An efficient and selective epoxidation of olefins with novel methyltrioxorhenium/(fluorous ponytailed) 2,2′-bipyridine catalysts

Article abstract of DOI:10.1002/adsc.201000032

Novel complexes between methyltrioxorhenium (MTO) and bis(fluorous- ponytailed) 2,2′bipyridines (bpy-F_n) were synthesized and used for the oxidation of alkenes with hydrogen peroxide under fluorous catalysis. High conversions and yields of the corresponding epoxides were obtained.

Full text of DOI:10.1002/adsc.201000032

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DOI: 10.1002/adsc.201000032
An Efficient and Selective Epoxidation of Olefins with Novel
Methyltrioxorhenium/(Fluorous Ponytailed) 2,2’-Bipyridine
Catalysts
Raffaele Saladino,a,* Maria Cristina Ginnasi,a Daniela Collalto,a
Roberta Bernini,a,* and Claudia Crestinib
a
Dipartimento di Agrobiologia e Agrochimica (DABAC), Universitꢀ degli Studi della Tuscia, Via S. Camillo De Lellis,
01100 Viterbo, Italy
Fax : (+39)-0761-357-242; e-mail: saladino@unitus.it or berninir@unitus.it
Dipartimento di Scienze e Tecnologie Chimiche, Universitꢀ di Roma Tor Vergata, Via della Ricerca Scientifica,
b
00133 Roma, Italy
Received: January 14, 2010; Revised: March 26, 2010; Published online: May 3, 2010
Abstract: Novel complexes between methyltrioxo-
rhenium (MTO) and bis(fluorous-ponytailed) 2,2’-
bipyridines (bpy-Fn) were synthesized and used for
the oxidation of alkenes with hydrogen peroxide
under fluorous catalysis. High conversions and
yields of the corresponding epoxides were obtained.
catalyzed by metal/fluorous nitrogen ligands include
manganese,[5] cobalt,[6] ruthenium,[7] and copper[8] oxi-
dations under both “heavy” and “light” conditions.
Methyltrioxorhenium (MTO) is one of the most
powerful catalysts for the activation of hydrogen per-
oxide in the oxidation of natural substances and fine
chemicals. In these reactions the active catalytic forms
are monoperoxorhenium [MeRe(O)2(O2)] and bisper-
oxorhenium [MeRe(O)(O2)2] complexes and/or their
adducts with solvent molecules.[9] Among the synthet-
ic applications of MTO, the epoxidation of olefins re-
ceived greater attention. The most relevant drawback
for this reaction is the concomitant ring opening of
the newly formed oxiranyl ring to diols due to acidic
Keywords: 2,2’-bipyridines; epoxidation; fluorous
ponytails; homogeneous catalysis; hydrogen perox-
ide; methyltrioxorhenium
In the last few years the fluorous catalysis has properties of MTO. To date, different procedures
become a novel synthetic strategy in the design and have been developed to avoid this side reaction, in-
reuse of both homogeneous and heterogeneous metal cluding the use of ligands bearing one or more nitro-
catalysts.[1] Two branches have been developed in this gen atoms as mediators for the oxidation. In this case,
field, namely the “heavy” and the “light” fluorous adducts of MTO with Lewis bases, of general formula
catalysis.[2] In both cases ligands bearing fluorous MTO/Ln [where L=ligand, n=1 (monodentate) or 2
atoms are used to coordinate the active metal species. (bidentate)], are prepared by reaction with low mo-
In the “heavy” fluorous catalysis, ligands bearing 39 lecular weight aromatic amines, such as pyridine, pyri-
or more fluorines are required to allow the complete dine derivatives,[10] bipyridines[11] as well as easily
solubility of the catalyst in the fluorinated solvents in available polymers bearing the pyridinyl moiety as an-
biphasic transformations. The “light” fluorous cataly- chorage site for the rhenium atom.[12] These adducts
sis typically is performed with 9–17 fluorines to in- inhibit the formation of diols by tuning the electronic
crease the solubility of catalysts in common organic properties of MTO, their stability depending both on
solvents. In this latter case the catalyst can be easily the physical and chemical properties of the ligand and
recovered at the end of the transformation by a fluo- of the reaction medium. Despite the large efforts de-
rous solid-phase extraction technique (F-SPE).[3] Irre- voted to the synthesis of novel MTO/Ln adducts, to
spective to the nature of the fluorine catalysis, 2,2’-bi- the best of our knowledge there are no examples
pyridines with 4,4’-bis(fluorous-ponytailed) substitu- dealing with the synthesis of complexes between
ents are commonly used as bidentate ligands in order MTO and fluorinated nitrogen ligands. Recently, fluo-
to maintain the geometry at the metal center even rinated rhenium(I)-bipyridine complexes bearing fluo-
when the metal is oxidized or reduced. Usually, meth- rinated alkyl ligands were prepared and their photo-
ylene spacers of general formula (CH2)
are used to insulate the active site from the electron-
withdrawing fluorines.[4] Examples of redox processes synthesis of complexes between MTO and bis(fluo-
(CF2)nCF3 chemical properties were investigated.[13]
In this paper we describe the hitherto unreported
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Adv. Synth. Catal. 2010, 352, 1284 – 1290

An Efficient and Selective Epoxidation of Olefins
Table 1. Chemical shifts (d, ppm) and DD Ar-H 3,3’, DD Ar-
H 5,5’, DD Ar-H 6,6’ of ligands 2a–f and catalysts 3a–f.
