The aerobic oxidation of alcohols with a ruthenium porphyrin catalyst in organic and fluorinated solvents

Article abstract of DOI:10.1039/b800583d

Carbonylruthenium tetrakis(pentafluorophenyl)porphyrin Ru(TPFPP)(CO) was utilized for the aerobic oxidation of alcohols. The in situ activation of the catalyst with mCPBA provided a species capable of catalyzing the oxidation of alcohols with molecular oxygen. The choice of solvent and additive was crucial to obtaining high activity and selectivity. Secondary aromatic alcohols were oxidized in the presence of the ruthenium porphyrin and tetrabutyl ammonium hydroxide in the solvent bromotrichloromethane, enabling high yields to be achieved (up to 99%). Alternatively, alcohols could be oxidized in perfluoro(methyldecalin) with the ruthenium porphyrin at higher temperatures (140 °C) and elevated oxygen pressures (50 psi). The Royal Society of Chemistry.

Full text of DOI:10.1039/b800583d

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
The aerobic oxidation of alcohols with a ruthenium porphyrin catalyst in
organic and fluorinated solvents
Vasily N. Korotchenko,a Kay Severinb and Michel R. Gagne´*a
Received 14th January 2008, Accepted 26th March 2008
First published as an Advance Article on the web 14th April 2008
DOI: 10.1039/b800583d
Carbonylruthenium tetrakis(pentafluorophenyl)porphyrin Ru(TPFPP)(CO) was utilized for the aerobic
oxidation of alcohols. The in situ activation of the catalyst with mCPBA provided a species capable of
catalyzing the oxidation of alcohols with molecular oxygen. The choice of solvent and additive was
crucial to obtaining high activity and selectivity. Secondary aromatic alcohols were oxidized in the
presence of the ruthenium porphyrin and tetrabutyl ammonium hydroxide in the solvent
bromotrichloromethane, enabling high yields to be achieved (up to 99%). Alternatively, alcohols could
be oxidized in perfluoro(methyldecalin) with the ruthenium porphyrin at higher temperatures (140 ◦C)
and elevated oxygen pressures (50 psi).
aerobic oxidation of alcohols. The stability of these halogenated
Introduction
derivatives to oxidative destruction and their modified redox
The oxidation of an alcohol to a carbonyl compound is an
potentials were properties that we hoped would successfully
overcome the inactivity of the 1st-generation catalyst. In this
article we outline our efforts to discover an active aerobic
oxidation catalyst, with an emphasis on deconvoluting the role of
ruthenium-catalyzed and autooxidation pathways. We document
experimental conditions under which either (and likely both)
mechanisms contribute to a highly efficient oxidation (quantitative
oxidation was documented at 0.01 mol% ruthenium loading).
The catalytic activity of 1 was examined for the aerobic
oxidation of benzhydrol 3 to benzophenone 4 in various solvents
under an O2 atmosphere (1 atm) at different temperatures (Table 1).
The conversion of 3 to 4 was monitored by 1H NMR of the
reaction mixture using tert-butylbenzene as an internal standard.
Complex 1 itself was almost inactive at 60 ◦C until oxidized to the
dioxoruthenium form 2 (entry 1). Complex 2 was prepared in situ
by oxidation of 1 wit◦h two equivalents of meta-chloroperbenzoic
acid (mCPBA) at 60 C and used without isolation (eqn 1).14
important transformation, and although there are many dif-
ferent methods for such functional group manipulations, cat-
alytic procedures that are environmentally friendly, atom ef-
ficient, and occur under aerobic conditions, are significantly
less common. The use of molecular oxygen as a stoichiometric
oxidant is very attractive since innocuous byproducts result
(H2O or H2O2).1 Modern, metal-catalyzed aerobic oxidation of
alcohols has recently been reviewed,2,3 and these reviews outline
significant progress in the elaboration of homogeneous and/or
heterogeneous catalysts in general, and in ruthenium catalysts in
particular.4,5 Since Groves’ pioneering discovery of the aerobic
epoxidation of olefins catalyzed by the cytochrome P450 analog
dioxo(tetramesitylporphyrinato)ruthenium,6 numerous investiga-
tions have focused on aerobic and anaerobic oxidative transfor-
mations catalyzed by ruthenium porphyrin complexes.7 Although
Hirobe8 andGroves9 havereportedhighturnovernumbers(TONs)
using 2,6-disubstituted pyridine-N-oxides as the stoichiometric
oxidant, similarly effective aerobic oxidations of alcohols remain
largely unreported.10,11
(1)
Results and discussion
We recently prepared an immobilized Ru(meso-tetraaryl-
porphyrin) complex and investigated its catalytic activity in the
epoxidation of olefins and oxidation of alcohols and alkanes using
2,6-dichloropyridine-N-oxide.12 Unfortunately, our attempts to
utilize this catalyst to mediate oxidation reactions using molecular
oxygen failed. Stimulated by the high performance of ruthenium
complexes in polyhalogenated porphyrins,8,9,13 we next studied
the catalytic activity of carbonylruthenium (tetrakispentafluo-
rophenyl)porphyrin Ru(TPFPP)(CO) 1 for the homogeneous
The choice of solvent was essential to the activity of the catalyst.
