Cu-catalyzed regioselective carbomagnesiation of dienes and enynes with sec- and tert-alkyl Grignard reagents

Article abstract of DOI:10.1039/b716678h

The carbomagnesiation of dienes and enynes with sec- and tert-alkyl Grignard reagents has been achieved by using copper salts as catalysts. The Royal Society of Chemistry.

Full text of DOI:10.1039/b716678h

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Electronic Supplementary Information
Cu-Catalyzed Regioselective Carbomagnesiation
of Dienes and Enynes with sec- and tert-Alkyl Grignard Reagents
Hirohisa Todo, Jun Terao, Hideyuki Watanabe, Hitoshi Kuniyasu, Nobuaki Kambe
Department of Molecular Chemistry & Science and Technology Center for Atoms,
Molecules and Ions Control, Graduate School of Engineering, Osaka University,
Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
Typical Experimental Procedures and Analytical Data of Products.
General
1H NMR and 13C NMR spectra were recorded with a JEOL JNM-Alice 400
spectrometer (400 MHz and 100 MHz, respectively). Chemical shifts are given in
parts per million (d) downfield from internal tetramethylsilane. Infrared spectra were
obtained with a Perkin-Elmer FT-IR (Model 1600). Both conventional and high
resolution mass spectra were recorded with a JEOL JMS-DX303HF spectrometer. GC
Mass analyses (EI) were run using a SATURN GCMS-2000 operating in the electron
impact mode (70 eV) equipped with a RTX-5 30MX.25MMX.25U column. The
HPLC separation was performed on a recycling preparative HPLC (Japan Analytical
Industry Co. Ltd., Model LC-908) equipped with JAIGEL-1H and -2H columns (GPC)
using CHCl3 as the eluent.
Elemental analyses were performed on a Perkin Elmer
240C apparatus. Grignard reagents were used as purchased. NMR yields were
determined using dioxane as an internal standard.
A Typical Procedure
2,2-Dimethyl-hexadec-4-ene (4)
A solution of tert-BuMgCl (0.8 M, 1.9 mL, 1.5 mmol) in THF was cooled to -78 °C
under nitrogen and 1,3-butadiene (22.4 mL, 1.0 mmol) and a catalytic amount of
Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added to the solution at -78 °C, and the
mixture was stirred for 3 h at 25 °C. Then decyl bromide (332.1 mg, 1.5 mmol) was
added to the solution at 0 °C. After stirring for 1 h at 25 °C, ca. 2 mL of 1 N HClaq was
added to the solution at 0 °C, and the mixture was warmed to 25 °C. A saturated

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aqueous NH4Cl solution (10 mL) was added, and the product was extracted with ether
(10 mL). The organic layer was dried over MgSO4, and evaporated to give a pale yellow
crude product (87 % NMR yield). Purification by HPLC with CHCl3 as an eluent
afforded 207 mg (82 %) of 4. IR (neat): 2955, 2924, 2854, 1466, 1364, 1240, 969 cm-1;
1H NMR (400 MHz, CDCl3): δ = 5.46-5.33 (m, 2H), 1.99 (q, J = 6.4 Hz, 2H), 1.85 (d, J
= 6.4 Hz, 2H), 1.34-1.26 (m, 18H), 0.89 (t, J = 2.8 Hz, 3H), 0.86 (s, 9H); 13C NMR (100
MHz, CDCl3): δ = 132.6, 127.0, 47.2, 42.2, 32.8, 32.1, 29.82, 29.79, 29.65, 29.50, 29.41,
29.39, 29.29, 29.4, 22.9, 14.3; MS (EI) m/z (relative intensity, %) 252 (M+, 3), 196 (12),
111 (4), 97 (6), 83 (6), 69 (7), 57(100), 41(8); HR-MS: calcd for C18H36(M) 252.2817,
found 252.2807; elemental analysis: calcd for C18H36: C, 85.63; H, 14.37. found: C,
85.65; H, 14.08.
