Ruthenium porphyrin-catalyzed aerobic oxidation of terminal aryl alkenes to aldehydes by a tandem epoxidation-isomerization pathway

Article abstract of DOI:10.1002/anie.200801500

(Figure Presented) Catalytic oxidation of 1-alkenes to aldehydes by an epoxidation-isomerization pathway with air or dioxygen as terminal oxidant has been realized for bulky ruthenium(VI) porphyrin catalysts. For the new, recyclable catalyst [Ru^VI(tmttp)O₂], product yields of up to 99% and total turnover numbers of up to 1144 were obtained.

Full text of DOI:10.1002/anie.200801500

Communications
DOI: 10.1002/anie.200801500
Aerobic Oxidation
Ruthenium Porphyrin-Catalyzed Aerobic Oxidation of Terminal Aryl
Alkenes to Aldehydes by a Tandem Epoxidation–Isomerization
Pathway**
Gaoxi Jiang, Jian Chen, Hung-Yat Thu, Jie-Sheng Huang, Nianyong Zhu, and Chi-Ming Che*
Metal-catalyzed selective oxidation of organic substrates
under mild conditions, with dioxygen or air as the sole
terminal oxidant, is an economic and green methodology for
the synthesis of epoxides, alcohols, ketones, and aldehydes.[1]
gives a mixture of aldehydes and methyl ketones or otherwise
affords aldehyde in approximately 10% yield.[5a]
Several years ago, we reported a version of Reaction (1)
(Scheme 1, R = aryl), catalyzed by ruthenium porphyrin and
employing 2,6-dichloropyridine N-oxide (2,6-Cl2pyNO) as
terminal oxidant. The ruthenium-porphyrin-catalyzed alde-
hyde formation reaction proceeded by a tandem epoxidation–
isomerization (E–I) pathway, affording aldehydes in up to
99% yield with the catalyst [RuIV(tmp)Cl2] (1a, tmp =
5,10,15,20-tetramesitylporphyrinato dianion) or [RuIV(2,6-
Cl2tpp)Cl2] (1b, 2,6-Cl2tpp = 5,10,15,20-tetrakis(2,6-dichloro-
=
For catalytic oxidation of 1-alkenes to aldehydes without C C
bond cleavage (Reaction (1), Scheme 1), a widely known
Scheme 1. General scheme for the metal-catalyzed oxidation of 1-
alkenes to aldehydes;ML n =metal catalyst, [O]=oxidant.
phenyl)porphyrinato dianion) (Reaction (2), Scheme 2).[6]
A
industrial process is the Wacker oxidation of ethylene to
acetaldehyde catalyzed by PdCl2, with CuCl2 and dioxygen as
oxidants.[2] Extension of the Wacker process, or its recent
modifications, to higher 1-alkenes using dioxygen as the sole
terminal oxidant,[3] usually affords methyl ketones instead of
aldehydes. A reversal of such selectivity (methyl ketone vs.
aldehyde) has been noted in the Wacker oxidation of 1-
alkenes functionalized with vicinal heteroatoms, or 1,5-
dienes,[4,5a–f] and in recently reported PdCl2-catalyzed Reac-
tion (1) (Scheme 1, R = aryl) using heteropolyacid
H4[PMo11VO40] as a terminal oxidant.[5g] The Wacker oxida-
tion of unfunctionalized 1-alkenes in tertiary alcohols[5a,d]
Scheme 2. Ruthenium porphyrin-catalyzed oxidation of 1-alkenes to
aldehydes (E–I reaction).
[*] G. Jiang, Dr. J. Chen, Prof. Dr. C.-M. Che
Shanghai-Hong Kong Joint Laboratory in Chemical Synthesis
Shanghai Institute of Organic Chemistry, The Chinese Academy of
Sciences
great challenge subsequently faced is to develop a similar
tandem E–I reaction with air or dioxygen, instead of 2,6-
Cl2pyNO, as terminal oxidant (Reaction (3), Scheme 2).[7]
Herein we report the first examples of an aerobic E–I
reaction (Reaction (3), Scheme 2), which gave aldehydes in
up to 94% yield using catalyst 1a or [RuVI(tmp)O2] (2a,
Scheme 3), and with up to 1144 product turnovers (after
354 Feng Lin Road, Shanghai 200032 (China)
E-mail: cmche@hku.hk
Dr. H.-Y. Thu, Dr. J.-S. Huang, Dr. N. Zhu, Prof. Dr. C.-M. Che
Department of Chemistry and
Open Laboratory of Chemical Biology of the Institute of Molecular
Technology for Drug Discovery and Synthesis
The University of Hong Kong
Pokfulam Road, Hong Kong
Fax: (+852)28571586
[**] We are thankful for the financial support of The University of Hong
Kong (University Development Fund), the University Grants Council
of HKSAR (the Area of Excellence Scheme: AoE 10/01P), the Hong
Kong Research Grants Council (HKU7009/06P and CityU 2/06C),
and CAS-Croucher Funding Scheme for Joint Laboratory. G.J. and
J.C. thank the Croucher Foundation of Hong Kong for a postgrad-
uate studentship.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.200801500.
