7-BROMO-BENZO[B]THIOPHENE

137105-52-3

1423-61-6

Preparation of 7-bromobenzo[b]thiophene of Scheme I, Step B: Chlorobenzene (100 mL) and polyphosphoric acid (30.4 g, PPA) were mixed and heated to reflux. Within 20 min, 2-(2-bromophenylthio)acetaldehyde diethyl acetal (13.7 g, 44.88 mmol, Scheme I, Step A) was dissolved in chlorobenzene (20 mL) and slowly added dropwise to the refluxed mixture. The reaction mixture was kept at reflux for 4 hours and subsequently cooled. The solvent was removed by decantation and toluene (2 x 50 mL) was added to the residue, stirred thoroughly and decanted again. The toluene extract was concentrated under vacuum and the residue was dissolved in a mixture of ethyl acetate and water. The organic phase was washed with saturated sodium bicarbonate solution, dried over anhydrous sodium sulfate, filtered and concentrated to give 7-bromobenzo[b]thiophene (8.91 g, 93% yield).