Fullerene as a platform for recyclable TEMPO organocatalysts for the oxidation of alcohols

Article abstract of DOI:10.1002/cctc.201402262

[60]Fullerene has been employed successfully as a molecular platform to anchor 12 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) moieties. Such an octahedrally substituted C₆₀-derivative has been employed as an organocatalyst for the oxidation of primary and secondary alcohols using the Anelli protocol. The reaction showed a general applicability to various alcohols, and the catalyst was recovered easily and could be recycled for at least seven cycles with no loss in catalytic activity. EPR spectroscopy studies revealed that the amount of radicals decreases during the catalytic cycles, even if the recovered material still displays unchanged catalytic activity. This new approach paves the way to use fullerene as a molecular platform to support other kinds of organometallic and organocatalysts as well as for their use as model compounds to understand the behavior of other nanocarbon-supported catalysts.

Full text of DOI:10.1002/cctc.201402262

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DOI: 10.1002/cctc.201402262
Fullerene as a Platform for Recyclable TEMPO
Organocatalysts for the Oxidation of Alcohols**
[a]
[a]
[b]
[b]
Hazi Ahmad Beejapur, Vincenzo Campisciano, Paola Franchi, Marco Lucarini,
[a]
[a]
Francesco Giacalone,* and Michelangelo Gruttadauria*
[
60]Fullerene has been employed successfully as a molecular
platform to anchor 12 2,2,6,6-tetramethylpiperidine-1-oxyl
TEMPO) moieties. Such an octahedrally substituted C -deriva-
spectroscopy studies revealed that the amount of radicals de-
creases during the catalytic cycles, even if the recovered mate-
rial still displays unchanged catalytic activity. This new ap-
proach paves the way to use fullerene as a molecular platform
to support other kinds of organometallic and organocatalysts
as well as for their use as model compounds to understand
the behavior of other nanocarbon-supported catalysts.
(
60
tive has been employed as an organocatalyst for the oxidation
of primary and secondary alcohols using the Anelli protocol.
The reaction showed a general applicability to various alcohols,
and the catalyst was recovered easily and could be recycled
for at least seven cycles with no loss in catalytic activity. EPR
Introduction
Oxidations of both primary and secondary alcohols to alde-
hydes and ketones, respectively, are processes of fundamental
importance on academic and industrial scales because of their
has been studied intensively to find a suitable application.
Some of the potential applications of C derivatives are in the
60
[7]
[8]
fields of organic photovoltaics, nanomedicine, and smart
[
1]
[9]
key role in organic synthesis. 2,2,6,6-Tetramethylpiperidine-1-
oxyl (TEMPO) derivatives represent one of the most employed
classes of metal-free compounds for the selective oxidation of
materials. Carbon nanoforms (CNF) such as nanotubes (CNT),
nanodiamonds (nD), graphenes, and related materials have
been employed widely as supports both for metal nanoparti-
cles and organometallic complexes to be employed in cataly-
[
2]
alcohols, although their relatively high prices prevent large-
scale use, and new methods and strategies devoted to its re-
[10]
sis. However, just a few studies deal with the use of ful-
lerenes in catalysis, which focus mainly on the preparation of
[
3]
covery have been explored. Recently, we have been engaged
in the synthesis and application of ionic-liquid-tagged TEMPO
[11]
heterogeneous C -metal mixtures, and very recently, a fuller-
60
[
4]
derivatives as recyclable catalysts for the oxidation of alco-
ene-metformine multiadduct has been employed as ligand for
[
5]
II
hols through the “release and catch” approach. With this
background, we planned to employ the [60]fullerene sphere as
a molecular platform to host several organocatalyst moieties
for the first time to achieve a controlled, highly loaded, C -
Pd to form a recyclable nanocatalyst species for Suzuki cou-
[
12]
plings.
In the last two decades, several examples of C -
60
[13]
TEMPO systems prepared through the Prato, Bamford–Ste-
[
14]
[15]
vens, and Bingel synthetic protocols have been reported.
As an example, nitroxide malonate methanofullerenes in com-
60
based recyclable catalyst in the oxidation of alcohols to their
corresponding carbonyl compounds. As a result of the multi-
bination with the anticancer drug cyclophosphamide showed
[
6]
[15d]
gram production of fullerene, this exotic allotrope of carbon
a high antitumor activity against leukemia P-388,
and a full-
eropyrrolidine nitroxide has been employed as paramagnetic
probe to explore the inner environment of single-walled
[13k]
carbon nanotubes by forming peapods.
Nonetheless, to
date, almost all other TEMPO-fullerene systems have been em-
ployed mainly for EPR spectroscopy and electrochemical inves-
tigations and there are no examples of their catalytic activity.
