Benzocycloheptynedicobalt Complexes by Intramolecular Nicholas Reactions

Abstract

Lewis acid mediated intramolecular Nicholas reactions of aryl (Z)-enyne propargyl acetate-Co₂(CO)₆ complexes 1 afford benzocycloheptenyne-Co₂(CO)₆ complexes 2 and their heterocyclic analogues.

Key words

Nicholas reactions - alkynes - arenes - complexes - transition metals

References

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• 15 This reflects a tendency for a slightly lower preference for C-2 reactivity in thiophenes relative to furans and perhaps the known tendency for electron withdrawing C-3 groups to deactivate C-2 to a greater degree than C-4. See: Taylor R. In The Chemistry of Heterocyclic Compounds   Part 2, Vol. 44:  Gronowitz S. Wiley; New York: 1986.  Chap. 1. p.16 
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12

Selected compounds:
Compound 5b: IR (neat, KBr): ν_max = 3345, 3020, 2920, 2193 cm^-1. ¹H NMR: δ = 1.77 (1 H, br), 2.38 (3 H, s), 4.50 (1 H, d, J = 2.0 Hz), 5.71 (1 H, dt, J = 11.9, 2.0 Hz), 6.64 (1 H, d, J = 11.9 Hz), 7.11 (1 H, d, J = 7.5 Hz), 7.27 (1 H, dd, J = 7.7, 7.5 Hz), 7.63 (1 H, s), 7.68 (1 H, d, J = 7.7 Hz). ¹³C NMR: δ = 139.4, 137.8, 136.1, 129.4, 128.2, 125.6, 106.5, 93.6, 84.3, 51.8, 21.4. MS (EI): m/z = 172. HRMS (EI): m/z calcd for C₁₂H₁₂O: 172.0888; found: 172.0888.
Compound 5g: IR (neat, KBr): ν_max = 3358, 3097, 2918, 2191, 1699, 1602 cm^-1. ¹H NMR: δ = 2.39 (1 H, s), 4.51 (2 H, d, J = 2.0 Hz), 5.62 (1 H, dt, J = 11.7, 2.3 Hz), 6.70 (1 H, d, J = 11.7 Hz), 7.29 (1 H, dd, J = 4.9, 2.6 Hz), 7.62 (1 H, d, J = 5.0 Hz), 7.76 (1 H, d, J = 2.1 Hz). ¹³C NMR: δ = 138.3, 133.0, 127.7, 125.6, 125.2, 105.2, 93.8, 84.4, 51.6. MS (EI): m/z = 164. HRMS (EI): m/z calcd for C₉H₈OS: 164.0296; found: 164.0292.

13

Selected compounds:
Compound 1b: IR (neat, KBr): ν_max = 3014, 2927, 2092, 2024, 1748 cm^-1. ¹H NMR: δ = 2.03 (3 H, s), 2.39 (3 H, s), 4.52 (2 H, s), 6.61 (1 H, d, J = 11.0 Hz), 6.80 (1 H, d, J = 11.0 Hz), 7.02 (2 H, d, J = 8.2 Hz), 7.14 (1 H, d, J = 7.6 Hz), 7.29 (1 H, d, J = 7.5 Hz). ¹³C NMR: δ = 199.1 (br), 170.5, 138.2, 137.6, 132.5, 129.0, 128.5, 128.4, 127.5, 125.4, 91.4, 83.5, 64.9, 21.3, 20.3. MS (EI): m/z = 472 [M - CO]⁺, 444 [M - 2 CO]⁺, 416 [M -3 CO]⁺, 388 [M - 4 CO]⁺, 360 [M - 5 CO]⁺, 332 [M - 6CO]⁺. HRMS (EI): m/z calcd for C₂₀H₁₄ Co₂O₈: 443.9454 [M - 2 CO]⁺; found: 443.9457.
Compound 1g: IR (neat, KBr): ν_max = 3013, 2956, 2092, 2022, 1746 cm^-1. ¹H NMR: δ = 2.07 (3 H, s), 4.73 (2 H, s), 6.62 (1 H, d, J = 11.0 Hz), 6.67 (1 H, d, J = 11.0 Hz), 6.98 (1 H, d, J = 4.3 Hz), 7.13 (1 H, s), 7.38 (1 H, s). ¹³C NMR: δ = 199.3 (br), 170.5, 138.2, 128.3, 128.2, 126.8, 126.2, 123.4, 91.4, 83.3, 64.5, 20.3. MS (EI): m/z = 464 [M - CO]⁺, 436 [M - 2 CO]⁺, 408 [M - 3 CO]⁺, 380 [M - 4 CO]⁺, 352 [M - 5 CO]⁺, 324 [M - 6 CO]⁺. HRMS (EI): m/z calcd for C₁₇H₁₀Co₂O₈S: 435.8862 [M - 2 CO]⁺; found: 435.8853.

