Hydrochloric Acid → Thiophen-3-amine oxalate

Participants

Reaction Conditions

Reaction Steps

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).

Provenance & Evidence