Reaction Steps
A solution mixture of 6 (0.20 g, 0.8 mmol), 3a (0.33 g, 1.1 mmol) and piperidine (0.1 mL) in ethanol (40 mL) was heated to reflux overnight. After cooling down to room temperature, the organic solvent was removed. The residue was purified by precipitation from methanol and ethyl acetate to afford SLE (0.22 g) in 53% yield.1H NMR (400 MHz, DMSO-d6) δ 9.34 (d, J=8.4 Hz, 1H), 9.15 (d, J=8.4 Hz, 1H), 8.86 (s, 1H), 8.54-8.51 (m, 2H), 8.44 (d, J=16 Hz, 1H), 8.36 (d, J=16 Hz, 1H), 8.28-8.23 (m, 2H), 8.12 (d, J=8.0 Hz, 1H), 8.05 (t, J=7.6 Hz, 1H), 7.77 (d, J=8.4 Hz, 1H), 7.70 (d, J=8.4 Hz, 1H), 7.52 (t, J=7.6 Hz, 1H), 7.31 (t, J=7.6 Hz, 1H), 4.99 (tr, J=6.8 Hz, 2H), 4.63 (t, J=4.8 Hz, 2H), 3.84 (t, J=4.8 Hz, 2H), 3.48 (t, J=4.8 Hz, 2H), 3.31 (t, J=4.8 Hz, 2H), 3.11 (s, 3H), 1.59 (t, J=6.8 Hz, 3H). 13C NMR (400 MHz, DMSO-d6) δ 153.2, 146.7, 145.1, 142.2, 140.9, 137.7, 135.0, 128.9, 127.4, 126.8, 126.7, 126.5, 126.4, 122.8, 122.2, 121.8, 120.4, 119.9, 119.0, 116.2, 115.5, 110.4, 110.3, 71.3, 69.8, 68.9, 58.1, 51.9, 15.1. HRMS (MALDI-TOF) m/z Calcd for C30H31N2O2 451.2380 Found 451.2362 [M]+.
