Synlett 2008(4): 561-564  
DOI: 10.1055/s-2008-1032096
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Silole Skeletons via Metathesis Reactions

Takanori Matsuda, Yoshiyuki Yamaguchi, Masahiro Murakami*
Department of Synthetic Chemistry and Biological Chemistry, Kyoto University, Katsura, Kyoto 615-8510, Japan
Fax: +81(75)3832752; e-Mail: murakami@sbchem.kyoto-u.ac.jp;
Further Information

Publication History

Received 6 November 2007
Publication Date:
12 February 2008 (online)

Abstract

Silole skeletons are constructed by ring-closing olefin metathesis of silicon-tethered dienes and trienes. A silicon-tethered enyne is also converted to a 2-alkenyl-1-silaindene via ruthenium-catalyzed ring-closing enyne metathesis.

7

Preparation of Siladienes 1Dimethyl(1-phenylvinyl)(2-vinylphenyl)silane (1a)
To a solution of chlorodimethyl(2-vinylphenyl)silane (2.0 g, 10.2 mmol) in THF (10 mL) was added a solution of (1-phenylvinyl)magnesium bromide in THF, which was prepared from α-bromostyrene (5.0 g, 27.3 mmol) and Mg (0.68 g, 28 mmol) in THF (20 mL) at r.t. for 3 h, at 0 °C. After the mixture was stirred at r.t. for 10 h, the volatile materials were removed under reduced pressure. The residue was quenched by sat. NH4Cl aq solution, and extracted with hexane. The extract was dried over MgSO4 and concentrated. The residue was purified by column chromatography on silica gel(hexane). Further purification by gel-permeation chromatography (GPC) gave 1a (500 mg, 19%): 1H NMR (300 MHz, CDCl3): d = 0.45 (s, 6 H), 5.22 (dd, J = 11.0, 1.3 Hz, 1 H), 5.61 (dd, J = 17.4, 1.3 Hz, 1 H), 5.69 (d, J = 2.9 Hz, 1 H), 6.01 (d, J = 2.9, 1 H), 7.07-7.29 (m, 7 H), 7.35-7.41 (m, 1 H), 7.54-7.59 (m, 2 H). 13C NMR (75 MHz, CDCl3): d = -1.0, 114.9, 125.2, 126.4, 126.8, 126.9, 128.1, 129.0, 129,6, 135.1, 136.0, 138.0, 134.9, 144.0, 151.5. HRMS (EI): m/z [M]+ calcd for C18H20Si: 264.1334; found: 264.1335.
Isopropenyldimethyl(2-vinylphenyl)silane (1c)
1H NMR (300 MHz, CDCl3): d = 0.40 (s, 6 H), 1.80 (t, J = 1.4 Hz, 3 H), 5.22 (dd, J = 10.8, 1.2 Hz, 1 H), 5.36 (q, J = 0.9 Hz, 1 H), 5.64 (dd, J = 17.3, 1.2 Hz, 1 H), 5.69 (sext, J = 1.7 Hz, 1 H), 7.04 (dd, J = 17.3, 10.8 Hz, 1 H), 7.25 (dt, J = 1.3, 7.3 Hz, 1 H), 7.37 (dt, J = 1.5, 7.5 Hz, 1 H), 7.50 (dd, J = 7.4, 1.4 Hz, 1 H), 7.56 (d, J = 7.5 Hz, 1 H). 13C NMR (75 MHz, CDCl3): d = -2.1, 22.6, 114.7, 125.0, 126.5, 126.9, 129.5, 135.0, 135.7, 138.0, 144.1, 146.6. HRMS (EI): m/z [M]+ calcd for C13H18Si: 202.1178; found: 202.1173.
Dimethyl(1-phenylvinyl)(2-vinylphenyl)germane (1k)
1H NMR (300 MHz, CDCl3): d = 0.57 (s, 6 H), 5.22 (dd, J = 10.5, 1.5 Hz, 1 H), 5.55 (d, J = 2.1 Hz, 1 H), 5.63 (dd, J = 17.4, 1.2 Hz, 1 H), 6.03 (d, J = 2.1 Hz, 1 H), 6.98 (dd, J = 17.4, 11.1 Hz, 1 H), 7.15-7.28 (m, 6 H), 7.32-7.38 (m, 1 H), 7.49-7.53 (m, 1 H), 7.56-7.60 (m, 1 H). 13C NMR (75 MHz, CDCl3): d = -1.1, 115.0, 125.1, 126.0, 126.6 [overlapping], 127.1, 128.2, 129.1, 134.3, 137.8, 139.0, 143.2, 143.5, 152.2. HRMS (EI): m/z [M]+ calcd for C18H20Ge: 310.0777; found: 310.0786.

