C-3 alkylation of oxindole with alcohols catalyzed by an indene-functionalized mesoporous iridium catalyst

Article abstract of DOI:10.1016/j.catcom.2010.12.021

A heterogeneous indene-based iridium catalyst with a highly ordered dimensional-hexagonal mesostructure was prepared through complexation of IrCl₃ with the indene-functionalized SBA-15 silica materials. During C-3 alkylation of oxindole with va

Full text of DOI:10.1016/j.catcom.2010.12.021

Catalysis Communications 12 (2011) 655–659
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Catalysis Communications
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Short Communication
C-3 alkylation of oxindole with alcohols catalyzed by an indene-functionalized
mesoporous iridium catalyst
⁎
⁎
Guohua Liu , Tianzeng Huang, Yuli Zhang, Xiaohui Liang, Yunsheng Li, Hexing Li
The Key Laboratory of Resource Chemistry of Ministry of Education, Shanghai Normal University, Shanghai 200234, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 24 October 2010
Received in revised form 11 December 2010
Accepted 13 December 2010
Available online 21 December 2010
A heterogeneous indene-based iridium catalyst with a highly ordered dimensional-hexagonal mesostructure
was prepared through complexation of IrCl3 with the indene-functionalized SBA-15 silica materials. During
C-3 alkylation of oxindole with various alcohols, this heterogeneous catalyst exhibited highly catalytic
activity (up to 93%). Such a catalyst could be recovered easily and used repetitively eight times without
significantly affecting its catalytic activity.
© 2010 Elsevier B.V. All rights reserved.
Keywords:
Heterogeneous catalyst
Iridium
Alkylation
Mesoporous materials
1. Introduction
expensive metal catalysts, as well as product contamination from
catalysts during work-up stage. Thus, besides employing economic
Oxindole as an important motif of many natural products has a
wide variety of biological activity [1–6]. In particular, oxindole
derivatives with C-3 functionalization, such as the anti-inflammatory
Tenidap [7] and the anti-cancer kinase inhibitor Sunitinib [8], are well
known for treatment of disease in medicinal chemistry. Generally,
main strategies to synthesize these biologically active molecules
involve conventional alkylation with alkyl halides. However, the in-
herent disadvantages of alkyl halides, such as toxicity and expensive-
ness, limit their application in industrial process. Furthermore,
alkylations with alkyl halides often suffer from bad regioselectivity
due to formation of bis-alkylated by-products [9]. Alcohols as a kind
of alkylative reagents are desirable economic and environmentally
friendly because only water is by-product. More importantly, alcohols
as relatively weak alkylative reagents possess high regioselectivity.
Recently, the catalytic reactions using alcohols as alkylative reagents
for C-3 alkylation of oxindole have appeared in the literature [10–16].
Grigg group [10] reported a catalytic reaction employing alcohols
as alkylative reagents, in which organometallic iridium showed a
high catalytic activity in C-3 alkylation of oxindole. A similar strategy
reported by Madsen group [11] also showed a high catalytic efficiency
for C-3 alkylation of oxindole when RuCl3 worked as a catalyst.
Although these catalysts had showed a high catalytic activity in C-3
alkylation of oxindole, their practical applications in the industrial
process were hindered due to difficulty in recovery and reuse of these
and environmentally friendly alcohols as alkylative reagents, giving
consideration to catalyst recycling for C-3 alkylation of oxindole is a
promising way in the industry.
Immobilization is well-known to solve the problem of transition-
metal catalyst recycling [17,18]. In particular, the immobilization of
homogeneous catalysts onto the mesoporous materials has showed
some salient features [19–22]. Besides general features of easy
separation and efficient recycling, these heterogeneous mesoporous
catalysts possess relatively large surface area and pore volume, and
tunable pore dimension and well-defined pore arrangement [23–25].
These features are not only beneficial to control the dispensability of
catalytically active species, but also to adjust the catalytic microen-
vironment of catalytically active centers. Furthermore, they also have
a facile preparation, remarkable thermal and mechanical stability.
