Synlett 2008(12): 1813-1816  
DOI: 10.1055/s-2008-1078570
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Immobilization of Grubbs Catalyst as Supported Ionic Liquid Catalyst (Ru-SILC)

Hisahiro Hagiwara*a, Naotaro Okunakaa, Takashi Hoshib, Toshio Suzukib
a Graduate School of Science and Technology, Niigata University, 8050, 2-Nocho, Ikarashi, Nishi-ku, Niigata 950-2181, Japan
e-Mail: hagiwara@gs.niigata-u.ac.jp;
b Faculty of Engineering, Niigata University, 8050, 2-Nocho, Ikarashi, Nishi-ku, Niigata 950-2181, Japan
Further Information

Publication History

Received 16 April 2008
Publication Date:
02 July 2008 (online)

Abstract

Grubbs olefin metathesis catalyst was immobilized as a ruthenium-supported ionic liquid catalyst (Ru-SILC) in pores of amorphous alumina with the aid of ionic liquid [hmim]PF6. This Ru-SILC was effective for various olefin metathesis reactions such as intra- or intermolecular macrocyclization and dimerization, and used up to six times after simple decantation.

6

Hagiwara, H.; Katsumi, T. unpublished results.

20

Preparation of Ru-SILC
To activated Al2O3 (powder for column chromatography purchased from Wako Chemical Co., 300 mesh, 1.545 g) and Grubbs I catalyst (1, 38 mg, 0.046 mmol, 0.03 mmol/g of Al2O3) was added a solution of [hmim]PF6 (150 mg, 10 wt%) in THF. The resulting slurry was stirred at r.t. for 4 h, when the pale blue color of THF solution was transferred to Al2O3. After evaporation of THF in vacuo, the powder was rinsed with anhyd Et2O twice. Evacuation in vacuo provided Ru-SILC (1.732 g) as a pale blue powder. Since leaching of Ru into the ether rinse was 0.05 ppm (0.105% as the catalyst 1) by ICP-AES analysis, more than 99% of Grubbs I catalyst(1) was immobilized on Al2O3.

21

RCM Reaction of Diethyl Diallylmalonate 4 A stirred suspension of diethyl 2,2-diprop-2-enylpropane-1,3-dioate (4, 31 mg, 0.13 mmol) and Ru-SILC [308 mg, 0.0065 mmol of Grubbs I catalyst(1)] in benzene (1.5 mL) was heated under reflux for 1 h. The organic layer was separated by filtration, and the flask was rinsed with Et2O. The combined organic layer was evaporated to dryness in vacuo. The residue was purified by medium pressure LC (eluent: n-hexane-EtOAc = 9:1) to give ethyl 1-(ethoxy-carbonyl)cyclopent-3-enecarboxylate (5, 23 mg, 82%). Recovered Ru-SILC was used intact for further recycle experiments.

22

Compound 13: ¹H NMR (500 MHz, CDCl3): δ = 1.19-1.47 (m, 20 H), 1.82-2.12 (m, 8 H), 4.13-4.19 (m, 4 H), 5.24-5.33 (m, 1 H), 5.49-5.55 (m, 0.3 H), 5.57-5.63 (m, 0.7 H). ¹³C NMR (67.5 MHz, CDCl3): δ = 171.9, 131.5, 130.7, 61.0, 56.5, 31.2, 30.4, 30.3, 28.4, 27.3, 27.0, 26.0, 24.5, 24.2, 20.7, 14.2. MS: m/z (%) = 338 (67) [M+], 293 (90), 265 (27), 246 (100), 218 (100), 191 (100), 173 (100), 168 (91). IR: 1723, 1464, 1448, 1368, 1260, 1231, 1190 cm. HRMS: m/z calcd for C20H34O4 [M]+: 338.2457; found: 338.2458.

23

Compound 17: ¹H NMR (270 MHz, CDCl3): δ = 1.21-1.28 (m, 20 H), 1.84-2.00 (m, 16 H), 4.14-4.22 (m, 8 H), 5.39-5.42 (m, 4 H). ¹³C NMR (67.5 MHz, CDCl3): δ = 171.7, 130.1, 61.1, 57.0, 32.1, 30.2, 23.5, 14.2. MS: m/z (%) = 536 (7) [M+], 491 (13), 444 (8), 399 (15), 336 (19), 279 (8), 265 (16), 251 (12), 173 (100). IR: 1719, 1463, 1445, 1369, 1299, 1254, 1095, 1028 cm. HRMS: m/z calcd for C28H43O7 [M - OCH2CH3]+: 491.3009; found: 491.3017.

24

Compound 19: ¹H NMR (500 MHz, CDCl3): δ = 1.21-1.34 (m, 14 H), 1.55-1.67 (m, 4 H), 1.73-2.05 (m, 12 H), 2.43-2.60 (m, 4 H), 3.39-3.45 (m, 2 H), 4.14-4.19 (m, 4 H), 5.34-5.42 (m, 4 H). ¹³C NMR (67.5 MHz, CDCl3): δ = 205.1, 169.7, 130.3, 129.5, 61.2, 58.3, 41.4, 32.3, 31.8, 28.9, 27.9, 27.4, 23.0, 14.2. MS: m/z (%) = 476 (3) [M+], 431 (7), 412 (16), 402 (4), 384 (15), 366 (11), 175 (19), 108 (45), 91 (51), 79 (73), 67 (95), 55 (100). IR: 1738, 1710, 1445, 1370, 1268, 1188, 909 cm. HRMS: m/z calcd for C26H39O5 [M - OCH2CH3]+: 431.2797; found: 431.2802.

25

Compound 21: ¹H NMR (500 MHz, CDCl3): δ = 1.25-1.28 (m, 12 H), 1.34-1.41 (m, 4 H), 1.86-1.92 (m, 4 H), 1.99-2.07 (m, 4 H), 3.29-3.33 (m, 2 H), 4.16-4.23 (m, 8 H), 5.34-5.36 (m, 0.6 H), 5.37-5.39 (m, 1.4 H). ¹³C NMR (67.5 MHz, CDCl3): δ = 169.3, 129.9, 61.3, 51.9, 32.2, 28.3, 27.3, 14.2. IR: 1726, 1462, 1446, 1371, 1178, 1157 cm. MS: m/z (%) = 428 (3) [M+], 383 (5), 337 (100), 269 (70), 227 (10), 173 (72), 160 (86), 130 (50). HRMS: m/z calcd for C22H36O8 [M]+: 428.2410; found: 428.2394.