Iron-containing mesoporous aluminosilicate catalyzed direct alkenylation of phenols: Facile synthesis of 1,1-diarylalkenes

Article abstract of DOI:10.3762/bjoc.9.6

The addition of phenols to aryl-substituted alkynes to form 1,1-diarylalkenes was carried out by using the Fe-Al-MCM-41 catalyst. The catalyst showed remarkable improvement in time and yield in comparison to other solid catalysts. The heterogeneous cataly

Full text of DOI:10.3762/bjoc.9.6

Iron-containing mesoporous aluminosilicate
catalyzed direct alkenylation of phenols:
Facile synthesis of 1,1-diarylalkenes
Satyajit Haldar and Subratanath Koner*
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2013, 9, 49–55.
Department of Chemistry, Jadavpur University, Kolkata 700032, India
doi:10.3762/bjoc.9.6
Email:
Received: 19 October 2012
Accepted: 10 December 2012
Published: 09 January 2013
Subratanath Koner* - snkoner@chemistry.jdvu.ac.in
* Corresponding author
Associate Editor: C. Stephenson
Keywords:
1,1-diarylalkenes; heterogeneous catalysis; Fe-Al-MCM-41
© 2013 Haldar and Koner; licensee Beilstein-Institut.
License and terms: see end of document.
Abstract
The addition of phenols to aryl-substituted alkynes to form 1,1-diarylalkenes was carried out by using the Fe-Al-MCM-41 catalyst.
The catalyst showed remarkable improvement in time and yield in comparison to other solid catalysts. The heterogeneous catalyst
can be reused at least three times without a significant loss in activity.
Introduction
The direct vinylation of phenols has received considerable Mizoroki–Heck-type reaction could be considered as an effi-
attention by synthetic organic chemists for a long time. The cient procedure for the synthesis of such vinylated phenols
resulting 1,1-disubstituted alkene derivatives (Figure 1) are [18,19]. There are a number of reports available in the litera-
widely used as key starting materials in the synthesis of fine ture that involve Pd-catalyzed cross coupling reactions of
chemicals [1-7], polymers [8-14], and pharmaceuticals [15-17]. various aryl halides with different olefins. However, the major
Furthermore, a variety of available reactions to functionalize the drawback of the Mizoroki–Heck-type reaction in the synthesis
double bond, such as reductive (hydrogenation, hydrosilylation, of 1,1-disubstituted olefins rests on its poor selectivity toward
etc.), oxidative (epoxidation, halogenations, dihydroxylation, the formation of α-products [20-23]. In general, the reaction
etc.) or cycloaddition transformations, encourage such vinyla- shows β-selectivity, and there are only a few reports available
tion process as an attractive primary tool in organic synthesis. concerned with α-substituted products [24-26]. Sabarre and
Thus, the development of simple methods concerning such Love reported a one-pot rhodium-catalyzed alkyne hydrothiola-
vinylation reactions of phenols always remains an important tion followed by a nickel-catalyzed Kumada-type cross
process.
coupling with Grignard reagents to afford 1,1-disubstituted
49

Beilstein J. Org. Chem. 2013, 9, 49–55.
Results and Discussion
MCM-41 and Al-MCM-41 were prepared according to the
procedure described in our earlier report [33]. The incorpor-
ation of iron(III) was achieved in a similar way [33]. The meso-
porous patterns of MCM-41, Al-MCM-41 and Fe-Al-MCM-41
were established from the small-angle XRD patterns (see
Supporting Information File 1). The BET surface area and the
pore width of Fe-Al-MCM-41 were found to be 753 m2/g and
25.83 Å, respectively. The aluminium and iron contents of the
Fe-Al-MCM-41 catalyst were estimated by AAS method and
found to be 5.5 wt % and 0.80 wt %, respectively.
