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Synlett 2010(20): 3031-3034  
DOI: 10.1055/s-0030-1259076
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Site-Selective Suzuki-Miyaura Reactions of the Bis(triflate) of 5,10-dihydroxy-11H-benzo[b]fluoren-11-one

Ghazwan Ali Salmana, Munawar Hussaina, Alexander Villingera, Peter Langer*a,b
a Institut für Chemie, Universität Rostock, Albert Einstein Str. 3a, 18059 Rostock, Germany
b Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert Einstein Str. 29a, 18059 Rostock, Germany
Fax: +49(381)4986412; e-Mail: peter.langer@uni-rostock.de;
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Received 19 October 2010
Publication Date:
25 November 2010 (online)

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Abstract

5,10-Diaryl-11H-benzo[b]fluoren-11-ones were prepared by Suzuki-Miyaura reactions of the bis(triflate) of 5,10-dihydroxy-11H-benzo[b]fluoren-11-one. The reactions proceed with excellent site-selectivity. The first attack occurs at position 10, due to electronic reasons.

Key words

catalysis - palladium - Suzuki-Miyaura reaction - regio­selectivity - fluorenones

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Synthesis of 11-Oxo-11 H -benzo[ b ]fluorene-5,10-diyl Bis(trifluoromethanesulfonate) (2): To a solution of 1 (2.0 g, 7.6 mmol) in CH2Cl2 (80 mL) was added pyridine (2.5 mL, 30.5 mmol), at 20 ˚C under an argon atmosphere. After stirring for 10 min, Tf2O (3.0 mL, 18 mmol) was added at -78 ˚C. The mixture was allowed to warm to 20 ˚C and stirred overnight. The reaction mixture was filtered and the filtrate was concentrated in vacuo. The residue was purified by chromatography (flash silica gel, heptanes-EtOAc) without aqueous work up to give 2 as a yellow solid (3.5 g, 88%); mp 186-188 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 7.43 (t, 1 H, J = 7.7 Hz, ArH), 7.59-7.79 (m, 4 H, ArH), 8.01 (t, 2 H, J = 8.0 Hz, ArH), 8.10 (d, 1 H, J = 8.3 Hz, ArH). ¹9F NMR (282.4 MHz, CDCl3): δ = -72.29, -72.3. ¹³C NMR (75.5 MHz, CDCl3): δ = 118.6 (q, J F,C = 320.5 Hz, CF3), 118.7 (q, J F,C = 321.4 Hz, CF3), 122.8, 124.0, 125.36 (CH), 128.2 (C), 129.4, 131.2, 131.3 (CH), 132.0, 135.7 (C), 135.9 (CH), 136.8, 140.2, 141.2 (C), 187.2 (CO). IR (KBr): 3085, 2926, 2854 (w), 1721 (m), 1635, 1600, 1591, 1581, 1516, 1466 (w), 1435, 1405 (m), 1391, 1337, 1289, 1274, 1241 (w), 1203 (s), 1173 (m), 1128 (s), 1082 (m), 1043 (w), 1011, 975 (m), 891 (s), 865, 814, 782 (m), 760, 747, 722 (s), 688 (m), 662, 651, 638 (w), 621, 595, 590 (s), 570, 528 (m) cm-¹. GC-MS (EI, 70 eV): m/z (%) = 526 (53) [M+], 393 (77), 329 (99), 301 (100). HRMS (EI, 70 eV): m/z calcd for C19H8O7S2F6: 525.96101; found: 525.961568

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General Procedure for Suzuki-Miyaura Reactions: A 1,4-dioxane solution (4-5 mL/0.3 mmol of 2) of K3PO4 (1.5-2.0 equiv), Pd(PPh3)4 (3 mol% per cross-coupling) and arylboronic acid 3 (1.0-1.1 equiv per cross-coupling) was stirred at 60-90 ˚C for 10 h. After cooling to 20 ˚C, distilled H2O was added. The organic and the aqueous layers were separated and the latter was extracted with CH2Cl2. The combined organic layers were dried (Na2SO4), filtered and the filtrate was concentrated in vacuo. The residue was purified by column chromatography.

