Olefin epoxidation by a (salen)Mn(III) catalyst covalently grafted on glass beads

Article abstract of DOI:10.1039/c4cy00831f

The asymmetric epoxidation of unfunctionalized prochiral olefins catalyzed by chiral (salen)Mn(III) complexes is an important viable route to obtain chiral epoxides. Recently we proposed a monolayer of (salen)Mn(III) molecules on functionalized flat silica substrates as an active heterogeneous catalyst for enantioselective epoxidation of 6-cyano-2,2-dimethylchromene with huge turnover values. In the present study we synthesized a monolayer of modified (salen)Mn(III) molecules on previously functionalized glass bead substrates in order to increase the active surface area. The catalyst activity of this system was tested with different olefins and in some cases we observed enantioselectivity higher than in solution. The system was reused up to seven times with no variation in performance.

Full text of DOI:10.1039/c4cy00831f

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Olefin epoxidation by a (salen)Mn(III) catalyst
covalently grafted on glass beads†
Cite this: DOI: 10.1039/c4cy00831f
Giuseppe Trusso Sfrazzetto,‡a Salvatrice Millesi,‡a Andrea Pappalardo,a
Rosa Maria Toscano,a Francesco P. Ballistreri,a Gaetano A. Tomasellia
ab
*
and Antonino Gulino
The asymmetric epoxidation of unfunctionalized prochiral olefins catalyzed by chiral (salen)Mn(III)
complexes is an important viable route to obtain chiral epoxides. Recently we proposed a monolayer of
(salen)Mn(III) molecules on functionalized flat silica substrates as an active heterogeneous catalyst for
enantioselective epoxidation of 6-cyano-2,2-dimethylchromene with huge turnover values. In the present
study we synthesized a monolayer of modified (salen)Mn(III) molecules on previously functionalized glass
bead substrates in order to increase the active surface area. The catalyst activity of this system was tested
with different olefins and in some cases we observed enantioselectivity higher than in solution. The system
was reused up to seven times with no variation in performance.
Received 27th June 2014,
Accepted 22nd July 2014
DOI: 10.1039/c4cy00831f
www.rsc.org/catalysis
this procedure.10,22–24 Very recently, Zhang and Wang
reported on the asymmetric epoxidation of cis/trans-β-methyl-
Introduction
Recently, we reported on a robust prototype (salen)Mn(III)-based
monolayer,1 covalently bound to flat quartz substrates,2
which resulted in a good chiral catalyst for asymmetric olefin
epoxidation with huge turnover values.3 Moreover, we also
reported experimental photoelectron evidence of the forma-
tion of the surface-confined OMnV(salen) oxene active
species.1
Olefin epoxidation reactions are of much importance since
the obtained chiral epoxides contain two new stereocentres
and can be easily transformed into a large variety of com-
pounds active in many other technological fields.4–14
Homogeneous (salen)Mn(III) complexes are well suited to
this purpose and high enantioselectivity in the asymmetric
epoxidation of unfunctionalised olefins has been reported.15
In this context, much effort has been dedicated to hetero-
genize the Jacobsen catalyst throughout anchoring chiral
(salen)Mn(III) complexes onto solid surfaces in order to
enhance their stability, activity, selectivity, recovery and
recycle.15–20 However, the separation and recycling of the
expensive chiral catalyst represents the main drawback of
styrene using two Mn(salen) catalysts immobilized inside
nanopores and the rigidity of the substrate–Mn complex
linkage was found to be a key factor affecting catalytic per-
formance.25 In fact, they concluded that for immobilised
Mn(salen) catalysts, a rigid linkage connecting active centres
to the support is essential to obtain activity and enantio-
selectivity as high as those obtained in homogeneous
systems. It emerges that the immobilisation strategy plays a
fundamental role in this field.26
As part of our on-going study in this field we now devel-
oped a new (salen)Mn(III)-based monolayer that was grafted
on the surface of some glass beads and tested its activity
towards four selected alkenes (6-cyano-2,2-dimethylchromene,
cis-β-ethylstyrene, 1,2-dihydronaphthalene and indene). We
found that the total conversion of alkenes occurred in short
times. Enantiomeric excess values were similar or better
than those obtained in homogeneous media and up to 90%,
thus demonstrating the efficiency of the new (salen)Mn(III)-
based monolayer grafted on glass beads for asymmetric
epoxidation.
a Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6,
95125 Catania, Italy. E-mail: agulino@unict.it; Fax: +39 095 580138;
Tel: +39 095 7385067
b I.N.S.T.M. UdR of Catania, Viale A. Doria 6, 95125 Catania, Italy
† Electronic supplementary information (ESI) available: Synthesis procedures,
1H and 13C NMR, APT, gCOSY, results of the epoxidation reactions using
catalyst 5 in solution and AFM of glass beads (Fig. S1–S7, Table S1) are reported
in the supporting information. See DOI: 10.1039/c4cy00831f
‡ Giuseppe Trusso Sfrazzetto and Salvatrice Millesi equally contributed to
this work.
