Supported Amino Acid Ionic Liquids
A R T I C L E S
D
2
O): δ 3.82 (s, 3H), 5.28 (s, 2H), 5.30 (d, J ) 11.2 Hz, 1H), 5.79 (d,
of 4b (%): C, 80.50; H, 7.60; N, 4.57. The loading of l-proline on the
J ) 18 Hz, 1H), 6.66-6.73 (m, 1H), 7.31 (d, J ) 8.4 Hz, 2H), 7.38
resin: 0.44 mmol/g.
(
(
1
d, J ) 0.8 Hz, 2H), 7.45 (d, J ) 8.0 Hz, 2H) 8.72 (s, 1H). 13C NMR
75 MHz, D O): δ 35.8, 52.5, 115.4, 122.2, 123.9, 126.9, 129.0, 133.1,
Metal Salt Scavenging Experiment. CuI scavenging. A mixture
of 4a-2 (100 mg, 0.069 mmol of the L-proline unit), CuI (6.6 mg, 0.035
mmol, 0.5 equiv), and DMSO (2 mL) was stirred overnight under N
2
+
+
15
35.8, 138.2. MS (ESI ) m/z 199 [M-Cl] . Anal. Calcd for C13H -
2
2
ClN : C, 66.52; H, 6.44; N, 11.93. Found: C, 66.38; H, 6.46; N, 11.90.
at room temperature, and an obvious color change of the resin from
pale yellow to red was observed. The ICP-AES analysis of the
supernatant indicated that the content of copper was 32.81 ppm,
demonstrating more than 97% of CuI was soaked on the resin 4a-2
and the loading level of CuI was ca. 0.34 mmol/g. Other CuI-soaked
4a-2 materials with different CuI loadings were prepared according
to the same procedure, and their CuI loading levels are shown in
Figure 3.
General Procedure for the Polymerization. A mixture of 1, styrene,
1
,4-divinylbenzene (DVB), azobisisobutyronitrile (AIBN), and poly-
vinylpyrrolidone (PVP) as a dispersant was stirred in ethanol for 24 h
at 65 °C under a nitrogen atmosphere. The resulting resin was filtered
and washed with distilled water, ethanol, and dichloromethane. The
resulting white polymer was dried in Vacuo for 24 h and then was
analyzed by elemental analysis to quantify the amount of imidazolium
groups by measuring the nitrogen content. This loading level could be
adjusted by changing the amount of ionic liquid monomer 1. In this
work, four polymers with different loadings of the imidazolium group
were used as shown in Table 1.
Pd(OAc)
the L-proline unit), Pd(OAc)
2
Scavenging. A mixture of 4a-2 (100 mg, 0.069 mmol of
(1.9 mg, 0.0086 mmol, 0.125 equiv), and
2
DMF (1 mL) was stirred overnight at room temperature, and the
supernatant became colorless. The ICP-AES analysis of the supernatant
showed that the content of Pd was 3.22 ppm, demonstrating more
Poly[1,2-dimethylimidazoliummethyl styrene chloride]-co-PS Resin
2+
(PS[DMVBIM][Cl], 2a-1). The ionic liquid monomer 1a (9.9 g, 39.8
than 99% of Pd(OAc)
level of Pd(OAc) was ca. 0.085 mmol/g. Other Pd(OAc)
a-2 materials with different Pd loadings were prepared according to
2
was soaked on the resin 4a-2, and the loading
mmol), styrene (6.3 g, 60.6 mmol), divinylbenzene (3.6 g, 27.7 mmol),
PVP (1.1 g), and AIBN (173 mg, 1.1 mmol) were used in EtOH (88
mL). Elemental analysis (%): C, 78.02; H, 7.43; N, 5.48. The loading
of the imidazolium on the resin: 1.96 mmol/g.
2
2
-soaked
4
the same procedure, and their Pd(OAc)
Figure 3.
2
loading levels are shown in
Poly[1,2-dimethylimidazoliummethyl styrene chloride]-co-PS Resin
PS[DMVBIM][Cl], 2a-2). The ionic liquid monomer 1a (9.9 g, 39.8
mmol), stryene (12.4 g, 119.2 mmol), divinylbenzene (7.2 g, 55.4
mmol), PVP (1.6 g), and AIBN (265 mg, 1.6 mmol) were used in EtOH
135 mL). Elemental analysis (%): C, 80.81; H, 7.53; N, 3.79. The
IrCl
L-proline unit), IrCl
1 mL) was stirred overnight at room temperature, and the supernatant
3
Scavenging. A mixture of 4a-2 (100 mg, 0.069 mmol of the
(
3
(2.6 mg, 0.0086 mmol, 0.125 equiv), and DMF
(
became colorless. The ICP-AES analysis of the supernatant showed
(
3+
that the content of Ir was 16.3 ppm, demonstrating more than 99%
loading of the imidazolium on the resin: 1.35 mmol/g.
of IrCl
3 3
was soaked on the resin 4a-2, and the loading level of IrCl
Poly[1,2-dimethylimidazoliummethyl styrene chloride]-co-PS Resin
was ca. 0.085 mmol/g.