Initially, the Fe-Al-MCM-41-catalyzed reaction of phenylacety-
lene and phenol was carried out in different solvent media. The
progress of the reaction was monitored by analyzing the prod-
ucts with the help of gas chromatography (Table 1). Amongst
Figure 1: (RS)-Tolterodine, an important urological drug.
olefins [27]. Alternatively, Friedel–Crafts-type alkenylation various solvents, such as cyclohexane, CH3CN, CH3NO2,
could be a better choice to prepare such regiospecific vinyl CH3OH, CHCl3, 1,2-dichloroethane, and dichloromethane,
aromatic compounds. Yamaguchi et al. reported a direct ortho cyclohexane was found to be the most suitable solvent for the
alkenylation of phenols with 1-alkynes using SnCl4 and Bu3N reaction (Table 1, entry 7). Though a moderate yield was
in acetonitrile under reflux [28]. Further developments include obtained in 1,2-dichloroethane, no conversion was observed in
the metal trifluoromethanesulfonate-catalyzed Friedel–Crafts DCM (Table 1, entries 5–6). Comparing the reaction result in
alkenylation of arenes using alkynes by Tsuchimoto et al. [29] 1,2-DCE (bp 80 °C) and DCM (bp 40 °C), it seemed that
and the addition of simple arenes to arylacetylenes to afford temperature plays a crucial role in the activation of the sub-
exclusive 1,1-diarylethylenes through a C–C coupling reaction strate. Hence, further screening was done by performing the
catalyzed by a combination of Cu(OTf)2/TMSA (TMSA = same reaction in cyclohexane at different temperatures (Table 1,
trifluoromethanesulfonic acid) [30]. The same reaction was also entries 8 and 9). The best result was obtained at 80 °C, i.e., in
successfully carried out by Li and co-workers using FeCl3 as cyclohexane under reflux.
catalyst in a homogeneous medium [31]. Further Yadav et al.
demonstrated an elegant hydroarylation of different phenols in Since a number of pure aluminosilicates are known to catalyze
the presence of gallium(III) chloride [32]. Nevertheless, all of C–C coupling reactions [34-42], a detailed investigation was
these Lewis acid catalyzed Friedel–Crafts-type reactions have performed with various available aluminosilicate and siliceous
their own limitations. Being homogeneous catalytic systems, materials to understand the necessity of the iron center in the
these methods suffer from drawbacks, such as difficulty in catalyst Fe-Al-MCM-41. NaY, a microporous aluminosilicate,
recovery and reusability of the catalysts and tedious work-up did not yield any product under the specified reaction condi-
procedures. In addition, in most of the cases the utilization of tions (Table 2, entry 1). Sartori et al. reported an electrophilic
air-sensitive chemicals also restricts these methods to be carried alkenylation of aromatics with phenylacetylene over zeolite
out under inert conditions. To overcome such limitations, HSZ-360-Y; however, this zeolite is known to have a high
heterogeneous solid catalysts have recieved much attention over number of acidic sites in its porous structure [43]. They showed
the past few decades. The easy separation and possibility of that among various readily available porous aluminosilicates
reuse made their employment an attractive choice. Recently, we like HSZ-360-Y, ZSM-5-Y, K10 montmorillonite, etc., HSZ-
have successfully employed a Fe-Al-MCM-41 catalyst in a 360-Y was capable of catalyzing the electrophilic substitution
Friedel–Crafts-type hydroarylation reaction of styrenes [33]. process. However, a rigorous pretreatment is necessary to acti-
The catalyst demonstrated high yields of products with good vate the catalyst and a moisture-free medium is essential.
selectivities within a short reaction time under “open flask Furthermore, a higher temperature (110 °C) and a longer reac-
conditions”. On further exploration of the use of iron-based tion time (14 h) were also required for the catalytic reaction.
mesoporous aluminosilicate catalyst in the direct alkenylation Sartori et. al. suggested that the external surface of HSZ-360-Y
of arenes, we have succeeded in vinylation of various phenols zeolite was responsible for such catalytic activity rather than the
with different phenylacetylenes. In this paper we report a con- pore of the zeolite. As evidence, they reported the acidic-
venient method for the alkenylation of phenols with aryl-substi- alumina-catalyzed reaction in which only 25% product yield
tuted alkynes under mild conditions.
was observed [43]. However, when we used acidic alumina
50

Beilstein J. Org. Chem. 2013, 9, 49–55.
