5394-13-8

White solid

2-Bromobenzo[b]thiophene is used in the stereoselective preparation of halogenated benzoxazines via enantioselective halocyclization of o-anilidostyrenes using chiral anion phase-transfer catalysts.

To a solution of benzo[b]thiophene (2.0 g, 15 mmol) in tetrahydrofuran (20 mL) was slowly added n-butyllithium (2.5 M hexane solution, 12 mL, 30 mmol) dropwise at -70 °C and under nitrogen protection. The reaction mixture was stirred continuously at this temperature for 30 minutes. Subsequently, N-bromosuccinimide (5.3 g, 30 mmol) was added and the reaction system was slowly warmed from -70 °C to room temperature over 1 hour. Upon completion of the reaction, the reaction was quenched with saturated aqueous ammonium chloride solution (20 mL) followed by extraction with ethyl acetate (3 x 30 mL). The organic phases were combined, concentrated in vacuum, and the residue was purified by silica gel column chromatography [eluent: petroleum ether/ethyl acetate = 100:1] to afford 2-bromobenzothiophene (0.50 g, 16% yield) as a white solid.

[1] Patent: WO2006/56418, 2006, A2. Location in patent: Page/Page column 68-69
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[3] Bioorganic and Medicinal Chemistry Letters, 2006, vol. 16, # 11, p. 3034 - 3038
[4] Patent: WO2017/69980, 2017, A1. Location in patent: Paragraph 00274; 00275
[5] Journal of the American Chemical Society, 1952, vol. 74, p. 664