Synthesis of Functionalized 9-Substituted Fluorene Derivatives via Boron Trifluoride Catalysed Reaction of Coplanar 9-(Phenylethynyl)-9H-fluoren-9-ols, Aryl Aminoamides and N-Bromosuccinimide

Abstract

A boron trifluoride catalysed reaction of coplanar 9-(phenyl­ethynyl)-9H-fluoren-9-ols with various 2-aminobenzamides affords a number of highly functionalized, conjugated (Z)-2-((2-(9H-fluoren-9-ylidene)-1-phenylethylidene)amino) benzamides in excellent yield. The reaction in the presence of N-bromosuccinimide affords (E)-5-bromo-2-((2-bromo-2-(9H-fluoren-9-ylidene)-1-phenylethylidene)amino)benz­amides in very good yields. The scope of the reaction is demonstrated by selecting N-aryl substituted 2-aminobenzamides and aminosulfonamides as reaction partners. The structures of representative compounds were established by single-crystal XRD analysis. Based on the structure of the products, a plausible mechanism via formation of allene carbocation intermediates is proposed.

Key words

aryl aminoamides - propargylic alcohol - N-bromosuccin­imide - BF₃·OEt₂ - fluorene - allene

Publikationsverlauf

Eingereicht: 16. Mai 2020

Angenommen nach Revision: 03. Januar 2021

Artikel online veröffentlicht:
25. Januar 2021

• References and Notes

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• 28 Synthesis of Compounds 3a–m; General Procedure: To a stirred solution of propargylic alcohol derivative of fluorenone 1 (0.35 mmol, 1equiv) and aminobenzamide 2 (0.35 mmol, 1 equiv) in dichloromethane (5 mL) was added BF₃·OEt₂ (0.1 mmol, 0.3 equiv). The resulting reaction mixture was stirred at room temperature for 5 minutes. After the completion of the reaction (monitored by TLC), the reaction mixture was diluted with dichloromethane, washed with distilled water and saturated brine. The combined organic layers were dried over anhydrous Na₂SO₄, filtered, and the solvent was evaporated under reduced pressure. The crude mixture was purified by silica gel column chromatography (eluent: hexane/EtOAc) to afford the corresponding compounds 3a–m in good yields. Synthesis of Compounds 4a–d; General Procedure: To a solution of propargylic alcohol 1 (0.35 mmol, 1 equiv) and aminobenzamide 2 (0.35 mmol, 1 equiv) in dichloromethane (5 mL) was added NBS (0.4 mmol, 1.2 equiv) followed by BF₃·Et₂O (0.1 mmol, 0.3 equiv) and the reaction mixture was stirred at room temperature. After the completion of the reaction (monitored by TLC), the reaction mixture was diluted with