Ethanol diazonium compounds

At the same time, the ethanol reduces some of the diazonium compound to benzene, the ethanol itself being oxidised to acetaldehyde, the odour... 

In absolute ethanol solution, the ethyl ether and the corresponding hydrocarbon are formed, the latter by reduction of the diazonium compound by the ethanol, which is itself oxidised to acetaldehyde ... 

A deamination procedure for which general application is claimed has been described by Hodgson and Madden.6 An aqueous solution of the diazotized amine is treated with the molar quantity of naphthalene-1,5-, disulfonic acid or 2-naphthol-l-sulfonic acid, whereupon the stabilized diazonium compound is precipitated. In most cases the stabilized diazo salts require slight variations in technique for their preparation in optimum yield. "The dry salt is reduced at room temperature in ethanol containing zinc or copper. Overall yields of the order of 90% are reported however, the purity of the product is not specified. 

Historically, the first replacement of a diazonium group by hydrogen was accomplished with alcohols.Of these, ethanol is the best, while methanol tends to convert diazonium compounds to aryl methyl ethers. " The hydrogen atom replacing the diazonium group comes from the alcohol, which is converted to the corresponding aldehyde. The reaction is catalyzed by UV irradiation " and by copper(I) oxide. "" " Copper(I) oxide alone reduces the diazonium compounds, but in poor yields. " The reaction can be carried out in aqueous media " or in organic solvents. ""- " ... 

Indazole has been obtained in a variety of ways which are of no preparative value. The elimination of the amino group from aminoindazoles, first utilized by Witt, by the action of ethanol or sodium stannite on the diazonium compounds appears to be the only other useful procedure. 

Coupling reactions of diazonium compounds methanol, ethanol, glacial acetic acid, pyridine... 

The high reactivity of the 5-position in 1.3-selenazoles toward electrophilic substitution was also observed on azocoupling. By reacting molar quantities of an aqueous solution of a diazonium salt with an ethanolic solution of a 2-arylamino selenazole. for example, the corresponding 2-arylamino-5 azoselenazoles are formed in a smooth reaction (100). They deposit from the deeply colored solution and form intenselv red-colored compounds after their recrystallization from a suitable solvent (Scheme 36l. 

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). 

The pyrazolo[3,4-( ][l,2,3,4]tetrazine derivative 49 has been reported to be formed by treatment of the hydrochloride salt of the amine 48 with sodium nitrite in aqueous ethanol at room temperature. Only a single example was described. Compound 49 was obtained as red crystals (m.p. >300°C). The product is presumed to form from the diazonium cation 50 which cyclizes via the hydrazone tautomer 51 (Scheme 2) <1998MI11>. 

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... 

Dichloro-3-nitropyridine was reacted with N-ethoxycarbonylpiperazine to give 6-chloro-2-(4-ethoxycarbonyl-l-piperazinyl)-3-nitropyridine. The product, without purification, was heated with ethanolic ammonia in a sealed tube at 120°-125°C to give 6-amino-2-(4-ethoxycarbonyl-l-piperazinyl)-3-nitropyridine (mp 132°-134°C), which was treated with acetic anhydride in acetic acid to give 6-acetylamino-2-(4-ethoxycarbonyl-l-piperazinyl)-3-nitropyridine (mp 168°-169°C). This compound was catalytically hydrogenated in the presence of 5% palladium-carbon in acetic acid to yield 3-amino-6-acetylamino-2-(4-ethoxycarbonyl-l-piperazinyl)pyridine. The obtained 3-amino derivative, without further purification, was dissolved in a mixture of ethanol and 42% tetrafluoroboric acid, and to this solution was added a solution of isoamyl nitrite in ethanol at below 0°C with stirring 20 minutes later, ether was added to the solution. The resulting precipitate was collected by filtration and washed with a mixture of methanol and ether and then with chloroform to yield 6-acetylamino-2-(4-ethoxycarbonyl-l-piperazinyl)-3-pyridine diazonium tetrafluoroborate mp 117°-117.5°C (dec.). 

The 4-aminopyridine derivative 92, prepared from the reaction of ethyl benzoylacetate and malononitrile dimer 91, undergoes the coupling reaction with aromatic diazonium salts to afford azo derivatives such as 93. Under refluxing conditions in ethanolic sodium hydroxide, these azo compounds cyclize to pyrido[3,2-f]pyridazines and pyrido[3,2-r]-pyridazino[2, 3 - ]quinazolines (Scheme 15) <2005AP329>. 

A suspension of 2.10 g. of the freshly prepared diazonium salt and 50 ml. of ethanol is stirred in a 200-ml. Erlenmeyer flask and cooled to 0°C. while a solution of 4.7 g. of fcww-chloro-hydrido-bis(triethylphosphine) platinum (II) in 25 ml. of ethanol is added over a period of 10 minutes. The mixture becomes yellow immediately and is stirred at 0°C. for 10 minutes. At this point, yellow crystals of the aryldiimide complex usually separate. The mixture is filtered, and the filtrate is cooled to —78°C. to give a second crop of the diimide complex. Occasionally crystallization does not occur immediately. In this situation, the mixture is cooled to — 78°C. directly, and the crystals which form are filtered and washed with ether. In either case the total yield is about 4.9-5.4 g. (72-78%). (The checkers reported an 87% yield with a melting point of 105-108°C. with decomposition.) The purity of this material is adequate for most preparatory purposes. Further purification may be accomplished by conversion to the arylazoplatinum compound (Sec. D) followed by reprotonation with concentrated aqueous fluoroboric acid, HBF4. 

---