Recently, we have reported a series of mesoporous catalysts and their
applications in catalytic processes [26–28]. Especially, microwave-
assisted Ti-catalyzed allylation of aldehydes [26] and microwave-
assisted tandem Ti/Ru-catalyzed allylation–isomerization reaction [27]
of benzaldehyde have showed a highly catalytic activity. Herein, we
develop a facile preparation of indene-functionalized mesoporous
iridium catalyst 5 and apply it to C-3 alkylation of oxindole with various
alcohols. The key feature is that an indene-functionalized mesoporous
material is prepared by a co-condensation method, which the potential
coordination-multifunctionilty of indenyl group to various transit
metals may result in an extensively application in catalytic reaction.
This research focuses on construction of highly ordered indene-
functionalized mesoporous iridium catalyst and investigation of its
catalytic performance in C-3 alkylation of oxindole.
⁎
Corresponding authors. Tel.: +86 21 64321819; fax: +86 21 64322511.
E-mail address: ghliu@shnu.edu.cn (G. Liu).
1566-7367/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.catcom.2010.12.021

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G. Liu et al. / Catalysis Communications 12 (2011) 655–659
Scheme 1. Preparation of the indene-functionalized mesoporous iridium catalyst 5.
2. Experimental
for 24 h and aged at 100 °C for 24 h. The resulting solid was filtered
and rinsed with excess ethanol before being dried overnight on a
filter. The surfactant template was removed by refluxing in acidic
ethanol (400 mL per gram) for 24 h. The solid was filtered and rinsed
with ethanol again, and dried at 60 °C under reduced pressure over-
night to afford In-SBA-15 (3) (1.02 g) in the form of a white powder.
IR (KBr) cm−1: 3440 (s), 2981 (w), 2879 (w), 1643 (m), 1544 (w),
1459 (w), 1400 (w), 1081 (s), 960 (w), 795 (w), 557 (w), 464 (m);
2.1. Synthesis of 2
Under argon atmosphere, to a stirred solution of indene (1.0 mL,
1.00 g, 15.15 mmol) in dry THF (20 mL) was added n-BuLi (6.50 mL,
16.25 mmol, 2.50 M in hexane) at −60 °C. The resulting mixture
was then allowed to warm to room temperature slowly and stirred
for another 1 h. After cooling down to 0 °C, a solution of 1 (3.64 g,
15.15 mmol) in 3 mL dry THF was added dropwise over 15 min. The
mixture was then warmed up to room temperature and stirred for
further 3 h. After the solvent was removed in vacuo, saturated NH4Cl
was added to quench the reaction. The reaction mixture then was
extracted with ethyl acetate several times. The combined organic
layer was washed subsequently with water and brine, and dried over
anhydrous Na2SO4. Evaporation of solvent gave the crude product,
which was fast passed through a short column (silica gel, eluent:
Et3N/ethyl acetate/petroleum ether=1:10:500) and concentrated in
vacuo to afford 2 (3.79 g, 11.85 mmol) as beige glass. Yield: 78.2%;
IR (KBr) cm−1: 3068 (w), 2975 (s), 2923 (s), 2885 (s), 1607 (w),
1483 (m), 1457 (m), 1441 (m), 1394 (m), 1270 (w), 1167 (m), 1104
(s), 1078 (s), 955 (s), 788 (s), 767 (s), 720 (m), 690 (w), 648 (w), 549
(w), 482 (w), 422 (w); 1H NMR (400 MHz, CDCl3): δ 7.55–7.28
(m, 4H), 6.30 (s, 1H), 3.94–3.89 (q, J=6.8 Hz, 6H), 3.41 (s, 2H), 2.70–
2.67 (t, J=5.4 Hz, 2H), 1.94–1.90 (m, J=5.4 Hz, 2H), 1.39–1.25
(t, J=6.8 Hz, 9H), 0.87–0.83 (t, J=5.4 Hz, 2H); 13C NMR (126 MHz,
CDCl3): δ 13.5, 17.0, 26.2, 33.0, 54.2, 73.0, 124.4, 127.1, 128.0, 129.2,
130.5, 134.1, 141; HPLC-MS (100 eV) m/z (%): Anal. Calcd. for
Elemental analysis (%): C 15.47, H 3.09; dpore: 5.453 nm; SBET
:
471.2 m2/g; 29Si MAS NMR (79.5 MHz): Q4 (δ=−111.7 ppm), Q3
C18H28O3Si: 320.18; Found: 319.20 [M-H]−
; Anal. Calcd. for
C18H28O3Si: C, 67.46; H, 8.81. Found: C, 67.28; H, 8.76%.
