5
6
R. Liu et al. / Journal of Catalysis 307 (2013) 55–61
2
9
transfer hydrogenation. Moreover, this organoruthenium-func-
tionalized chrysanthemum-like mesoporous silica can serve as a
general catalyst to promote asymmetric transfer hydrogenation
for extensive substrates including various aryl ketones and quino-
lines in aqueous medium. In addition, this robust catalyst can be
readily recycled and reused at least 10 times without reducing
its catalytic efficiency, presenting a practical application in asym-
metric synthesis.
(m), 798.5 (m), 702.2 (w), 568.0 (w), 462.1 (m); Si MAS/NMR
3
2
3
(79.4 MHz):
À101.7 ppm), Q (d = À110.9 ppm);
8.3–20.8 (CH in C Me , SiCH and CH
and CH of CTAB), 52.8 (NCH and NCH
(NCHPh of T DPEN), 119.7–141.4, 148.7 (C of Ph and Ar) ppm; Ele-
mental analysis (%): C 11.72, H 2.15, N 1.01, S 0.76.
T
(d = À68.4 ppm),
Q
(d = À92.6 ppm),
Q
(d =
C CP/MAS (100.5 MHz):
of CTAB), 24.0–34.3 (CH Ph
of CTAB), 55.6–65.1
4
13
3
6
6
2
3
2
2
2
3
S
2.2.2. Preparation of ArRuTsDPEN-CMS (5)
In a typical synthesis, to a stirred suspension of 4 (1.0 g) and
2
. Experimental
NEt
Me
room temperature for 24 h. Then, the residues were filtrated and
washed twice with 20 mL of dry CH Cl . After Soxhlet extraction
in dry CH Cl to remove unreacted start materials, the solid was
dried under reduced pressure overnight to afford the catalyst 5
1.02 g) as a light yellow powder. ICP analysis showed that the
3
2 2 2
(1.00 mL, 16.5 mmol) in 20 mL dry CH Cl was added [RuCl (-
C
6
6
2
)] (0.11 g, 0.16 mmol). The resulting mixture was stirred at
2.1. Characterization
2
2
Ru loading amount in the catalyst was analyzed using an induc-
2
2
tively coupled plasma optical emission spectrometer (ICP, Varian
VISTA-MPX). Fourier transform infrared (FTIR) spectra were col-
lected on a Nicolet Magna 550 spectrometer using KBr method.
X-ray powder diffraction (XRD) was carried out on a Rigaku D/
(
Ru loading amount was 27.12 mg (0.266 mmol) per gram catalyst.
IR (KBr) cm-1: 3424.4 (s), 2928.4 (w), 2855.6 (w), 1630.1 (m),
498.3 (w), 1457.9 (w), 1384.0 (w), 1082.1 (s), 953.1 (m), 801.2
Max-RB diffractometer with Cu K
microscopy (SEM) images were obtained using a JEOL JSM-
380LV microscope operating at 20 kV. Transmission electron
a radiation. Scanning electron
1
(
0
(
2
m), 699.6 (w), 565.2 (w), 462.2 (m); SBET: 578.3 m /g, Vpore
:
6
3
29
Si MAS/NMR (79.4 MHz): T3
.74 cm /g,
pore
d : 3.73 nm;
microscopy (TEM) images were performed on a JEOL JEM2010 elec-
tron microscope at an acceleration voltage of 220 kV. X-ray photo-
electron spectroscopy (XPS) measurements were performed on a
2
3
4
d = À67.8 ppm),
d = À111.0 ppm);
Me , SiCH and CH
CTAB), 52.8 (NCH
DPEN), 89.8 (C
Q
(d = À92.5 ppm),
Q
(d = À101.8 ppm),
Q
1
3
(
C CP/MAS (100.5 MHz): 8.8–21.4 (CH
3
in
of
C
6
6
2
3
2 2
of CTAB), 24.0–33.4 (CH Ph and CH
and NCH of CTAB), 55.6–64.3 (NCHPh of TS-
3
PerkinElmer PHI 5000C ESCA system. A 200
was scanned using a monochromatized Aluminum K
1486.6.6 eV) at 40 W and 15 kV with 58.7 eV pass energies. All the
binding energies were calibrated by using the contaminant carbon
1s = 284.6 eV) as a reference. Nitrogen adsorption isotherms were
l
m diameter spot size
2
a
X-ray source
6
of C
6
Me
6
), 121.3–141.9, 149.5 (C of Ph and Ar)
(
ppm; Elemental analysis (%): C 16.54, H 2.86, N 1.10, S 0.86.
(
C
measured at 77 K with a Quantachrome Nova 4000 analyzer. The
samples were measured after being outgassed at 423 K overnight.
