Stille Cross-Coupling Reactions with Sn Reagents Supported on Ionic Liquids
tracted with CH2Cl2 (3ϫ20 mL), and the combined organic phase
was dried with MgSO4, filtered, and concentrated under reduced
pressure. The resulting crude product (1.78 g) was then purified by
column chromatography [silica gel: 20 g; solvent: CH2Cl2 to
CH2Cl2/MeOH (98:2) and then CH2Cl2/MeOH/diethyl ether
(96:2:2)] to yield the liquid product as a mixture of 7a with the
starting material 6a (1.70 g, 67% product, 33% starting material).
1-{6-[Dibutyl(phenyl)stannyl]hexyl}-3-methyl-1H-imidazolium Iodide
(8b):[9] In a dried sealed tube, crude 1-{3-[dibutyl(phenyl)stannyl]-
hexyl}-1H-imidazole (7b, 1.02 g, 2.2 mmol) was dissolved in methyl
iodide (0.5 mL) and stirred at 40 °C overnight. The mixture was
allowed to cool to room temp., and the excess methyl iodide was
evaporated under reduced pressure to yield 8b (1.33 g, 2.2 mmol,
1
99%) as a pale yellow oil. H NMR (CDCl3, 400 MHz): δ = 10.17
1
This mixture was used directly in the next reaction step. H NMR
(s, 1 H), 7.29–7.46 (m, 6 H), 7.20 (s, 1 H, 4-H), 4.25 (t, J = 7.5 Hz,
(CDCl3, 400 MHz): δ = 7.28–7.42 (m, 6 H), 7.04 (s, 1 H), 6.84 (s, 2 H), 4.11 (s, 3 H), 1.83–1.90 (m, 2 H), 0.98–1.57 (m, 20 H), 0.88
1 H), 3.86 (t, J = 7.2 Hz, 2 H), 1.01–2.00 (m, 16 H), 0.88 (t, J = (t, J = 7.2 Hz, 6 H) ppm. 13C NMR (CDCl3, 100 MHz): δ = 141.7,
7.3 Hz, 6 H) ppm. 13C NMR (CDCl3, 100 MHz): δ = 140.6, 137.1,
136.3, 129.3, 128.3, 128.2, 118.7, 50.6, 29.0, 28.7, 27.3, 13.6, 9.4,
136.8, 136.8, 136.4, 128.0, 123.6, 121.8, 50.1, 37.1, 33.5, 30.1, 29.0,
27.3, 26.5, 25.6, 13.6, 9.5, 9.4 ppm. 119Sn NMR (149 MHz, CDCl3):
5.8 ppm. IR (neat): ν = 2955, 2924, 2870, 2850, 1504, 1462, 1427,
δ = –43.8 ppm. IR (neat): ν = 3061, 2953, 2922, 2848, 1568, 1462,
˜
˜
1375, 1281, 1227, 1107, 1074, 906, 808, 725, 698, 662, 594, 503,
1427, 1375, 1165, 1072, 862, 727, 700, 656, 617, 505, 447 cm–1.
HRMS: calcd. for C24H41N2120Sn 477.2291; found 477.2296.
446 cm–1. HRMS: calcd. for C20H32N2Na120Sn [M
443.1485; found 443.1482.
