A simple and highly selective biomimetic oxidation of alcohols with hypervalent iodine(III) reagent catalyzed by β-cyclodextrin in water

Article abstract of DOI:10.1007/s10562-011-0545-y

A simple, mild and highly efficient biomimetic oxidation of alcohols to the corresponding aldehydes or ketones with hypervalent iodine(III) reagent catalyzed by β-cyclodextrin was reported. β-cyclodextrin serves as a biological catalyst to enhance the rea

Full text of DOI:10.1007/s10562-011-0545-y

Catal Lett (2011) 141:582–586
DOI 10.1007/s10562-011-0545-y
A Simple and Highly Selective Biomimetic Oxidation
of Alcohols with Hypervalent Iodine(III) Reagent Catalyzed
by b-Cyclodextrin in Water
•
Chenjie Zhu Yunyang Wei
Received: 14 December 2010 / Accepted: 3 January 2011 / Published online: 11 January 2011
Ó Springer Science+Business Media, LLC 2011
Abstract A simple, mild and highly efficient biomimetic
oxidation of alcohols to the corresponding aldehydes or
ketones with hypervalent iodine(III) reagent catalyzed by
b-cyclodextrin was reported. b-cyclodextrin serves as a
biological catalyst to enhance the reaction remarkably. The
oxidation proceeded in water to afford aldehydes or
ketones in excellent yields and high selectivity without
remarkable over-oxidation to carboxylic acids. Selective
oxidation of primary alcohols in the presence of secondary
alcohols was also achieved. A possible mechanism for the
oxidation was proposed.
development of new catalytic oxidation system is particu-
larly attractive.
b-Cyclodextrin (b-CD), which is cyclic oligosaccharide
with hydrophobic cavity, can catalyze chemical reactions
by supramolecular catalysis involving reversible formation
of host–guest complexes by non-covalent bonding. The
complexation depends on the size, shape and hydropho-
bicity of the guest molecule. Thus, mimicking of bio-
chemical selectivity, which shows shape and substrate
selectivity, with the reactions being carried out in water
will be superior to chemical selectivity. Due to these
attractive features in the biomimetic modelling of chemical
reactions, b-cyclodextrin has drawn considerable attention
as an efficient catalyst for various organic transformations
[8–15].
Keywords Alcohols Á Cyclodextrin Á Hypervalent iodine Á
Catalytic oxidation Á Water
On the other hand, hypervalent iodine(III) reagents have
drawn considerable attention as mild and highly chemo-
selective oxidizing reagents for various organic transfor-
mations [16]. As a result of their nontoxic nature,
affordability, and safety profile, hypervalent iodine(III)
reagents are nowadays popular reagents for the forma-
tion of carbon–carbon bonds, carbon–heteroatom bonds,
heteroatom–heteroatom bonds. Activation of carbon–
hydrogen bonds, rearrangements and fragmentations can
also be induced by these reagents [17]. Therefore, hyper-
valent iodine compounds offer high potential for the
improvement of known reactions, not only from the envi-
ronmental point of view, they are also potentially inter-
esting reagents for the development of completely new
synthetic transformations. Some reviews about the oxida-
tion of alcohols using hypervalent iodine reagents have
been published just in the last 10 years [18, 19]. However,
typical reactions of common hypervalent iodine reagents
are performed in non-recyclable organic solvents such as
dichloromethane, dimethyl sulfoxide, and acetone, which
1 Introduction
The selective oxidation of alcohols to the corresponding
aldehydes or ketones is a fundamental transformation both
in laboratory synthesis and industrial production [1, 2].
Numerous oxidizing reagents (for example, CrO3, KMnO4,
MnO2, etc.) in stoichiometric amounts have been tradi-
tionally employed to accomplish this transformation with
considerable drawbacks such as the use of expensive
reagents, volatile organic solvents, and discharge of envi-
ronmentally pernicious wastes [3]. Transition metal-
catalyzed oxidations of alcohols using aqueous H2O2 or
gaseous O2 as oxidant have also been developed [4–7].
From economic and environmental perspectives, the
C. Zhu Á Y. Wei (&)
School of Chemical Engineering, Nanjing University of Science
and Technology, Nanjing 210094, China
e-mail: ywei@mail.njust.edu.cn
123