Experimental details
The detailed synthesis of the catalysts (Scheme 1) used in
this work has been reported in the ESI.† NMR experiments
were carried out at 27 °C on a Varian UNITY Inova 500 MHz
spectrometer (1H at 499.88 MHz, 13C NMR at 125.7 MHz)
equipped with a pulsed field gradient module (Z axis) and
a tuneable 5 mm Varian inverse detection probe (ID-PFG).
1H NMR (Fig. S1–S4†) peak assignments follow from
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X-ray photoelectron spectroscopy (XPS) spectra were
obtained with a PHI 5600 Multi Technique System and the
resolution, procedures for calibration, satellite subtraction
and background removal were already reported.31,32
UV-vis measurements were carried out on a Jasco UV-vis
V-650 spectrometer and the spectra were recorded with a
0.2 nm resolution at room temperature.
The glass bead surface morphology was studied by atomic
force microscopy (AFM) in an instrument manufactured by
NT-MDT. The noise level before and after each measurement
was 0.01 nm. AFM characterisation was performed in high-
amplitude tapping mode (Fig. S7).†
Results and discussion
Scheme 1 shows the synthesis strategy for the Mn(III)-catalyst (1).
3-tert-Butyl-2-hydroxybenzaldehyde was chloromethylated in
the 5-position by treatment with aqueous formaldehyde and
hydrochloric acid to obtain 2. Then N-hexanol-phthalimide
was linked to 2 under alkaline conditions leading to 3.
The asymmetric salen ligand 4 was obtained by the reac-
tion of (1R,2R)-1,2-diphenylethylenediamine,3,5-di-tert-
butylsalicylaldehyde hydrochloride and aldehyde 3 in the
presence of triethylamine.33 The Mn-catalyst 5 was isolated
by treatment of ligand 4 with manganese(III) acetate in etha-
nol. Finally, deprotection of the amino group in 5 by reaction
with hydrazine monohydrate gave Mn catalyst 1. All of the
details regarding the synthetic reactions have been reported
in the ESI (Fig. S1–S6). At variance with the (salen)Mn(III) that
we already used on flat quartz substrates,1 this system is
asymmetric since it has only one pendant amino group for
surface grafting. This method should allow an increased
molecular density on the substrate surface since this system
has a higher degree of freedom upon grafting.
The (salen)Mn(III)-based monolayer Mn_1_MGB was
synthesized by covalent grafting of 1 to glass beads that were
previously silylated (Scheme 2).2
Silylation was performed under N2 with trichloro[4-
(chloromethyl)phenyl]silane, a bi-functional coupling agent
that binds both the substrate and the (salen)Mn(III).2 The
grafted molecules were found to be insoluble in toluene,
MeCN, THF, and EtOH.
Scheme 1 Synthetic pathway for the protected 5 and the unprotected
1. Reagents and conditions: (a) formaldehyde (aq. 37%), HCl, 90 °C,
90%; (b) N-hexanol-phthalimide, K2CO3, CH3CN, 70 °C, 18 h, 40%;
(c)(1R,2R)-1,2-diphenylethylenediamine,3,5-di-tert-butylsalicylaldehyde
hydrochloride, Et3N, EtOH, 80%; (d) Mn(AcO)3·2H2O, r.t., 24 h, 97%;
(e) hydrazine monohydrate, EtOH, 60 °C, 10 min., 80%.
2D-COSY (Fig. S5†) experiments. Gas chromatographic
analyses of the reaction mixtures were carried out on a gas
chromatograph equipped with a flame ionization detector
and that has programming capability.
ESI mass spectra (Fig. S6†) were acquired using ES-MS
Thermo-Finnigan LCQ-DECA in MeOH (positive ion mode).
