Reaction Steps
Prepared according to the general procedure from 2-chloro-hydrocinnamaldehyde and (E)-ethyl 4-cyclohexyl-2-oxobut-3-enoate using 2 mol % 1 as the catalyst in 85% yield as a single diastereomer (colorless oil). [α]D20 (c 1.20, CHCl3)=+83.5; 1H NMR (400 MHz, CDCl3) δ 7.33-7.21 (m, 5H), 6.48 (d, 1H, J=6.5 Hz), 4.30 (dq, 1H, J=7.2, 1.8 Hz), 3.38 (dd, 1H, J=14.3, 5.7 Hz), 2.97-2.91 (m, 1H), 2.77 (dd, 1H, J=14.3, 9.1 Hz), 2.45-2.41 (m, 1H), 1.76-1.62 (m, 5H), 1.47-1.44 (m, 1H), 1.34 (t, 3H, J=7.2 Hz), 1.27-1.06 (m, 4H), 0.93-0.89 (m, 1H); 13C NMR (100 MHz, CDCl3) δ 170.4, 160.7, 142.8, 138.6, 128.9, 126.9, 117.6, 62.0, 43.0, 39.4, 37.7, 31.7, 31.4, 27.2, 26.8, 26.1, 14.3; IR (thin film) ν 3520, 3086, 3028, 2981, 2928, 2853, 1770, 1731, 1660, 1453, 1369, 1309, 1262, 1120, 1094, 1013 cm−1; HRMS (ESI) calcd for C21H26O4 [M+Na]+ 365.1723, found 365.1721; 95% ee (4S,5S)-isomer as determined by HPLC (AS-H, 20:1 hexanes/i-PrOH), tr (4S,5S)=19.1 min, tr (4R,5R)=15.7 min.