Table 1: Fe-Al-MCM-41-catalyzed reaction of phenylacetylene and phenola.
entry
temp. [°C]
solvent
time
conversion [%]b
yield [%]c
1
2
3
4
5
6
7
8
9
80
80
80
80
80
40
80
70
60
CH3CN
6
6
0
0
0
0
CH3NO2
CH3OH
6
4
0
CHCl3
6
0
0
1,2-DCE
DCM
2.5
6
88
0
71
0
cyclohexane
cyclohexane
cyclohexane
2
99
30
1
81
25
0
2.5
9
aReaction conditions: 1 mmol of phenylacetylene, 1.5 mmol of phenol, 65 mg of Fe-Al-MCM-41, 2 mL of solvent. bGC conversion of phenylacetylene.
cGC yield of alkenylated product.
(under our reaction conditions) at a relatively low temperature iron-exchanged Al-MCM-41 was employed as catalyst the reac-
(80 °C) without any pretreatment, no conversion was observed tion proceeded smoothly to afford high yields of products
(Table 2, entry 3). The basic and the neutral alumina also within very short reaction times. The reaction was performed
remained inactive in catalyzing the coupling reaction (Table 2, under “open-flask” conditions without any moisture-preventing
entries 4 and 5). This may be attributed to the low activation conditions, and no pretreatment of the catalyst was required.
energy or the lack of moisture-free conditions. However, when Notably, when the alumina support “Al-MCM-41” itself was
Table 2: Reactions of phenylacetylene with phenol with different catalystsa.
entry
catalyst
time (h)
conversion [%]b
yield [%]c
1
NaY
6
0
0
2d
3
HSZ-360-Y
14
6
55
3
52
0
acidic alumina
basic alumina
neutral alumina
Fe-Al-MCM-41
Al-MCM-41
4
6
0
0
5
6
0
0
6
2
99
2
81
0
7
6
8
MCM-41
6
0
0
9e
10f
11g
Fe-Al-MCM-41 (degraded)
GaCl3
12
6
48
–
45
75
0
FeCl3·6H2O (10 mol %)
12
0
aReaction conditions: 1 mmol of phenylacetylene, 1.5 mmol of phenol, 65 mg of catalyst, 2 mL of cyclohexane, 80 °C. bGC conversion of phenylacety-
lene. cGC yield of arylated products. dRef [43]. eSee Experimental for details. fRef [32]. gCatalyst: 2.32 mg of FeCl3·6H2O (0.008 mmol).
51

Beilstein J. Org. Chem. 2013, 9, 49–55.
used as catalyst, the conversion recorded was only 2% (Table 2, by proper treatment [48]. In that case, a long reaction time was
entry 7). The aluminium-free pure mesoporous silica, MCM-41, observed (Table 2, entry 9), as in the case of HSZ-360-Y.
displayed no catalytic activity, as expected (Table 2, entry 8).
This clearly indicates that the presence of iron in the catalyst On the basis of the optimized reaction conditions, the scope of
Fe-Al-MCM-41 is directly related to its superior performance in this Fe-Al-MCM-41 catalyzed C–C coupling reaction was
the catalytic reaction. Iron probably has some role in lowering further investigated. Various substituted phenols were used for
the activation energy of the reaction in synergy with the the alkenylation by phenylacetylene. The reaction preceded
aluminium moiety present in Al-MCM-41. The short reaction smoothly both in the case of electron-donating and -with-
time is probably due to the mesoporous structure of Fe-Al- drawing groups at the phenol. While p-Br-, p-Me- and p-OMe-
MCM-41 (pore width = 25.83 Å), which provides a higher phenol took about 1–2 hours for a good conversion, p-Cl-phenol
surface area to facilitate the reaction. It is well established that took slightly longer (viz. 2.5 hours) (Table 3, entries 2–5). In all
the site-isolation of active centers enhances the catalytic effi- cases a mono-alkenylated product at the ortho position was
cacy of the materials [44-47]. Owing to the large surface area of observed in high yield. Moreover, the catalyst showed regiose-
catalyst Fe-Al-MCM-41, iron centers are well dispersed in the lectivity in producing the 1,1-diarylalkene product. For alkynes,
mesoporous matrix. Thus, the catalyst attained the desired site- p-Me-substituted phenylacetylene was further used to explore
isolation of active centers for enhanced activity in catalytic the general acceptability of this reaction. In its reaction with
reaction. In fact, in order to investigate the role of mesoporous different substituted phenols a lowering of the reaction time was
structure, we further performed the reaction with “degraded-Fe- observed (Table 3, entries 6–9). Thus, Fe-Al-MCM-41 exhib-
Al-MCM-41” of which the mesoporous integrity was destroyed ited its efficiency in catalyzing the alkenylation of different
Table 3: Reactions of arenes with phenylalkynesa.
