Benzene derivatives amino groups

The chemical properties and reactions of the aminophenols and their derivatives are to be found in detail in many standard chemical texts (25). The acidity of the hydroxyl function is depressed by the presence of an amino group on the benzene ring this phenomenon is most pronounced with 4-aminophenol. 

The relative ease of preparation of condensed thiazole derivatives is a consequence of facile thiazole ring closure, and therefore also benzothiazole amines with an amino group on the benzene ring (except for the weakly regioselective nitration of benzothiazoles) are very easily accessible and useful substrates for the Gould-Jacobs reaction. 

The term coupling component referred originally to aromatic hydrocarbons, particularly benzene and naphthalene derivatives, which were required to have a hydroxy or an amino group as a substituent (sometimes, but not necessarily, accompanied by other substituents such as sulfonic acid groups). The presence of the hydroxy or amino group increases the C-nucleophilicity of the coupling component. In most cases this is a necessary requirement because the diazo components are relatively weak electrophiles. If the coupling component is phenol or a derivative of phenol ... 

This reaction [65-67] is only rarely encountered in the benzene series but is extremely useful for appropriate derivatives of naphthalene, where the mechanism of the reaction has been investigated extensively. The reaction allows a hydroxy group to be exchanged for an amino group or vice versa. When a hydroxy group is to be converted into an amino group, the naphthol is heated under pressure with ammonium bisulphite (often produced in situ by introduction of ammonia liquor and sulphur dioxide into a sealed autoclave) at a temperature of 100-150 °C the naphthol is thereby converted into the corresponding naphthylamine. The mechanism of the reaction is outlined in Scheme 4.22. 

In the cyclocondensation of diethyl acetylmalonate and 4-alkylamino-1,5-benzodiazepines (1411) in benzene in the presence of acetic acid and piperidine, the addition of acetylmalonate at the side-chain double bond of 1411 took place first. The amino group at position 4 was involved only in the second step of the reaction sequence to give tricyclic derivatives (1412) in 49-77% yields (85FES391). 

Aniline is a simple aromatic compound composed of an amino group attached to a benzene ring. Other aromatic amines are aniline derivatives. Some examples of aromatic amines are shown in Figure 13-2. 

Sulfasalazine Sulfasalazine, 5-[p-[(4,6-dimethyl-2-pyridinyl)sulfamoyl]phenylazo]sali-cylic acid (33.1.22), is a derivative of sulfapyridine drug described above and one of the few sulfanilamides in which the free amino group in the benzene ring is modified, and it is synthesized by an azo-coupling reaction of a diazo salt, which is synthesized by reacting sulfapyridine (33.1.21) with nitrous acid and salicylic acid alkaline media [24,25]. 

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