[CH2:1]([NH:8][C:9](=[O:14])[CH2:10][C:11](=[O:13])[CH3:12])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[Br:15]Br.C(=O)(O)[O-].[Na+]>ClCCl>[CH2:1]([NH:8][C:9](=[O:14])[CH2:10][C:11](=[O:13])[CH2:12][Br:15])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1To a solution of N-benzyl-3-oxobutanamide (compound A 100 g, 522.9 mmol) in dichloromethane (500 ml) at 0-5° C. was added dropwise a solution of bromine (25.55 ml, 575.2 mmol) over 6 h. The reaction mixture was warmed up to 20-25° C. and stirred for 2 hours (bromine colour disappeared). An aqueous solution (600 mL) of sodium bicarbonate (65.9 g, 784.44 mmol) was added to the mixture. The organic layer was separated, washed with brine (200 mL), and then evaporated to dryness to give N-benzyl-4-bromo-3-oxobutanamide (114.25 g, quantitative) and was used in the next step without further purification.
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