All commercially available chemicals were reagent grade and bought from Aladdin Reagent Co., LTD (Shanghai, China); NBT/BCIP kit was bought from Tiangen Biochemical Technology Co., LTD (Shanghai, China); AnnexinV-FITC apoptosis detection kit was bought from Nanjing KGI Biotechnology Development Co., Ltd. (Nanjing, China); The spectra such as NMR, MS, and IR were all evaluated and recorded on a Bruker DRX-400 (1H: 400 MHz, 13C: 100 MHz) (Rheinstetten, Germany), a Thermo Fisher LCQ Fleet (ESI) instrument (Waltham, MA, USA), and FT-IR Thermo Nicolet Avatar 360 using a KBr pellet (Waltham, MA, USA). And the melting points were measured by the XT-4 A melting point apparatus (Shanghai, China) without correction. Other instruments include BD FACSAria II Flow cytometer (Franklin Lakes, NJ, USA), MCO96 carbon dioxide incubator (Osaka, Japan) and Bio Tek EL × 800 microplate reader (Winooski, VT, USA), etc.
3.1. Synthesis Methods
3.1.1. Synthesis of N-phenyl-o-aminobenzoic acid (1) and 9-chlorine acridine (2)
The synthesis of N-phenyl-o-aminobenzoic acid (
1) and 9-chlorine acridine (
2) was carried out according to our previously published procedure, with slight modifications [
24]. Compound
1 could proceed to the next step without further purification.
2-methoxyl-9-chlorine acridine (2a): Yellow-green needle crystal, yield 85.2%, m.p. 158–159 °C. ESI-MS m/z: 244 ([M + H]+); 1H NMR (CDCl3, 400 MHz) 8.00 (dd, 2H, J = 8.00, ArH), 7.93 (d, 2H, J = 8.20, ArH), 7.55–7.60 (m, 2H, ArH), 7.50 (d, 1H, J = 8.40, ArH), 7.30 (s, 1H, ArH), and 3.73 (s, 3H, -OCH3).
2-methyl-9-chlorine acridine (2b): Pale green needle crystal, yield 78.5%, m.p. 122–123 °C. ESI-MS m/z: 228 ([M + H])+ 1H NMR (CDCl3, 400 MHz), δ: 8.05 (dd, 2H, J = 8.00, ArH), 8.00 (d, 2H, J = 9.20, ArH), 7.61–7.68 (m, 2H, ArH), 7.50 (d, 1H, J = 5.40, ArH), 7.43 (s, 1H, ArH), 2.35 (s, 3H, -CH3).
3.1.2. Synthesis of 9-acridinyl Isothiocyanate (3)
To a solution of chlorine acridine 2 (5 mmol) in acetone (50 mL), NaSCN (0.81 g, 10 mmol) and tetrabutylammonium bromide (0.32 g, 1 mmol) were added, and the mixture was then refluxed at 60 °C for 1 h. After cooling to room temperature, crystals of 3a were immediately precipitated in the reaction mixture, and crystals of 3b were precipitated in an ice bath. At the end of the procedure, the crystals were filtered, washed with water, and dried under vacuum, and no further purification was carried out.
2-methoxyl-9-acridinyl isothiocyanate (3a): bright yellow crystal, yield 88.0%, m.p. 149–150 °C; ESI-MS m/z: 267 ([M + H]+); 1H NMR (CDCl3, 400 MHz), δ: 8.25 (d, 2H, J = 8.50, ArH), 8.15 (d, 1H, J = 9.20, ArH), 7.77–7.81 (q, 1H, ArH), 7.66–7.68 (t, 1H, ArH), 7.51 (d, 1H, J = 8.00, ArH), 7.40 (s, 1H, ArH), 4.08(s, 3H, -OCH3); 13C NMR (CDCl3, 100 MHz) δ: 158.66, 130.48, 127.54, 127.04, 123.48, 122.62, 122.28, 98.50, 55.90; IR (KBr) ν: 2967, 2098 (-N=C=S), 1356–1557 cm−1.
2-methyl-9-acridinyl isothiocyanate (3b): faint yellow needle crystal, yield 94%, m.p. 128–129 °C; ESI-MS m/z: 351 ([M + H]+); 1H NMR (CDCl3, 400 MHz), δ: 8.26–8.28 (m, 2H, ArH), 8.15 (d, 1H, J = 8.40 Hz, ArH), 8.04 (s, 1H, ArH), 7.83 (t, 1H, ArH), 7.64–7.70 (m, 2H, ArH), 7.40 (s, 1H, ArH), 2.67 (s, 3H, -CH3); 13C NMR (CDCl3, 100 M Hz) δ: 137.59, 130.46, 127.08, 125.21, 122.92, 122.21, 121.17, 22.12; IR (KBr) ν: 2903, 2143 (-N=C=S), 1411–1630 cm−1.