[
a] H. A. Beejapur, V. Campisciano, Dr. F. Giacalone, Prof. M. Gruttadauria
Department of Biological, Chemical and Pharmaceutical Sciences and Tech-
nologies
University of Palermo
Viale delle Scienze s/n, Ed. 17, I-90128 Palermo (Italy)
Fax: (+39)091596825
E-mail: francesco.giacalone@unipa.it
Results and Discussion
michelangelo.gruttadauria@unipa.it
With the aim to explore whether fullerene can be employed
successfully as a recyclable molecular support to host a con-
trolled number of catalytic moieties, we prepared three C -
[
b] Dr. P. Franchi, Prof. M. Lucarini
Department of Chemistry “G. Ciamician”
University of Bologna
6
0
TEMPO systems to be tested in the oxidation of alcohols: C60-
Via San Giacomo 11, I-40126 Bologna (Italy)
T (2), C -T (3), and C -T (4) that have two, four, and 12
[**] TEMPO=2,2,6,6-tetramethylpiperidine-1-oxyl
2
60
4
60 12
TEMPO moieties, respectively (Scheme 1). The synthesis starts
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201402262.
[15d,16]
with the formation of TEMPO-bismalonate 1
from malonyl
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chloride and 4-hydroxy-TEMPO.
The Bingel reaction has been ap-
plied to prepare the TEMPO/full-
erene conjugates: if a 1:1 stoichi-
[15d,17]
ometry was employed, 2
and 3 were isolated by column
chromatography in 28 and 10%
yield, respectively, whereas the
use of 10:1 stoichiometry (1/C )
6
0
led to 4 in 54% yield. As a result
of the paramagnetic nature of
the nitroxide moieties in these
new systems, no valuable struc-
tural information can be gained
by NMR spectroscopy. Indeed, as
1
expected, the H NMR spectrum
of 4 has a very low resolution,
which makes structural assign-
ment rather difficult. To obtain
some useful information from
NMR spectroscopy, 4 was con-
verted into the analogous N-hy-
droxylamine, an excess of phe-
nylhydrazine was added directly
[18]
into the NMR tube, or it was
reduced by Na S O . Neverthe-
4
Scheme 1. Synthesis of C60-TEMPO systems. Reaction conditions: a) C60, CBr (2 equiv.), 1 (1 equiv.), DBU (4 equiv.),
2
2
4
PhCl, RT, 24 h. Yield: 2 (28%), 3 (10%); b) C60, CBr
54%).
4
(50 equiv.), 1 (10 equiv.), DBU (20 equiv.), PhCl, RT, 72 h. Yield: 4
less, the proton spectra so ob-
tained are not well resolved, but
show the presence of all the sig-
nals of TEMPOH (Figures S1 and
(
S2). Better indications have been achieved from FTIR spectra of
C -TEMPO systems, which show the presence of the carbonyl
60
stretching vibration along with that of NÀO· radicals at n˜ =
465 cm and that of C60 at n˜ =527 cm (Figure S3). Finally,
À1
À1
1
ESI-MS confirmed the proposed hexakis adduct structure for 4,
+
and the relevant peaks at m/z 3206.1 ([M+Na] ) and 1614.5
2+
(
[M+2Na] ) were present (Figure S4).
Figure 1a shows the EPR spectrum of a THF solution of 4.
This spectrum mainly shows one broad signal, the integrated
intensity of which corresponds to the initial amount of nitro-
xides expected for a hexakis adduct. The broadening (peak-to-
peak line width of 15 G) of the signal is reminiscent of that ob-
[19]
tained from very concentrated nitroxide solutions (>0.05m).
As the shape of the signal is independent of the concentration
of the radical in the range 0.01–1 mm, the signal broadening is
ascribed to spin exchange caused by the proximity of the spin
centers of 4 within the framework of the fullerene. This signal
is indicative of the presence not only of triplet transitions be-
tween two nitroxide units connected to the same malonate
unit but also of other multiplet transitions from higher spin
states that arise from multiple interactions between the 12 rad-
[20]
ical units. The spectrum also shows a signal characterized by
three equally spaced sharp lines presumably caused by mole-
cules of 4 that contain some tetramethylpiperidine units in the
diamagnetic form. Theoretical simulation of the experimental
spectrum, however, indicated that these correspond to less
than 3% of the total amount of nitroxide (Figure S6).
Figure 1. EPR spectra of a) 4 and b) 3 in THF at room temperature.
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The spectrum of 3 shows a five-line pattern (Figure 1b) in
which the second and fourth lines are broader. This spectrum
is very similar to that of a C -T derivative described by Nuret-
bromo-, and p-nitrobenzyl alcohols as well as 2-naphthalene-
methanol were converted quantitatively between 0.5 and 1.5 h
(entries 1–4). Secondary benzylic alcohols such as 1-indanol
and benzoin were converted quantitatively (entries 5–6),
whereas diphenylmethanol gave benzophenone in 87% yield
(entry 7). Cyclic secondary alcohols such as cyclohexanol and
1-tert-butoxycarbonyl-4-hydroxypiperidine (entries 8–9) and
acyclic secondary alcohols such as 2-decanol and 4-phenylbu-
tan-2-ol (entries 10–11) were oxidized with complete conver-
sions with longer reaction times in the latter cases. Finally, ex-
cellent yields were obtained with primary aliphatic alcohols
within 0.5–2 h (entries 12–14). Interestingly, primary alcohols
afforded the corresponding aldehydes selectively without un-
dergoing easy autoxidation to the corresponding carboxylic
60
2
dinov et al. in which spin exchange could be operative be-
[
15d]
tween only two nitroxide units.
