[Br:1]Br.[C:3]([O:6][CH2:7][CH2:8][N:9]1[CH:13]=[CH:12][CH:11]=[C:10]1[C:14](=[O:20])[C:15]([O:17][CH2:18][CH3:19])=[O:16])(=[O:5])[CH3:4].CCCCCC.C(OCC)(=O)C>ClCCl>[C:3]([O:6][CH2:7][CH2:8][N:9]1[CH:13]=[C:12]([Br:1])[CH:11]=[C:10]1[C:14](=[O:20])[C:15]([O:17][CH2:18][CH3:19])=[O:16])(=[O:5])[CH3:4]Three ml (58.3 mmole) of bromine is added in a dropwise manner to a stirred solution of 14.77 g (58.3 mmole) of ethyl 1-(2-acetoxyethyl)pyrrole-2-glyoxalate in 200 ml anhydrous dichloromethane, cooled to -75° C. After the addition, the reaction is left at -75° C. for 2.5 hours and then the temperature is allowed to increase to room temperature. The solvent is removed in vacuo, dichloromethane is added to the residue and the solution is washed successively with water, 10% sodium bicarbonate solution and water. The organic phase is dried over sodium sulfate, and the solvent is removed in vacuo. The crude product thus obtained (18.3 g) is subjected to column chromatography on Florisil (1 Kg) using hexane-ethyl acetate (9:1) as the eluting solvent. There is thus obtained upon removal of the solvent, 10.9 g (56%) of ethyl 1-(2-acetoxyethyl)-4-bromopyrrole-2-glyoxalate as an oil having the following physical constants:
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