3.1.3. General Procedure for the Synthesis of Acridinyl Aroyl Thiourea Derivatives 4a–4f
To a solution of 9-isothiocyanatoacridine 3 (2mmol) in absolute ethyl alcohol (60 mL), the appropriate substituted hydrazides (2 mmol) were added, and the reaction mixture was refluxed until the reactants had been consumed (monitored by TLC). The precipitate of 4a–4f was prepared, filtered off, washed with 95% ethyl alcohol, and dried at room temperature.
1-2′-methoxyl acridinyl-3-4′-pyridinamide thiourea (4a): Yellow powder, Yield 91%, m.p. 200–206 °C; ESI-MS m/z: 404 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 11.26 (br, s, 1H, -NH), 10.41 (br, s, 1H, -NH), 10.22 (br, s, 1H, -NH), 8.80 (s, 1H, ArH), 8.05–8.15 (m, 2H, ArH), 7.93 (s, 1H, ArH), 7.77 (t, 1H, ArH), 7.63 (t, 1H, ArH), 8.15 (d, 1H, J = 8.40 Hz, ArH), 8.04 (s, 1H, ArH), 7.83 (t, 1H, ArH), 7.53 (d, 1H, J = 9.20 Hz, ArH), 7.45 (s, 1H, ArH), 4.02 (s, 3H, -OCH3); 13C NMR (DMSO-d6, 100 MHz) δ: 183.19, 167.30, 165.41, 158.40, 150.74, 148.72, 141.00, 139.61, 131.03, 129.59, 125.82, 122.40, 113.46, 109.76, 56.09; IR (KBr) ν: 3108, 2948 (N–H), 1695 (-C=O), 1291 (-C=S) cm−1.
1-2′-methoxyl acridinyl-3-benzoyl thiosemicarbazides (4b): Yellow powder, Yield 76%, m.p. 190–192 °C; ESI-MS m/z: 403 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 10.96 (br, s, 1H, -NH), 10.40 (br, s, 1H, -NH), 10.10 (br, s, 1H, -NH), 8.01–8.14 (m, 4H, ArH), 7.76 (s, 2H, ArH), 7.52–7.58 (m, 6H, ArH), 4.02 (s, 3H, -OCH3); 13C NMR (101 MHz, DMSO-d6) δ: 183.14, 166.84, 164.80, 157.06, 156.21, 144.80, 141.24, 139.31, 132.72, 129.80, 128.80, 127.28, 125.95, 122.46, 122.11, 112.10, 111.51, 56.22; IR (KBr) ν: 3102, 2941 (-N—H), 1686 (-C=O), 1289 (-C=S) cm−1.
1-2′-methoxyl acridinyl-3-4′-methoxy benzoyl thiosemicarbazides (4c): Yellow powder, Yield 87%, m.p. 202–203 °C; ESI-MS m/z: 455 ([M + Na]+); 1H NMR (400 MHz, DMSO-d6), δ: 10.81 (br, s, 1H, -NH), 10.37 (br, s, 1H, -NH), 10.04 (br, s, 1H, -NH), 8.02–8.09 (m, 4H, ArH), 7.32–7.87 (m, 6H, ArH), 7.06 (s, 1H, ArH), 3.82 (s, 3H, -OCH3), 3.32 (s, 3H, -OCH3); 13C NMR (101 MHz, DMSO-d6) δ: 182.97, 166.60, 162.03, 156.30, 153.82, 140.77, 136.15, 132.16, 129.58, 128.77, 127.25, 125.82, 121.52, 111.00, 108.32, 55.90; IR (KBr) ν: 3107, 2945 (-N—H), 1677 (-C=O), 1256 (-C=S) cm−1.
1-2’-methoxyl acridinyl-3-4′-nitro benzoyl thiosemicarbazides (4d): Yellow powder, Yield 94%, m.p. 223–227 °C; ESI-MS m/z: 448 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 11.30 (br, s, 1H, -NH), 10.45 (br, s, 1H, -NH), 10.22 (br, s, 1H, -NH), 8.38 (s, 2H, ArH), 8.26 (s, 2H, ArH), 8.02–8.16 (m, 2H, ArH), 7.53-7.63 (m, 4H, ArH), 7.46 (s, 1H, ArH), 4.02 (s, 3H, -OCH3); 13C NMR (101 MHz, DMSO-d6) δ: 183.22, 167.59, 162.87, 157.42, 149.87, 147.71, 146.73, 140.26, 138.66, 131.49, 131.11, 129.64, 125.67, 124.67, 124.15, 123.98, 117.74, 110.08, 100.87, 56.20; IR (KBr) ν: 3105, 2947 (-N—H), 1697 (-C=O), 1527 (-C=S) cm−1.