Scheme 3. Dioxoruthenium(VI) porphyrin catalysts 2a–c.
6638
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2008, 47, 6638 –6642

Angewandte
Chemie
recycling the catalyst five times) by employing a new
ruthenium porphyrin catalyst [RuVI(tmttp)O2] (2c,
Scheme 3, tmttp = 1,3,5,7-tetramethyl-2,4,6,8-tetraterphenyl-
porphyrinato dianion), thus providing a unique example of an
efficient metal-catalyzed analogue of Reaction (1)
(Scheme 1) at ambient temperature and pressure with
dioxygen as the sole terminal oxidant.
In previous work,[6] the oxidation of p-methoxystyrene
(3a) by 2,6-Cl2pyNO in CDCl3, catalyzed by 1b (2 mol%) at
258C for 0.5 h, afforded 2-(4-methoxyphenyl)-acetaldehyde
(4a, Scheme 4) in 99% yield. However, a similar aerobic
reaction in CDCl3 using catalyst 1b or 1a (2 mol%) in the
absence of 2,6-Cl2 pyNO for 7 days gave only a trace amount
Scheme 4. Aerobic oxidation of 3a to 4a catalyzed by 1a and 2a.
Table 1: Aerobic oxidation of 1-alkenes catalyzed by 1a.[a]
1
of 4a, as revealed by H NMR spectroscopy. Neither raising
the temperature to 608C nor irradiating the mixture with light
increased the yield of 4a.
Strikingly, upon addition of a solution of NaHCO3
(4 mol%) in water (0.3 mL), the aerobic oxidation of 3a
(0.1 mmol) in CDCl3 (1 mL) with 1a as catalyst gave 4a in
94% yield after 7 h (Reaction (4), Scheme 4). The aqueous
NaHCO3 solution seemingly served as a “switch” in the 1a-
catalyzed aerobic oxidation, the presence of which allowed
aldehyde formation to proceed. By using 4 mol% of other
additives, such as 2,6-dichloropyridine, triethylphosphite,
trifluoroacetic acid, or aqueous hydrochloric acid, instead of
aqueous NaHCO3, no 4a was detected in the reaction mixture
after at least 9 h.
Examination of the solvent effect revealed chloroform as
the solvent of choice. Changing the solvent to dichloro-
methane and 1,2-dichloroethane lowered the yield of 4a to
68% and 10%, respectively. No reaction was found when the
solvent was changed to benzene, toluene, acetone, diethyl
ether, or methanol. The effect of porphyrin ligands in the
catalysis has also been examined. Changing the catalyst from
1a to 1b led to the formation of 4a in less than 3% yield after
a 12 h reaction, in sharp contrast with the virtually identical
activity of 1a and 1b in catalyzing the 2,6-Cl2pyNO oxidation
of 3a to 4a.[6]
Entry Substrate
Product
Time Yield
[h]
[%][b]
1
2
3
4
4.5
92
7
5
4
87
87
89
5
7
93
6[c]
7[c]
8[c]
9[c]
5
5
7
7
84
81
71
69
Complex 2a was found to catalyze the aerobic oxidation
of 3a to give 4a in 61% yield after 6 h without the need for
added aqueous NaHCO3 (Reaction (5), Scheme 4).[8] At the
end of the catalytic process, the reaction mixture was found to
contain [RuII(tmp)(CO)], as encountered in other alkene
oxidations catalyzed by 2a[8a,d] and 1b.[6] Because 2a is less
stable than 1a, we used the latter as catalyst in subsequent
aerobic oxidation reactions.