2.2. Preparation of In-SBA-15 (3)
In a typical synthesis, 2.0 g of the structure-directing agent,
pluronic P123, was fully dissolved in a mixture of 60 mL hydrochloric
acid (2.0 N) and 15 mL deionized water. Then, 4.05 mL (18.00 mmol)
of tetraethyl orthosilicate (TEOS) was added as the silica precursor
at 40 °C. After a TEOS pre-hydrolysis period of one hour, 0.64 g
(2.00 mmol) of 2 was added. The reaction mixture was stirred at 40 °C
Fig. 1. The solid-state NMR spectra of 3 and 5. (a) 29Si MAS NMR and (b) 13 C MAS NMR.

G. Liu et al. / Catalysis Communications 12 (2011) 655–659
657
analysis (%): C 14.42, H 2.96; dpore: 3.399 nm; SBET: 305.9 m2/g. 29Si
MAS NMR (300 MHz): Q4 (δ=−111.0 ppm), Q3 (δ=−102.8 ppm),
T3 (δ=−68.2 ppm); 13C CP MAS NMR (161.9 MHz): 0.1, 9.3, 15.6,
25.1, 44.5, 58.3, 124.9 ppm.
2.4. Catalytic reaction
A typical procedure is as follows: The solid catalyst (48.22 mg,
0.013 mmol based on Ir from ICP), KOH (22.0 mg, 0.40 mmol),
oxindole (0.266 mg, 2.0 mmol), and alcohols (2.2 mmol) and 2 mL
toluene were placed in a 25-mL thick-walled screw-cap vial. The vial
was purged with Ar and sealed with a screw-cap. The mixture was
placed in an aluminum block preheated to 110 °C and stirred for 20 h.
After completion of the reaction, the reaction mixture was allowed to
cool to room temperature followed by dilution with 2 mL of ethyl
acetate. The mixture was then stirred for 1 min, and the reactor was
centrifuged (10000 r/min) for 3–5 min. The solid was reused for
recycling experiment. The solution was purified by column chroma-
tography (2 in×12 in silica column) using n-hexane/EtOAc (4:1) as
eluent to afford the corresponding products.
Fig. 2. The powder XRD patterns of SBA-15, 3 and 5.
(δ=−102.9 ppm), T3 (δ=−67.3 ppm), T2 (δ=−60.8 ppm); 13C CP
MAS NMR (100.6 MHz): 8.1, 14.9, 24.9, 45.3, 58.4, 69.1, 124.3 ppm.
3. Results and discussion
2.3. Preparation of the indene-functionalized mesoporous iridium
3.1. Syntheses and structural characterizations of the catalyst 5
catalyst (5)
The indene-functionalized mesoporous materials and iridium
catalyst, abbreviated as In-SBA-15 (3) and Me-Ir-In-SBA-15 (5),
were prepared according to the procedures illustrated in Scheme 1.
Firstly, the key intermediate, indene-based silica resource 2, was
synthesized by the reaction of indene with n-BuLi followed by
coupling with 3-chloropropyltriethoxysilane (1) (NMR and IR Spectra
refer to the supporting information). The condensation 2 with Si
(OEt)4 was then carried out to afford 3 as a white powder following
a similar procedure reported in literature [29]. Finally, after
the protection of silicon-hydroxyl groups in 3 using trimethysilyl
(-SiMe3) group as a protection reagent [30], the resulting mixture
was reacted with n-BuLi followed by complexation with IrCl3 to
afford crude product. After removal of the unreacted start materials
and homogeneous omplexes via Soxlet extraction thoroughly in THF,
Me-Ir-In-SBA-15 (5) was obtained as a light yellow powder. The
inductively coupled plasma (ICP) optical emission spectrometer
analysis showed that Ir loading amount in the 5 was 53.52 mg
(0.28 mmol) per gram of catalyst.