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General Procedure for Ring-Closing Metathesis1,1-Dimethyl-2-phenyl-1-silaindene (2a) 14
To Schrock catalyst (11.5 mg, 0.015 mmol) was added a solution of 1a (76.45 mg, 0.289 mmol) in toluene (5 mL), and the mixture was stirred at r.t. for 2 h. The reaction mixture was taken up with hexane and passed through a pad of Florisil®. Removal of volatile materials afforded 2a (61.4 mg, 0.257 mmol, 89%): 1H NMR (300 MHz, CDCl3): δ = 0.48 (s, 6 H), 7.20-7.40 (m, 6 H), 7.49-7.56 (m, 4 H). 13C NMR (75 MHz, CDCl3): d = -3.1, 124.3, 126.4, 126.6, 127.0, 128.7, 130.0, 131.7, 138.2, 139.0, 141.1, 145.3, 148.8. 29Si NMR (79 MHz, CDCl3): d = -15.9. HRMS (EI): m/z [M]+ calcd for C16H16Si: 236.1021; found: 236.1019.
2-(3-Methoxyphenyl)-1,1-dimethyl-1-silaindene (2b)
To Grubbs second-generation catalyst (8.7 mg, 0.010 mmol) was added a solution of 1b (58.62 mg, 0.199 mmol) in toluene (2 mL), and the mixture was stirred at 80 °C for 2 h. The reaction mixture was taken up with hexane and passed through a pad of Florisil® (hexane-EtOAc = 10:1). After removal of volatile materials, the residue was subjected to preparative thin-layer chromatography to give 2b (50.66 mg, 0.190 mmol, 96%): 1H NMR (300 MHz, CDCl3): d = 0.49 (s, 6 H), 3.87 (s, 3 H), 6.79-6.85 (m, 1 H), 7.04-7.11 (m, 2 H), 7.19-7.39 (m, 4 H), 7.53-7.57 (m, 2 H). 13C NMR (75 MHz, CDCl3): d = -3.1, 55.2, 111.9, 112.4, 119.3, 124.3, 126.7, 129.6, 130.0, 131.7, 138.3, 140.5, 141.5, 145.2, 148.7, 159.8. HRMS (EI): m/z [M]+ calcd for C17H18OSi: 266.1127; found: 266.1121.
1,1,2-Trimethyl-1-silaindene (2c)
1H NMR (300 MHz, CDCl3): d = 0.28 (s, 6 H), 2.02 (d, J = 1.5 Hz, 3 H), 6.86 (q, J = 1.5 Hz, 1 H), 7.10-7.15 (m, 2 H), 7.24-7.30 (m, 1 H), 7.46 (d, J = 6.9 Hz, 1 H). 13C NMR (75 MHz, CDCl3): d = -4.6, 17.4, 122.8, 125.6, 129.7, 131.6, 138.1, 142.7, 144.6, 149.5. HRMS (EI): m/z [M]+ calcd for C11H14Si: 174.0865; found: 174.0864.
1,1,3-Trimethyl-1-silaindene (2d)
1H NMR (300 MHz, CDCl3): δ = 0.29 (s, 6 H), 2.22 (s, 3 H), 5.92 (s, 1 H), 7.21-7.27 (m, 1 H), 7.30-7.40 (m, 2 H), 7.51-7.55 (m, 1 H). 13C NMR (75 MHz, CDCl3): δ = -4.0, 19.6, 121.2, 126.5, 127.8, 129.4, 131.2, 139.8, 149.9, 156.2. 29Si NMR (79 MHz, CDCl3): δ = -19.4. HRMS (EI): m/z [M]+ calcd for C11H14Si: 174.0865; found 174.0864.
1,1-Diethyl-2-phenyl-1-silaindene (2i)
1H NMR (300 MHz, CDCl3): d = 0.85-1.15 (m, 10 H), 7.18-7.58 (m, 10 H). 13C NMR (75 MHz, CDCl3): d = 4.3, 7.5, 124.2, 126.39, 126.45, 126.9, 128.6, 129.9, 132.3, 136.3, 139.5, 142.4, 143.7, 149.7. 29Si NMR (79 MHz, CDCl3): d = -8.7. HRMS (EI): m/z [M]+ calcd for C18H20Si: 264.1334; found 264.1332.
1,1-Dimethyl-2-phenyl-1-germaindene (2k)
1H NMR (300 MHz, CDCl3): d = 0.67 (s, 6 H), 7.20-7.41 (m, 6 H), 7.47-7.58 (m, 4 H). 13C NMR (75 MHz, CDCl3): d = -2.2, 125.0, 126.6, 126.8, 127.1, 128.7, 129.3, 131.8, 137.8, 139.3, 140.5, 147.6, 148.0. HRMS (EI): m/z [M]+ calcd for C16H16Ge: 282.0464; found: 282.0469.