+
Na]+
Dibutylbis(3-methoxyphenyl)stannane (11):
A solution of 3-
MeOC6H4MgBr in THF (1.2 molL–1, 24.00 mmol, 20 mL) was
added dropwise over a period of 30 min to a solution of Bu2SnCl2
(3.64 g, 12.00 mmol) in THF (9 mL). The solution was heated at
reflux for 18 h. The THF was evaporated under reduced pressure,
and the residue was dissolved in Et2O (20 mL). The organic layers
were washed with H2O (3ϫ10 mL). The aqueous layer was ex-
tracted with Et2O (3ϫ10 mL), and the combined organic phases
were dried with MgSO4, filtered, and concentrated under reduced
pressure to yield 11 (4.56 g, 86%). 1H NMR (400 MHz, CDCl3): δ
= 7.26–7.32 (m, 2 H), 6.99–7.12 (m, 4 H), 6.85–6.88 (m, 2 H), 3.80
(s, 6 H), 1.57–1.70 (m, 4 H), 1.26–1.40 (m, 8 H), 0.88 (t, J = 7.3 Hz,
6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 159.1, 141.7, 122.3,
113.5, 35.0, 28.9, 27.3, 13.6, 10.4 ppm. 119Sn NMR (149 MHz,
1-{3-[Dibutyl(phenyl)stannyl]propyl}-3-methyl-1H-imidazolium Iodide
(8a):[9] In a dried sealed tube, crude 1-{3-[dibutyl(phenyl)stannyl]-
propyl}-1H-imidazole (7a, 1.68 g) was dissolved in methyl iodide
(1 mL) and stirred at 40 °C overnight. The mixture was cooled to
room temp., and the excess methyl iodide was evaporated under
reduced pressure. A CH2Cl2/ethyl acetate/diethyl ether (90:5:5) mix-
ture was added, and the organic phase was washed with water to
remove the impurities having remained from the previous step and
then separated, dried with MgSO4, filtered, and concentrated under
reduced pressure to yield 8a (0.99 g, 1.8 mmol, 44%, over two
steps) as a colorless liquid. 1H NMR (CDCl3, 400 MHz): δ = 10.11
(s, 1 H), 7.33–7.44 (m, 5 H), 7.30 (m, 1 H), 7.04 (m, 1 H), 4.23 (t,
J = 7.2 Hz, 2 H), 4.09 (s, 3 H), 2.03–2.11 (m, 2 H), 1.11–1.57 (m,
14 H), 0.89 (t, J = 7.2 Hz, 6 H) ppm. 13C NMR (CDCl3, 100 MHz):
δ = 140.4, 136.8, 136.5, 128.5, 128.4, 123.7, 121.7, 53.3, 37.1, 29.0,
28.1, 27.3, 13.7, 9.5, 5.4 ppm. 119Sn NMR (149 MHz, CDCl3): δ =
CDCl ): δ = –69.6 ppm. IR (neat): ν = 2899, 1569, 1474, 1408,
˜
3
1282, 1241, 1223, 1180, 1100, 1039, 819, 773, 693, 655, 432 cm–1.
HRMS (CI methane): calcd. for C22H33O2Sn [M + H]+ 449.1503;
found 449.1495.
–42.2 ppm. IR (neat): ν = 3061, 2953, 2922, 2868, 2850, 1568, 1456,
˜
1425, 1375, 1167, 1072, 1020, 864, 727, 700, 656, 617, 594, 503,
447 cm–1. HRMS: calcd. for C21H35N2120Sn 435.1822; found
435.1825.
Dibutylchloro(3-methoxyphenyl)stannane (12): A solution of HCl in
Et2O (2 , 3 mL, 6 mmol) was added dropwise at 0–5 °C over 5 min
to a solution of dibutylbis(3-methoxyphenyl)stannane (11, 2.66 g,
5.94 mmol) in Et2O (25 mL). The mixture was stirred at room
temp. for an additional 1 h, and was then treated with H2O
(3ϫ20), and brine (10 mL). The aqueous layer was extracted with
Et2O (3ϫ20 mL), and the combined organic phases were dried
with MgSO4, filtered, concentrated under reduced pressure, and
distilled (125 °C, 0.04 Torr) to yield 12 as a yellow oil (1.78 g, 80%).
