To a stirred solution of 2-(2-bromo-6-nitrophenyl)acetic acid (0.66 g, 2.54 mmol) dissolved in a solvent mixture of 50% H2SO4 (6.0 mL) and EtOH (10.0 mL), zinc powder (0.66 g, 10.1 mmol) was added, and the reaction was carried out at 90 °C in an N2 atmosphere. After completion of the reaction, the reaction mixture was treated according to a similar method as in preparation 5 to give the intermediate 4-bromoindolone (0.50 g, 93% yield). The mass spectrum (electrospray ionization) showed an M+1 peak of 212 and an M+2 peak of 214.
