Chiral Dawson-Type Hybrid Polyoxometalate Catalyzes Enantioselective Diels-Alder Reactions

Article abstract of DOI:10.1002/chem.201502839

Can achiral organocatalysts linked to chiral polyanionic metal oxide clusters provide good selectivity in enantioselective C-C bond formations? The answer to this question is investigated by developing a new active hybrid polyoxometalate-based catalyst for asymmetric Diels-Alder reaction. Chirality transfer from the chiral anionic polyoxometalate to the covalently linked achiral imidazolidinone allows Diels-Alder cycloaddition products to be obtained with good yields and high enantioselectivities when using cyclopentadiene and acrylaldehydes as partners.

Full text of DOI:10.1002/chem.201502839

DOI: 10.1002/chem.201502839
Full Paper
&
Asymmetric Catalysis
Chiral Dawson-Type Hybrid Polyoxometalate Catalyzes
Enantioselective Diels–Alder Reactions
Wen-Jing Xuan,[a, b] Candice Botuha,[a, b] Bernold Hasenknopf,*[a, b] and Serge Thorimbert*[a, b]
Abstract: Can achiral organocatalysts linked to chiral polyan-
ionic metal oxide clusters provide good selectivity in enan-
tioselective CÀC bond formations? The answer to this ques-
tion is investigated by developing a new active hybrid poly-
oxometalate-based catalyst for asymmetric Diels–Alder reac-
tion. Chirality transfer from the chiral anionic polyoxometa-
late to the covalently linked achiral imidazolidinone allows
Diels–Alder cycloaddition products to be obtained with
good yields and high enantioselectivities when using cyclo-
pentadiene and acrylaldehydes as partners.
Introduction
POM platforms whereby the chiral information comes from the
organic part via electrostatic effects or covalent bonds.[10,11]
Some of these architectures have been used to catalyze organ-
ic transformations but few of them have effected efficient
transfer of stereochemical information.
For several decades, polyoxometalates (POMs)[1] have been the
subject of important developments in materials science[2] and
biology,[3] and have become established as efficient catalysts
due to their acid–base and redox properties.[4] The use of
chiral POMs in these fields is less well developed,[5] despite the
obvious importance of chirality in biology and synthesis. Fur-
thermore, POMs are often considered as molecular models of
bulk metal oxides. Thus, chiral POMs represent a model for
chiral metal oxide surfaces.[6] Considering the huge importance
of metal oxides in catalytic transformations, there is relatively
little known about chiral oxide surfaces and their mode of in-
teraction with organic molecules. Chiral recognition on surfa-
ces (of a POM or bulk metal oxide) and the transfer of chirality
from a surface to organic substrates are promising fields of in-
vestigation for the development of future enantioselective cat-
alysts where the chiral information no longer relies on chiral
organic molecules.[6,7] One should note also that discrimination
on chiral surfaces might have played a major role in prebiotic
chemistry and the occurrence of chiral biomolecules.[8]
The concept of asymmetric catalysis by ion pairing and/or
hydrogen bonding, which has progressed exponentially in the
last decade, is well suited for original discoveries at the inter-
face of organic and inorganic chemistry. Asymmetric catalysis
through temporary covalent bonding in addition to noncova-
lent interactions has been exploited and is of prime interest
for reactions giving high enantioselectivities. Indeed, the
higher the organization in the transition state is, the higher
the stereoinduction can be expected.[12] We realized that our
POM hybrids could fulfill these requirements and hypothesized
that the polyanionic POM framework could act as a chiral
counter ion and thus influence the reaction stereoselectivity.
In line with our research regarding the preparation and use
of POM hybrids, we reported very low enantioselectivity in the
acylation of indenyl anions. We realized that the chiral POM
was at a too long distance from the approaching prochiral nu-
cleophile to efficiently control the configuration of the quater-
nary carbons during the CÀC bond formation (Figure 1a).[13] In-
spired by the known mechanism of imidazolidinone-catalyzed
reactions, in which the transition states involved iminium spe-
cies,[14] we selected the Diels–Alder reaction between croton-
aldehyde and cyclopentadiene as a new benchmark model.
