N-bromobutanimide → 2-Bromo-5-fluoro-3-methylbenzo[b]thiophene

Participants

Reaction Conditions

Reaction Steps

A mechanically-stirred solution of 5-fluoro-3-methylbenzo[b]thiophene (50.32 g, 0.303 mol, 1.0 equiv) in acetonitrile (350 mL) is treated with NBS (56.32 g, 0.318 mol, 1.05 equiv). An initial endotherm reduces the reaction temperature to 17° C. A subsequent exotherm then increases the reaction temperature to 40° C. over a 10 min. period, at which time the reaction is cooled to 18-20° C. by application of an ice water bath. The reaction is stirred at RT for an additional 35 min. and the resultant slurry is slowly diluted with water (350 mL). The slurry is stirred for 10 min and the product is filtered, washed with 50:50 acetonitrile:water (100 mL) and dried to a colorless crystalline solid (65.56 g, 88%).

Provenance & Evidence