Synthesis
Step 2: 7-fluoroindoline-2,3-dione N-(2-fluorophenyl)-2-(hydroxyimino)acetamide (30 g, 164.84 mmol) was dissolved in concentrated sulfuric acid (100 mL), and the reaction was stirred at 80 °C for 2 hours. Upon completion of the reaction, the mixture was slowly poured into an ice-water mixture, and the precipitated brick-red solid was collected by filtration and dried to give 25 g of 7-fluorodihydroindole-2,3-dione in 90% yield. The product was analyzed by LCMS to confirm that the molecular ion peak was 166 (M + H)+.
References
[1] Patent: US2008/139558, 2008, A1. Location in patent: Page/Page column 55
[2] Journal of Heterocyclic Chemistry, 1990, vol. 27, # 7, p. 2151 - 2163
[3] Proceedings of the Royal Society of London, Series B: Biological Sciences, 1958, vol. 148, p. 481,488
[4] Journal of Medicinal Chemistry, 1992, vol. 35, # 11, p. 2085 - 2094
[5] European Journal of Medicinal Chemistry, 1994, vol. 29, # 10, p. 743 - 751
