General procedure for the synthesis of tert-butyl 3-(2-bromoethyl)azetidine-1-carboxylate from tert-butyl 3-(2-hydroxyethyl)azetidine-1-carboxylate: To a solution of tert-butyl 3-(2-hydroxyethyl)azetidine-1-carboxylate (6.1 g, 30.3 mmol) in dichloromethane (100 mL) was added, in sequence, at 0 °C carbon tetrabromide (19.8 g 60.6 mmol) and triphenylphosphine (15.7 g, 60.6 mmol). The reaction mixture was stirred at room temperature overnight. After completion of the reaction, the mixture was concentrated and the residue was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate=100:1) to afford tert-butyl 3-(2-bromoethyl)azetidine-1-carboxylate (5.5 g, 69.4% yield) as a colorless oil.LC-MS m/z: 208 [M+H-56].
