Synthesis of Primary Alcohol from Azetidine

Azetidine 6a (14.1 g, 19.09 mmol, 1.0 equiv) was dissolved in CH₂Cl₂ (191 mL) and cooled to 0 °C. Trifluoroacetic acid (14.9 ml, 191 mmol, 10 equiv) was then added over approximately 10 min until the yellow color persisted. The mixture was neutralized by the addition of a saturated aqueous solution of sodium bicarbonate and the aqueous layer extracted 2 additional times with CH₂Cl₂. The combined organic extracts were dried over MgSO₄, filtered and concentrated under reduced pressure to provide the crude product, which was purified by chromatography over silica gel using hexanes/EtOAc to provide the primary alcohol 7a (8.74 g, 92%) as a foam. ${[\mathrm{\alpha }]}_{\mathrm{D}}^{20}=-46.2$ (c 0.59, CHCl₃); IR ν_max (film): 3335, 2873, 1538, 1346, 1166, 905; ¹H NMR (500 MHz, CDCl₃) δ 7.83 (dd, J = 7.8, 1.4 Hz, 1H), 7.79 (dd, J = 7.9, 1.3 Hz, 1H), 7.72 (td, J = 7.7, 1.5 Hz, 1H), 7.66 (td, J = 7.6, 1.3 Hz, 1H), 7.22 (m, 4H), 5.83 (m, 1H), 5.28 (d, J = 17.1 Hz, 1H), 5.17 (d, J = 10.1 Hz, 1H), 4.92 (s, 1H), 3.64 (s, 1H), 3.54 (s, 2H), 3.49–3.42 (m, 1H), 3.37 (m, 1H), 3.21 (s, 3H), 2.92 (t, J = 10.3 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃) δ 147.6, 135.5, 133.8, 133.5, 132.7, 132.6, 132.2, 131.2, 130.9, 125.7, 121.4, 118.6, 67.3, 64.8, 61.4, 61.1, 42.8, 41.8; HRMS (ESI) calcd for C₂₀H₂₃BrN₃O₅S [M + H]⁺: 496.0542, found: 496.0545.