours and evaporate in vacuum. Add 480 ml water to the residue, cool and adjust pH to 6 with glacial acetic acid. Scratch glass to precipitate filter, wash precipitate with cold water to get 41 g 4-acetyl-2-COOH-7-CI-tryptamine (recrystallize-50% ethanol) which can be alkylated to the active dialkyltryptamine as described elsewhere here. 

As indicated by Komblum in 1944125 the classical method of hydro-de-diazoniation by treating a diazonium salt in boiling acidic ethanol often leads to ethoxy-de-diazoniation. Kornblum replaced that method by dediazoniation in an aqueous solution of hypophos-phorous acid (H3PO2), in some cases in the presence of a catalyst, e.g. 0.05-0.10 mol% Cu. Experimental evidence indicates that aryl radicals are involved. 

The diazonium group in o-carboxybenzenediazonium salts was replaced by hydrogen using sodium borohydride in methanol [593], or ethanol and ultraviolet irradiation [306]. Yields of benzoic acid were 77% and 92.5%, respectively. 

Nitration of hydroxypropiophenone (7-1) followed by conversion of the phenol to its methyl ether by means of methyl iodide provides the intermediate (7-2) the nitro group is then reduced to the corresponding amine (7-3) by catalytic reduction. The newly introduced amine is then replaced by a nitrile group by successive conversion to the diazonium salt by means of nitrous acid followed by treatment with cuprous cyanide (7-4). Reaction with aluminum chloride removes the methyl ether to afford the ortho acylphenol (7-5). This is converted to the chromone (7-6) as above by reaction with benzoyl chloride and sodium benzoate. The nitrile is next hydrolyzed to the carboxylic acid (7-7) by means of sulfuric acid. The acid is then converted to its acid chloride by means of thionyl chloride and that treated with 2-(A -piperidyl)ethanol (7-8). There is thus obtained flavoxate (7-9) [8], a muscle relaxant whose name reflects its flavone nucleus. 

To a mixture of 1 mole of the aromatic amine and 3-4 moles of hydrochloric acid (diluted 1 1 with water) is added, at 0°C, the requisite amount of sodium nitrite dissolved in a minimum amount of water. While maintaining the diazonium salt solution at ice temperatures, 200 ml of a cold saturated solution of zinc chloride is added with occasional stirring. After allowing the mixture to stand for some time in an ice bath, the product is filtered off, washed several times with small portions of ice-cold ethanol followed by anhydrous ether. The salt is then air-dried and finally dried in a vacuum desiccator. In most cases the yield is in the range 90-98 %. 

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