Phosphoric Acid → 7-Bromo-1-benzofuran

Participants

Reaction Steps

A mixture of phosphorus pentoxide (19.3 g) and phosphoric acid (64 ml, 85%) was added carefully to a stirred solution of 2-(2-bromophenoxy)acetaldehyde dimethyl acetal (69.6 g) in chlorobenzene (450 ml) at ambient temperature under nitrogen. The mixture was then heated under reflux for 20 hours, cooled and poured into ice/water (500 ml). The aqueous layer was separated and washed with dichloromethane (2×250 ml). The combined organic extracts were washed with brine (400 ml), dried (MgSO4), and the solvent removed in vacuo. The residue was purified by flash column chromatography over silica using a 1:49 mixture of ether and petroleum ether (b.p. 60-80° C.) as the eluant, followed by distillation to give 7-bromobenzo[b]furan (30.3 g) as a clear oil, b.p. 66-68° C. at 0.93 mbar.

Provenance & Evidence