rous-ponytailed) 2,2’-bipyridines (MTO/bpy-Fn) char-
acterized by different values of fluorophilicity. These
complexes are efficient and selective catalysts for the
epoxidation of olefins with hydrogen peroxide (H2O2)
under fluorous catalysis conditions.
Entry Ligand/Cat- ReCH3 DD Ar-
DD Ar-
H 5,5’
DD Ar-
H 6,6’
alyst
H 3,3’
1
2
3
4
5
6
7
8
MTO/bpy
1.04
–
1.28
–
1.27
–
1.28
–
1.33
–
1.33
–
–
0.21
–
0.29
–
0.29
Bis(fluorous-ponytailed) 2,2’-bipyridines 2a–f (bpy-
Fn) were prepared according to literature procedures
starting from commercially available 4,4’-dimethyl-
2,2’-bipyridine.[14] Briefly, compound 1 was treated
with lithium diisopropylamide (LDA) in dry THF at
low temperature (À788C) followed by alkylation with
2a
3a
2b
3b
2c
3c
2d
3d
2e
3e
2f
3f
0.09
0.10
0.10
0.13
0.05
0.27
0.25
0.20
0.12
0.09
0.31
0.24
0.24
0.16
0.10
perfluoroalkyl
iodides
of
general
formula
CnF2n+1CH2CH2I (n=5, 7 and 9) to afford desired
mono- and bis(fluorous-ponytailed) nitrogen ligands
(bpy-Fn) in acceptable yield [(Scheme 1, steps a) and
9
10
11
12
13
1.34
Table 2. Parameters of the ligands 2a–f.
Entry
Ligand
F [%]
FPC[a]
f
1
2
3
4
5
6
2a
2b
2c
2d
2e
2f
46.7
51.3
54.6
56.4
60.0
62.5
0.01
0.04
0.09
0.25
0.41
2.60
À4.60
À3.20
À2.40
À2.40
À0.90
+0.95
[a]
FPC=ci
phase/ci
phase; ci is the concentration of
organic
fluorous
fluorinated speciesi expressed in mol/L; fluorous phase
was FC77 and organic phase was dichloromethane.
Scheme 1.
ty[16,17] f=ln
calculated for a biphasic mixture (1:1 v/v) of perfluor-
ACHTUNGTRENN[UNG FPC]. As a usual procedure, FPCs were
b)]. Freshly prepared bpy-Fn 2a–f (0.18 mmol) were ooctane (FC77) and CH2Cl2. These parameters are re-
successively added to a solution of MTO (0.18 mmol) ported in Table 2.
in diethyl ether (5.0 mL) at room temperature for 4 h
On the basis of these data, ligands 2a–f should be
(Scheme 1, step c). The corresponding MTO/bpy-Fn useful for “light fluorous catalysis” in accordance with
catalysts 3a–f were easily recovered in quantitative previous trends observed for fluorocarbon modified
yield as yellow powders by cooling down to 08C.
Nuclear magnetic resonance analysis (1H NMR, 60%, is also useful for “heavy fluorous catalysis”).