Glass beads of 3 mm diameter were first cleaned with
“piranha” solution (conc H2SO4 : 35% H2O2 70 : 30 v/v) at
90 °C for 60 min and then cooled to room temperature. The
piranha solution is very dangerous and needs to be handled
with caution! Glass beads were then rinsed (ten times) with
double distilled water and kept in a solution containing
H2O, H2O2 (30%) and NH3 (28%) in a 5 : 1 : 1 volume ratio,
respectively, at room temperature for 1 h.27–29 Repeated washes
with double distilled water, followed by drying under a
vacuum, were carried out just prior to coupling agent (CA)
deposition. All successive substrate treatments were per-
formed in a glove box under a N2 atmosphere (1 ppm O2,
1 ppm H2O). Freshly cleaned glass beads were immersed at
room temperature for 20 min in an n-pentane (0.5 : 100 v/v)
solution of trichloro[4-(chloromethyl)phenyl]silane to afford the
siloxane-coated substrates.27–30 These were washed (ten times)
with n-pentane, sonicated in n-pentane for 10 min to remove
Fig. 1 shows the absorption spectra of a toluene solution
of 1 (black line) at 5.7 × 10−6 M and of a representative
Mn_1_MGB (red line).
The solution UV-vis spectrum shows two bands: the first
centred at 296.4 with two weak bands at 286.2 and 306.4 nm
and the second at 374.2 nm with a shoulder at 393.0 nm.
These two bands are consistent with the π → π* and n → π*
transitions of 1, respectively.1 The Mn_1_MGB UV-vis spec-
trum closely resembles that of the solution with two features
at 287.4 and 302.8 nm and another band at 366.1 nm with
a shoulder at 388.6 nm. The calculated molecular surface
coverage, dsurf = Aε−1 (number of molecules of 1 cm−2 in
any physisorbed CA, immersed in a freshly prepared 9.5 × 10−4
M
toluene solution of (salen)Mn(III) (1) and kept at 90 °C for 72 h
while stirring. The (salen)Mn(III) monolayers on glass beads thus
formed were cooled to room temperature and then sonicated
(two times) for 10 min with toluene to remove any residual
unreacted Mn complex.
Mn_1_MGB) is 7.8 × 1013 molecules cm−2 34
This value is
.
almost two times higher than that already reported for its
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Fig. 2 Set-up of Mn_1_MGB for XPS measurements.
Scheme 2 Covalent grafting of 1 to silylated glass beads. Reagents
and conditions: glass silylation: in a glove box under a N2 atmosphere,
0.5 : 100 v/v trichloro[4-(chloromethyl)phenyl]silane/n-pentane, 25 °C,
25′; catalyst grafting: a 9.5 × 10−4 M toluene solution of (salen)Mn(III),
95 °C, 72 h.
Fig. 3 Mg Kα excited XPS of Mn_1_MGB in the Mn 2p binding energy
region.
Fig. 4 Mg Kα excited XPS of Mn_1_MGB in the N 1s binding energy
region.
Fig. 1 UV-vis spectra of a 5.7 × 10−6 M toluene solution (black line)
of 1 and of a representative Mn_1_MGB (red line).
complex shows a rather symmetric N 1s signal at 400.0 eV as
a consequence of some electronic level reorganization of the
imine functionalities upon Mn(III) complexation.1
On the basis of XPS atomic concentration analysis we
estimated a surface coverage of 5.7 × 1013 and this value is
rather close to that obtained from UV-vis measurements
(vide supra).36–38 Therefore we estimated the molecular size
of 1 on the surface using MM+ calculation (HyperChem 7.5)
and Fig. 5 shows the geometric arrangement.39
parent system with two pendant groups and confirms the
objective of this new synthetic design.1 The resulting foot-
print is 128 Å2 per molecule.2
Fig. 2 shows the set-up of Mn_1_MGB on the sample
holder for XPS measurements.
The glass beads were stacked with double-sided Scotch
tape appropriate for XPS. A representative XPS of Mn_1_MGB
in the Mn 2p energy region is reported in Fig. 3.
The two spin–orbit components appear at 641.8 and 653.7 eV
and partially overlap with the high energy shake-up satellites
typical of Mn(III) species.1,35
Fig. 4 shows the XPS of Mn_1_MGB in the N 1s binding
energy region. On the basis of a localized bonding scheme,
(salen)Mn(III) shows two imine and one amine nitrogens in
the formula unit. The photoelectron spectrum of the grafted
On the basis of these calculations the occupied area on
the substrate is 134.7 Å2 per molecule. This value is strongly
reminiscent of that obtained from UV-vis measurements and
confirms the high density of 1 on the bead surfaces.