Hirobe8 and later Iida15 reported that the mineral acids HCl and
HBr could be used to enhance the activity of ruthenium porphyrin
complexes, presumably by forming more active halo–ruthenium
porphyrin complexes. Dihalogen ruthenium porphyrins can also
be prepared from carbonyl ruthenium precursors by reaction
with CCl4 or CBr4.9b,16 Che has improved the catalytic activity
of ruthenium carbonyl porphyrin by first refluxing in CCl4.17
In this contribution we report that CBrCl3 may also be used
as a soft non-acidic activator and solvent and that it can
improve the activation of the ruthenium porphyrin complex; non-
acidic activators being especially important for the oxidation of
aDepartment of Chemistry, University of North Carolina at Chapel Hill,
Chapel Hill, NC, 27599-3290, USA. E-mail: mgagne@unc.edu
b
´
Institut des Sciences et Inge´nieries Chimiques, Ecole Polytechnique Fe´de´rale
de Lausanne (EPFL), 1015, Lausanne, Switzerland
This journal is
The Royal Society of Chemistry 2008
Org. Biomol. Chem., 2008, 6, 1961–1965 | 1961
©

View Article Online
Table 1 Optimization of the catalytic system
Entry
Catalyst
Solvent/additives
Temperature/◦C
Time/h
Yield of 4 (%)a
1
2
3
4
5
1
CBrCl3
CCl4
CD3CN
PhCl
C4F9OMe–CBrCl3 (9 : 1, v/v)
CBrCl3
CBrCl3
60
60
60
100
60
60
80
100
90
100
90
90
18
4
4
4
4
4
1.5
2
2b
2b
2b
4
2b
<1
10
31
74
63
30
99
96
22
66
6
2b
3
7c
8c
9d
10d
11
12
13
14
2b
22
18
4
2b
CBrCl3
2b
CBrCl3–D2O–NaOD (250 mol%)
CBrCl3–D2O–NaOD (250 mol%)
CBrCl3–H2O–Bu4NOH (25 mol%)
CBrCl3–H2O–Bu4NOH (25 mol%)
CBrCl3–H2O–Bu4NOH (25 mol%)
CBrCl3–H2O–Bu4NOH (25 mol%)
2b
3
2b
24
24
24
24
1
(TPFPP)H2 + mCPBA
Fe(TPFPP)Cl + mCPBA
90
90
a Determined by 1H NMR, internal standard tert-butylbenzene, S/C ratio = 100. b Catalyst 2 prepared in situ from 1. c Conversion was accompanied by
the side products 5, 6, and 7. d Reaction stopped after destruction of ruthenium porphyrin.
acid-sensitive compounds. Of the studied solvents (Table 1, entries
2–6), only CBrCl3 provided significant oxidation of 3.
