Thieno[2,3-b]pyridine (8CI,9CI)

609-40-5

122-31-6

272-23-1

Thieno[2,3-b]pyridine was synthesized as follows: 1.08 g (8.3 mmol) of 2-nitrothiophene and 16 mL of concentrated hydrochloric acid were sequentially added to a vigorously stirred mixture at 30 °C. Subsequently, a total of 2.08 g of granulated tin was added in batches of 0.42 g. After most of the tin was dissolved, 6 mL of ethanol and 0.5 g of anhydrous zinc chloride were added to the mixture and the mixture was heated to 85°C. The mixture was then stirred vigorously at 30°C for 1 hour. Next, 1.4 g (6.5 mmol) of malonaldehyde tetraethyl acetal (purchased from Aldrich Chemical Co.) dissolved in 3 mL of ethanol was added all at once. The reaction mixture was maintained at 85 °C for 1 h before the reaction was quenched by pouring 9 g of ice. The aqueous mixture was alkalized with concentrated ammonia solution and subsequently extracted with three 5 mL dichloromethane. The organic phases were combined and distilled to give 0.4 g (44% yield) of the target product thieno[2,3-b]pyridine as a light yellow liquid.