Under argon atmosphere, a suspension of 3 (1.00 g) and HMDS
[(CH3)3Si)2N] (10 mL, 0.050 mol) in 25 mL dry toluene was stirred
overnight. The volatiles were stripped on a rotary evaporator and the
dry powder was washed five times with excess dry CH2Cl2 and finally
dried under vacuum at 60 °C for 6 h to afford end-capping of 3
(1.05 g) in the form of a white powder. Then it was suspended
in 20 mL dry THF again. Under argon atmosphere, to this stirred
suspension was added n-BuLi (2.00 mL, 5.00 mmol, 2.50 M in hexane)
at −60 °C. The resulting mixture was then allowed to warm to room
temperature slowly and stirred for another 1 h. After cooling down to
0 °C, a solution of IrCl3 (0.60 g, 2.00 mmol) in 5 mL dry THF was added
dropwise over 15 min. The mixture was then warmed up to room
temperature and stirred for further 5 h. After the solvent was removed
in vacuo, saturated NH4Cl was added to quench the reaction. The
mixture was then filtered through a filter paper and rinsed with
excess water and CH2Cl2, dry toluene. After Soxlet extraction in THF
solvent to remove unreacted start materials for 48 h, the solid was
dried at room temperature under vacuum overnight to afford catalyst
5 (0.78 g) as a light yellow powder. ICP analysis showed that the Ir
loading-amount is 53.52 mg per gram catalyst. IR (KBr) cm−1: 2964
(w), 2879 (w), 1643 (m), 1543 (w), 1454 (w), 1398 (w), 1257 (m),
1159 (m), 1081 (s), 848 (w), 802 (w), 755 (w), 457 (m); Elemental
The incorporation of indenyl groups and the complexation of
iridium onto the indene-functionalized mesoporous silica materials
could be further confirmed by FT-IR spectra (see the supporting
information) and solid-state NMR spectra. As shown in Fig. 1(a), the
29Si MAS NMR spectra of In-SBA-15 (3) and Me-Ir-In-SBA-15 (5)
Fig. 3. The TEM images of 3 and 5 viewed along [100] and [001] directions.

658
G. Liu et al. / Catalysis Communications 12 (2011) 655–659
3, the enhanced Q3–Q4 signals and disappeared Q2 in Me-Ir-In-SBA-
15 (5) suggested that 5 possessed mainly network structures of (HO)
Si(OSi)3} and {Si(OSi)4}, while the enhanced T3 and disappeared T2
signals in Me-Ir-In-SBA-15 (5) indicated the formation of {RSi(OSi)3}
(R = iridium complexes) as a part of wall in mesoporous silica
structure [32,33]. As marked in Fig. 1(b), the 13C CP/MAS NMR
spectra clearly displayed the peaks at 8.1, 14.9, 24.9, 45.3, 58.4, 69.1,
124.3 ppm for In-SBA-15 (3) and at 0.1, 9.3, 15.6, 25.1, 44.5, 58.3,
124.9 ppm for Me-Ir-In-SBA-15 (5), corresponding to indenyl and
aliphatic carbon atoms, respectively.
As shown in Fig. 2, the small-angle XRD patterns revealed that
In-SBA-15 (3) and Me-Ir-In-SBA-15 (5) showed one similar intense
d100 diffraction peak along with two similar weak diffraction peaks
(d110
, d200), suggesting that the dimensional-hexagonal pore
structure (p6mm) observed in pure SBA-15 [26] could be preserved
after the co-condensation and the complexation [34]. Compared
to pure SBA-15, the decreases of peak intensity in In-SBA-15 (3) and
Me-Ir-In-SBA-15 (5) implied that the incorporation of indenyl groups
and the complexation of iridium onto the indene-functionalized
mesoporous silica materials might disturb the highly ordered
mesoporous structure to a certain degree. The TEM morphologies
further confirmed that In-SBA-15 (3) and Me-Ir-In-SBA-15 (5)
had well-ordered mesostructures with the dimensional-hexagonal
arrangement as shown in Fig. 3. Nitrogen adsorption–desorption
isotherms in In-SBA-15 (3) and Me-Ir-In-SBA-15 (5) (Fig. 4) exhibited
typical IV type isotherms with H1 hysteresis loop and a visible step at
P/P0 =0.35–0.90, corresponding to capillary condensation of nitro-
gen in mesopores. As the structural parameters inserted in Fig. 2, the
protection of silicon-hydroxyl groups and the complexation of
iridium complexes onto the indene-functionalized mesoporous silica
materials caused a decrease in mesopore size, surface area, and pore
Fig. 4. The Nitrogen adsorption–desorption isotherms of SBA-15, 3 and 5.
