Improved procedure for ruthenium-catalyzed oxidative cleavage of alkenes with IG(OH)5

Article abstract of DOI:10.1080/00397910500328944

Oxidative cleavage of alkenes to carboxylic acids catalyzed by cis-[RuCl₂-(bipy)₂]·2H₂O in the presence of IO(OH)₅ has been studied in a biphasic (CH₃CN-CCl ₄-H₂O; 1:1:2 v/v) solvent system. Ruthenium tetraoxide seems to be the active catalyst species. Copyright Taylor & Francis LLC.

Full text of DOI:10.1080/00397910500328944

This article was downloaded by: [University of Saskatchewan Library]
On: 14 October 2014, At: 07:38
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office:
Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International
Journal for Rapid Communication of
Synthetic Organic Chemistry
Publication details, including instructions for authors and subscription
information:
http://www.tandfonline.com/loi/lsyc20
Improved Procedure for
Ruthenium‐Catalyzed Oxidative Cleavage of
Alkenes With IO(OH)5
Abdel Ghany F. Shoair a & Ramadan H. Mohamed a
a Department of Chemistry, Faculty of Science , Egypt
Published online: 21 Aug 2006.
To cite this article: Abdel Ghany F. Shoair & Ramadan H. Mohamed (2006) Improved Procedure for
Ruthenium‐Catalyzed Oxidative Cleavage of Alkenes With IO(OH)5 , Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 36:1, 59-64, DOI:
10.1080/00397910500328944
To link to this article: http://dx.doi.org/10.1080/00397910500328944
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)
contained in the publications on our platform. However, Taylor & Francis, our agents, and our
licensors make no representations or warranties whatsoever as to the accuracy, completeness, or
suitability for any purpose of the Content. Any opinions and views expressed in this publication
are the opinions and views of the authors, and are not the views of or endorsed by Taylor &
Francis. The accuracy of the Content should not be relied upon and should be independently
verified with primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities
whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial
or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or
distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use
can be found at http://www.tandfonline.com/page/terms-and-conditions

Synthetic Communicationsw, 36: 59–64, 2006
Copyright # Taylor & Francis LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500328944
Improved Procedure for Ruthenium-
Catalyzed Oxidative Cleavage
of Alkenes With IO(OH)5
Abdel Ghany F. Shoair and Ramadan H. Mohamed
Department of Chemistry, Faculty of Science, Egypt
Abstract: Oxidative cleavage of alkenes to carboxylic acids catalyzed by cis-[RuCl2-
.
(bipy)2] 2H2O in the presence of IO(OH)5 has been studied in a biphasic (CH3CN-
CCl4-H2O; 1 : 1 : 2 v/v) solvent system. Ruthenium tetraoxide seems to be the active
catalyst species.
Keywords: Alkenes, cleavage, oxoruthenates
INTRODUCTION
.
There are a number of systems in which RuCl3 nH2O has been used as a
catalyst for oxidative cleavage of alkenes to acids.[1–3] Wolfe et al.[1]
reported the oxidation of cyclohexene to adipic acid by stirring a solution of
.
cyclohexene in CH2Cl2 with an aqueous solution of RuCl3 nH2O and
NaOCl. The most widely used procedure is that reported by Carlesen
et al.,[2] in which cyclopentene was converted into glutaric acid by using
.
RuCl3 nH2O as catalyst with NaIO4 as a cooxidant in a biphasic CH3CN-
CCl4-H2O solution. Halostyrenes and haloalkenes were oxidized to their
acids using RuO2 nH2O with either NaIO4 or NaOCl as cooxidants.[3]
.
However, a disadvantage of these catalyst systems is the formation of
NaIO3 and/or NaCl during the oxidation reaction, and they are sparingly
Received in the UK March 17, 2005
Address correspondence to Abdel Ghany F. Shoair, Department of Chemistry,
Faculty of Science, 34517 Domiat El-gadida, Egypt. E-mail: shoairaksm@hotmail.
com
59