10[c]
7
81
By employing 2 mol% catalyst 1a and 4 mol% NaHCO3,
the oxidation of alkoxy-substituted styrenes 3b–3 f with air
afforded 4b–4 f, respectively, in 87–93% yields within 4–7 h
(Table 1, entries 1–5).
Styrenes 3g–3l, bearing alkyl or halo substituents, can also
be converted into their respective aldehydes 4g–4l by aerobic
oxidation catalyzed by 1a. However, a higher reaction
temperature and higher loadings of catalyst 1a and additive
NaHCO3 were needed to obtain the aldehyde products in
good yields. Under the conditions of 3 mol% 1a, 8 mol%
NaHCO3, 0.3 mL H2O, and 508C, the oxidation of 3g–3l gave
aldehydes 4g–4l, respectively, in 69–84% yields within 5–7 h
(Table 1, entries 6–11).
71
11[c]
12[c]
13[c]
7
5
7
(64[d])
73
74
(68[d])
[a] Reaction conditions: substrate (0.1 mmol), 1a (2 mol%), CDCl3
(1 mL), NaHCO3 (4 mol%), H2O (0.3 mL), open to air, room temper-
ature. [b] Determined by 1H NMR spectroscopy. [c] 1a (3 mol%),
NaHCO3 (8 mol%), 508C. [d] Yield of isolated product.
Angew. Chem. Int. Ed. 2008, 47, 6638 –6642
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 6639

Communications
1-Vinylnaphthalene (3m) and its derivative 3n exhibited a
NaHCO3 with H2O18, the oxidation with air resulted in
approximately 72% incorporation of O18 in 4a (see the
Supporting Information). These results recall the dioxygen
pressure-independent epoxide yields reported by Groves and
Quinn,[8a] and the 81% O18-incorporation from H2O18 into the
epoxide product reported by Hirobe and co-workers[12] for the
2a-catalyzed aerobic epoxidation of alkenes. The active
intermediate for the epoxide isomerization step is unclear.
Examples of isomerization of epoxides to aldehydes in the
presence of metal catalysts, including an iron porphyrin
catalyst, have been reported in the literature.[13]
reactivity comparable to that of 3g–3l toward the 1a-
catalyzed aerobic oxidation, with the aldehydes 4m and 4n
being formed in 73% and 74% yields under similar con-
ditions (Table 1, entries 12 and 13).
The efficient aerobic oxidation of 3a to 4a catalyzed by 1a
in the presence of NaHCO3 (aq), along with previous reports
on the metalloporphyrin-catalyzed olefination of aldehydes
with ethyl diazoacetate (EDA) and triphenylphosphine
(PPh3),[9] prompted us to develop a “one-pot” olefination
process that features in situ generation of an aldehyde from
alkene oxidation with dioxygen, instead of 2,6-Cl2pyNO
employed in our earlier work.[6] Interestingly, when a mixture
of 3a (0.8 mmol), 1a (3 mol%), and NaHCO3 (aq, 10 mol%)
in CHCl3 was stirred under dioxygen (1 atm) at room
temperature for 5 h, followed by removal of the solvent and
subsequent treatment of the residue with PPh3 (1.2 equiv),
toluene (10 mL), and EDA (1.2 equiv) at 808C for 2 h, the
olefination product 5a was isolated in 71% yield (Reac-
tion (6), Scheme 5). A similar one-pot olefination of 3e
afforded 5b in 73% yield.
A comparison among the behavior of 1a, 2a, and [RuII-
(tmp)(CO)] toward the catalytic isomerization of epoxides to
aldehydes is given in the Supporting Information (Table S1).
Treatment of styrene oxide (0.1 mmol) with 2 mol% 1a in
CDCl3 (1 mL) at 508C for 6 h afforded phenylacetaldehyde in
over 98% yield. Under similar conditions, 2a is also an active
catalyst for this isomerization process, affording phenylace-
taldehyde in 62% yield after 3 h, accompanied by conversion
of 2a into [RuII(tmp)(CO)]. No phenylacetaldehyde was
formed by employing [RuII(tmp)(CO)] as catalyst. The
activity of 2a in catalyzing both aerobic epoxidation of
alkenes[8a] and epoxide isomerization to aldehyde can ration-
alize the formation of 4a from 2a-catalyzed aerobic oxidation
of 3a (Reaction (5), Scheme 4).
