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

HRID 569071Notes

Reaction equation

N[C:2]1[CH:3]=[C:4]2[S:10][CH:9]=[CH:8][C:5]2=[N:6][CH:7]=1.S(=O)(=O)(O)[OH:12].N([O-])=O.[Na+]>O>[OH:12][C:2]1[CH:3]=[C:4]2[S:10][CH:9]=[CH:8][C:5]2=[N:6][CH:7]=1

Participants

Conditions

Temperature: 0 °C

Procedure

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.

Workup

additionwas added dropwise
customto give a copious yellow precipitate
temperaturemaintained at 110° C
waitAfter an additional hour
temperaturethe solution was cooled to room temperature
washwashed with methylene chloride
washwashed again with methylene chloride
customto remove
extractionthe precipitated product was extracted into chloroform/methanol
dry with materialdried over anhydrous sodium sulfate
filtrationfiltered through a pad of charcoal
customthe solvents were evaporated

Sources & evidence

ORD record: ord-bbdb6275f3344e12bbe63bc140f3b3ac
Source dataset: uspto-grants-1988_03
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US04731368

Reaction notes

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