The combination of CBrCl3 and 2 was nearly inert without
O2, as demonstrated by heating 3 with CBrCl3 and catalyst 2 at
100 ◦C under argon. Analysis after 20 h showed a 4% conversion
to benzophenone, which could be attributed to stoichiometric
oxidation of 3 with dioxoruthenium complex 2. Catalytic ox-
idations of 3 to 4 in CBrCl3, however, were accompanied by
significant amounts of the undesirable 5, 6 and 7 (eqn 2).18 Higher
temperatures accelerated the oxidation (Table 1, entries 6–8) but
also increased the proportion of side products. These compounds
could be suppressed with an inorganic base (entries 9 and 10), but
at the cost of accelerated catalyst destruction. Catalyst longevity
could be recovered by adding an aqueous solution of Bu4NOH
(25 mol% to 3) to act as a phase transfer reagent and base. Under
these optimum conditions the selectivity increased to 99% (entry
11), and 1 did not need preactivation with mCPBA to be effective
(entry 12). Free porphyrin ligand (TPFPP)H2 and iron porphyrin
complex Fe(TPFPP)Cl are also catalytically active (entries 13 and
14), but observed conversions of 3 are less than for the ruthenium
catalyst.
Fig. 1 Oxidation of 3 to 4 with different S/C ratios.
completely suppressed (7% conversion at 48 h) in the dark even
with added benzophenone (entry 3). Repeating catalytic reactions
under the optimum conditions, but wrapped in foil, indicated
that the ruthenium-mediated oxidation was insensitive to light
(entries 4 and 5). BHT (2,6-di-tert-butyl-4-methylphenol) also
effectively terminated the autooxidation pathway (entry 6), while
it only inhibited the ruthenium-catalyzed oxidation (entry 7). The
outcome of these experiments were thus consistent with a scenario
wherein ruthenium-catalyzed oxidation occurs in parallel with,
and perhaps independent of, a radical chain autooxidation that
does not take place in the dark or in the presence of a radical
trap. Conditions could be engineered to exclude the autooxidation
pathway but under typical conditions it seems, at least for the
photo sensitizer benzophenone, that both pathways occur to some
degree.
This optimized catalytic system (Table 2, footnote a) was used in
the oxidation of a set of secondary alcohols (Table 3). To evaluate
the maximal turnover number (TON), experiments with decreas-
ing catalyst concentration (higher substrate to catalyst ratio, S/C)
were carried out. With a S/C ratio of 10 000, an 82% yield was
achieved for benzhydrol 3; even higher yields were observed for
8 and 10. The corresponding ketones 4, 9, and 11 were isolated
in high yields. 4,4ꢀ-Dimethoxybenzhydrol 12 also oxidized to the
ketone 13 in good yield; however, the oxidation was complicated
(2)
As shown in Fig. 1, the progression of the oxidation was
investigated at different loadings of catalyst. In each case an
induction period was observed and a relatively constant growth of
benzophenone ensued.
The viability of an autooxidation process was investigated
by similarly following the reaction in the absence of catalyst
(see Table 2). In this manner it was established that over the
first 24 h period, the autooxidation was much slower (6%
conversion) than with ruthenium (Fig. 1, entry 1 in Table 2).
When this same reaction was quantified after 65 h, however,
complete oxidation had occurred (entry 1). The autocatalytic
nature of this oxidation was traced to a benzophenone-mediated
photo-autooxidation under normal fumehood light (entry 2). It
was additionally established that the autooxidation was almost
1962 | Org. Biomol. Chem., 2008, 6, 1961–1965
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
Table 2 Control experiments outlining the role of autoxidation pathways
Entry
1
Catalyst
None
Conditionsa
Standard
Time/h
Yield of 4 (%)b
24
65
12
48
20
24
72
24
6
99
100
7
92
82
NR
61
2
3
4
5
6
7
None
None
2c,d
Standard + 25 mol% Ph2CO
Standard + 25 mol% Ph2CO, dark
Standard
2c,d
Dark
None
Dark + 10 mol% BHT
Dark + 10 mol% BHT
2c
a All reactions were performed with the standard conditions (0.2 mmol of 3, 10 mL of CBrCl3, 0.05 mL of 1 M aqueous solution of Bu4NOH) at 90 ◦C.
b Determined by 1H NMR, internal standard tert-butylbenzene. c Catalyst 2 was prepared in situ from 1. d S/C = 10 000.
Table 3 Oxidation of alcohols in the CBrCl3–Bu4NOH systema
Entry
Substrate
S/C
100
1000
10 000
1000
Yield of ketone (%)b
Product
1
2
3
4
3
3
3
95
4
4
4
99 (97c)
82
95 (92c)
8
8
9
9
5
6
10 000
1000
99
99 (98c)
10
10
11
11
7
8
10 000
1000
99
77 (73c)
12
a Alcohol (200 lmol), catalyst 2, CBrCl3 (10 mL), Bu4NOH 1 M aqueous solution (0.05 mL), 90 ◦C, 24 h. b Determined by 1H NMR, internal standard
tert-butylbenzene. c Isolated yield.
