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General procedure for the synthesis of N-BOC-4-bromoethylpiperazine from tert-butyl 4-(2-hydroxyethyl)piperazine-1-carboxylate: carbon tetrabromide (1.681 g, 5.07 mmol) was dissolved in dichloromethane (17 ml) and cooled in an ice bath. Subsequently, tert-butyl 4-(2-hydroxyethyl)piperazine-1-carboxylate (1.062 g, 4.61 mmol) and triphenylphosphine (1.329 g, 5.07 mmol) were added to this solution. The reaction mixture was stirred overnight at room temperature and additional dichloromethane (11 ml) was added. After completion of the reaction, the solvent was removed by evaporation. The residue was purified by silica gel column chromatography (using a SNAP ULTRA 25g column with hexane/ethyl acetate solvent mixture as eluent) to afford N-BOC-4-bromoethylpiperazine (1.131 g, 83.7% yield) as a yellow solid.

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