CC BY-NC-ND 4.0 · SynOpen 2021; 05(01): 17-24
DOI: 10.1055/s-0040-1706015
letter

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

Mohanakumaran Athira
,
M.A. thanks CSIR-New Delhi for the award of a Senior Research Fellowship.


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.

Supporting Information



Publication History

Received: 16 May 2020

Accepted after revision: 03 January 2021

Publication Date:
25 January 2021 (online)

© 2021. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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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 3am 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 4ad in good yields. (Z)-2-((2-(9H-Fluoren-9-ylidene)-1-phenylethylidene)amino)benzamide (3a): Yield: 92%; yellow solid; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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; Rf (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.