Reaction Steps
To a mixture of (Z)-2-(5-nitro-1H-indol-3-yl)-3-pyridin-3-yl-acrylonitrile (370 mg, 1.27 mmol, 1.0 eq.) in ethanol (40 mL) were added zinc powder (667 mg, 10.2 mmol, 8.0 eq.) and then, ammonium chloride (679 mg, 12.7 mmol, 10.0 eq.). The reaction mixture was stirred at room temperature for 30 minutes and filtered through a celite pad. The filtrate was concentrated under reduced pressure and partitioned between water and ethyl acetate. The organic layer was washed with brine, dried over MgSO4 and evaporated. The residue was purified by silica gel flash-column chromatography (eluent: CH2Cl2/EtOH, 96/4 to 94/6) to afford, after trituration with diethyl ether, the compound (40) as a orange solid (80 mg, 24%). IR νmax (cm−1): 2216 (νCN), 3340 (νN—H); 1H NMR (DMSO, 500 MHz) δ (ppm): 4.72 (2H, s, aniline H), 6.63 (1H, dd, J6′-7′=8.9 Hz, J6′-4′=2.4 Hz, H6′), 7.19 (1H, d, J7′-6′=8.9 Hz, H7′), 7.22 (1H, d, J4′-6′=2.4 Hz, H4′), 7.54 (1H, dd, J5″-4″=7.9 Hz, J5″-6″=4.8 Hz, H5″), 7.59 (1H, s, H3), 7.61 (1H, s, H2′), 8.29 (1H, d, J4″-5″=7.9 Hz, H4″), 8.57 (1H, d, J6″-5″=4.8 Hz, H6″), 8.93 (1H, s, H2″), 11.37 (1H, s, indolic H); 13C NMR (DMSO, 75.5 MHz) δ (ppm): 103.0 (C4′), 109.3 (C2), 109.9 (C3′), 113.2 (C6′), 113.4 (C7′), 118.5 (C1), 124.2 (C5″), 125.1 (C3a′), 127.1 (C2′), 130.9 (C3), 131.1 (C3″), 131.5 (C7a′), 134.7 (C4″), 143.7 (C5′), 149.8 (C6″), 150.2 (C2″); ESI-MS: m/z 261.1 ([M+H]+); HRESI-MS: m/z 261.1153 (calcd for C16H13N4+, 261.1140).