showed two groups of signals with four oxygen neighbors (Q-type
species) originated from TEOS and with three oxygen neighbors
(T-type species) derived from silylether groups. Typical isomer
shift values were −91.5/−101.5/−110 ppm for Q2/Q3/Q4 signals
(Q2{(HO)2Si(OSi)2}, Q3 {(HO)Si(OSi)3}, Q4 {Si(OSi)4}) and −48.5/
−58.5/−67.5 ppm for T1/T2/T3 signals (T1{R(HO)2SiOSi}, T2 {R(HO)
Si(OSi)2}, T3 {RSi(OSi)3}) [31]. In-SBA-15 (3) showed three Q signals
(Q4:−111.7 ppm, Q3:−102.9 ppm, Q2:−94.3 ppm) and two T signals
(T2:−60.8 ppm and T3:−67.3 ppm), while the catalyst Me-Ir-In-
SBA-15 (5) only showed two Q signals (Q3:−102.8 ppm and Q4:
−111.0 ppm) and one T signal (T3:−68.2 ppm). In comparison with
Table 1
The catalytic C-3 alkylation of oxindole with various alcohols.a
Entry
Catalyst
R
Time
Yield (%)b
1
2
3
4
5
6
7
8
5
IrCl3
6
6
6
6
7
8
9
10
11
12
6
6
6
6
6
6
6
1
1
1
1
1
1
1
1
1
1
2
3
4
5
6
7
8
93.5
72.0c
91.7c
69.6c
90.3
Me-SBA-15+InIrCl2
Me-In-SBA-15+IrCl3
5
5
5
5
5
5
5
5
5
5
5
5
5
90.5
86.7
86.9
82.0
9
10
11
12
13
14
15
16
17
91.9
93.2d
92.8d
91.8d
91.5d
91.2d
91.0d
89.2d
a
Reaction conditions: solid catalyst (48.22 mg, 0.013 mmol based on Ir from ICP), KOH (22.0 mg, 0.40 mmol), oxindole (0.266 mg, 2.0 mmol), alcohols (2.2 mmol), toluene
(2 mL), reaction time 20 h., and reaction temperature 110 °C.
b
Isolated yields (NMR Spectra of products refer to the supporting information).
The amounts of solid catalysts [(IrCl3 (4.00 mg, 0.013 mmol) in entry 2, Me-SBA-15 (43.16 mg) plus InIrCl2 (5.06 mg, 0.013 mmol) in entry 3 and Me-In-SBA-15 (44.22 mg) plus
c
IrCl3 (4.00 mg, 0.013 mmol) in entry 4].
d
Recovered catalyst was used.

G. Liu et al. / Catalysis Communications 12 (2011) 655–659
659
volume, obviously due to coverage of pore surface with trimethysilyl
(-SiMe3) groups and/or iridium complexes, leading to an increase
of the wall thickness [32,33].
exhibited high catalytic activity in C-3 alkylation of oxindole with
various alcohols. More importantly, such a catalyst could be recovered
and reused eight times without affecting obviously its reactivity,
showing good potential in industrial application.
3.2. Catalytic property of the indene-functionalized mesoporous
catalyst 5
Acknowledgements
With the indene-functionalized mesoporous iridium catalyst
Me-Ir-In-SBA-15 (5) in hand, we examined its C-3 alkylation of
oxindole with alcohols according to the reported method in the
literature [11]. It was found that oxindole was reacted with 1.1
equiv. of benzalcohol to give a C-3 alkylation product in 93.5%
reaction yield, which was the nearly same as that of 94% isolated
yield using [Cp*IrCl2]2 as a catalyst [11], and obvious higher than
that of the parent catalyst IrCl3 (entry 1 versus entry 2). On the
basis of the about excellent result, the catalyst 5 was further inves-
tigated using a variety of alcohols as substrates (entries 5–10). In
general, a variety of alcohols were smoothly reacted with oxindole
to afford the corresponding desired products in high yields under
similar conditions. Neither the significant effect of reactant using
aromatic/aliphatic as substrates nor the obviously electronic effect of
substituent on the aryl ring were observed for this catalytic reaction.
