C. Yan et al. / Journal of Organometallic Chemistry 691 (2006) 3391–3396
3395
3.2. Procedure for the preparation of imidazolium-loaded
polymeric support (1)
reaction mixture was filtered, the polymeric support was
washed vigorously with ether (10 mL · 3), and then, the fil-
trate and the washing solution were combined. The solvents
were evaporated and the residue was purified by flash chro-
matography to give the corresponding alcohol.
Imidazolium-loaded polymeric support (1) was prepared
from commercially available CM PS resin cross-linked with
1% DVB (100–200 mesh). A mixture of CM PS resin (1.0 g,
2.3 mmol Cl/g polymeric support) and (2,4,6-trimethylphe-
nyl)imidazole (2.0 g, 10.7 mmol) in NMP (120 mL) was
slowly agitated at 80 ꢁC for 48 h. After cooling to room tem-
perature, the reaction mixture was filtered, andthe polymeric
support was washed with NMP (20 mL · 3), 0.1 N aq. HCl
(20 mL · 3), and methanol (20 mL · 3) followed by drying
under reduced pressure to give 1. The loading of the imidazo-
lium was determined to be 0.61 mmol/g by means of the
nitrogen content obtained from elementary analysis.
4-(Phenylmethoxyl)diphenylmethanol: white solid, mp:
1
56–57 ꢁC. H NMR (CDCl3, 400 MHz): d 7.44–7.25 (m,
12H, phenyl-CH), 6.96–6.93 (m, 2H, phenyl-CH), 5.81 (s,
1H, CHOH), 5.06 (s, 2H, OCH2), 2.20 (s, br, 1H, OH).
13C NMR (CDCl3, 100 MHz): d 158.2, 144.0, 136.9,
136.4, 128.5, 128.4, 127.9, 127.4, 127.3, 126.4, 114.8, 75.7,
70.0. HRMS (ESI): m/z calcd. for C20H18O2 [M+Na]+:
313.3515. Found 313.1199.
1,3-Benzodioxol-5-yl-40-methyldiphenylmethanol: white
solid, mp: 48–49 ꢁC. 1H NMR (CDCl3, 400 MHz): d
7.25–7.20 (m, 2H, phenyl-CH), 7.16–7.10 (m, 2H, phenyl-
CH), 6.83–6.80 (m, 2H, phenyl-CH), 6.79–6.73 (m, 1H,
phenyl-CH), 5.90 (m, 2H, OCH2O), 5.70 (s, 1H, CHOH),
2.32(s, 3H, CH3) 2.22 (s, br, 1H, OH). 13C NMR (CDCl3,
100 MHz) d 147.6, 146.7, 140.9, 138.2, 137.0, 129.0, 126.2,
119.8, 107.9, 107.1, 100.8, 75.6, 21.0. MS (ESI): m/z 265.1
[M+Na]+.
Other addition products, diphenylmethanol [11,39],
4-chlorodiphenylmethanol [39], 4-nitrodiphenylmethanol
[40], 4-cyanodiphenylmethanol [11,41], 1,3-benzodioxol-5-yl-
phenylmethanol [42], 4-chloro-40-methyldiphenylmethanol
[41], 4-methyl-40-nitrodiphenylmethanol [43], 4-cyano-40-
methyldiphenylmethanol [41], 4-chloro-40-methoxyldi-
phenylmethanol [44,45] have been identified by comparing
their 1H NMR spectra and melting points with that
reported in the literature.
3.3. Procedure for measuring the swelling volumes of the
imidazolium-loaded polymeric support (1)
The swelling volumes of the imidazolium-loaded poly-
meric support in various solvents were measured in a frit-
ted column (ID 1.0 cm, length 10 cm). The polymeric
support (1.0 g) was swollen in a solvent at room tempera-
ture for 4 h, and then washed with a 10-fold volume of each
solvent. After filtering out the solvent, the volume of the
polymeric support was measured.
3.4. Preparation of the polymer-supported NHC–Rh
complex (2)
[Rh(COD)Cl]2 (30 mg 0.12 mmol) was added to a
Schlenk tube along with 3 equivalents of KOtBu. The ves-
sel was evacuated and flushed with Ar three times. THF
(30 mL) was syringed in and stirred at room temperature
for 2 h before the imidazolium-loaded polymeric support
(1) (100 mg, 0.61 mmol/g) was added. The mixture was stir-
red at room temperature for 24 h. After filtration, the poly-
meric support was washed vigorously with THF
(10 mL · 5) and CH2Cl2 (10 mL · 5) to give 2. To measure
the amount of Rh loaded on the polymeric support, the
polymeric support (10 mg) was treated with a mixture
(5 mL) of hydrochloric acid and nitric acid (1:1, v/v) at
room temperature for 4 h. After the orange-colored solu-
tion was filtered, the polymeric support was washed with
distilled water (2.5 mL · 2), and then, the filtrate and the
washing solution were combined to determine the amount
of Rh by ICP-AES. The loading level of immobilized rho-
dium was measured to be 0.18 mmol/g.
4. Conclusion
In summary, a novel polymer-supported NHC–Rh com-
plex was prepared using a simple procedure. The polymer-
supported NHC–Rh complex showed high catalytic activ-
ity in the addition of arylboronic acids to aldehydes giving
diarylmethanols in satisfactory yields.
Acknowledgment
This work was financially supported by the National
Natural Science Foundation of PR China (Project No:
20372049).
Appendix A. Supplementary data
Supplementary data associated with this article can be
3.5. Rhodium-catalyzed addition of arylboronic acids to
aldehydes
Arylboronic acid (1 mmol), KOtBu (0.5 mmol), aldehyde
(0.5 mmol), catalyst (2) (Rh 5 lmol based on aldehyde) and
1,4-dioxane (5 mL) were introduced into a Schenk tube and
then water (1.25 mL) was added. The resulting mixture was
heated at 80 ꢁC. After cooling to room temperature, the
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