Sulfuric Acid → 1,2-Benzothiazol-5-ol

Temperature

90 °C

5-Aminobenzo[d]isothiazole (217 mg, 1.45 mmol) was suspended/dissolved in water (20 mL) containing concentrated sulphuric acid (1.5 mL) and heated at 90° C. for 2 h. This solution was cooled to 0° C. and sodium nitrite (105 mg, 1.52 mmol) in water (1 mL) was added over 5 min and the mixture allowed to warm to ambient temperature. The diazonium salt was added dropwise over 20 min to a solution of concentrated sulphuric acid (1 mL) in water (12 mL) at 90° C. and stirred at this temperature for 2 h before hot filtering to remove an insoluble solid. The filtrate was extracted with dichloromethane (3×20 mL) and the combined organic extracts washed with brine (50 mL), dried (MgSO4) and concentrated in vacuo to give the title compound as a brown solid (65 mg, 30%).

1. temperatureThis solution was cooled to 0° C.
2. temperatureto warm to ambient temperature
3. filtrationbefore hot filtering
4. customto remove an insoluble solid
5. extractionThe filtrate was extracted with dichloromethane (3×20 mL)
6. washthe combined organic extracts washed with brine (50 mL)
7. dry with materialdried (MgSO4)
8. concentrationconcentrated in vacuo

ORD record

ord-10dccd6e2a7f4de382b4276eb5c8f13e

Source dataset

uspto-grants-2011_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07868017B2