Iodine → (3R,6S)-3-Amino-1-(2-methoxyethyl)-6-phenylazepan-2-one

To a slurry of 1-bromo-2,3-dichlorobenzene (1.46 g, 6.46 mmol) in diethyl ether (10 mL) was added magnesium (0.157 g, 6.46 mmol) and a crystal of iodine. This mixture was refluxed for 3 h, and then cooled to room temperature. A solution of benzyl (2R,5E)-2-[bis(tert-butoxycarbonyl)amino]-6-nitrohex-5-enoate (0.50 g, 1.08 mmol) in diethyl ether (10 mL) was cooled to 0° C., and 2.0 mL of the Grignard solution prepared above was added. After 1 and 2 h, respectively, 2.0 and 1.0 mL of the Grignard solution was added. The reaction was quenched with a saturated aqueous solution of ammonium chloride, the phases separated and the organic phase washed with saturated aqueous sodium potassium tartrate and brine. The combined organics were dried over magnesium sulfate, filtered and concentrated to give a residue that was purified by silica gel chromatography (0%→3% methanol/dichloromethane) to give the title compound (0.52 g). MS 411.0 (M+1-2Boc).