A Simple and Highly Selective Biomimetic Oxidation of Alcohols
583
H
several hours while checking the reaction progress by gas
or thin-layer chromatography. After completion, the mix-
ture was extracted with ethyl acetate (3 9 10 mL) and
analyzed by GC–MS. The organic layer was dried over
anhydrous sodium sulfate and concentrated under vacuum.
The crude product was purified by column chromatography
(petroleum ether/ethyl acetate = 10/1) to afford the ana-
lytically pure product. The aqueous phase was removed by
decantation and lyophilized to obtain the b-CD.
OH
CH2OH
H
C
H
O
CHO
(PhIO)3 SO3
Cyclodextrin/H2O
R
R
Scheme 1 Oxidation of alcohols catalyzed by (PhIO)3ÁSO3/b-cyclo-
dextrin in water
have potentially damaging environmental properties. The
development of aqueous-phase reactions using environ-
mentally friendly reagents is one of the active fields in
organic synthesis due to a recent demand for realization of
green chemical processes [20, 21]. From economic and
environmental perspectives, the development of reactions
in water based on hypervalent iodine reagents have
received great attention. Many highly efficient systems for
application of hypervalent iodine reagents in water have
been developed [22–28].
2.2.2 Oxidation of Alcohols with (PhIO)3ÁSO3 Generated
In Situ
b-Cyclodextrin (0.57 g, 0.5 mmol) was dissolved in H2O
(15 mL) at 60 °C for several minutes, followed by addition
of alcohol (1 mmol) with stirring. Then PhI(OAc)2 (0.35 g,
1.1 mmol) and NaHSO4ÁH2O (0.15 g, 1.1 mmol) were
added and stirred at 60 °C for several hours while checking
the reaction progress by gas or thin-layer chromatography.
After the completion of the reaction, the mixture obtained
was treated as above to afford the corresponding pure
product.
In continuation of our efforts to develop new applications
of hypervalent iodine reagents [29–34], here, we would
like to report a facile procedure for the oxidation of alcohols
to the corresponding carbonyl compounds with (PhIO)3Á
SO3 catalyzed by b-cyclodextrin in water (Scheme 1).
3 Results and Discussion
2 Experimental
The initial experiments were carried out using 4-nitroben-
zyl alcohol as the model substrate. First, a range of
hypervalent iodine reagents such as PhI(OAc)2, PhI
(OH)OTs, PhIO2, PhICl2, PhI(OCOCF3)2, and PhIO were
used as oxidant in the reaction, however, all of them were
not satisfactory probably due to their poor solubility in
water (Table 1, entries 1–6). Recently, Zhdankin and
co-workers [35, 36] have reported a mild and efficient
method for the preparation of oligomeric iodosylbenzene
sulfate (PhIO)3ÁSO3. This sulfate can find practical appli-
cation as a readily available, stable, and water-soluble
hypervalent iodine reagent with a reactivity pattern similar
to iodosylbenzene [37, 38]. It was found that in the case of
(PhIO)3ÁSO3 as oxidant, desired product was obtained in
49% yield (Table 1, entry 7). Encouraged by this result, we
evaluated the effects of three species of CDs on the reac-
tion, in hopes of promoting the oxidation. Fortunately,
b-CD serves as a good catalyst to enhance the reaction
remarkably (Table 1, entry 9). In the same conditions,
a-CD and c-CD show no catalytic activity (Table 1, entries
8 and 10). It might be concluded that the oxidation with
CDs as catalyst is highly shape-selective, owing to the
different interior cavity sizes of these CDs. With regard to
the dosage of b-CD, use of more b-CD accelerated the
reaction rate (Table 1, entries 9, 11, and 12). It is well
known that the presence of an appropriate catalyst (Lewis
acid, bromide or iodide anions, transition metal complex)
2.1 Instruments and Reagents
Gas chromatography (GC) analysis was performed on an
Agilent GC-6820 chromatograph equipped with
a
30 m 9 0.32 mm 9 0.5 lm HP-Innowax capillary col-
umn and a flame ionization detector. GC–MS spectra were
recorded on Thermo Trace DSQ GC–MS spectrometer
using TRB-5MS (30 m 9 0.25 mm 9 0.25 lm) column.
(PhIO)3ÁSO3 was prepared from commercially available
PhI(OAc)2 and NaHSO4ÁH2O by a procedure described in
the literature [35, 36]. Other reagents (AR grade) were
obtained from commercial resources and used without
further purification. Products were all known compounds
and were identified by comparing of their physical and
spectra data with those reported in the literature.
2.2 Typical Procedure for Oxidation of Alcohols
2.2.1 Oxidation of Alcohols with (PhIO)3ÁSO3
b-Cyclodextrin (0.57 g, 0.5 mmol) was dissolved in H2O
(15 mL) at 60 °C for several minutes, and then alcohol
(1 mmol) was added slowly with stirring. To this was
added (PhIO)3ÁSO3 (0.30 g, 0.4 mmol) portion-wise over a
period of 10 min. The mixture was stirred at 60 °C for
123