As the aqueous solution of NaHCO3 functioned as a
“switch” in the 1a-catalyzed aldehyde formation, we moni-
1
tored (by H NMR and IR spectroscopy) a solution of 1a
(approx. 2 mg) in CDCl3 (1 mL) open to air with and without
addition of NaHCO3 (aq). These experiments revealed the
formation of 2a in almost quantitative yield upon stirring the
solution of 1a with NaHCO3 (aq, 10 equiv, 0.3 mL) at room
temperature for 6.5 h; however, in the absence of NaH-
CO3 (aq), no 2a was formed. Evidently, the role of NaH-
CO3 (aq) in the 1a-catalyzed aldehyde formation is to
facilitate the oxidation of 1a to 2a by air during catalysis.
As complex 1b contains a less electron-rich porphyrin
ligand, its oxidation by air to 2b (Scheme 3) should be less
effective. Indeed, only ꢀ 10% yield of 2b was detected, by
1H NMR spectroscopy, in a CDCl3 solution of 1b mixed with
NaHCO3 (aq, 10 equiv) after the mixture was exposed to air
and stirred at room temperature for 12 h. Not surprisingly, 2b
exhibited a substantially lower activity than 2a in catalyzing
aerobic oxidation of 3a to 4a; only a 22% yield of 4a was
obtained under the conditions of catalyst (2 mol%), CDCl3
(1 mL), room temperature, 12 h. These factors could account
for the dramatic difference between the catalytic activity of
1a and 1b toward the aerobic oxidation of 3a.
Scheme 5. “One-pot” olefination reaction involving the aerobic oxida-
tion of 3 to 4 catalyzed by 1a.
To obtain an insight into the mechanism of the 1a-
catalyzed aerobic oxidation of alkenes with additive NaH-
CO3 (aq), we examined the course of the reaction for 3 f over
1
time by H NMR spectroscopy. The time course plot resem-
bles that previously reported for the 2,6-Cl2pyNO oxidation
of 1-alkene catalyzed by 1b through the E–I pathway (see the
Supporting Information, Figure S1).[6] These studies revealed
that the 1a-catalyzed oxidation of 3 f exhibited an induction
period of about 4 min, followed by the formation of 2a and
initiation of the alkene oxidation. [RuII(tmp)(CO)], gener-
ated in the reaction, exhibits no catalytic activity toward the
aldehyde formation.
In view of the stoichiometric alkene epoxidation[8a,10] and
catalytic aerobic alkene epoxidation[8a–d,11] by dioxoruthe-
nium(VI) porphyrins, including those using 2a, pioneered by
Groves and Quinn,[8a] we propose that aldehyde formation
from the aerobic oxidation of 3, catalyzed by 1a, proceeds by
a tandem E–I mechanism, in which 2a, generated in situ from
the oxidation of 1a by air, is mainly responsible for the
epoxidation step. Indeed, for the 1a-catalyzed oxidation of 3a
in the presence of aqueous NaHCO3, the yield of 4a did not
depend on the dioxygen pressure when dioxygen was used as
terminal oxidant, and by replacing H2O16 of aqueous
Given the inactivity of [RuII(tmp)(CO)] and the insta-
bility of 2a for aerobic oxidation of alkenes as described by
Groves and Quinn,[8a] and for the aerobic E–I reactions as
described above, the formation of [RuII(tmp)(CO)] is a step
accounting for the deactivation of catalysts 1a and 2a in
aerobic oxidations of alkenes. For Reaction (3) (Scheme 2)
catalyzed by 1a or 2a, the product turnovers are less than 50
under the employed reaction conditions. We envisaged that
the modified bis-pocket porphyrin ligand tmttp, first reported
by Chang and co-workers,[14] could be better than tmp in the
design of sterically encumbered robust ruthenium catalysts.
6640 www.angewandte.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2008, 47, 6638 –6642

Angewandte
Chemie
Therefore we prepared [RuII(tmttp)(CO)(H2O)] (see the
Supporting Information) and determined its structure by X-
ray crystallography[15] (Figure 1). Oxidation of [RuII-
(tmttp)(CO)(H2O)] with m-chloroperbenzoic acid (m-
CPBA) gave 2c (Scheme 3), which was characterized by
1H NMR, UV/Vis, and IR spectroscopy and mass spectrom-
etry.[16]
Table 2: Catalyst recycling for oxidation of 3a to 4a with dioxygen
catalyzed by 2c.[a]
Entry
Recycle
Time [h]
Yield [%][b]
Total TON[c]
1
2
3
4
5
6
5
5
5
6
6
8
99
97
96
96
94
90
198
392
584
776
964
1st
2nd
3rd
4th
5th
1144
[a] Reaction conditions: 3a (0.1 mmol), 2c (0.5 mol%), CDCl3 (1 mL) for
initial reaction (entry 1); m-CPBA (2.5 mol%) in CDCl3 (0.1 mL) and 3a
(0.1 mmol) were sequentially added to start each recycle. [b] Determined
by 1H NMR spectroscopy. [c] Total number of product turnovers.
