Trimethyl borate → 6-Fluoro-1-benzothiophene-7-ol

Participants

Reaction Steps

(Ref: Briner, K; Burkholder, T. P; Conway, R. G; Cunningham, B. E; Finley, D. R; Heinz, L. J; Jesudason, C. D; Kohlman, D. T; Liang, S. X; Xu, Y. C. Preparation and use of serotonergic benzothiophenes. WO 0109126 A1. Chem. Abs. 134:162912). To a solution of 7-bromo-6-fluoro-1-benzothiophene (0.2 g, 0.9 mmol) and trimethylborate (0.2 mL, 1.8 mmol) at −78° C. was added tert-butyllithium dropwise. After 10 mins at −78° C. the reaction was quenched by pouring onto saturated ammonium chloride. This was extracted with ethyl acetate (3×10 mL) and the solvent removed in vacuo from the combined organic extracts. The residue was taken up in ethyl acetate (4 mL) and 10% aqueous hydrochloric acid (4 mL) was added, the mixture was stirred at room temperature for 1 h. The organic layer was separated and the aqueous layer extracted with ethyl acetate (2×10 mL). The combined organic extracts were dried (MgSO4) and the solvent removed in vacuo. The residue was taken up in TBF (10 mL), water (2 mL) and cooled to 0° C. then 10% aqueous sodium hydroxide (2 mL) and 28% hydrogen peroxide (1 mL) were added to this and stirred for 0.5 h at 0° C. The mixture was warmed to room temperature and stirred for 2 hours, before a acetic acid (3 mL) was added. The mixture was extracted with ethyl acetate (3×10 mL), dried (MgSO4) and the solvent removed in vacuo, to give a purple solid. This was purified by flash chromatography with a gradient of 0-20% ethyl acetate in iso-hexane to give the title compound (56 mg, 38%); δH (300 MHz, CDCl3) 7.41 (4H, m, ArH).

Provenance & Evidence