G. Liu et al. / Tetrahedron: Asymmetry 20 (2009) 240–246
245
ꢀ
1
importantly, such a catalyst could be recovered and reused five
times without obviously affecting the ee value, showing a good
application in industry. ICP analysis further confirmed the fact that
the content of Rh after fifth recycle was 5.39 mg per gram catalyst,
in which the lost Rh loading amounts could be neglected.
1070, 951, 816, 805, 747, 698, 596, 458 cm ; Elemental analysis
2
29
(%): C, 4.03; H, 1.28; N, 0.29; dpore: 3.65 nm; SBET: 285 m /g. Si
4
3
3
MAS/NMR (300 MHz): Q (d = ꢀ112 ppm), Q (d = ꢀ103 ppm), T
2
13
(d = ꢀ67 ppm), T (d = ꢀ58 ppm); C CP/MAS (161.9 MHz): 125,
3
1
49, 32, 12 ppm; P CP MAS NMR (161.9 MHz): 196.5 ppm.
4
.3. Characterization
3
. Conclusion
Ru and Rh loading amounts in the catalysts were analyzed using
In conclusion, we have presented a facile approach to prepare
an inductively coupled plasma optical emission spectrometer (ICP,
Varian VISTA-MPX). X-ray powder diffraction (XRD) experiments
were carried out on a Rigaku D/Max-RB diffractometer with Cu
mesoporous silica-supported chiral Rh and Ru catalysts 5 and 6
by directly anchoring the organometallic complexes onto SBA-15,
which exhibited high catalytic activities and moderate enantiose-
lectivities during the asymmetric hydrogenation of various aro-
matic ketones under 40 atm H . Both catalysts showed higher
2
activities and enantioselectivities than the corresponding homoge-
Ka radiation. Transmission electron microscopy (TEM) studies
were performed on a JEOL JEM2010 electron microscope, operated
at an acceleration voltage of 200 kV. Fourier transform infrared
(
FTIR) spectra were collected on a Nicolet Magna 550 spectrometer
neous catalysts. Furthermore, catalyst 5 could be recovered and re-
using KBr method. Nitrogen adsorption isotherms were measured
at 77 K after being outgassed at 423 K overnight on a Quanta-
chrome Nova 4000 analyzer. Pore size distributions and specific
surface areas (SBET) were calculated using BJH model and BET
used five times without affecting the ee value, showing
possibility in industrial applications.
a
4
4
. Experimental
1
13
31
method, respectively. Liquid-state H NMR, C NMR and
P
2
9
13
NMR, and Solid-state Si MAS NMR and C CP MAS NMR spectra
were recorded on a Bruker AV-400 spectrometer.
.1. Synthesis of 3
Under an argon atmosphere, to a stirred solution of 1 (0.50 g,
.43 mmol) and triethylamine (0.13 mL, 2.15 mmol) in 3 mL dry
4
.4. Catalytic reaction
1
toluene was added a solution of 2 (0.26 g, 1.45 mmol) in 3 mL
dry toluene at 0 °C. The resulting mixture was then allowed to
warm to room temperature slowly and was stirred for another
A typical procedure is as follows: Solid catalyst 5 (37.7 mg,
.00 lmol based on Rh from ICP) was added to a stainless-steel
autoclave at room temperature in glovebox, into which anhydrous
-propanol (5 mL, 0.065 mol), potassium isopropoxide (5 mL,
.065 mol), and ketone (0.4 mmol) were charged beforehand. The
2
3
h. After the solvent was removed in vacuo, the residue was
passed fast through a short column (silica gel, eluent: Et N/hex-
ane/CH Cl = 1:10:40) and concentrated in vacuo to afford 3 as
beige glass. Yield: 56%; ½
400 MHz, CDCl ): d 7.95–7.60 (m, 8H), 7.95–7.60 (t, J = 7.2 Hz,
H), 7.00–6.90 (t, J = 7.2 Hz, 2H), 3.59 (s, 9H), 2.62 (t, J = 5.4 Hz,
H), 2.08 (s, 1H, NH), 1.56–1.50 (m, 2H), 0.62 (t, J = 5.4 Hz, 2H);
2
0
3
2
2
2
D
0
1
hydrogenation was performed at 50 °C under 40 atm H2 for 16 h.