1-2’-methoxyl acridinyl-3-4’-nitro benzoyl thiosemicarbazides (4d): Yellow powder, Yield 94%, m.p. 223–227 °C; ESI-MS m/z: 448 ([M+H]+); 1H NMR (400 MHz, DMSO-d6), δ: 11.30 (br, s, 1H, -NH), 10.45 (br, s, 1H, -NH), 10.22 (br, s, 1H, -NH), 8.38 (s, 2H, ArH), 8.26 (s, 2H, ArH), 8.02-8.16 (m, 2H, ArH), 7.53–7.63 (m, 4H, ArH), 7.46 (s, 1H, ArH), 4.02 (s, 3H, -OCH3); 13C NMR (101 MHz, DMSO-d6) δ: 183.22, 167.59, 162.87, 157.42, 149.87, 147.71, 146.73, 140.26, 138.66, 131.49, 131.11, 129.64, 125.67, 124.67, 124.15, 123.98, 117.74, 110.08, 100.87, 56.20; IR (KBr) ν: 3105, 2947 (-N—H), 1697 (-C=O), 1527 (-C=S) cm−1.
1-2′-methyl acridinyl-3-4′-pyridinamide thiourea (4f): Orange powder, Yield 82%, m.p. 176–180 °C; ESI-MS m/z: 410 ([M + Na]+); 1H NMR (400 MHz, DMSO-d6), δ: 11.59 (br, s, 1H, -NH), 10.99 (br, s, 1H, -NH), 10.21 (br, s, 1H, -NH), 8.81 (s, 2H, ArH), 7.89 (s, 3H, ArH), 7.42–7.89 (m, 6H, ArH), 2.33 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6) δ: 183.47, 167.14, 155.61, 150.76, 140.45, 140.16, 138.18, 133.65, 131.24, 126.31, 124.88, 117.52, 111.80, 21.93; IR (KBr) ν: 3104, 2918 (-N—H), 1556 (-C=O), 1471 (-C=S) cm−1.
1-2′-methyl acridinyl-3-benzoyl thiosemicarbazides (4g): Orange powder, Yield 82%, m.p. 171–173 °C; ESI-MS m/z: 409 [M + Na]+; 1H NMR (400 MHz, DMSO-d6), δ: 10.68 (br, s, 1H, -NH), 10.41 (br, s, 1H, -NH), 10.13 (br, s, 1H, -NH), 8.58–8.75 (m, 4H, ArH), 7.42–7.57 (m, 5H, ArH), 7.39 (d, J = 8.5 Hz, 2H, ArH), 7.09 (s, 1H, ArH), 2.42 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6,) δ: 181.29, 166.81, 153.65, 150.24, 148.96, 140.25, 138.24, 133.58, 130.84, 130.35, 126.22, 125.07, 122.13, 121.38, 117.44, 116.40, 111.44, 21.25; IR (KBr) ν: 3102, 2917 (-N—H), 1569 (-C=O), 1471 (-C=S) cm−1.
1-2′-methyl acridinyl-3-4’-methoxy benzoyl thiosemicarbazides (4h): Orange-yellow powder, Yield 93%, m.p. 210–212 °C; ESI-MS m/z: 439 ([M + Na]+); 1H NMR (400 MHz, DMSO-d6), δ: 10.53 (br, s, 1H, -NH), 10.38 (br, s, 1H, -NH), 10.08 (br, s, 1H, -NH), 7.97–8.18 (m, 4H, ArH), 7.34–7.55 (m, 3H, ArH), 7.34–7.55 (m, 3H, ArH), 7.07 (s, 1H, ArH), 3.44 (s, 3H, -OCH3), 2.42 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6) δ: 181.09, 166.30, 153.39, 148.81, 140.15, 138.18, 130.79, 130.04, 126.17, 125.32, 121.21, 117.39, 114.12, 111.37, 55.89, 22.24; IR (KBr) ν: 3094, 2914 (-N—H), 1556 (-C=O), 1471 (-C=S) cm−1.
1-2′-methyl acridinyl-3-4’-nitro benzoyl thiosemicarbazides (4i): Orange-yellow powder, Yield 73%, m.p. 187–188 °C; ESI-MS m/z: 457 ([M + Na]+); 1H NMR (400 MHz, DMSO-d6), δ: 11.56 (br, s, 1H, -NH), 10.76 (br, s, 1H, -NH), 10.15 (br, s, 1H, -NH), 8.41 (d, J = 8.5 Hz, 2H), 7.96–8.26 (m, 4H, ArH), 7.26–7.57 (m, 4H, ArH), 7.11 (s, 1H, ArH), 2.44 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6) δ: 183.42, 166.78, 155.67, 149.20, 140.24, 140.14, 131.87, 130.89, 130.41, 124.68, 117.93, 111.56, 22.50; IR (KBr) ν: 3095, 2918 (-N—H), 1598 (-C=O), 1483 (-C=S) cm−1.