We anticipated that the reactive prochiral unsaturated double
bond could be closer to the chiral POM, giving a better trans-
fer of the chiral information from the inorganic cluster to the
created stereogenic centers (Figure 1b).
Considerable advances in the preparation of chiral POMs
have emerged in recent years.[5] The first major approaches to
obtain enantiopure chiral POM-based frameworks were built
on spontaneous resolution upon crystallization or on supra-
molecular assemblies.[9] Besides, chiral organic or metallo-or-
ganic species can be introduced through ion-pair interactions
or direct ligation to POMs to create efficient chiral entities.[10]
Most of these homogeneous catalysts are derived from achiral
[a] W.-J. Xuan, Dr. C. Botuha, Prof. B. Hasenknopf, Prof. S. Thorimbert
Sorbonne UniversitØs, UniversitØ Pierre et Marie Curie Paris 06, UMR 8232
Institut Parisien de Chimie MolØculaire (IPCM), 75005 Paris (France)
E-mail: bernold.hasenknopf@upmc.fr
Results and Discussion
serge.thorimbert@upmc.fr
An intrinsically chiral POM framework can be obtained by
the formation of a vacancy, which is subsequently replaced
with other metals.[5] In this study, we employed the a1-tin-
[b] W.-J. Xuan, Dr. C. Botuha, Prof. B. Hasenknopf, Prof. S. Thorimbert
CNRS, UMR 8232, IPCM, 75005 Paris (France)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201502839.
substituted
Dawson
oxo-acyl
anhydride
(TBA)6[a1-
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Table 1. Diels–Alder reaction between cyclopentadiene and crotonalde-
hyde with POM-Imidazolidinone catalysts 3.[a]
Entry Cat.
Yield [%][b] exo/endo[c] exo ee [%][d] endo ee [%][d]
1
3a
95
87
19
45
67:33
69:31
46:54
59:41
57:43
25:75
54
55
0
0
0
46
46
<5
8
0
0
2[e]
3
3a
3b
3c
4
5
6
Boc-2a 58
29
–
0
[a] Absolute configuration assigned by chemical correlation to a known
compound (see the Supporting Information); [b] yields of isolated exo
and endo isomers; [c] diastereoselectivity determined by 1H NMR spec-
troscopy of the crude; [d] ee values were determined by GC analysis on
a chiral phase; [e] reaction stopped after 2 days.
Figure 1. Chiral POM associated to activated reactive functions.
P2W17O61{SnCH2CH2C(=O)}] (1; >99% ee; TBA=tetra-n-butylam-
monium) as an inherently chiral platform.[15] Since it can be fur-
ther functionalized by amide bond formation, it is a convenient
and easily prepared starting material to study the transfer of
stereochemical information from inorganic metal oxide surface
to organic molecules. Moreover, the polyanionic structure of
POMs is relevant for supramolecular contacts with organics by
hydrogen bonding or electrostatic interactions.[15c]
slightly diminished the yield to 87% but did not modify the
overall stereoselectivity (Table 1, entry 2). Interestingly, our ho-
mogeneous catalyst favored the formation of the exo cycload-
duct. For steric reasons, (supported) imidazolidinone-catalyzed
Diels–Alder reactions between unsaturated aldehydes and cy-
clopentadiene are known to give exo/endo ratios close to
50:50.[14a,17] In our experiments, the observed 67:33 exo/endo
ratio highlights that our bulky hybrid POM is close to the reac-
tive centers. A drop in both reactivity and enantioselectivity
was observed when the more sterically constrained catalysts
3b and 3c were applied (Table 1, entries 3 and 4).[18] Moreover,
control experiments were conducted by either omitting hybrid
catalyst 3 or by using simple N-Boc-protected amino imidazoli-
dinone 2a, revealing an expected low and non-enantioselec-
tive reactivity (Table 1, entries 5 and 6). We also tested the acti-
vated POM (À)-1 as a catalyst, but no enantioselectivity was
detected in the products. Consequently, catalyst 3a was select-
ed to further optimize the reaction conditions. Among the dif-
ferent solvents we tested, CH2Cl2 and CH3CN were the most ef-
ficient with slightly better yields observed for CH2Cl2. THF,
a THF/H2O solvent mixture 95:5 v/v, or polar solvents (tBuOH,
iPrOH) gave either lower conversion or enantioselectivities.