584
C. Zhu, Y. Wei
Yield (%)a
Table 1 Optimization studies for the conversion of 4-nitrobenzyl alcohol
Entry
Oxidant
Catalyst (equiv)
Additive
Temperature (°C)
1
PhI(OAc)2
PhI(OH)OTs
PhIO2
–
–
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
60
–
2
–
–
14
–
3
–
–
4
PhICl2
–
–
–
5
PhI(OCOCF3)2
PhIO
–
–
22
27
49
46
76
44
83
85
81
77
80
94
92
6
–
–
7
(PhIO)3ÁSO3
(PhIO)3ÁSO3
(PhIO)3ÁSO3
(PhIO)3ÁSO3
(PhIO)3ÁSO3
(PhIO)3ÁSO3
(PhIO)3ÁSO3
(PhIO)3ÁSO3
(PhIO)3ÁSO3
(PhIO)3ÁSO3
PhI(OAc)2
–
–
8
a-CD (0.1)
b-CD (0.1)
c-CD (0.1)
b-CD (0.5)
b-CD (1.0)
b-CD (0.5)
b-CD (0.5)
b-CD (0.5)
b-CD (0.5)
b-CD (0.5)
–
9
–
10
11
12
13
14
15
16
17
–
–
–
KBr
Et2OÁBF3
3 A MS
˚
–
NaHSO4ÁH2O
60
Reactions were performed by using 4-nitrobenzyl alcohol (1 mmol), oxidant (1.1 mmol), catalyst (0.5 mmol), H2O (15 mL) at 60 °C for 3 h
unless otherwise noted
a
GC–MS yield
can effectively depolymerize (PhIO)n generating the reac-
tive monomeric species [39]. However, addition of KBr,
alcohol was not satisfactory, indicating that the space
configuration of guest molecules is more important for
smooth conversion than the influence from electron effect
in the present catalytic system. This could be further sup-
ported by the fact that the existence of any group on the
aromatic ring decreased the reactivity more or less
(Table 2, entries 1–6).
˚
Et2OÁBF3 or 3 A molecular sieves to accelerate the depo-
lymerization did not improve the oxidation (Table 1,
entries 13–15). In addition, increasing the temperature is
beneficial to the reaction (Table 1, entry 16). A further
study showed that (PhIO)3ÁSO3 can be generated in situ
from PhI(OAc)2 and NaHSO4ÁH2O, used conveniently
without isolation for the oxidation (Table 1, entry 17).
In order to evaluate the versatility of this novel catalytic
system, we applied the procedure to the oxidation of a wide
range of alcohols. Excellent chemoselectivity was observed
under the present system. We detected no phenol oxidation
products (Table 2, entry 6), which are well known to form
in reactions with aryl-k3-iodanes. For the oxidation of
primary alcohol, no noticeable over-oxidation of aldehyde
to carboxylic acid was detected. Allylic alcohol such as
cinnamyl alcohol (Table 2, entry 9) was also oxidized
efficiently without any observable reaction at the double
bond functionality. In the present research benzylic alco-
hols underwent smooth oxidation (Table 2, entries 1–7).
The electronic properties of the substituents in the aromatic
ring had remarkable influence on the rate of the oxidation
of benzyl alcohols. Strong electron withdrawing groups,
such as nitro group, improve the oxidation of alcohol
(Table 2, entry 2). Strong electron-donating groups, such
as –OCH3 group, lowered the reaction rate (Table 2, entry
4). However, the yield of the oxidation of 2-nitrobenzyl
In spite of the good results with benzylic alcohols, the
oxidation of cycloalkyl and aliphatic alcohols under the
same conditions gave quite low yields (Table 1, entries
12–13). Cyclohexanol exhibited low reactivity towards the
oxidation, which may be explained by the bulk of the
cyclohexyl group, with chair and boat conformations
occupying more space than an aromatic group. The other
possible reason might attribute to the inactive of the
hydroxyl group in virtue of the absence of electron cloud
conjugation.
It is known that b-CD and substrates can form host–
guest complex. This complexation depends on the size,
shape and hydrophobicity of the guest molecule. For
example, the steric hindrance of the diphenyl group might
account for the lack of reactivity of diphenylmethanol,
which is too large to enter into the hydrophobic cavity of
b-CD during the reaction (Table 2, entry 8). This could be
further evidenced that the oxidation of straight-chain ali-
phatic alcohol. The oxidation exhibited low reactivity most
probably due to the impossibility of formation of an steady
intermediate owing to the long distance between alcohol
123