In order to explore the catalytic nature of the indene-functionalized
mesoporous iridium catalyst and to eliminate the effect of non-
covalent adsorption on catalytic process, two control experiments
were carried out using Me-In-SBA-15 plus IrCl3 and SBA-15 plus InIrCl2
as catalysts under similar reaction conditions. It was found that the
former afforded the corresponding product in 69.6% isolated yield,
while the latter gave the corresponding product in 91.7% isolated
yield (entries 3 and 4). Low activity in the former suggested that
most of the postmodified IrCl3 had not been coordinated on catalytic
process, resulting in a low catalytic efficiency. High activity in the latter
indicated that the catalyst via non-covalent adsorption on catalytic
process also gave desired product in a high yield, suggesting the
catalytic microenvironment had not been changed on catalytic
process. However, both catalytic activities disappeared completely
when employed both above catalysts after Soxlet extracting in toluene,
indicating that the non-covalent adsorption of InIrCl2 and unreacted
starting materials of IrCl3 on catalytic process could be eliminated
through Soxlet extracting. This was also further proved by ICP analysis
(both nearly same amounts of Ir were detected in solution after
Soxlet extracting).
We are grateful to China National Natural Science Foundation
(20673072), Shanghai Sciences and Technologies Development Fund
(10dj1400103 and 10jc1412300), and Shanghai Municipal Education
Commission (No. 08YZ71 and S30406) for financial support.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
doi:10.1016/j.catcom.2010.12.021.
References
[1] S.E. Reisman, J.M. Ready, M.M. Weiss, A. Hasuoka, M. Hirata, K. Tamaki, T.V.
Ovaska, C.J. Smith, J.L. Wood, J. Am. Chem. Soc. 130 (2008) 2087.
[2] C.V. Galliford, K.A. Scheidt, Angew. Chem. Int. Ed. 46 (2007) 8748.
[3] T. Kagata, S. Saito, H. Shigemori, A. Ohsaki, H. Ishiyama, T. Kubota, J. Kobayashi,
J. Nat. Prod. 69 (2006) 1517.
[4] B. Volk, J. Barkóczy, E. Hegedus, S. Udvari, I. Gacsályi, T. Mezei, K. Pallagi, H.
Kompagne, G. Lévay, A. Egyed, L.G. Hársing, M. Spedding, G. Simig, J. Med. Chem.
51 (2008) 2522.
[5] A. Fensome, W.R. Adams, A.L. Adams, T.J. Berrodin, J. Cohen, C. Huselton, A.
Illenberger, J.C. Kern, V.A. Hudak, M.A. Marella, E.G. Melenski, C.C. McComas, C.A.
Mugford, O.D. Slayden, M. Yudt, Z. Zhang, P. Zhang, Y. Zhu, R.C. Winneker, J.E.
Wrobel, J. Med. Chem. 51 (2008) 1861.
[6] M.C. Michel, M. Oelke, N. Zinner, Drug Discov. Today 2 (2005) 1.
[7] H. Wang, M. Chen, L. Wang, Chem. Pharm. Bull. 55 (2007) 1439.
[8] A. Nimal, M. Benoit-Guyod, G. Leclerc, Eur. J. Med. Chem. 30 (1995) 973.
[9] A.S. Kende, J.C. Hodges, Synth. Commun. 12 (1982) 1.
[10] R. Grigg, C. Lofberg, S. Whitney, V. Sridharan, A. Keep, A. Derrick, Tetrahedron 65
(2009) 4375.
[11] T. Jensen, R. Madsen, J. Org. Chem. 74 (2009) 3990.
[12] S.J. Pridmore, J.M.J. Williams, Tetrahedron Lett. 49 (2008) 7413.
[13] F. Alonso, P. Riente, M. Yus, Eur. J. Org. Chem. (2008) 4908.
