To a stirred solution of tert-butyl 3-formylazetidine-1-carboxylate (1.3 g, 27 mmol) in methanol (70 ml) was added dimethyl (1-diazido-2-oxopropyl)phosphonate (6 g, 31.2 mmol) followed by potassium carbonate (14.92 g, 108 mmol) at 0 °C. The reaction mixture was stirred at 0 °C for 3 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate (150 ml), filtered and concentrated under reduced pressure to give the crude product. The crude product was purified by fast chromatography (silica gel, eluent: 0-100% hexane solution of ethyl acetate) to give tert-butyl 3-alkynyl-1-azetidinecarboxylate (4.6 g, 94%).1H NMR (400 MHz, DMSO-d6) δ 1.34 (s, 9H), 3.22-3.23 (m, 1H), 3.34-3.39 (m, 1H ), 3.68 (t, J = 6.8 Hz, 2H), 4.04 (t, J = 8.4 Hz, 2H).