1-2′-methyl acridinyl-3-4′-chloro benzoyl thiosemicarbazides (4j): Orange-yellow powder, Yield 86%, m.p. 178–179 °C; ESI-MS m/z: 443 ([M + Na]+); 1H NMR (400 MHz, DMSO-d6), δ: 10.77 (br, s, 1H, -NH), 10.48 (br, s, 1H, -NH), 10.08 (br, s, 1H, -NH), 8.18–8.34 (m, 4H, ArH), 7.57–7.83 (m, 3H, ArH), 7.33–7.57 (m, 3H, ArH), 7.07 (s, 1H, ArH), 2.42 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6) δ: 182.61, 166.39, 155.38, 149.09, 140.26, 139.92, 131.03, 130.08, 129.29, 124.20, 117.53, 116.31, 111.58, 104.34, 22.83; IR (KBr) ν: 3094, 2915 (-N—H), 1567 (-C=O), 1480 (-C=S) cm−1.
3.1.4. General Procedure for the Synthesis of Acridinyl 1,2,4-triazole Derivatives 5a–5f
The appropriate acyl thiosemicarbazides (4a–4i, 1 mmol) and 5% aqueous sodium carbonate (40 mL) were refluxed for 5 h. After cooling, the precipitate was filtered off and the filtrate was acidified by hydrochloric acid to a pH of 2. The precipitates were formed, filtered off and then crystallized from ethyl alcohol.
4-(2-methoxyacridin-9-yl)-5-(pyridin-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5a): Light yellow powder, Yield 75%, m.p. 272–273 °C; ESI-MS m/z: 384 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 14.79 (br, s, 1H, -NH), 8.38 (dd, J = 4.6, 1.5 Hz, 2H, ArH), 8.33–8.11 (m, 2H, ArH), 7.94–7.76 (m, 1H, ArH), 7.08 (dd, J = 4.6, 1.6 Hz, 2H, ArH), 6.87 (d, J = 2.6 Hz, 1H), 3.86 (s, 3H, -OCH3); 13C NMR (100 MHz, DMSO-d6) δ: 169.99, 159.21, 157.94, 150.89, 149.46, 134.90, 130.31, 129.15, 126.69, 125.10, 124.89, 120.97, 56.52; IR (KBr) ν: 3069, 2906, 2745 (-N—H), 1505–1633 (-C=N),1480 (-C=S) cm−1.
4-(2-methoxyacridin-9-yl)-5-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (5b): Light yellow powder, 60%, m.p. 259–261 °C; ESI-MS m/z: 385 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 14.56 (s, 1H, -NH), 8.22 (dd, J = 12.2, 9.1 Hz, 2H, ArH), 7.89–7.75 (m, 1H, ArH), 7.70–7.58 (m, 2H, ArH), 7.56 (d, J = 8.6 Hz, 1H, ArH), 7.26 (t, J = 6.6 Hz, 1H, ArH), 7.21–7.07 (m, 4H, ArH), 6.82 (d, J = 2.6 Hz, 1H, ArH), 3.85 (s, 3H, -OCH3); 13C NMR (100 MHz, DMSO-d6) δ: 169.50, 159.01, 151.69, 147.45, 146.68, 132.13, 131.27, 130.24, 130.13, 129.26, 128.94, 127.42, 126.58, 125.76, 124.95, 123.68, 122.58, 98.59, 56.44; IR (KBr) ν: 3056, 2912, 2749 (-N—H), 1500–1632 (-C=N), 1476 (-C=S) cm−1.
4-(2-methoxyacridin-9-yl)-5-(4-methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5c): Light yellow powder, Yield 58%, m.p. 262–267 °C; ESI-MS m/z: 415 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 14.45 (s, 1H, -NH), 8.23 (dd, J = 11.8, 9.1 Hz, 2H, ArH), 7.93–7.73 (m, 1H, ArH), 7.64 (s, 2H, ArH), 7.54 (s, 1H, ArH), 7.08 (d, J = 8.9 Hz, 2H, ArH), 6.80 (s, 1H, ArH), 6.70 (d, J = 8.9 Hz, 2H, ArH), 3.85 (s, 3H, -OCH3), 3.58 (s, 3H, -OCH3); 13C NMR (100 MHz, DMSO-d6) δ: 169.30, 161.33, 159.01, 151.58, 147.51, 146.73, 134.08, 132.17, 130.20, 128.95, 126.56, 125.02, 123.76, 122.59, 117.89, 114.76, 98.57, 56.41, 55.60; IR (KBr) ν: 3066, 2883, 2726 (N—H), 1500–1632 (C=N), 1476 (C=S) cm−1.
4-(2-methoxyacridin-9-yl)-5-(4-nitrophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5d): Light yellow powder, Yield 40%, m.p. 253–255 °C; ESI-MS m/z: 430 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 14.79 (s, 1H, -NH), 8.24 (t, J = 9.3 Hz, 2H, ArH), 8.02 (d, J = 8.9 Hz, 2H, ArH), 7.93–7.75 (m, 1H, ArH), 7.63 (dd, J = 9.5, 2.7 Hz, 2H, ArH), 7.58 (s, 1H, ArH), 7.44 (d, J = 8.9 Hz, 2H, ArH), 6.91 (s, 1H, ArH), 3.87 (s, 3H, -OCH3); 13C NMR (100 MHz, DMSO-d6) δ: 170.00, 159.22, 149.93, 148.90, 147.47, 146.78, 133.20, 132.22, 131.44, 130.25, 129.15, 128.69, 126.70, 124.93, 124.61, 123.51, 122.38, 98.64, 56.54; IR (KBr) ν: 3066, 2883, 2726 (-N—H), 1421–1633 (-C=N), 1345 (-C=S) cm−1.