60
A. G. F. Shoair and R. H. Mohamed
soluble in water with the solvent quantity specified (5 cm3).[2,3] These solids
remain at the end of the reaction, making the workup difficult.
.
The complex cis-[RuCl2(bipy)2] 2H2O was used for the chemoselective
degradation of aromatic rings to acids with NaIO4 as a cooxidant[4] but
not for the oxidative cleavage of alkenes to acids. As a part of our continuing
study on the use of ruthenium catalysts for specific oxidation of
organic compounds,[5,6] we studied the use of the catalyst system
.
cis-[RuCl2(bipy)2] 2H2O/IO(OH)5 for the oxidative cleavage of alkenes to
acids with IO(OH)5 as cooxidant; in this system, the direct use of RuO4 is
avoided.
RESULTS AND DISCUSSION
.
Although the complex cis-[RuCl2(bipy)2] 2H2O has occasionally been used
for other oxidations, few experimental details are available.[4] We studied
.
the reaction of cis-[RuCl2(bipy)2] 2H2O with IO(OH)5 in a biphasic solvent
system for cleavage of alkenes to acids. After many trials, we found
.
that the catalyst system, cis-[RuCl2(bipy)2] 2H2O/IO(OH)5, is a highly
effective catalyst for oxidative cleavage of a number of linear and cyclic
alkenes at room temperature in a biphasic solvent (CH3CN-CCl4-H2O). In a
typical experiment, an aqueous solution of an excess amount of IO(OH)5
was added to a stirred solution of an alkene and a catalytic amount of cis-
.
[RuCl2(bipy)2] 2H2O in CCl4-CH3CN, where after stirring for 15 min the
brown color of the reaction mixture turned into pale yellow, which is due to
the formation of RuO4.
The results obtained for the oxidation of several alkenes by the
present catalyst system are summarized in Table 1. We found that the
yields of the acids are in the range of 70–92%. These results are comparable
.
to those previously reported by us for the use of the RuCl3 nH2O/IO(OH)5
catalyst system for oxidative cleavage of alkenes to acids,[6] and the
yields here are higher than those previously reported for other catalyst
system, [RuCl2(PPh3)3]/PhIO.[7] It was found that the procedure is
simple and easy to use, and the major product here is the corresponding
acid. Other products such as epoxides were detected but in a very low
yields (5%).
The attempts to use other cooxidants, such as NaIO4 and NaOCl, with
.
cis-[RuCl2(bipy)2] 2H2O under the same conditions for oxidative cleavage
of cyclohexene as representative example were all unsuccessful. We noticed
that the presence of acetonitrile in the solvent system improves the yields of
.
.
acids as has been observed for RuCl3 nH2O/IO(OH)5 and RuCl3 nH2O/
NaIO4 systems respectively.[2,6] Large-scale oxidation of alkenes to
acids can be attained by this catalyst system; for example, oxidation of
20 mmol of styrene gave 19 mmol of benzoic acid with the catalytic
turnover of 190.

Ruthenium-Catalyzed Oxidative Cleavage
61
.
Table 1. Oxidative cleavage of alkenes to carboxylic acids by cis-[RuCl2(bipy)2]
2H2O/IO(OH)5
Yield (%)
[TO]
Reaction
time (h)
Substrate
Product
Glutaric acid
85(170)
92(184)
2
2
Adipic acid
Suberic acid
Palmetic acid
75(150)
80(160)
2
2
Benzoic acid
Benzoic acid
90(180)
90(180)
2
2
Pentanoic acid
Hexanoic acid
90(180)
80(160)
2
2
Heptanoic acid
70(140)
2
Reaction conditions: alkene (2 mmol), catalyst (0.01 mmol), and periodic acid
(10 mmol) were added to a mixture of CCl4 : CH3CN : H2O (1 : 1 : 2 v/v), stirring
at room temperature for 2 h. TO ¼ turnover ¼ moles of the product/moles of the
catalyst.
NATURE OF THE ACTIVE SPECIES AND THE PROPOSED
MECHANISM
Because the precise mechanistic study for reactions containing low-valent
ruthenium complexes as catalysts suggests the formation of metal-oxo inter-
mediates,[8] we investigated the nature of the active species responsible for
the cleavage by carrying out the electronic spectrum for the reaction
mixture without addition of the substrate. We found that the electronic
spectra of both the aqueous and CCl4 layers showed the characteristic peaks
of RuO4 with attendant vibrational fine structure at about 463 nm and
387 nm for the organic layer (curve A) and at about 475 nm and 390 nm for
the aqueous layer (curve B) (Figure 1). Similar results were reported for the
oxoruthenate complexes containing RuO4.[9]

62
A. G. F. Shoair and R. H. Mohamed
.
Figure 1. Electronic spectrum of the catalyst system; cis-[RuCl2(bipy)2] 2H2O
(0.01 mmol) and IO(OH)5 (10 mmol) were added in a biphasic solvent system
[CH3CN (5 cm3), CCl4 (5 cm3), and H2O (10 cm3)] with stirring. The electronic spec-
trum of organic layer is A and the electronic spectrum of aqueous layer is B.
The oxidative cleavage of alkenes to acids by the present catalyst system
is likely to proceed through a similar mechanism as that suggested for
RuO4.[10] In this mechanism, the produced RuO4 cleaves the alkene to acid
and converted into RuO2, which in turn will be further oxidized to RuO4 by
excess IO(OH)5 according to the following equations.
Cis-½RuCl2ðbipyÞ2ꢀ þ 3 IOðOHÞ
!
RuO4
þ 3HIO3 þ 2bipy þ 2HCl þ55H2O
2 Cyclohexene þ RuO4
RuO2 þ 2 IOðOHÞ5
2 Cyclohexene epoxide þ RuO4
!
2 cyclohexene epoxide þ RuO2
RuO4 þ 2HIO3 þ 4H2O
2 adipic acid þ RuO2
!
!
Scheme 1. Catalytic cycle for oxidative cleavage of alkenes to acids by cis-[RuCl2(-
.
bipy)2] 2H2O/IO(OH)5.

