Dichloromethane → 7-Bromo-4-methoxy-1H-indole

Participants

Reaction Steps

2-Bromo-5-methoxy-aniline (4.4 g, 21.8 mmol) was added dropwise to a solution of boron trichloride in methylene chloride (1.0 M, 24 mL, 24 mmol) cooled with ice water. The reaction mixture was warmed to room temperature, stirred for 30 min, and chloroacetonitrile (4.01 mL, 26.2 mmol) and aluminum chloride (4.01 g, 24.0 mmol) were added, followed by 1,2-dichloroethane (28.5 mL). The reaction mixture was heated to 70° C. to distill off methylene chloride, and then heated to reflux for 24 hrs. After cooling to 0–5° C., the mixture was treated with 2.5 M HCl (38.4 mL) carefully, and then heated to 80° C. for 1 h until all solids dissolved. The aqueous layer was separated, extracted with methylene chloride and the combined extracts washed with water and brine, dried (sodium sulfate) and evaporated to a yellow solid, which was used without further purification. The crude product was taken into dioxane (37 mL) and water (4.2 mL), and treated with sodium borohydride (0.91 g, 24.0 mmol) in portions. After stirring at room temperature for 30 min, all the starting material was consumed and the reaction mixture was then heated to reflux for 14 hrs. After cooling to room temperature, the mixture was treated with concentrated HCl, and extracted with ethyl acetate. The organic extract was washed with water and brine; dried (sodium sulfate), and concentrated. Column chromatography on silica gel (hexanes/ethyl acetate) gave 4-methoxyl-7-bromoindole (1.2 g, 24%). 1H NMR (400 MHz, CDCl3) 3.94 (s, 3H), 6.44 (d, J=8.21 Hz, 1H), 6.73 (m, 1H), 7.17 (t, J=2.74 Hz, 1H), 7.22˜7.26 (m, 1H), 8.32 (br, 1H); MS (ES, m/z): C9H8BrNO: 227.99 (M+(79Br)+1), 230.0(M+(81Br)+1).

Provenance & Evidence