entry
1
arene
productb
time [h]
conversion [%]c
yield [%]d
81
2
99
1a
2
1
100
83
1b
3
4
5
2.5
1.5
2
93
99
99
75
87
89
1c
1d
1e
52

Beilstein J. Org. Chem. 2013, 9, 49–55.
Table 3: Reactions of arenes with phenylalkynesa. (continued)
6
0.75
100
86
2a
7
2
97
81
87
89
2b
8
1
100
100
2c
9
1.5
2d
aReaction conditions: 1 mmol of arylalkyne, 1.5 mmol of arene, 65 mg of Fe-Al-MCM-41, 2 mL of solvent, 80 °C. bmain product. cGC conversion of
phenylalkyne. dGC yield of alkenylated product.
phenols by various substituted/nonsubstituted phenylacetylenes
Table 4: Recycling of Fe-Al-MCM-41 catalyst for the reaction of phenol
to furnish the corresponding 1,1-diarylalkenes in high conver-
sion and selectivity within a short reaction time.
with phenylacetylene.
cycle
3
Furthermore, to verify whether the coupling reaction was truly
catalyzed by solid Fe-Al-MCM-41 or by the leached iron
species from the solid support, a “hot filtration” experiment was
undertaken. A reaction between phenol and phenylacetylene
was performed until 22% conversion was observed (monitored
by GC analysis) and then the catalyst was separated by simple
centrifugation under the hot conditions. No conversion in the
“catalyst-free centrifugate” was observed upon further heating
for 12 hours.
1
2
4
conversion (%)a
time (h)
99
2
97
2
98
96
2
2
yield (%)b
81
80
80
78
aGC conversion of phenylacetylene. bGC yield of arylated products.
Conclusion
In summary, Fe-Al-MCM-41 has been proven to be an efficient
Another most advantageous aspect of this type of solid-support catalyst for the alkenylation of phenols with aryl-substituted
catalyst is their scope for recycling. The reaction between alkynes. Various substituted arylalkynes and phenols afforded
phenol and phenylacetylene under optimized conditions was the 1,1-diarylethylenes under mild reaction conditions. The
chosen to evaluate the recyclability of Fe-Al-MCM-41. The reaction did not require any further addition of acids or special
catalyst was separated after the completion of the reaction by reagents such as additives, etc. The catalytic reactions can be
simple centrifugation. This recovered catalyst was washed with carried out under “open-flask conditions”. Furthermore, the
cyclohexane, then methanol followed by dichloromethane, and catalyst can be easily recovered from the reaction mixture by
dried at 80 °C for a few hours prior to its next use. The conver- simple centrifugation and can be reused several times without
sions of successive cycles are given in Table 4.
any special treatment other than washing.
53

Beilstein J. Org. Chem. 2013, 9, 49–55.
Experimental
Acknowledgements
General procedure for catalytic reactions: Phenylacetylene S.H. thanks CSIR, New Delhi, for the award of fellowships.
(1.0 mmol) was added to a mixture of phenol (1.5 mmol) and Financial support from CSIR, New Delhi by a grant (Grant No.