In order to test the activity of Mn_1_MGB as a catalyst in
epoxidation reactions the following four alkenes, 6-cyano-2,2-
dimethylchromene, cis-β-ethylstyrene, 1,2-dihydronaphthalene
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washed with water and dichloromethane and then reused for
the next cycle. Fig. 6 shows that both enantiomeric excess
values and %conversion remained almost unaltered thus
confirming the high stability of the present heterogeneous
catalyst.
Table 2 shows the epoxidation data obtained using cis-β-
ethylstyrene. Reaction times are similar to those previously
observed for 6-cyano-2,2-dimethylchromene, and also in this
case the detected enantiomeric excess values are higher
with respect to those observed in solution (Table S1).†
However, an inversion of the cis/trans ratio was observed:
in solution, catalyst 5 leads mainly to the cis isomer
(cis/trans = 5), while Mn_1_MGB predominantly generates the
trans isomer (90%).
Fig. 5 MM+ optimization of the arrangement of 1.
and indene, have been selected. Table 1 lists the results
obtained for the epoxidation of 6-cyano-2,2-dimethylchromene
into 3,4-epoxy-6-cyano-2,2-dimethylchromene. Results indicate
that the reaction time for total conversion decreases as the
number of glass beads used in the reaction medium increases.
Enantiomeric excess values (85–91%) are slightly higher than
the corresponding ones (80%) obtained in solution (Table S1†).
As expected, TON and TOF values are in the range of 104−105
and 102−103, respectively. Table 1 shows that the addition of
4-phenylpyridine-N-oxide (PPNO) does not significantly influ-
ence the e.e. and conv. values. In order to check on the robust-
ness of Mn_1_MGB the above epoxidation process was
repeated 7 times for 24 h. After each cycle, Mn_1_MGB was
Fig. 6 Variations in e.e. and conv. values after reusing 60 spheres
(beads) in the epoxidation of 6-cyano-2,2-dimethylchromene for 24 h
with Mn_1_MGB.
Table 1 Results of the epoxidation of 6-cyano-2,2-dimethylchromene into 3,4-epoxy-6-cyano-2,2,-dimethylchromene using Mn_1_MGBa
Number of glass bead catalyst
10
Reaction time/h
e.e.b
%
Conv.b %
TONc
TOFd (h−1
)
7
24
48
72
96
130
7
24
48
72
96
7
24
48
72
7
24
48
72
88
86
85
87
85
86
89
88
87
88
87
87
89
87
85
90
91
91
90
5
15
35
55
75
100
12
25
50
75
100
30
45
77
100
29
47
78
100
6202
886
775
904
948
969
982
719
437
437
437
437
883
386
331
286
854
404
335
286
18 606
43 415
68 224
93 032
124 043
5036
10 492
20 984
31 477
41 969
6183
30
60
9275
15 870
20 611
5977
9687
16 076
20 611
60 + PPNO
a
In all of these experiments 0.081 mmol of 6-cyano-2,2-dimethylchromene was dissolved in 1 mL of CH2Cl2; NaClO was 0.81 mmol and the
b
total volume of the reacting solutions buffered with 1 mL of 0.05 M Na2HPO4 at pH = 11.2 was 3 mL. Determined by GC with a dimethyl-
c
pentyl-beta (DIMEPEBETA-086) chiral column (25 m × 0.25 mm ID, 0.25 μm film). TON = mmol of the overall products/mmol of the catalyst.
d
TOF = TON/reaction time (h).
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Table 2 Results of the epoxidation of cis-β-ethylstyrene at 25 °C using Mn_1_MGBa
Number of glass bead catalyst
10
Reaction time/h
e.e.b cis %
e.e.b trans %
Conv.b %
TONc
TOFd (h−1
)
7
24
48
72
96
7
24
48
72
7
24
48
72
7
24
48
72
80
80
83
84
84
80
81
83
84
72
81
85
85
89
88
88
89
89
90
89
90
91
88
90
91
88
88
86
88
87
91
92
91
91
17
29
56
73
100
29
54
89
100
40
70
94
100
49
77
93
20 958
35 556
69 275
91 095
124 043
12 106
22 798
37 454
41 969
8310
14 433
19 355
20 611
10 051
15 951
19 245
20 611
2994
1482
1443
1265
1292
1729
950
780
583
1187
601
403
286
1436
665
401
286
30
60
60 + PPNO
100
a
In all of these experiments 0.081 mmol of cis-β-ethylstyrene was dissolved in 1 mL of CH2Cl2; NaClO was 0.81 mmol and the total volume of
b
the reacting solutions buffered with 1 mL of 0.05 M Na2HPO4 at pH = 11.2 was 3 mL. Determined by GC with a DiAcTBuSiliBETA-ov-1701
chiral column (25 m × 0.25 mm ID, 0.25 μm film), [trans]/[cis] = 7. TON = mmol of the overall products/mmol of the catalyst. TOF =
c
d
TON/reaction time (h).
