Diazonium salicylic acid

Salicylic acid couples with diazonium salts in the expected manner. With diazotized aniline, ie, benzenediazonium chloride, the primary product is 5-phenylazosalicylic acid [3147-53-3] (eq. 7). 

Terminally metallizable dyes (30) are obtained by the interaction of a diazonium salt and a coupling component containing a chelating system, for example salicylic acid, catechol, salicyl-aldoxime or 8-hydroxyquinoline, and their coordination chemistry is typical of these compounds. Such dyes were rarely used as preformed metal complexes but were usually applied to cotton and then converted to their copper complexes on the fibre to improve their fastness to wet treatments. A typical example is the blue dyestuff (31). 

Iodophenol was first obtained as a by-product of the action of iodine on salicylic acid in alkaline solution or by heating iodo-salicylic acid.1 It has also been obtained by the action of iodine on phenol in alkaline solution2 or in the presence of mercuric oxide,3 or by the action of iodine monochloride.4 It is best prepared by the diazotization of -aminophenol and replacement of the diazonium group by iodine 5 although it has also been obtained from />-iodoaniline by diazotization and replacement of the diazonium group by hydroxyl.6... 

Copper complexes (152) of o-hydroxy-o -(p-aminoethylamino)diarylazo compounds have been prepared ° by the reaction of the corresponding o-chloro-o -hydroxydiarylazo compounds and ethylenediamine in the presence of copper(II) ions (c/. Section 58.2.3. l(iii)(c)). Dyestuffs of this type have been evaluated on nylon but are reported to have very poor fastness properties. Copper complexes such as (153) have been preparedby similar methods. Other, related tetradentate diarylazo compounds, e.g. (154), (155) and (156), are obtained by the reaction of a suitable diazonium salt with the appropriate diarylamine. Chromium(III) and cobalt(III) complexes of dyes of this type, in which the coordination sphere of the metal is completed by a colourless bidentate ligand such as ethylenediamine, salicylic acid or 8-hydroxyquinoline, are reported to have dyeing properties on wool similar to those of the comparably charged 2 1 complexes derived from tri-... 

It may be prepared first by diazotising N -2-pyridyl-sulfanilamide at 0-10°C and secondly by coupling the resulting diazonium salt with salicylic acid. 

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