We next turned our attention to the effect of the acid coca-
talyst. The presence of an acid cocatalyst is required and was
found to have a positive effect on both yield and enantioselec-
tivity. (Table 2, entries 1 and 2). The reaction gave higher yields
but lower enantioselectivities in the presence of a stronger
acid such as trifluoroacetic acid (TFA; Table 2, entry 3). HCl had
a negative effect on both the yield and the ee. (Table 2,
entry 4). Interestingly, the chiral (S)-10-camphorsulfonic acid
(CSA) gave the Diels–Alder adduct in comparable stereoselec-
tivities but in lower yields (Table 2, entry 5). It should be noted
that CSA alone without POM 3a catalyzed the reaction but did
not lead to any enantioselectivity.
Three kinds of achiral amino ethyl imidazolidinones 2 were
prepared following known procedures,[16] whereas catalysts
3a–c were prepared without special precautions as follows:[15b]
the chiral activated POM platform 1 was treated with amines
2a–c in the presence of Et3N to afford, after precipitation with
Et2O, the corresponding hybrids 3a–c in high yields (150–
300 mg, 85–91%; Scheme 1). They showed the expected sig-
nals for the organic and inorganic moieties in 1H, 13C and
31P NMR spectroscopy, and ESI-MS further confirmed their com-
position (see the Supporting Information).
Scheme 1. Synthesis of chiral polyoxometalate–imidazolidinone hybrids.
The cycloaddition between crotonaldehyde and cyclopenta-
diene was efficiently promoted by a combination of 3a
(5 mol%) and 2,4-dinitrobenzoic acid (DNBA; 5 mol%) for three
days at room temperature in CH2Cl2 (Table 1, entry 1). Satisfy-
ingly, we isolated the cycloadduct in 95% overall yield as a mix-
ture of endo and exo bicyclic products with enantiomeric ex-
cesses of 54 and 46%, respectively. A 2 day reaction time
These experiments performed so far revealed some trends
on the active catalytic species. Indeed, the relative acidity
seems to be less important than the nature of the correspond-
ing conjugate base. We speculate that the strong influence of
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Table 2. Cocatalyst effects on the Diels–Alder reaction.[a]
Table 3. Scope of the POM–imidazolidinone 3a catalyzed Diels–Alder re-
action.[a]
Entry Cocat.
Yield [%][b] exo/endo[c] exo ee [%][d] endo ee [%][d]
Entry
R
Yield [%][b] exo/endo[c] exo ee [%][d] endo ee [%][d]
1
2
3
4
5
6
–
9
65:35
69:31
68:32
69:31
68:32
66:34
39
55
22
48
59
58
22
46
9
DNBA 87
TFA
HCl
(S)-CSA 38
cat. 4 41
1
2
3
4
5[e]
6
7
8[f]
Me
Pr
H
CO2Et
CO2Et
Ph
87
29
96
100
86
38
69:31
72:28
32:68
45:55
42:58
80:20
84:16
84:16
55 (2R)
55 (2R)
0
0
0
88 (2S)
86 (2S)
86 (2S)
46 (2R)
49 (2R)
0
0
0
72 (2S)
64 (2S)
78 (2S)
97
46
32
41
29
[a] Absolute configuration assigned by chemical correlation to a known
compound (see the Supporting Information); [b] yields of isolated exo
and endo isomers; [c] diastereoselectivity determined by 1H NMR spec-
troscopy of the crude; [d] ee values were determined by GC analysis on
a chiral phase.
