A solution mixture of 3a (0.14 g, 0.5 mmol), 4 (0.18 g, 0.6 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 recrystallization from methanol to afford SLM (0.24 g) as red solid in 56% yield. 1H NMR (400 MHz, DMSO-d6) δ 9.28 (d, J=6.4 Hz, 1H), 9.14 (d, J=8.4 Hz, 1H), 8.86 (s, 1H), 8.51 (d, J=6.4 Hz, 1H), 8.42 (m, 3H), 8.28 (m, 2H), 8.13 (d, J=8.8 Hz, 1H), 8.08 (t, J=7.2 Hz, 1H), 7.80 (d, J=8.8 Hz, 1H), 7.71 (d, J=8.0 Hz, 1H), 7.53 (t, J=8.0 Hz, 1H), 7.32 (t, J=7.2 Hz, 1H), 4.64 (t, J=5.2 Hz, 2H), 4.52 (s, 3H), 3.84 (t, J=5.2 Hz, 2H), 3.48 (m, 2H), 3.33 (m, 2H), 3.11 (s, 3H). 13C NMR (400 MHz, DMSO-d6) δ 153.0, 147, 144.9, 142.1, 140.9, 138.8, 134.9, 129.0, 127.3, 126.7, 126.4, 126.1, 122.8, 122.2, 121.7, 120.4, 119.9, 119.3, 116.2, 115.1, 110.5, 110.4, 71.3, 69.8, 68.9, 58.1, 44.2, 42.9. HRMS (MALDI-TOF) m/z Calcd for C29H29N2O2 437.2223. Found 437.2207 [M+].