Tributyl-(5,5-dimethyl-hex-2-enyl)-silane (5)
A solution of tert-BuMgCl (0.8 M, 1.9 mL, 1.5 mmol) in THF was cooled to -78 °C
under nitrogen and 1,3-butadiene (22.4 mL, 1.0 mmol) and a catalytic amount of
Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added to the solution at -78 °C, and the
mixture was stirred for 3 h at 25 °C. Then Bu3SiCl (352.7 mg, 1.5 mmol) was added to
the solution at 0 °C. After stirring for 1 h at 25 °C, similar workup as mentioned above
afforded a pale yellow crude product (78 % NMR yield). Purification by HPLC with
CHCl3 as an eluent afforded 226.8 mg (73 %) of 5. IR (neat): 2955, 1464, 1194, 965,
886, 762 cm-1; 1H NMR (400 MHz, CDCl3): δ = 5.38-5.23 (m, 2H), 1.84 (d, J = 6.4 Hz,
2H), 1.45 (d, J = 7.6 Hz, 2H), 1.35-1.24 (m, 12H), 0.88 (t, J = 6.8 Hz, 9H), 0.86 (s, 9H),
0.52 (t, J = 4.8 Hz, 6H); 13C NMR (100 MHz, CDCl3): δ =128.3, 125.6, 47.6, 31.1, 29.4,
27.0, 26.2, 18.7, 14.0, 12.1; MS (EI) m/z (relative intensity, %) 310 (M+, 2), 253 (3),
199 (69), 143 (100), 101 (32), 87 (27), 59 (26); HR-MS: calcd for C20H42Si(M)
310.3056, found 310.3061; elemental analysis: calcd for C20H42Si: C, 77.33; H, 13.63.
found: C, 77.38; H, 13.61.
1-[1-(2,2-Dimethyl-propyl)-allyl]-cyclohex-2-enol (6)
A solution of tert-BuMgCl (0.8 M, 1.9 mL, 1.5 mmol) in THF was cooled to -78 °C
under nitrogen and 1,3-butadiene (22.4 mL, 1.0 mmol) and a catalytic amount of
Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added to the solution at -78 °C, and the
mixture was stirred for 3 h at 25 °C. Then cyclohexenone (144.6 mg, 1.5 mmol) was
added to the solution at 0 °C. After stirring for 1 h at 25 °C, similar workup as
mentioned above afforded a pale yellow crude product (72 % NMR yield). Purification
by HPLC with CHCl3 as an eluent afforded 143.8 mg (69 %) of 6. IR (neat): 3466, 2952,

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1
1706, 1636, 1475, 1365, 1166, 977 cm-1; H NMR (400 MHz, CDCl3): δ = 5.97-5.81 (m, 1H),
5.77-5.66 (m, 1H), 5.60-5.45 (m, 1H), 5.22-5.08 (m, 2H), 2.22-2.15 (m, 1H), 2.05-1.96 (m, 2H),
1.79 (s, 1H), 1.67-1.48 (m, 4H), 1.27-1.21 (m, 2H), 0.89 (s, 9H); 13C NMR (100 MHz, CDCl3):
δ = 140.8, 130.9, 130.1, 117.4, 70.7, 50.5, 42.1, 32.8, 31.1, 30.2, 25.2, 18.7; MS (EI) m/z
(relative intensity, %) 208 (M+, 1), 191 (3), 175 (3), 137 (2), 119 (3), 105 (2), 97 (100), 79 (10),
67 (7), 55 (8), 41 (13); HR-MS: calcd for C14H24O (M) 208.1827, found 208.1822; elemental
analysis: calcd for C14H24O: C, 80.71; H, 11.61. found: C, 80.65; H, 11.77.
2-(2,2-Dimethyl-propyl)-2,3-dimethyl-1-phenyl-but-3-en-1-one (7)
To a mixture of 2,3-dimethyl-1,3-butadiene (82.5 mg, 1.0 mmol) and a catalytic amount
of Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added tert-BuMgCl (0.8 M, 1.9 mL, 1.5
mmol) in THF, and the mixture was stirred for 3 h at 25 °C. Then benzoyl chloride
(210.9 mg, 1.5 mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C,
similar workup as mentioned above afforded a pale yellow crude product (73 % NMR
yield). Purification by HPLC with CHCl3 as an eluent afforded 168.6 mg (69 %) of 7. IR
1
(neat): 2952, 2360, 1676, 1632, 1446, 1234, 1197, 961, 882, 700cm-1; H NMR (400 MHz,
CDCl3): δ = 7.90 (d, J = 6.8 Hz, 2H), 7.44 (t, J = 7.2 Hz, 1H), 7.34 (t, J = 7.6 Hz, 2H), 5.15 (s,
1H), 5.04 (s, 1H), 2.57 (d, J = 14.8 Hz, 2H), 1.89 (d, J = 14.8Hz, 1H)1.73 (s, 9H), 1.48 (s, 3H)
13C NMR (100 MHz, CDCl3): δ = 204.6, 149.6, 138.2, 131.4, 128.7, 127.8, 111.7, 56.7, 49.3,
32.0, 24.3, 20.9; MS (EI) m/z (relative intensity, %) 244 (M+, 5), 188 (18), 170 (13), 106 (12),
105 (100), 77 (23), 57 (18); HR-MS: calcd for C17H24O(M) 244.1827, found 244.1826;
elemental analysis: calcd for C17H24O: C, 83.55; H, 9.90. found: C, 83.28; H, 9.67.