Very recently Zhang and Wang reported that for immo-
bilized Mn(salen) catalysts, a rigid linkage connecting active
centres to the support is essential to obtain activity and
enantioselectivity as high as that obtained in homogeneous
systems.25 In fact, the immobilised catalyst with a flexible
linkage gave lower chemical selectivity, enantioselectivity
and inverted cis/trans ratio compared to the homogeneous
Jacobsen catalyst and to the immobilized catalyst with a rigid
linkage. This is possible because of the rotation of the C–C
bond in radical intermediates that affects the cis/trans ratio.
In our case as well as in Zhang and Wang's case, the linkages
are connected to the 6-position in the salen ligand, which
is far from the Mn(III) atoms. Moreover, the only difference
between the catalyst (5) we used for homogeneous solution
reactions and the catalyst (1) anchored onto the glass beads
(Mn_1_MGB) is the naphthylamide group that protects
the amino group and this is unlikely to result in different
chemical selectivities to epoxides, cis/trans ratio and e.e.
values. Therefore, the inversion of the cis/trans ratio we
observed from homogeneous to heterogeneous medium must
be due to the rigid silane linker used to functionalize the
glass bead surface for the successive grafting of 1.25 Notably,
we always observed a better e.e. value with Mn_1_MGB than
in solution.
Similar epoxidation reactions have been performed with
Mn_1_MGB using 1,2-dihydronaphthalene and indene and
Tables 3 and 4 show relevant results, respectively.
Notably, reaction times for the total conversion of 1,2-
dihydronaphthalene and indene are shorter than those observed
for cis-β-ethylstyrene and 6-cyano-2,2-dimethylchromene.
Table 3 Results of the epoxidation of 1,2-dihydronaphthalene using Mn_1_MGBa
Number of glass bead catalyst
10
Reaction time/h
e.e.b
%
Conv.b %
TONc
TOFd (h−1
)
7
24
48
72
7
24
48
72
7
24
48
7
24
48
80
78
80
80
81
80
79
80
79
81
80
80
79
81
23
49
77
100
27
55
84
100
31
84
100
38
33 108
61 073
103 718
124 043
9640
20 664
32 209
41 969
6363
17 293
20 611
7790
19 222
20 611
4730
2545
2161
1723
1377
861
671
583
909
721
30
60
429
1113
801
60 + PPNO
93
100
429
a
In all of these experiments 0.081 mmol of 1,2-dihydronaphthalene was dissolved in 1 mL of CH2Cl2; NaClO was 0.81 mmol and the total
b
volume of the reacting solutions buffered with 1 mL of 0.05 M Na2HPO4 cat pH 11.2 was 3 mL. Determined by GC with a dimethyl-pentyl-beta
d
(DMePeBETACDX) chiral column (25 m × 0.25 mm ID, 0.25 μm film). TON = mmol of the overall products/mmol of the catalyst. TOF =
TON/reaction time (h).
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Table 4 Results of the epoxidation of indene using Mn_1_MGBa
Number of glass bead catalyst
10
Reaction time/h
e.e.b
%
Conv.b %
TONc
TOFd (h−1
)
7
24
48
7
24
48
7
24
48
7
80
78
80
78
81
80
75
78
78
77
78
28
72
100
31
88
100
24
91
100
29
34 657
89 302
124 043
13 105
36 976
41 969
4852
18 758
20 611
6067
4951
3721
2584
1872
1541
874
693
782
429
867
30
60
60 + PPNO
24
97
20 004
833
a
In all of these experiments 0.081 mmol of indene was dissolved in 1 mL of CH2Cl2; NaClO was 0.81 mmol and the total volume of the
b
reacting solutions buffered with 1 mL of 0.05 M Na2HPO4 at pH 11.2 was 3 mL. Determined by GC with a dimethyl-pentyl-beta
(DMePeBETACDX) chiral column (25 m × 0.25 mm ID, 0.25 μm film). TON = mmol of the overall products/mmol of the catalyst. TOF =
c
d
TON/reaction time (h).