A Simple and Highly Selective Biomimetic Oxidation of Alcohols
585
Table 2 b-cyclodextrin catalyzed oxidation of alcohols
Entry
1
Alcohols
Products
Catalytic systema
A
Time (h)
2
Yield (%)b
92 (1st)
90 (2nd)
91 (3rd)
90
OH
O
B
A
B
3
3
3
2
3
4
5
6
7
94
OH
O
92
O2N
O2N
Cl
A
B
3
4
90
88
OH
OH
O
Cl
O
A
B
5
6
82
79
O
O
A
B
5
7
76
70
OH
NO2
O
NO2
A
B
4
5
86
89
OH
O
HO
HO
A
B
4
5
87
85
OH
O
8
A
B
8
37
26
OH
O
10
9
A
B
6
8
90
87
OH
O
10
A
B
8
76
64
OH
O
10
11
A
B
5
6
83
80
O
O
OH
O
12c
A
B
8
58
47
OH
O
10
13c
n-C11H23–CH2OH
n-C11H23–CHO
A
B
10
10
Trace
Trace
a
Catalytic system A: (PhIO)3ÁSO3/b-cyclodextrin, B: PhI(OAc)2/NaHSO4ÁH2O/b-cyclodextrin
Yields of isolated products unless otherwise noted
b
c
Yields were determined by GC–MS
and b-CD (Table 2, entry 13). By compare with the oxi-
Next, we modified this system to develop a practical
and clean procedure for the oxidation of alcohols
with (PhIO)3ÁSO3 generated in situ from PhI(OAc)2 and
NaHSO4ÁH2O. The use of PhI(OAc)2 and NaHSO4ÁH2O
instead of (PhIO)3ÁSO3 in the oxidation led to similar
results, albeit a little longer reaction time was needed. This
dation of benzyl alcohol, cinnamyl alcohol, and phenethyl
alcohol (Table 2, entries 1, 9 and 10), it can also conclude
that increase the methylene group in the substrate might
retard the host–guest complex intermediate formation by
hydrogen bonding.
123

586
C. Zhu, Y. Wei
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At the end of the reaction, the b-CD was recovered by
precipitation with ethyl acetate, the aqueous phase was
removed by decantation and lyophilized to obtain the
b-CD. The recycled b-CD was reused for three times with
no loss of activity or selectivity, and only 1.6% loss of
weight was observed after three times recycling (Table 2,
entry 1). Therefore, from the point of view on the greener
chemical processes, the use of this catalytic system do not
lead to two major sources of waste: organic solvent and
catalyst.
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346:346
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Scheme 2 shows the result of the competitive oxidation
of primary and secondary alcohol. 1 equivalent oxidant was
used in this competitive reaction. The competing oxidation
of an equimolecular mixture of benzyl alcohol and
1-phenylethanol resulted in 87% yield of benzaldehyde and
less than 10% yield of acetophenone. This result suggest
that chemoselective oxidation of primary alcoholic func-
tionality in the presence of secondary alcoholic function-
ality is possible with the present system.
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4 Conclusions
27. Ye Y, Wang L, Fan R (2010) J Org Chem 75:1760
28. Panchan W, Chiampanichayakul S, Snyder DL, Yodbuntung S,
Pohmakotr M, Reutrakul V, Jaipetch T, Kuhakarn C (2010)
Tetrahedron 66:2732
In summary, a simple, mild and highly efficient biomimetic
oxidation of alcohols with (PhIO)3ÁSO3/b-cyclodextrin in
water has been developed, which allowed the oxidation of
alcohols to aldehydes or ketones in excellent yields and
high selectivity without remarkable over-oxidation to car-
boxylic acids. It is noteworthy to mention that the catalyst
could easily be recycled and reused without loss of activity
and the oxidant could also be generated in situ.
29. Zhu C, Ji L, Wei Y (2010) Synthesis 3121
30. Zhu C, Ji L, Wei Y (2010) Catal Commun 11:1017
31. Zhu C, Sun C, Wei Y (2010) Synthesis 4235
32. Zhu C, Ji L, Zhang Q, Wei Y (2010) Can J Chem 88:362
33. Zhu C, Ji L, Wei Y (2010) Monatsh Chem 141:327
34. Zhu C, Wei Y, Ji L (2010) Synth Commun 40:2057
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VV (2009) Inorg Chem 48:4908
Acknowledgment We are grateful to Nanjing University of Science
and Technology for financial support.
37. Yusubov MS, Yusubova RY, Funk TV, Chi KW, Zhdankin VV
(2009) Synthesis 2505
38. Yoshimura A, Neu HM, Nemykin VN, Zhdankin VV (2010) Adv
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