3.2. Synthesis of Compounds 4a–g, 5b–f, 8h–j

Four different methods were employed.

The proper compound 1(10 mmol) was dissolved in methanol (100 mL) and treated with the appropriate aldehyde 2 or 3 (5 mmol) and piperidine (2 mL). The reaction mixture was refluxed for 3–8 h (according to a TLC test), cooled and, if necessary, concentrated at reduced pressure or treated with water (100 mL). The yellow to orange precipitate thus formed was collected by filtration. The compounds were subjected to biological tests after crystallization from ethanol.

Since compounds 8 have an indolinone central core, the same procedure was used for their synthesis, but the stoichiometric ratios have been inverted: 5 mmol of the indolinone 7 and 10 mmol of the appropriate aldehyde 6.

3,3’-((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methaneylylidene))bis(indolin-2-one),4a, Yield 15%; IR (Nujol) ν_max: 1705, 1608, 1224, 733 cm⁻¹; ¹H-NMR (DMSO–d₆): δ 1.26 (9H, s, 3 x CH₃), 6.82 (2H, t, ind, J = 7.6), 6.86 (2H, d, ind, J = 7.6), 7.19 (2H, t, ind, J = 7.6), 7.45 (2H, d, ind, J = 7.6), 7.71 (2H, s, ar), 7.73 (2H, s, CH), 9.88 (1H, broad, OH), 10.56 (2H, s, NH); ¹³C-NMR (DMSO-d₆): 31.10, 34.28, 110.14, 120.86, 121.14, 122.41, 123.10, 127.51, 128.58, 129.99, 132.30, 142.87, 168.65; HRMS: m/z calculated for C₂₈H₂₄N₂NaO₃ [M + Na]⁺: 459.16846. Found: 459.16795; Anal. Calcd. for C₂₈H₂₄N₂O₃ (MW 436,51): C, 77.04; H, 5.54; N, 6.42; Found C, 77.05; H, 5.56; N, 6.39.

3,3’-((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methaneylylidene))bis(5-bromoindolin-2-one),4b, Yield 45%; IR (Nujol) ν_max: 1708, 1607, 1260, 1224 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 1.33 (9H, s, 3 x CH₃), 6.85 (2H, d, ind-7, J = 8.2), 7.40 (2H, dd, ind-6, J = 8.2, J = 2.0), 7.58 (2H, d, ind-4, J = 2.0), 7.77 (2H, s, ar), 7.82 (2H, s, CH), 10.08 (1H, broad, OH), 10.77 (2H, s, NH); ¹³C-NMR (DMSO-d₆): δ 31.48, 34.76, 112.41, 112.99, 123.29, 123.71, 125.05, 127.07, 129.45, 132.57, 134.59, 142.35, 168.57; HRMS: m/z calculated for C₂₈H₂₃Br₂N₂O₃ [M + H]⁺: 593.00754. Found: 595.00656; Anal. Calcd for C₂₈H₂₂Br₂N₂O₃ (MW: 594,30): C, 56.59; H, 3.73; N, 4.71; Found C, 56.57; H, 3.75; N, 4.74.

3,3’-((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methaneylylidene))bis(5-chloroindolin-2-one), 4c, Yield 60%; IR (Nujol) ν_max: 1707, 1607, 1312, 1260 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 1.32 (9H, s, 3 x CH₃), 6.90 (2H, d, ind-7, J = 8.0), 7.28 (2H, dd, ind-6, J = 8.0, J = 2.0), 7.44 (2H, d, ind-4, J = 2.0), 7.77 (2H, s, ar), 7.83 (2H, s, CH), 10.08 (1H, broad, OH), 10.74 (2H, s, NH); ¹³C-NMR (DMSO-d₆): δ 31.00, 34.33, 111.46, 121.93, 122.80, 124.83, 129.15, 134.20, 141.56, 168.29; HRMS: m/z calculated for C₂₈H₂₃Cl₂N₂O₃ [M + H]⁺: 505.10857. Found: 505.10852; Anal. Calcd for C₂₈H₂₂Cl₂N₂O₃ (MW: 505,40): C, 66.54; H, 4.39; N, 5.54; Found C, 66.57; H, 4.36; N, 5.52.