This suggests that spin ex-
change occurs in 3 mainly between the two nitroxide units
linked to the same malonate fragment and not between radi-
cal centers that belong to different malonate units. This finding
suggests that steric hindrance drives the formation of these bis
adducts to keep the functionalized units quite far apart
(mainly as equatorial and trans adducts).
With the fullerene-TEMPO systems in hand, we started to
test their catalytic activity in the oxidation of 1-phenylethanol
to acetophenone by applying three different conditions in
which the co-oxidant was varied: hypervalent iodine(III) [bis-
[23]
acid probably because TEMPO systems are free-radical scav-
[
21]
[2g,24]
(
acetoxy)iodo]benzene (BAIB),
oxygen in the presence of
engers and hence act as autoxidation inhibitors.
[
22]
tert-butyl nitrite (TBN) as cocatalyst, and sodium hypochlor-
ite solution (commercial bleach) in the presence of KBr and
[
2a–c]
NaHCO to adjust the pH (Anelli’s conditions).
The results
3
are collected in Table 1 and show that with BAIB as the termi-
nal oxidant only 4 in 1 mol% is able to convert 1-phenyletha-
nol fully (entry 3). The three catalysts gave almost the same
promising results if oxygen was used (entries 4–6) even if the
yields were not quantitative. Finally, complete conversions in
a very short reaction time were obtained with all the C -
Table 2. Catalytic oxidation of primary and secondary alcohols with 4
under Anelli’s conditions.
[
a]
60
TEMPO conjugates if bleach in dichloromethane (DCM) was
used (entries 7–9). In all cases, control experiments performed
with no catalysts afforded conversions <5%.
Entry
Substrate
Product
t
Yield
[%]
[
h]
Then, we focused on 4 to explore the substrate scope of the
reaction because of its greater TEMPO/C60 ratio, which allowed
us to use less catalyst with a fixed loading (e.g., 2.1 mg of 4 is
needed for 0.8 mmol of alcohol versus 4.5 mg of 2). Catalyst 4
was highly active in the oxidation of a wide range of sub-
strates (Table 2). Primary benzylic alcohols, such as benzyl-, p-
1
2
0.5
>95
>95
0.5
0.5
1.5
3
4
>95
>95
Table 1. Catalytic oxidation of 1-phenylethanol with 2, 3, and 4 under
different reaction conditions.
5
6
1.0
7.0
>95
>95
[
a]
7
8
9
8.0
1.5
4.0
87
>95
>95
Entry
Catalyst
Conditions
t
Yield
[%]
[h]
[
[
[
b]
b]
b]
1
2
3
4
5
6
7
8
9
2
3
4
2
3
4
2
3
4
BAIB
BAIB
BAIB
16
16
16
4
70
trace
>95
75
72
72
>95
>95
>95
[
[
[
c]
c]
c]
aerobic
aerobic
aerobic
NaClO
NaClO
NaClO
4
4
1
1
1
0
6.0
>95
[
[
[
d]
d]
d]
11
6.0
0.5
>95
>95
1
1
2
[a] In all the reactions 1 mol% (based on TEMPO) of catalyst was em-
ployed. [b] Reaction conditions: alcohol (0.8 mmol), BAIB (1.1 equiv.),
DCM (2 mL), RT. [c] Reaction conditions: alcohol (0.8 mmol), TBN
13
1.5
2.0
>95
>95
14
(15 mol%), O
2
(balloon), water (0.5 mL), 508C. [d] Reaction conditions: al-
cohol (0.8 mmol), NaClO (2.86 mL, 0.35m), KBr (0.16 mL, 0.5m), NaHCO
3
[a] Reaction conditions: alcohol (0.8 mmol), NaClO (2.86 mL, 0.35m), KBr
(0.16 mL, 0.5m), NaHCO (1.28 mmol), DCM (2 mL), 0–158C.
(1.28 mmol), DCM (2 mL), 0–158C.
3
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Next, the different polarity between the oxidation products
and 4 was exploited to recover the catalyst easily and to per-
form a complete recycling study. After the first reaction, the
carbonyl compound can be isolated quickly by short chroma-
tography by eluting with a mixture of low-polarity solvents
(see Experimental Section and Figure S7). Then, the catalyst,
which displays a greater affinity toward silica gel than the
product and reactants, can be recovered easily by eluting with
a more polar mixture and it can be recycled after evaporation
of the solvent. A recycling study that used 1 mol% of 4 for the
oxidation of 1-phenylethanol or 1-decanol on a 4 mmol scale is
shown in Figure 2. In both cases, catalyst 4 can be recycled for
Figure 3. EPR spectra of fresh 4 (0.5 mm) and 4 after five and seven cycles in
THF.