dichloromethane, washed with distilled water and saturated brine. The combined organic layer was dried over anhydrous Na₂SO₄, filtered, and the solvent was evaporated under reduced pressure. The crude mixture was purified by silica gel column chromatography (eluent: hexane/EtOAc) to afford the corresponding compounds 4a–d in good yields. (Z)-2-((2-(9H-Fluoren-9-ylidene)-1-phenylethylidene)amino)benzamide (3a): Yield: 92%; yellow solid; R_f (30% EtOAc–Hexane): 0.45. FTIR (KBr): 3293, 3057, 2922, 2852, 1914, 1810, 1656, 1611, 1487, 1447, 1378, 1289, 1267, 1236, 1158, 1107, 1016, 943, 836, 747, 730, 697, 622 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 8.25 (s, 1 H), 8.13 (dd, J = 7.5, 1.8 Hz, 1 H), 7.98–7.95 (m, 2 H), 7.58–7.53 (m, 2 H), 7.47 (d, J = 7.6 Hz, 1 H), 7.43 (d, J = 7.3 Hz, 1 H), 7.35 (t, J = 7.5 Hz, 2 H), 7.29 (t, J = 7.1 Hz, 1 H), 7.21–7.15 (m, 2 H), 7.10 (ddd, J = 7.5, 4.8, 1.7 Hz, 3 H), 6.92 (t, J = 7.2 Hz, 1 H), 6.85 (s, 1 H), 6.73 (dd, J = 7.6, 1.3 Hz, 1 H), 6.07 (s, 1 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 119.1, 119.9, 120, 120.9, 121.1, 124.7, 125.7, 127.4, 127.5, 128.7, 129.2, 129.6, 129.7, 131.4, 132, 135.5, 137.3, 137.7, 139.9, 141.7, 142.7, 148.6, 166.9, 168.6. HRMS (ESI): m/z [M + H] calcd for C₂₈H₂₁N₂O: 401.1653; found: 401.1652.(Z)-2-((2-(9H-Fluoren-9-ylidene)-1-phenylethylidene)amino)benzenesulfonamide (3b): Yield: 90%; yellow solid; R_f (30% EtOAc–Hexane): 0.47. FTIR (KBr): 3360, 3268, 2923, 1918, 1643, 1604, 1587, 1535, 1445, 1401, 1344, 1276, 1254, 1209, 1171, 1128, 1070, 1024, 942, 857, 833, 807, 772, 730, 689, 620 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 8.06–8.03 (m, 2 H), 8.00 (dd, J = 7.9, 1.4 Hz, 1 H), 7.66 (dd, J = 7.5, 0.8 Hz, 2 H), 7.57 (d, J = 7.6 Hz, 1 H), 7.53–7.48 (m, 1 H), 7.44–7.37 (m, 3 H), 7.32 (ddd, J = 10.2, 8.2, 1.3 Hz, 2 H), 7.27 (dd, J = 2.6, 1.3 Hz, 1 H), 7.25–7.22 (m, 2 H), 7.18–7.14 (m, 1 H), 7.03 (td, J = 7.6, 1.1 Hz, 1 H), 6.97 (s, 1 H), 6.77 (dd, J = 7.9, 1.0 Hz, 1 H), 5.34 (s, 2 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 119.7, 119.9, 120.1, 120.9, 121.5, 124.6, 125.9, 127, 127.4, 127.6, 128.8, 129.2, 129.6, 129.7, 132.3, 132.8, 133.6, 135.8, 137, 137.7, 139.9, 141.9, 142.4, 148.2, 169.5. HRMS (ESI): m/z [M + H] calcd for C₂₇H₂₁N₂O₂S: 437.1323; found: 437.1323.