3,3’-((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methaneylylidene))bis(5-hydroxy-1-methylindolin-2-one),4f, Yield 15%; IR (Nujol) ν_max: 1677, 1650, 1595, 1213 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 1.30 (9H, s, 3 x CH₃), 3.17 (6H, s, CH₃), 6.75 (2H, dd, ind-6, J = 8.0, J = 2.4), 6.85 (2H, d, ind-7, J = 8.0), 7.04 (2H, d, ind-4, J = 2.4), 7.75 (2H, s, ar), 7.76 (2H, s, CH), 9.02 (2H, s, OH), 9.92 (1H, s, OH); ¹³C-NMR (DMSO-d₆): δ 25.95, 30.98, 34.31, 108.75, 110.37, 116.16, 121.21, 122.43, 122.95, 127.24, 128.68, 132.52, 136.56, 152.47, 167.06; HRMS: m/z calculated for C₃₀H₂₉N₂O₅ [M + H]⁺: 497.20765. Found: 497.20733; Anal. Calcd for C₃₀H₂₈N₂O₅ (MW: 496,56): C, 72.56; H, 5.68; N, 5.64; Found C, 72.58; H, 5.65; N, 5.63.

3,3’-((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methaneylylidene))bis(1,3-dihydro-2H-benzo[g]indol-2-one),4g, Yield 10%; IR (Nujol) ν_max: 1701, 1614, 1311, 1265 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 1.33 (9H, s, 3 x CH₃), 7.44 (2H, d, ind, J = 8.4), 7.53 (4H, m, ind), 7.64 (2H, d, ind, J = 8.4), 7.85 (2H, s, ar), 7.86 (2H, s, CH), 7.88 (2H, m, ind), 8.15 (2H, m, ind), 10.04 (1H, broad, OH), 10.41 (2H, s, NH); ¹³C-NMR (DMSO-d₆): δ 30.52, 34.25, 114.89, 119.41, 120.31, 122.61, 123.26, 127.01, 128.18, 128.45, 128.89, 132.07, 133.91, 139.99, 169.73; HRMS: m/z calculated for C₃₆H₂₈N₂NaO₃ [M + Na]⁺: 559.19976. Found: 559.19979; Anal. Calcd for C₃₆H₂₈N₂O₃ (MW: 536,63): C, 80.58; H, 5.26; N, 5.22; Found C, 80.59; H, 5.28; N, 5.19.

3,3’-(1,3-phenylenebis(methaneylylidene))bis(5-hydroxyindolin-2-one),5e, Yield 20%; IR (Nujol) ν_max: 1701, 1614, 1311, 1265 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 6.67 (4H, m, ind-6+ind-7), 7.02 (2H, d, ind-4, J = 1.6), 7.62 (2H, s, CH), 7.68 (1H, t, ar, J = 8), 7.79 (1H, d, ar, J = 8), 7.88 (1H, s, ar), 9.04 (2H, s, OH), 10.31 (2H, s, NH); ¹³C-NMR (DMSO-d₆): δ 109.97, 110.63, 117.01, 121.40, 129.02, 129.17, 129.89, 134.61, 13.07, 135.46, 151.87, 168.57; HRMS: m/z calculated for C₂₄H₁₇N₂O₄ [M + H]⁺: 397.11883. Found: 397.11863; Anal. Calcd for C₂₄H₁₆N₂O₄ (MW: 396,40): C, 72.72; H, 4.07; N, 7.07; Found C, 72.70; H, 4.05; N, 7.09.

3,3’-(1,3-phenylenebis(methaneylylidene))bis(5-hydroxy-1-methylindolin-2-one),5f, Yield 30%; IR (Nujol) ν_max: 1678, 1598, 1217, 1118 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 3.15 (6H, s, CH₃), 6.74 (2H, dd, ind-6, J = 8.0, J = 2.0), 6.85 (2H, d, ind-7, J = 8.0), 7.07 (2H, d, ind-4, J = 2.0), 7.69 (1H, t, ar, J = 7.4), 7.72 (2H, s, CH), 7.81 (2H, d, ar, J = 7.4), 7.91 (1H, s, ar), 9.15 (2H, s, OH); HRMS: m/z calculated for C₂₆H₂₁N₂O₄ [M + H]⁺: 425.15013. Found: 425.15010; Anal. Calcd for C₂₆H₂₀N₂O₄ (MW: 424,46): C, 73.57; H, 4.75; N, 6.60; Found C, 73.55; H, 4.76; N, 6.61

3,5-bis((2-chloro-1H-indol-3-yl)methylene)-1,7-dimethyl-5,7-dihydropyrrolo[3,2-f]indole-2,6(1H,3H)-dione,8h, Yield 20%; IR (Nujol) ν_max: 1681, 1604, 1271, 1127 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 3.30 (6H, s, CH₃), 6.38 (1H, s, ar), 6.45 (2H, d, ind, J=7.6), 6.59 (2H, t, ind, J = 7.6), 6.87 (2H, t, ind, J = 7.6), 6.91 (1H, s, ar), 7.15 (2H, d, ind, J = 7.6), 7.37 (2H, s, CH), 12.16 (2H, s, NH); ¹³C-NMR (DMSO-d₆): δ 26.26, 90.52, 106.53, 11.50, 113.74, 119.18, 120.10, 121.50, 122.88, 123.12, 123.98, 126.18, 134.23, 144.53, 168.09, HRMS: m/z calculated for C₃₀H₂₁Cl₂N₄O₂ [M + H]⁺: 539.10416. Found: 539.10237; Anal. Calcd for C₃₀H₂₀Cl₂N₄O₂ (MW: 539,42): C, 66.80; H, 3.74; N, 10.39; Found C, 66.83; H, 3.71; N, 10.38.