In fact, the total conversion of 1,2-dihydronaphthalene was
achieved in 72 h using 10 and 30 spheres and in 48 h using
Conclusions
60 spheres. Indene was completely converted to the respec-
tive epoxides in 48 h using 30 spheres. The observed differ-
ent reaction times for the total conversion of the above
alkenes can find a rationale on the basis of the different
geometric structures of the substrates. Both indene and
1,2-dihydronaphthalene have planar structures, while cis-β-
ethylstyrene and 6-cyano-2,2-dimethylchromene are slightly
more bulky, due to the freedom in the γ-position in cis-β-
ethylstyrene and the two methyl groups in 6-cyano-2,2-
dimethylchromene. Planar alkenes seem more suitable
than bulky substrates to interact with the surface-confined
Mn_1_MGB (Fig. 5). In these cases enantiomeric excess values
are similar to our data obtained in solution (Table S1†) and
similar to recently reported results.40–45
An interesting observation is the high present value of
the turnover frequencies under heterogeneous conditions
(1.24 × 105 using 10 spheres) with respect to the solution (20) after
total olefin transformation.20,21,41 Obviously, the highest TON
values have been observed for the lowest number of beads
used in the reaction media (Tables 1–4). The TOF parameter41
displays a similar trend on passing from homogeneous (10)
to heterogeneous (4951 highest TOF for indene epoxidation
after 7 h reaction) conditions. Evidently, these large TOF values
(Tables 1–4) are due to the covalent nature of the active catalyst
that precludes any leaching as measured in the reacting solu-
tion by inductively coupled plasma mass spectrometry.
A novel (salen)Mn(III) robust monolayer was covalently
fabricated on glass bead substrates and resulted in an active
catalyst for asymmetric epoxidation of four different alkenes.
High enantioselectivity and high TON and TOF values have
been observed. No observable leaching of the catalyst as
well as no performance variation was noted after 7 reaction
cycles.
According to the studies of Zhang25 and Tu47 the rigid silane
group used to graft the present (salen)Mn(III) complex to the
glass bead surface was advantageous to attain high activity
and e.e. values. Our present study demonstrates the possi-
bility to heterogenize the (salen)Mn(III) catalyst by improving
the performance with respect to the solution reactions. In
fact, we believe that some enantiomeric excess values are
better than those obtained in homogeneous media because
the (salen)Mn(III) catalyst, supported on the present glass
beads, probably assumes the most appropriate conformation
to promote efficient enantioselective oxygen transfer towards
some substrates.
Acknowledgements
A G. thanks the MIUR (RINAME project) and the University
of Catania.
Notes and references
The present increase in enantioselectivity from solution
(80%, Table S1†) to heterogeneous (85–91%, Tables 1–2)
catalysis observed for the first two alkenes may be consistent
with the grafting geometry of this (salen)Mn(III) catalyst that
is always appropriate for epoxidation reaction. We already
noted that it is possible to assume that the OMnV group
of OMnV(salen) points outside from the monolayer.1,25
A similar conclusion has been arrived at by Milstein who
reported improved TON values in catalytic reactions using
molecular ordered Langmuir–Blodgett catalyst films.46
1 V. La Paglia Fragola, F. Lupo, A. Pappalardo, G. Trusso Sfrazzetto,
R. M. Toscano, F. P. Ballistreri, G. A. Tomaselli and A. Gulino,
J. Mater. Chem., 2012, 22, 20561–20565.
2 A. Gulino, T. Gupta, M. Altman, S. Lo Schiavo, P. G. Mineo,
I. L. Fragalà, G. Evmenenko, P. Dutta and M. E. van der Boom,
Chem. Commun., 2008, 2900–2902.
3 S. Liao and B. List, Angew. Chem., Int. Ed., 2010, 49, 628–631.
4 J. Lisowski, Inorg. Chem., 2011, 50, 5567–5576.
5 G. Haberhauer, Angew. Chem., Int. Ed., 2010, 49, 9286–9289.
Catal. Sci. Technol.
This journal is © The Royal Society of Chemistry 2014

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Paper
6 A. Gonzalez-Alvarez, I. Alfonso, J. Cano, P. Diaz, V. Gotor,
V. Gotor-Fernandez, E. Garcia-Espana, S. Garcia-Granda,
H. R. Jimenez and F. Lloret, Angew. Chem., Int. Ed., 2009, 48,
6055–6058.
