Methyl 4-bromocrotonate

67-56-1

13991-36-1

1117-71-1

The general procedure for the synthesis of methyl 4-bromobut-2-enoate from methanol and (E)-4-bromobut-2-enoic acid was as follows: (E)-4-bromobut-2-enoic acid (1.525 g, 9.24 mmol) and anhydrous methanol (10 ml) were added into a 50 ml three-necked flask, and stirred at 0 °C until complete dissolution. Thionyl chloride (5.49 g, 46.19 mmol, 5 ml) was added slowly dropwise, and bubbles were observed during the dropwise addition. After the dropwise addition, the reaction mixture was gradually warmed up to room temperature and stirring was continued for 15 h. The completion of the reaction was monitored by thin layer chromatography (TLC). After completion of the reaction, the solvent was evaporated to dryness under reduced pressure and the residue was extracted with ethyl acetate and water. The organic phase was separated and dried with anhydrous sodium sulfate. The dried organic phase was concentrated by rotary evaporator to obtain the crude product. The crude product was purified by column chromatography with the eluent ratio of petroleum ether:ethyl acetate=8:1, and the final product was methyl 4-bromobut-2-enoate (1.54 g, 93.1% yield) as a red oily liquid.