Use of Oxirane Ring-Opening Reactions for Synthesis of Ethylene-bis(indenyl) Ligands Containing Alkene Tethers

Abstract

An efficient strategy is presented for the synthesis of novel bis-indenyl ligands containing alkene tethers for their further immobilization. The tether was attached to a bridge or aromatic ring of the ligand. The ligands were prepared using oxirane ring-opening reaction.

Key words

indene - ethylene-bis(indene) - ligand - oxirane-cleavage - tethering

References

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6

Panarello, A.; Vassylyev, O.; Khinast, J. G. Tetrahedron Lett. 2005, accepted for publication.

9

Ethylene oxide (2 mol equiv) passed through a solution of 2 (1 mol equiv) in THF at -78 °C for 2 h. Then the reaction mixture was kept at stirring for 1.5 h at 0 °C and allowed to gradually warming to r.t. overnight, quenched by aq NH₄Cl and extracted by Et₂O. Organic phase was washed with H₂O, dried over MgSO₄ and purified by column chromatography with hexane-Et₂O mixture (5:2).

11

General Procedure for Iodination.
Hydroxy-compound was dissolved in a mixture Et₂O-MeCN (4:1) together with PPh₃ (1.1 mol equiv), imidazole (2 mol equiv) and I₂ (2 mol equiv). After 20 min of stirring at r.t., the reaction mixture was diluted by Et₂O, filtered, liquid phase washed by aq NaHCO₃ and brine, dried over MgSO₄ and concentrated. The product was purified by column chromatography using hexane as eluent.

13

General Procedure for Preparation of bis-Indenyl Compounds.
Iodide compound (1.05 mol equiv) in THF-hexanes was added dropwise to the solution of 2 (1 mol equiv) in THF at -78 °C during 25 min, and allowed to warm to r.t. overnight. Then the reaction mixture was treated similar to 3.

14

The Suzuki Coupling Reaction Using Pd(PPh ₃ ) ₄ .
In an oven-dried reaction flask equipped with a reflux head and a stir bar, Pd(PPh₃)₄ (1 mol%), arylboronic acid 13 (0.32 mmol, 1.3 mol equiv) and 12 (0.25 mmol, 1 mol equiv) were charged to a solution of DMM (4 mL). The mixture was allowed to stir at r.t. while aq K₂CO₃ (2.0 M, 3.3 mol equiv) was added. The reaction was then placed in an oil bath and refluxed for 6 h. The reaction was quenched at r.t. by adding H₂O (25 mL) and CH₂Cl₂ (25 mL). A liquid-liquid extraction was performed, where the organic phase was collected and dried over MgSO₄. The reaction mixture was then purified by silica gel chromatography to afford the desired coupling product.

15

Solution of 2 (1.05 mol equiv) in THF was added dropwise to the solution of 9 (1 mol equiv) and catalytic amount of Cu₂I₂ in THF at 0 °C. Further treatment was similar to 3.

16

Isomers were characterized by the presence of the cyclopentadienyl peaks in the ¹H NMR spectra. A decrease in the doublet intensity (δ = 6.25-6.15 ppm) is replaced by the alkene isomer peaks that show up as double doublets at δ = 7.00-6.95 and 6.70-6.55 ppm. In addition, a shift in the alkene peak was also observed; from δ = 5.90-5.80 to 5.65-5.75 ppm.