7 E. N. Jacobsen, in Catalytic Asymmetric Synthesis, ed. I. Ojima,
VCH, Weinheim, 1993, ch. 4.2, pp. 159–202.
8 K. Matsumoto and T. Katsuki, in Catalytic Asymmetric
Synthesis, ed. I. Ojima, J. Wiley & Sons, Inc., New Jersey,
3rd edn, 2010, pp. 839–890.
9 A. F. Trindade, P. M. P. Gois and C. A. M. Afonso, Chem.
Rev., 2009, 109, 418–514.
28 A. Facchetti, L. Beverina, M. E. van der Boom, P. Dutta,
G. Evmenenko, A. D. Shukla, C. E. Stern, G. A. Pagani and
T. J. Marks, J. Am. Chem. Soc., 2006, 128, 2142.
29 (a) R. Yerushalmi, A. Scherz and M. E. van der Boom, J. Am.
Chem. Soc., 2004, 126, 2700; (b) C. Haensch, S. Hoeppener
and U. S. Schubert, Chem. Soc. Rev., 2010, 39, 2323; (c)
S. L. Brandow, M. S. Chen, C. S. Dulcey and W. J. Dressick,
Langmuir, 2008, 24, 3888.
30 A. Gulino, F. Lupo, G. G. Condorelli, A. Motta and I. Fragalà,
J. Mater. Chem., 2009, 19, 3507.
31 (a) A. Gulino, Anal. Bioanal. Chem., 2013, 405, 1479–1495;
(b) S. Millesi and A. Gulino, J. Mater. Chem. C, 2014, 2,
5924–5930.
10 T. P. Yoon and E. N. Jacobsen, Science, 2003, 299,
1691–1693.
11 I. W. E. E. Arends, Angew. Chem., Int. Ed., 2006, 45,
6250–6252.
12 D.-Y. Xie, S. B. Sharma, N. L. Paiva, D. Ferreira and R. A. Dixon,
Science, 2003, 299, 396–399.
13 Q.-H. Xia, H.-Q. Ge, C.-P. Ye, Z.-M. Liu and K.-X. Su, Chem.
Rev., 2005, 105, 1603–1662.
32 D. Briggs and J. T. Grant, Surface Analysis by Auger and
X-Ray Photoelectron Spectroscopy, IMP, Chichester, U.K.,
2003, p. 899.
33 (a) F. P. Ballistreri, G. G. Condorelli, I. Fragalà, A. Motta,
A. Pappalardo, G. A. Tomaselli, C. Tudisco and G. Trusso
Sfrazzetto, Eur. J. Inorg. Chem., 2011, 2124–2131; (b)
M. E. Amato, F. P. Ballistreri, S. D'Agata, A. Pappalardo,
G. A. Tomaselli, R. M. Toscano and G. Trusso Sfrazzetto,
Eur. J. Org. Chem., 2011, 5674–5680; (c) A. Pappalardo,
M. E. Amato, F. P. Ballistreri, G. A. Tomaselli, R. M. Toscano
and G. Trusso Sfrazzetto, J. Org. Chem., 2012, 77, 7684–7687;
(d) A. D'Urso, C. Tudisco, F. P. Ballistreri, G. G. Condorelli,
R. Randazzo, G. A. Tomaselli, R. M. Toscano, G. Trusso Sfrazzetto
and A. Pappalardo, Chem. Commun., 2014, 50, 4493–4496.
34 D. Q. Li, B. I. Swanson, J. M. Robinson and M. A. Hoffbauer,
J. Am. Chem. Soc., 1993, 115, 6975.
35 I. Bar-Nahum, H. Cohen and R. Neumann, Inorg. Chem.,
2003, 42, 3677–3684.
36 D. A. Cristaldi, A. Motta, S. Millesi, T. Gupta, M. Chhatwalb
and A. Gulino, J. Mater. Chem. C, 2013, 1, 4979–4984.
37 A. Gulino, F. Lupo, M. E. Fragalà and S. L. Schiavo, J. Phys.
Chem. C, 2009, 113, 13558.
38 F. Lupo, M. E. Fragalà, T. Gupta, A. Mamo, A. Aureliano,
M. Bettinelli, A. Speghini and A. Gulino, J. Phys. Chem. C,
2010, 114, 13459.
39 D. A. Cristaldi, I. Fragalà, A. Pappalardo, R. M. Toscano,
F. P. Ballistreri, G. A. Tomaselli and A. Gulino, J. Mater.
Chem., 2012, 22, 675–683.
