1-Benzyl-3-((4-hydroxybenzylidene)hydrazono)indolin-2-one (**6c**)

Orange solid (50%) mp = 235–236 ◦C. IR (KBr): νmax (cm−1): 3329 (O-H), 3022 (C-H aliphatic), 1705 (C=O), 1608 (C=N), 1589 (C=N). 1H NMR (DMSO-d6, 600 MHz: δ 4.97 (s, 2H, N-CH2-Ph), 6.92 (d, *J* = 7.8, 2H, ArH), 6.98 (d, *J* = 7.2, 1H, ArH), 7.08 (t, 1H, ArH), 7.22–7.4 (m, 6H, ArH), 7.73 (bs, 1H, OH), 7.86 (d, *J* = 7.2, 2H, ArH), 8.15 (d, *J* = 7.8, 1H, ArH), 8.65 (s, 1H, N=CH) ppm. 13C NMR (DMSO-d6, 150 MHz: δ 164.32, 164.11, 162.32, 150.79, 150.31, 145.17, 136.56, 133.62, 132.08, 129.29, 129.18, 127.96, 127.49, 124.88, 123.49 and 43.14 ppm. ESI mass m/z = 356 [M + H]<sup>+</sup>.
