Imidazole → 1-Benzyloxycarbonyl-3-t-butyldiphenylsilyloxyazetidine

Subsequently, to a solution of 1-benzyloxycarbonyl-3-hydroxyazetidine (1.91 g, 9.22 mmol) in dimethylformamide (96 ml) were added t-butyldiphenylsilyl chloride (2.88 ml, 11.1 mmol) and imidazole (756 mg, 11.1 mmol) in an ice bath. The resulting mixture was stirred in the ice bath for 6 hours. After checking the completion of the reaction, the reaction mixture was partitioned between ethyl acetate and 10% aqueous sodium chloride solution. The organic layer was washed with saturated aqueous sodium hydrogencarbonate solution and saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by chromatography on a silica gel column using n-hexane:ethyl acetate (6:1) as the eluant to afford 1-benzyloxycarbonyl-3-t-butyldiphenylsilyloxyazetidine (4.04 g, yield 98%) as a colorless oil.