Ammonium Chloride → Ethyl 5-amino-4-methoxythiophene-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

A mixture of ethyl 4-methoxy-5-nitrothiophene-2-carboxylate (Int. 68) (300 mg, 1.297 mmol) (prepared as described in Step 4 hereabove reported), and ammonium chloride (139 mg, 2.59 mmol) in EtOH/water=2/1 (18 ml) was heated at 50° C. until complete dissolution. Iron powder (435 mg, 7.78 mmol) was added, and the reaction was heated at 80° C. for 2 hours. The mixture was filtered and the filtrate was concentrated under vacuum; the residue was portioned between brine and EtOAc and the organic phase was dried over sodium sulfate. The solvent was removed to afford ethyl 5-amino-4-methoxythiophene-2-carboxylate (Int. 69) in a mixture with approximately 30% of corresponding methyl ester (261 mg, 1.297 mmol, MS/ESI+201.9 [MH]+). This intermediate was used as such in the following step.

Provenance & Evidence