Reaction Steps
A mixture of 41 (1.340 g, 4.44 mmol) in nitromethane (4 ml) was heated a microwave reactor (Biotage Initiator) at 100° C. for 15 min in presence of DBU (0.811 g, 5.328 mmol, 1.2 eq). After cooling to room temperature, the reaction mixture was poured into HCl 1M (10 ml). The product extracted with ethyl acetate (2×15 ml). The organic extracts were collected, dried over Na2SO4 and the solvent removed under reduced pressure. Chromatography on silica gel (7:3 hexanes/ethyl acetate, Rf 0.20) afforded 47 (0.980 g, 2.75 mmol, 62%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 1.37 (3H, t, J 7.6 Hz), 2.79 (1H, dd, J 7.2, 15.2 Hz), 2.86 (1H, dd, J 7.2, 15.2 Hz), 4.07 (1H, quint, J 7.2 Hz), 4.34 (2H, q, J 7.2 Hz), 4.72 (1H, dd, J 7.8, 12.6 Hz), 4.83 (1H, dd, J 6.4, 12.4 Hz), 6.63 (1H, d, J 16 Hz), 7.11 (1H, t, J 7.6 Hz), 7.24-7.26 (2H, m), 7.27-7.36 (2H, m), 7.45 (1H, s), 7.47 (2H, d, J 8.8 Hz), 7.96 (2H, d, J 8.8 Hz). 13C NMR (400 MHz, CDCl3) δ 14.55, 40.67, 40.93, 61.20, 79.50, 119.17, 126.54, 127.53, 128.45, 129.48, 130.98, 138.51, 141.60, 166.30, 168.39. MS (API-ES): m/z found 357 [M+H]+ (100%), HRMS (API-ES) m/z found 357.1344 [M+H]+.
