Claims
- 1. A process for the preparation of 6-hydroxynaphthalene-1-carboxylic acid comprising the following steps:
- (a) amidoalkylating naphthalene-2-sulphonic acid in an acid medium with an amidoalkylating agent of the formula ##STR3## in which R.sub.1 is acyl,
- R.sub.2 is hydrogen or acyl, or
- R.sub.1 and R.sub.2 together form a diacyl radical,
- X is halogen, and R.sub.3 O-group or an (R.sub.1)(R.sub.2)N-group and
- R.sub.3 is hydrogen, acyl or an (R.sub.1)(R.sub.2)N--CH.sub.2 -- group;
- (b) splitting off the acyl radical R.sub.1 or the acyl radicals R.sub.1 and R.sub.2 from the amidoalkylation product by acid or alkaline hydrolysis;
- (c) oxidizing the 1-aminomethyl-naphthalene-6-sulfonic acid obtained in step (b) to form a 1-carboxynaphthalene-6-sulphonic acid; and
- (d) converting the 1-carboxynaphthalene-6-sulphonic acid by alkali fusion into the 6-hydroxynaphthalene-1-carboxylic acid.
- 2. A process of claim 1 wherein in step (a) the naphthalene-2-sulphonic acid is used in the form of the pure acid, in the form of its salts or in the form of a sulphonation mixture obtained when 1 mol of naphthalene is reacted with 0.8-2.0 mol of 98-100% strength sulphuric acid at a temperature from 100.degree.-170.degree. C.
- 3. A process of claim 1 wherein the amidoalkylation reaction of step (a) is carried out in 60-100% strength by weight sulphuric acid.
- 4. A process of claim 1 wherein in the formula of the amidoalkylating agent
- R.sub.1 is a C.sub.1 -C.sub.4 -alkanoyl, a C.sub.1 -C.sub.4 -alkenoyl,
- C.sub.1 -C.sub.4 -alkanoyl substituted by chlorine,
- C.sub.1 -C.sub.4 -alkenoyl substituted by chlorine, or the radical of an aromatic carboxylic acid,
- R.sub.2 is hydrogen or
- R.sub.1 and R.sub.2 together form the diacyl radical of a saturated or unsaturated aliphatic dicarboxylic acid or of an aromatic o-dicarboxylic acid and
- X is chlorine, hydroxy or a R.sub.1 NH group.
- 5. A process of claim 1 wherein in step (c) the 1-aminomethylnaphthalene-6-sulphonic acid is oxidized directly by means of dichromate salts or chromate salts in a neutral or alkaline medium or is first converted into 1-formylnaphthalene-6-sulphonic acid by reaction with hexamethylenetetramine and the 1-formyl-naphthalene-6-sulphonic acid is then oxidized to yield 1-carboxynaphthalene-6-sulphonic acid.
- 6. A process of claim 1 wherein after hydrolysis of the amidoalkylation product, the 1-aminomethylnaphthalene-6-sulphonic acid is separated off at a pH.ltoreq.6.5.
Priority Claims (1)
Number |
Date |
Country |
Kind |
3637138 |
Oct 1986 |
DEX |
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Parent Case Info
This is a division of application Ser. No. 108,525, filed Oct. 15, 1987 now U.S. Pat. No. 4,795,596.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
1785955 |
Herzberg et al. |
Dec 1930 |
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3330862 |
Borkowski |
Jul 1967 |
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Divisions (1)
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Number |
Date |
Country |
Parent |
108525 |
Oct 1987 |
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