Host (Nanocavity of aluminium-incorporated mesoporous KIT-6)-guest (12-tungesto(molybdato) phosphoric acid) nanocomposite material: Efficient and reusable catalysts for the Hosomi-Sakurai three-component coupling reaction

Article abstract of DOI:10.1080/10426507.2012.704100

The immobilization of heteropoly acids (HPAs) into the Al-functionalized KIT-6 mesoporous molecular sieve has been carried out to see the effect of Al-KIT-6 as a host matrix on the HPA activities. These modified mesoporous molecular sieves are effective c

Full text of DOI:10.1080/10426507.2012.704100

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Phosphorus, Sulfur, and Silicon and the
Related Elements
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Host (Nanocavity of Aluminium-
Incorporated Mesoporous KIT-6)–guest
(12-tungesto(molybdato) Phosphoric
Acid) Nanocomposite Material:
Efficient and Reusable Catalysts for
the Hosomi–Sakurai Three-Component
Coupling Reaction
Razieh Fazaeli a b , Hamid Aliyan c & Elham Naderi a
a Department of Chemistry, Shahreza Branch , Islamic Azad
University , 86145-311 , Shahreza , Isfahan , Iran
b Razi Chemistry Research Center, Shahreza Branch , Islamic Azad
University , Shahreza , Isfahan , Iran
c Department of Chemistry, Mobarakeh Branch , Islamic Azad
University , 84815-119 , Mobarakeh , Isfahan , Iran
Accepted author version posted online: 26 Jun 2012.Published
online: 31 May 2013.
To cite this article: Razieh Fazaeli , Hamid Aliyan & Elham Naderi (2013) Host (Nanocavity of
Aluminium-Incorporated Mesoporous KIT-6)–guest (12-tungesto(molybdato) Phosphoric Acid)
Nanocomposite Material: Efficient and Reusable Catalysts for the Hosomi–Sakurai Three-Component
Coupling Reaction, Phosphorus, Sulfur, and Silicon and the Related Elements, 188:6, 745-754, DOI:
10.1080/10426507.2012.704100
To link to this article: http://dx.doi.org/10.1080/10426507.2012.704100
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Phosphorus, Sulfur, and Silicon, 188:745–754, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.704100
HOST (NANOCAVITY OF ALUMINIUM-INCORPORATED
MESOPOROUS KIT-6)–GUEST
(12-TUNGESTO(MOLYBDATO) PHOSPHORIC ACID)
NANOCOMPOSITE MATERIAL: EFFICIENT AND
REUSABLE CATALYSTS FOR THE HOSOMI–SAKURAI
THREE-COMPONENT COUPLING REACTION
Razieh Fazaeli,1,2 Hamid Aliyan,3 and Elham Naderi1
1Department of Chemistry, Shahreza Branch, Islamic Azad University, 86145-311,
Shahreza, Isfahan, Iran
2Razi Chemistry Research Center, Shahreza Branch, Islamic Azad University,
Shahreza, Isfahan, Iran
3Department of Chemistry, Mobarakeh Branch, Islamic Azad University,
84815-119, Mobarakeh, Isfahan, Iran
GRAPHICAL ABSTRACT
Abstract The immobilization of heteropoly acids (HPAs) into the Al-functionalized KIT-6
mesoporous molecular sieve has been carried out to see the effect of Al-KIT-6 as a host matrix
on the HPA activities. These modified mesoporous molecular sieves are effective catalysts for
the Hosomi–Sakurai three-component coupling reaction via condensation of aldehydes, silyl
ethers, and allylsilanes.
Received 30 December 2011; accepted 13 June 2012.
We gratefully thank Dr. S. Taki for his kind help, and Shahreza Branch, Islamic Azad University for financial
support.
Address correspondence to Razieh Fazaeli, Department of Chemistry, Shahreza Branch, Islamic Azad
University, 86145-311, Shahreza, Isfahan, Iran. E-mail: fazaeli@iaush.ac.ir
745