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Synthesis of 5,10-Bis(4-methoxyphenyl)-11 H -benzo[ b ]-fluoren-11-one (4a): Starting with 2 (150 mg, 0.28 mmol), 4-methoxyphenylboronic acid (3a; 96 mg, 0.63 mmol), Pd(PPh3)4 (19 mg, 6 mol%), K3PO4 (178 mg, 0.84 mmol) and 1,4-dioxane (5 mL), 4a was isolated as a yellow solid (100 mg, 80%); mp 243-245 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 3.85 (s, 3 H, OMe), 3.90 (s, 3 H, OMe), 6.31-6.36 (m, 1 H, ArH), 7.02 (d, 2 H, J = 8.4 Hz, ArH), 7.07-7.12 (m, 4 H, ArH), 7.25-7.31 (m, 5 H, ArH), 7.35 (td, 1 H, J = 1.4, 8.1 Hz, ArH), 7.43-7.46 (m, 1 H, ArH), 7.50-7.58 (m, 1 H, ArH), 7.63-7.66 (m, 1 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 55.3, 55.4 (OMe), 113.6, 114.8, 123.8, 123.9, 126.5, 127.1 (CH), 127.8, 128.4 (C), 128.5, 129.0 (CH), 129.8 (C), 130.9, 131.0 (CH), 133.9, 134.0 (C), 134.3 (CH), 135.8, 136.8, 137.2, 140.5, 144.5, 159.4, 159.6 (C), 192.6 (CO). IR (KBr): 3064, 2997, 2952, 2929, 2849, 2831 (w), 1704 (s), 1606, 1589 (m), 1579 (w), 1510 (s), 1462, 1441, 1410, 1361, 1335, 1311 (w), 1286 (m), 1243 (s), 1215, 1191 (m), 1173 (s), 1107, 1086, 1048 (w), 1034, 1026 (m), 1005 (w), 963 (m), 932, 899 (w), 870, 830, 805, 791 (m), 759, 727 (s), 693, 681, 655, 633 (w), 623, 596 (m), 573 (w), 559, 531 (m) cm-¹. GC-MS (EI, 70 eV): m/z (%) = 442 (100) [M+], 441 (28), 411 (6), 326 (5). HRMS (EI, 70 eV): m/z calcd for C31H22O3: 442.15635; found: 442.155487.

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Synthesis of 10-(3,4-Dimethoxyphenyl)-11-oxo-11 H -benzo[ b ]fluoren-5-yl Trifluoromethanesulfonate (5g): Starting with 2 (150 mg, 0.28 mmol), 3,4-dimethoxy-phenylboronic acid (3g; 56 mg, 0.3 mmol), Pd(PPh3)4 (10 mg, 3 mol%), K3PO4 (119 mg, 0.56 mmol) and 1,4-dioxane (5 mL), 5g was isolated as a yellow solid (129 mg, 88%); mp 221-222 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 3.79 (s, 3 H, OMe), 3.92 (s, 3 H, OMe), 6.79-6.85 (m, 2 H, ArH), 6.97 (d, 1 H, J = 8.2 Hz, ArH), 7.33 (td, 1 H, J = 0.8, 7.4 Hz, ArH), 7.39-7.44 (m, 1 H, ArH), 7.53-7.68 (m, 4 H, ArH), 8.02 (d, 2 H, J = 7.8 Hz, ArH). ¹9F NMR (282.4 MHz, CDCl3): δ =
-72.47. ¹³C NMR (75.5 MHz, CDCl3): δ = 55.9, 56.0 (OMe), 110.9, 112.9 (CH), 118.7 (q, J F,C = 321.6 Hz, CF3), 122.1, 124.5, 125.0 (CH), 126.6 (C), 128.0 (CH), 129.4 (C), 129.5, 129.9 (CH), 130.3 (C), 130.4 (CH), 130.9 (C), 135.1 (CH), 135.7, 136.5, 137.7, 140.3, 141.5, 148.8, 149.2 (C), 190.3 (CO). IR (KBr): 3076, 3012, 2966, 2939, 2919, 2838, 2249 (w), 1718 (s), 1623, 1600, 1579 (w), 1517, 1511 (m), 1468, 1448 (w), 1404 (s), 1374, 1345, 1334, 1319, 1297, 1255 (w), 1215 (s), 1172 (m), 1134 (s), 1090, 1054 (w), 1020 (m), 998 (s), 963 (m), 913 (w), 892 (m), 866 (w), 817, 804 (s), 788, 777 (w), 758 (s), 745 (w), 722 (s), 687 (m), 665 (w), 653, 647 (m), 629, 611 (s), 589, 559 (w) cm-¹. GC-MS (EI, 70 eV): m/z (%) = 514 (28) [M+], 381 (100), 353 (4). HRMS (EI, 70 eV): m/z calcd for C26H17O6F3S: 514.06925; found: 514.070130.