13C NMR and 19F NMR) confirmed the assigned struc-
Epoxidations with MTO/bpy-Fn catalysts 3a–f and
organics (and, in principle, the ligand 2f, with F>
tures. In particular, we observed a downfield shift for H2O2 (35% aqueous solution) were investigated with
ReCH3 protons in fluorinated catalysts 3a–f compared cyclic aliphatic olefins, cyclohexene 4 and cis-cyclo-
to the complex between MTO and 4,4’-dimethyl-2,2’- ctene 6 (0.26 mmol) and low reactive aromatic olefins,
bipyridine as a reference (DD=0.23–0.30 ppm, see trans-stilbene 8 and styrene 11, as representative
Table 1). Downfield shifts for H-3,3’, H-5,5’ and H- model substrates (Scheme 2). All reactions were per-
1
6,6’ protons in H NMR spectra of 3a–f compared to formed applying the “light fluorous catalysis” strategy
ligands 2a–f were also observed in accordance with in CH2Cl2 (2.5 mL) at room temperature using 2% in
the general behaviour previously reported for MTO weight of 3a–f. The epoxidation of 4 with the complex
complexes (DD Ar-H 3,3’, DD Ar-H 5,5’, DD Ar-H MTO/bpy was also performed as reference. The reac-
6,6’, see Table 1).[15]
tions were monitored by GC-MS analysis (see Experi-
Ligands 2a–f were further characterized by evalua- mental Section for more details). In the absence of
tion of typical parameters for fluorinated species, the catalyst, less than 5% conversion of substrates
such as the percent of fluorine content (F), the fluo- took place under otherwise identical conditions. The
rous partition coefficient (FPC) and the fluorophilici- results are summarized in Table 3. Noteworthy, irre-
Adv. Synth. Catal. 2010, 352, 1284 – 1290
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to the known lower reactivity of aromatic olefins with
respect to aliphatic ones (Table 1, entries 16–21 and
23–28 versus entries 2–7 and 9–14). As a general
trend, the fluorophilicity f of the catalysts did not in-
fluenced the selectivity of the epoxidation, with the
only exception of trans-stilbene 8, in which case, cata-
lysts 3a–c bearing mono(fluorous-ponytailed) nitrogen
ligands were more selective than the corresponding
bisACTHUNRTGNEUNG(fluorous-ponytailed) systems 3d–f (see, for exam-
ple, Table 3, entries 16–18 versus entries 19–21).
The turnover frequencies (TOFs; moles of convert-
ed substrate per mole of catalyst per hour) of MTO/
bpy-Fn catalysts 3a–f calculated for the epoxidation of
olefins 4, 6, 8 and 11 were found in the range of 1.0–
25 depending on the experimental conditions and
were similar to those of the parent MTO/bpy catalyst,
confirming that the fluorinated chains did not modify
the catalytic activity of the MTO active species.
Finally, our efforts were aimed at recycling the cat-
alysts. The oxidation of cyclohexene 4 with 3f was
performed as a selected example. The thermomorphic
method based on the temperature-dependent solubili-
ty of the fluorous catalysts in the organic solvent[16]
was chosen as procedure to recover the catalyst.
After the oxidation, the reaction mixture was directly
cooled until T=À608C. A precipitate was observed
and the supernatant phase containing the oxidation
Scheme 2.
spective of the presence of one or two fluorinated product was removed. The precipitate was washed
chains and number of fluorine atoms, MTO/bpy-Fn and used for a successive oxidation (see Experimental
3a–f were highly efficient and selective catalysts in Section). Unfortunately, the conversion of substrate
the epoxidation reaction of olefins 4 and 6 and the and yield of epoxide 5 were dramatically decreased
corresponding epoxides 5 and 7 were isolated in (25% and 20%, respectively).
quantitative conversions and yields after only 2–5 h
(Table 1, entries 2–7, 9–14). The MTO/bpy catalyst 3a by a fluorous solid-phase extraction technique
showed a similar behaviour in terms of yield and reac- (F-SPE). Fluorous silica gel as solid phase (commer-
A better result was obtained with the light catalyst
AHCTUNGTRENNUNG
tion time suggesting that the presence of fluorine cially available as FluoroFlash ꢂ), a mixture of meth-
atoms in the side-chains did not interfere with the re- anol/water as fluorophobic solvent and methanol as
activity of the MTO active species (Table 3, entries 1, fluorophilic solvent were used experimentally.[3] Brief-
8, 15 and 22).
ly, the reaction mixture dissolved in DMF was
Catalysts 3a–f were also efficient systems in the oxi- charged on column previously preconditioned with
dation of the aromatic olefins trans-stilbene 8 and sty- methanol/water (80:20). The column was eluted with
rene 11 (Table 1, entries 16–21 and 23–28). In particu- methanol/water 80:20 to recover epoxide 5 followed
lar, in the oxidation of trans-stilbene 8, the epoxide 9 by methanol to afford 3a in appreciable yield (60%).
