Coupling anilines

The most important reaction of the diazonium salts is the condensation with phenols or aromatic amines to form the intensely coloured azo compounds. The phenol or amine is called the secondary component, and the process of coupling with a diazonium salt is the basis of manufacture of all the azo dyestuffs. The entering azo group goes into the p-position of the benzene ring if this is free, otherwise it takes up the o-position, e.g. diazotized aniline coupled with phenol gives benzeneazophenol. When only half a molecular proportion of nitrous acid is used in the diazotization of an aromatic amine a diazo-amino compound is formed. 

Its production was 621 t and the average price 0.75/kg in 1987. Direct YeUow 44 (64) is prepared by phosgenation of an equimolar mixture of metanilic acid coupled to o-anisidinomethanesulfonic acid (with subsequent hydrolysis of the methanesulfonic acid group) and nitro aniline coupled to sahcychc acid (with subsequent reduction of the nitro group). 

Other commercially important direct oranges iaclude Direct Orange 26 (66) (R = H) (2 mol aniline coupled to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid), and Direct Orange 72 (67) which is obtained by phosgenatiag two moles of 7-amiQO-l,3-naphthalenedisulfonic acid coupled to cresidine [120-71 -8]. 

Fig. 5. Direct red dyes, (a) Direct Red 81 described ia text (68) (b) Direct Red 2 (o-toLidiae coupled to two moles of naphthionic acid) (69) (c) Direct Red 23 (aniline coupled to 6,6 -ureylenebis-l-naplitliol-3-sulfonic acid with a second coupling with j aminoacetanilide) (70) and Direct Red 80 (2 mol 6-amino-3,4 -azobenzenedisulfonic acid coupled twice to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid) (73). Direct Red 24 (4-aniino-y -toluenesulfonic acid coupled under acidic conditions to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid followed by an alkaline coupling of o-anisidine) (71) (d) Direct Red 72 (Broenner s acid, ie, 6-artiino-2-naphthalenesulfonic acid coupled under acidic conditions to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid followed by an...

Basic Orange 1 (130) (aniline coupled to 2,4-diamiaotoluene) and Basic Orange 2 (22) (aniline coupled to y -phenylenediamiae) are examples of amine salt type cationic azo dyes. The cation is formed by protonation under acidic conditions. Under neutral or alkaline conditions, these dyes behave more like disperse dyes. In 1988 the U.S. production of Cl Basic Orange 2 amounted to 132 tons. 

A synthesis of glaziovine [259] via oxidative phenol-aniline coupling involves con-trapolarizing activation of the aromatic carbon para to the amino group. 

The qualitative application is illustrated by the approximate location of E°w for the azobenzene/aniline couple on redox ladders constructed by Schwarzenbach et al. (e.g., Figure K.3 in Reference 120). The estimate, around -0.1 V vs. NEIE, comes from electrochemical studies that report non-Nemstian dependence of E1/2 on pEI and additional evidence for the non-reversibility of this reaction (8,121). 

Amino-5-nitro-2,l-benzisothiazole is manufactured by thiolysis of 2-amino-5-nitrobenzonitrile and oxidative ring closure. With aniline coupling components, shades from navy to greenish blue are obtainable (e.g., 28 and 29). 

Dyeing is normally readily accomplished in aqueous solution, often in the presence of a fixing agent, or mordant. This is ideal for cotton, silk and wool, but not for certain synthetic fibers, such as nylon and polyester. The latter are plastic in nature, and require disperse dyes. Here the dyeing process involves heating the fiber in an aqueous dispersion of a water-insoluble dye. A solid solution is formed in the fiber. In order to penetrate synthetic fibers, a small dye molecule is required, for which simple water-insoluble mono-azo dyes are ideal. Apart from yellow dyes (where phenolic components are common), these are usually based on /V,/V-dialkylated aniline coupling components that permit a wide range of shades to be obtained. 

In 1955, Mester showed that diazotized aniline couples with D-arabino-hexulose phenylosazone (43) in alcoholic potassium hydroxide to give an... 

Fig. 10.3-22 Secondary bioconjugation using ami notyrosines, (a) Following reduction of azotyrosine 71 using dithionite, the aminotyrosine product 72 couples rapidly with N-acylphenylene diamine 73 under oxidative conditions. Following the formation of adduct 75. an additional oxidation step occurs to yield stable product 76. Similar to the aniline coupling strategy described above, this reaction is believed to...

Their synthesis began with protected dipeptide 220, reaction of which with o-iodoaniline and (V-iodosuccinimide in the absence of an acid-scavenger afforded the indole-aniline coupled product 221 as a single diastereomer. Larock annulation of 221 with tripeptide 222 obtained in two steps from serine-derived 223 through... 

Determination of amine antioxidants in polyalkenes and other polymers, p-nitro aniline coupling - spectrophotometric procedure... 

Nickel azo yellow Nickel complexes of p-chlor aniline coupled with 2-4 dihydroxyquinoline... 

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