R. Wang, Z. Zeng, B. Twamley, M. M. Piekarski, J. M. Shreeve
FULL PAPER
1-(Pyrazolylmethyl)-3-(4,4,4-trifluorobutyl)imidazolium
Bis(tri-
7.71 (d, J = 1.8 Hz, 1 H, CH4,5-imidazolium), 7.70 (d, J = 1.7 Hz, 1
H, CH3,5-pyrazole), 7.50 (d, J = 1.5 Hz, 1 H, CH3,5-pyrazole), 6.54 (s,
fluoromethanesulfon)amide (3e): Pale-yellow liquid; yield: 0.50 g
1
(92%). H NMR: δ = 9.23 (s, 1 H, NCHN), 7.92 (d, J = 1.9 Hz, 1 2 H, NCH2N), 6.26 (t, J = 2.1 Hz, 1 H, CH4-pyrazole), 4.41 (t, J =
H, CH4,5-imidazolium), 7.75 (d, J = 1.1 Hz, 1 H, CH4,5-imidazolium),
7.1 Hz, 2 H, NCH2CH2), 2.13–2.28 (m, 4 H, CH2CH2CF3) ppm.
7.51 (s, 2 H, CH3,5-pyrazole), 6.58 (s, 2 H, NCH2N), 6.27 (t, J = 13C NMR: δ = 142.8, 137.3, 132.0, 127.9 (q, J = 273.8 Hz), 123.9,
2.1 Hz, 1 H, CH4-pyrazole), 4.44 (t, J = 6.7 Hz, 2 H, NCH2CH2), 123.2, 108.2, 63.0, 49.4, 30.8 (q, J = 29.1 Hz), 23.5 (q, J = 3.2 Hz)
2.13–2.30 (s, 4 H, CH2CH2CF3) ppm. 13C NMR: δ = 142.8, 137.4,
132.0, 127.9 (q, J = 273.8 Hz), 124.0, 123.2, 120.9 (q, J = 319.1 Hz),
108.2, 63.1, 49.5, 30.8 (q, J = 29.3 Hz), 23.5 (q, J = 3.2 Hz) ppm.
19F NMR: δ = –66.9 (t, J = 10.6 Hz, 3 F), –79.9 (s, 6 F) ppm.
C13H14F9N5O4S2 (539.03): calcd. C 28.95, H 2.62, N 12.98; found
C 29.15, H 2.13, N 12.78.
ppm. 19F NMR: δ = –66.8 (t, J = 10.6 Hz, 3 F), –70.8 to –73.3 (d,
J = 707.5 Hz, 6 F) ppm. C11H14F9N4P (404.08): calcd. C 32.69, H
3.49, N 13.86; found C 32.78, H 3.37, N 13.39.
3-Hexyl-1-(pyrazolylmethyl)imidazolium Hexafluorophosphate (3k):
Colorless solid; yield: 0.35 g (93%). 1H NMR: δ = 9.05 (s, 1 H,
NCHN), 7.92 (d, J = 2.4 Hz, 1 H, CH4,5-imidazolium), 7.67 (d, J =
2.2 Hz,
1 H, CH4,5-imidazolium), 7.62 (d, J = 1.8 Hz, 1 H,
3-Hexyl-1-(pyrazolylmethyl)imidazolium
Bis(trifluoromethanesul-
1
CH3,5-pyrazole), 7.49 (d, J = 1.6 Hz, 1 H, CH3,5-pyrazole), 6.51 (s, 2 H,
NCH2N), 6.26 (t, J = 2.1 Hz, 1 H, CH4-pyrazole), 4.25 (t, J = 7.4 Hz,
2 H, NCH2CH2), 1.82 (quint, J = 7.2 Hz, 2 H, NCH2CH2), 1.13–
1.25 (m, 6 H, CH2CH2CH2CH3), 0.73 (t, J = 7.0 Hz, 3 H,
CH2CH3) ppm. 13C NMR: δ = 142.8, 137.0, 132.0, 123.9, 122.9
108.2, 62.9, 50.8, 31.7, 30.4, 26.3, 22.9, 14.1 ppm. 19F NMR: δ =
–71.3 to –73.8 (d, J = 706.4 Hz, 6 F) ppm. C13H21F6N4P (378.14):
calcd. C 41.27, H 5.60, N 14.81; found C 41.53, H 5.46, N 14.71.