thylpiperidine-1-oxyl (TEMPO) systems employed as active cat-
alysts for the oxidation of primary and secondary alcohols to
aldehydes and ketones. The main advantage of this approach
is to have highly loaded homogeneous catalytic systems that
can be recovered easily through a simple and fast silica pad,
which combines the benefits of homogeneous catalysis with
recyclability and cost abatement. The catalysts were active at
just 1 mol% loading (based on TEMPO) in at least seven cycles
with almost no loss in activity. Moreover, the success of the
present approach may pave the way toward the extensive use
of fullerene as a molecular support for other kinds of organo-
metallic and organocatalysts as well as for their use as model
compounds to understand the behavior of other nanocarbon-
supported catalysts. In addition, especially in the case of C -T
12
Figure 2. Recycling of 4 (1 mol%) in the formation of acetophenone or
decanal.
at least five cycles with just a small decrease in catalytic activi-
ty (96–84% for acetophenone; 98–81% for decanal). The cata-
lyst recovered from the five cycles with 1-phenylethanol was
further employed in a sixth and seventh cycle with 1-decanol
as the alcohol. Quantitative conversion to decanal was ob-
served in these two additional cycles (data not shown). Finally,
the possibility to decrease the catalyst loading was considered,
and the complete conversion of 1-phenylethanol (4 mmol) was
achieved by using 0.1 mol% of 4 (based on TEMPO) in a con-
centrated DCM solution (2 mL) with a longer reaction time
6
0
(4), this exotic octahedral polynitroxide system can also find
[25]
application in organic radical batteries, for magnetic reso-
[26]
nance and EPR imaging, or as a building block for the prepa-
ration of materials with magnetic, conducting, and optical
[27]
(
6 h).
We also recorded the EPR spectrum of 4 recovered after five
cycles in THF. The EPR spectrum is significantly different from
properties, among others.
that recorded from the fresh sample and exhibits a three-line Experimental Section
group as the main signal (Figure 3). This suggests that during
EPR spectroscopy
the catalytic cycles nitroxide units are in part converted to dia-
EPR spectra were recorded at RT by using an ELEXYS E500 spec-
magnetic units to lead to a dramatic decrease of the spin-ex-
change interaction between the 12 nitroxide units. Quantita-
tive analysis, performed by comparison of a doubly integrated
spectrum to a spectrum of a solution of 2,2-diphenyl-1-picryl-
hydrazyl (DPPH) of known concentration, indicated that after
five cycles the total amount of nitroxide was reduced to 24%.
As the catalyst still shows good activity after five cycles, it is
plausible that the nitroxide is converted to the diamagnetic ox-
oammonium form during the different catalytic cycles.
trometer equipped with a NMR gaussmeter to calibrate the mag-
netic field and a frequency counter for the determination of g fac-
tors. Nitroxide concentrations were measured with respect to a so-
lution of DPPH of known concentration using the signal from
a ruby crystal as internal standard.
Synthesis of C -TEMPO systems
60
Synthesis of 1: A solution of 4-hydroxy-TEMPO (3.55 mmol,
10 mg) in 1,2-dichloroethane (12 mL) in a single-necked round
bottom flask was degassed with dry Ar. Pyridine (3.55 mmol,
85 mL) was added to the solution at RT, and the reaction mixture
6
Conclusions
2
For the first time, fullerene has been employed successfully as
a molecular support in the preparation of C -2,2,6,6-tetrame-
was cooled to 08C. Then, malonyl chloride (1.77 mmol, 173 mL)
was added dropwise under Ar, and the solution was stirred at 08C
60
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1
for 1 h. The reaction mixture was left overnight at RT. A saturated
sion of the product was calculated by H NMR spectroscopy after
solution of NaHCO (15 mL) was added to the mixture, which was
careful determination of its weight.
3
extracted with DCM (3ꢁ20 mL). The combined organic layers were
dried over anhydrous Na SO and evaporated under reduced pres-
Oxidation with oxygen: A mixture of alcohol (0.8 mmol), tert-butyl
2
4
nitrite (15 mol%), and catalyst (1 mol% based on TEMPO) in H O
2
sure. The residue was purified by flash chromatography (SiO , ethyl
2
(0.5 mL) was prepared in a single-necked round-bottomed flask.
acetate/petroleum ether 2:8) to recover 450 mg (61%) of 1 as an
The flask was then filled with pure oxygen (balloon filled), and the
resulting mixture was stirred at 508C under an oxygen atmosphere.
orange solid. FTIR (film): n˜ =2977, 2940, 1735 (C=O), 1465 (NÀO),
À1
1
365, 1337, 1243, 1180, 1150, 1015, 1061 cm ; MS (EI): m/z: calcd
After 4 h, the reaction mixture was cooled to RT, and Et O (3ꢁ
2
for C H N O 412.2, found 412.4 m/z.
2
1
36
2
6
5
mL) was added. The mixture was stirred for 5 min, and the organ-
Synthesis of 2 and 3: To a solution of fullerene C60 (0.387 mmol,
79 mg), CBr (0.774 mmol, 257 mg), and 1 (0.387 mmol, 160 mg)
ic layers were separated and dried over anhydrous Na SO . The sol-
2
4
2
vent was removed under reduced pressure to give the crude prod-
uct, which was purified by simple filtration through a pad of silica
(AcOEt/petroleum ether). The conversion of the product was calcu-
4
in chlorobenzene (22 mL), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU;
.55 mmol, 236 mL) was added at RT, and the mixture was stirred
1
1
for 24 h. The crude product was purified by column chromatogra-
phy (SiO ), unreacted C was recovered by hexane/toluene (3:1),
lated by H NMR spectroscopy after careful determination of its
weight.