3,5-bis((2-chloro-5-hydroxy-1H-indol-3-yl)methylene)-1,7-dimethyl-5,7-dihydropyrrolo[3,2-f]indole-2,6(1H,3H)-dione,8i, Yield 15%; IR (Nujol) ν_max: 1678, 1609, 1273, 1134, 1108 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 3.32 (6H, s, CH₃), 5.82 (2H, d, ind-4, J = 1.9), 6.40 (2H, dd, ind-6, J = 8.8, J = 1.9), 6.47 (1H, s, ar), 6.89 (1H, s, ar), 6.93 (2H, d, ind-7, J = 8.8), 7.38 (2H, s, CH), 8.42 (2H, s, OH), 11.87 (2H, s, NH); ¹³C-NMR (DMSO-d₆): δ 26.25, 90.20, 104.50, 106.09, 11.39, 112.05, 114.09, 123.17, 123.66, 124.20, 125.85, 128.39, 144.02, 151.41, 168.28; HRMS: m/z calculated for C₃₀H₂₁Cl₂N₄O₄ [M + H]⁺: 571.09399. Found: 571.09044; Anal. Calcd for C₃₀H₂₀Cl₂N₄O₄ (MW: 571,41): C, 63.06; H, 3.53; N, 9.81; Found C, 63.08; H, 3.50; N, 9.82.

3,5-bis((2-chloro-1H-benzo[g]indol-3-yl)methylene)-1,7-dimethyl-5,7-dihydropyrrolo[3,2-f]indole-2,6(1H,3H)-dione,8j, Yield 15%; IR (Nujol) ν_max: 1659, 1603, 1269, 1125cm⁻¹; ¹H-NMR (DMSO-d₆): δ 3.33 (6H, s, CH₃), 6.69 (2H, d, ind, J = 8), 6.89 (1H, s, ar,), 6.94 (1H, s, ar,), 7.03 (2H, d, ind, J = 8), 7.35 (2H, t, ind, J = 8), 7.43 (2H, s, CH), 7.47 (2H, t, ind, J = 8), 7.61 (2H, d, ind, J = 8), 7.78 (2H, d, ind, J = 8), 12.03 (2H, s, NH); ¹³C-NMR (DMSO-d₆): δ 26.33, 108.18, 113.72, 119.44, 119.60, 119.96, 120.34, 120.82, 123.01, 123.39, 123.69, 124.12, 125.48, 127.60, 129.18, 129.21, 144.76, 168.21; HRMS: m/z calculated for C₃₈H₂₅Cl₂N₄O₂ [M + H]⁺: 639.13546. Found: 639.13362; Anal. Calcd for C₃₈H₂₄Cl₂N₄O₂ (MW: 639,54): C, 71.37; H, 3.78; N, 8.76; Found C, 71.33; H, 3.80; N, 8.78

The appropriate oxindole 1 (10 mmol) was dissolved in ethanol (100 mL) and treated with the aldehyde 2 (5 mmol) and 37% hydrochloric acid (1 mL). The reaction mixture was refluxed for 2-4 h (according to a TLC test) and cooled. The yellow to orange precipitates thus formed were collected by filtration. The crude products were purified by crystallization with ethanol (4d) or were treated with diethyl ether (4e) to give the desired products.

3,3’-((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methaneylylidene))bis(5-chloro-1-methylindolin-2-one),4d, Yield 25%; IR (Nujol) ν_max: 1706, 1603, 1268, 1108 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 3.21 (6H, s, CH₃), 7.11 (2H, d, ind-7, J = 8.0), 7.31 (2H, d, ind-4, J = 2.0), 7.38 (2H, dd, ind-6, J = 8.0, J = 2.0), 7.75 (1H, t, ar, J = 8.4), 7.83 (2H, d, ar, J = 8.4), 7.85 (2H, s, CH), 7.92 (1H, s, ar); ¹³C-NMR (DMSO-d₆): δ 26.11, 30.92, 34.33, 110.34, 121.69, 122.03, 122.77, 125.52, 125.85, 129.19. 129.28, 134.69, 142.72, 166.81; HRMS: m/z calculated for C₃₀H₂₇Cl₂N₂O₃ [M + H]⁺: 533.13987. Found: 533.13988; Anal. Calcd for C₃₀H₂₆Cl₂N₂O₃ (MW: 533,45): C, 67.55; H, 4.91; N, 5.25; Found C, 67.56; H, 4.93; N, 5.22

