Reaction Steps
Under an atmosphere of N2, a 1.5M solution of LiN(Pri)2THF in c-C6H6 (Aldrich; 43.9 ml, 65.9 mmol) was added dropwise to a stirred solution of 1-tert-butyldimethylsilyl-4-phenyl-2-azetidinone (13.24 g, 50.64 mmol) in dry THF (230 ml) at an inner temperature between -78 and -73 C. After stirring at -78 C for 30 minutes, the reaction mixture became a white slurry. A solution of 3-bromo-2-[(4-methoxybenzoyloxy)methyl]propene (14.69 g, 54.18 mmol) in dry THF (30.0 ml) was added dropwise at an inner temperature between -78 and -71 C. After the addition was complete, the dropping funnel used was rinsed with dry THF (5 ml×2). The resultant homogeneous reaction mixture was stirred at -78 C. for an hour, and then at -10 C. for 50 minutes. The reaction was quenched by adding sat. NH4Cl aq. solution (30.0 ml) below 0 C. The mixture was taken up in AcOEt (500 ml). The AcOEt solution separated was washed with sat. NaCl aq. solution (100 ml×2), dried (MgSO4), and concentrated in vacuo to give a heterogeneous yellow oil (26.51 g). This was, then, diluted with Et2O (250 ml), washed with H2O (×2), and sat. NaCl aq. solution (×1), dried (MgSO4), and concentrated in vacuo to give a homogeneous yellow oil (24.91 g). This was flash chromatographed over SiO2 (Merck Kieselgel 60, 250 g). Elution with n-hexane-AcOEt (40:1/30:1/20:1/10:1) gave title compound (19.73 g, 86.3%) as a viscous pale yellow oil. IRmax (film): 1745(s), 1645(m), 1610(m), 1510(m), 990(shoulder, m), 910(m), 775(m), 745(w), 700(m), 680(m) cm-1 ; 1H-NMR δ: 7.40-7.25(m, 5H), 7.20(d, J=8.8 Hz, 2H), 6.85(d, J=8.8 Hz, 2H), 5.05(s, 1H), 4.84(s, 1H), 4.35(s, 2H), 4.20(d, J=2.6 Hz, 1H), 3.86(s, 2H), 3.80(s, 3H), 3.25(ddd, J=10.5, 5.1, 2.6 Hz, 1H), 2.70(dd, J=15.7, 5.1 Hz, lH), 2.48(dd, J=15.7, 10.7 Hz, 1H), 0.92(s, 9H), 0.21(s, 3H), -0.21(s, 3H) ppm.