(Z)-2-((2-(9H-Fluoren-9-ylidene)-1-phenylethylidene)amino)-5-iodobenzamide (3c): Yield: 91%; yellow solid; R_f (30% EtOAc–Hexane): 0.50. FTIR (KBr): 3413, 3339, 3149, 2971, 2924, 1670, 1608, 1575, 1495, 1447, 1404, 1350, 1294, 1256, 1211, 1159, 1095, 1018, 951, 918, 862, 813, 780, 733, 698, 663 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 8.46 (d, J = 2.1 Hz, 1 H), 8.19 (s, 1 H), 7.99–7.94 (m, 2 H), 7.57 (dd, J = 11.0, 7.6 Hz, 2 H), 7.51 (d, J = 7.6 Hz, 1 H), 7.48–7.39 (m, 2 H), 7.34 (ddd, J = 10.7, 8.3, 4.3 Hz, 3 H), 7.22 (ddd, J = 7.6, 4.3, 0.9 Hz, 2 H), 7.06 (d, J = 7.7 Hz, 1 H), 6.91 (td, J = 7.7, 0.9 Hz, 1 H), 6.82 (s, 1 H), 6.48 (d, J = 8.4 Hz, 1 H), 5.74 (s, 1 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 89.9, 118.5, 120.0, 120.4, 121.2, 122.8, 125.8, 126.7, 127.5, 127.7, 128.8, 129.3, 129.9, 129.4, 132.4, 135.4, 137.2, 137.6, 140.1, 140.2, 140.7, 141.9, 143.2, 148.1, 166.9, 167.5. HRMS (ESI): m/z [M + H] calcd for C₂₈H₂₀IN₂O: 527.0620; found: 527.0619.(Z)-2-((2-(9H-Fluoren-9-ylidene)-1-phenylethylidene)amino)-N-phenylbenzamide (3d): Yield: 89%; yellow crystals; R_f (10% EtOAc–Hexane): 0.49. FTIR (KBr): 3418, 3114, 3058, 1915, 1710, 1662, 1595, 1537, 1494, 1445, 1401, 1315, 1279, 1249, 1157, 1124, 882, 752, 730, 694, 620 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.75 (s, 1 H), 8.25–8.20 (m, 1 H), 8.05–8.01 (m, 2 H), 7.52 (dd, J = 12.3, 7.5 Hz, 2 H), 7.47–7.36 (m, 6 H), 7.26 (dd, J = 7.5, 0.8 Hz, 1 H), 7.17 (d, J = 2.3 Hz, 1 H), 7.15–7.11 (m, 5 H), 7.08–7.06 (m, 1 H), 6.96–6.92 (m, 1 H), 6.90 (s, 1 H), 6.81–6.76 (m, 2 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 118.8, 120.0, 120.1, 121.0, 121.2, 123.9, 125.9, 126.1, 126.3, 127.4, 127.6, 128.9, 129.0, 129.2, 129.8, 131.6, 131.8, 132.4, 135.4, 137.4, 137.7, 138.7, 140.1, 141.8, 143.1, 147.7, 164.3, 167.3. HRMS (ESI): m/z [M + H] calcd for C₃₄H₂₅N₂O: 477.1966; found: 477.1970.(Z)-2-((2-(9H-Fluoren-9-ylidene)-1-phenylethylidene)amino)-N-(3-bromophenyl)benzamide (3e): Yield: 90%; yellow crystals; R_f (15% EtOAc–Hexane): 0.45. FTIR (KBr): 3649, 3051, 3012, 2971, 2922, 2363, 1942, 1913, 1665, 1589, 1523, 1476, 1446, 1417, 1285, 1249, 1159, 1126, 1064, 994, 956, 913, 877, 768, 726, 697, 674, 621 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.98 (s, 1 H), 8.24–8.21 (m, 1 H), 8.05–8.02 (m, 2 H), 7.57 (d, J = 2.0 Hz, 1 H), 7.54 (d, J = 4.5 Hz, 1 H), 7.53–7.47 (m, 3 H), 7.42 (d, J = 7.2 Hz, 3 H), 7.32–7.28 (m, 1 H), 7.20–7.16 (m, 3 H), 7.15 (d, J = 1.9 Hz, 1 H), 7.06 (d, J = 7.8 Hz, 2 H), 7.00 (t, J = 8.0 Hz, 1 H), 6.90 (s, 1 H), 6.84–6.79 (m, 2 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 118.3, 118.6, 120.0, 120.1, 121.1, 121.2, 122.6, 122.8, 125.8, 125.9, 126.5, 126.7, 127.4, 127.6, 128.8, 129.4, 129.8, 129.9, 130.3, 131.6, 132.1, 132.6, 135.4, 137.4, 137.7, 140.0, 140.1, 141.8, 143.5, 147.6, 164.3, 167.4. HRMS (ESI): m/z [M + 2] calcd for C₃₄H₂₄BrN₂O: 557.1072; found: 557.1060.