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General procedure for the synthesis of 1-BOC-4-(4-bromo-2-cyanophenyl)piperazine from 2-fluoro-5-bromobenzonitrile and N-BOC-piperazine: in a pressure tube, 5-bromo-2-fluorobenzonitrile (2,500 mg, 12.5 mmol), tert-butyl piperazine-1-carboxylate (2,444.45 mg, 13.12 mmol) and triethylamine (5.23 mL. 37.5 mmol) were dissolved in dimethyl sulfoxide (10 mL) and the reaction was refluxed at 100 °C. After completion of the reaction, the mixture was cooled and separated by extraction with ethyl acetate and saturated aqueous sodium bicarbonate. The organic phase was dried with anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by fast column chromatography on silica gel, eluting with a 5-60% ethyl acetate/hexane gradient to afford the light brown oily product tert-butyl 4-(4-bromo-2-cyanophenyl)piperazine-1-carboxylate (3660 mg, 80% yield).

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