897957-06-1

General procedure for the synthesis of 6-bromo-1-methyldihydro-2-one from 6-bromo-1-methylindole-2,3-dione: 6-bromo-1-methyldihydro-2,3-dione (397 mg, 1.65 mmol) was mixed with hydrazine hydrate (1 mL, 20.6 mmol) and the reaction was heated to 100 °C for 1 h. The reaction was then warmed to 125 °C and continued for another hour. After completion of the reaction, the mixture was cooled to room temperature and layered with dichloromethane (DCM) and water. The aqueous layer was extracted twice with DCM and the organic layers were combined, washed with saturated brine and dried over anhydrous sodium sulfate. The organic phase was concentrated under reduced pressure and the resulting residue was purified by column chromatography with the eluent cyclohexane/ethyl acetate (3:1, v/v). The product yield was 65%. Mass spectrometric analysis showed m/z 226 [M + H]+, m/z 224 [M + H]- with a retention time (rt) of 0.58 min (LC-MS method b).

[1] Patent: WO2013/41497, 2013, A1. Location in patent: Page/Page column 36
[2] Patent: WO2014/140075, 2014, A1. Location in patent: Page/Page column 215; 217
[3] Patent: WO2014/140081, 2014, A1. Location in patent: Page/Page column 61; 62
[4] Patent: US2014/275159, 2014, A1. Location in patent: Paragraph 0328; 0331
[5] Patent: WO2014/140091, 2014, A1. Location in patent: Page/Page column 74; 75