Fe-Al-MCM-41 (0.065 g) in 2 mL of cyclohexane. The mixture 01(2542)/11/EMR-II) (to S.K.) is gratefully acknowledged.
was stirred at 80 °C in an oil bath. To study the progress of the
References
1. Yuki, H.; Okamoto, Y.; Sadamoto, K. Bull. Chem. Soc. Jpn. 1969, 42,
reaction, the products were collected at different time intervals
and identified and quantified by gas chromatography. After
1754–1755. doi:10.1246/bcsj.42.1754
completion of the reaction, the solution was cooled down and
2. Brady, W. T.; Giang, Y. F. J. Org. Chem. 1985, 50, 5177–5179.
the catalyst was removed by centrifugation. The resulting crude
doi:10.1021/jo00225a039
mixture was gently evaporated under vacuum and purified by
3. Hayakawa, K.; Ohara, K.; Akagi, N.; Hirata, Y. Preparation of 1,
flash column chromatography on silica gel 230–400 by using an
1-diphenylethylene derivatives as starting materials for the synthesis of
appropriate solvent.
near-infrared-absorbing leuco dyes. Jpn. Kokai Tokkyo Koho
JP04338363, A, Nov 25, 1992.
4. D'Auria, M.; Esposito, V.; Mauriello, G. Tetrahedron 1996, 52,
14253–14272. doi:10.1016/0040-4020(96)00878-2
5. Vesterinen, A.-H.; Rich, J.; Seppälä, J. J. Colloid Interface Sci. 2010,
351, 478–484. doi:10.1016/j.jcis.2010.07.073
2-(1-phenylvinyl)phenol (1a) [43]: 1H NMR (300 MHz,
CDCl3) δ 7.40–7.32 (m, 5H, CH), 7.30–7.13 (m, 3H, CH),
6.97–6.94 (m, 2H, CH), 5.88 (d, J(H,H) = 0.6 Hz, 1H, CHH),
5.43 (s, 1H, CHH), 5.18 (s, 1H, OH).
6. Tavor, D.; Popov, S.; Dlugy, C.; Wolfson, A. Org. Commun. 2010, 3,
70–75.
7. Wang, X.; Guram, A.; Caille, S.; Hu, J.; Preston, J. P.; Ronk, M.;
Walker, S. Org. Lett. 2011, 13, 1881–1883. doi:10.1021/ol200422p
8. Kim, J.; Cho, J. C.; Kim, K. H.; Kim, K. U.; Jo, W. H.; Quirk, R. P.
ACS Symp. Ser. 1998, 704, 85–95. doi:10.1021/bk-1998-0704.ch007
9. Reutenauer, S.; Hurtrez, G.; Dumas, P. Macromolecules 2001, 34,
755–760. doi:10.1021/ma000676e
Synthesis of the catalyst (Fe-Al-MCM-41): As described in
our previous work [33], iron was incorporated into the meso-
porous aluminosilicate (Al-MCM-41) by the ion-exchange
method. A 0.5 g amount of Al-MCM-41 was added to 100 mL
0.001 M methanolic solution of FeCl3·6H2O, and the mixture
was stirred vigorously for 12 h. The resultant solid was then
filtered. To remove the excess FeCl3, the isolated solid was
washed by Soxhlet extraction using methanol. The resulting
solid was dried in an oven at 80 °C and characterized. The cata-
lyst was then used directly in reactions without any further acti-
vation.
10.Meyer, N.; Delaite, C.; Hurtrez, G.; Dumas, P. Polymer 2002, 43,
7133–7139. doi:10.1016/S0032-3861(02)00454-8
11.Viala, S.; Tauer, K.; Antonietti, M.; Krüger, R.-P.; Bremser, W. Polymer
2002, 43, 7231–7241. doi:10.1016/S0032-3861(02)00676-6
12.Kloninger, C.; Rehahn, M. Macromolecules 2004, 37, 1720–1727.
doi:10.1021/ma034909o
13.Grimsdale, A. C.; Chan, K. L.; Martin, R. E.; Jokisz, P. G.;
Holmes, A. B. Chem. Rev. 2009, 109, 897–1091.
doi:10.1021/cr000013v
Disintegration of mesoporous structure: The mesoporous
structure is known to disintegrate during boiling with water, due
to silicate hydrolysis [48]. The disintegration of the meso-
porous structure was achieved by boiling Fe-Al-MCM-41 with
millipore water. The liquid-to-sample ratio was fixed at 1 Lg−1.