4-(4-chlorophenyl)-4-(2-methoxyacridin-9-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5e): Light yellow powder, Yield 78%, m.p. 286–287 °C; ESI-MS m/z: 419 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 14.61 (s, 1H, -NH), 8.23 (dd, J = 11.4, 9.2 Hz, 2H, ArH), 7.93–7.76 (m, 1H, ArH), 7.73–7.60 (m, 2H, ArH), 7.55 (d, J = 8.6 Hz, 1H, ArH), 7.25 (d, J = 8.6 Hz, 2H, ArH), 7.17 (d, J = 8.6 Hz, 2H, ArH), 6.85 (s, 1H, ArH), 3.86 (s, 3H, -OCH3); 13C NMR (100 MHz, DMSO-d6) δ: 169.59, 159.10, 150.72, 147.44, 146.71, 136.12, 133.51, 132.17, 130.22, 129.54, 129.11, 126.64, 124.93, 124.62, 123.57, 122.49, 98.61, 56.49; IR (KBr) ν: 3056, 2909, 2748 (-N—H), 1344–1632 (-C=N), 1503 (-C=S) cm−1.
4-(2-methylacridin-9-yl)-5-(pyridin-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5f): Light yellow powder, Yield 48%, m.p. 264–268 °C; ESI-MS m/z: 370 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 14.84 (s, 1H, -NH), 8.37 (d, J = 6.0 Hz, 2H, ArH), 8.29 (d, J = 8.7 Hz, 1H, ArH), 8.23 (d, J = 8.9 Hz, 1H, ArH), 7.96–7.84 (m, 1H, ArH), 7.84–7.74 (m, 1H, ArH), 7.72–7.59 (m, 2H, ArH), 7.50 (s, 1H, ArH), 7.04 (d, J = 6.1 Hz, 2H, ArH), 2.52 (s, 3H, -CH3); 13C NMR (100 MHz, DMSO-d6) δ: 170.32, 150.92, 149.15, 148.75, 148.53, 139.37, 134.60, 134.56, 132.85, 131.15 130.21, 130.00, 129.04, 123.54, 123.40, 122.87, 120.84, 120.70, 56.49; IR (KBr) ν: 3066, 2917, 2757 (-N—H), 1279–1600 (-C=N), 1426 (-C=S) cm−1.
4-(2-methylacridin-9-yl)-5-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (5g): White powder, Yield 78%, m.p. 292–293 °C; ESI-MS m/z: 369 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 14.60 (s, 1H, -NH), 8.26 (d, J = 8.8 Hz, 1H, ArH), 8.20 (d, J = 8.9 Hz, 1H, ArH), 7.90–7.82 (m, 1H, ArH), 7.77 (d, J = 9.0 Hz, 1H, ArH), 7.72–7.56 (m, 2H, ArH), 7.48 (s, 1H, ArH), 7.30–7.17 (m, 1H, ArH), 7.13 (d, J = 4.4 Hz, 4H, ArH), 2.51 (s, 3H, -CH3); 13C NMR (100 MHz, DMSO-d6) δ: 169.73, 151.47, 148.71, 148.47, 139.08, 135.20, 134.51, 131.29, 131.07, 130.11, 129.91, 129.28, 128.83, 127.33, 125.66, 123.71, 123.58, 123.02, 120.86, 22.15; IR (KBr) ν: 3066, 2917, 2757 (-N—H), 1279–1600 (-C=N), 1426 (-C=S) cm−1.
4-(4-methoxyphenyl)-4-(2-methylacridin-9-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5h): White powder, Yield 83%, m.p. 268–269 °C; ESI-MS m/z: 399 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 14.48 (s, 1H, -NH), 8.27 (d, J = 8.8 Hz, 1H), 8.21 (d, J = 8.9 Hz, 1H, ArH), 7.86 (t, 1H, ArH), 7.78 (dd, J = 9.0, 1.5 Hz, 1H, ArH), 7.65 (d, J = 6.5 Hz, 1H, ArH), 7.60 (d, J = 8.5 Hz, 1H, ArH), 7.46 (s, 1H, ArH), 7.05 (d, J = 8.9 Hz, 2H, ArH), 6.68 (d, J = 8.9 Hz, 2H, ArH), 3.57 (s, 3H, -OCH3), 2.52 (s, 3H, -CH3); 13C NMR (100 MHz, DMSO-d6) δ: 169.51, 161.33, 151.35, 148.77, 148.53, 139.05, 135.42, 134.49, 131.06, 130.06, 128.85, 123.71 123.02, 120.86, 117.78, 114.78, 55.61, 22.17; IR (KBr) ν: 3095, 2925, 2750 (-N—H), 1360–1613 (-C=N), 1514 (-C=S) cm−1.
