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US 5,196,573 AGranted
Process for the preparation of sulfonated anthranilic acids
AssigneeBASF SE
InventorsManfred Patsch, Klaus Pandl, Jacques Dupuis, Helmut Hagen
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Abstract
A process for the preparation of 4-sulfonated anthranilic acids by sulfonation of ortho-nitrotoluenes with chlorosulfonic acid or oleum followed by oxidation of the methyl group and, finally, reduction of the nitro group.
Claims3
A process tor the preparation of an anthranilic acid of formula I ##STR5## in which X.sup.1 and X.sup.2 are the same or different and independently denote hydrogen, halogen or amino, comprising
- a) treating in a first stage a nitrotoluene of formula II ##STR6## in which Y.sup.1 and Y.sup.2 are the same or different and independently denote hydrogen, halogen or nitro, with chlorosulfonic acid or from 10 to 75% w/w oleum at a temperature of from 40.degree. to 150.degree. C. and,
- b) in a second stage, diluting in situ the resulting reaction mixture containing the nitrotoluenesulfonic acid of formula III ##STR7## in which Y.sup.1 and Y.sup.2 have the meanings stated above, with water and treating the mixture with nitric acid in the presence of V.sub.2 O.sub.5 at from 130.degree. to 170.degree. C. and,
- c) in a third stage, reducing the resulting nitrobenzoic acid of formula IV ##STR8## ` in which Y.sup.1 and Y.sup.2 have the meanings stated above.
Dependencies are inferred from the claim text.