2
60
whereas the monoadduct 2 was eluted with DCM and dried under
reduced pressure. Subsequently, 3 was eluted with DCM/MeOH
Oxidation with NaClO (Anelli): A mixture of alcohol (0.8 mmol),
catalyst (1 mol% based on TEMPO), and aq KBr (0.16 mL, 0.5m) in
DCM (2 mL) was prepared in a single-necked flask. The mixture
was cooled to 08C, NaOCl (2.86 mL, 0.35m) was added, and the so-
(
2
9:1) and dried under reduced pressure. Finally, pure 2 (124 mg,
8%) and 3 (29 mg, 10%) were collected after precipitation from
CHCl with MeOH as dark solids.
3
lution was buffered to pH 8.6 with NaHCO (108 mg). The biphasic
3
Compound 2: FTIR (KBr): n˜ =2973, 2936, 1747 (C=O), 1465 (NÀO),
reaction mixture was stirred vigorously, and the temperature of the
solution was maintained between 0–158C until total consumption
of the starting alcohol (TLC). The solution was diluted with DCM
À1
1
364, 1231, 1177, 1114, 1061, 740, 705, 527 cm (C ); MS (ESI): m/
60
+
z: calcd for C H N O ·H 1131.1, found 1131.2.
8
1
34
2
6
(
3ꢁ10 mL), and the organic layer was separated by extraction and
Compound 3: FTIR (KBr): n˜ =2976, 2939, 1746 (C=O), 1464 (NÀO),
dried over anhydrous Na SO . The solvent was removed under re-
À1
2
4
1
2
1
7
364, 1231, 1180, 1107, 1057, 740, 527 cm (C ); UV (CHCl ): l=
60
3
duced pressure to give the crude compound, which contained the
catalyst and the carbonyl compound. The crude compound was
further purified by simple filtration through a pad of silica, and the
+
58, 324, 426, 474 nm; MS (ESI): m/z: calcd for C H N O ·H
102 68
4
12
2+
542.6, found 1542.7; calcd for [C102H N O ·2H] 772.2, found
68
4
12
72.1.
1
conversion of the product was calculated by H NMR spectroscopy
Synthesis of 4: To a solution of fullerene C60 (0.0833 mmol, 60 mg),
after careful determination of its weight.
CBr (4.165 mmol, 1.38 g), and 1 (0.833 mmol, 345 mg) in chloro-
4
benzene (9.2 mL), DBU (1.667 mmol, 250 mL) was added at RT, and
the mixture was stirred for 72 h. The crude solution was purified
by column chromatography (SiO ); unreacted C was recovered by
using hexane/toluene (3:1), excess 1 was recovered with DCM/
MeOH (9:1), and the desired compound 4 was eluted with DCM/
MeOH (8:2). After removal of the solvent under reduced pressure,
the pure product was precipitated from CHCl3 with hexane to
afford 140 mg (54%) of an orange solid. FTIR (KBr): n˜ =2975, 2938,
Recycling procedure
2
60
The crude collected in the first cycle, after extraction and drying,
was concentrated to a 1–2 mL volume and seeded in a short silica
pad. Then, after atmospheric evaporation of the solvent, the car-
bonyl compound was isolated by elution with diethyl ether/petro-
leum ether (2:8), and the catalyst was recovered quickly with a mix-
ture of methanol/ethyl acetate (2:8). The removal of the solvent al-
lowed the recycling of the catalyst.
1
5
744 (C=O), 1634, 1464 (NÀO), 1365, 1225, 1178, 964, 714,
À1
28 cm (C ); UV (CHCl ): l=246, 279, 342 nm; MS (ESI): m/z
6
0
3
+
calcd for C186H204N O ·Na 3206.4, found 3206.1; calcd for
12
36
2
+
[
C186H204N O ·Na ] 1614.4, found 1614.5.
12 36 2
Acknowledgements
Preparation of reduced 4 (N-hydroxylamine form): To 4 (10 mg,
.1 mmol), a 1:1 mixture of acetone/water (2 mL) and 85% Na S O
3
2
2
4
Financial support from the University of Palermo, the University
of Bologna, and COST Action CM0905 ORCA are gratefully
acknowledged.
(
0.7 mg, 3.4 mmol) were added. After stirring for 0.5 h at RT, ace-
tone was removed under reduced pressure. The remaining aque-
ous solution was extracted with diethyl ether. The organic layers
were dried over anhydrous Na SO . The solution was filtered, and
2
4
the solvent was removed under reduced pressure. The so-obtained
sample was employed to record NMR spectra. H NMR (250 MHz,
Keywords: alcohols
organocatalysis · oxidation · TEMPO
·
EPR spectroscopy
·
fullerenes
·
1
CDCl ): d=3.79 (bs, 12H), 2.67 (s, 24H), 2.94 (s, 24H), 1.29 ppm (s,
3
1
44H).