Ruthenium-Catalyzed Oxidative Cleavage
63
This catalytic cycle will continue until all the substrate is completely
consumed (Scheme 1).
CONCLUSION
.
We conclude that the complex cis-[RuCl2(bipy)2] 2H2O can be used as an
effective catalyst for oxidative cleavage of alkenes to acids with IO(OH)5 as
a cooxidant at room temperature, and the active catalyst species seems to be
RuO4. This procedure can eliminate our current need for the use of stoichio-
metric oxidants.
EXPERIMENTAL
Instrumentation and Chemicals
Instrumentation
1
The H NMR spectra were made in CDCl3 solutions on a high-resolution
Bruker AM 300L spectrometer with tetramethylsilane (TMS) as internal
standard at Cairo University. The infrared spectra were recorded on a
Mattson 5000 FT-IR and the electronic spectra on a UV-visible vision
software V 3.2 at Mansoura University. Microanalysis was carried out at
Cairo University Microanalytical Unit.
Chemicals
All chemicals were obtained from Aldrich and used as received. The complex
[11]
.
cis-[RuCl2(bipy)2] 2H2O was prepared using Sullivan’s procedure.
Oxidative Cleavage of Alkenes
.
An alkene (2 mmol), cis-[RuCl2(bipy)2] 2H2O (0.01 mmol), and IO(OH)5
(10 mmol) were added in a biphasic solvent system [CH3CN (5 cm3), CCl4
(5 cm3), and H2O (10 cm3)] with stirring. The reaction mixture was stirred
at room temperature for the times specified in Table 1. The products were
extracted with diethylether (3 ꢁ 10 cm3), dried over MgSO4, and evaporated
under reduced pressure.
Large-Scale Oxidation of Styrene
Styrene (20 mmol) was added to a solution of CCl4 (50 cm3), CH3CN
(50 cm3), and H2O (100 cm3) containing IO(OH)5 (100 mmol) and

64
A. G. F. Shoair and R. H. Mohamed
.
cis-[RuCl2(bipy)2] 2H2O (0.1 mmol). The mixture was stirred at room
temperature for 2 h. The product was isolated as described to give benzoic
acid (19 mmol) (95% yield).
ACKNOWLEDGMENTS
I thank W. P. Griffith (Department of Chemistry, Imperial College, London
University) for his helpful discussion.
REFERENCES
1. Wolfe, S.; Hasan, S. K.; Campbell, J. R. J. Chem. Soc. Chem. Commun. 1970,
1420.
2. Carlesen, P. H. J.; Katsuki, T.; Martin, V. S.; Sharpless, K. B. J. Org. Chem. 1981,
46, 3936.
3. Huang, B.; Khrapov, M.; Hansen, K. C.; Idoux, J. P. Synth. Commun. 1995, 25,
2709.
4. Chakraborti, A. K.; Ghatak, M. R. J. Chem. Soc. Perkin 2 Trans. 1985, 2605.
5. Griffith, W. P.; Reddy, B.; Shoair, A. G. F.; Suriaatmaja, M.; White, A. J. P.;
Williams, D. J. J. Chem. Soc., Dalton Trans. 1998, 2819.
6. Griffith, W. P.; Shoair, A. G.; Suriaatmaja, M. Synth. Commun. 2000, 30, 3091.
7. Muller, P.; Godoy, J. Helv. Chim. Acta 1981, 64, 2531.
8. Murahashi, S.-I.; Komiya, N.; Hayashi, Y. H.; Kumano, T. Pure Appl. Chem. 2001,
73 (2), 311.
9. Connick, R. E.; Hurley, C. R. J. Am. Chem. Soc. 1952, 74, 5012.
10. Hansen, K. C.; Lin, Q.; Aminabhavi, T. M. J. Chem. Soc., Faraday Trans. 1996,
92 (19), 3643.
11. Sullivan, B. P.; Salmon, D. J.; Meyer, T. J. Inorg. Chem. 1978, 17, 3334.