(Z)-2-((2-(9H-fluoren-9-ylidene)-1-phenylethylidene)amino)-N-(p-toluenesulfonyl)benzamide (3f): Yield: 88%; yellow solid; R_f (15% EtOAc–Hexane): 0.49. FTIR (KBr): 3009, 2919, 1911, 1652, 1593, 1564, 1527, 1446, 1404, 1345, 1314, 1280, 1248, 1177, 1124, 1090, 1019, 881, 849, 812, 767, 729, 696, 621 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.70 (s, 1 H), 8.23 (dd, J = 6.0, 3.5 Hz, 1 H), 8.06–8.03 (m, 2 H), 7.57–7.52 (m, 2 H), 7.48 (t, J = 7.7 Hz, 2 H), 7.39 (d, J = 7.2 Hz, 2 H), 7.31 (dd, J = 14.2, 7.8 Hz, 3 H), 7.20–7.14 (m, 4 H), 7.09 (d, J = 7.8 Hz, 1 H), 6.97 (d, J = 8.3 Hz, 2 H), 6.91 (s, 1 H), 6.81 (ddd, J = 11.9, 6.6, 2.4 Hz, 2 H), 2.20 (s, 3 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 20.9, 118.9, 119.9, 120.0, 120.1, 120.9, 121.2, 125.9, 126.1, 126.3, 127.4, 127.6, 128.9, 129.2, 129.5, 129.7, 129.8, 131.5, 131.8, 132.4, 133.4, 135.5, 136.1, 137.4, 137.8, 140.1, 141.8, 143.1, 147.7, 164.1, 167.1. HRMS (ESI): m/z [M + H] calcd for C₃₅H₂₇N₂O: 491.2123; found: 491.2122.(Z)-2-((2-(9H-Fluoren-9-ylidene)-1-(p-toluenesulfonyl)ethylidene)amino)-N-phenylbenzamide (3g): Yield: 87%; yellow solid; R_f (15% EtOAc–Hexane): 0.49. FTIR (KBr): 3566, 3057, 2921, 2852, 2364, 1718, 1666, 1597, 1561, 1538, 1495, 1446, 1315, 1280, 1247, 1178, 1121, 1036, 824, 776, 753, 730, 692, 621 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.82 (s, 1 H), 8.22 (dd, J = 6.0, 3.5 Hz, 2 H), 7.94 (d, J = 8.2 Hz, 2 H), 7.54 (dd, J = 11.8, 7.5 Hz, 2 H), 7.48 (dd, J = 7.4, 2.4 Hz, 3 H), 7.31–7.27 (m, 1 H), 7.20–7.15 (m, 6 H), 7.14–7.10 (m, 3 H), 6.96 (t, J = 7.4 Hz, 1 H), 6.90 (s, 1 H), 6.84–6.76 (m, 2 H), 2.35 (s, 3 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 21.8, 119.2, 119.9, 120.0, 120.1, 121.1, 123.9, 125.9, 126.0, 126.1, 127.5, 127.6, 128.9, 129.0, 129.7, 129.8, 130.0, 131.5, 131.9, 134.6, 135.5, 137.7, 138.7, 140.0, 141.7, 142.9, 143.1, 147.8, 164.4, 167.1. HRMS (ESI): m/z [M + H] calcd for C₃₅H₂₇N₂O: 491.2123; found: 491.2123.