Table 4 Oxidation of alcohol 3 by oxygen in PFMD solvent
by the formation of unidentified side products. Oxidation of other
alcohols – 1-phenylethanol and benzyl alcohol – resulted in
complex product mixtures.
Entry
Catalysta
O2 pressure/psi
Temp./◦C
TON to 4
In addition to the above CBrCl3 activation approach, we sought
reaction conditions that might be less susceptible to autooxidation
pathways. Cognizant of the safety risks of hydrocarbon-based
solvents and knowing that highly fluorinated solvents have high
oxygen solubility (as well as being non-flammable),19 we developed
alter◦native conditions based on the relatively high boiling (137–
160 C) perfluoro(methyldecalin) PFMD. Like numerous fluori-
nated solvents, PFMD is immiscible with regular organic solvents
at room temperature and miscible at elevated temperatures, thus
facilitating the separation of products and the recovery of the
fluorous solvent.19 As before, the catalytic activity of 2 was
investigated with alcohol 3. Table 4 collects the data showing
that the catalytic activity of 2 was dependent on both reaction
temperature and oxygen pressure. Expressed as a TON (initial
S/C = 100), the conversion of 3 to 4 increased as the oxygen
pressure was increased from 12.5 to 25 to 50 psi (TONs 9, 28,
and 45, respectively). Increasing the temperature from 120 to
1
2
3
4
5
6
7
2
12.5
25
50
50
50
50
50
50
50
50
140
140
140
160
120
140
140
140
140
140
9
28
45
42
15
12
2
2
2
2
1
b
None
—
8c
9d
10e
2
2
2
35
27
15
a Catalyst 2 was prepared in situ from 1. b Only ether 7 was isolated.
c Benzophenone (10 mol%) was added. d BHT (10 mol%) was added.
e Reaction was carried out in the dark.
◦
140 C tripled the yield of ketone, but additional increases were
not beneficial. Under optimum conditions (140 ◦C, 50 psi of O2),
the unactivated ruthenium carbonyl catalyst 1 could be directly
used, but it was less effective (entry 6).
This journal is
The Royal Society of Chemistry 2008
Org. Biomol. Chem., 2008, 6, 1961–1965 | 1963
©

View Article Online
Table 5 Oxidation of alcohols in the PFMD systema
Experimental
Entry
Substrate
TONb
Product
General
The synthesis of complex 1 was performed as described.9b meta-
Chloroperbenzoic acid (mCPBA, 77%, Aldrich) was used without
purification. Perfluoro(methyldecalin) (PFMD, 80%, Aldrich)
was degassed by a standard freeze–pump–thaw procedure and
saturated with oxygen prior to use. The identity of the prod-
uct ketones were confirmed by comparison with commercially
1
2
3
4
3
45
99
42
68
4
8
9
10
12
11
13
a Alcohol (200 lmol), catalyst 2 (2 lmol, S/C = 100), PFMD (5 mL),
O2 (50 psi), 140 ◦C, 24 h. b Determined by H NMR, internal standard
1
tert-butylbenzene.
1
available compounds. H NMR analyses were performed on a
Bruker 400 MHz AVANCE spectrometer. The UV analyses were
performed with Hewlett Packard 8453 UV-Visible spectrometer.
An important component of reaction efficiency was
a
concurrent condensation process that converted into
3
In situ activation of ruthenium carbonyl porphyrin complex 1
tetraphenyldimethyl ether 7. In fact, only 7 and 4 were observed
at the completion of the reaction. This thermal process converts
the more reactive substrate into one that is considerably less so,
as demonstrated by oxidation reactions of the isolated ether 7
(12% conversion after 24 h). The condensation occurs quickly
in the absence of catalyst (<3 h at 140 ◦C). Hypothesizing
that accelerating the reverse hydration process might lead to a
more efficient oxidation process, the reaction was repeated with
added water, and a slight inhibition was observed (28% of 4
after 24 h); the high temperatures almost certainly help to drive
the dehydration. As described above, it was established that 3
quantitatively converted to 7 under heating without catalyst (entry
7); and most importantly no autooxidation was observed. Since
addition of benzophenone did not accelerate oxidation (entry
8), and reactions in the dark or in the presence of BHT were
only slowed (entries 9, 10), we propose a metal-catalyzed aerobic
oxidation under these conditions.