was again obtained as the main reaction product in Catalyst 3a was used in a successive run without any
64–92% conversion and 45–82% yield (Table 3, en- further purification showing the expected reactivity
tries 16–21). According to the known high reactivity (conversion: 75%; yield of epoxide 5: 75%).
of stilbene epoxide to give nucleophilic ring-opening
Thus, in our hands the F-SPE technique was the
reactions, a significant amount of the corresponding most efficient recycling procedure. However, a de-
diol 10 was observed (Table 3, entries 16-21). Note- crease of the reactivity of catalyst 3a was observed
worthy, the selectivity in the oxidation of 8 was tuned during the successive run (conversion: 45%; yield of
by the nature of the ligand, MTO/bpy-Fn 3b being the epoxide 5: 45%).
most efficient catalyst (Table 3, entry 17). In the oxi-
In conclusion, in this paper mono- and bis(fluorous-
dation of styrene 11, the epoxide 12 was obtained as ponytailed)/MTO catalysts were prepared for the first
the main product in 83–90% conversion and 80–87% time in acceptable yield and applied for the activation
yield (Table 1, entries 23–28), besides unreacted sub- of environmental friendly H2O2 in the epoxidation of
strate and traces of diol 13. As expected, longer reac- aliphatic and aromatic olefins under fluorous catalysis.
tion times were required for the oxidation of 11 due The epoxides were obtained in high yield and selec-
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Adv. Synth. Catal. 2010, 352, 1284 – 1290

An Efficient and Selective Epoxidation of Olefins
Table 3. Experimental data of oxidation of alkenes 4–8 with perfluoroalkylated catalysts 3a–f.[a]
Entry
Substrate
Catalyst
Reaction time [h]
Conv. [%][b]
Yield [%][b]
1
cyclohexene 4
MTO/bpy
5
98
5: 97
2
3a
5
97
5: 97
3
4
5
3b
3c
3d
5
5
2
>98
>98
96
5: >98
5: >98
5: 96
6
7
8
9
3e
3f
3
3
5
5
3
5
3
4
>98
>98
>98
>98
>98
82
>98
>98
>98
65
64
92
89
85
77
82
85
83
5: >98
5: >98
7: >98
7: >98
7: >98
7: 82
7: >98
7: >98
cis-cycloctene 6
trans-stilbene 8
styrene 11
MTO/bpy
3a
3b
3c
3d
3e
3f
MTO/bpy
3a
3b
3c
3d
3e
3f
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
4
7: >98
24
24
24
24
24
24
20
48
48
48
48
60
48
48
9: 54; 10: 11
9: 52; 10: 12
9: 82; 10: 10
9: 76; 10: 13
9: 45; 10: 40
9: 65; 10: 12
9: 70; 10: 12
12: 80; 13: 5
12: 80; 13: 3
12: 85; 13: 10
12: 86; 13: 4
12: 86; 13: 3
12: 85
MTO/bpy
3a
3b
3c
3d
3e
3f
95
90
89
85
87
12: 87
[a]
Reaction conditions: substrate (0.26 mmol), catalyst (2%), hydrogen peroxide (35% water solution, 2 equiv.), dichlorome-
thane (2.5 mL), room temperature.
Calculated by GC-MS analysis.
[b]
tivity, values comparable to that of non-fluorinated
MTO complex. With the only exception of trans-stil-
bene, the fluorophilicity of the ligand did not influ-
ence the reactivity, suggesting that three carbon units
in the methylene spacer effectively insulated the bi-
pyridyl ring and the rhenium center from the elec-
tron-withdrawing effect of the fluorinated alkyl
chains. The MTO/bpy-Fn catalysts can be recovered
by a fluorous solid-phase extraction technique and
used in successive runs. Since MTO shows multifunc-
tional catalytic properties including Lewis and Brçnst-
ed activity and metathesis properties,[18] these results
are a promising entry to further exploiting the fluo-
rine chemistry in the family of MTO-based organo-
metallic species.
able (Merck). Thin layer chromatography was carried out
using Merck platen Kieselgel 60 F254. 1H and 13C NMR
spectra were recorded on a Bruker (200 MHz) spectrome-
ter; 19F NMR were taken on a Bruker AMX 400 MHz.
Chemical shifts are reported in d values. Mass spectra were
recorded on a VG 70/250S spectrometer with an electron
beam of 70 eV and a CP-SIL 8 CB-MS column (25 mꢃ
0.25 mm and 0.25 mm film thickness). GC analysis were per-
formed using an isothermal temperature profile of 40 or
808C for 5 min, followed by a 108CminÀ1 temperature gradi-
ent to 2508C for 10 min. The injector temperature was
2808C.
