[NH2:1][C:2]1[C:7]([NH2:8])=[CH:6][CH:5]=[CH:4][C:3]=1[CH3:9].[C:10](O)(=O)/[CH:11]=[CH:12]/[C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1.[OH-].[Na+]>O>[CH3:9][C:3]1[C:2]2[N:1]=[C:10](/[CH:11]=[CH:12]/[C:13]3[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=3)[NH:8][C:7]=2[CH:6]=[CH:5][CH:4]=1A mixture of 2,3-diaminotoluene (2.44 g, 20 mmol), (E)-cinnamic acid (2.96 g, 20 mmol) and polyphosphoric acid (10 g) was heated to 180° C. for 90 min. The hot mixture was poured into water (100 ml), basified with 50% aqueous solution of sodium hydroxide and extracted with dichloromethane (3×100 ml). The combined extracts were washed with water (100 ml) and brine (100 ml), dried (magnesium sulfate) and concentrated to dryness. Purification by column chromatography (silica gel, 300 g; n-hexane/ethyl acetate (7/3)) yielded 0.61 g (13%) of the titled compound as red solids. 1H-NMR (CDCl3) δ: 9.53 (1H, br.s), 8.72-8.67 (1H, m), 7.95 (1H ddd, J=7.7, 7.7, 1.8 Hz), 7.60-7.49 (3H, m), 7.43-7.31 (3H, m), 7.23-7.14 (3H, m), 7.09-7.04 (1H, m), 2.63 (3H, br.s)
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