To evaluate the scope of this variant on the catalytic system,
we investigated the oxidation of a number of alcohols (Table 5).
Non-enolizable alcohols 3, 8, 10, and 12 were smoothly oxidized
to their corresponding ketones, fluorenol 8 being particularly well
behaved (entry 2). It is worth noting that no dimer analogous to
7 was observed with the other alcohols, and unreacted alcohol
was observed in these cases. Oxidation of other alcohols – 1-
phenylethanol and benzyl alcohol – resulted in the formation of
multiple products, although corresponding carbonyl compounds
were detected by 1H NMR. For example, benzaldehyde and ben-
zoic acid (along with other unidentified products) were observed
for benzyl alcohol.
Complex 1 (2.2 mg, 2 lmol) was first dissolved in CBrCl3 (5 mL)
at 60 ◦C (oil bath), and then mCPBA (0.9 mg, 4 lmol) was added
in one portion to the solution. At 60 ◦C complete oxidation of
1 to dioxoruthenium complex 2 required only a few seconds. The
oxidation could be monitored by UV/Vis or more routinely by the
color change from crimson to brown. The solution of 2 was used
within 1 hour of preparation.
General procedure for the oxidation of alcohols in CBrCl3
To a catalyst solution, containing 2 lmol (S/C ratio = 100), 0.2
lmol (S/C ratio = 1000) or 0.02 lmol (S/C ratio = 10 000) of 2
in CBrCl3 (10 mL), prepared by dilution of the stock solution (see
above), was added an aqueous solution of tetrabutylammonium
hydroxide (50 lmol, 50 lL of a 1 M solution) and substrate
(200 lmol). Oxygen was bubbled through the reaction mixture for
◦
◦
15 min while heating to 90 C. The mixture was stirred at 90 C
for 24 h under an oxygen atmosphere (1 atm). After complete
consumption of starting material, the reaction mixture was
cooled to rt, concentrated under vacuum and chromatographed
(hexanes–EtOAc) to give the ketone.
General procedure for the oxidation of alcohols in
perfluoro(methyldecalin)
A catalyst solution, containing 2 lmol of 2 in chloroform (0.2 mL,
prepared as described above) was added to a high pressure glass
reaction vessel equipped with a pressure gauge, and diluted with
PFMD (5 mL). Alcohol (200 lmol, S/C ratio = 100) was added in
one portion, and the reaction vessel was then filled with oxygen (50
psi) and heated to 140 ◦C (oil bath). Once 140 ◦C was achieved, the
pressure was then released and the vessel was refilled with oxygen.
The reaction mixture was stirred at 140 ◦C under oxygen for 24 h,
the pressure was then released and the reaction mixture cooled to
room temperature. The organics were extracted with CDCl3 (2 ×
1 mL) and the mixture analyzed by 1H NMR.
Conclusions
In summary, we report that the combination of 2 with 25 mol%
Bu4NOH in CBrCl3 effectively oxidizes secondary alcohols to
ketones in good to excellent yields with molecular oxygen. Control
experiments indicated that under the optimum reaction conditions
ruthenium catalysis and autooxidation were both viable, though
conditions could be engineered (radical traps or absence of light)
wherein the autooxidation pathway was shut down and only
ruthenium catalysis converted alcohol to ketone, high turnover
efficiencies being achieved. Alternatively, these alcohols could be
oxidized using 2 and oxygen in a fluorinated solvent (PFMD).
Numerous control experiments suggested that autooxidation did
not occur under these modified conditions.
Acknowledgements
We gratefully acknowledge the Army Research Office (Grant #
W911NF0510081) and the Defense Threat Reduction Agency
(DTRA) for funding. KS thanks the Swiss National Science
Foundation and the EPFL for kind support.
1964 | Org. Biomol. Chem., 2008, 6, 1961–1965
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
(d) M. B. Ezhova and B. R. James, ‘Catalytic oxidation using ruthenium
porphyrins’, in Advances in Catalytic Activation of Dioxygen by Metal
References
1 Modern Oxidation Methods, ed. J.-E. Ba¨ckvall, Wiley-VCH, Weinheim,
2004.