40 D. Feichtinger and D. A. Plattner, Angew. Chem., Int. Ed.
Engl., 1997, 36, 1718–1719.
41 R. L. Paddock and S. T. Nguyen, J. Am. Chem. Soc., 2001,
123, 11498–11499.
14 M. L. Merlau, M. Del Pillar Mejia, S. T. Nguyen and
J. T. Hupp, Angew. Chem., Int. Ed., 2001, 40, 4239–4242.
15 (a) L. Canali and D. C. Sherrington, Chem. Soc. Rev., 1999, 28,
85–93; (b) C. E. Song and S. G. Lee, Chem. Rev., 2002, 102,
3495–3524; (c) E. M. McGarrigle and D. G. Gilheany, Chem.
Rev., 2005, 105, 1563–1602; (d) K. Yu, Z. Gu, R. Ji, L. L. Lou,
F. Ding, C. Zhang and S. X. Liu, J. Catal., 2007, 252, 312–320;
(e) R. Luo, R. Tan, Z. Peng, W. Zheng, Y. Kong and D. Yin,
J. Catal., 2012, 287, 170–177.
16 (a) P. McMorn and G. J. Hutchings, Chem. Soc. Rev., 2004,
33, 108–122; (b) C. Li, Catal. Rev.: Sci. Eng., 2004, 46, 419–492;
(c) A. Corma, Catal. Rev.: Sci. Eng., 2004, 46, 369–417; (d)
D. J. Macquarrie, Curr. Top. Catal., 2009, 52, 1640–1650.
17 J. M. Thomas and R. Raja, Acc. Chem. Res., 2008, 41,
708–720.
18 S. Bell, B. Wustenberg, S. Kaiser, F. Menges, T. Netscher and
A. Pfaltz, Science, 2006, 311, 642–644.
19 M. Wills, Science, 2006, 311, 619–620.
20 R. Raja, J. M. Thomas, M. D. Jones, B. F. G. Johnson and
D. E. W. Vaughan, J. Am. Chem. Soc., 2003, 125, 14982–14983.
21 C. Bianchini and P. Barbaro, Top. Catal., 2002, 19, 17–32.
22 J. M. Fraile, J. I. García, C. I. Herrerías, J. A. Mayoral and
E. Pires, Chem. Soc. Rev., 2009, 38, 695–706.
23 A. Corma and H. Garcia, Chem. Soc. Rev., 2008, 37, 2096–2126.
24 B. M. Rossbach, K. Leopold and R. Weberskirch, Angew.
Chem., Int. Ed., 2006, 45, 1309–1312.
25 H. Zhang, Y. Zou, Y.-M. Wang, Y. Shen and X. Zheng,
Chem. – Eur. J., 2014, 20, 7830–7841.
42 H. Zhang and C. Li, Tetrahedron, 2006, 62, 6640–6649.
43 Y. M. A. Yamada, S. M. Sarkar and Y. Uozumi, J. Am. Chem.
Soc., 2012, 134, 9285–9290.
44 Q.-Y. Bi, X.-L. Du, Y.-M. Liu, Y. Cao, H.-Y. He and K.-N. Fan,
J. Am. Chem. Soc., 2012, 134, 8926–8933.
45 T. Roy, R. I. Kureshy, N. H. Khan, S. H. R. Abdi, A. Sadhukhan
and H. C. Bajaj, Tetrahedron, 2012, 68, 6314–6322.
46 K. Töllner, R. Popovitz-Biro, M. Lahav and D. Milstein,
Science, 1997, 278, 2100–2102.
47 X. B. Tu, X. K. Fu, X. Y. Hu and Y. D. Li, Inorg. Chem.
Commun., 2010, 13, 404–407.
26 (a) F. Cozzi, Adv. Synth. Catal., 2006, 348, 1367–1390; (b)
C. Li, H. D. Zhang, D. M. Jiang and Q. H. Yang, Chem.
Commun., 2007, 547–558; (c) J. M. Thomas, R. Raja and
D. W. Lewis, Angew. Chem., 2005, 117, 6614–6641; (d)
J. M. Thomas, R. Raja and D. W. Lewis, Angew. Chem.,
Int. Ed., 2005, 44, 6456–6482.
27 L. Motiei, M. Altman, T. Gupta, F. Lupo, A. Gulino,
G. Evmenenko, P. Dutta and M. E. van der Boom, J. Am.
Chem. Soc., 2008, 130, 8913.
This journal is © The Royal Society of Chemistry 2014
Catal. Sci. Technol.