[14] M.S. Kwon, N. Kim, S.H. Seo, I.S. Park, R.K. Cheedrala, J. Park, Angew. Chem. Int. Ed.
44 (2005) 6913.
[15] K. Taguchi, H. Nakagawa, T. Hirabayashi, S. Sakaguchi, Y. Ishii, J. Am. Chem. Soc.
126 (2004) 72.
[16] K. Motokura, D. Nishimura, K. Mori, T. Mizugaki, K. Ebitani, K. Kaneda, J. Am. Chem.
Soc. 126 (2004) 5662.
[17] M. Heitbaum, F. Glorius, I. Escher, Angew. Chem. Int. Ed. 45 (2006) 4732.
[18] J. Horn, F. Michalek, C.C. Tzschucke, W. Bannwarth, Top. Curr. Chem. 242 (2004)
43.
An important feature of design of the indene-functionalized
mesoporous iridium catalyst is the easy and reliable separation via
simple filtration. Taking benzalcohol as an example, upon completion
of the reaction, Me-Ir-In-SBA-15 (5) was quantitatively recovered via
filtration. As shown in entries 11–17 in Table 1, the recycling catalyst
still afforded 89.2% yield after the eighth recycle, suggesting that the
catalyst with highly ordered dimensional-hexagonal mesostructure is
beneficial to uniform distribution catalytically active species and can
avoid the loss of catalyst. The gradual decrease of catalytic activity
as the catalyst was recycled was due to the slight loss of iridium
catalyst, which was confirmed by ICP analyses.
[19] J.M. Thomas, R. Raja, Acc. Chem. Res. 41 (2008) 708.
[20] M. Heitbaum, F. Glorius, I. Escher, Angew. Chem. Int. Ed. 45 (2006) 4732.
[21] T. Bein, Curr. Opin. Solid State Mater. Sci. 4 (1999) 85.
[22] C. Li, H.D. Zhang, D.M. Jiang, Q.H. Yang, Chem. Commun. (2007) 547.
[23] L. Mercier, T.J. Pinnavaia, Adv. Mater. 9 (1997) 500.
[24] X. Feng, G.E. Fryxell, L.Q. Wang, A.Y. Kim, J. Liu, K.M. Kemmer, Science 276 (1997)
923.
[25] D.S. Shepard, W. Zhou, T. Maschmeyer, J.M. Matters, C.L. Roper, S. Parsons, B.F.G.
Johnson, M.J. Duer, Angew. Chem. Int. Ed. 37 (1998) 2719.
[26] G.H. Liu, Y. Gao, X.Q. Lu, F. Zhang, M.M. Liu, H.X. Li, Chem. Commun. (2008) 3184.
[27] G.H. Liu, Y.Q. Sun, J.Y. Wang, C.S. Sun, F. Zhang, H.X. Li, Green Chem. 11 (2009)
1477.
[28] G.H. Liu, M. Yao, J.Y. Wang, X.Q. Lu, M.M. Liu, F. Zhang, H.X. Li, Adv. Synth. Catal.
350 (2008) 1464.
[29] Y. Wan, F. Zhang, Y.F. Lu, H.X. Li, J. Mol. Catal., A Chem. 267 (2007) 165.
[30] K. Pathak, A.P. Bhatt, S.H.R. Abdi, R.I. Kureshy, N.H. Khan, I. Ahmad, R.V. Jasra,
Tetrahedron Asymmetr. 17 (2006) 1506.
4. Conclusion
[31] O. Krőcher, O.A. Kőppel, M. Frőba, A. Baiker, J. Catal. 178 (1998) 284.
[32] H.X. Li, F. Zhang, Y. Wan, Y.F. Lu, J. Phys. Chem. B 110 (2006) 22942.
[33] H.X. Li, Q.F. Zhao, Y. Wan, W.L. Dai, M.H. Qiao, J. Catal. 244 (2006) 251.
[34] D. Zhao, Q. Huo, J. Feng, B.F. Chmelka, G.D. Stucky, J. Am. Chem. Soc. 120 (1998)
6024.
In conclusion, we supplied a co-condensation approach to prepare
an indene-functionalized mesoporous materials. The catalyst 5
synthesized through direct complexation of IrCl3 with this materials