catalytic aerobic oxidation reactions, which exhibits > 1000
product turnovers after recycling the catalyst five times. The
presence of an aqueous NaHCO3 solution plays a pivotal role
in aldehyde formation from the aerobic oxidation catalyzed
by dichlororuthenium(IV) complex 1a.[17] To our knowledge,
the present work provides the first example of selective
aldehyde formation from 1-alkenes by a metal-catalyzed
tandem epoxidation–isomerization reaction with air as the
terminal oxidant,[18] a catalytic process complementing the
conventional Wacker oxidations that usually afford methyl
ketones.
Figure 1. ORTEP drawing for [RuII(tmttp)(CO)(H2O)]. Hydrogen atoms
are omitted for clarity;ellipsoids are set at 30% probability.
By using 2c (0.2 mol%) as catalyst with dioxygen (1 atm)
as terminal oxidant, product turnovers of 396, 377, 368, 243,
and 320 were obtained for the oxidation of 3a, 3g, 3h, 3j, and
3k to 4a, 4g, 4h, 4j, and 4k, respectively, in CDCl3 at 608C for
7 or 12 h (see the Supporting Information). No other products
of alkene oxidation were detected in the reaction mixtures by
1H NMR spectroscopy. These product turnovers are signifi-
cantly higher than those (< 50) obtained for the 2a- or 1a-
catalyzed oxidations. For the oxidation of 3a to 4a by
dioxygen catalyzed by 0.5 mol% 2c at 608C, [RuII-
(tmttp)(CO)] was formed in nearly quantitative yield
(approx. 96%) at the end of the reaction, which contrasts
with the approximately 70% yield of [RuII(tmp)(CO)]
formed from the same reaction catalyzed by 2 mol% 2a at
room temperature.
Catalysts 2c and 2a can be recycled by oxidation of their
deactivated forms [RuII(tmttp)(CO)] and [RuII(tmp)(CO)],
respectively, with m-CPBA (see the Supporting Information).
In the case of the oxidation of 3a with dioxygen, catalyzed by
2 mol% 2a at room temperature, which gave 4a in 67% yield
after 12 h, the first recycle decreased the yield of 4a to 49%
(reaction time: 20 h). In contrast, for the same reaction
catalyzed by 0.5 mol% 2c at 608C, the catalyst can be
recycled five times without a significant decrease in the yield
of 4a, as shown in Table 2. The total number of product
turnovers after five recycles reaches 1144.
Received: March 31, 2008
Published online: July 24, 2008
Keywords: alkenes · homogeneous catalysis · N ligands ·
.
oxidation · ruthenium
[1] For examples, see: a) I. E. Markó, P. R. Giles, M. Tsukazaki,
S. M. Brown, C. J. Urch, Science 1996, 274, 2044 – 2046; b) J. M.
Thomas, R. Raja, G. Sankar, R. G. Bell, Nature 1999, 398, 227 –
230; c) C. L. Hill, Nature 1999, 401, 436 – 437; d) G.-J. ten Brink,
I. W. C. E. Arends, R. A. Sheldon, Science 2000, 287, 1636 –
1639; e) T. Punniyamurthy, S. Velusamy, J. Iqbal, Chem. Rev.
2005, 105, 2329 – 2363; f) M. D. Hughes, Y.-J. Xu, P. Jenkins, P.
McMorn, P. Landon, D. I. Enache, A. F. Carley, G. A. Attard,
G. J. Hutchings, F. King, E. H. Stitt, P. Johnston, K. Griffin, C. J.
Kiely, Nature 2005, 437, 1132 – 1135; g) S. S. Stahl, Science 2005,
309, 1824 – 1826; h) D. I. Enache, J. K. Edwards, P. Landon, B.
Solsona-Espriu, A. F. Carley, A. A. Herzing, M. Watanabe, C. J.
Kiely, D. W. Knight, G. J. Hutchings, Science 2006, 311, 362 – 365.