4-NO2Ph 100
4-NO2Ph 100
[a] Absolute configuration assigned by chemical correlation to a known
compound (see the Supporting Information); [b] yields of isolated prod-
ucts as mixture of exo and endo isomers; [c] determined by H NMR spec-
1
troscopy of the crude; [d] ee values were determined by GC or HPLC on
a chiral phase; [e] reaction run without catalyst 3a. [f] 2.5 mol% of cata-
lyst was used.
the acid cocatalyst on both reactivity and enantioselectivity is
due to a competitive association of its conjugate base with
either iminium or TBA counter ions.[19]
To further understand this ion-pairing effect, we prepared
and isolated POM–imidazolidinium 4 (Figure 2) by mixing POM
3a with TFA in a THF/CH3CN solution and precipitating by
but with no enantioselectivity. This is due to the proton-cata-
lyzed side reaction, which can now compete (Table 3, en-
tries 3–5). As for other homogeneous imidazolidinone-organo-
catalyzed reactions, the catalyst 3a is not efficient with a-
methyl-substituted a,b-unsaturated aldehydes, such as metha-
crolein (low conversion, no enantioselectivity) and tiglic alde-
hyde (no conversion). Finally, b-aryl-substituted dienophiles
provided somewhat higher diastereo- and enantioselectivities
with moderate to excellent yields (Table 3, entries 6 and 7). By
decreasing the catalyst loading to 2.5 mol%, the reactive 4-ni-
trophenylacrylaldehyde reacted with the same high efficiency,
giving after 2 days, a quantitative overall yield of the cycload-
duct in a 84:16 exo/endo ratio with enantioselectivities of 86
and 78%, respectively (Table 3, entry 8).
Figure 2. Proposed structure of POM–imidazolidinium 4.
adding Et2O. The solid was characterized as the expected
hybrid POM 4, whereas the filtrate, after evaporation of the
solvents, afforded CF3COO·TBA as the residue (see the Support-
ing Information). By using 5 mol% of 4 to catalyze the studied
Diels–Alder reaction, the enantioselectivities for both endo and
exo products were significantly higher than those obtained by
simply mixing 3a with TFA (Table 2, entries 3 and 6). The selec-
tivity of the reaction reached the same level as in the DNBA
case. However, the yield of the reaction dropped to 41%, re-
vealing a decrease in the efficiency of the catalyst due to possi-
ble partial decomposition. We thus confirmed that the nature
of the anion associated to the catalytically active intermediate
is essential for modulating both the reactivity and the stereo-
selectivity of the reaction.[20]
The origin for this unique chirality transfer from the chiral
POM to the new organic molecule (Scheme 2) is assumed to
involve an iminium intermediate.[21] The protonation of the
hybrid POM 3 by the acid cocatalyst leads to an equilibrium
that determines the overall reactivity with the unsaturated al-
dehydes. After formation of the usual conjugated iminium spe-
cies A (established by ESI-MS; see the Supporting Informa-
tion),[22] the electrostatic interaction and the hydrogen bonding
between the amide NH and the oxido ligands[15a] hold the or-
ganic chain close to the inorganic surface. Because of the chir-
ality of the POM, one sense for the wrapping of the organic
chain around the POM is preferred to the other. This helical ori-
entation might justify the origin of the enantioselectivities ob-
served during the formation of B. Indeed, only one face of the
unsaturated iminium in A should be accessible to the diene.
The unfolded conformation A’ is certainly more reactive but
should not give rise to enantioselectivity, as both faces of the
prochiral unsaturated iminium A’ are reactive. The affinity of
the iminium for the oxide surface in comparison to the conju-
gated base of the acid cocatalyst (XÀ) is crucial for the equilib-
rium between A and A’. Finally, after cycloaddition with cyclo-
Experiments to probe the scope of the dienophiles are sum-
marized in Table 3. The POM–imidazolidinone-catalyzed cyclo-
addition tolerates a range of b-substituted dienophiles. Alkylat-
ed b-substituted dienophiles were sensitive to steric hindrance,
which led to lower reactivity but almost no loss of enantiose-
lectivity (Table 3, entries 1 and 2). However, the reactions of
the less constrained and more reactive unsubstituted a,b-unsa-
turated aldehydes provide the desired product in good yields
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product (23 mg, 87% yield). Prepa-
ration of catalysts, GC, HPLC and
ESI-MS studies and other full char-
acterization are included in the
Supporting Information.