Preparation of 4-(Perfluoroalkyl)-4’-methyl-2,2’-
bipyridines (2a–c) and 4,4’-Bis(perfluoroalkyl)-2,2’-
bipyridines (2d–f)
The preparation was performed according to that reported
in the literature.[14] Into a dry round-bottom flask, 20 mL of
dry THF were added. After cooling to À788C, LDA 2M
(0.3 mL, 2.3 mmol) and a 0.5M solution of 4,4’-dimethyl-
2,2’-bypiridine 1, (0.198 g, 1.08 mmol) in 2 mL of dry THF
were added. The mixture was kept under stirring for 3 h. To
Experimental Section
All chemicals and FluoroFlashꢂ were purchased from Al-
drich Company. Solvents were of the hightest commercially
available quality. Dry tetrahydrofuran was prepared accord-
ing to classical procedures. Silica gel was commercially avail-
the
dianion
obtained,
the
perfluoroalkyl
iodide
CnF2n+1CH2CH2I (2.3 mmol) was added and the mixture was
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Raffaele Saladino et al.
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kept under stirring for 1 h at À788C, then warmed up to
room temperature and kept under stirring overnight. The re-
action was quenched with brine (20 mL); the residue was
extracted with diethyl ether (3ꢃ20 mL) and dried over
Na2SO4. Evaporation of the solvent under reduced pressure,
afforded a crude mixture. After crystallization and, if neces-
sary, chromatographic purification on silica gel (eluent: di-
chloromethane/methanol), 4-(perfluoroalkyl)-4’-methyl-2,2’-
bipyridines 2a–c and 4,4’-bis(perfluoroalkyl)-2,2’-bipyridines
2d–f were respectively isolated in 20–40% yield. Spectro-
scopic data are reported below.
4-(1H,1H,2H,2H,3H,3H-Perfluorononyl)-4’-methyl-2,2’-
bipyridine (2a): Yield: 36%. Light brown solid. 1H NMR
(200 MHz, CDCl3): d=8.61–8.54 (m, Ar-H 6,6’), 8.33–8.29
(m, 2H, Ar-H 3,3’), 7.23–7.18 (m, 2H, Ar-H 5,5’), 2.84–2.63
(m, 2H, Ar-CH2), 2.46 (s, 3H, Ar-CH3), 2.22–1.95 (m, 4H,
-CH2CH2CH2CF2-); 13C NMR (200 MHz, CDCl3): d=156,6
(C-2’), 155.8 (C-2), 150.5 (C-4), 149.3 (C-6’), 149 (C-6), 148.2
Preparation of MTO Complexes (3a–f)
0.18 mmol of perfluoroalkyl bipyridines 2a–f were added to
a solution of MTO (0.045 g, 0.18 mmol) in diethyl ether
(5.0 mL). The mixture was kept under stirring for 2 h at
room temperature. After cooling down to 08C, a yellow pre-
cipitate was formed. The solid was filtered off, washed with
pentane and dried under a flow of nitrogen until constant
weight. Spectroscopic data are described below.
MTO/4-(1H,1H,2H,2H,3H,3H-perfluorononyl)-4’-
methyl-2,2’-bipyridine (3a): Yield: 98%. Yellow powder.
1H NMR (200 MHz, CDCl3): d=8.91–8.88 (d, J=5.4 Hz,
3
1H, Ar-H 6’), 8.85–8.82 (d, J=5.4 Hz, 1H, Ar-H 6). 8.11 (s,
2H, Ar-H 3,3’), 7.36–7.33 (m, 2H, ArH 5,5’), 2.92–2.85 (m,
2H, Ar-CH2), 2.54 (s, 3H, Ar-CH3), 2.27–2.00 (m, 4H,
-CH2CH2CH2CF2-), 1.28 (3H, MTO-CH3); 13C NMR
(200 MHz, CDCl3): d=154.7 (C- 2’), 152.3 (C-2), 150.7 (C-
4), 150.0 (C-4’), 149.2 (C-6’), 148.8 (C-6) 127.4 (C-5’), 126.2-
AHCTUNGERTN(GNUN C-5), 124.3 (C-3’), 123.4 (C-3), 34.5 (-CF2CH2CH2CH2-Ar),
(C-4’), 122.1
ACHTUNGTRENNUNG(C-3’), 121.1 (C-3), 34.5 (-CF2CH2CH2CH2-Ar),
30.4 (-CF2CH2CH2CH2-Ar), 28.0 (CH3-Re), 21.4 (CH3-Ar),
21.0 (-CF2CH2CH2CH2-Ar); 19F NMR (376.4 MHz, CDCl3):
d=À128.8 (CF2, 2F), À126.0 (CF2, 2F), À125.5 (CF2, 2F),
À124.5 (CF2, 2F), À116.7 (CF2, 2F), À83.4 (CF3, 3F).