17

Analytical data for novel compounds. Data are reported for compound purity greater than 95% (trace solvent or moisture).
3-(2′-Hydroxyethyl)-1 H -indene ( 3): ¹H NMR (CDCl₃): δ = 7.50 (d, 1 H, J = 7 Hz), 7.40 (d, 1 H, J = 7 Hz), 7.35-7.30 (t, 1 H, J = 7 Hz), 7.30-7.25 (dt, 1 H, J = 7 Hz, 7 Hz), 6.35 (s, 1 H), 4.00-3.90 (br s, 2 H), 3.40 (s, 2 H), 2.90-2.85 (qt, 2 H, J = 2, 7 Hz), 2.10-2.00 (br s, 1 H). ¹³C NMR (CDCl₃): δ = 145.0, 144.4, 140.8, 129.9, 126.1, 124.8, 123.9, 119.0, 61.1, 37.9, 31.2. MS: m/z = 160 [M]⁺, 143 [Ind - (CH₂)₂]⁺, 129 [Ind - CH₂]⁺.
3-(2′-Iodoethyl)-1 H -indene (4): ¹H NMR (CDCl₃): δ = 7.60 (d, 1 H, J = 7 Hz), 7.45 (d, 2 H, J = 4 Hz), 7.40-7.35 (m, 1 H), 6.40 (s, 1 H), 3.60-3.55 (t, 2 H, J = 8 Hz), 3.45 (s, 2 H), 3.25-2.20 (t, 2 H, J = 8 Hz). ¹³C NMR (CDCl₃): δ = 144.3, 143.1, 129.5, 126.3, 125.1, 124.1, 118.8, 38.1, 32.8, 3.1. Due to the instability of the compound, IR or MS could not be obtained. ¹³C NMR was only obtained after using a very high concentration 50 mg/mL and a small number of scans.