Acknowledgements
We thank the UniversitØ Pierre et
Marie Curie (UPMC) and CNRS
for funding. The FØdØration de
Recherche (FR2769) provided
technical access for analysis.
W.J.X. acknowledges the China
Scholarship Council (CSC) for
a PhD fellowship.
Keywords: chirality
cycloaddition
reaction
polyoxometalates
·
·
Diels–Alder
·
organocatalysis
·
[1] a) R. Neumann in Modern Oxidation
Methods (Ed.: J. E. Bäckvall), Wiley-
VCH, Weinheim, 2004, pp. 223–
251; b) C. L. Hill in Comprehensive
Coordination Chemistry II, Vol.
4
Scheme 2. Mechanism and origin of enantioselectivity in the studied reaction.
(Ed.: A. G. Wedd), Elsevier, Oxford,
2004, pp. 679–759; c) M. T. Pope
in Comprehensive Coordination
Chemistry II, Vol.
4 (Ed.: A. G.
pentadiene, hydrolysis of iminium intermediate B liberates the
bicyclic product and regenerates the catalyst/cocatalyst
system.
Wedd), Elsevier, Oxford, 2004, pp. 635–678; d) D.-L. Long, E. Burkholder,
L. Cronin, Chem. Soc. Rev. 2007, 36, 105–121; e) N. Mizuno, K. Kamata,
Coord. Chem. Rev. 2011, 255, 2358–2370; f) M. T. Pope, U. Kortz, Polyoxo-
metalates in Encyclopedia of Inorganic and Bioinorganic Chemistry (Ed.:
R. A. Scott), John Wiley & Sons, Hoboken, NJ, 2012; g) Polyoxometalates
(Cluster Issue), Eur. J. Inorg. Chem. (Guest Eds.: U. Kortz, T. Liu), 2013,
pp. 1556–1967; h) Polyoxometalates (Cluster Issue), Chem. Soc. Rev.
(Guest Eds.: L. Cronin, A. Müller), 2012, 41, pp. 7333–7634.
Conclusion
In summary, a new type of chiral hybrid POM–imidazolidinone
catalyst was synthesized and used to perform the first efficient
chirality transfer from an intrinsically chiral inorganic oxide sur-
face, represented by the POM cluster, to organic molecules. As
for the mechanism, competitive ion pairing between the posi-
tive iminium side chain and either the anionic POM surface or
the cocatalyst anion seems essential to determining the reac-
tion rate and enantioselectivity. This study opens an entry to
the challenging fields of asymmetric catalysis using POMs or,
more generally speaking, for using inorganic oxides as
a source for chiral information. Further studies to address the
scope of this new catalytic strategy will be forthcoming.
[2] a) M. Carraro, S. Gross, Materials 2014, 7, 3956–3989; b) A. Dolbecq, E.
Dumas, C. R. Mayer, P. Mialane, Chem. Rev. 2010, 110, 6009–6048; c) A.
Proust, B. Matt, R. Villaneau, G. Guillemot, P. Gouzerh, G. Izzet, Chem.
Soc. Rev. 2012, 41, 7605–7622; d) D.-L. Long, R. Tsunashima, L. Cronin,
Angew. Chem. Int. Ed. 2010, 49, 1736–1758; Angew. Chem. 2010, 122,
1780–1803; e) S. Berardi, M. Carraro, A. Sartorel, G. Modugno, M. Bon-
chio, Isr. J. Chem. 2011, 51, 259–274.
[3] a) B. Hasenknopf, Front. Biosci. 2005, 10, 275–287; b) for recent exam-
ples see: C. Yvon, A. J. Surman, M. Hutin, J. Alex, B. O. Smith, D.-L. Long,
L. Cronin, Angew. Chem. Int. Ed. 2014, 53, 3336–3341; Angew. Chem.
2014, 126, 3404–3409; c) K. Stroobants, V. Goovaerts, G. Absillis, G.
Bruylants, E. Moelants, P. Proost, T. N. Parac-Vogt, Chem. Eur. J. 2014, 20,
9567–9577.