MTO/4-(1H,1H,2H,2H,3H,3H-perfluoroundecyl)-4’-
methyl-2,2’-bipyridine (3b): Yield: 98%. Yellow powder.
1H NMR (200 MHz, CDCl3): d=8.90–8.87 (d, J=5.5 Hz,
30.4 (-CF2CH2CH2CH2-Ar),
21.1
(CH3-Ar),
21.0
(-CF2CH2CH2CH2-Ar); 19F NMR (376.4 MHz, CDCl3): d=
À131.4 (CF2, 2F), À128.6 (CF2, 2F), À128.1 (CF2, 2F),
À127.2 (CF2, 2F), À119.1 (CF2, 2F), À86.0 (CF3, 3F).
4-(1H,1H,2H,2H,3H,3H-Perfluoroundecyl)-4’-methyl-
2,2’-bipyridine (2b): Yield: 33%. Light brown solid.
1H NMR (200 MHz, CDCl3): d=8.59–8.56 (dd, 5J=0.7 Hz,
3J=5.7 Hz 1H, Ar-H 6’), 8.53–8.50 (dd, 5J=0.5 Hz, 3J=
5.0 Hz, 1H, Ar-H 6), 8.23–8,19 (m, 2H, Ar-H 3,3’), 7.14–7.11
(2dd, 4J=1.69 Hz, 3J=6.6 Hz, 2H, 5,5’) 2.88–2.66 (m, 2H,
Ar-CH2-), 2.42 (3H, s, Ar-CH3), 2.19–2.02 (m, 4H,
-CH2CH2CH2CF2-); 13C NMR (200 MHz, CDCl3): d=156.6
(C-2’), 155.8 (C-2), 150.6 (C-4), 149.3 (C-6’), 149.0 (C-6),
148.2 (C-4’), 124.8 (C-5’), 123.6 (C-5), 121.1 (C-3’), 121.0 (C-
3), 34.6 (-CF2CH2CH2CH2-Ar), 30.4 (-CF2CH2CH2CH2-Ar),
21.2 (CH3-Ar), 21.0 (-CF2CH2CH2CH2-Ar): 19F NMR
(376.4 MHz, CDCl3): d=À131.1 (CF2, 2F), À128.3 (CF2,
2F), À128.0 (CF2, 2F), À127.7 (CF2, 2F), À126.9 (CF2, 4F),
À119.1 (CF2, 4F), À85.7 (CF3, 3F).
3
1H, Ar-H 6’), 8.85–8.82 (d, J=5.5, 1H, Ar-H 6), 8.12(s, 2H,
Ar-H 3,3’), 7.36–7.34 (2dd, 4J=1.69 Hz, 3J=5.5 Hz, 2H,
5,5’), 2.93–2.85 (m, 2H, ArCH2-), 2.55 (s, 3H, ArCH3), 2.15–
2.00 (m, 4H, -CH2CH2CH2CF2-), 1.27 (s, 3H, MTO-CH3);
13C NMR (200 MHz, CDCl3): d=156.6 (C-2’), 155.8 (C-2),
150.6 (C-4), 149.3 (C-6’), 149.0 (C-6), 149.1 (C-4’), 124.8 (C-
5’), 123.6ACTHNUGTRNEUNG(C-5), 121.1 (C-3’), 121.0 (C-3), 34.6
(-CF2CH2CH2CH2-Ar), 30.4 (-CF2CH2CH2CH2-Ar) 28.0
(CH3-Re), 21.2 (1C, CH3-Ar) 21.0 (1C, -CF2CH2CH2CH2-
Ar; 19F NMR (376.4 MHz, CDCl3): d=À126.7 (CF2, 2F),
À123.9 (CF2, 2F), À123.6 (CF2, 2F), À123.3 (CF2, 2F),
À122.5 (CF2, 4F), À114.7 (CF2, 4F), À81.3 (CF3, 3F).