14

Experimental Procedure:
To a stirred ice cold solution of the propargyl acetate complex (0.2 mmol) in CH₂Cl₂ (20 mL) was added BF₃·OEt₂ (85.2 mg, 0.60 mmol) in CH₂Cl₂ (4 mL) over 10 min. After stirring at 0 °C for the time indicated in Table [2] , sat. NaHCO₃ solution was added, and the mixture was subjected to a conventional work up. Purification by flash chroma-tography afforded sequentially the benzocycloheptenyne complex and any recovered starting material.

17

Compound 2a: IR (neat, KBr): ν_max = 2929, 2091, 2021, 1574 cm^-1. ¹H NMR: δ = 4.18 (2 H, s), 6.77 (1 H, d, J = 10.1 Hz), 6.93 (1 H, d, J = 10.1 Hz), 7.22 (4 H, m). ¹³C NMR: δ = 199.3 (br), 137.5, 137.3, 133.1, 132.5, 129.4, 128.9, 128.8, 126.9, 102.3, 86.5, 40.8. MS (EI): m/z = 426 [M]⁺, 398 [M - CO]⁺, 370 [M - 2 CO]⁺, 342 [M - 3 CO]⁺, 314 [M - 4 CO]⁺, 286 [M - 5 CO]⁺, 258 [M - 6 CO]⁺. HRMS (EI): m/z calcd for C₁₇H₈Co₂O₆: 426.9063 [M + H]⁺; found: 426.9069.
Compound 2b: IR (neat, KBr): ν_max = 3014, 2858, 2090, 2053, 2021, 1557 cm^-1. ¹H NMR: δ = 2.31 (3 H, s), 4.14 (2 H, s), 6.72 (1 H, d, J = 10.1 Hz), 6.90 (1 H, d, J = 10.1 Hz), 7.00 (1 H, s), 7.07 (1 H, d, J = 7.9 Hz), 7.15 (1 H, d, J = 7.6 Hz); resonances for minor regioisomer (2b′) could be observed at δ = 2.51 (3 H, s), 4.10 (2 H, s), 6.82 (1 H, d, J = 10.0 Hz), 6.93 (1 H, d, J = 10.0 Hz), 7.03 (1 H, m), 7.10 (1 H, m), 7.17 (1 H, m). ¹³C NMR: δ = 199.4 (br), 137.3, 136.4, 134.5, 133.2, 129.6, 129.4, 128.5, 102.5, 86.9, 40.4, 20.7; resonances for the minor regioisomer could be observed at δ = 133.8, 130.7, 130.4, 128.8, 126.3, 34.2, 21.1. MS (EI): m/z = 440 [M]⁺, 412 [M - CO]⁺, 384 [M - 2 CO]⁺, 356 [M⁺ - 3 CO], 328 [M - 4 CO]⁺, 300 [M - 5 CO]⁺, 272 [M - 6 CO]⁺. HRMS (EI): m/z calcd for C₁₈H₁₀Co₂O₆: 439.9141; found: 439.9137.
Compound 2c: IR (neat, KBr): ν_max = 3014, 2956, 2837, 2090, 2050, 2020, 1604 cm^-1. ¹H NMR: δ = 3.77 (3 H, s), 4.10 (2 H, s), 6.68 (1 H, d, J = 10.1 Hz), 6.71 (1 H, s), 6.79 (1 H, d, J = 8.3 Hz), 6.92 (1 H, d, J = 10.1 Hz), 7.16 (1 H, d, J = 8.3 Hz). ¹³C NMR: δ = 199.3 (br), 158.3, 138.6, 132.8, 130.5, 130.0, 129.3, 117.7, 113.9, 102.9, 86.6, 55.3, 39.9. MS (EI): m/z = 456 [M]⁺, 428 [M - CO]⁺, 400 [M - 2 CO]⁺, 372 [M - 3 CO]⁺, 344 [M - 4 CO]⁺, 316 [M - 5 CO]⁺, 288 [M - 6 CO]⁺. HRMS (EI): m/z calcd for C₁₈H₁₀Co₂O₇: 455.9090; found: 455.9051.
