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Synlett 2004(4): 667-670  
DOI: 10.1055/s-2004-817777
LETTER
© Georg Thieme Verlag Stuttgart · New York

An Easily Assembled Highly Active Ruthenium Initiator for Olefin Metathesis

Nicole Buschmann, Hideaki Wakamatsu, Siegfried Blechert*
Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
Fax: +49(30)31423619; e-Mail: blechert@chem.tu-berlin.de;
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Publication History

Received 22 October 2003
Publication Date:
10 February 2004 (online)

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Abstract

A practical and easily assembled synthesis of new ruthenium alkylidene precatalyst 8 is described, which exhibits excellent metathesis activity in ring-closing and ring-opening cross meta­thesis processes.

Key words

catalysis - metathesis - ring-closing - ring-opening - ruthenium

    References

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7

Procedure for the Preparation of Catalyst 8: To a solution of 7 (136 mg, 0.71 mmol) in CH2Cl2 (35 mL) was added CuCl (38 mg, 0.39 mmol) and 1 (300 mg, 0.35 mmol) under an atmosphere of N2. The reaction mixture was stirred for 1 h at 40 °C, concentrated, dissolved in a minimal volume of CH2Cl2 and passed through a Pasteur pipette containing a plug of cotton, and then concentrated. The residue was purified by column chromatography on silica gel (hexane/MTBE 2:1) to give 8 (188 mg, 81%) as a green solid. IR (ATR): ν = 3482 (w), 2971 (s), 2918 (s), 1701 (m), 1607 (w), 1574 (s), 1475 (s), 1445 (s), 1267 (ss), 1106 (s), 852 (w), 759 (w) cm-1. 1H NMR (500 MHz, CD2Cl2): δ = 1.15 [d, J = 6 Hz, 6 H, OCH(CH3)2], 2.40 (br s, 18 H, CH3-Mes), 3.78 (s, 3 H, OCH3), 4.14 (s, 4 H, H-2), 5.69 [qsep, J = 6, 6 Hz, 1 H, OCH(CH3)2], 6.54 (d, J = 8 Hz, 1 H, CH-Ar), 6.88 (dd, J = 8, 8 Hz, 1 H, CH-Ar), 7.06 (br s, 4 H, CH-Mes), 7.15 (d, J = 8 Hz, 1 H, CH-Ar), 16.51 (s, 1 H, H-3). 13C NMR (126 MHz, CD2Cl2): δ = 18.4 (CH3, Mes), 20.2 (CH3, Mes), 20.9 [CH3, OCH(CH3)2], 21.6 [CH3, OCH(CH3)2], 51.5 (br, CH2, C-2), 56.3 (CH3, OCH3), 80.5 [CH, OCH(CH3)2], 114.1 (CH, Ar), 115.4 (CH, Ar), 123.4 (CH, Ar), 129.2 (br, CH, Mes), 138.8 (Cq), 138.9 (Cq), 139.7 (Cq), 139.9 (Cq), 147.6 (Cq), 149.6 (Cq), 210.6 (Cq, C-2), 297.6 (CH, C-3). LRMS (FAB): m/z (%) = 656 (2) [M+], 578 (6), 541 (2), 441 (5), 405 (34) 307 (37), 147 (22), 109 (23), 91 (42), 69 (78), 55 (100). Anal. Calcd for C32H40N2O2Cl2Ru: C, 58.53; H, 6.14; N, 4.27. Found: C, 58.18; H, 5.90; N, 4.51.

8

General Procedure for RCM: The acyclic 11, 13, 15, 16, 18 diene was dissolved in dry CH2Cl2 (0.05 M) at r.t., 8 (0.1-0.5 mol%) was added and the solution was sirred for 10-20 min at r.t. Subsequently the reaction mixture was quenched using freshly distilled ethyl vinyl ether and concentrated. The crude product was purified by FC on silica gel (hexane/EE or hexane/MTBE), respectively.

9

General Procedure for ROM-CM: The Oxanorbornene derivative 20 was dissolved in dry CH2Cl2 (0.05 M) at r.t., 2 equiv of the desired cross metathesis partner 21a-d and 8 (0.05-3.00 mol%) were added and the solution was stirred for 5 min at r.t. (21d: 14 h at reflux). Subsequently, the reaction mixture was quenched using freshly distilled ethyl vinyl ether and concentrated. The crude product 22a-d [15] was purified by FC on silica gel (hexane/EE or hexane/MTBE).