Triethyl-(2,3,5-trimethyl-hept-2-enyl)-silane (9)
To a mixture of 2,3-dimethyl-1,3-butadiene (82.5 mg, 1.0 mmol) and a catalytic amount
of Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added sec-BuMgCl (0.7 M, 2.2 mL, 1.5
mmol) in THF, and the mixture was stirred for 3 h at 25 °C. Then Et3SiCl (226.1 mg,
1.5 mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C, similar
workup as mentioned above afforded a pale yellow crude product (85 % NMR yield).
Purification by HPLC with CHCl3 as an eluent afforded 198.5 mg (78 %) of 9. IR (neat):
1
2955, 2875, 1461, 1416, 1376, 1238, 1166, 1074, 1016, 774, 738 cm-1; H NMR (400 MHz,
CDCl3): δ = 1.97 (dd, J = 13.4, 6.2 Hz, 1H), 1.86 (dd, J = 13.4, 8.3 Hz, 1H), 1.63 (s, 3H), 1.58
(s, 3H), 1.54 (d, J = 2.7 Hz, 2H), 1.50-1.45 (m, 1H), 1.39-1.32 (m, 1H), 1.15-1.04 (m, 1H), 0.95
(t, J = 7.8 Hz, 9H), 0.88 (t, J = 7.3 Hz, 3H), 0.82 (d, J = 6.6 Hz, 3H), 0.54 (q, J = 7.8, 6H); 13C
NMR (100 MHz, CDCl3): δ = 126.8, 124.6, 42.3, 34.5, 30.2, 21.6, 21.1, 19.9, 19.6, 12.3, 8.0,
4.7; MS (EI) m/z (relative intensity, %) 254 (M+, 13), 225 (1), 197 (5), 183 (1), 169 (2), 155 (1),

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139 (1), 127 (1), 115 (100), 87 (65), 73 (2), 59 (16); HR-MS: calcd for C16H34Si(M) 254.2430,
found 254.2423.
General Procedure for the Preparation of Enynes
Vinyl bromide (1.0 M, 30 mL, 30 mmol) in THF was added to a solution 1-Alkynes (20 mmol),
PdCl2(PPh3)2 (280 mg, 0.4 mmol) and CuI (152 mg, 0.8 mmol) in Et3N (20 mL) at 25 °C. After
stirring for 3 h at 25 °C, 1 N HClaq was added to the solution. A saturated aqueous
NH4Cl solution (30 mL) was added, and the product was extracted with ether (30 mL).
The organic layer was dried over MgSO4, and concentrated under vacuum. Purification
by column chromatography with hexane afforded the corresponding enynes as an oil.