After 12 h of heating, the sample was filtered and dried in an
oven for 2 h at 398 K. The XRD patterns of the dried sample
revealed that the mesoporous integrity was totally lost. The
catalytic reaction was performed with this “degraded-Fe-Al-
MCM-41” (Table 2, entry 9).
14.Tan, J. F.; Blencowe, A.; Goh, T. K.; Qiao, G. G.
Macromol. Rapid Commun. 2010, 31, 305–309.
doi:10.1002/marc.200900576
15.Evans, D.; Cracknell, M. E.; Saunders, J. C.; Smith, C. E.;
Williamson, W. R. N.; Dawson, W.; Sweatman, W. J. F. J. Med. Chem.
1987, 30, 1321–1327. doi:10.1021/jm00391a010
16.Botteghi, C.; Corrias, T.; Marchetti, M.; Paganelli, S.; Piccolo, O.
Org. Process Res. Dev. 2002, 6, 379–383. doi:10.1021/op020014k
17.Valcarcel, G.; Cristina, I.; Mantlo, N. B.; Shi, Q.; Wang, M.;
Winneroski, L. L., Jr.; Xu, Y.; York, J. S. Preparation of
aryloxyalkoxyphenylalkanoic acids and analogs, as PPAR modulators,
espeacially PPAR agonists. PCT Int. Appl. WO 2005019151, A1,
March 3, 2005.
Supporting Information
18.Mizoroki, T.; Mori, K.; Ozaki, A. Bull. Chem. Soc. Jpn. 1971, 44, 581.
doi:10.1246/bcsj.44.581
Supporting Information File 1
Experimental procedures with characterization data for all
compounds.
19.Heck, R. F.; Nolley, J. P. J. Org. Chem. 1972, 37, 2320–2322.
doi:10.1021/jo00979a024
20.Fristrup, P.; Le Quement, S.; Tanner, D.; Norrby, P.-O.
Organometallics 2004, 23, 6160–6165. doi:10.1021/om0494521
21.Cabri, W.; Candiani, I. Acc. Chem. Res. 1995, 28, 2–7.
doi:10.1021/ar00049a001
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-9-6-S1.pdf]
22.Djakovitch, L.; Koehler, K. J. Am. Chem. Soc. 2001, 123, 5990–5999.
doi:10.1021/ja001087r
54

Beilstein J. Org. Chem. 2013, 9, 49–55.
23.Mo, J.; Xu, L.; Xiao, J. J. Am. Chem. Soc. 2005, 127, 751–760.
doi:10.1021/ja0450861
License and Terms
And references therein.
This is an Open Access article under the terms of the
Creative Commons Attribution License
24.Ruan, J.; Iggo, J. A.; Berry, N. G.; Xiao, J. J. Am. Chem. Soc. 2010,
132, 16689–16699. doi:10.1021/ja1081926
25.Matsubara, R.; Gutierrez, A. C.; Jamison, T. F. J. Am. Chem. Soc.
2011, 133, 19020–19023. doi:10.1021/ja209235d
26.Ruan, J.; Xiao, J. Acc. Chem. Res. 2011, 44, 614–626.
doi:10.1021/ar200053d
(http://creativecommons.org/licenses/by/2.0), which
permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
27.Sabarre, A.; Love, J. Org. Lett. 2008, 10, 3941–3944.
doi:10.1021/ol8012843
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
28.Yamaguchi, M.; Hayashi, A.; Hirama, M. J. Am. Chem. Soc. 1995, 117,
1151–1152. doi:10.1021/ja00108a041
(http://www.beilstein-journals.org/bjoc)
29.Tsuchimoto, T.; Maeda, T.; Shirakawa, E.; Kawakami, Y.