[4] a) N. Mizuno, K. Yamaguchi, K. Kamata, Coord. Chem. Rev. 2005, 249,
1944–1956; b) C. L. Hill, J. Mol. Catal. A 2007, 262, 1–2; c) I. V. Kozhevni-
kov in NATO Science Series, Vol. 98: Polyoxometalate Molecular Science
(Eds.: J. J. Borras-Almenar, E. Coronado, A. Müller, M. T. Pope), Kluwer,
Dordrecht, 2003, pp. 351–380; d) T. Ueda, H. Kotsuki, Heterocycles
2008, 76, 73–97; e) M. Carraro, A. Sartorel, M. Ibrahim, N. Nsouli, C.
Jahier, S. Nlate, U. Kortz, M. Bonchio in Innovative Catalysis in Organic
Synthesis: Oxidation, Hydrogenation, and CÀX Bond Forming Reactions
(Ed.: P. G. Andersson), Wiley-VCH, Weinheim, 2012, pp. 1–25; f) S.-S.
Wang, G.-Y. Yang, Chem. Rev. 2015, 115, 4893–4962.
Experimental Section
Typical experimental procedure: Catalyst 3a (60 mg, 5 mol%) and
DNBA (5 mol%) were stirred in CH2Cl2 (0.4 mL) for 5 min, followed
by addition of crotonaldehyde (0.19 mmol, 16 mL) then cyclopenta-
diene (0.58 mmol, 49 mL). After 2 days of stirring, the POM was pre-
cipitated upon addition of EtOH/Et2O (0.4 mL/8 mL) and removed
by centrifugation and filtration. The filtrate was concentrated and
purified by flash chromatography on a silica column to furnish the
[5] a) B. Hasenknopf, K. Micoine, E. Lacôte, S. Thorimbert, M. Malacria, R.
Thouvenot, Eur. J. Inorg. Chem. 2008, 5001–5013; b) D. L. Du, L.-K. Yan,
Z.-M. Su, S.-L. Li, Y.-Q. Lan, E.-B. Wang, Coord. Chem. Rev. 2013, 257,
Chem. Eur. J. 2015, 21, 16512 – 16516
www.chemeurj.org
16515
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
702–717; c) W.-L. Chen, H.-Q. Tan, E.-B. Wang, J. Coord. Chem. 2012, 65,
1–18.
[6] J. A. Switzer, H. M. Kothari, P. Poizot, S. Nakanishi, E. W. Bohannan,
Nature 2003, 425, 490–493.
Chem. Eur. J. 2014, 20, 16074–16077; b) For some early Pd-catalyzed
asymmetric allylation of pronucleophiles see R. Kuwano, Y. Ito, J. Am.
Chem. Soc. 1999, 121, 3236–3237; c) B. M. Trost, J. Xie, J. D. Sieber, J.
Am. Chem. Soc. 2011, 133, 20611–20622.
[7] T. Mallat, E. Orglmeister, A. Baiker, Chem. Rev. 2007, 107, 4863–4890.
[8] A. Gonzµlez-Campo, D. B. Amabilino, Top. Curr. Chem. 2013, 320-331,
109–156.
[14] a) K. A. Ahrendt, C. J. Borths, D. W. C. MacMillan, J. Am. Chem. Soc. 2000,
122, 4243–4244; b) J. F. Austin, S.-G. Kim, C. J. Sinz, W. J. Xiao, D. W. C.
MacMillan, Proc. Natl. Acad. Sci. USA 2004, 101, 5482–5487; c) A. B.
Northrup, D. W. C. MacMillan, J. Am. Chem. Soc. 2002, 124, 2458–2460.
[15] a) K. Micoine, B. Hasenknopf, S. Thorimbert, E. Lacôte, M. Malacria,
Angew. Chem. Int. Ed. 2009, 48, 3466–3468; Angew. Chem. 2009, 121,
3518–3520; b) C. Boglio, K. Micoine, E. Derat, R. Thouvenot, B. Hasen-
knopf, S. Thorimbert, E. Lacôte, M. Malacria, J. Am. Chem. Soc. 2008,
130, 4553–4561; c) N. DuprØ, C. Brazel, L. Fensterbank, M. Malacria, S.