MTO/4-(1H,1H,2H,2H,3H,3H-perfluorotridecyl)-4’-
methyl-2,2’-bipyridine (3c): Yield: 98%. Yellow powder.
1H NMR (200 MHz, CDCl3): d=8.83–8.76 (m, 2H, Ar-H
6,6’), 8.41–8.29 (m, 2H, Ar-H 3,3’), 7.42–7.34 (m, 2H, Ar-H
5,5’), 2.94–2.87 (m, 2H, ArCH2-), 2.58 (s, 3H, ArCH3), 2.13–
2.07 (m, 4H, -CH2CH2CH2CF2-), 1.28 (s, 3H, MTO-CH3);
13C NMR (200 MHz, CDCl3): d=153.6 (C-2,2’), 150.9 (C-4),
149.1 (C-4’), 149.0 (C-6,6’), 126.6 (C-5’), 125.6 (C-5), 124.1
(C-3’), 123.0 (C-3), 34.6 (-CF2CH2CH2CH2-Ar), 30.3
(-CF2CH2CH2CH2-Ar), 26.0 (CH3-Re), 21.7 (CH3-Ar), 20.9
(-CF2CH2CH2CH2-Ar; 19F NMR (376.4 MHz, CDCl3): d=
À126.7 (CF2, 4F), À123.7 (CF2, 4F), À122.5 (CF2, 4F),
À118.2 (CF2, 2F), À114.7 (CF2, 4F), À81.4 (CF3, 3F).
4-(1H,1H,2H,2H,3H,3H-Perfluorotridecyl))-4’-methyl-
2,2’-bipyridine (2c): Yield: 25%. Light brown solid.
1H NMR (200 MHz, CDCl3): d=8.59–8.57 (dd, 5J=0.7 Hz,
3J=5.0 Hz, 1H, Ar-H 6’), 8.54–8.51 (dd, 5J=0.7 Hz, 3J=
5.0 Hz, 1H, Ar-H 6) 8.26–8.23 (m, 2H, Ar-H 3,3’), 7.15–
7.11(2dd, 4J=1.56 Hz, 3J=6.5 Hz, 2H, 5,5’), 2.82–2.75 (m,
2H, Ar-CH2), 2.43 (s, 3H, Ar-CH3), 2.15–2.02 (m, 4H,
-CH2CH2CH2CF2-); 13C NMR (200 MHz, CDCl3): d=157.9
(C-2’), 154.5 (C-2), 151.4 (C-4), 149.1 (C-6’), 147.8 (C-6),
148.2 (C-4’), 125.2 (C-5’), 124.1ACTHNUGRTNEUNG(C-5), 122.8 (C-3’), 121.8 (C-
3), 34.6 (-CF2CH2CH2CH2-Ar), 30.6 (-CF2CH2CH2CH2-Ar),
21.4 (CH3-Ar), 20.9 (-CF2CH2CH2CH2-Ar); 19F NMR
(376.4 MHz, CDCl3): d=À131.0 (CF2, 4F), À128.0 (CF2,
4F), À126.8 (CF2, 4F), À122.5 (CF2, 2F), À119.0 (CF2, 4F),
À85.7 (CF3, 3F).
MTO/4,4’-bis(1H,1H,2H,2H,3H,3H-perfluorononyl)-
1
2,2’-bipyridine (3d): Yield: 98%. Yellow powder. H NMR
(200 MHz, CDCl3): d=8.85 (d, 2H, J=5.4 Hz, Ar-H 6,6’),
8.15 (s, 2H, Ar-H 3,3’), 7.33 (d, 2H, J=5.5 Hz, Ar-H 5,5’),
2.92–2.84 (m, 4H, ArCH2), 2.22–2.06 (m, 8H,
-CH2CH2CH2CF2-), 1.3 (s, 3H, MTO-CH3); 13C NMR
(200 MHz, CDCl3): d=154.0 (C-2,2’), 152.7 (C-4,4’), 149.5
4,4’-Bis(1H,1H,2H,2H,3H,3H-perfluorononyl)-2,2’-bi-
pyridine (2d): Yield: 40%. White solid. Spectroscopic data
were in accord to those reported in the literature.[14]
4,4’-Bis(1H,1H,2H,2H,3H,3H-perfluoroundecyl)-2,2’-bi-
pyridine (2e): Yield: 37%. White solid. Spectroscopic data
were in accord to those reported in the literature.[14]
4,4’-Bis(1H,1H,2H,2H,3H,3H-perfluorotridecyl)-2,2’-bi-
pyridine (2f): Yield: 30%. White solid. Spectroscopic data
were accord to those reported in the literature.[14]
(C-6,6’),
(-CF2CH2CH2CH2-Ar), 30.1 (-CF2CH2CH2CH2-Ar), 23.9
(CH3-Re), 20.9 (-CF2CH2CH2CH2-Ar);
19F NMR
(376.4 MHz, CDCl3): d=À128.8 (CF2, 4F), À126.0 (CF2,
125.2
(C-3,3’),
122.1
(C-5,5’),
34.6
1288
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ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 1284 – 1290

An Efficient and Selective Epoxidation of Olefins
4F), À125.5 (CF2, 4F), À124.6 (CF2, 4F), À116.7 (CF2, 4F),
À83.3 (CF3, 6F).