´
Complexes, ed. L. I. Simandi, Kluwer Academic Publishers, London,
2003, pp. 1–77.
2 For general reviews, see: (a) R. A. Sheldon and I. W. C. E. Arends,
‘Catalytic oxidations of alcohols’, in Advances in Catalytic Activation
of Dioxygen by Metal Complexes, ed. L. I. Sima´ndi, Kluwer Academic
Publishers, London, 2003, pp. 123–155; (b) I. W. C. E. Arends and R. A.
Sheldon, ‘Modern oxidation of alcohols using environmentally benign
oxidants’, in Modern Oxidation Methods, ed. J.-E. Ba¨ckvall, Wiley-
VCH, Weinheim, 2004, pp. 83–118; (c) I. E. Marko´, P. R. Giles, M.
Tsukazaki, A. Gautier, R. Dumeunier, K. Doda, F. Philippart, I. Chelle´-
Regnault, J.-L. Mutonkole, S. M. Brown and C. J. Urch, ‘Aerobic,
metal-catalyzed oxidation of alcohols’, in Transition Metals for Organic
Synthesis (2nd edn), ed. M. Beller and C. Bolm, Wiley-VCH, Weinheim,
2004, pp. 437–478; (d) B.-Z. Zhan and A. Thompson, Tetrahedron,
2004, 60, 2917–2935; (e) T. Mallat and A. Baiker, Chem. Rev., 2004,
104, 3037–3058; (f) M. J. Schultz and M. S. Sigman, Tetrahedron, 2006,
62, 8227–8241; (g) M. S. Sigman and D. R. Jensen, Acc. Chem. Res.,
2006, 39, 221–229.
3 For Ru-catalyzed aerobic oxidations, see: (a) B. R. James, ‘Selective
oxidations with dioxygen catalyzed by ruthenium and rhodium com-
plexes’, in Dioxygen Activation and Homogeneous Catalytic Oxidation,
ed. L. I. Sima´ndi, Elsevier, Amsterdam, 1991, pp. 195–212; (b) T. Naota,
H. Takaya and S.-I. Murahashi, Chem. Rev., 1998, 98, 2599–2660; (c) M.
Pagliaro, S. Campestrini and R. Ciriminna, Chem. Soc. Rev., 2005, 34,
837–845.
8 (a) T. Higuchi, H. Ohtake and M. Hirobe, Tetrahedron Lett., 1989,
30, 6545–6548; (b) T. Higuchi, H. Ohtake and M. Hirobe, Tetrahedron
Lett., 1991, 32, 7435–7438; (c) H. Ohtake, T. Higuchi and M. Hirobe,
J. Am. Chem. Soc., 1992, 114, 10660–10662; (d) H. Ohtake, T. Higuchi
and M. Hirobe, Tetrahedron Lett., 1992, 33, 2521–2524; (e) H. Ohtake,
T. Higuchi and M. Hirobe, Heterocycles, 1995, 40, 867–903; (f) T.
Higuchi and M. Hirobe, J. Mol. Catal. A: Chem., 1996, 113, 403–
422.
9 (a) J. T. Groves, M. Bonchio, T. Carofiglio and K. Shalyaev, J. Am.
Chem. Soc., 1996, 118, 8961–8962; (b) C. Wang, K. V. Shalyaev, M.
Bonchio, T. Carofiglio and J. T. Groves, Inorg. Chem., 2006, 45, 4769–
4782.
10 TONs of about 1.5 per day have been realized for oxidation of
isopropanol: S. Y. S. Cheng, N. Rajapakse, S. J. Rettig and B. R. James,
J. Chem. Soc., Chem. Commun., 1994, 2669–2670.
11 The aerobic oxidation of alcohols in the presence of a sacrificial
reductant and a ruthenium porphyrin catalyst has been reported: H.-B.
Ji, Q.-L. Yuan, X.-T. Zhou, L.-X. Pei and L.-F. Wang, Bioorg. Med.
Chem. Lett., 2007, 17, 6364–6368. See also: M. T. Zhou, H.-B. Ji, Q.-L.
