[CH2:1]([CH:5]1[CH2:9][O:8][C:7]([CH3:11])([CH3:10])[O:6]1)[CH2:2][C:3]#[CH:4].CN1C(=O)N(C)CCC1.[Li][CH2:22][CH2:23][CH2:24][CH3:25].CCCCCC>C1COCC1>[CH:24]1([CH2:25][C:4]#[C:3][CH2:2][CH2:1][CH:5]2[CH2:9][O:8][C:7]([CH3:11])([CH3:10])[O:6]2)[CH2:22][CH2:23]1To a solution of 4-But-3-ynyl-2,2-dimethyl-[1,3]dioxolane (6 mmol, 1.0 g) in 40 ml anhydrous THF and anhydrous DMPU (26 mmol, 3 g) was added a solution of 2.5M BuLi in hexane (9.01 mmol, 3.6 mL) at −78° C. It was stirred at −78 ° C. for 15 minutes and slowly warmed up to room temperature. The reaction mixture was quenched with sat. NH4Cl and extracted by EtOAc. The combined organic layer was washed with H2O and brine, dried by MgSO4 and concentrated. Silica gel chromatography (2˜10% EtOAc/Hexane) 4(5-Cyclopropyl-pent-3-ynyl)-2,2-dimethyl-[1,3]dioxolane as a clear oil; 1H NMR (400 MHz, CDCl3): δ 4.22–5.15 (m, 1H), 4.07 (dd, 1H, J3=8.0 Hz, J2=6.0 Hz), 3.57 (dd, 1H, J1=7.9 Hz, J2=7.1 Hz), 2.29–2.23 (m, 2H), 2.20–2.16 (m, 2H), 1.83–1.77 (m, 1H), 1.72–1.65 (m, 1H), 1.40 (s, 3H), 1.35 (s, 3H), 0.91–0.86 (m, 1H), 0.46–0.41(m, 2H), 0.21–0.17 (m, 2H).
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