[
1] a) J. E. Bꢂckvall, Modern Oxidation Methods, 2nd ed., Wiley-VCH, Wein-
heim, 2010; b) M. Hudlicky in Oxidations in Organic Synthesis, ACS Mon-
ograph 186, Washington DC, 1990; c) S. Jammi, T. Punniyamurthy,
G. B. W. L. Ligthart, R. H. Meijer, J. V. Buijtenen, J. Meuldijk, J. A. J. M. Ve-
kemans, L. A. Hulshof, K. Kittigowittana, M. Pohmakotr, V. Reutrakul, C.
Kuhakarn, Regio- and Stereo- Controlled Oxidations and Reductions,
Vol. 5, Wiley, Chichester 2007.
General procedures for oxidation
Oxidation with BAIB: BAIB (0.88 mmol) was added to a solution of
alcohol (0.8 mmol) and catalyst (1 mol% based on TEMPO) in DCM
(
2 mL). The reaction mixture was stirred at RT and monitored by
[
2] a) P. L. Anelli, S. Banfi, F. Montanari, S. Quici, J. Org. Chem. 1989, 54,
TLC. After 16 h the solvent was removed under reduced pressure
to obtain the crude product, which was purified by simple filtration
through a pad of silica (AcOEt/petroleum ether), and the conver-
2
970–2972; b) P. L. Anelli, C. Biffi, F. Montanari, S. Quici, J. Org. Chem.
1987, 52, 2559–2562; c) P. L. Anelli, F. Montanari, S. Quici, Org. Synth.
1990, 69, 212–219; d) M. Dagonneau, E. S. Kagan, V. I. Mikhailov, E. G.
ꢀ
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5
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ÞÞ
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CHEMCATCHEM
FULL PAPERS
www.chemcatchem.org
Rozantsev, V. D. Sholle, Synthesis 1984, 895–916; e) L. Tebben, A.
Studer, Angew. Chem. Int. Ed. 2011, 50, 5034–5068; Angew. Chem. 2011,
Chem. Phys. Lett. 2000, 330, 287–292; h) F. Conti, C. Corvaja, M. Maggi-
ni, G. Scorrano, P. Ceroni, F. Paolucci, S. Roffia, Phys. Chem. Chem. Phys.
2001, 3, 3518–3525; i) Y. Li, X. Lei, S. Jockusch, J. Y. C. Chen, M. Frunzi,
J. A. Johnson, R. G. Lawler, Y. Murata, M. Murata, K. Komatsu, N. J. Turro,
J. Am. Chem. Soc. 2010, 132, 4042–4043; j) Y. Li, X. Lei, R. G. Lawler, Y.
Murata, K. Komatsu, N. J. Turro, J. Phys. Chem. Lett. 2010, 1, 2135–2138;
k) S. Campestrini, C. Corvaja, M. De Nardi, C. Ducati, L. Franco, M. Maggi-
ni, M. Meneghetti, E. Menna, G. Ruaro, Small 2008, 4, 350–356.
[14] a) K. Matsuda, G. Ulrich, H. Iwamura, J. Chem. Soc. Perkin Trans. 2 1998,
1581–1588; b) T. Ishida, K. Shinozuka, M. Kubota, M. Ohashi, T. Nogami,
J. Chem. Soc. Chem. Commun. 1995, 1841–1842; c) T. Ishida, K. Shinozu-
ka, T. Nogami, M. Kubota, M. Ohashi, Tetrahedron 1996, 52, 5103–5112;
d) P. Ceroni, F. Conti, C. Corvaja, M. Maggini, F. Paolucci, S. Roffia, G.
Scorrano, A. Toffoletti, J. Phys. Chem. A 2000, 104, 156–163.
1
23, 5138–5174; f) T. Vogler, A. Studer, Synthesis 2008, 1979–1993;
g) R. A. Sheldon, I. W. C. E. Arends, Adv. Synth. Catal. 2004, 346, 1051–
071.
3] a) A. K. Tucker-Schwartz, R. L. Garrell, Chem. Eur. J. 2010, 16, 12718–
2726; b) M. Benaglia, A. Puglisi, O. Holczknecht, S. Quici, G. Pozzi, Tetra-
hedron 2005, 61, 12058–12064; c) C. Bolm, F. Thomas, Chem. Commun.
999, 1795–1796; d) R. Ciriminna, J. Blum, D. Avnir, M. Pagliaro, Chem.
1
[
1
1
Commun. 2000, 1441–1442; e) T. Dohi, K. I. Fukushima, T. Kamitanaka,
K. Morimoto, N. Takenaga, Y. Kita, Green Chem. 2012, 14, 1493–1501;
f) B. Karimi, A. Biglari, J. H. Clark, V. Budarin, Angew. Chem. Int. Ed. 2007,
46, 7210–7213; Angew. Chem. 2007, 119, 7348–7351; g) J. P. Lindner, C.