746
R. FAZAELI ET AL.
Supplemental materials are available for this paper. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Keywords KIT-6; mesoporous silica; Hosomi–Sakurai reaction; multicomponent coupling;
alkoxytrimethylsilane; allyltrimethylsilane
INTRODUCTION
Since ordered mesoporous silicas, KSW-11 and MCM-41,2,3 were reported for the
first time in the 1990s, many other mesoporous silicas with various pore geometries, such
as MCM-48,3,4 SBA-15,5,6 SBA-16,6–8 KIT-6,9 and FDU-12,10,11 have been synthesized and
characterized chiefly by low-angle powder X-ray diffraction (XRD), transmission electron
microscopy (TEM), and N2 adsorption/desorption. The structure of the mesoporous in
KIT-6, similar to MCM-48,4 is body-centered cubic, space group Ia3d. Pure siliceous
KIT-6 material has an electronically neutral framework and is consequently devoid of
Bro¨nsted and Lewis acid sites. In order to improve the catalytic activity of this material, one
must incorporate heteroatoms into the framework either by grafting or by direct synthesis.
However, it is very difficult to prepare aluminium-incorporated KIT-6 by direct synthesis
under strongly acidic conditions due to dissolution of aluminum source.12
Hydrogen forms (or free acids) of heteropoly acids (HPAs) usually have low surface
areas (drawbacks of H3PW12O40 (PW12) and H3PMo12O40 (PMo12) are their low surface
areas, 1–5 m2 g−1, and low porosity, <0.1 cm3 g−1). Supported HPA catalysts have much
greater surface areas. Many attempts have been made to disperse and fix HPA catalysts
on various supports. Support materials, such as silica, carbon, and organic resins, have
been applied with varying levels of success, with new supporting materials and methods
being actively pursued.13,14 Although the structure and composition of the supported HPAs
are sometimes uncertain, high catalytic activities are often observed, and separation made
easier. For various reasons, such as efficiency, better accessibility to the active sites, and
cost, depositing on a support is currently favored.15,16
Homoallylic ethers represent valuable organic intermediates, which are amenable to
further synthetic manipulations.17,18 A direct approach to homoallylic ethers involves the
combination of an aldehyde with an allyltrimethylsilane and a silyl ether.
Many reagents have been reported in the literature for such three-component
Hosomi–Sakurai reactions, including trimethylsilyl iodide (TMSI),19 trimethylsilyl tri-
flate (TMSOTF),20 iron chloride (FeCl3),21 bismuth trifate [Bi(OTf)3],22 iron tosylate
[Fe(OTs)3],23 2,4-dinitrobenzenesulfonic acid (DNBA),24 montmorillonite K10 clay25 and
silicomolybdic acid/SiO2,26 trimethylsilylfluorosulfonate (TMSOFs),27 and I2.28 However,
these methods have several drawbacks. For example, (1) the catalyst separation and re-
cycling are difficult for homogeneous systems; (2) many of these methods use corrosive
and moisture sensitive catalysts such as Trimethylsilyl (TMS); and (3) metal triflates are
expensive and toxic. Moreover, the main disadvantage of the reported methods is that the
catalysts are destroyed in the work-up procedure and cannot be recovered or reused.
In continuation of our work on the catalytic properties of HPAs,29–31 herein, we wish
to report a mild and efficient method for the Hosomi–Sakurai three-component coupling
reaction via condensation of aldehydes (1), alkoxytrimethylsilanes (2), and allyltrimethyl-
silanes (3) in the presence of a catalytic amount of H3PW12O40 and H3PMo12O40 modi-
fied aluminium-incorporated mesoporous KIT-6 (hereafter denoted as PW12/Al-KIT-6 and
PMo12/Al-KIT-6, respectively) (Scheme 1).