3-[2′-(1 H -Inden-3′′-yl)-ethyl]-5-bromo-1 H -indene (6): ¹H NMR (CDCl₃): δ = 7.50-7.47 (d, 1 H, J = 9 Hz), 7.45-7.40 (dd, 2 H, J = 8, 8 Hz), 7.35 (s, 2 H), 7.25 (d, 2 H, J = 7 Hz), 6.29 (s, 2 H), 3.36 (s, 2 H), 3.34-3.30 (d, 2 H, J = 10 Hz), 2.95 (s, 4 H). ¹³C NMR (CDCl₃): δ = 147.7, 146.6, 145.3, 144.5, 143.9, 143.7, 143.6, 143.2, 129.7, 129.1, 128.4, 128.1, 127.3, 127.1, 126.1, 125.1, 124.7, 123.9, 122.2, 120.3, 120.1, 118.9, 118.8, 37.8, 37.7, 37.5, 26.2, 26.1. IR (NaBr): 3063, 2902, 1599, 1563, 1459, 1396, 1273, 1245, 1230, 1202, 1168, 1121, 1059, 1014, 967, 917, 863 (C=C), 809 (C=C), 773 (C=C), 719 (C=C) cm^-1. Anal. Calcd for C₂₀H₁₇Br: m/z (%) = C, 71.2; H, 5.08. Found: C, 69.32; H, 5.07.
3-[2′-(1 H -Inden-3′′-yl)ethyl]-5-(4′′′-vinylphenyl)-1 H -indene (8): mp 104 °C(hexane).¹H NMR (CDCl₃): δ = 7.75 (s, 1 H), 7.60 (d, 2 H, J = 8 Hz), 7.59 (dd, 1 H, J = 8, 8 Hz), 7.52-7.42 (m, 5 H), 7.35 (t, 1 H, J = 7, 7 Hz), 7.25 (t, 1 H, J = 7 Hz), 6.85-6.75 (q, 1 H, J = 18 Hz), 6.35 (s, 1 H), 6.33 (s, 1 H), 5.85-5.78 (d, 1 H, J = 18 Hz), 5.32-5.25 (d, 1 H, J = 11 Hz), 3.45 (s, 2 H), 3.38 (s, 2 H), 2.90 (s, 4 H). ¹³C NMR (CDCl₃): δ = 197.9, 145.3, 144.8, 144.5, 144.1, 144, 137.3, 136.5, 136.2, 128.5, 128.0, 127.4, 127.2, 126.6, 126, 125.1, 124.6, 123.8, 122.5, 119.1, 118.9, 113.6, 37.9, 37.8, 26.3. IR (NaBr): 3049, 2920, 1715, 1603 (C=C), 1460, 1396, 1265, 1167, 1060, 914, 821, 770, 736 cm^-1. MS: m/z = 359 [M - 1]⁺, 333 [Ind - (CH₂)₂ - Ind - C₆H₄]⁺, 218 [Ind - C₆H₄ - CH=CH₂]⁺.
3-(2′-Hydroxyhexen-5′-yl)-1 H -indene (11): ¹H NMR (CDCl₃): δ = 7.55 (d, 1 H, J = 7 Hz), 7.45 (d, 1 H, J = 7 Hz), 7.31 (t, 1 H, J = 8 Hz), 7.24 (t, 1 H, J = 8 Hz), 6.40 (s, 1 H), 5.95-5.85 (dq, 1 H, J = 5 Hz), 5.20-5.00 (dd, 2 H, J = 17, 10 Hz), 4.00 (br s, 1 H), 3.45-3.35 (s, 2 H), 2.90-2.85 (d, 1 H, J = 12 Hz), 2.80-2.75 (dd, 1 H, J = 16, 8 Hz), 2.40-2.20 (m, 2 H), 1.90-1.80 (s, 1 H), 1.80-1.75 (t, 2 H, J = 8 Hz). ¹³C NMR (CDCl₃): δ = 145.0, 144.5, 141.1, 138.5, 130.8, 126.1, 124.8, 123.9, 119.2, 114.9, 69.5, 37.9, 36.3, 36.2, 30.2. MS: m/z = 214 [M]⁺, 197 [Ind - CH(CH₂)₂ - (CH₂)₂ - CH=CH₂]⁺, 184 [Ind - CH(CH₂)₂ - (CH₂)₂ - CH₂]⁺.
3-(2′-Iodohexen-5′-yl)-1 H -indene (12): ¹H NMR (CDCl₃): δ = 7.60 (d, 1 H, J = 7 Hz), 7.45-7.40 (m, 2 H), 7.40-7.35 (m, 1 H), 6.45 (s, 1 H), 5.95-5.85 (dq, 1 H, J = 7 Hz), 5.25-5.10 (dd, 2 H, J = 15, 8 Hz), 4.65 (m, 1 H), 3.50-3.30 (m, 3 H), 3.35-3.25 (m, 1 H), 2.60-2.50 (m, 1 H), 2.40-2.30 (m, 1 H), 2.15-1.95 (dm, 2 H). ¹³C NMR (CDCl₃): δ = 144.7, 144.4, 142.3, 136.9, 130.8, 126.2, 125.0, 124.1, 118.9, 115.9, 40.2, 39.2, 38.1, 34.6, 34.0. IR: 3076, 3011, 2974, 2904, 2847, 2774, 1642, 1601, 1462, 1429, 1388, 1303, 1245, 1151, 996, 963, 923, 771, 747, 722, 694 cm^-1. MS: m/z = 324 [M]⁺, 197 [Ind - CH(CH₂)C₄H₇]⁺.
1,2-Bis(1H-inden-3′-yl)-hexene-5 (13): ¹H NMR (CDCl₃): δ = 7.50-7.47 (d, 1 H, J = 8 Hz), 7.46-7.44. (d, 2 H, J = 8 Hz) 7.40-7.35 (d, 1 H, J = 7 Hz), 7.35-7.25 (t, 2 H, J = 7 Hz), 7.25-7.15 (dd, 2 H, J = 8 Hz, 8 Hz), 6.28-6.25 (s, 1 H), 6.20-6.15 (s, 1 H), 5.80-5.75 (dq, 1 H, J = 6 Hz), 4.95-4.85 (dd, 2 H, J = 17, 10 Hz), 3.35-3.32 (s, 2 H) 3.30-3.27 (s, 1 H), 3.25-3.20 (t, 1 H, J = 7 Hz), 3.05-2.95 (m, 1 H), 2.95-2.85 (dd, 1 H, J = 8, 7 Hz), 2.15-2.05 (m, 1 H), 2.10-2.00 (m, 1 H), 1.90-1.85 (q, 2 H, J = 7 Hz). ¹³C NMR (CDCl₃): δ = 147.6, 145.7, 145.1, 144.8, 144.4, 142.6, 138.8, 129.3, 127.9, 125.9, 125.8, 124.4, 124.4, 123.8, 123.7, 119.4, 118.9, 114.4, 37.8, 37.7, 36.3, 33.1, 32.8, 31.5. IR: 3068, 3007, 2974, 2917, 2851, 2765, 1642, 1605, 1458, 1388, 1021, 992, 972, 910, 771, 718 cm^-1. MS: m/z = 311 [M]⁺.