Roben, A. Studer, M. Stasiak, R. Ronge, A. Greiner, H. J. Wendorff,
Angew. Chem. Int. Ed. 2009, 48, 8874–8877; Angew. Chem. 2009, 121,
[15] a) L. Franco, M. Mazzoni, C. Corvaja, V. P. Gubskaya, L. S. Berezhnaya,
I. A. Nuretdinov, Appl. Magn. Reson. 2006, 30, 577–590; b) L. Franco, M.
Mazzoni, C. Corvaja, V. P. Gubskaya, L. Berezhnaya, I. A. Nuretdinov,
Chem. Commun. 2005, 2128–2130; c) V. P. Gubskaya, L. S. Berezhnaya,
V. V. Yanilkin, V. I. Morozov, N. V. Nastapova, Y. Y. Efremov, I. A. Nuretdi-
nov, Russ. Chem. Bull. 2005, 54, 1642–1655; d) V. P. Gubskaya, L. Berezh-
naya, A. T. Gubaidullin, I. I. Faingold, R. A. Kotelnikova, N. P. Konovalova,
V. I. Morozov, I. A. Litvinov, I. A. Nuretdinov, Org. Biomol. Chem. 2007, 5,
976–981.
[16] a) E. G. Rozantsev, V. A. Golubev, Izv. Akad. Nauk SSSR Ser. Khim. 1965,
718–719; b) C. Bosch-Navarro, F. Busolo, E. Coronado, Y. Duan, C. Marti-
Gastaldo, H. Prima-Garcia, J. Mater. Chem. C 2013, 1, 4590–4598.
[17] N. B. Mel’nikova, I. V. Gulyaev, M. V. Gulenova, A. A. Volkov, O. E. Zimnya-
kova, V. P. Gubskaya, L. S. Berezhnaya, A. T. Gubaidullin, I. A. Nuretdinov,
Russ. Chem. Bull. 2008, 57, 1955–1966.
9035–9038; h) A. Schꢂtz, R. N. Grass, W. J. Stark, O. Reiser, Chem. Eur. J.
2008, 14, 8262–8266; i) Y. Wang, X. Song, S. Shao, H. Zhong, F. Lin, RSC
Adv. 2012, 2, 7693–7698; j) J. A. M. Hepperle, F. Mitschang, A. K. Bier,
B. K. Dettlaff, A. Greiner, A. Studer, RSC Adv. 2013, 3, 25976–25981.
4] H. A. Beejapur, F. Giacalone, R. Noto, P. Franchi, M. Lucarini, M. Grutta-
dauria, ChemCatChem 2013, 5, 2991–2999.
[
[
[
[
5] M. Gruttadauria, F. Giacalone, R. Noto, Green Chem. 2013, 15, 2608–
2
618.
6] W. Krꢂtschmer, L. D. Lamb, K. Fostiropoulos, D. R. Huffman, Nature 1990,
47, 354–358.
7] a) N. S. Sariciftci, L. Smilowitz, A. J. Heeger, F. Wudl, Science 1992, 258,
474–1476; b) G. Yu, J. Gao, J. C. Hummelen, F. Wudl, A. J. Heeger, Sci-
3
1
ence 1995, 270, 1789–1791; c) G. Dennler, M. C. Scharber, C. J. Brabec,
Adv. Mater. 2009, 21, 1323–1338; d) J. Peet, J. Y. Kim, N. E. Coates, W. L.
Ma, D. Moses, A. J. Heeger, G. C. Bazan, Nat. Mater. 2007, 6, 497–500;
e) B. C. Thompson, J. M. J. Frꢃchet, Angew. Chem. Int. Ed. 2008, 47, 58–
[18] T. D. Lee, J. F. W. Keana, J. Org. Chem. 1975, 40, 3145–3147.
[19] J. E. Werz, J. R. Bolton, Electron Spin Resonance: Elementary Theory and
Practical Applications, Chapman and Hall, New York, 1986.
77; Angew. Chem. 2008, 120, 62–82.
[
8] a) R. Bakry, R. M. Vallant, M. Najam-ul-Haq, M. Rainer, Z. Szabo, C. W.
Huck, G. K. Bonn, Int. J. Nanomed. 2007, 2, 639–649; b) S. Bosi, T.
Da Ros, G. Spalluto, M. Prato, Eur. J. Med. Chem. 2003, 38, 913–923; c) T.
Da Ros, M. Prato, Chem. Commun. 1999, 663–669.
9] a) F. Giacalone, N. Martꢄn, Chem. Rev. 2006, 106, 5136–5190; b) F. Giac-
alone, N. Martꢄn, Adv. Mater. 2010, 22, 4220–4248.
[20] P. Neviani, E. Mileo, S. Masiero, S. Pieraccini, M. Lucarini, G. P. Spada,
Org. Lett. 2009, 11, 3004–3007.
[21] a) A. De Mico, R. Margarita, L. Parlanti, A. Vescovi, G. Piancatelli, J. Org.
Chem. 1997, 62, 6974–6977; b) O. Holczknecht, M. Cavazzini, S. Quici, I.