fon)amide (3f): Pale-yellow liquid; yield: 0.49 g (96%). H NMR: δ
= 9.20 (s, 1 H, NCHN), 8.02 (d, J = 2.4 Hz, 1 H, CH4,5-imidazolium),
7.78 (s, 1 H, CH4,5-imidazolium), 7.74 (s, 1 H, CH3,5-pyrazole), 7.61 (d,
J = 1.5 Hz, 1 H, CH3,5-pyrazole), 6.65 (s, 2 H, NCH2N), 6.37 (t, J =
1.8 Hz, 1 H, CH4-pyrazole), 4.35 (t, J = 7.3 Hz, 2 H, NCH2CH2),
1.93 (quint, J = 6.8 Hz, 2 H, NCH2CH2), 1.27–1.34 (m, 6 H,
CH2CH2CH2CH3), 0.85 (t, J = 6.7 Hz, 3 H, CH2CH3) ppm. 13C
NMR: δ = 142.1, 136.0, 131.1, 123.1, 122.1, 120.1 (q, J = 319.4 Hz),
107.4, 62.1, 50.0, 30.8, 29.7, 25.4, 22.0, 13.2 ppm. 19F NMR: δ =
–79.8 (s, 6 F) ppm. C15H21F6N5O4S2 (513.09): calcd. C 35.09, H
4.12, N 13.64; found C 35.10, H 4.09, N 13.43.
Synthesis Procedure for [3-Butyl-1-(pyrazolylmethyl)imidazol-2-ylid-
ene]palladium Dichloride (4): A mixture of 2d (0.48 g, 2.0 mmol)
and silver(I) oxide (0.24 g, 1.05 mmol) in dichloromethane (20 mL)
was stirred at 25 °C for 12 h. The reaction mixture was filtered
through Celite and washed with CH2Cl2 (3ϫ3 mL). The solvent
of the combined solutions was removed in vacuo until ca. 10 mL
remained. Then Pd(cod)Cl2 (0.57 g, 2 mmol) in 10 mL of CH2Cl2
was added to the resulting solution and the mixture stirred at 25 °C
for 12 h. After this time, it was filtered through Celite and washed
with CH2Cl2 (3 ϫ3 mL). The combined solutions were concen-
trated under reduced pressure to leave a yellow solid, which was
recrystallized from CH2Cl2/Et2O (3 mL/10 mL), washed with hex-
ane, and dried in vacuo to leave a yellow powder. Yield: 0.68 g
(89%). 1H NMR ([D6]DMSO): δ = 8.06 (d, J = 2.4 Hz, 1 H,
CH4,5-imidazol), 7.77 (d, J = 1.6 Hz, 1 H, CH4,5-imidazol), 7.44 (d, J =
1.5 Hz, 1 H, CH3,5-pyrazole), 7.33 (d, J = 1.5 Hz, 1 H, CH3,5-pyrazole),
6.51 (s, 2 H, NCH2N), 6.77 (t, J = 2.1 Hz, 1 H, CH4-pyrazole), 4.34
(t, J = 7.3 Hz, 2 H, NCH2CH2), 1.70 (quint, J = 7.0 Hz, 2 H,
NCH2CH2), 1.12 (sext, J = 7.1 Hz, 2 H, CH2CH3), 0.82 (t, J =
7.3 Hz, 3 H, CH2CH3) ppm. 13C NMR ([D6]DMSO): δ = 164.9,
143.8, 133.6, 122.5, 121.7, 107.1, 62.4, 49.4, 32.6, 19.0, 13.4 ppm.
C11H16Cl2N4Pd (379.98): calcd. C 34.62, H 4.23, N 14.68; found C
35.35, H 4.19, N 14.05.
3-(1H,1H,2H,2H-Perfluorohexyl)-1-(pyrazolylmethyl)imidazolium
Bis(trifluoromethanesulfon)amide (3g): Colorless solid; yield: 0.58 g
(86%). 1H NMR: δ = 9.42 (s, 1 H, NCHN), 8.03 (s, 1 H,
CH4,5-imidazolium), 7.94 (s, 1 H, CH4,5-imidazolium), 7.87 (s, 1 H,
CH3,5-pyrazole), 7.62 (s, 1 H, CH3,5-pyrazole), 6.70 (s, 2 H, NCH2N),
6.38 (t, J = 1.5 Hz, 1 H, CH4-pyrazole), 4.85 (t, J = 7.1 Hz, 2 H,
NCH2CH2), 3.03–3.15 (m, 2 H, NCH2CH2) ppm. 13C NMR: δ =
142.9, 141.6, 137.9, 132.0, 124.3, 123.3, 120.6 (q, J = 370.5 Hz),
110.1–124.2 (m), 108.3, 63.2, 43.2 (t, J = 5.1 Hz), 31.6 (t, J =
21.1 Hz) ppm. 19F NMR: δ = –79.9 (s, 6 F), –82.0 (t, J = 9.9 Hz,
3 F), –114.60 (quint, J = 7.8 Hz, 2 F), –125.0 (s, 2 F), –126.6 (quint,
J = 6.3 Hz, 2 F) ppm. C15H12F15N5O4S2 (675.01): calcd. C 26.67,
H 1.79, N 10.37; found C 26.70, H 1.80, N 10.72.
