Reaction-controlled phase-transfer catalytic oxidative cleavage of cyclopentene to glutaraldehyde over peroxy-niobic acid

Article abstract of DOI:10.1246/cl.2002.220

The oxidative cleavage of cyclopentene to glutaraldehyde with aqueous H₂O₂ was performed over a peroxy-niobic acid catalyst with high yield (72%) and complete conversion of cyclopentene under mild reaction conditions. Peroxy-niobic acid has been shown as a "reaction-controlled phase-transfer" catalyst, which has the advantages of both homogeneous and heterogeneous catalysts.

Full text of DOI:10.1246/cl.2002.220

220
Chemistry Letters 2002
Reaction-Controlled Phase-Transfer Catalytic Oxidative Cleavage of Cyclopentene to
Glutaraldehyde over Peroxy-niobic Acid
Hao Chen, Wei-Lin Dai,ꢀ An-Ren Jiang, and Jing-Fa Deng
Department of Chemistry, Fudan University, Shanghai 200433, P. R. China
(Received September 13, 2001; CL-010909)
The oxidative cleavage of cyclopentene to glutaraldehyde with
oxidation took place. After the H2O2 was consumed, peroxy-niobic
acid was self-precipitated slowly and could be removed from the
system for its reuse.6 This phenomenon suggested a solid-liquid-
solid phase transfer of the catalyst, which was controlled by the
reaction. After stirring at 308 K for 24 hours, the mixture was
sampled and analyzed by GC-MS, according to the details found
elsewhere.3;4 There were several by-products in the product
mixture, such as the solvated compounds (2-R-1-cyclopentanol
(R¼methoxy, ethoxy, iso-propoxy, tert-butoxy, etc.), cyclopen-
tane-1,2-diol, and other little amounts of by-products: cyclopenta-
none, cyclopentenone and cyclopentene oxide. Details are shown in
Tables 1–3.
A strong band at 860cm À1 (v(O-O)) was observed in the FT-IR
spectrum, indicating the presence of a niobic peroxo-group in the
prepared solid.7 The XPS analysis showed that the binding energy
of the Nb 3d 5/2 was at 207.3 eV, suggesting that the chemical
valence of niobuim in the solid was þ5. The niobium content of the
solid was determined as 45.3% through elementary analysis.
Iodometric titration analysis, based on the literature method,8
showed that the molar ratio of peroxo-group (O-O) to niobium is
almost 1 : 1. TG analysis showed that the content of the released
water and oxygen from the as-prepared peroxy-niobic acid was
26.9% and 7.6%, respectively. Accordingly, the simple chemical
formula of the solid can be denoted as Nb2(O2)2O3ꢁ6H2O. Similar
formula was also obtained by V. A. Titova et al.9
aqueous H2O2 was performed over a peroxy-niobic acid catalyst
with high yield (72%) and complete conversion of cyclopentene
under mild reaction conditions. Peroxy-niobic acid has been shown
as a ‘‘reaction-controlled phase-transfer’’ catalyst, which has the
advantages of both homogeneous and heterogeneous catalysts.
Glutaraldehyde (GA) is now commonly used in sterilization
and disinfection fields, whose large-scale utilizations are restricted
by its complicated and expensive process in the case of using
propenal as raw material.1 H. Furukawa et al. reported an interesting
one-step route for the preparation of GA by the oxidative cleavage
of cyclopentene (CPE) in 1987.2 Unfortunately, the advantages of
lowering the cost by short-cutting the conventional multi-step
reaction and using the cheap raw material are far outweighed by the
inefficiency of the noble catalysts as well as the dangerous
anhydrous H2O2 involved in the reaction. We have previously
developed another new system,3;4 which has made great improve-
ments to this one-step route against those drawbacks mentioned
above, using environmentally benign and clean aqueous H2O2,
instead of dangerous anhydrous H2O2, as oxygen donor and cheap
tungstic acid as catalyst. However, the new route has not yet
succeeded in industry because of two factors: the relatively
expensive solvent—tert-butanol and the problem in homogeneous
