Procedure for the synthesis of 5-bromo-2,3-dimethylindole: A mixture of 4-bromophenylhydrazine (5.0 g, 22.3 mmol) and 2-butanone (1.6 g, 22.3 mmol) was dissolved in ethanol (60 mL) and the reaction was heated overnight under reflux conditions. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The resulting residue was recrystallized from the ethanol/water solvent mixture to afford the target product 5-bromo-2,3-dimethylindole (3.6 g, 73% yield). The structure of the product was confirmed by NMR hydrogen spectrum (400 MHz, d6-DMSO): δ 10.87 (s, 1H), 7.51 (d, J = 1.2 Hz, 1H), 7.18 (d, J = 6.3 Hz, 1H), 7.07 (dd, J = 6.3 Hz, 1.2 Hz, 1H), 2.31 (s, 3H), 2.13 (s, 3H).
