N-bromobutanimide → 5-(Bromomethyl)benzo[b]thiophene

Participants

Reaction Steps

A mixture of 5-methylbenzo[b]thiophene (3.8 g, 25.6 mmol), NBS (4.7 g, 27 mmol), and benzoyl peroxide (310 mg, 1.3 mmol) were refluxed one hour in CCl4 (100 mL) while being irradiated with a sunlamp. Upon completion, the reaction was cooled, diluted with Et2O, filtered and concentrated to yield 5.8 g of 5-bromomethylbenzo[b]thiophene. The crude 5-bromomethylbenzo[b]thiophene was refluxed for 36 hours in 1:1 dioxane/2N aq. NaOH (128 mL). After cooling, extraction with EtOAc and concentration of the extracts, the residue was chromatographed on silica gel eluting 2.6 g of 5-hydroxymethylbenzo[b]thiophene with 35% EtOAc/hexane. The title compound (1.96 g) was obtained after filtration and concentration of the reaction product produced by refluxing 5-hydroxymethylbenzo[b]thiophene (2.08 g, 12.7 mmol) and 50% MnO2 /C (17.6 g, 101 mmol) for five hours in toluene while H2O was continually removed using a Dean-Stark trap.

Provenance & Evidence