Sulfuric Acid → 7-bromo-6-fluoro-2,3-dihydro-1H-indole-2,3-dione

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Reaction Conditions

Reaction Steps

A 2 L 3-neck flask with a temperature probe adapter was fixed with a mechanical stirrer, condenser, and temperature probe. The flask was charged with conc. sulfuric acid (79 mL, 1418 mmol) and was heated to 70° C.; solid N-(2-bromo-3-fluorophenyl)-2-(hydroxyimino)acetamide (719a; 12.34 g, 47.3 mmol) was then slowly added (exotherm) and the temperature raised to 100° C. The brown solution was stirred at 90° C. for 45 min. The heating mantle was replaced with an ice bath to cool the reaction mixture to RT; the brown solution was poured into a beaker containing ice (500 mL), diluted with EtOAc (200 mL), added to a separatory funnel, and extracted with EtOAc (2×150 mL); the combined organics were dried over Na2SO4 and concentrated to give 7-bromo-6-fluoroindoline-2,3-dione (11.53 g, 47.3 mmol, 100% yield) as a reddish solid. 1H NMR (400 MHz, CDCl3) δ ppm 6.91 (t, J=8.51 Hz, 1H) 7.63 (dd, J=8.22, 4.89 Hz, 1H) 7.99 (br. s., 1H). 19F NMR (377 MHz, CDCl3) δ ppm −90.65 (s, 1F). MS (ESI, pos. ion) m/z: 243.9/245.9 (M+1).

Provenance & Evidence