Preparation of Example 26-2: tert-butyl 3-((methylsulfonyl)oxy)azetidine-1-carboxylate
Under a nitrogen atmosphere, methanesulfonyl chloride (2.57 mL, 33.3 mmol) and triethylamine (11.6 mL, 83.1 mmol) were sequentially added to a solution of tetrahydrofuran (100 mL) containing N-Boc-3-hydroxyazetidine (4.8 g, 27.7 mmol). The reaction mixture was stirred at room temperature for 2 hours. Upon completion of the reaction, saturated aqueous sodium bicarbonate solution was added to the reaction solution and the mixture was diluted with ethyl acetate. The organic layer was separated, washed with saturated brine and subsequently dried over anhydrous sodium sulfate. The desiccant was removed by filtration and the filtrate was concentrated under vacuum. The residue was purified by silica gel column chromatography (eluent ratio: n-heptane/ethyl acetate = 9:1 to 1:1) to quantitatively obtain N-Boc-3-methylsulfonyloxyazetidine.
1H-NMR (CDCl3) δ (ppm): 1.45 (9H, s), 3.07 (3H, s), 4.03-4.18 (2H, m), 4.22-4.36 (2H, m), 5.12-5.27 (1H, m).
