Sodium borohydride → (2-Bromo-5-phenylthiophen-3-yl)methanol

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Reaction Steps

Under a nitrogen atmosphere, a suspension of 2-bromo-5-phenylthiophene-3-carboxylic acid (11d) (260 mg, 0.92 mmol) in thionyl chloride (2 mL) was refluxed for 30 minutes. The reaction mixture was concentrated in vacuo and co-evaporated with toluene to provide an oil which was slowly added to a solution of sodium borohydride (81 mg, 0.92 mmol) in anhydrous dimethoxyethane (8 mL) under a nitrogen atmosphere at 10° C. After stirring at room temperature for 30 minutes, the reaction mixture was concentrated in vacuo. Water (8 mL) was added to the residue, followed by acetic acid (1.5 mL) to ensure sodium borohydride decomposition. The mixture was basified with 28% ammonium hydroxide until pH 8 and extracted with ethyl dichloromethane (2×10 mL). The organic layer was dried over sodium sulfate, filtered and evaporated to dryness to provide the desired alcohol (11e) (220 mg, 0.82 mmol, 89%) as a pink oil, which was used without further purification.

Provenance & Evidence