Boron tribromide → (6-Hydroxy-benzo[b]thiophen-3-yl)-acetic acid ethyl ester

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Reaction Steps

A solution of (6-methoxy-benzo[b]thiophen-3-yl)-acetic acid ethyl ester (3.81 g, 15.22 mmol) in dichloromethane (50 mL) at −78° C. is added boron tribromide (38.1 mL, 38.1 mmol) dropwise. The mixture is stirred and allowed to warm to room temperature overnight. The mixture is cooled to 0° C. and quenched with water (100 mL). The organic layer is separated, and the aqueous layer is extracted with EtOAc (50 mL). The combined organic layers are dried over Na2SO4, filtered, and concentrated. The crude product is purified by flash chromatography eluting with 30-40% EtOAc/Hexanes. The appropriate fractions are pooled and concentrated under reduced pressure. The material is dried in vacuo to afford (6-hydroxy-benzo[b]thiophen-3-yl)-acetic acid ethyl ester (3.35 g, 93%). ES/MS m/e 237.0 (M+1); 235.0 (M−1).

Provenance & Evidence