4-(2-methylacridin-9-yl)-5-(4-nitrophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5i): Light yellow powder, Yield 53%, m.p. 245–247 °C; ESI-MS m/z: 414 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 14.79 (s, 1H, -NH), 8.24 (t, J = 9.3 Hz, 2H, ArH), 8.02 (d, J = 8.9 Hz, 2H, ArH), 7.83 (s, 1H, ArH), 7.71–7.59 (m, 2H, ArH), 7.57 (d, J = 8.7 Hz, 1H, ArH), 7.44 (d, J = 8.9 Hz, 2H, ArH), 6.91 (s, H, ArH), 2.51 (s, 3H, -CH3), 13C NMR (100 MHz, DMSO-d6) δ: 169.99, 150.53, 148.55, 139.72, 135.26, 131.39, 130.41, 129.19, 128.69, 126.71, 124.62, 123.78, 123.49, 120.98, 22.19; IR (KBr) ν: 3054, 2918, 2755 (-N—H), 1432-1633 (-C=N), 1376 (-C=S) cm−1.
4-(4-chlorophenyl)-4-(2-methylacridin-9-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5j): Yellow powder, Yield 80%, m.p. 259–263 °C; ESI-MS m/z: 403 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 14.65 (s, 1H, -NH), 8.27 (d, J = 8.8 Hz, 1H, ArH), 8.20 (d, J = 8.9 Hz, 1H, ArH), 7.88 (dd, J = 10.5, 4.0 Hz, 1H, ArH), 7.77 (d, J = 8.8 Hz, 1H, ArH), 7.73–7.57 (m, 2H, ArH), 7.49 (s, 1H, ArH), 7.24 (d, J = 8.5 Hz, 2H, ArH), 7.14 (d, J = 8.5 Hz, 2H, ArH); 13C NMR (100 MHz, DMSO-d6) δ: 169.85, 150.49, 148.74, 148.52, 139.19, 136.15, 134.86, 134.52, 131.08, 130.17, 129.97, 129.55, 129.00, 124.51, 123.56, 122.98, 120.81, 22.15; IR (KBr) ν: 3097, 2933 (-N—H), 1258-1600 (-C=N), 1497 (-C=S) cm−1.
3.1.5. General Procedure for the Synthesis of Acridinyl 1,3,4-thiadiazol Derivatives (6)
About 3 mL of 98% concentrated sulfuric acid was added to a 50 mL round-bottom flask and stirred in an ice bath for 10 min at 0 °C. Then, intermediate 4 (0.5 mmol) was added into the solution in small portions over the course of 1 h. The reaction was continued at room temperature for 24–48 h, and 10 mL pure water was slowly added to reaction mixture in an ice bath. The final product 6 was precipitated, filtered off, washed with water, dried, and crystallized from ethyl alcohol.
7-methoxy-N-(5-(pyridin-4-yl)-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6a): Orange solids, Yield 80%, m.p. 272–275 °C; ESI-MS m/z: 386 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 8.78 (d, J = 5.7 Hz, 2H, ArH), 8.22 (d, J = 8.6 Hz, 1H, ArH), 8.00–7.94 (m, 3H, ArH), 7.90 (d, J = 6.2 Hz, 2H, ArH), 7.75 (dd, J = 9.3, 2.7 Hz, 1H, ArH), 7.58 (s, 1H, ArH), 7.53 (dt, J = 8.3, 4.0 Hz, 1H, ArH), 3.86 (s, 3H, -OCH3); 13C NMR (DMSO-d6, 100 MHz) δ: 156.40, 149.19, 140.03, 135.03, 130.65, 128.43, 127.65, 127.49, 127.29, 126.86, 125.02, 121.72, 119.38, 103.95, 56.20; IR (KBr) ν: 3055, 3011, 2837 (-C—H, -N—H), 1379-1631 (-C=N) cm−1.
7-methoxy-N-(5-phenyl-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6b): Orange- yellow solid, Yield 81%, m.p. 263–265 °C; ESI-MS m/z: 385 ([M + H]+); 1H NMR (400 MHz, DMSO-d6), δ: 8.19 (d, J = 8.7 Hz, 1H, ArH), 7.92 (q, J = 9.3 Hz, 3H, ArH), 7.80 (dd, J = 6.6, 2.9 Hz, 2H, ArH), 7.68 (dd, J = 9.2, 2.7 Hz, 1H, ArH), 7.58 (s, 1H, ArH), 7.54–7.44 (m, 4H, ArH), 3.83 (s, 3H, -OCH3); 13C NMR (101 MHz, DMSO-d6) δ: 156.06, 140.22, 136.58, 134.49, 131.24, 130.46, 129.83, 127.72, 126.95, 126.79, 124.37, 121.59, 120.02, 120.33, 119.26, 116.76, 104.39, 56.03; IR (KBr) ν: 2771 (-C—H, N—H), 1329-1632 (-C=N) cm−1.