1H NMR (400 MHz, CDCl3): δ = 6.90–7.38 (m, 4 H), 3.83 (s, 3
H), 1.67–1.75 (m, 4 H), 1.49–1.57 (m, 4 H), 1.35–1.45 (m, 4 H),
0.92 (t, J = 7.3 Hz, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
159.6, 142.6, 129.7, 127.5, 120.8, 115.2, 55.2, 27.8, 26.8,
17.8,13.6 ppm. 119Sn NMR (149 MHz, CDCl3): δ = –70 ppm. IR
1-{6-[Dibutyl(phenyl)stannyl]hexyl}-1H-imidazole (7b):[9] Dibutyl-
phenyltin hydride (3.45 g, 11.1 mmol) was slowly added at –78 °C
to a solution of lithium diisopropylamide (11.3 mmol) in dry THF
(40 mL). The resulting mixture was stirred at –50 °C for 1 h and
was subsequently added at –50 °C to a solution of 1-(6-chlo-
rohexyl)-1H-imidazole (6b, 1.57 g, 8.5 mmol) in dry THF (20 mL).
The mixture was then allowed to warm to room temp. and stirred
for 18 h. Water (5 mL) was slowly added, and the mixture was
stirred at room temp. for an additional 15 min CH2Cl2 (100 mL)
was added to this mixture, and the organic phase was successively
washed with H2O (20 mL) and brine (10 mL). The aqueous layer
was extracted with CH2Cl2 (3ϫ20 mL), and the organic combined
phases were dried with MgSO4, filtered, and concentrated under
reduced pressure. The resulting crude product (4.69 g) was then
purified by column chromatography [silica gel; solvent: CH2Cl2 to
CH2Cl2/MeOH (98:2) and then CH2Cl2/MeOH/diethyl ether
(96:2:2)] to yield the pure product 7b as a colorless oil (2.86 g,
(neat): ν = 2955, 2853, 1734, 1583, 1571, 1475, 1462, 1411, 1376,
˜
1284, 1242, 1228, 1181, 1038, 866, 776, 692, 657, 511, 432 cm–1.
HRMS (CI methane): calcd. for C15H25OSn [M – Cl]+ 341.0927;
found 341.0929.
Dibutyl(3-methoxyphenyl)tin Hydride (13): A solution of NaBH4
(0.548 g, 14.50 mmol) in H2O (5 mL) was added dropwise with vig-
1
6.2 mmol, 73%). H NMR (CDCl3, 400 MHz): δ = 7.29–7.45 (m,
6 H), 7.05 (s, 1 H), 6.87 (s, 1 H), 3.87 (t, J = 7.2 Hz, 2 H), 1.68– orous stirring (Caution: hydrogen evolution!) at 0–8 °C over a
1.75 (m, 2 H), 1.64 (br. s, 2 H), 1.50–1.57 (m, 5 H), 1.27–1.37 (m,
period of 10 min to a solution of dibutylbis(3-methoxyphenyl)stan-
8 H), 0.89–1.07 (m, 5 H), 0.88 (t, J = 7.2 Hz, 6 H) ppm. 13C NMR nane (12, 1.81 g, 4.82 mmol) in Et2O (25 mL). The mixture was
(CDCl3, 100 MHz): δ = 141.8, 137.1, 136.5, 129.3, 128.1, 128.0, stirred at room temp. for an additional 45 min. The organic phase
118.8, 47.0, 33.7, 31.0, 29.1, 27.4, 26.6, 26.0, 13.7, 9.6, 9.5 ppm.
was then washed with H2O (2ϫ50 mL). The aqueous layer was
extracted with Et2O (3ϫ10 mL), and the combined organic phases
were dried with MgSO4, filtered, and concentrated under vacuum
to yield 13 as a yellow oil (1.41 g, 86%). 1H NMR (400 MHz,
CDCl3): δ = 6.84–7.29 (m, 5 H), 5.43 (m, 1 H), 1.14–1.63 (m, 12
119Sn NMR (149 MHz, CDCl ): δ = –43.9 ppm. IR (neat): ν =
˜
3
2955, 2922, 2850, 1504, 1462, 1427, 1282, 1228, 1074, 808, 725,
698, 662, 596, 503, 446 cm–1. HRMS: calcd. for C23H39N2120Sn
463.2135; found 463.2138.
Eur. J. Org. Chem. 2009, 3249–3257
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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