But-3-en-1-ynyl-triisopropyl-silane (21)
Vinyl bromide (1.0 M, 30 mL, 30 mmol) in THF was added to a solution
triisopropylsilylacetylene (3.8 g, 20 mmol), PdCl2(PPh3)2 (280.5 mg, 0.4 mmol) and CuI (152.3
mg, 0.8 mmol) in Et3N (20 mL) at 25 °C. After stirring for 3 h at 25 °C, 1 N HClaq was
added to the solution. A saturated aqueous NH4Cl solution (30 mL) was added, and the
product was extracted with ether (30 mL). The organic layer was dried over MgSO4,
and concentrated under vacuum. Purification by column chromatography with hexane
afforded 3.8 g (92%) of 21. 1H NMR (400 MHz, CDCl3): δ = 5.84 (dd, J = 11.2, 17.6 Hz, 1H),
5.68 (dd, J = 17.6, 2.4 Hz, 1 H), 5.49 (dd, J = 11.1, 2.4 Hz, 1H), 1.09-1.08 (m, 21H); 13C NMR
(100 MHz, CDCl3): δ = 127.6, 117.5, 105.7, 91.4, 18.6, 11.2; MS (EI) m/z (relative intensity,
%) 208 (M+, 12), 165 (100), 149 (1), 137 (39), 123 (30), 109 (52), 95 (55), 79 (8); HR-MS:
calcd for C13H24Si (M) 208.1647, found 208.1649; elemental analysis: calcd for C13H24Si: C,
74.92; H, 11.61. found: C, 75.14; H, 11.33
(5,5-Dimethyl-1-phenyl-hexa-1,2-dienyl)-triethyl-silane (14)
To a mixture of but-3-en-1-ynyl-benzene (128.2 mg, 1.0 mmol) and a catalytic amount
of Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added tert-BuMgCl (0.8 M, 1.9 mL, 1.5
mmol) in THF, and the mixture was stirred for 3 h at 25 °C. Then Et3SiCl (226.1 mg,
1.5 mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C, similar
workup as mentioned above afforded a pale yellow crude product (98 % NMR yield).
Purification by HPLC with CHCl3 as an eluent afforded 285.5 mg (95 %) of 14. IR
(neat): 3053, 2950, 2873, 1924, 1595, 1489, 1444, 1363, 1240, 1006, 756, 734, 704, 695 cm-1;
1H NMR (400 MHz, CDCl3): δ = 7.28-7.12 (m, 5H), 5.06 (t, J = 8.0 Hz, 1H), 2.00 (d, J = 8.0 Hz,
2H), 0.95 (t, J = 7.6 Hz, 9H), 0.93 (s, 9H), 0.73 (q, J = 7.6 Hz, 6H); 13C NMR (100 MHz,
CDCl3): δ = 209.8, 138.7, 128.1, 127.5, 125.6, 95.4, 83.0, 43.7, 31.2, 29.3, 7.6, 4.2; MS (EI) m/z

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(relative intensity, %) 300 (M+, 4), 272(17), 243(4), 215(5), 187(8), 159(5), 131(9), 115(100),
87(67), 59(18); HR-MS: calcd for C20H32Si(M) 300.2273, found 300.2271; elemental analysis:
calcd for C20H32Si: C, 79.92; H, 10.73. found: C, 80.03; H, 10.61
Triethyl-(5-methyl-1-phenyl-hexa-1,2-dienyl)-silane (15)
To a mixture of but-3-en-1-ynyl-benzene (128.2 mg, 1.0 mmol) and a catalytic amount
of Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added i-PrMgBr (0.6 M, 2.7 mL, 1.5
mmol) in THF, and the mixture was stirred for 3 h at 25 °C. Then Et3SiCl (226.1 mg,
1.5 mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C, similar
workup as mentioned above afforded a pale yellow crude product (83 % NMR yield).
Purification by HPLC with CHCl3 as an eluent afforded 226.4 mg (79 %) of 15. IR
(neat): 3436, 3058, 2956, 2874, 1925, 1706, 1597, 1490, 1465, 1380, 1239, 1005, 910, 827, 734,
696 cm-1; 1H NMR (400 MHz, CDCl3): δ = 7.27-7.14 (m, 5H), 5.06 (t, J = 7.6 Hz, 1H), 1.99 (td,
J = 7.1, 2.3 Hz, 2H), 1.74-1.64 (m, 1H), 0.95 (t, J = 7.8 Hz, 9H), 0.94 (d, J = 7.6 Hz, 6H), 0.72
13
(q, J = 7.9 Hz, 6H); C NMR (100 MHz, CDCl3): δ = 209.7, 138.8, 128.3, 127.6, 125.8, 96.0,
84.8, 38.0, 29.0, 22.4, 7.3, 4.1; MS (EI) m/z (relative intensity, %) 286 (M+, 1), 257 (46), 229
(4), 215 (1), 187 (12), 163 (20), 159 (11), 135 (5), 131 (17), 115 (100), 105 (5), 87 (98), 59
(27); HR-MS: calcd for C19H30Si(M) 286.2117, found 286.2108
4-Hexyl-8-methyl-nona-1,4,5-triene (17)
To a mixture of dec-1-en-3-yne (136.5 mg, 1.0 mmol) and a catalytic amount of
Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added i-PrMgBr (0.6 M, 2.7 mL, 1.5 mmol)
in THF, and the mixture was stirred for 3 h at 25 °C. Then allyl bromide (181.5 mg, 1.5
mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C, similar workup
as mentioned above afforded a pale yellow crude product (73 % NMR yield).
