Dichloromethane → Dimethyl 3-(2-bromoethylamino)-2-pentenedioate

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Reaction Conditions

Reaction Steps

Dimethyl 3-(2-methanesulfonylethylamino)-2-pentenedioate (156.3 g, 529 mmol) was added to a 2 L three-neck flask, which was fitted with a mechanical stirrer, thermometer, and reflux condenser. Dichloromethane (750 mL) was added and stirred until the mesylate had completely dissolved, anhydrous lithium bromide (69.0 g, 794 mmol) was added, and the mixture stirred at 35° C. for 19 hours. The mixture was cooled to 0° C. and water (250 mL) added, then stirred for 5 minutes and the phases separated. The organic phase was washed with water (3×250 mL) and brine (150 mL), and dried over anhydrous potassium carbonate for 15 minutes. Rotary evaporation of the solvent under reduced pressure (50° C.) gave 128.4 g of crude dimethyl 3-(2-bromoethylamino)-2-pentenedioate as a yellow oil, which quickly solidified to a yellow solid. The crude material was purified by extraction into boiling hexane (5×750 mL) and recrystallization from hexane, and the pot residues extracted and recrystallized, to give a total of 90.8 g (61.2% yield) of dimethyl 3-(2-bromoethylamino)-2-pentenedioate as white needles. An NMR spectrum in CDCl3 indicated an Z/E isomer ratio of 19:1, and remeasurement of the CDCl3 solution after three days indicated an Z/E ratio of 4:1. The two isomers were not separated.

Provenance & Evidence