Aromatic diazo compounds

Azo Coupling. The coupling reaction between an aromatic diazo compound and a coupling component is the single most important synthetic route to azo dyes. Of the total dyes manufactured, about 60% are produced by this reaction. Other methods iaclude oxidative coupling, reaction of aryUiydraziae with quiaones, and oxidation of aromatic amines. These methods, however, have limited iadustrial appHcations. 

Polyfluoroalkyl- andperfluoroalkyl-substituted CO and CN multiple bonds as dipolarophiles. Dmzo alkanes are well known to react with carbonyl compounds, usually under very mild conditions, to give oxiranes and ketones The reaction has been interpreted as a nucleophilic attack of the diazo alkane on the carbonyl group to yield diazonium betaines or 1,2,3 oxadiazol 2 ines as reaction intermediates, which generally are too unstable to be isolated Aromatic diazo compounds react readily with partially fluorinated and perfluorinated ketones to give l,3,4-oxadiazol-3-ines m high yield At 25 °C and above, the aryloxa-diazolines lose nitrogen to give epoxides [111]... 

In the 1980 s three monographs were published that cover parts of the present book, namely Quinone Diazides, by Ershov, Nikiforov, and de Jonge (1981), Aromatic Diazo Compounds, by Saunders and Allen (1985), and Williams Nitrosa-tion (1988). The book of Saunders and Allen which is actually the third edition of Saunders original book (1936, 1949), focuses on synthesis and preparative methods. The other two books emphasize rather the mechanistic and physical organic aspects of their subjects. 

Spiroperidol, synthesis 230 (Z)/(ii)-Stereochemistry of aromatic diazo compounds 96 ff. 

Aromatic diazo compounds can be reduced in water via a radical process (Scheme 11.5).108 The reduction mechanism of arenediazo-nium salts by hydroquinone was studied in detail.109 Arenediazonium tetrafluoroborate salts undergo facile electron-transfer reactions with hydroquinone in aqueous phosphate-buffered solution containing the hydrogen donor solvent acetonitrile. Reaction rates are first order in a... 

K H Saunders and R L M Allen, Aromatic diazo compounds, 3rd Edn (London Edward Arnold, 1985). 

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... 

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. 

H. Zollinger, Azo and Diazo Chemistry, Interscience, New York, 1961 S. Patai, ed. The Chemistry of Diazonium and Diazo Groups, John Wiley Sons, New York, 1978, Chapters 8,11, and 14 H. Saunders and R. L. M. Allen, Aromatic Diazo Compounds, 3rd ed., Edward Arnold, London, 1985. 

K. H. Saunders and R. L. M. Allen, Aromatic Diazo Compounds, Edward Arnold, London, 1985. 

K.H. Saunders u. R.L.M. Allen, Aromatic diazo Compounds, 3. Aufl., S. 71 ff., Edward Arnold, London 1985. 

K. H. Saunders, The Aromatic Diazo-Compounds and their Technical Applications. Longmans, Green, New York, 1949. 

The Aromatic Diazo Compounds and Their Technical Applications", Longmans, Green Co, London(1948), 402 pp (Reviewed in Chemistry in Canada 1, 14(1949) 8) W.flP. 

Aromatic Diazo Compounds and Their Technical Application. Title of the book by K.H. Saunders, Arnold, London (1949)... 

For further information see Aromatic Diazo Compounds by Saunders, Chap. 2. 

For a discussion of the diazotization of weakly basic amines see Saunders, "Aromatic Diazo Compounds, Edward Arnold and Co., London, 1936. 

By means of this method, o-nitrophenylarsonic acid was prepared in a yield of 86% as compared with a yield of only 60% by the original Bart process. According to Schmidt, the proportion of by-products, especially the parent hydrocarbon (benzene in the illustration), increases with higher alkalinity. In acid solution the yields are low unless the aromatic diazo compounds contain strongly negative substituents, such as nitro groups, in the ortho and para positions (as in 2,4-dinitrobenzenediazo-nium chloride, for example). 

Bases, Neutral Salts.— As a base it forms salts, in which form the diazo compound is obtained by diazotization, and which though also unstable has been isolated in small quantities and the composition and properties determined. Of the three salts, the sulphate, chloride and nitrate, the first is the most stable and the last is the least stable. They are colorless crystalline neutral compounds soluble in water, difficultly soluble in alcohol and insoluble in ether. After being prepared by the ordinary diazo reaction, with sodium nitrite in cold acid water solution, they may be precipitated in crystalline form by the addition of alcohol and ether. If the diazotization is effected in alcohol solution by means of amyl nitrite or ethyl nitrite the crystals of the diazonium salt separate at once. These salts of diazo benzene all show true salt characteristics, e.g., they lower the freezing point of solutions. The diazo radical, (CeHs—N2—) is thus basic toward strong acids, and the hydroxide, the non-isolated hypothetical diazo benzene, CeHs—N2—OH, is the free base. It may be considered as the simplest aromatic diazo compound and the mother substance of all other members of the class. 

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