Recycling Experiments Using the Fluorous Biphasic
Catalysis (FBC) Technique
MTO/4,4’-bis(1H,1H,2H,2H,3H,3H-perfluoroundecyl)-
1
To apply the F-SPE technique, we used fluorous silica gel as
solid phase (commercially available as FluoroFlashꢂ) and a
mixture of methanol/water as fluorophobic solvent and
methanol as fluorophilic solvent. The oxidation of cyclohex-
ene 4 catalyzed by 3a was performed in dichloromethane at
room temperature. The silica gel was washed with DMF.
The reaction mixture was dissolved in DMF and charged in
a column with the solid phase previously preconditioned
with methanol/water (80:20). Firstly, the column was eluted
with methanol/water 80:20 to recover the oxidation product
(epoxide 9); then with methanol to recover the fluorinated
species (catalyst 3a). Finally, the column was washed with
acetone to regenerate the fluorous solid phase.
2,2’-bipyridine (3e): Yield: 98%. Yellow powder. H NMR
(200 MHz, CDCl3): d=8.76 (d, 2H, J=5.4 Hz, Ar-H 6,6’),
8.18 (s, 2H, Ar-H 3,3’), 7.27–7.24 (m, 2H, Ar-H 5,5’), 2.91–
2.65 (m, 4H, ArCH2), 2.24–1.82 (m, 8H, -CH2CH2CH2CF2-),
1.33 (s, 3H, MTO-CH3); 13C NMR (200 MHz, CDCl3): d=
156.1 (C-2,2’), 153.7 (C-4,4’), 149.4 (C-6,6’), 124.8 (C-3,3’),
122.8
(-CF2CH2CH2CH2-Ar), 30.3 (-CF2CH2CH2CH2-Ar), 23.9
(CH3-Re), 20.9 (-CF2CH2CH2CH2-Ar);
19F NMR
(C-5,5’),
34.6
(-CF2CH2CH2CH2-Ar),
33.8
(376.4 MHz, CDCl3): d=À126.7 (CF2, 4F), À124.0 (CF2,
4F), À123.4 (CF2, 4F), À122.6 (CF2, 8F), À118.1 (CF2, 4F),
À114.8 (CF2, 4F), À81.3 (CF3, 6F).
MTO/4,4’-bis(1H,1H,2H,2H,3H,3H-perfluorotridecyl)-
1
2,2’-bipyridine (3f): Yield: 98%. Yellow powder. H NMR
(200 MHz, CDCl3): d=8.70 (d, 2H, J=5.4 Hz, Ar-H 6,6’),
8.20 (s, 2H, Ar-H 3,3’), 7.24–7.21 (m, 2H, Ar-H 5,5’), 2.90–
2.68 (m, 4H, ArCH2), 2.19–2.04 (m, 8H, -CH2CH2CH2CF2-),
1.54 (s, 3H, MTO-CH3); 13C NMR (200 MHz, CDCl3): d=
156.2 (C-2,2’) 152.7 (C-4,4’), 149.5 (C-6,6’), 124.8 (C-3,3’),
Acknowledgements
122.8
(C-5,5’),
34.6
(-CF2CH2CH2CH2-Ar),
23.9 (CH3-Re),
30.1
20.9
The University of Tuscia and Ministero della Ricerca Scientif-
ica e Tecnologica are acknowledged for the financial support.
(-CF2CH2CH2CH2-Ar),
(-CF2CH2CH2CH2-Ar); 19F NMR (376.4 MHz, CDCl3): d=
À126.7 (CF2, 4F), À124.0 (CF2, 4F), À123.6 (CF2, 4F),
À122.5 (CF2, 16F), À118.1 (CF2, 4F), À114.8 (CF2, 4F),
À81.4 (CF3, 6F).
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