Diazo compounds phenols

Reaction with alcohols is general for diazo compounds, but it is most often performed with diazomethane to produce methyl ethers or with diazo ketones to produce ot-keto ethers, since these kinds of diazo compounds are most readily available. With diazomethane the method is expensive and requires great caution. It is used chiefly to methylate alcohols and phenols that are expensive or available in small amounts, since the conditions are mild and high yields are obtained. Hydroxy compounds react better as their acidity increases ordinary alcohols do not react at... 

Alkylation of alcohols or phenols with diazo compounds... 

The use of copper as a catalyst in carbenoid transfer has its roots in the Amdt-Eistert reaction, Eq. 1 (3). Although the original 1935 paper describes the Wolff rearrangement of a-diazo ketones to homologous carboxylic acids using silver, the authors mention that copper may be substituted in this reaction. In 1952, Yates (4) demonstrated that copper bronze induces insertion of diazo compounds into the X-H bond of alcohols, amines, and phenols without rearrangement, Eq. 2. Yates proposal of a distinct metal carbenoid intermediate formed the basis of the currently accepted mechanistic construct for the cyclopropanation reaction using diazo compounds. 

Nor can there be any question of real tautomerism in the case of phenol. In its chemical properties phenol resembles the aliphatic enols in all respects. We need only recall the agreement in the acid character, the production of colour with ferric chloride, and the reactions with halogens, nitrous acid, and aromatic diazo-compounds (coupling), caused by the activity of the double bond and proceeding in the same way in phenols and aliphatic enols. The enol nature of phenol provides valuable support for the conception of the constitution of benzene as expressed in the Kekule-Thiele formula, since it is an expression of the tendency of the ring to maintain the aromatic state of lowest energy. In this connexion the hypothetical keto-form of phenol (A)—not yet obtained—would be of interest in comparison with... 

DIAZOTISATION OF ANILINE. PHENOL, IODOBENZENE AND BENZENE PROM ANILINE. ISOMERISM OF THE DIAZO-COMPOUNDS... 

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. 

Even the doubly unsaturated hydrocarbons, such as butadiene, can be coupled with suitable diazo-compounds. Finally, not only phenols, but also phenol ethers, such as anisole, are capable of coupling (K. H. Meyer1). 

One such process involves the thermal decomposition of a diazo compound to give an acid that cross-links phenol formaldehyde resins upon heating, similar to the conventional UV initiated plates used in the industry (Figure 4.3), but other sensitisation methods are also used (see section 4.5). It is also possible to produce plates in a dry resin process by ablation or phase change methods. 

Reaction between alkoxides or arox-ides and alkyl halides (Williamson) 0-14 Reaction between alkoxides or arox-ides and inorganic esters 0-15 Alkylation of alcohols or phenols with diazo compounds 0-16 Dehydration of alcohols 0-17 Transetherification 0-19 Alkylation of alcohols with onium salts... 

OXYAZO COMPOUNDS. Compounds of the type RN=NC6H4OH, containing both the azo group — N=N—, and a hydroxyl group —OH, both attached to carbon atoms in the same ring. These compounds are commonly produced by ihe action of diazo compounds upon phenols in alkaline solution. They constitute a class of dyes. See Dyes. 

The reaction of diazo cation with phenolate yielding the azo dye may proceed through the formation of the diazo ether. Kekule came to this conclusion in 1870. Zollinger (1958), considering this conclusion, proposed and explained the mechanism by which the diazo ethers convert into the C-diazo compounds, that is, into the hydroxyazo dyes. The diazo ether preliminarily dissociates into the phenolate ion and the diazonium ion i.e., a two-stage intermolecular reaction takes place. The CIDNP effect suggests that the diazo ether may reversibly convert into the radical pair ... 

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... 

During the nitration of aromatic compounds a certain amount of diazo compounds as by-products can also be formed. This for the first time was described by Weselsky as early as in 1875 [84] in the case of nitration of phenols with nitrogen dioxide and of nitration of aromatic hydrocarbons by Titov and Baryshnikova [85], Titov [39] explained the reaction as the result of reaction of nitroso compounds with NO ... 

The diazo compound (I) can next be transformed into the phenol (II) (see also [18a]). 

Phenols are particularly suited as addition substances for fixing the diazo-bodies. Experiments have shown that the coupling of the diazo-compound with the acid component takes... 

There are also important examples of phenolic compounds that do not couple (see Fig. 13.88). In these examples, the required coupling positions are blocked, the ring is too deactivated, or the compounds undergo oxidation in the presence of the diazo compound. 

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... 

Phenol derivatives, in which the hydroxyl group has been converted to an ether or an ester, are incapable of coupling under normal conditions. Similarly, acyl derivatives of amines (benzoyl, acetyl, etc.) are unreactive. The sulfonyl derivatives of primary amines, such as p-tolu-enesulfonanilide, are exceptions these compounds are soluble in caustic alkali and behave as phenols toward diazo compounds. 

Phenols and Enolizable Keto Compounds. These compounds are coupled in alkaline (soda) solution as a rule. If the coupler is a sulfonic or carboxylic acid, or is soluble in water (e.g., resorcinol), it is dissolved directly in the required amount of soda solution. In other cases, the coupler is dissolved in the equivalent amount of dilute sodium hydroxide solution and the recaustic soda for complete solution in such cases, no more is used than is absolutely required. (Solution of the 2-hydroxyl-3-naphthoic acid arylides is greatly assisted by the addition of alcohol. In many cases, no other method of dissolving the coupler is known.) An unnecessarily large excess of alkali is to be avoided, except in special cases, since such an excess rapidly decomposes the diazo compound. It is desirable to use that amount of soda which will be converted to bicarbonate by the acid of... 

Alkaline coupling is carried out, as in the case of phenols, with the addition of soda. If the diazo compound is sensitive to alkali, it is desirable to add only a small portion of the soda at the start to dissolve the coupler and the remainder simultaneously with the diazo solution. In this way, the solution is kept only weakly alkaline throughout the course of the reaction. The addition of the diazo solution should be made slowly and with vigorous stirring. 

The following types of compounds undergo coupling reactions with diazo compounds (a) Phenols, (b) Enolizable keto compounds of an aliphatic character, having a reactive methylene group which may be part of an open chain or a ring system, either homocyclic or heterocyclic. This group of compounds may be represented by the formula ... 

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