11

Dimethyl(1-phenylvinyl)(2-vinylcyclopent-1-enyl)silane (3a)
A solution of (2-vinylcyclopent-1-enyl)lithium in THF, which was prepared from 1-bromo-2-vinylcyclopent-1-ene (0.69 g, 3.99 mmol) and n-BuLi in hexane (1.55 M, 2.8 mL, 4.34 mmol) in THF (10 mL) at -78 °C for 1 h, was added to a solution of chlorodimethyl(1-phenylvinyl)silane (0.697 g, 3.54 mmol) in THF (10 mL) at 0 °C. After the mixture was stirred at r.t. for 10 h, the volatile materials were removed under reduced pressure. The residue was quenched by sat. NH4Cl aq solution, and extracted with hexane. The extract was dried over MgSO4 and concentrated. The residue was purified by column chromatography on silica gel (hexane) to afford 3a (0.32 mg, 32%): 1H NMR (300 MHz, CDCl3): d = 0.29 (s, 6 H), 1.82 (quin, J = 7.5 Hz, 2 H), 2.47-2.60 (m, 4 H), 5.09 (d, J = 10.7 Hz, 1 H), 5.13 (d, J = 17.1 Hz, 1 H), 5.65 (d, J = 3.0 Hz, 1 H), 5.92 (d, J = 3.0 Hz, 1 H), 6.80 (dd, J = 17.1, 10.7 Hz, 1 H), 7.15-7.30 (m, 5 H). 13C NMR (75 MHz, CDCl3): d = -1.2, 23.6, 34.6, 39.3, 115.3, 126.6, 127.0. 128.2. 128.3, 134.3, 140.9, 144.5, 151.9, 152,7. HRMS-FAB: m/z calcd for C17H22Si [M+] 254.1491; found: 254.1476.
Dimethyl(1-phenylvinyl)(2-vinyl-3,4-dihydronaph-thalen-1-yl)silane (3b)
1H NMR (300 MHz, CDCl3): d = 0.45 (s, 6 H), 2.31-2.38 (m, 2 H), 2.58-2.65 (m, 2 H), 5.16 (d, J = 10.8 Hz, 1 H), 5.44 (d, J = 17.1 Hz, 1 H), 5.78 (d, J = 2.7 Hz, 1 H), 5.97 (d, J = 2.7 Hz, 1 H), 6.96 (dd, J = 17.1, 11.1 Hz, 1 H), 7.09-7.26 (m, 9 H). 13C NMR (75 MHz, CDCl3): d = 2.0, 24.4, 28.5, 114.3, 125.6, 125.9, 126.4, 126.7, 126.8, 127.5, 128.0, 128.1, 135.7, 136.7, 138.1, 138.7, 143.9, 150.6, 153.3. HRMS (EI): m/z [M]+ calcd for C22H24Si: 316.1647; found: 316.1650.
1,1-Dimethyl-2-phenyl-1,4,5,6-tetrahydrocyclo-penta[ b ]silole (4a)
1H NMR (300 MHz, CDCl3): d = 0.37 (s, 6 H), 2.14 (quin, J = 7.2 Hz, 2 H), 2.48-2.59 (m, 4 H), 7.12-7.43 (m, 6 H). 13C NMR (75 MHz, CDCl3): d = -3.7, 27.0, 32.7, 32.8, 125.9, 126.4, 128.6, 134.9, 139.5, 142.9, 147.5, 161.4. HRMS-FAB: m/z [M]+ calcd for C15H18Si: 226.1178; found: 226.1187.
2-Phenyl-4,5-dihydronaphtho[1,2- b ]silole (4b)
1H NMR (300 MHz, CDCl3): d = 0.55 (s, 6 H), 2.59 (t, J = 8.4 Hz, 2 H), 2.92 (t, J = 8.1 Hz, 2 H), 7.08-7.50 (m, 10 H). 13C NMR (75 MHz, CDCl3): d = -2.7, 26.3, 28.4, 125.7, 126.1, 126.2, 126.6, 126.8, 127.86 128.7, 134.2, 134.6, 135.9, 138.7, 140.9, 144.7, 152.2. 29Si NMR (79 MHz, CDCl3): d = -16.2. HRMS (EI): m/z [M]+ calcd for C20H20Si: 288.1334; found: 288.1330.

