Sulfuric Acid → 4,6-Difluoro-1H-indole-2,3-dione

Temperature

120 °C

A solution of 3,5-difluoroaniline (10.8 g) in a mixture of 12N aqueous hydrochloric acid solution (7.5 ml) and water (90 ml) was added to a stirred mixture of chloral hydrate (9.2 ml), sodium sulphate decahydrate (240 g) and water (210 ml). A solution of hydroxylamine hydrochloride (18.6 g) in water (90 ml) was then added and the mixture was heated to 120° C. for 45 minutes. The mixture was cooled to ambient temperature and the precipitate was isolated and dried under vacuum. The material so obtained was added to concentrated sulphuric acid (60 ml) and the mixture was stirred and heated to 80–90° C. for 10 minutes. The mixture was cooled to ambient temperature and poured onto a 1:1 mixture of ice and water (600 ml). The precipitate was isolated, washed with water and dried under vacuum at 50° C. to give 4,6-difluoro-2,3-dioxoindoline (14 g); NMR Spectrum: (DMSOd6) 6.61 (m, 1H), 6.9 (m, 1H).

1. temperatureThe mixture was cooled to ambient temperature
2. customthe precipitate was isolated
3. customdried under vacuum
4. customThe material so obtained
5. temperatureheated to 80–90° C. for 10 minutes
6. temperatureThe mixture was cooled to ambient temperature
7. customThe precipitate was isolated
8. washwashed with water
9. customdried under vacuum at 50° C.

ORD record

ord-3e2b6062f9b24746b658fb5462326b87

Source dataset

uspto-grants-2006_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07049438B2