(Z)-2-((2-(9H-Fluoren-9-ylidene)-1-(p-toluenesulfonyl)ethylidene)amino)-N-(3-bromophenyl)benzamide (3h): Yield: 91%; yellow solid; R_f (15% EtOAc–Hexane): 0.49. FTIR (KBr): 3772, 3050, 3009, 2922, 2852, 1938, 1661, 1589, 1553, 1418, 1351, 1313, 1300, 1286, 1251, 1224, 1180, 1158, 1043, 773, 724, 695, 625 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 11.04 (s, 1 H), 8.23–8.20 (m, 1 H), 7.93 (d, J = 8.2 Hz, 2 H), 7.57–7.52 (m, 3 H), 7.49–7.47 (m, 2 H), 7.29 (td, J = 7.5, 0.9 Hz, 1 H), 7.24–7.19 (m, 3 H), 7.17 (s, 1 H), 7.16–7.13 (m, 2 H), 7.10 (s, 1 H), 7.07 (dd, J = 6.5, 1.6 Hz, 1 H), 7.01 (d, J = 7.9 Hz, 1 H), 6.89 (s, 1 H), 6.85–6.80 (m, 2 H), 2.35 (s, 3 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 21.8, 118.4, 118.8, 120.0, 120.1, 121.1, 121.2, 122.6, 122.8, 125.8, 126.0, 126.3, 126.7, 127.4, 127.6, 128.8, 129.8, 129.9, 130.2, 130.4, 131.4, 131.5, 132.1, 134.8, 135.5, 137.8, 140.1, 141.8, 143.2, 143.4, 143.7, 164.4, 167.2. HRMS (ESI): m/z [M + 2] calcd for C₃₅H₂₆BrN₂O: 571.1206; found: 571.1213.(Z)-2-((2-(9H-Fluoren-9-ylidene)-1-(p-toluenesulfonyl)ethylidene)amino)-N-(p-toluenesulfonyl)benzamide (3i): Yield: 88%; yellow solid; R_f (15% EtOAc–Hexane): 0.49. FTIR (KBr): 3465, 3361, 3271, 3171, 3040, 2917, 2854, 2363, 1920, 1715, 1658, 1539, 1512, 1473, 1446, 1405, 1319, 1281, 1246, 1176, 1128, 1089, 1039, 1014, 983, 938, 895, 851, 815, 777, 728, 693, 664, 621 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.75 (s, 1 H), 8.22 (dd, J = 5.9, 3.6 Hz, 1 H), 7.93 (d, J = 8.2 Hz, 2 H), 7.54 (dd, J = 11.7, 7.5 Hz, 2 H), 7.47 (d, J = 7.6 Hz, 1 H), 7.36 (d, J = 8.4 Hz, 2 H), 7.28 (dd, J = 10.9, 4.0 Hz, 1 H), 7.18 (d, J = 8.7 Hz, 2 H), 7.11 (dd, J = 6.1, 3.3 Hz, 3 H), 6.98 (d, J = 8.2 Hz, 2 H), 6.90 (s, 1 H), 6.84–6.79 (m, 1 H), 6.77 (dd, J = 5.9, 3.2 Hz, 1 H), 2.34 (s, 3 H), 2.20 (s, 3 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 21.0, 21.8, 119.3, 119.9, 120.0, 121.0, 121.1, 125.9, 126.0, 127.4, 127.5, 128.9, 129.5, 129.7, 130.0, 131.4, 131.7, 133.4, 135.5, 136.2, 137.7, 140.0, 141.7, 142.8, 143.0, 147.8, 164.2, 170.0. HRMS (ESI): m/z [M + H] calcd for C₃₆H₂₉N₂O: 505.2279; found: 505.2273.(Z)-2-((2-(9H-Fluoren-9-ylidene)-1-(p-toluenesulfonyl)ethylidene)amino)-N-(3,5-dimethylphenyl)benzamide (3j): Yield: 75%; yellow solid; R_f (15% EtOAc–Hexane): 0.49. FTIR (KBr): 3163, 3057, 2961, 3919, 2850, 2359, 1910, 1717, 1658, 1594, 1558, 1537, 1502, 1469, 1446, 1405, 1313, 1280, 1252, 1176, 1130, 1092, 1043, 937, 880, 862, 826, 777, 728, 695, 662, 620 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.84 (s, 1 H), 8.32 (dd, J = 5.9, 3.6 Hz, 1 H), 8.03 (d, J = 8.2 Hz, 1 H), 7.64 (dd, J = 11.5, 7.5 Hz, 2 H), 7.57 (d, J = 7.6 Hz, 1 H), 7.42–7.36 (m, 2 H), 7.30–7.26 (m, 4 H), 7.22 (dd, J = 6.7, 3.1 Hz, 3 H), 7.18 (s, 1 H), 7.03 (d, J = 8.2 Hz, 1 H), 6.98 (s, 1 H), 6.93 (td, J = 7.7, 0.9 Hz, 1 H), 6.86 (dd, J = 5.9, 3.2 Hz, 1 H), 2.44 (s, 3 H), 2.20 (s, 3 H), 2.15 (s, 3 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 19.3, 19.8, 21.7, 117.4, 119.1, 119.9, 120.0, 120.9, 121.2, 121.3, 125.9, 126.0, 126.1, 127.5, 127.6, 128.9, 129.7, 129.9, 130.0, 131.4, 131.7, 132.1, 134.8, 135.6, 136.5, 1370, 137.8, 140.0, 141.7, 142.9, 142.9, 147.7, 134.1, 166.9. HRMS (ESI): m/z [M + H] calcd for C₃₇H₃₁N₂O: 519.2436; found: 519.2438. (Z)-2-((1-(4-Bromophenyl)-2-(9H-fluoren-9-ylidene)ethylidene) amino)-N-phenylbenzamide (3k): Yield: 84%; yellow solid; R_f (10% EtOAc–Hexane): 0.47. FTIR (KBr): 3645, 3052, 3010, 2970, 2932, 2363, 1942, 1913, 1665, 1589, 1523, 1476, 1446, 1417, 1285, 1249, 1159, 1126, 1064, 994, 956, 877, 768, 726, 674, 623 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.55 (s, 1 H), 8.25–8.21 (m, 1 H), 7.93–7.91 (m, 2 H), 7.58–7.53 (m, 4 H), 7.49–7.42 (m, 3 H), 7.33–7.29 (m, 1 H), 7.21 (dd, J = 10.8, 4.3 Hz, 4 H), 7.18 (d, J = 0.8 Hz, 1 H), 7.17 (dd, J = 2.5, 1.0 Hz, 1 H), 7.05 (d, J = 7.7 Hz, 1 H), 6.99 (dd, J = 10.0, 3.7 Hz, 1 H), 6.88–6.85 (m, 2 H), 6.80–6.78 (m, 1 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 118.2, 120.0, 120.1, 120.2, 120.9, 121.2, 124.1, 125.8, 126.5, 127.3, 127.6, 127.7, 129.2, 130.0, 130.1, 130.2, 131.6, 132.0, 132.6, 135.3, 136.3, 137.6, 138.6, 140.1, 141.9, 143.6, 147.5, 164.2, 166.4. HRMS (ESI): m/z [M + 2] calcd for C₃₄H₂₄BrN₂O: 557.1052; found: 557.1053.(Z)-N-(3-Bromophenyl)-2-((1-(4-bromophenyl)-2-(9H-fluoren-9-ylidene)ethylidene)amino)benzamide (3l): Yield: 83%; yellow solid; R_f (15% EtOAc–Hexane): 0.48. FTIR (KBr): 3060, 2923, 2850, 1668, 1589, 1531, 1478, 1445, 1417, 1304, 1284, 1247, 1171, 1121, 1072, 1007, 859, 835, 774, 727, 680, 621 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.78 (s, 1 H), 8.24–8.21 (m, 1 H), 7.92–7.89 (m, 2 H), 7.56 (t, J = 5.5 Hz, 4 H), 7.52 (dd, J = 6.9, 5.0 Hz, 2 H), 7.47 (d, J = 7.6 Hz, 1 H), 7.44–7.41 (m, 1 H), 7.30 (dt, J = 7.5, 3.7 Hz, 1 H), 7.23–7.20 (m, 1 H), 7.18 (s, 2 H), 7.09 (dd, J = 6.6, 1.8 Hz, 1 H), 7.06–7.03 (m, 2 H), 6.87 (dd, J = 7.6, 1.0 Hz, 1 H), 6.85 (s, 1 H), 6.82–6.80 (m, 1 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 117.9, 118.2, 120.1, 120.3, 121.0, 121.3, 122.7, 122.8, 125.8, 125.9, 126.7, 126.9, 127.5, 127.9, 127.7, 130.1, 130.2, 130.3, 130.5, 131.6, 132.2, 132.7, 135.2, 136.4, 137.6, 139.8, 140.1, 141.9, 143.9, 147.4, 164.2, 166.5. HRMS (ESI): m/z [M + 4] calcd for C₃₄H₂₃Br₂N₂O: 637.0177; found: 637.1037.