[2] J. Smidt, W. Hafner, R. Jira, R. Sieber, J. Sedlmeier, A. Sabel,
Angew. Chem. 1962, 74, 93 – 102; Angew. Chem. Int. Ed. Engl.
1962, 1, 80 – 88.
[3] Selected examples: a) G. J. ten Brink, I. W. C. E. Arends, G.
Papdogianakis, R. A. Sheldon, Chem. Commun. 1998, 2359 –
2360; b) T. Nishimura, N. Kakiuchi, T. Onoue, K. Ohe, S.
Uemura, J. Chem. Soc. Perkin Trans. 1 2000, 1915 – 1918; c) C. N.
Cornell, M. S. Sigman, J. Am. Chem. Soc. 2005, 127, 2796 – 2797;
d) T. Mitsudome, T. Umetani, N. Nosaka, K. Mori, T. Mizugaki,
K. Ebitani, K. Kaneda, Angew. Chem. 2006, 118, 495 – 499;
Angew. Chem. Int. Ed. 2006, 45, 481 – 485; e) C. N. Cornell, M. S.
Sigman, Org. Lett. 2006, 8, 4117 – 4120.
In summary, we have developed a ruthenium porphyrin-
=
catalyzed oxidation of 1-alkenes to aldehydes, without C C
bond cleavage, using ambient air as the sole terminal oxidant,
together with a new, recyclable ruthenium catalyst for such
Angew. Chem. Int. Ed. 2008, 47, 6638 –6642
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 6641

Communications
[4] For a recent review on aldehyde formation from Pd-catalyzed
[12] H. Ohtake, T. Higuchi, M. Hirobe, Heterocycles 1995, 40, 867 –
903.
oxidation of 1-alkenes, see: J. Muzart, Tetrahedron 2007, 63,
7505 – 7521.
[13] a) H. Alper, D. Des Roches, T. Durst, R. Legault, J. Org. Chem.
1976, 41, 3611 – 3613; b) R. Sudha, K. M. Narasimhan, V. G.
Saraswathy, S. Sankararaman, J. Org. Chem. 1996, 61, 1877 –
1879; c) S. Kulasegaram, R. J. Kulawiec, J. Org. Chem. 1997, 62,
6547 – 6561; d) B. C. Ranu, U. Jana, J. Org. Chem. 1998, 63,
8212 – 8216; e) K. Suda, K. Baba, S. Nakajima, T. Takanami,
Tetrahedron Lett. 1999, 40, 7243 – 7246; f) F. Martínez, C.
del Campo, E. F. Llama, J. Chem. Soc. Perkin Trans. 1 2000,
1749 – 1751.
[14] N. Bag, S. S. Chern, S.-M. Peng, C.-K. Chang, Tetrahedron Lett.
1995, 36, 6409 – 6412.
[15] CCDC 683003 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre at www.ccdc.cam.
ac.uk/data_request/cif.
[5] Selected examples: a) B. L. Feringa, J. Chem. Soc. Chem.
Commun. 1986, 909 – 910; b) A. K. Bose, L. Krishnan, D. R.
Wagle, M. S. Manhas, Tetrahedron Lett. 1986, 27, 5955 – 5958;
c) T. Hosokawa, S. Aoki, M. Takano, T. Nakahira, Y. Yoshida, S.-
I. Murahashi, J. Chem. Soc. Chem. Commun. 1991, 1559 – 1560;
d) T. T. Wenzel, J. Chem. Soc. Chem. Commun. 1993, 862 – 864;
e) H. Pellissier, P.-Y. Michellys, M. Santelli, Tetrahedron Lett.
1994, 35, 6481 – 6484; f) T.-L. Ho, M. H. Chang, C. Chen,
Tetrahedron Lett. 2003, 44, 6955 – 6957; g) J. A. Wright, M. J.
Gaunt, J. B. Spencer, Chem. Eur. J. 2006, 12, 949 – 955.
[6] J. Chen, C.-M. Che, Angew. Chem. 2004, 116, 5058 – 5062;
Angew. Chem. Int. Ed. 2004, 43, 4950 – 4954.
[7] Note that a ruthenium perhalogenated porphyrin complex,
[RuII(tfppCl8)(CO)] (tfppCl8 = octachlorotetrakis(pentafluoro-
phenyl)porphyrinato dianion) can catalyze aerobic oxidation
of styrene at room temperature to primarily afford an aldehyde.
