Reaction Steps
Prepared according to the general procedure using (Z)-4-benzylidene-2-(2,5-difluorophenyl)-1H-imidazol-5(4H)-one and trans-crotonaldehyde. The unpurified residue was purified by flash chromatography using 15% EtOAc/hexanes to afford 18 as an off-white solid (85 mg, 80%). Analytical data for 18: 1H NMR (500 MHz, CDCl3) δ 9.43 (br s, 1H), 7.91 (ddd, J=9.3, 6.1, 3.2 Hz, 1H), 7.37-7.28 (m, 3H), 7.15-7.03 (m, 3H), 7.02-6.93 (m, 1H), 4.31 (d, J=6.9 Hz, 1H), 3.06 (q, J=6.8 Hz, 1H), 1.89-1.78 (m, 1H), 1.31-1.20 (m, 1H), 1.04 (t, J=7.4 Hz, 3H); 13C NMR (CDCl3, 126 MHz) δ 169.0, 159.1 (d, JCF=243.5 Hz), 155.4 (d, JCF=240.5 Hz), 149.3, 137.1, 136.4, 129.2, 128.2, 127.7, 118.5 (dd, JCF=13.1, 9.2 Hz), 117.1 (dd, JCF=25.7, 8.8 Hz), 116.5 (dd, JCF=24.9, 9.5 Hz), 114.5 (dd, JCF=27.0, 4.0 Hz), 110.5 (d, JCF=3.9 Hz), 47.8, 39.1, 20.4, 11.9; IR (film) cm−1 2968, 2933, 2877, 1773, 1763, 1618, 1528, 1482, 1464, 1388, 1174, 1138, 1115, 1089, 1067, 766, 736, 699; LRMS (ESI): Mass calcd for [M+H]+ C20H17F2N2O2: 355.1. found 355.3; Enantiomeric ratio was measured by chiral phase HPLC (Chiralcel OD-H; 15% IPA/hexanes 1.0 mL/min, 280 nm), Rt1=20.2 min (major), Rt2=36.1 min (minor)); er=>99:1.