HOSOMI–SAKURAI THREE-COMPONENT COUPLING REACTION
747
Scheme 1 HPA/Al-KIT-6-catalyzed three-component Hosomi–Sakurai reaction.
RESULTS AND DISCUSSION
Catalysts Characterization
The prepared catalyst was characterized by infrared spectroscopy (FT-IR), XRD, and
atomic absorption spectroscopy techniques.
FT-IR spectra have proved to be a powerful technique for studying surface interaction
between HPA and organic and inorganic supports. The infrared spectrum of PW12/Al-
KIT-6 exhibited strong vibrations at 1081 νas(P–Oa), 902 νas(W O W), and 809 cm−1
νas(W Oc W) (Figure 1a), while that of PMo12/Al-KIT-6 exhibited strong vibrations at
1083 νas(P–Oa), 962 νas(Mo Oa), and 809 cm−1 νas(Mo Oc Mo) (Figure 1b). Moreover,
the band located at 1632 cm−1 may be characteristic of the O–H stretching vibration.
Figure 2 shows the XRD patterns of PW12/Al-KIT-6 and PMo12/Al-KIT-6. The inter-
esting point is that PW12/Al-KIT-6 and PMo12/Al-KIT-6 also did not show characteristic
XRD pattern, although 35% wt% PMo12 and PW12 were loaded on the Al-KIT-6. This
indicates that the PW12 and PMo12 species were not in crystal state but in an amorphous-
like state, thereby demonstrating that Keggin species are finely and molecularly dispersed
on Al-KIT-6. After impregnation, the intensities of reflections decrease, which could be
assigned to decrease in electron density contrasted upon introduction of HPA species into
the mesopores of silica host materials.
The TEM picture of calcined PW12/Al-KIT-6 is shown in Figure 3. The sample for
the TEM measurement was suspended in ethanol and supported on a carbon-coated copper
grid. A well-resolved contrast characteristic of certain silica mesopore structure symmetry
is still observed, which is an indication of the preservation of the long ordered arrangement
of channels in the silica host matrix after aluminium deposition.12 The places with darker
contrast could be assigned to the presence of PW12 particles with different dispersion. The
small dark spots in the images could be ascribed to PW12 particles, probably located into the
support channels. The larger dark areas over the channels most likely correspond to PW12
agglomerates on the external surface. TEM images showed the presence of the well-ordered
cubic 3D mesoporous channels and confirmed that each PW12/Al-KIT-6 sample possesses
Ia3d cubic structure as does KIT-6.12
To obtain further information on the structure of the catalysts, we analyzed the
supported-HPAs by neutron activation analysis (NAA). The content of HPAs on the Al-KIT-
6 supports, which was calculated from W and Mo content in supported Al-KIT-6 catalysts,
was determined by NAA. A good distribution of elements analyzed is in agreement with
the atomic adsorption analysis, NAA, and ICP results with deviation in the range of 0.09.
The physicochemical properties of these supported catalysts by XRD, FT-IR, and NAA

748
R. FAZAELI ET AL.
Figure 1 FTIR spectra of (a) PW12/Al-KIT-6, and (b) PMo12/Al-KIT-6.
Figure 2 Powder XRD patterns of (a, c) PW12/Al-KIT-6, and (b, d) PMo12/Al-KIT-6.

HOSOMI–SAKURAI THREE-COMPONENT COUPLING REACTION
749
Figure 3 TEM images of PW12/Al-KIT-6 (60).
demonstrated that HPA was anchored on the surface of support and HPA still remained its
Keggin structure.
Physical properties of Al-KIT-6, PW12/Al-KIT-6, and the bulk-PW12 materials are
listed in Table 1. As expected, the BET surface areas, total pore volumes, and mesopore
sizes of Al-KIT-6 material decreased from 726 m2 g−1 to 138 (126) m2 g−1, 1.7 cm3 g−1 to
0.73 (0.61) cm3 g−1, and 6.8 nm to 4.3 (4.0) nm, respectively, after functionalization with
PW12 (PMo12). These changes reflect that part of the mesopore volume in the Al-KIT-6
matrix is filled with PW12 (or PMo12), resulting in pore diameters that are less than that of
silica channels.
Hosomi–Sakurai Three-Component Coupling Reaction via
Condensation of Aldehydes, Silyl Ethers, and Allylsilanes
The influence of various solvents on the yield of the reaction was investigated us-
ing benzaldehyde, allyltrimethylsilane, and ethoxytrimethylsilane (EtOTMS) as the model
reaction. Our studies toward the development of Hosomi–Sakurai reaction revealed that
PW12/Al-KIT-6 is a powerful catalyst, and acetonitrile is a suitable solvent for the allylation
Table 1 The texture parameters of parent Al-KIT-6 and PW12/Al-KIT-6 in comparison with the bulk PW12
materials
Texture parameters (N2 adsorption)
Materials
Surface area (m2 g−1 a
)
Pore volume (cm3 g−1 a
)
Pore diameter (nm)
Al-KIT-6
726
138
126
6
1.7
6.8
4.3
4.0
—
PW12/Al-KIT-6
PMo12/Al-KIT-6
Bulk-PW12
0.73
0.61
—
Bulk-PW12
8
0.01
—
aTotal pore volume measured at p/p0 = 0.99.

