Sulfuric Acid → 5,6-difluoro-2,3-dihydro-1H-indole-2,3-dione
Reaction equation
[F:1][C:2]1[CH:3]=[C:4]([NH:9][C:10](=[O:14])[CH:11]=NO)[CH:5]=[CH:6][C:7]=1[F:8].S(=O)(=O)(O)[OH:16]>>[F:8][C:7]1[CH:6]=[C:5]2[C:4](=[CH:3][C:2]=1[F:1])[NH:9][C:10](=[O:14])[C:11]2=[O:16]Participants
Procedure
In accordance with the above reaction scheme, an aqueous solution of 3,4-difluoroaniline (I) and hydroxylamine hydrochloride containing hydrochloric acid is reacted with an aqueous solution of chloral hydrate and sodium sulfate at the reflux, then filtered while hot, giving N-(3,4-difluorophenyl)-2-(hydroxyimino)-acetamide (II). The compound (II) is reacted with concentrated sulfuric acid with heat, then added to cracked ice, giving 5,6-difluoro-1H-indole-2,3-dione (III). A basic aqueous solution of compound (III) is treated with hydrogen peroxide and heat, then cooled and acidified, giving 2-amino-4,5-difluorobenzoic acid (IV). The compound (IV) is added to a mixture of anhydrous copper(II) chloride, t-butyl nitrite and anhydrous acetonitrile at 0°-5° C., then added to a dilute mineral acid, giving 2-chloro-4,5-difluorobenzoic acid (V).
Workup
- temperaturewith heat
- additionadded
Sources & evidence
- ORD record
- ord-2b5ca1785adf4f11a1998e20cdd8ab41
- Source dataset
- uspto-grants-1989_05
- Patent number
- US04833270
Reaction notes
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