Acetic Acid → Methyl 4-bromo-3-methylthiophene-2-carboxylate

Participants

Reaction Steps

The (trimethylsilyl)diazomethane solution in ether (2.0 M, 41.2 mL, 82.3 mmol) was added dropwise to a solution of 4-bromo-3-methyl-thiophene-2-carboxylic acid (13.0 g, 58.8 mmol, purchased from Oakwood Products) in methanol (50 mL) and tetrahydrofuran (50 mL) at ambient temperature. After the reaction mixture was stirred at ambient temperature for 30 min, acetic acid was added to decompose the excess (trimethylsilyl)diazomethane until the yellow color disappeared. Most of the solvent was evaporated and ethyl acetate was added. The organic solution was washed with saturated sodium bicarbonate solution and brine, dried over anhydrous sodium sulfate and concentrated. The crude product was purified by flash chromatography eluting from silica gel with a gradient of 0-50% ethyl acetate in hexanes to produce 12.8 g of a white solid. 1H NMR (CDCl3, 200 MHz): δ=7.40 (s, 1H), 3.87 (s, 3H), and 2.54 (s, 3H).

Provenance & Evidence