Benzyl chloroformate → 2-Benzyl 1-t-butyl 5-bromo-1H-pyrrole-1,2-dicarboxylate

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Reaction Steps

t-Butyl 2,5-dibromo-1H-pyrrole-1-carboxylate (10.98 g, 33.8 mmol) synthesized in Example (66a) was dissolved in diethyl ether (135 mL), and cooled to −78° C. n-Butyl lithium (2.77M hexane solution, 12.8 mL, 35.5 mmol) was added dropwise slowly, and stirring was carried out for 1 hour. To the reaction solution, benzyl chloroformate (6.25 mL, 44.0 mmol) was added dropwise slowly, and stirring was carried out for 30 minutes. With the temperature of the reaction solution being gradually raised to room temperature, stirring was carried out for 1 hour. To the reaction solution, were added a saturated aqueous ammonium chloride solution (200 mL) and diethyl ether (300 mL), and the solution was separated. The organic layer was washed with saturated brine, and subsequently dried over sodium sulfate. The solvent was distilled off under reduced pressure, and the resulting residue was purified using silica gel column chromatography (elution solvent: ethyl acetate/hexane=5%-45%) to afford the desired compound (8.80 g, yield 68%) as a reddish brown oil.

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