14

1,1-Dimethyl-2-(pent-1-en-2-yl)-1-silaindene (6) and 1,1-Dimethyl-2-methylene-3-propyl-1,2-dihydro-1-silanaphthalene (7)
The title compounds (45.63 mg, 67%, 6/7 = 50:50) were obtained from enyne RCM of 5 (67.8 mg) using Ru-II. The isomers were separated by HPLC.
Compound 6: 1H NMR (300 MHz, CDCl3): δ = 0.31 (s, 6 H), 0.97 (t, J = 7.5 Hz, 3 H), 1.59 (sext, J = 7.5 Hz, 2 H), 2.43 (t, J = 7.8 Hz, 2 H), 5.61 (d, J = 1.5 Hz, 1 H), 6.03 (d, J = 1.5 Hz, 1 H), 6.29 (s, 1 H), 7.10-7.20 (m, 2 H), 7.25-7.31 (m, 1 H), 7.48 (d, J = 0.6 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = -1.3, 14.1, 22.4, 35.9, 124.7, 126.0, 128.9, 129.2, 129.6, 133.3, 133.8, 140.2, 141.9, 145.0. HRMS (EI): m/z [M]+ calcd for C15H20Si: 228.1334; found: 228.1335.
Compound 7: 1H NMR (300 MHz, CDCl3): δ = 0.43 (s, 6 H), 1.00 (t, J = 7.5 Hz, 3 H), 1.61 (sext, J = 7.5 Hz, 2 H), 2.40 (t, J = 7.8 Hz, 2 H), 5.08 (d, J = 6.6 Hz, 2 H), 7.16-7.35 (m, 4 H), 7.52-7.54 (m, 1 H). 13C NMR (75 MHz, CDCl3): δ = -2.9, 14.0, 21.6, 35.9, 115.0, 124.2, 126.5, 129.9, 131.6, 138.3, 140.5, 146.8, 147.3, 149.0. HRMS (EI): m/z [M]+ calcd for C15H20Si: 228.1334; found: 228.1333.