750
R. FAZAELI ET AL.
Table 2 Effect of different conditions in the reaction of benzaldehyde, ethoxysilane, and allyltrimethylsilane
after 3 ha
Catalyst (mol%)
Solvent
CH3CN
Temperature (◦C)
Yield (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
18
—
r.t.
8
75
72
34
98
85
98
78
95
62
55
45
43
43
28
33
58
55
21
17
Bulk-PW12 (3)
Bulk-PMo12 (3)
Al-KIT-6 (3)
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH2Cl2
CHCl3
THF
Hexane
MeOH
EtOH
1,4-Dioxane
DMF
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (2)
35% PW12/Al-KIT-6 (4)
25% PW12/Al-KIT-6 (3)
45% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
35% PW12/Al-KIT-6 (3)
45
Reflux condition
0
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
aReaction conditions: benzaldehyde (1 mmol), ethoxtrimethylysilane (2 mmol), allyltrimethylsilane (2 mmol),
catalyst, solvent (5 ml).
bIsolated yield.
of aldehydes. This model multicomponent reaction was conducted at room temperature.
Raising or lowering of the temperature did not result in any improvement (Table 2).
Therefore, we kept these parameters constant. Screening of the catalyst loading and the
equivalents of the reagents furnished our optimized conditions. Thus, one equivalent of
benzaldehyde reacted with two equivalents each of silyl ether and allylsilane in the pres-
ence of 0.1 g (3 mol%) of 35% PW12/Al-KIT-6 to give the desired product of 98%
yield.
We have also studied the similar reaction only in the presence of bulk PW12 and bulk
PMo12. Although these catalysts were active for the condensation reactions (Table 2, entries
2 and 3), the yields were insignificant when compared with yields with PW12/Al-KIT-6 and
PMo12/Al-KIT-6.
In order to show the general applicability of the protocol, we applied this catalytic
system for the preparation of other homoallylic ether derivatives (4) from several types
of aldehydes. Aromatic aldehydes carrying either electron donating or withdrawing sub-
stituents afforded high product yields with high purity (Table 3, entries a–f). Even for
thiophene-3-carbaldehyde and cinnamaldehyde, which normally show extremely poor
yields in the Hosomi–Sakurai three-component coupling reaction, better yields of the
corresponding homoallylic ether derivatives (Table 3, entries g and h; 78%, 75%) could be
obtained.
In order to show the merit of the present work in comparison with recently reported
protocols, we compared the results of the homoallylic ether derivatives synthesis from two
aldehydes in the presence of 2,4-dinitrobenzensulfonic acid (DNBA), and silicomolybdic

HOSOMI–SAKURAI THREE-COMPONENT COUPLING REACTION
751
Table 3 Three-component Hosomi–Sakurai reaction using aldehyde, R’OTMS, and allyltrimethylsilane in the
presence of PM12/Al-KIT-6 as catalyst
Entry
R
M
Rꢁ
Et
Time (h)
Yield (%)
a
b
c
d
e
f
C6H5
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
Mo
W
2
3
2
2.5
3
5
3.5
3.5
2
3
2.5
2
2.5
3
3
1.5
6
11
5
6.5
1
3
1
1
95
98
95
89
98
85
95
90
92
87
85
80
80
85
92
92
78
80
72
78
92
90
98
98
92
90
85
82
4-Me-C6H4
4-MeO-C6H4
4-Cl-C6H4
4-NO2-C6H4
3-NO2-C6H4
2-NO2-C6H4
3-Br-C6H4
Cinnamyl
C4H3S
Et
Et
Et
Et
Et
g
h
i
Et
Et
Et
j
Et
k
l
C6H5
Bn
Bn
Me
Me
4-Cl-C6H4
C6H5
m
n
2
2.5
3.5
6
4-NO2-C6H4
Mo
aReaction conditions: aldehyde (1 mmol), ethoxytrimethylsilane, benzyloxytrimethylsilane, or
methoxytrimethylsilane (2 mmol), allyltrimethylsilane (2 mmol), PM12/Al-KIT-6 (3 mol%), CH3CN
(5 mL).
bIsolated yield.
acid supported on silica gel with respect to the amount of the catalysts used, reaction time,
and yields of the products (Table 4). Comparison of PW12/Al-KIT-6 with these catalysts
for this reaction shows that the activity of PW12/Al-KIT-6 seems to be higher than or equal
to other known catalysts (Table 4).

