Imidazole → (S)-(2-Iodo-1-methyl-ethyl)-carbamic acid tert-butyl ester

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PS-triphenylphosphine (2.5 mmol/g, 1.3 g, 3.3 mmol) was suspended in methylene chloride (12 mL). Imidazole (225 mg, 3.3 mmol) was added and the mixture was cooled to 0° C. in an ice-water bath. To the cooled mixture was added iodine (838 mg, 3.3 mmol), and the resulting mixture was warmed to room temperature, stirred 10 minutes and recooled to 0° C. Boc-L-alaninol (463 mg, 2.64 mmol) in methylene chloride (3 mL) was added over several minutes. The resulting mixture was stirred at 0° C. for 1 hour, warmed to room temperature and stirred 2 h. The mixture was filtered. The solids collected were washed thoroughly with ethyl acetate. The filtrate washed with dilute aqueous HCl (3%), sodium thiosulfate (1 M), saturated aqueous sodium bicarbonate and brine. The extracts were then dried over magnesium sulfate, filtered and concentrated under reduced pressure. The crude tert-butyl [(1S)-2-iodo-1-methylethyl]carbamate (xxvii) was obtained as a yellow oil and used without further purification. 1H NMR (300 MHz, CDCl3): δ 3.34-3.56 (m, 2H), 3.27 (dd, J=3.7, 9.8 Hz, 1H), 1.43 (s, 9H), 1.18 (d, J=6.7 Hz, 3H).

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