Dimethylformamide → Methyl 3-amino-5-(3-chlorophenyl)thiophene-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

Phosphorous oxychloride (6.7 mL) was added to dimethylformamide (11 mL) with ice cooling to keep the internal temperature below 25° C. After 20 minutes, (3-chlorophenyl)ethanone (5 g) was added portionwise keeping the internal temperature below 30° C. The reaction mixture was heated to 50° C. and then treated cautiously with hydroxylamine hydrochloride (10 g). The reaction mixture was stirred for 20 minutes at room temperature and water (50 mL) was added. After a further 30 minutes, the reaction mixture was extracted three times with ethyl acetate. The combined extracts were washed with brine, dried (MgSO4) and evaporated to give an oil. This oil was dissolved in methanol (50 mL) and treated with methyl mercaptoacetate (2.7 mL) and sodium methoxide (7.3 mL of a 25% solution in methanol). After reflux for 1 h, the cooled reaction mixture was reduced to one third volume and water was added. The reaction mixture was extracted three times with ethyl acetate. The combined extracts were dried (MgSO4), the solvent was evaporated and the residue was chromatographed on silica eluting with dichloromethane/isohexane mixtures to give the sub-title ester (2.0 g).

Provenance & Evidence