15

Selected spectroscopic data:
Compound 22b: IR (ATR): ν = 2954 (s), 2928 (s), 2857 (s), 1720 (s), 1643 (w), 1472 (m), 1255 (s), 1089 (s), 836 (ss) cm-1. 1H NMR (500 MHz, CDCl3, E/Z = 1:1): δ = 0.02-0.06 [m, H, OSi(CH 3)2], 0.88 [m, 18 H, OSiC(CH 3)3], 2.11-2.54 (m, 8 H, H-4, H-, H-9, H-10 and H-12), 3.62-3.77 (m, 2 H, H-13 and H-14), 4.19 (dd, J = 7, 7 Hz, 0.5 H, H-6), 4.26 (m, 1 H, H-3), 4.61 (dd, J = 7 Hz, 0.5 H, H-6), 5.09 (br dd, J = 10, 5 Hz, 1 H, H-1, Z), 5.23 (d, J = 17 Hz, 1 H, H-1, E), 5.42-5.53 (m, 1.5 H, H-7 and H-8), 5.65 (dt, J = 15, 7 Hz, 0.5 H, H-8, E), 5.86 (m, 1 H, H-2). 13C NMR (125.8 MHz, CDCl3): δ = -5.6, -5.6, -5.5 [CH3, OSi(CH3)2], 18.1, 18.1 [Cq, OSiC(CH3)3], 21.9 (CH2), 25.8 [CH3, OSiC(CH3)3], 26.3 (CH2), 29.9, 29.9 (CH, C-12), 43.0, 43.5, (CH2), 48.9, 49.0, 49.1, 49.8 (CH, C-4 and C-5), 60.5, 60.6, 60.8, 60.9 (CH2, C-13 and C-14), 76.3, 81.8, 82.2, 82.3 (CH, C-3 and C-6), 115.3, 115.5 (CH2, C-1), 131.0, 131.0, 131.8, 131.9 (CH, C-7 and C-8), 139.4, 139.6 (CH, C-2). LRMS (EI): m/z (%) = 482 (<1) [M+], 425 (42), 189 (31), 147 (67), 89 (67), 73 (100). HRMS: m/z calcd for C26H50O4Si2 [M+]: 482.3248; found: 482.3259. Anal. Calcd for C26H50O3Si2: C, 64.67; H, 10.44. Found: C, 64.63; H, 10.21.
Compound 22c: IR (ATR): ν = 2954 (s), 2929 (s), 2857 (s), 1644 (w), 1255 (s), 1090 (s), 837 (ss) cm-1. 1H NMR (500 MHz, CDCl3, two diastereomers 1:1, E/Z = 4:1): δ = 0.04 [br s, 12 H, OSi(CH 3)2], 0.88 [br s, 18 H, OSiC(CH 3)3], 2.14-2.23 (m, 2 H), 2.59-2.63 (m, 1 H), 2.79 (dt, J = 4, 4 Hz, 1 H), 3.14 (m, 1 H), 3.34-3.45 (m, 1 H), 3.63-3.85 (m, 5 H), 3.99-4.49 (m, 3 H), 4.59 (br t, J = 6 Hz, 1 H), 5.07 (br d, J = 10 Hz, 0.2 H), 5.11 (dd, J = 10, 4 Hz, 0.8 H), 5.22 (br d, J = 17 Hz, 0.2 H), 5.24 (br d, J = 17 Hz, 0.8 H), 5.54-5.79 (m, 2 H), 5.84 (m, 1 H, H-2). 13C NMR (125.8 MHz, CDCl3): δ = -5.6, -5.5, -5.5, -5.5, [CH3, OSi(CH3)2], 18.1, 18.2 [Cq, OSiC(CH3)2], 25.8, 25.8, 25.9, 26.0 [CH3, OSiC(CH3)2], 44.3, 44.4, 44.4 (CH2, C-12), 48.9, 49.0, 49.1, 49.7, 49.9, 50.6, 50.7, 50.8 (CH, C-4, C-5 and C-11), 60.2, 60.6, 60.7, 60.7, 60.8, 61.0, 61.1, 61.3 (CH2, C-13 and C-14), 67.0, 67.1, 70.6, 70.6, 70.8, 71.3, 71.3, 71.4 (CH2, C-9 and C-10), 76.1, 76.7, 81.1, 81.3, 81. 