(
PS[DMVBIM][Cl], 2a-3). The ionic liquid monomer 1a (9.9 g, 39.8
General Procedure for the Catalytic N-Arylation of Nitrogen-
Containing Heterocycles with Aryl and Heteroaryl Halides. A flame-
dried Schlenk test tube with a magnetic stirring bar was charged with
CuI (9.5 mg, 0.05 mmol), 4a-2 (145 mg, 0.1 mmol of the L-proline
mmol), stryene (53.6 g, 515.4 mmol), divinylbenzene (30.6 g, 235.4
mmol), PVP (6.7 g), and AIBN (1.12 g, 6.8 mmol) were used in EtOH
(572 mL). Elemental analysis (%): C, 89.49; H, 7.39; N, 0.89. The
loading of the imidazolium on the resin: 0.32 mmol/g.
unit), K
mmol), aryl or heteroaryl halide (0.6 mmol), and DMSO (2 mL) under
. A rubber septum was replaced with a glass stopper, and the system
was then evacuated three times and backfilled with N . The reaction
mixture was stirred for 30 min at room temperature and then heated at
20 °C for 60 h. The resulting mixture was cooled to ambient
2 3
CO (165 mg, 1.2 mmol), nitrogen-containing heterocycle (0.5
Poly[1-methylimidazoliummethyl styrene chloride]-co-PS Resin
(PS[MVBIM][Cl], 2b). The ionic liquid monomer 1b (9.6 g, 40.9
N
2
mmol), stryene (12.4 g, 119.2 mmol), divinylbenzene (7.2 g, 55.4
mmol), PVP (1.6 g), and AIBN (265 mg, 1.6 mmol) were used in EtOH
2
(135 mL). Elemental analysis (%): C, 81.97; H, 7.17; N, 4.10. The
1
loading of the imidazolium on the resin: 1.46 mmol/g.
temperature, diluted with 2-3 mL of ethyl acetate, filtered through
a plug of silica gel, and washed with 10-20 mL of ethyl acetate.
The filtrate was concentrated, and the resulting residue was purified
by column chromatography on silica gel to provide the desired
product.
General Procedure for the Preparation of 4a,b. The polymer 2
(
10.0 g) was stirred in aqueous NaOH (1 M, 100 equiv based on the
imidazolium group) for 40 h at room temperature. The resulting polymer
was separated and washed with distilled water, followed by a stirring
3
in an aqueous solution of L-proline (1 M, 100 equiv based on the
imidazolium group) for 40 h at room temperature. The solid was
separated and washed with distilled water and then dried in Vacuo for
Recycling Experiments. These experiments were performed ac-
cording to the representative procedure described above. The organic
solvent was filtrated after every run, and the resulting residue was
extracted with degassed ethyl acetate, washed with degassed water,
and then dried in Vacuo. The recycled catalyst was used directly for
2
4 h. The polymer was analyzed by an elemental analyzer to quantify
the amount of the L-proline unit by measuring the nitrogen content 2
and 4 as shown in Table 1.
2 3
the next cycle after the addition of 2.4 equiv of K CO .
Poly[1,2-dimethylimidazoliummethyl styrene L-proline salt]-co-
PS Resin (PS[DMVBIM][Pro], 4a-1). A pale yellow solid. Elemental
analysis of 4a-1 (%): C, 75.08; H, 7.64; N, 6.98. The loading of
L-proline on the resin: 1.55 mmol/g.
General Procedure for Solvent-Free Hydrogenation of Styrene.
A mixture of 4a-2 (100 mg, 0.069 mmol of the L-proline unit), Pd-
OAc) (15.5 mg, 0.069 mmol), and DMF (8 mL) was stirred overnight
2
(
at room temperature. The ICP-AES analysis of the supernatant showed
Poly[1,2-dimethylimidazoliummethyl styrene L-proline salt]-co-
PS Resin (PS[DMVBIM][Pro], 4a-2). A pale yellow solid. Elemental
analysis of 4a-2 (%): C, 79.00; H, 7.66; N, 4.55. The loading of
L-proline on the resin: 0.69 mmol/g.
2+
that the content of Pd was 218.43 ppm, demonstrating the loading
level of Pd(OAc)
separated and washed with DMF, followed by hydrogenation in 4 mL
of water under H (1 atm) overnight at room temperature. The resulting
2
was ca. 0.53 mmol/g. The resulting solid was
2
Poly[1,2-dimethylimidazoliummethyl styrene L-proline salt]-co-
PS Resin (PS[DMVBIM][Pro], 4a-3). A pale yellow solid. Elemental
analysis of 4a-3 (%): C, 88.38; H, 7.98; N, 1.08. The loading of
L-proline on the resin: 0.14 mmol/g.
black solid was filtrated and washed with water and dried in Vacuo. A
Schlenk test tube with a magnetic stirring bar was then charged with
the black solid (2.2 mg, 0.0012 mmol of Pd) and styrene (0.641 g, 6.2
mmol). The mixture was stirred for 20 h under H (1 atm) at room
2
temperature to afford the hydrogenated product (GC analysis: >99%
yield).
Poly[1-methylimidazoliummethyl styrene L-proline salt]-co-PS
Resin (PS[MVBIM][Pro], 4b). A pale yellow solid. Elemental analysis
J. AM. CHEM. SOC.
9
VOL. 129, NO. 45, 2007 13885