Hydrogen Bromide → 2-Methyl-1H-indol-6-ol

Participants

Reaction Steps

To a suspension of lithium aluminum hydride (3.7 g, 97 mmol) in 1,4-dioxane (97 mL) was slowly added dropwise a solution of methyl 6-methoxy-1H-indole-2-carboxylate (2.0 g, 9.8 mmol) in 1,4-dioxane (30 mL) under ice-cooling. After dropwise addition, the reaction mixture was heated under reflux for 24 hr. A saturated aqueous sodium sulfate solution was added to the mixture under cooling, magnesium sulfate was added and the insoluble material was filtrated. The filtrate was concentrated under reduced pressure, and the residue was recrystallized from hexane to give 6-methoxy-2-methyl-1H-indole (1.0 g, 6.5 mmol) as a yellow solid. To a solution of 6-methoxy-2-methyl-1H-indole (1.0 g, 6.2 mmol) in acetic acid (15 mL) was added 48% aqueous hydrogen bromide (31 mL) at room temperature, and the reaction mixture was heated under reflux for 3 hr. The solvent was evaporated under reduced pressure, ethyl acetate/tetrahydrofuran and saturated aqueous sodium hydrogencarbonate solution were added to the residue. The aqueous layer was extracted with ethyl acetate/tetrahydrofuran (×3). Combined organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and filtrated. The filtrate was concentrated under reduced pressure, and the residue was washed with ethyl acetate/hexane to give the title compound (600 mg, 65%) as a white solid.

Provenance & Evidence