(Z)-N-(3-Bromophenyl)-2-((2-(2,7-dibromo-9H-fluoren-9-ylidene)-1-phenylethylidene)amino)benzamide (3m): Yield: 69%; yellow solid; R_f (15% EtOAc–Hexane): 0.49. FTIR (KBr): 3056, 2919, 2849, 1734, 1671, 1589, 1533, 1476, 1447, 1422, 1307, 1251, 1063, 1003, 952, 879, 810, 773, 696 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 10.97 (s, 1 H), 8.30–8.26 (m, 1 H), 8.00–7.97 (m, 2 H), 7.62 (d, J = 1.4 Hz, 1 H), 7.58–7.54 (m, 2 H), 7.49 (d, J = 7.8 Hz, 2 H), 7.43 (d, J = 1.4 Hz, 1 H), 7.41–7.35 (m, 3 H), 7.31 (dd, J = 8.1, 1.5 Hz, 1 H), 7.24–7.21 (m, 2 H), 7.14 (d, J = 1.4 Hz, 1 H), 7.06 (dd, J = 6.8, 1.6 Hz, 1 H), 7.01 (d, J = 8.0 Hz, 1 H), 6.98 (s, 1 H), 6.83–6.79 (m, 1 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 118.4, 121.1, 121.2, 121.3, 121.4, 121.5, 121.9, 122.6, 122.9, 124.6, 126.1, 126.8, 127.0, 128.7, 129.2, 129.6, 130.2, 131.9, 132.1, 133.0, 136.7, 137.2, 137.9, 139.3, 139.7, 140.0, 141.3, 147.0, 164.0, 166.1. HRMS (ESI): m/z [M + 6] calcd for C₃₄H₂₁Br₃N₂O: 716.9222; found: 716.9244.(E)-5-Bromo-2-((2-bromo-2(9H-fluoren-9-ylidene)-1-phenyl ethylidene)amino)benzamide (4a): Yield: 60%; yellow solid; R_f (15% EtOAc–Hexane): 0.43. FTIR (KBr): 3400, 3059, 1664, 1604, 1576, 1462, 1447, 1408, 1344, 1315, 1263, 1204, 1181, 1096, 1056, 1024, 936, 851, 811, 779, 730, 691, 649, 620 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 8.52 (d, J = 7.9 Hz, 1 H), 8.23 (d, J = 2.3 Hz, 1 H), 7.98 (dd, J = 5.3, 3.3 Hz, 2 H), 7.87 (s, 1 H), 7.61 (d, J = 7.2 Hz, 1 H), 7.56 (d, J = 7.5 Hz, 1 H), 7.50–7.46 (m, 1 H), 7.39 (ddd, J = 9.6, 7.0, 4.0 Hz, 3 H), 7.31 (d, J = 7.9 Hz, 1 H), 7.25 (ddd, J = 7.3, 6.8, 3.8 Hz, 2 H), 7.17 (dd, J = 6.4, 2.1 Hz, 1 H), 6.98 (td, J = 7.8, 1.1 Hz, 1 H), 6.62 (d, J = 8.5 Hz, 1 H), 6.05 (s, 1 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 113.1, 119.3, 119.9, 120.0, 120.6, 124.4, 126.4, 126.6, 127.6, 127.9, 128.6, 129.5, 129.6, 130.4, 132.7, 134.1, 134.2, 134.9, 136.2, 136.3, 139.9, 140.3, 141.5, 146.2, 165.6, 166.6. HRMS (ESI): m/z [M + 4] calcd for C₂₈H₁₉Br₂N₂O: 560.9864; found: 560.9847.