Hydrochloric Acid → Thiophen-3-amine oxalate

Temperature

115 °C

Methyl 3-aminothiophene-2-carboxylate (1.52 g, 9.68 mmol) is dissolved in 2M NaOH (10 mL, 20 mmol) and heated to reflux in a 115° C. oil bath for 30 min. The mixture is cooled to rt, placed in an ice bath, and carefully acidified with concentrated HCl. The slurry is filtered and rinsed with H2O (25 mL). The cake is then dissolved in acetone (50 mL), dried over MgSO4, filtered, and concentrated to a thick paste. The crude material is dissolved in 1-propanol (25 mL), and oxalic acid (0.90 g, 10.0 mmol) is added portionwise. The mixture is heated at 38° C. for 45 min, cooled to rt, and diluted with ether. The precipitate is isolated via filtration, and washed with ether, affording 3-amino-thiophene oxalate (C135) as a fluffy white solid (70% yield). HRMS (FAB) calculated for C4H5NS+H: 100.0221, found 100.0229 (M+H).

1. temperatureheated
2. temperatureThe mixture is cooled to rt
3. customplaced in an ice bath
4. filtrationThe slurry is filtered
5. washrinsed with H2O (25 mL)
6. dissolutionThe cake is then dissolved in acetone (50 mL)
7. dry with materialdried over MgSO4
8. filtrationfiltered
9. concentrationconcentrated to a thick paste
10. dissolutionThe crude material is dissolved in 1-propanol (25 mL)
11. temperatureThe mixture is heated at 38° C. for 45 min
12. temperaturecooled to rt
13. customThe precipitate is isolated via filtration
14. washwashed with ether

ORD record

ord-bad4079d0c724a5eb536acab6b9fa433

Source dataset

uspto-grants-2005_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06911543B2