752
R. FAZAELI ET AL.
Table 4 Comparison of PW12/Al-KIT-6 with two catalysts for synthesis of homoallylic ether derivatives
Time (h):Yield (%):mol (%)
Silicomolybdic
PW12/Al-KIT-6
(This work)
acid supported
on silica gel26
28
Entry
R
Rꢁ
DNBA24
AgF32
I2
1
2
C6H5
4-Cl-C6H5
Bn
Bn
1:92:2
1:98:2
3:92:3
4:86:3
—
0.75:99:2
12:>90:5a
12:>90:5a
0.75:86:10b
1:78:10b
aAt −78 ◦C.
bAt 0 ◦C.
CONCLUSIONS
We have developed an efficient strategy for the Hosomi–Sakurai three-component
coupling reaction via condensation of aldehydes, silyl ethers, and allylsilanes using HPA/Al-
KIT-6 as eco-friendly, inexpensive, and efficient catalysts. The advantages of this catalytic
system are mild reaction conditions, short reaction time, high product yield, easy preparation
of catalysts, non-toxicity of the catalysts, and simple and clean work-up of the desired
products.
EXPERIMENTAL
All materials were commercial reagent grade. Aldehydes, alkoxytrimethylsilanes,
and allyltrimethylsilanes were purchased from Merck or Aldrich. Infrared spectra
(400–4000 cm−1) were recorded from KBr pellets on a Nicolet Impact 400 D spectrometer.
The X-ray-powdered diffraction patterns were performed on a Bruker-D8 advance with
automatic control. The patterns were run with monochromatic Cu Kα (1.5406 Å) radiation
with a scan rate of 2◦ min−1. The micrographs were recorded using an SEM (HITACHI
COM-S-4200) operated at an accelerating voltage of 30 kV. The BET specific surface
areas and pore volumes of the catalysts were determined by the adsorption/desorption of
nitrogen at liquid nitrogen temperature with a Micromeritics Bel Sorp Mini II instrument.
The pore sizes of the catalysts were obtained from the peak positions of distribution curves
determined from the adsorption branches of isotherms.
Synthesis of HPA–modified Al-KIT-6 (35% PW12/Al-KIT-6 and 35%
PMo12/Al-KIT-6)
The supported HPA catalysts were prepared by the method of incipient wetness. In
a typical process, a 640-mg portion of HPA (PW12 or PMo12) was dissolved in deionized
water and impregnated dropwise into 1600 mg Al-KIT-6 (60) support in methanol (25 ml)
with constant agitation. The resulting pastes were dried for 4 h at 110 ◦C and calcined for
4 h at 350 ◦C31 (Scheme 2).
General Procedure for the Three-Component Hosomi–Sakurai Reaction
Aldehyde (1 mmol, 1.0 equiv.), an alkoxytrimethylsilane (2 mmol, 2.0 equiv.), and
allyltrimethylsilane (2 mmol, 2.0 equiv.) were added to a solution of 35% HPA/Al-KIT-6

HOSOMI–SAKURAI THREE-COMPONENT COUPLING REACTION
753
Scheme 2 Preparation of PW12/Al-KIT-6 and PMo12/Al-KIT-6.
(0.1 g, 3 mol%) in anhydrous CH3CN (1.5 mL) and stirred at room temperature for the
indicated time. The mixture was poured into brine (20 mL) and extracted with Et2O (3
× 50 mL). The combined organic layers were washed with aqueous NaHCO3 (20 mL)
and brine (20 mL), dried over Na2SO4, filtered, and concentrated. Homoallylic ether was
isolated by flash chromatography (silica, pentane/CH2Cl2, or pentane/Et2O).
SUPPLEMENTAL MATERIALS
Detailed characterization data for the synthesis of Al-KIT-612 and some spectra of
the product homoallylic ethers24 are contained in the Supplemental Materials file.
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