7, 82.3, 82.4, 82.7(CH, C-3 and C-6), 115.0, 115.5, 115.7 (CH2, C-1), 127.5, 127.5,128.6, 128.7, 133.8, 133.9, 134.4, 134.4 (CH, C-7 and C-8), 139.2, 139.4, 139.7 (CH, C-2). LRMS (EI): m/z (%) = 455 (8) [M+ - (tert-Bu)], 189 (20), 147 (48), 131 (100), 89 (84), 73 (95). HRMS: m/z calcd for C23H43O5Si2 [M+ - (tert-Bu)]: 455.2649; found: 455.2651. Anal. Calcd for C27H52O5Si2: C, 63.23; H, 10.22. Found: C, 63.10; H, 9.86.
Compound 22d: IR (ATR): ν = 2954 (s), 2928 (s), 2857 (s), 1644 (w), 1472 (m), 1252 (s), 1087 (s), 836 (ss) cm-1. 1H NMR (500 MHz, CDCl3, E/Z = 1/1): δ = 0.03 [s, 3 H, OSi(CH 3)2], 0.04 [s, 3 H, OSi(CH 3)2], 0.04 [s, 3 H, OSi(CH 3)2], 0.05 [s, 3 H, OSi(CH 3)2], 0.12 (s, 3 H, H-10), 0.14 (s, 1.5 H, H-10), 0.15 (s, 1.5 H, H-10), 0.89 [s, 9 H, OSiC(CH 3)3], 0.90 [s, 4.5 H, OSiC(CH 3)3], 0.90 [s, 4.5 H, OSiC(CH 3)3], 1.58-1.66 (m, 1.5 H, H-9), 1.73 (dd, J = 9, 2 Hz, 0.5 H, H-9), 2.09-2.23 (m, 5 H, H-4, H-5 and H-13), 2.62 (t, J = 7 Hz, 2 H, H-12), 3.63-3.80 (m, 6 H, H-11, H-14 and H-15), 4.19 (t, J = 8 Hz, 0.5 H, H-6), 4.27 (dt, J = 6, 7 Hz, 1 H, H-3), (dd, J = 8, 7 Hz, 0.5 H, H-6), 5.08 (dd, J = 10, 4 Hz, 1 H, H-1, Z), 5.23 (ddt, J = 17, 8, 2 Hz, 1 H, H-1, E), 5.34-5.41 (m, 1 H, H-7), 5.56 (dt, J = 10, 9 Hz, 0.5 H, H-8, Z), (dt, J = 16, 8 Hz, 0.5 H, H-8, E), 5.87 (dddd, J = 17, 10, 6, 2 Hz, 1 H, H-2). 13C NMR (125.8 MHz, CDCl3): δ = -5.5, -5.5, -5.5 [CH3, OSi(CH3)2], -2.4, -2.4, 2.3, 2.3 (CH3, C-10), 16.1, 16.1 (CH3, C-13), 18.1, 18.2 [Cq, OSiC(CH3)3], 18.9, 22.4 (CH2, C-9), 25.8, 25.9, 25.9 [CH3, OSiC(CH3)3], 36.3, 36.3 (CH2, C-12), 49.0, 49.0, 49.1, 50.1 (CH, C-4 and C-5), 60.5, 60.6, 60.9, 61.0 (C-14 and C-15), 62.4, 62.4 (CH2, C-11), 76.3, 82.0, 82.0, 82.1 (CH, C-3 and C-6), 115.1, 115.2 (CH2, C-1), 127.7, 128.2 (CH, C-8), 129.7, 130.6 (CH, C-7), 139.7, 139.9 (CH, C-2). LRMS (EI): m/z (%) = 574 (<1) [M+], 223 (3), 189 (4), 149 (100), 133 (6), 89(8), 75 (23). HRMS: m/z calcd for C28H58O4SSi3 [M+]: 574.3364; found: 574.3371.