3-Methyl-1-(pyrazolylmethyl)imidazolium
Hexafluorophosphate
1
(3h): Colorless solid, yield: 0.37 g (84%). H NMR: δ = 9.09 (s, 1
H, NCHN); 8.02 (d, J = 2.3 Hz, 1 H, CH4,5-imidazolium), 7.76 (d, J
= 1.8 Hz, 1 H, CH4,5-imidazolium), 7.65 (d, J = 1.7 Hz, 1 H,
CH3,5-pyrazole), 7.60 (d, J = 1.6 Hz, 1 H, CH3,5-pyrazole), 6.63 (s, 2 H,
NCH2N), 6.37 (t, J = 2.1 Hz, 1 H, CH4-pyrazole), 4.04 (s, 3 H,
NCH3) ppm. 13C NMR: δ = 142.8, 137.6, 132.0, 125.2, 122.7,
108.2, 62.8, 36.8 ppm. 19F NMR: δ = –71.5 to –74.0 (d, J =
706.4 Hz, 6 F) ppm. C8H11F6N4P (308.16): calcd. C 31.18, H 3.60,
N 18.18; found C 31.70, H 3.57, N 18.11.
General Procedures for the Heck Cross-Coupling Reactions in Ionic
Liquid 3d: The palladium(II) complex 4 (7.6 mg, 0.02 mmol) was
dissolved in 3d (3.0 g), and the solvent was degassed under reduced
pressure at 60 °C for 1 h before nitrogen was introduced. The aryl
iodide (1.0 mmol), the olefin (1.25 mmol) and Na2CO3 (1.5 mmol)
were subsequently added under nitrogen. The resulting mixture was
stirred at 120 °C for 12 h. The product was extracted from the reac-
tion mixture by the addition of diethyl ether (3 mL), and followed
by decanting the diethyl ether solution of the product. This was
repeated three more times (3ϫ3 mL). The combined organic layers
were concentrated by rotary evaporation. The residue was purified
by flash chromatography on silica gel to give the desired product.
The ionic liquid containing the PdII catalyst was washed with water
(3ϫ3 mL), then dried under reduced pressure at 60 °C for 4 h to
remove traces of water and other volatile materials, and employed
for the next cycle.
3-Butyl-1-(pyrazolylmethyl)imidazolium Hexafluorophosphate (3i):
1
Pale-yellow liquid; yield: 0.32 g (91%). H NMR: δ = 9.17 (s, 1 H,
NCHN), 7.93 (d, J = 2.4 Hz, 1 H, CH4,5-imidazolium), 7.74 (d, J =
1.7 Hz,
1 H, CH4,5-imidazolium), 7.69 (d, J = 1.7 Hz, 1 H,
CH3,5-pyrazole), 7.51 (d, J = 1.5 Hz, 1 H, CH3,5-pyrazole), 6.57 (s, 2 H,
NCH2N), 6.27 (t, J = 2.1 Hz, 1 H, CH4-pyrazole), 4.30 (t, J = 7.3 Hz,
2 H, NCH2CH2), 1.82 (quint, J = 7.5 Hz, 2 H, NCH2CH2), 1.25
(sext, J = 7.5 Hz, 2 H, CH2CH3), 0.82 (t, J = 7.4 Hz, 3 H, CH2CH3)
ppm. 13C NMR: δ = 142.9, 137.2, 132.1, 124.1, 123.1, 108.2, 63.1,
50.7, 32.6, 20.0, 13.6 ppm. 19F NMR: δ = –71.4 to –73.9 (d, J =
706.4 Hz, 6 F) ppm. C11H17F6N4P (350.11): calcd. C 37.72, H 4.89,
N 16.00; found C 37.92, H 4.80, N 15.87.
1-(Pyrazolylmethyl)-3-(4,4,4-trifluorobutyl)imidazolium Hexafluoro-
phosphate (3j): Colorless solid; yield: 0.35 g (87%). H NMR: δ =
Supporting Information (see footnote on the first page of this arti-
cle): Spectroscopic data of coupled products for Heck cross-coup-
1
9.14 (s, 1 H, NCHN), 7.92 (d, J = 2.1 Hz, 1 H, CH4,5-imidazolium), ling reaction.
660
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Eur. J. Org. Chem. 2007, 655–661