(E)-2-((2-Bromo-2-(9H-fluoren-9-ylidene)-1-(p-toluenesulfonyl) ethylidene)amino)benzamide (4b): Yield: 75%; yellow solid; R_f (15% EtOAc–Hexane): 0.45. FTIR (KBr): 3608, 3440, 3341, 3159, 3059, 2919, 2852, 1670, 1563, 1492, 1471, 1445, 1374, 1290, 1267, 1204, 1181, 1113, 1059, 1019, 977, 926, 834, 777, 727, 660, 624 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 8.51 (d, J = 7.9 Hz, 1 H), 8.11–8.07 (m, 1 H), 7.96 (s, 1 H), 7.88 (d, J = 8.3 Hz, 2 H), 7.61–7.53 (m, 2 H), 7.39–7.33 (m, 2 H), 7.26–7.18 (m, 4 H), 7.06 (dd, J = 5.9, 3.5 Hz, 2 H), 7.01–6.97 (m, 1 H), 6.74–6.71 (m, 1 H), 5.95 (s, 1 H), 2.33 (s, 3 H); ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 21.7, 114.2, 119.0, 119.9, 120.0, 124.7, 125.7, 126.4, 127.6, 128.0, 128.7, 129.5, 130.2, 130.3, 131.4, 131.8, 132.2, 136.5, 136.6, 139.6, 140.3, 141.5, 143.4, 147.5, 164.9, 168.3. HRMS (ESI): m/z [M + 2] calcd for C₂₉H₂₂BrN₂O: 495.0995; found: 495.1180.(E)-2-((2-Bromo-2-(9H-fluoren-9-ylidene)-1-phenyl­ethylidene)amino)benzenesulfonamide (4c): Yield: 73%; yellow solid; R_f (15% EtOAc–Hexane): 0.44. FTIR (KBr): 3358, 3260, 2920, 1915, 1641, 1611, 1530, 1444, 1344, 1276, 1254, 1209, 1171, 1128, 1070, 1024, 942, 857, 832, 807, 772, 689, 620 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 8.58 (d, J = 7.9 Hz, 1 H), 7.98–7.93 (m, 3 H), 7.66 (d, J = 7.6 Hz, 1 H), 7.61 (d, J = 7.5 Hz, 1 H), 7.45–7.39 (m, 3 H), 7.38–7.35 (m, 2 H), 7.29–7.24 (m, 2 H), 7.16–7.11 (m, 2 H), 7.00 (td, J = 7.9, 1.0 Hz, 1 H), 6.90–6.87 (m, 1 H), 5.39 (s, 2 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 21.0, 21.8, 119.3, 120.0, 121.0, 121.1, 125.9, 126.0, 127.4, 127.5, 128.9, 129.5, 129.7, 129.8, 131.4, 131.7, 133.4, 134.6, 135.5, 136.2, 137.7, 140.0, 141.7, 142.8, 143.0, 147.8, 164.2, 166.9. HRMS (ESI): m/z [M + 2] calcd for C₂₇H₂₀BrN₂O₂S: 517.0408; found: 517.0420.(E)-2-((2-Bromo-2-(9H-fluoren-9-ylidene)-1-phenyl­ethylidene)amino)-5-iodobenzamide (4d): Yield: 72%; yellow solid; R_f (15% EtOAc–Hexane): 0.43. FTIR (KBr): 3370, 3327, 3145, 3063, 2921, 2774, 2252, 1959, 1903, 1811, 1669, 1596, 1565, 1445, 1404, 1347, 1314, 1260, 1202, 1152, 1087, 1052, 1022, 935, 904, 872, 845, 801, 774, 727, 688, 645, 622 cm^–1. ¹H NMR (400 MHz, CDCl₃/TMS): δ = 8.52 (d, J = 7.9 Hz, 1 H), 8.40 (d, J = 2.1 Hz, 1 H), 7.99–7.96 (m, 2 H), 7.84 (d, J = 2.6 Hz, 1 H), 7.60 (d, J = 7.5 Hz, 1 H), 7.56–7.54 (m, 1 H), 7.47–7.44 (m, 1 H), 7.41–7.33 (m, 5 H), 7.30 (d, J = 7.9 Hz, 1 H), 7.27–7.19 (m, 2 H), 6.97 (td, J = 7.8, 1.1 Hz, 1 H), 6.49–6.46 (m, 1 H). ¹³C NMR (CDCl₃/TMS, 100.6 MHz): δ = 90.1, 113.2, 120.0, 120.1, 120.9, 124.5, 126.5, 126.6, 127.7, 128.0, 128.8, 129.6, 129.7, 130.5, 132.9, 134.2, 136.3, 136.4, 139.9, 140.1, 140.4, 140.9, 141.6, 146.9, 165.6, 166.8. HRMS (ESI): m/z [M + 2] calcd for C₂₈H₁₉BrIN₂O: 606.9705; found: 606.9719.