Reaction Steps
Prepared according to the general procedure from ethyl trans-4-oxo-2-butenoate and trans-N-(4-methoxybenzenesulfonyl)-1-(4-(3-iminoprop-1-enyl)phenyl)ethanone using 10 mol % 9 as the catalyst in 55% yield as a yellow oil. [α]D20 (c 1.22, CHCl3)=+168.2; 1H NMR (400 MHz, CDCl3) δ 8.04 (dd, 2H, J=6.9, 2.1 Hz), 7.59 (dd, 2H, J=6.5, 1.9 Hz), 7.19 (d, 1H, J=8.0 Hz), 7.07 (dd, 2H, J=6.9, 2.1 Hz), 6.69 (dd, 2H, J=6.6, 1.7 Hz), 5.59 (dd, 1H, J=8.0, 6.6 Hz), 4.14-4.11 (m, 2H), 3.95 (s, 3H), 3.74 (t, 1H, J=6.9 Hz), 3.58-3.53 (m, 1H), 2.58 (dd, 1H, J=17.4, 6.0 Hz), 2.52 (s, 3H), 1.90 (dd, 1H, J=17.4, 7.8 Hz), 1.22 (t, 3H, J=7.2 Hz); 13C NMR (100 MHz, CDCl3) δ 197.5, 171.5, 168.6, 164.5, 142.3, 136.6, 131.4, 128.9, 128.2, 125.3, 114.3, 112.7, 94.6, 61.1, 56.1, 43.9, 41.7, 31.4, 26.7, 14.3; IR (thin film) ν 3020, 2983, 2842, 1723, 1682, 1594, 1497, 1363, 1267, 1167, 1091, 1024 cm−1; HRMS (ESI) calcd for C24H25NO7S [M+Na]+ 494.1243, found 494.1265; >99% ee (3S,4S)-isomer as determined by HPLC(OD-H, 4:1 hexanes/i-PrOH), tr (3S,4S)=28.6 min, tr (3R,4R)=35.1 min.