7-methoxy-N-(5-(4-methoxyphenyl)-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6c): Orange-red solid, Yield 54%; m.p. 230–232 °C; ESI-MS m/z: 415 ([M + H]+); 1HNMR (400 MHz, DMSO-d6) δ: 8.35 (d, J = 8.5 Hz, 1H, ArH), 8.10 (d, J = 8.1 Hz, 3H, ArH), 8.01 (d, J = 9.8 Hz, 1H, ArH), 7.96 (s, 1H, ArH), 7.91–7.79 (m, 1H, ArH), 7.76–7.55 (m, 3H, ArH), 7.06 (t, J = 9.1 Hz, 1H, ArH), 3.93 (s, 3H, -OCH3), 3.81 (s, 3H, -OCH3); 13C NMR (101 MHz, DMSO-d6) δ: 156.91, 149.55, 144.54, 140.78, 136.88, 135.34, 129.01, 128.50, 126.77, 124.39, 121.00, 116.85, 112.99, 103.39, 103.21, 56.65, 56.17; IR (KBr) ν: 2771 (-C—H, -N—H), 1567 (-C=N) cm−1.
7-methoxy-N-(5-(4-nitrophenyl)-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6d): Orange-red solid, Yield 33%; m.p. 258–260 °C; ESI-MS m/z: 430 ([M + H]+); 1H NMR (DMSO-d6, 400 MHz) δ: 8.32 (d, J = 8.9 Hz, 2H, ArH), 8.29 (d, J = 8.6 Hz, 1H, ArH), 8.04 (dd, J = 6.9, 4.8 Hz, 5H, ArH), 7.81 (dd, J = 9.3, 2.7 Hz, 1H, ArH), 7.61 (dd, J = 8.5, 2.5 Hz, 2H, ArH), 3.89 (s, 3H, -OCH3); 13C NMR (101 MHz, DMSO-d6) δ: 156.85, 148.76, 145.74, 142.43, 139.80, 136.85, 135.92, 135.35, 129.32, 127.93, 126.55, 125.67, 125.01, 121.90, 120.38, 119.60, 117.03, 103.59, 56.32; IR (KBr) ν: 2829 (-C—H, -N—H), 1346-1633 (-C=N) cm−1.
7-methoxy-N-(5-(4-chlorophenyl)-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6e): Orange-yellow solid, Yield 51%; m.p. 203–205 °C; ESI-MS m/z: 419 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 8.21 (d, J = 8.6 Hz, 1H, ArH), 7.94 (d, J = 8.1 Hz, 3H, ArH), 7.82 (s, 2H, ArH), 7.72 (dd, J = 9.2, 2.6 Hz, 1H, ArH), 7.58 (dd, J = 5.9, 2.6 Hz, 3H, ArH), 7.55–7.41 (m, 1H, ArH), 3.85 (s, 3H, -OCH3); 13C NMR (101 MHz, DMSO-d6) δ: 156.36, 140.09, 135.90, 134.8, 129.89, 129.19, 128.58, 128.25, 126.65, 124.87, 121.70, 120.01, 119.45, 116.90, 104.12, 102.60, 56.21; IR (KBr) ν: 2781 (-C—H, -N—H), 1467 (-C=N) cm−1.
7-methyl-N-(5-(pyridin-4-yl)-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6f): Orange-yellow solid, Yield 43%; m.p. 276–278 °C; ESI-MS m/z: 370 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 8.34 (d, J = 8.7 Hz, 2H, ArH), 8.23 (d, J = 8.9 Hz, 1H, ArH), 8.14 (d, J = 8.3 Hz, 1H, ArH), 8.05 (t, J = 9.3 Hz, 3H, ArH), 8.01–7.91 (m, 2H, ArH), 7.88 (s, 1H, ArH), 7.51 (d, J = 8.2 Hz, 1H, ArH), 2.48 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6) δ: 158.09, 155.78, 151.07, 140.54, 135.49, 133.66, 131.53, 127.77, 126.46, 123.78, 121.88, 118.38, 118.11, 116.14, 21.31; IR (KBr) ν: 2824 (-C—H, -N—H), 1347-1600 (-C=N) cm−1.
7-methyl-N-(5-phenyl-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6g): Yellow solid, Yield 56%; m.p. 294–296 °C; ESI-MS m/z: 369 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 8.17 (d, J = 8.5 Hz, 1H, ArH), 8.07 (s, 1H, ArH), 7.97–7.85 (m, 2H, ArH), 7.80 (d, J = 6.9 Hz, 4H, ArH), 7.59-7.49 (m, 3H, ArH), 7.48–7.34 (m, 1H, ArH), 2.45 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6) δ: 160.12, 157.49, 140.60, 138.98, 137.32, 135.07, 133.97, 131.26, 130.45, 129.82, 127.17, 127.15, 125.56, 124.06, 119.50, 119.21, 118.10, 117.00, 21.44; IR (KBr) ν: 2792 (C—H, N—H), 1366-1627 (C=N) cm−1.