Thorimbert, B. Hasenknopf, E. Lacôte, Chem. Eur. J. 2012, 18, 12962–
12965; d) G. Lenoble, B, Hasenknopf, R. Thouvenot, J. Am. Chem. Soc.
2006, 128, 5735–5744; e) C. Boglio, B. Hasenknopf, G. Lenoble, P. RØmy,
P. Gouzerh, S. Thorimbert, E. Lacôte, M. Malacria, R. Thouvenot, Chem.
Eur. J. 2008, 14, 1532–1540; f) Y.-M. Sang, L.-K. Yan, J.-P. Wang, Z.-M. Su,
J. Phys. Chem. A 2012, 116, 4152–4158; g) the representation of a1-
P2W17O61 is given for illustration of the overall structure; the (À) enan-
tiomer might correspond to the mirror image of the drawing.
[16] a) C. S. Pecinovsky, G. D. Nicodemus, D. L. Gin, Chem. Mater. 2005, 17,
4889–4891; b) D. L. Gin, X. Lu, P. R. Nemade, C. S. Pecinovsky, Y. Xu, M.
Zhou, Adv. Funct. Mater. 2006, 16, 865–878; c) Y. Zhang, L. Zhao, S. S.
Lee, J. Y. Ying, Adv. Synth. Catal. 2006, 348, 2027–2032; d) F. Freire, S. H.
Gellman, J. Am. Chem. Soc. 2009, 131, 7970–7972.
[17] a) J. B. Brazier, K. M. Jones, J. A. Platts, N. C. O. Tomkinson, Angew. Chem.
Int. Ed. 2011, 50, 1613–1616; Angew. Chem. 2011, 123, 1651–1654; b) S.
Guizzetti, M. Benaglia, J. S. Siegel, Chem. Commun. 2012, 48, 3188–
3190; c) A. Puglisi, M. Benaglia, R. Annunziata, V. Chiroli, R. Porta, A. Ger-
visini, J. Org. Chem. 2013, 78, 11326–11334; d) I. Atodiresei, C. Vila, M.
Rueping, ACS Catal. 2015, 5, 1972–1985.
[18] T. J. Peelen, Y. Chi, S. H. Gellman, J. Am. Chem. Soc. 2005, 127, 11598–
11599.
[19] C. Jahier, S. Nlate, Eur. J. Inorg. Chem. 2012, 833–840.
[9] a) M. Sadakane, M. H. Dickman, M. T. Pope, Inorg. Chem. 2001, 40,
2715–2719; b) V. Soghomonian, Q. Chen, R. C. Haushalter, J. Zubieta,
C. J. O’Connor, Science 1993, 259, 1596–1599; c) H. Y. An, D. R. Xiao,
E. B. Wang, Y. G. Li, L. Xu, New J. Chem. 2005, 29, 667–672; d) Y. Hou, X.
Fang, C. L. Hill, Chem. Eur. J. 2007, 13, 9442–9447; e) Y. Q. Lan, S. L. Li,
X. L. Wang, K. Z. Shao, D. Y. Du, Z. M. Su, E. B. Wang, Chem. Eur. J. 2008,
14, 9999–10006; f) H.-Y. An, E.-B. Wang, D.-R. Xiao, Y.-G. Li, Z.-M. Su, L.
Xu, Angew. Chem. Int. Ed. 2006, 45, 904–908; Angew. Chem. 2006, 118,
918–922; g) J. Zhang, J. Hao, Y. Wei, F. Xiao, P. Yin, L. Wang, J. Am.
Chem. Soc. 2010, 132, 14–15; h) L. Shi, B. Li, L. Wu, Chem. Commun.
2015, 51, 172–175.
[10] a) M. Inoue, T. Yamase, Bull. Chem. Soc. Jpn. 1995, 68, 3055–3063;
b) F. B. Xin, M. T. Pope, J. Am. Chem. Soc. 1996, 118, 7731–7736; c) M.
Inoue, T. Yamase, Bull. Chem. Soc. Jpn. 1996, 69, 2863–2868; d) D. L.