[16] Spectroscopic data for 2c: 1H NMR (400 MHz, CDCl3): dH =
9.61 (s, 4H), 7.85–7.80 (m, 12H), 7.09–7.06 (m, 16H), 6.43–6.40
(m, 24H), 2.96 ppm (s, 12H); UV/Vis (CH2Cl2): lmax (log e) 418
(5.13), 517 (4.11), 550 nm (4.23); IR: n˜ = 820 cmÀ1 [n(RuO2)];
ESI MS: m/z 1411 (M+).
[17] Dichlororuthenium(IV) porphyrin can be conveniently pre-
pared by reaction of a carbonylruthenium(II) porphyrin with
CCl4. See: Z. Gross, C. M. Barzilay, J. Chem. Soc. Chem.
Commun. 1995, 1287 – 1288. One referee suggested that the
superiority of chlorinated solvents in the catalytic oxidation
reported in this work could be related to the fact that these
=
However, this process results in a complete C C bond cleavage
to give benzaldehyde. See: E. R. Birnbaum, J. A. Labinger, J. E.
Bercaw, H. B. Gray, Inorg. Chim. Acta 1998, 270, 433 – 439.
[8] For other types of 2a-catalyzed aerobic oxidation, such as alkene
epoxidation and amine dehydrogenation, see: a) J. T. Groves, R.
Quinn, J. Am. Chem. Soc. 1985, 107, 5790 – 5792; b) J.-C.
Marchon, R. Ramasseul, J. Chem. Soc. Chem. Commun. 1988,
298 – 299; c) M. Tavares, R. Ramasseul, J.-C. Marchon, B.
Bachet, C. Brassy, J.-P. Mornon, J. Chem. Soc. Perkin Trans. 2
1992, 1321 – 1329; d) B. Scharbert, E. Zeisberger, E. Paulus, J.
Organomet. Chem. 1995, 493, 143 – 147; e) A. J. Bailey, B. R.
James, Chem. Commun. 1996, 2343 – 2344.
solvents
could
recycle
some
of
the
ruthenium-
(carbonyl)complexes back to dichlororuthenium(IV) or related
species.
[9] a) G. A. Mirafzal, G. Cheng, L. K. Woo, J. Am. Chem. Soc. 2002,
124, 176 – 177; b) V. K. Aggarwal, J. R. Fulton, C. G. Sheldon, J.
de Vicente, J. Am. Chem. Soc. 2003, 125, 6034 – 6035; c) Y. Chen,
L. Huang, M. A. Ranade, X. P. Zhang, J. Org. Chem. 2003, 68,
3714 – 3717.
[10] a) W.-H. Leung, C.-M. Che, J. Am. Chem. Soc. 1989, 111, 8812 –
8818; b) R. Zhang, W.-Y. Yu, H.-Z. Sun, W.-S. Liu, C.-M. Che,
Chem. Eur. J. 2002, 8, 2495 – 2507; c) C.-M. Che, J.-L. Zhang, R.
Zhang, J.-S. Huang, T.-S. Lai, W.-M. Tsui, X.-G. Zhou, Z.-Y.
Zhou, N. Zhu, C. K. Chang, Chem. Eur. J. 2005, 11, 7040 – 7053.
[11] T.-S. Lai, R. Zhang, K.-K. Cheung, H.-L. Kwong, C.-M. Che,
Chem. Commun. 1998, 1583 – 1584.
[18] Currently we cannot exclude the possibility that small amounts
of the arylacetaldehydes 4 resulted from a direct oxidation of the
corresponding aryl alkenes rather than from isomerization of
epoxides. For examples of arylacetaldehyde formation from
direct oxidation of styrenes by oxoiron porphyrins or by
iodosylbenzene or hypochlorite in the presence of iron and
manganese porphyrin catalysts, see: a) J. T. Groves, R. S. Myers,
J. Am. Chem. Soc. 1983, 105, 5791 – 5796; b) J. P. Collman, T.
Kodadek, J. I. Brauman, J. Am. Chem. Soc. 1986, 108, 2588 –
2594; c) Z. Gross, S. Nimri, J. Am. Chem. Soc. 1995, 117, 8021 –
8022; d) Z. Gross, S. Nimri, C. M. Barzilay, L. Simkhovich, J.
Biol. Inorg. Chem. 1997, 2, 492 – 506.
6642 www.angewandte.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2008, 47, 6638 –6642