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Synthesis of 5-(3,5-Dimethylphenyl)-10-(4-methoxyphenyl)-11 H -benzo[ b ]fluoren-11-one (6a): Starting with 2 (150 mg, 0.28 mmol), 4-methoxy-phenylboronic acid (3a; 43 mg, 0.28 mmol), Pd(PPh3)4 (10 mg, 3 mol%), K3PO4 (119 mg, 0.56 mmol), 1,4-dioxane (5 mL), and 3,5-dimethylphenylboronic acid (3d; 46 mg, 0.31 mmol), 6a was isolated as a yellow solid (90 mg, 72%); mp 220-222 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 2.36 (s, 6 H, 2 × Me), 3.85 (s, 3 H, OMe), 6.27-6.33 (m, 1 H, ArH), 6.98 (br s, 2 H, ArH), 7.02 (d, 2 H, J = 8.8 Hz, ArH), 7.08-7.14 (m, 3 H, ArH), 7.26 (d, 2 H, J = 8.8 Hz, ArH), 7.27-7.30 (m, 1 H, ArH), 7.34 (td, 1 H, J = 1.3, 8.2 Hz, ArH), 7.43-7.46 (m, 1 H, ArH), 7.50-7.53 (m, 1 H, ArH), 7.63-7.66 (m, 1 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 21.5 (2 × Me), 55.3 (OMe), 113.6, 123.8, 123.9, 126.5, 127.3, 127.4 (CH), 127.8, 128.4 (C), 128.5, 128.9, 129.8, 131.0 (CH), 134.0 (C), 134.4 (CH), 134.5, 135.2, 136.7, 136.8, 137.6, 139.9, 140.4, 144.5, 159.4 (C), 192.6 (CO). IR (KBr): 3068, 3000, 2955, 2923, 2852 (w), 1703, 1695, 1598, 1505 (s), 1466, 1435, 1423, 1363, 1336, 1311, 1302, 1287, 1259 (w), 1244 (s), 1202 (m), 1172 (s), 1130, 1105, 1087, 1049 (w), 1029, 998 (m), 969, 950, 939, 926, 906 (w), 873 (m), 848, 834 (w), 826, 790, 778 (m), 761 (s), 742 (w), 724 (s), 710, 703, 680, 661, 631 (w), 613, 595 (m), 579 (w), 562, 538 (m) cm-¹. GC-MS (EI, 70 eV): m/z (%) = 440 (100) [M+], 409 (6), 396 (4). HRMS (ESI+): m/z [M + H]+ calcd for C32H24O2: 440.17708; found: 440.176873.

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CCDC 799371 contains all crystallographic details
of this publication and is available free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html or can be ordered from the following address: Cambridge Crystallographic Data Centre, 12 Union Road, GB-Cambridge CB21EZ, U.K.; Fax: +44 (1223)336033; or Email: deposit@ccdc.cam.ac.uk.