Shepperson, G. Pozzi, Adv. Synth. Catal. 2005, 347, 677–688; c) J. S.
Yadav, N. N. Yadav, T. Srinivasa Rao, B. V. Subba Reddy, A. A. K. Al Gham-
di, Eur. J. Org. Chem. 2011, 4603–4608.
[22] B. Karimi, E. Farhangi, Chem. Eur. J. 2011, 17, 6056–6060.
[23] R. A. Sheldon, J. K. Kochi, Metal-Catalyzed Oxidations of Organic Com-
pounds, Academic Press, New York, 1981.
[24] R. A. Sheldon, I. W. C. E. Arends, J. Mol. Catal. A 2006, 251, 200–214.
[25] a) H. Nishide, S. Iwasa, Y. J. Pu, T. Suga, K. Nakahara, M. Satoh, Electro-
chim. Acta 2004, 50, 827–831; b) H. Nishide, K. Oyaizu, Science 2008,
319, 737–738; c) K. Oyaizu, H. Nishide, Adv. Mater. 2009, 21, 2339–
2344.
[
[
10] a) S. Sarkar, M. L. Moser, X. Tian, X. Zhang, Y. F. Al-Hadeethi, R. C.
Haddon, Chem. Mater. 2014, 26, 184–195; b) C. Su, K. P. Loh, Acc. Chem.
Res. 2013, 46, 2275–2285; c) D. S. Su, S. Perathoner, G. Centi, Chem. Rev.
2
013, 113, 5782–5816; d) G. G. Wildgoose, C. E. Banks, R. G. Compton,
Small 2006, 2, 182–193; e) P. Serp, M. Corrias, P. Kalck, Appl. Catal. A
003, 253, 337–358; f) B. F. Machado, P. Serp, Catal. Sci. Technol. 2012,
, 54–75.
2
2
[
[
[
11] a) B. Coq, J. M. Planeix, V. Brotons, Appl. Catal. A 1998, 173, 175–183;
b) N. F. Goldshleger, Fullerene Sci. Technol. 2001, 9, 255–280.
12] H. Veisi, R. Masti, D. Kordestani, M. Safaei, O. Sahin, J. Mol. Catal. A
[26] a) A. A. Bobko, I. Dhimitruka, J. L. Zweier, V. V. Khramtsov, J. Am. Chem.
Soc. 2007, 129, 7240–7241; b) P. Kuppusamy, P. Wang, R. A. Shankar, L.
Ma, C. E. Trimble, C. J. C. Hsia, J. L. Zweier, Magn. Reson. Med. 1998, 40,
806–811; c) K. i. Matsumoto, H. Yakumaru, M. Narazaki, H. Nakagawa, K.
Anzai, H. Ikehira, N. Ikota, Magn. Reson. Imaging 2008, 26, 117–121;
d) B. P. Soule, F. Hyodo, K. i. Matsumoto, N. L. Simone, J. A. Cook, M. C.
Krishna, J. B. Mitchell, Free Radical Biol. Med. 2007, 42, 1632–1650.
[27] I. Ratera, J. Veciana, Chem. Soc. Rev. 2012, 41, 303–349.
2014, 385, 61–67.
13] a) Y. Li, Z. Mao, J. Xu, J. Yang, Z. Guo, D. Zhu, J. Li, B. Yin, Chem. Phys.
Lett. 1997, 265, 361–364; b) Z. Shi, J. Jin, Y. Li, Z. Guo, S. Wang, L. Jiang,
D. Zhu, New J. Chem. 2001, 25, 670–672; c) A. Polimeno, M. Zerbetto, L.
Franco, M. Maggini, C. Corvaja, J. Am. Chem. Soc. 2006, 128, 4734–
4741; d) C. Corvaja, M. Maggini, M. Prato, G. Scorrano, M. Venzin, J. Am.
Chem. Soc. 1995, 117, 8857–8858; e) F. Arena, F. Bullo, F. Conti, C. Corva-
ja, M. Maggini, M. Prato, G. Scorrano, J. Am. Chem. Soc. 1997, 119, 789–
795; f) F. Conti, C. Corvaja, A. Toffoletti, N. Mizuochi, Y. Ohba, S. Yamau-
chi, M. Maggini, J. Phys. Chem. A 2000, 104, 4962–4967; g) C. Corvaja, L.
Received: April 22, 2014
Franco, M. Mazzoni, M. Maggini, G. Zordan, E. Menna, G. Scorrano,
Published online on && &&, 0000
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FULL PAPERS
A great couple: Fullerene and 2,2,6,6-
tetramethylpiperidine-1-oxyl (TEMPO)
moieties combined in molecular assem-
blies give rise to excellent catalysts for
the oxidation of a wide range of alco-
hols. These hybrids are easily recycled
and maintain their activity after seven
cycles.
H. A. Beejapur, V. Campisciano, P. Franchi,
M. Lucarini, F. Giacalone,*
M. Gruttadauria*
&& – &&
Fullerene as a Platform for Recyclable
TEMPO Organocatalysts for the
Oxidation of Alcohols
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