Iodine → 6-Hydroxy-5-methoxybenzo[b]thiophene-2-carboxylic acid

Participants

Reaction Steps

Iodine (90 g) was added to a stirred mixture of the product from Step B (73 g) and 90% ethanol (2000 mL). The resultant dark mixture was heated at reflux for 24 hours. Saturated sodium bisulfite solution (20 mL) was added to the cooled reaction mixture and the ethanol was removed in vacuo. The aqueous residue was diluted to 1500 ml with water and extracted with ethyl acetate (4×400 mL). The combined extracts were evaporated in vacuo and the residue was heated on the steam bath with 1N sodium hydroxide solution (1500 mL) for 3 hours. The solution was treated with charcoal, filtered, diluted to 2500 mL with water and acidified with concentrated hydrochloric acid. The precipitated solid was collected, washed with water and dried; yield 36.8 g.

Provenance & Evidence