Reaction Steps
The title compound was prepared according to the general procedure from ethyl trans-4-oxo-2-butenoate and trans-N-(4-methoxybenzenesulfonyl)-3-(4-methoxyphenyl)prop-2-en-1-imine using 10 mol % 9 as the catalyst in 81% yield as a yellow solid. [α]D20 (c 1.04, CHCl3)=+143.6; mp=107-110° C.; 1H NMR (400 MHz, CDCl3) δ 8.03 (dd, 2H, J=7.1, 1.8 Hz), 7.13 (d, 1H, J=8.1 Hz), 7.05 (dd, 2H, J=7.1, 1.8 Hz), 6.55-6.48 (m, 4H), 5.59 (dd, 1H, J=8.0, 6.6 Hz), 4.16-4.09 (m, 2H), 3.92 (s, 3H), 3.71 (s, 3H), 3.60 (t, 1H, J=6.9 Hz), 3.52-3.47 (m, 1H), 2.58 (dd, 1H, J=17.2, 6.0 Hz), 1.95 (dd, 1H, J=17.2, 7.7 Hz), 1.22 (t, 3H, J=7.0 Hz); 13C NMR (100 MHz, CDCl3) δ 171.8, 169.1, 164.3, 159.2, 131.4, 129.2, 128.5, 124.3, 114.3, 114.3, 113.9, 113.6, 61.0, 56.0, 55.3, 44.3, 41.2, 31.5, 14.4; IR (thin film) ν 3055, 2840, 1720, 1647, 1511, 1498, 1463, 1442, 1366, 1263, 1167, 1090, 1028 cm−1; HRMS (ESI) calcd for C23H25NO7S [M+Na]+ 482.1243, found 482.1253; >99% ee (3S,4S)-isomer as determined by HPLC (AS-H, 4:1 hexanes/i-PrOH), tr (3S,4S)=49.3 min, tr (3R,4R)=29.6 min.