Yuan, J. C. Xu, L. Y. Pei and L.-F. Wang, Chin. Chem. Lett., 2007, 18,
926–928.
12 (a) O. Nestler and K. Severin, Org. Lett., 2001, 3, 3907–3909; (b) E.
¨
Burri, M. Ohm, C. Daguenet and K. Severin, Chem.–Eur. J., 2005, 11,
4 (a) I. E. Marko´, P. R. Giles, M. Tsukazaki, I. Chelle´-Regnault, C. J.
Urch and S. M. Brown, J. Am. Chem. Soc., 1997, 119, 12661–12662;
(b) N. Komiya, T. Nakae, H. Sato and T. Naota, Chem. Commun., 2006,
4829–4831; (c) F. Shi, M. K. Tse and M. Beller, Chem.–Asian J., 2007,
2, 411–415.
5 For the application of heterogeneous ruthenium catalysts in aerobic
oxidation of alcohols, see: (a) K. Yamaguchi and N. Mizuno, Angew.
Chem., Int. Ed., 2002, 41, 4538–4542; (b) K. Yamaguchi and N. Mizuno,
Chem.–Eur. J., 2003, 9, 4353–4361; (c) H.-Y. Shen, S.-C. Zhou, M.-H.
Wei and H.-X. Zong, React. Funct. Polym., 2006, 66, 827–831; (d) T.
Matsumoto, M. Ueno, J. Kobayashi, H. Miyamura, Y. Mori and S.
Kobayashi, Adv. Synth. Catal., 2007, 349, 531–534.
5055–5061; (c) E. Burri, S. M. Leader, K. Severin and M. R. Gagne´,
Adv. Synth. Catal., 2006, 348, 1640–1644; (d) E. Burri and K. Severin,
Chimia, 2006, 60, 182–184.
13 (a) S.-I. Murahashi, T. Naota and N. Komiya, Tetrahedron Lett., 1995,
36, 8059–8062; (b) E. R. Birnbaum, J. A. Labinger, J. E. Bercaw and
H. B. Gray, Inorg. Chim. Acta, 1998, 270, 433–439.
14 Formation of 2 in the oxidation of 1 with mCPBA was described
recently: see ref. 9b.
15 S. Ogawa, T. Iida, T. Goto, N. Mano, J. Goto and T. Nambara, Org.
Biomol. Chem., 2004, 2, 1013–1018.
16 Z. Gross and C. M. Barzilay, J. Chem. Soc., Chem. Commun., 1995,
1287–1288.
6 J. T. Groves and R. Quinn, J. Am. Chem. Soc., 1985, 107, 5790–5792.
7 For the reviews of ruthenium porphyrin catalyzed oxidations, see:
(a) B. Meunier, Chem. Rev., 1992, 92, 1411–1456; (b) T. Mlodnicka
and B. R. James, ‘Oxidations Catalyzed by Ruthenium Porphyrins’,
in Metalloporphyrins Catalyzed Oxidations, ed. F. Montanari and
L. Casella, Kluwer Academic Publishers, London, 1994, pp. 121–148;
(c) J. T. Groves, K. Shalyaev and J. Lee, ‘Oxometalloporphyrins in
oxidative catalysis’, in The Porphyrin Handbook, Vol. 4, ed. K. Kadish,
K. Smith and R. Guilard), Academic Press, New York, 2000, pp. 17–40;
17 R. Zhang, W.-Y. Yu, K.-Y. Wong and C.-M. Che, J. Org. Chem., 2001,
66, 8145–8153.
18 The identity of compounds 5–7 was established by the comparison of
their 1H NMR spectra with literature data: (a) L. J. Stangeland and J.
Songstad, Acta Chem. Scand., 1970, 24, 356–358; (b) K. J. Miller and
M. M. Abu-Omar, Eur. J. Org. Chem., 2003, 1294–1299.
19 (a) Handbook of Fluorous Chemistry, ed. J. A. Gladysz, D. P. Curran
and I. T. Horvath, Wiley-VCH, Weinheim, 2004; (b) E. P. Wesseler, R.
Iltis and L. C. Clark, Jr., J. Fluorine Chem., 1977, 9, 137–146.
This journal is
The Royal Society of Chemistry 2008
Org. Biomol. Chem., 2008, 6, 1961–1965 | 1965
©