Compound 2e: IR (neat, KBr): ν_max = 3026, 2935, 2090, 2052, 2022, 1602, 1556 cm^-1. ¹H NMR: δ = 3.88 (3 H, s), 5.35 (1 H, s), 6.77 (1 H, dd, J = 8.6, 2.6 Hz), 6.82 (1 H, s), 6.83 (1 H, m), 7.01 (1 H, d, J = 10.1 Hz), 7.09 (1 H, d, J = 8.5 Hz), 7.23 (1 H, m), 7.29 (2 H, m), 7.35 (2 H, m). ¹³C NMR: δ = 199.4 (br), 158.3, 144.4, 138.3, 133.5, 133.1, 131.3, 129.6, 128.6, 127.0, 118.4, 114.2, 107.1, 84.8, 55.4, 55.3. MS (EI): m/z = 504 [M - CO]⁺, 476 [M - 2 CO]⁺, 448 [M - 3 CO]⁺, 420 [ M - 4 CO]⁺, 392 [M - 5 CO]⁺, 364 [M - 6 CO]⁺. HRMS (EI): m/z calcd for C₂₄H₁₄Co₂O₇: 503.9454 [M - CO]⁺; found: 503.9437.
Compound 2f: IR (neat, KBr): ν_max = 3025, 2928, 2092, 2051, 2020. ¹H NMR: δ = 4.47 (2 H, s), 6.31 (1 H, s), 6.39 (1 H, d, J = 9.6 Hz), 6.57 (1 H, d, J = 9.6 Hz), 7.30 (1 H, s). ¹³C NMR: δ = 199.3 (br), 148.8, 140.8, 125.1, 124.1, 120.5, 113.3, 92.2, 86.6, 34.0. MS (EI): m/z = 416 [M]⁺, 388 [M - CO]⁺, 360 [M - 2 CO]⁺, 332 [M - 3 CO]⁺, 304 [M - 4 CO]⁺, 276 [M - 5 CO]⁺, 248 [M - 6 CO] ⁺ . HRMS (EI): m/z calcd for C₁₅H₆Co₂O₇: 415.8777 [M]⁺; found: 415.8752.
Compound 2g: IR (neat, KBr): ν_max = 2926, 2856, 2092, 2055, 2024, 1699, 1650, 1540 cm^-1. ¹H NMR: δ = 4.45 (2 H, s), 6.68 (1 H, AB quartet, J = 16.0 Hz), 6.74 (1 H, AB quartet, J = 16.1 Hz), 6.88 (1 H, d, J = 8.7 Hz), 7.08 (1 H, d, J = 8.8 Hz); resonances for minor regioisomer (2g′) could be observed (in CD₃CN) at δ = 4.34 (2 H, s), 6.66 (1 H, d, J = 9.9 Hz), 6.80 (1 H, d, J = 9.7 Hz), 7.20 (1 H, s), 7.38 (1 H, s). ¹³C NMR: δ = 199.1 (br), 136.8, 136.7, 132.0, 126.4, 126.2, 122.0, 97.6, 86.8, 34.6; resonances for the minor regioisomer could be observed at δ = 128.7, 126.9, 124.8, 35.5. MS (EI) m/z = 432 [M]⁺, 404 [M - CO]⁺, 376 [M - 2 CO]⁺, 348 [M - 3 CO]⁺, 320 [M - 4 CO]⁺, 292 [M - 5 CO]⁺, 264 [M - 6 CO]⁺. HRMS (EI): m/z calcd for C₁₅H₆Co₂O₆S: 403.8575 [M - CO]⁺; found: 403.8554.
Compound 2j: IR (neat, KBr): ν_max = 3055, 2090, 2051, 2021, 1594 cm^-1. ¹H NMR: δ = 3.78 (3 H, s), 3.83 (3 H, s), 3.91 (3 H, s), 4.05 (2 H, s), 6.62 (1 H, s), 6.93 (1 H, d, J = 10.4 Hz), 7.12 (1 H, d, J = 10.4 Hz). ¹³C NMR: δ = 199.4, 153.3, 152.8, 141.4, 134.3, 127.7, 125.9, 124.7, 108.4, 102.9, 87.7, 61.1, 61.0, 56.0, 41.1. MS (EI): m/z = 516 [M]⁺, 460 [M - 2 CO]⁺, 404 [M - 4 CO]⁺. HRMS: m/z calcd for C₂₀H₁₄Co₂O₉: 403.9505 [M - 4 CO]⁺; found: 403.9492.
Compound 2k: IR (neat, KBr): ν_max = 3014, 2957, 2360, 2091, 2052, 2022 cm^-1. ¹H NMR: δ = 0.28 (9 H, s), 4.20 (2 H, s), 6.76 (1 H, d, J = 10.1 Hz), 6.94 (1 H, d, J = 10.1 Hz), 7.16 (1 H, d, J = 7.5 Hz) 7.36 (1 H, s), 7.37 (1 H, d, J = 6.2 Hz). ¹³C NMR: δ = 199.4 (br), 142.0, 137.7, 136.3, 134.2, 133.2, 131.9, 131.7, 129.0, 102.4, 86.6, 40.9, -1.2. MS (EI) m/z = 498 [M]⁺, 470 [M - CO]⁺, 442 [M - 2 CO]⁺, 414 [M - 3 CO]⁺, 386 [M - 4 CO]⁺, 358 [M - 5 CO]⁺, 330 [M - 6 CO]⁺. HRMS (EI): m/z calcd for C₂₀H₁₆Co₂O₆Si: 469.9431 [M - CO]⁺; found: 469.9434.