Long, P. Kçgerler, L. J. Farrugia, L. Cronin, Chem. Asian J. 2006, 1, 352–
357; e) U. Kortz, M. G. Savelieff, F. Y. A. Ghali, L. M. Khalil, S. A. Maalouf,
D. I. Sinno, Angew. Chem. Int. Ed. 2002, 41, 4070–4073; Angew. Chem.
2002, 114, 4246–4249; f) X. K. Fang, T. M. Anderson, C. L. Hill, Angew.
Chem. Int. Ed. 2005, 44, 3540–3544; Angew. Chem. 2005, 117, 3606–
3610; g) X. K. Fang, T. M. Anderson, Y. Hou, C. L. Hill, Chem. Commun.
2005, 5044–5046; h) C. Jahier, M. Cantuel, N. D. McClenaghan, T. Buffe-
teau, D. Cavagnat, F. Agbossou, M. Carraro, M. Bonchio, S. Nlate, Chem.
Eur. J. 2009, 15, 8703–8708; i) W. Adam, P. L. Alsters, R. Neumann, C. R.
Saha-Moeller, D. Seebach, R. Zhang, Org. Lett. 2003, 5, 725–728; j) S. Be-
rardi, M. Carraro, M. Iglesias, A. Sartorel, G. Scorrano, M. Albrecht, M.
Bonchio, Chem. Eur. J. 2010, 16, 10662–10666.
[11] a) S. Zh. Luo, J. Y. Li, H. Xu, L. Zhang, J.-P. Cheng, Org. Lett. 2007, 9,
3675–3678; b) J. Y. Li, X. Li, P. X. Zhou, L. Zhang, S. Zh. Luo, J.-P. Cheng,
Eur. J. Org. Chem. 2009, 4486–4493; c) Q. Han, C. He, M. Zhao, B. Qi, J.
Niu, C. Duan, J. Am. Chem. Soc. 2013, 135, 10186–10189; d) Y. Wang, H.
Li, W. Qi, Y. Yang, Y. Yan, B. Li, L. Wu, J. Mater. Chem. 2012, 22, 9181–
9188; e) S. Nlate, C. Jahier, Eur. J. Inorg. Chem. 2013, 1606–1619; f) L.
Shi, Y. Wang, B. Li, L. Wu, Dalton Trans. 2014, 43, 9177–9188.
[12] a) M. Mahlau, B. List, Angew. Chem. Int. Ed. 2013, 52, 518–533; Angew.
Chem. 2013, 125, 540–556; b) K. Brak, E. N. Jacobsen, Angew. Chem. Int.
Ed. 2013, 52, 534–561; Angew. Chem. 2013, 125, 558–588; c) M. Raynal,
P. Ballester, A. Vidal-Ferran, P. W. N. M. van Leeuwen, Chem. Soc. Rev.
2014, 43, 1660–1733; d) L. Gong, L.-A. Chen, E. Meggers, Angew. Chem.
Int. Ed. 2014, 53, 10868–10874; Angew. Chem. 2014, 126, 11046–11053.
[13] a) Chiral hybrid POM–DMAP for acylation delivering 8% ee. See: C.
Brazel, N. DuprØ, M. Malacria, B. Hasenknopf, E. Lacôte, S. Thorimbert,
[20] a) Y. Hayashi, S. Samanta, H. Gotoh, H. Ishikawa, Angew. Chem. Int. Ed.
2008, 47, 6634–6637; Angew. Chem. 2008, 120, 6736–6739; b) P. Mel-
chiorre, M. Marigo, A. Carlone, G. Bartoli, Angew. Chem. Int. Ed. 2008, 47,
6138–6171; Angew. Chem. 2008, 120, 6232–6265.
[21] a) T. Kano, Y. Tanaka, K. Maruoka, Chem. Asian J. 2007, 2, 1161–1165;
b) R. Gordillo, K. N. Houk, J. Am. Chem. Soc. 2006, 128, 3543–3553.
[22] O. V. Maltsev, A. O. Chizhov, S. G. Zlotin, Chem. Eur. J. 2011, 17, 6109–
6117.
Received: July 20, 2015
Published online on September 25, 2015
Chem. Eur. J. 2015, 21, 16512 – 16516
www.chemeurj.org
16516
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