[OH:1][CH:2]1[CH2:5][N:4]([C:6]([O:8][C:9]([CH3:12])([CH3:11])[CH3:10])=[O:7])[CH2:3]1.C(N(CC)CC)C.[C:20](OC(=O)C)(=[O:22])[CH3:21]>CN(C1C=CN=CC=1)C.C(Cl)Cl>[C:20]([O:1][CH:2]1[CH2:3][N:4]([C:6]([O:8][C:9]([CH3:12])([CH3:11])[CH3:10])=[O:7])[CH2:5]1)(=[O:22])[CH3:21]A solution of tert-butyl 3-hydroxyazetidine-1-carboxylate (2.0 g), DMAP (1.55 g) and triethylamine (2.34 g) in DCM (80 mL) was cooled to 0° C. A solution of acetic anhydride (2.35 g) in DCM (20 mL) was added dropwise over 20 minutes and the reaction mixture was stirred at room temperature for 1 hour. The mixture was washed with water and brine, dried (MgSO4) and filtered. The filtrate was concentrated in vacuo and the residue was dissolved in ether and washed with 10% aqueous citric acid solution and brine, dried (MgSO4), filtered. The filtrate was concentrated in vacuo to give tert-butyl 3-acetoxyazetidine-1-carboxylate (2.34 g) as a clear oil.
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