After completion of the reaction, hydrogen was carefully released.
aꢁ
¼ ꢀ548:6 (c 0.61, toluene); H NMR
(
3
2 2
Dry CH Cl (1 mL) was added, and the mixture was stirred for
2
2
1
min, after which the reactor contents were centrifuged (2000 r/
1
3
min) for 1–2 min. The solution was purified by column chromatog-
raphy (2 in. ꢂ 12 in. silica column) using ether as eluent. The main
fractions were concentrated to afford a mixture of the ketone and
the corresponding secondary alcohol as a colorless liquid to deter-
mine conversion and enantiomeric excess via a GC analysis using a
3
C NMR (126 MHz, CDCl ): d 6.9, 26.1, 43.3, 50.3, 113.6, 118.5,
1
3
9
23.5, 124.4, 127.1, 128.0, 129.2, 130.5, 134.1, 153.2; IR: 3399,
098, 2986, 2945, 1621, 1586, 1508, 1462, 1215, 1084, 1022,
ꢀ1
31
75, 821, 745 cm
;
3
P NMR (162 MHz, CDCl ): d 150.20; ESI-
HRMS, calcd for C26
5
H28NO PSi, 493.1573, found 493.1582.
Supelco b-Dex 120 chiral column (30 m ꢂ 0.25 mm (i.d.), 0.25
lm
film).
4
.2. Catalyst preparation
Acknowledgments
A typical procedure is as follows: Under an argon atmosphere,
to a stirred solution of 3 (0.208 g, 0.420 mmol) and (R,R)-DPEN
We are grateful to China National Natural Science Foundation
(20673072), Shanghai Sciences and Technologies Development
Fund (071005119, S30406, and 07dz22303), and Shanghai Munici-
pal Education Commission (08YZ71 and DZL807) for financial
supports.
(
(
0.045 g, 0.210 mmol) in 3 mL dry toluene was added [Rh(COD)Cl]
0.052 g, 0.104 mmol). The resulting mixture was stirred at room
2
temperature for 3 h. Then pure siliceous support [SBA-15 (pore size
of 7.6), 1.0 g] and dry toluene (25 mL) were added to the above
solution. The resulting mixture was stirred and refluxed for 24 h,
after which the residues were filtered and washed twice with dry
toluene. After Soxlet extraction in a toluene solvent to remove
homogeneous and unreacted starting materials, the solid was dried
under reduced pressure overnight to afford SBA-15/Rh-MonoPhos-
DPEN 5 (1.078 g, 29.2% relative to 3) as a light yellow powder. IR
References
1.
(a) Thomas, J. M.; Raja, R. Acc. Chem. Res. 2008, 41, 708; (b) Heitbaum, M.;
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Yang, Q. H. Chem. Commun. 2007, 547.
3
1
440, 3060, 2965, 2933, 2876, 1645, 1634, 1621, 1600, 1507,
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3. (a) Moller, K.; Bein, T.; Fischer, R. X. Chem. Mater. 1999, 11, 665; (b) Sims, S. D.;
Burkett, S. L.; Mann, S. Mater. Res. Soc. Symp. Proc. 1996, 431, 77; (c) Macquarrie,
D. J. Chem. Commun. 1996, 1961; (d) Babonneau, F.; Leite, L.; Fontlupt, S. J.
Mater. Chem. 1999, 9, 175; (e) Jiang, D. M.; Yang, Q. H.; Yang, J.; Zhang, L.; Zhu,
G. R.; Su, W. G.; Li, C. Chem. Mater. 2005, 17, 6154; (f) Jiang, D. M.; Gao, J. S.;
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ꢀ1
458, 1440, 1213, 1070, 955, 812, 804, 739, 694, 563, 457 cm
;
Elemental analysis (%): C, 4.29; H, 1.36; N, 0.30; dpore: 3.62 nm;
2
29
4
S
Q
BET: 204.5 m /g. Si MAS/NMR (300 MHz): Q (d = ꢀ111 ppm),
3
3
2
13
(d = ꢀ101 ppm), T (d = ꢀ66 ppm), T (d = ꢀ57 ppm); C CP/
31
MAS (161.9 MHz): 127, 49, 31, 12 ppm;
161.9 MHz): 193.3 ppm.
Catalyst 6: Prepared according to the general procedure de-
scribed above. Light red powder (Yield: 28.5%); IR 3400, 3100,
960, 2929, 2868, 1650, 1634, 1622, 1580, 1510, 1462, 1442,
P CP MAS NMR
(
4.
(a) Feringa, B. L. Acc. Chem. Res. 2000, 33, 346; (b) Pena, D.; Minnaard, A. J.; de
Vries, J. G.; Feringa, B. L. J. Am. Chem. Soc. 2002, 124, 14552; (c) Claver, C.;
Fernandez, E.; Gillon, A.; Heslop, K.; Hyett, D. J.; Martorelli, A.; Orpen, A. G.;
2