Phenols from diazo compounds

From Diazo Compounds.—Another synthesis of phenols that is often used in the laboratory, especially if the desired sulphonic acid is not... 

An important support for this theory is the circumstance that the bodies formed by the action of aromatic hydrazines on quinones are identical with those obtained from phenols and diazo-compounds. Phenylhydrazine, for example, reacts with a-naphthoquinone, producing the same compound which is formed by combination of a-naphthol with diazobenzene [3j. The first method of formation renders the formula... 

That a close relationship exists between azo-compounds and hydrazides is seen from the fact that certain oxyazo-compounds obtained from diazo-compounds and phenols are identical with the hydrazides of certain quinones. Indeed all coloured hydrazides show a great similarity to the azo-compounds, and probably belong to this class. Both classes of compounds, for example, behave similarly on reduction. The hydrazine group, like the azo-group, is split, yielding two amido-groups, one of which remains in combination with the phenyl group, the other with the carbon atom. 

In its simplest form this reaction, by means of which the extremely numerous technical azo-dyes are manufactured, consists in condensation of aromatic diazo-compounds with phenols or aromatic amines to form azo-compounds. From the labile diazo-system the very stable azo-complex is produced. The azo-dyes, therefore, are, without exception, derivatives of azobenzene or else of azonaphthalene, etc. 

It is reported that alkaline sodium hydrotulfite (Na2S204) is effective -in converting certain diazo compounds to the hydrocarbons,119 a statement supported solely by reference to the work of Grandmougin.130 Actually he obtained only a small yield of benzene from benzenediazonium salts but suggested that on further study the process might prove to be useful. Upon reduction with hydrosulfite, the diazo oxide XXIV is converted to the phenol XXV in 95% yield (crude product.)131... 

The 3(5)-diazopyrazoles are noticeably less stable than the 4-diazo compounds.31 Both are light-sensitive and both couple with phenols in organic solvents. The dyes so obtained form lakes with transition metal ions (cf. dyes from 2-diazopyrroles above, e.g., 40).13 The coupled product from 3-diazopyrazole and /9-naphthol is not in fact the simple azo dye but a condensation product derived from it.7... 

Salts of primary aromatic amines react with nitrous acid to produce diazonium salts. The reaction is usually performed by adding a cold solution of sodium nitrite to a cold solution of the arylamine in aqueous mineral acid. The end point of the reaction is conveniently determined by the detection of excess nitrous acid with potassium iodide-starch paper. Sulfamic acid has long been used both in industry and in the laboratory to remove excess nitrous acid. It has been found to react with the more active diazo compounds. In most cases, high temperatures are avoided to prevent the formation of phenols and the decomposition of the unstable nitrous acid. An excess of mineral acid is necessary to prevent coupling between the diazonium salt and unreacted amine (cf. method 494). If the amine salt is somewhat insoluble, a fine crystalline form, which is produced by rapid crystallization from a warm aqueous solution, may be employed. ... 

The melt is extracted with water, and the residue dissolved in hot alcohol, and ammonia gas passed into the solution. The precipitate which forms is boiled with acetic acid or hydrochloric acid [44, 48, 49]. Aurin is also formed by condensation of phenol with formic acid and zinc chloride [45], by boiling the diazo-compound from pararosaniline with water [12], by heating dioxybenzophenone chloride with phenol [46], and by action of salicylic aldehyde on phenol in presence of concentrated sulphuric acid [47]. 

Several of these acids are known, but only one, the caustic soda on /8-naphthylaminedisulphonic acid G (from /S-naphtholdisulphonic acid and ammonia) at about 260°. It may be diazotised, and reacts with diazo-compounds to produce azo-colours, which may be diazotised and combined on the fibre with other amines and phenols. (See below, under Tetrazo-colours.)... 

A variety of monoanionic N,0-chelate complexes have been described. These include ligands derived from phenolic diazo compounds, a variety of Schiff-base derivatives, aldehyde hydrazone ligands,762 thiazolidin-4-ones,763,764 and salicylideneamino-3,5-dimercapto-l,2,4-tri-azoles.760 Similarly, the complexes Ti(OPr )4 (NHC(0)R) (R = Me, Ph, NC5H4, n 4) are thought to be coordinated via the carbonyl group of the amide functional group.765... 

From this equation it is evident that by reduction, the amine which was diazotised—in the above case sulphanilic add—may be obtained again on the one hand, on the other an amido-group is introduced into the second component. If the constitution of this second product can be determined, then the constitution of the azo dyes is also determined. It may be stated as a general rule that, when a diazo-compound combines with an amine or phenol, the hydrogen atom in the para position to the amido- or hydroxyl-group is always substituted. In accordance with this, in the above case, p-amidodimethyl aniline ought to be obtained on reduction. If the para position is already occupied, then, the o-hydrogen atom Mites With the acid radical-... 

The aqueous distillate contains the quinoline formed in the reaction and a small amount of aniline. In order to separate the latter, advantage is taken of the fact that aniline is converted into a diazo compound by nitrous acid, whereas quinoline, being a tertiary amine, is not affected by this reagent. When the aqueous solution containing the diazo compound is heated, the latter is converted into a phenol. Quinoline can be readily separated from phenol by distillation with steam from an alkaline solution, in which the phenol is present as the sodium salt and is, therefore, non-volatile. To effect this separation treat the aqueous distillate as follows Add to the distillate 10 cc. of concentrated sulphuric acid. There should be a small excess of acid... 

Excess diazomethane has been used to convert phenols to methyl ethers in the presence or absence of acids . Employment of transition metal derivatives, typically Rh2(OAc)4 and recently CHsReOs , allows one to react functionalized diazo compounds in an intramolecular or intermolecular 0-aUtylation (equation 13). The stability of diazo compounds derived from active methylene compounds toward OH insertion was compared... 

Through researches in aromatic chemistry it was not tong before synthetic phenol became available. Prior to work by Griess on aromatic diazo compounds published in 1860, Hunt (ref.1) had in 1849 obtained phenol from a diazonium salt produced by the reaction of aniline hydrochloride and siver nitrite. F.A. Kekule, (1829-1896), Fig.3, in 1867 (ref.2) described the recently completed sulphonation of benzene and fusion of the sulphonic acid with alkali as a new... 

Salicylic acid can be prepared by the oxidation of o-hydroxy-benzyl alcohol, by the fusion of o-toluenesulphonic acid and other ortho acids with potassium hydroxide, by heating with water the diazo compound formed from anthranilic acid. It can be obtained with a favorable yield when o-cresol is fused with potassium hydroxide and lead peroxide the latter compound oxidizes the methyl radical to carboxyl. A mixture of o- and p-hydroxybenzoic acid is obtained from phenol by the Tiemann-Reimer synthesis (507). 

The acid is an unstable white powder which soon darkens even m the dry state. When heated it decomposes without melting, and m water and the usual solvents it is insoluble, but it dissolves readily m alkali, ammonium hydroxide and acids. A sodium salt may be precipitated from the aqueous alkali solution by the addition of alcohol. The ammo-group is diazotisable and the diazo-compound couples with alkaline resorcinol solution and other phenols. 

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