1 -Amino-2-hydroxy-naphthalene—

Heterocycles are known to have O—S, S—N, and O—N bonds. The cyclization of peri-hydroxy and peri-amino-substituted naphthalene sulfonic acids gives rise to 1,8-naphthosultone 246 and 1,8-naphthosultam 247, respectively (33MI2 63MI1). On gas phase photolysis of naphtho[/>c]-... 

A particularly important class of coupling components are the aminohydroxy-naphthalenesulfonic acids. Appropriate variation of the disazo component permits the development of shades ranging from orange to black. Orange and scarlet are achieved with I-acid (6-amino-l-hydroxy-naphthalene-3-sulfonic acid) and y-acid (7-amino-1-hydroxynaphthaIcne-3-sulfonic acid), whereas H-acid (8-amino-l-hydroxynaphthalene-3,6-disulfonic acid) and K-acid (8-amino-l-hydroxy-naphthalene-3,5-disulfonic acid) derivatives are useful for red to bluish-red hues. Extremely lightfast red shades are also accessible with disazo dyes ( brown dyes ). For chemical structures see Section 3.1.5). 

Alkaline glucose converts the diazonium salts of l-amino-2-hydroxy-naphthalene-4-sulfonic acid and its halogen, nitro, carboxyl, or sulfonic acid derivatives into the corresponding 2-hydroxynaphthalene-4-sul-fonic acids.126 According to this patent, the yields are nearly quantitative. 

A single-step process for preparing oxazine derivatives via the condensation of an a-hydroxyaldehyde and o -amino-/3-hydroxy naphthalene (3) is illustrated in Eq. 2 ... 

The nitro substitution products of naphthalene are easily prepared by the action of nitric acid on the hydrocarbon. By such direct nitration the product obtained is alpha-nitro naphthalene. This is proven by the following series of reactions. Nitro-naphfhalene by reduction yields amino naphthalene, naphthylamine, which by the diazo reaction yields hydroxy naphthalene, naphthol. Now the naphthol so obtained is identical with the one resulting from the phenyl vinyl acetic acid synthesis (p. 768) and this must be the alpha compound. 

The position of coupling reactions in amino and hydroxy naphthalene compounds is more involved. If the amino or hydroxy group is in the /3-position (2-position), then coupling takes place in the a-position (adjacent). If the amino or hydroxyl group is in the a-position, then coupling takes place in the 4- or 8-position. Generally speaking, hydroxy compounds couple more readily than amino compounds. 

Avoidance of Wastewater and Residues in the Production of H Acid (l-Amino-8-hydroxy-naphthalene-3 6-disulfonic acid)... 

Acetylamino-2-sulfophenylazo)-6-amino-4-hydroxy naphthalene-2-sulfonic acid, disodium salt. See Acid red 37... 

H acid 1 -amino-8-hydroxy-naphthalene-3,6-disulphonic acid azo... 

Amino-3-hydroxy-7-nitro-l-naphthalene-sulfonic acid [6259-63-8]... 

The Chemicaly3.bstractIndexis 2,7-naphthalene-disulfonic acid, 4-amino-5-hydroxy-3-[[4 -[(4-hydroxyphenyl)azo] [l,l -biphenyl]-4-yl]azo]-6-(phenylazo)-, disodium salt. 

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 ... 

In naphthalene derivatives with an amino or a hydroxy group and no other substituents the ratio of 4- to 2-coupling, k4/k2, is not so large, only about 20-40. 

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. 

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