Purification by HPLC with CHCl3 as an eluent afforded 143.3 mg (65 %) of 17. IR
(neat): 3400, 3078, 2956, 2871, 1963, 1724, 1638, 1466, 1382, 1367, 1168, 991, 912, 835, 724
1
cm-1; H NMR (400 MHz, CDCl3): δ = 5.86-5.76 (m, 1H), 5.06-4.98 (m, 3H), 2.69 (d, J = 5.9
Hz, 2H), 1.94-1.84 (m, 4H), 1.68-1.58 (m, 1H), 1.40-1.28 (m, 8H), 0.93 (d, J = 14.6 Hz, 6H),
0.88 (t, J = 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3): δ = 201.8, 136.6, 115.3, 101.8, 90.4,
90.3, 39.0, 37.8, 32.2, 31.8, 29.0, 28.6, 27.6, 22.7, 14.1; MS (EI) m/z (relative intensity, %) 220
(M+, 1), 205 (1), 191 (1), 177 (28), 163 (6), 150 (25), 135 (29), 121 (19), 107 (80), 93 (93), 79
(100), 67 (29), 55 (20); HR-MS: calcd for C16H28 (M) 220.2191, found 220.2194

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(1-Allyl-5,5-dimethyl-hexa-1,2-dienyl)-trimethyl-silane (19)
To a mixture of but-3-en-1-ynyl-trimethyl-silane (124.3 mg, 1.0 mmol) and a catalytic
amount of Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added tert-BuMgCl (0.8 M, 1.9
mL, 1.5 mmol) in THF, and the mixture was stirred for 3 h at 25 °C. Then allyl bromide
(181.5 mg, 1.5 mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C,
similar workup as mentioned above afforded a pale yellow crude product (99 % NMR
yield). Purification by HPLC with CHCl3 as an eluent afforded 143.3 mg (98 %) of 19.
IR (neat): 4378, 3880, 3326, 2954, 2348, 1936, 1638, 1474, 1388, 1364, 1248, 992, 910, 838,
1
754, 628 cm-1; H NMR (400 MHz, CDCl3): δ = 5.80-5.71 (m, 1H), 4.97-4.87 (m, 2H),
13
4.73-4.69 (m, 1H), 2.65-2.63 (m, 2H), 1.88 (d, J = 7.8 Hz, 2H), 0.90 (s, 9H), 0.08 (s, 9H); C
NMR (100 MHz, CDCl3): δ = 207.3, 137.7, 114.7, 93.3, 82.5, 43.7, 34.5, 31.0, 29.3, -1.3; MS
(EI) m/z (relative intensity, %) 222 (M+, 1), 179 (1), 165 (20), 148 (1), 137 (2), 123 (2), 109 (3),
91 (1), 73 (100), 57 (8); HR-MS: calcd for C14H26Si(M) 222.1804, found 222.1799.
5-Methyl-3-tributylsilanyl-1-trimethylsilanyl-hept-1-yne (20)
To a mixture of but-3-en-1-ynyl-trimethyl-silane (124.3 mg, 1.0 mmol) and a catalytic
amount of Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added sec-BuMgCl (0.7 M, 2.1
mL, 1.5 mmol) in THF, and the mixture was stirred for 3 h at 25 °C. Then Bu3SiCl
(352.3 mg, 1.5 mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C,
similar workup as mentioned above afforded a pale yellow crude product (93 % NMR
yield). Purification by HPLC with CHCl3 as an eluent afforded 327.5 mg (86 %) of 20.
IR (neat): 4331, 3592, 2958, 2873, 2596, 2157, 1814, 1464, 1410, 1377, 1248, 1195, 1082, 1000,
1
964, 873, 841, 759, 733, 656 cm-1; H NMR (400 MHz, CDCl3): δ = 1.87-1.82 (m, 1H),
1.53-1.48 (m, 1H), 1.37-1.22 (m, 16H), 0.93-0.83 (m, 15H), 0.65-0.60 (m, 6H), 0.12 (s, 9H);
13C NMR (100 MHz, CDCl3): δ = 110.3, 83.7, 35.6, 33.3, 30.0, 26.5, 25.7, 17.7, 15.7, 15.1, 13.5,
10.8, -0.01; MS (EI) m/z (relative intensity, %) 380 (M+, 2), 323 (7), 310 (1), 267 (6), 254 (1),
245 (1), 211 (3), 199 (51), 183 (2), 166 (2), 143 (100), 127 (7), 109 (5), 87 (17), 73 (16), 59
(25); HR-MS: calcd for C23H48Si2(M) 380.3295, found 380.3290.
