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With boron tribromide In dichloromethane at 0 - 20℃; for 2 h;
To a cooled (0 °C), stirred solution of 5-methoxy-2-methyl-1H-indole (3.5 g, 21.7 mmol) in dichloromethane (200 mL), boron tribromide 1 M in dichloromethane solution (10 mL, 108 mmol) was added drop-wise. The reaction mixture was allowed to stir at RT for 2 h, before being poured into ice water, and extracted with ethyl acetate. The organic phase was washed with water and brine, dried (Na2SO), filtered, and concentrated in vacuo to afford the title compound (3.13 g, 98percent). MS m/z (relative intensity, 70 eV) 147 (M+,82), 146 (bp), 118 (16), 117 (14), 91 (11). ESIMS: m/z 148.0 (M + H)+.1H NMR (CD3OD, 400 MHz) δ: 2.34 (s, 3H), 5.94 (s, 1H), 6.55 (dd,J = 8.59, 2.34 Hz, 1H), 6.79 (d, J = 2.34 Hz, 1H), 7.05 (d, J = 8.59 Hz, 1H). 13C NMR (CD3OD, 101 MHz) δ: 13.50, 99.71, 104.65, 110.73,111.54, 131.27, 132.87, 137.34, 151.07.
93%
With boron tribromide In dichloromethane; water
A solution of boron tribromide (32.5 ml, 341 mmol) in methylene chloride (60 ml) was added in portions to a solution of 5-methoxy-2-methylindole (25 g, 155 mmol) in methylene chloride (250 ml) cooled at -45° C. After stirring for 15 minutes at -30° C., the mixture was warmed up to ambient temperature and stirred for 1 hour. Methylene chloride (300 ml) was added in portions and the mixture was cooled to 0° C. Water was added in portions and the mixture was adjusted to pH6 with 4N sodium hydroxide. The organic layer was separated. The aqueous layer was extracted with methylene chloride and the organic layers were combined, washed with water, brine, dried (MgSO4) and the volatiles were removed by evaporation. The residue was purified by column chromatography eluding with ethyl acetate/methylene chloride (1/9 followed by 15/85) to give 5-hydroxy-2-methylindole (21.2 g, 93percent).
0.376 g
With boron tribromide In dichloromethane at 20℃; for 3.25 h; Cooling with ice
To a stirred, ice-cooled solution of 5-methoxy-2-methylindole (0.444 g, 3.00 mmol) in dry DCM (30 mL), 1.0 M solution of BBr3 in DCM (15.0 mL, 15 mmol) was added dropwise over 15 min. The reaction mixture was allowed to warm to rt and stirred at rt for 3h. It was then cooled in ice-bath again and excess BBr3 was quenched with slow addition of MeOH (5 mL). The volatiles were removed in vacuo and the residue diluted with water and pH adjusted with 10percent aq K2CO3 to give a suspension. The solid was collected by vacuum filtration, washed with water and dried. The crude product was purified on silica gel (2percent MeOH in DCM) to give 0.376 g 2-methylindole-5-ol. MS (MH+): 148.
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[2] Patent: US2003/212055, 2003, A1,
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[9] Patent: WO2014/183300, 2014, A1, . Location in patent: Page/Page column 36
2
[ 7598-91-6 ]
[ 13314-85-7 ]
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[1] Journal of Medicinal Chemistry, 2002, vol. 45, # 14, p. 3094 - 3102
[2] Research on Chemical Intermediates, 2010, vol. 36, # 8, p. 975 - 983
[3] Journal of Medicinal Chemistry, 2016, vol. 59, # 3, p. 867 - 891
[4] Journal of the Chemical Society, 1951, p. 2029,2031
[5] Bioorganic and Medicinal Chemistry Letters, 1998, vol. 8, # 15, p. 1991 - 1996
3
[ 30891-22-6 ]
[ 13314-85-7 ]
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[1] Journal of Organic Chemistry, 1984, vol. 49, # 25, p. 4833 - 4838
[2] Chemistry Letters, 1997, # 7, p. 679 - 680
4
[ 106-51-4 ]
[ 13314-85-7 ]
Reference：
[1] Research on Chemical Intermediates, 2010, vol. 36, # 8, p. 975 - 983
[2] Journal of Medicinal Chemistry, 2016, vol. 59, # 3, p. 867 - 891
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