Pore size distributions were calculated by using the BJH model. The
specific surface areas (SBET) of samples were determined from the
2.3. General procedure for asymmetric transfer hydrogenation
For asymmetric transfer hydrogenation of ketones, the catalyst
5 (15.0 mg, 4.0 lmol of Ru based on the ICP analysis), HCO Na
2
linear parts of BET plots (p/p
0
= 0.05–1.00). Thermal gravimetric
(0.27 g, 10.0 mmol), ketone (0.40 mmol), and 2.0 mL of water were
added in a 10 mL round bottom flask in turn. The mixture was al-
lowed to react at 40 °C for 3.0–9.0 h. [For asymmetric transfer
analysis (TGA) was performed with a PerkinElmer Pyris Diamond
TG analyzer under air atmosphere with a heating ramp of 5 K/
min. Solid-state NMR experiments were explored on a Bruker
AVANCE spectrometer at a magnetic field strength of 9.4 T with
hydrogenation of quinolines, the catalyst 5 (15.0 mg, 4.0
lmol of
Ru based on the ICP analysis), HCO Na (0.27 g, 10.0 mmol), quino-
2
1
H frequency of 400.1 MHz, 13C frequency of 100.5 MHz, and Si
29
lines (0.40 mmol), and 2.0 mL (2.0 M HCOOH/HCOONa buffer solu-
tion, pH = 5.0) were added in a 10 mL round bottom flask in turn.
The mixture was allowed to react at 40 °C for 10.0–24 h.] During
that time, the reaction was monitored constantly by TLC. After
completion of the reaction, the catalyst was separated via centri-
fuge (10,000 r/min) for the recycle experiment. The aqueous solu-
frequency of 79.4 MHz with 4 mm rotor at two spinning frequency
of 5.5 kHz and 8.0 kHz, TPPM decoupling is applied in the during
1
acquisition period. H cross-polarization in all solid-state NMR
experiments was employed using a contact time of 2 ms and the
pulse lengths of 4
ls. Elemental analysis was performed with a
Carlo Erba 1106 Elemental Analyzer.
tion was extracted by Et
washed with brine twice and dehydrated with Na
evaporation of Et O, the residue was purified by silica gel flash col-
umn chromatography to afford the desired product. The conver-
sion could be determined by an external standard method, and
the ee value could be determined by chiral GC using a Supelco b-
2
O (3 Â 3.0 mL). The combined Et
2
O was
SO . After the
2
4
2
2
2
1
.2. Catalyst preparation
.2.1. Preparation of TsDPEN-functionalized CMS (4)
In a typical synthesis, 8.0 mL H
.0 mL ammonia solution (25–28%) were added in a closed vessel
2
O, 40.0 mL ethyl ether, and
Dex 120 chiral column (30 m  0.25 mm (i.d.), 0.25
HPLC analysis with a UV–Vis detector using a Daicel OJ-H/OD-H/
OB-H chiralcel column (
0.46 Â 25 cm).
lm film) or a
and vigorously stirred at ambient temperature. When the solution
became homogeneous, 2.0 mL (8.06 mmol) TEOS was dropwise
added and stirred continuously for 3 h. Then to this, solution was
added 1.0 g CTAB (2.74 mmol) and a mixture solution of TEOS
U
3. Results and discussions
(
1
2.0 mL, 8.06 mmol) and (R,R)-TsDPEN-derived silica (3) (0.80 g,
.60 mmol). The resulting mixture was vigorously stirred for 12 h
3.1. Syntheses and characterizations of the catalysts
at ambient temperature. The products were collected by centrifu-
gating, washing repeatedly for three times with distilled water.
The surfactant was then extracted by refluxing with HCl–ethanol
The incorporation of chiral ArRuTsDPEN functionality within
its CMS silicate network, abbreviated as ArRuTsDPEN-CMS (5),
was prepared as outlined in Scheme 1. Firstly, a microemulsion
2 2
solution for 12.0 h. After Soxhlet extraction in dry CH Cl to re-
move unreacted start materials, the solid was dried under reduced
(2) was formed in a mixture solvents of NH
3
ÁH
2
O, ethyl ether,
pressure overnight to afford TsDPEN-functionalized CMS (4)
and tetraethoxysilane (TEOS 1) to provide the growing silica
seeds. The cooperative assembly and continuous grown between
TEOS and 4-(trimethoxysilyl)ethyl)phenylsulfonyl-1,2-diphenyl-
À1
(
1.22 g) as a white powder. IR (KBr) cm : 3449.2 (s), 2928.8 (w),
2
856.7 (w), 1632.1 (m), 1496.5 (w), 1457.9 (w), 1082.2 (s), 955.3