3,3’-((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methaneylylidene))bis(6-hydroxyindolin-2-one),4e, Yield 15%; IR (Nujol) ν_max: 1693, 1614, 1259, 1198 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 1.31 (9H, s, 3 x CH₃), 6.66 (4H, m, ind-4 + ind-6), 7.00 (2H, s, ar), 7.69 (2H, s, ind-7), 7.74 (2H, s, CH), 8.91 (2H, s, OH), 9.82 (1H, s, OH), 10.27(2H, s, NH); HRMS: m/z calculated for C₂₈H₂₄N₂NaO₅ [M + Na]⁺: 491.15829. Found: 491.15760; Anal. Calcd for C₂₈H₂₄N₂O₅ (MW: 468,51): C, 71.78; H, 5.16; N, 5.98; Found C, 71.76; H, 5.17; N, 5.99.

The 5-bromoindolin-2-one 1b (10 mmol) was dissolved in acetic acid (50 mL) and treated with isophthaldehyde 3 (5 mmol) and 37% hydrochloric acid (1 mL). The reaction mixture was refluxed for 4 h and the solid separated on cooling was collected by filtration. The crude product was purified by crystallization with ethanol.

3,3’-(1,3-phenylenebis(methaneylylidene))bis(5-bromoindolin-2-one),5b, Yield 10%; IR (Nujol) ν_max: 1712, 1611, 1306, 810 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 6.81 (2H, d, ind-7, J = 8.4), 7.36 (2H, dd, ind-6, J = 8.4, J = 1.9), 7.39 (2H, d, ind-4, J = 1.9), 7.70 (3H, m, 1ar + CH), 7.78 (2H, d, ar, J = 6.8), 7.88 (1H, s, ar), 10.76 (2H, s, NH); HRMS: m/z calculated for C₂₄H₁₅Br₂N₂O₂ [M + H]⁺: 520.95003. Found: 522.94752; Anal. Calcd for C₂₄H₁₄Br₂N₂O₂ (MW: 522,20): C, 55.20; H, 2.70; N, 5.36; Found C, 55.18; H, 2.71; N, 5.35.

Isophthaldehyde 3 (5 mmol) was dissolved in toluene (75 mL) and treated with the appropriate oxindole 1 (10 mmol) in the presence of 4-toluenesulfonic acid (0.5 mmol). The reaction mixture was refluxed for 1 h, and after cooling, the precipitate formed was collected by filtration. The crude derivatives were crystallized from ethanol (5c) or toluene (5d).

3,3’-(1,3-phenylenebis(methaneylylidene))bis(5-chloroindolin-2-one),5c, Yield 30%; IR (Nujol) ν_max: 1735, 1713, 1690, 800 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 6.85 (2H, d, ind-7, J = 8), 7.23 (2H, m, ind-4), 7.25(2H, m, ind-6), 7.71 (1H, m, ar), 7.73 (2H, s, CH), 7.79 (2H, d, ar, J = 8), 7.88 (1H, s, ar), 10.75 (2H, s, NH); HRMS: m/z calculated for C₂₄H₁₄Cl₂N₂NaO₂ [M + Na]⁺: 455.03300. Found: 455.03226; Anal. Calcd for C₂₄H₁₄Cl₂N₂O₂ (MW: 433,29): C, 66.53; H, 3.26; N, 6.47; Found C, 66.55; H, 3.27; N, 6.43.

3,3’-(1,3-phenylenebis(methaneylylidene))bis(5-chloro-1-methylindolin-2-one),5d, Yield 60%; IR (Nujol) ν_max: 1725, 1607, 1109, 796 cm⁻¹; ¹H-NMR (DMSO-d₆): δ 3.21 (6H, s, CH₃), 7.09(2H, d, ind-7, J = 8.0), 7.31 (2H, d, ind-4, J = 2.0), 7.38 (2H, dd, ind-6, J = 8.0, J = 2.0), 7.75 (1H, t, ar, J = 8.4), 7.83 (2H, d, ar, J = 8.4), 7.85 (2H, s, CH), 7.92 (1H, s, ar); HRMS: m/z calculated for C₂₆H₁₉Cl₂N₂O₂ [M + H]⁺: 461.08236. Found: 461.08213; Anal. Calcd for C₂₆H₁₈Cl₂N₂O₂ (MW: 461,34): C, 67.69; H, 3.93; N, 6.07; Found C, 67.67; H, 3.95; N, 6.08.