7-methyl-N-(5-(4-methoxyphenyl)-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6h): Orange-yellow solid, Yield 84%; m.p. >300 °C; ESI-MS m/z: 399 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 8.33 (d, J = 8.7 Hz, 1H, ArH), 8.18 (s, 1H, ArH), 8.10–8.01 (m, 3H, ArH), 7.98 (d, J = 8.8 Hz, 2H, ArH), 7.91–7.77 (m, 1H, ArH), 7.68 (dd, J = 8.6, 2.3 Hz, 1H, ArH), 7.62 (dd, J = 14.4, 7.9 Hz, 1H, ArH), 7.08 (d, J = 8.7 Hz, 1H, ArH), 2.48 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6) δ: 162.17, 159.02, 140.47, 139.22, 137.04, 136.13, 135.63, 128.91, 127.11, 127.06, 126.92, 126.85, 125.57, 125.06, 120.71, 120.03, 119.59, 118.29, 117.35, 113.02, 56.20, 21.52; IR (KBr) ν: 3090, 2920, 2830 (-C—H, -N—H), 1486-1628 (-C=N) cm−11.
7-methyl-N-(5-(4-nitrophenyl)-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6i): Purple-red solid, Yield 53%; m.p. 224–226 °C; ESI-MS m/z: 414 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 12.17 (s, 1H, -NH), 8.35 (d, J = 8.9 Hz, 2H, ArH), 8.15 (d, J = 8.9 Hz, 2H, ArH), 7.96 (d, J = 5.1 Hz, 2H, ArH), 7.72 (t, J = 7.0 Hz, 1H, ArH), 7.65–7.56 (m, 2H, ArH), 7.54 (d, J = 8.5 Hz, 1H, ArH), 7.18 (t, J = 7.6 Hz, 1H, ArH), 2.35 (s, 3H, -CH3); 13C NMR (100 MHz, DMSO-d6) δ: 165.41, 148.81, 143.72, 140.52, 139.40, 138.81, 136.22, 135.69, 135.63, 127.93, 126.99, 125.65, 125.02, 120.12, 119.72, 118.15, 117.34, 113.14, 21.54; IR (KBr) ν: 2918 (-C—H, -N—H), 1340-1627 (-C=N) cm−1.
7-methyl-N-(5-(4-chlorophenyl)-1,3,4-thiadiazol-2-yl)-10,10a-dihydroacridin-9(8aH)-imine (6j): Orange-yellow solid, Yield 67%, m.p. 258–260 °C; ESI-MS m/z: 403 ([M + H]+); 1H NMR (400 MHz, DMSO-d6) δ: 8.23 (d, J = 8.6 Hz, 1H, ArH), 8.12 (s, 1H, ArH), 8.04–7.93 (m, 2H, ArH), 7.88 (s, 2H, ArH), 7.81 (d, J = 8.5 Hz, 2H, ArH), 7.58 (d, J = 8.5 Hz, 2H, ArH), 7.51 (t, J = 7.5 Hz, 1H, ArH), 2.49 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO-d6) δ: 160.71, 146.36, 140.56, 139.09, 137.87, 135.87, 135.50, 129.89, 129.14, 128.58, 127.04, 125.34, 124.71, 119.72, 119.37, 118.16, 117.13, 21.47; IR (KBr) ν: 2795 (-C—H, -N—H), 1366–1627 (-C=N) cm−1.
3.1.6. Preparation of Single Crystal Compounds 5b and 6d and Their X-ray Single Crystal Diffraction Method
A single crystal of
5b and
6d suitable for X-ray diffraction study was cultivated from 95% ethyl alcohol and N, N-dimethylformamide respectively, by a slow evaporation method at room temperature. All measurements were performed with Mo Kα radiation (λ = 0.7107 Å) on a Brucker SMART 1000 CCD X diffractometer (Billerica, MA, USA). The structure was solved by direct methods with SHELXS-97 [
25] and refined by SHELXL-97 [
26]. All non-hydrogen atoms were refined with anisotropic thermal parameters. The final full-matrix least-squares refinement of
5b gave R = 0.0914, ω = 1/[s
2(Fo
2) + (0.0431
p)
2 + 0.2721
p] where
p = (Fo
2 + 2Fc
2)/3, S = 1.043, (Δ/
σ)
max = 0.237 and (Δ/σ)
min = −0.267 e/Å
3. In addition, the final full-matrix least-squares refinement of
6d gave R = 0.0914, ω = (1/[s
2(Fo
2) + (0.0650
p)
2 + 0.0224
p] where
p = (Fo
2 + 2Fc
2)/3, S = 1.028, (Δ/
σ)
max = 0.236 and (Δ/
σ)
min = −0.197 e/Å
3.