5,5-Dimethyl-3-triethylsilanyl-1-triisopropylsilanyl-hex-1-yne (22)
To a mixture of but-3-en-1-ynyl-triisopropyl-silane (208.4 mg, 1.0 mmol) and a catalytic
amount of Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added tert-BuMgCl (0.8 M, 1.9
mL, 1.5 mmol) in THF, and the mixture was stirred for 3 h at 25 °C. Then Et3SiCl
(226.1 mg, 1.5 mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C,
similar workup as mentioned above afforded a pale yellow crude product (74 % NMR
yield). Purification by HPLC with CHCl3 as an eluent afforded 258.9 mg (68 %) of 22.

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IR (neat): 4099, 3522, 2953, 2865, 2360, 2151, 1732, 1464, 1416, 1365, 1241, 1103, 1072, 1017,
919, 883, 766, 718, 675, 620 cm-1; 1H NMR (400 MHz, CDCl3): δ = 1.85 (d, J = 11.2 Hz, 1H),
1.46 (t, J = 11.2 Hz, 1H), 1.31 (d, J = 14.0 Hz, 1H), 1.05-0.96 (m, 39H), 0.73-0.61 (m, 6H); 13C
NMR (100 MHz, CDCl3): δ = 113.0, 79.5, 43.3, 32.5, 29.7, 18.6, 13.3, 11.5, 7.6, 2.3; MS (EI)
m/z (relative intensity, %) 380 (M+, 4), 351 (5), 337 (57), 323 (1), 309 (1), 295 (2), 267 (1), 253
(9), 239 (1), 225 (6), 211 (3), 197 (3), 183 (4), 157 (100), 129 (9), 115 (86), 101 (1), 87 (50), 73
(14); HR-MS: calcd for C23H48Si2(M) 380.3295, found 380.3289; elemental analysis: calcd for
C23H48Si2: C, 72.54; H, 12.71. found: C, 72.54; H, 12.71.
Triethyl-(1-ethyl-3,5,5-trimethyl-hexa-1,2-dienyl)-silane (24)
To a mixture of 2-methyl-1-hexen-3-yne (94.2 mg, 1.0 mmol) and a catalytic amount of
Li2CuCl4 (0.1 M, 0.1 mL, 0.01 mmol) was added tert-BuMgCl (0.8 M, 1.9 mL, 1.5
mmol) in THF, and the mixture was stirred for 3 h at 25 °C. Then Et3SiCl (226.1 mg,
1.5 mmol) was added to the solution at 0 °C. After stirring for 1 h at 25 °C, similar
workup as mentioned above afforded a pale yellow crude product (85 % NMR yield).
Purification by HPLC with CHCl3 as an eluent afforded 207.9 mg (78 %) of 24. IR
(neat): 2953, 2910, 2874, 1931, 1476, 1464, 1416, 1362, 1311, 1238, 1200, 1085, 1054, 1008,
973, 924, 733, 703 cm-1; 1H NMR (400 MHz, CDCl3): δ = 1.96-1.90 (m, 2H), 1.73 (s, 2H), 1.67
(s, 3H), 1.02 (t, J = 7.3 Hz, 3H), 0.94 (s, 9H), 0.93 (t, J = 7.8 Hz, 9H), 0.56 (t, J = 7.8 Hz, 6H);
13C NMR (100 MHz, CDCl3): δ = 206.8, 92.4, 91.3, 48.6, 31.2, 29.9, 23.5, 21.8, 14.1, 7.5, 3.3;
MS (EI) m/z (relative intensity, %) 266 (M+, 31), 237 (7), 209 (22), 181 (12), 151 (3), 139 (35),
115 (100), 87 (55), 59 (10), 41 (2); HR-MS: calcd for C17H34Si(M) 266.2430, found 266.2439;
elemental analysis: calcd for C17H34Si: C, 76.61; H, 12.86. found: C, 76.62; H, 13.13.