Chem. Commun. 2000, 1573–1574. doi:10.1039/b003702h
30.Bhilare, S. V.; Darvatkar, N. B.; Deorukhkar, A. R.; Raut, D. G.;
Trivedi, G. K.; Salunkhe, M. M. Tetrahedron Lett. 2009, 50, 893–896.
doi:10.1016/j.tetlet.2008.12.031
The definitive version of this article is the electronic one
which can be found at:
doi:10.3762/bjoc.9.6
31.Li, R.; Wang, S. R.; Lu, W. Org. Lett. 2007, 9, 2219–2222.
doi:10.1021/ol070737u
32.Yadav, J. S.; Reddy, B. V. S.; Sengupta, S.; Biswas, S. K. Synthesis
2009, 1301–1304. doi:10.1055/s-0028-1088027
33.Haldar, S.; Koner, S. J. Org. Chem. 2010, 75, 6005–6008.
doi:10.1021/jo100803y
34.Armengol, E.; Cano, M. L.; Corma, A.; García, H.; Navarro, M. T.
J. Chem. Soc., Chem. Commun. 1995, 519–520.
doi:10.1039/c39950000519
35.Corma, A. Chem. Rev. 1997, 97, 2373–2420. doi:10.1021/cr960406n
36.Koch, H.; Liepold, A.; Roos, K.; Stöcker, M.; Reschetilowski, W.
Chem. Eng. Technol. 1999, 22, 807–811.
doi:10.1002/(SICI)1521-4125(199910)22:10<807::AID-CEAT807>3.0.C
O;2-4
37.Taguchi, A.; Schüth, F. Microporous Mesoporous Mater. 2005, 77,
1–45. doi:10.1016/j.micromeso.2004.06.030
38.Agúndez, J.; Díaz, I.; Márquez-Álvarez, C.; Pérez-Pariente, J.;
Sastre, E. Chem. Commun. 2003, 150–151. doi:10.1039/B209983G
39.Perego, C.; de Angelis, A.; Carati, A.; Flego, C.; Millini, R.; Rizzo, C.;
Bellussi, G. Appl. Catal., A 2006, 307, 128–136.
doi:10.1016/j.apcata.2006.03.013
40.Iwanami, K.; Choi, J.-C.; Lu, B.; Sakakura, T.; Yasuda, H.
Chem. Commun. 2008, 1002–1004. doi:10.1039/B718462J
41.Pega, S.; Boissière, C.; Grosso, D.; Azaïs, T.; Chaumonnot, A.;
Sanchez, C. Angew. Chem., Int. Ed. 2009, 48, 2784–2787.
doi:10.1002/anie.200805217
42.Robinson, M. W. C.; Davies, A. M.; Mabbett, I.; Davies, T. E.;
Apperley, D. C.; Taylor, S. H.; Graham, A. E. J. Mol. Catal. A: Chem.
2010, 329, 57–63. doi:10.1016/j.molcata.2010.06.018
43.Sartori, G.; Franca Bigi, F.; Pastorío, A.; Porta, C.; Arienti, A.;
Maggi, R.; Moretti, N.; Gnappi, G. Tetrahedron Lett. 1995, 36,
9177–9180. doi:10.1016/0040-4039(95)01934-A
44.Sharma, K. K.; Asefa, T. Angew. Chem., Int. Ed. 2007, 46, 2879–2882.
doi:10.1002/anie.200604570
45.Sharma, K. K.; Anan, A.; Buckley, R. P.; Ouellette, W.; Asefa, T.
J. Am. Chem. Soc. 2008, 130, 218–228. doi:10.1021/ja074128t
46.Yu, K.; McKittrick, M. W.; Jones, C. W. Organometallics 2004, 23,
4089–4096. doi:10.1021/om049765w
47.Müller, C.; Ackerman, L. J.; Reek, J. N. H.; Kamer, P. C. J.;
van Leeuwen, P. W. N. M. J. Am. Chem. Soc. 2004, 126,
14960–14963. doi:10.1021/ja046901f
48.Kim, J. M.; Ryoo, R. Bull. Korean Chem. Soc. 1996, 17, 66–68.
55