Sulfuric Acid → Thieno[3,2-b]pyridin-6-ol

Participants

Reaction Conditions

Reaction Steps

To a solution of 6-aminothieno[3,2-b]pyridine (2.5 g, 16.6 mmol) in water (22 ml) containing concentrated sulfuric acid (4.15 ml) and cooled at 0° C. was added dropwise with vigorous stirring a solution of sodium nitrite (1.26 g, 18.3 mmol) in water (7 ml) to give a copious yellow precipitate. This slurry was pipetted dropwise into 5% sulfuric acid (110 ml) maintained at 110° C. After an additional hour, the solution was cooled to room temperature and washed with methylene chloride. This aqueous solution was made basic with sodium hydroxide and washed again with methylene chloride to remove any unreacted starting material. The aqueous solution was then made neutral with hydrochloric acid and the precipitated product was extracted into chloroform/methanol, dried over anhydrous sodium sulfate and filtered through a pad of charcoal and the solvents were evaporated to give product (2.2 g) which was purified by crystallization from hot ethyl acetate/methanol to give pure product (1.81 g, 72% yield), m.p. 228°-230 ° C.

Provenance & Evidence