catalytic systems: the difficulty of separation and reuse of the
tungstic acid catalyst.
We herein first report the novel catalytic system in which CPE
was oxidized to GA by aqueous H2O2 when using ethanol as the
solvent and peroxy-niobic acid as the catalyst. Complete conversion
of CPE and a very high yield of GA (72%) were obtained. The
unique characteristic of this system is the use of peroxy-niobic acid
as a ‘‘reaction-controlled phase-transfer’’ catalyst,5 which over-
came all the drawbacks of our previous tungstic acid system. Thus,
the present catalytic reaction system may open new promising route
for the preparation of GA commercially.
Peroxy-niobic acid was synthesized according to the following
procedure: 1 g of Na8Nb6O19ꢁ9H2O was dissolved in 10mL of
30wt% aqueous H 2O2 at 268 K, then cooled concentrated HCl was
slowly added into the solution under gentle stirring until the pH of
the solution was adjusted to about 1.0. A yellow solid precipitate
was collected after the further stirring at room temperature for
another 1 hour. The as-prepared precipitate was washed by distilled
water, and dried in air for further study.
The selective oxidation of CPE to GA in the presence of
peroxy-niobic acid catalyst was carried out as follows: 66 mg of
peroxy-niobic acid was added into the mixture of 1 mL of CPE,
certain amount of ethanol and aqueous H2O2. The yellow solid
catalyst gradually dissolved and the system gradually changed from
turbid to clear during the reaction, demonstrating that homogeneous
As shown in Table 1, the nature of solvents exerted a significant
influence on the oxidation. When reaction was carried out in
ethanol, the highest yield of GA (59%) was achieved at complete
consumption of CPE, using 30% H2O2 as the oxidant. Although
complete conversion of CPE also ocurred in methanol, the GA yield
was only 50%, 9% lower than that of ethanol. When 2-propanol and
tert-butanol were used as the solvent, the CPE consumption was
low: 80% and 74%, respectively, after 24 hours’ reaction, resulting
in lower yields of GA: 45% and 40%, respectively. Other non-
alcoholic solvents such as dichloro-methane were also used, but the
results were not satisfactory: CPE conversion ꢂ70%, GA yield
ꢂ32%.
The reaction results as a function of the relative amount of
ethanol was also investigated as listed in Table 2. It was shown that
Table 1. The CPE oxidation to GA using different solvents
Selct. of
GA/%
CH3OH 5105 51051020
Conv. of
CPE/%
Yield/%
1,2-diol
solvent
GA
59
22
4019
17
a
b
7
C2H5OH
i-C3H7OH
t-C4H9OH
CH2Cl2
59
56
54
46
100
8045
74
25
8
6
—
9
5
9
21
7032
Reaction temperature: 308 K, 1 mL of CPE, 4 mL of solvent, 66 mg of
niobium peroxide; Reaction time: 24 hours; a, by-product from the
reaction of CPE with the solvnt; b, other by-products, including
cyclopentene oxide and cyclopentanone.
Copyright Ó 2002 The Chemical Society of Japan

Chemistry Letters 2002
221
Table 2. Effect of ethanol amount on the GA preparation
ratio of peroxide group (O-O) to Nb in the catalyst was also kept at
1 : 1 after thereactions and theelementary analysis also showed that
the element content was almost the same (determined as ꢂ45:1%)
as in the fresh catalyst (ꢂ45:3%), demonstrating that the catalyst
kept its chemical state before and after the oxidative cleavage
reaction. Moreover, the catalytic performance of the recovered
catalyst after 10reaction cycles was just the same as those of the
fresh catalyst without any addition of fresh catalyst, indicating the
excellent stability of catalyst. As compared to the tungstic acid
catalyst, this novel catalyst has much longer life time because the
tungstic acid catalyst is a homogeneous one and cannot be reused.
The reactivity of several different olefins toward H2O2
catalyzed by peroxo-niobic acid under similar reaction conditions
is illustrated in Table 4. Acyclic olefins have low reactivity than that
of cyclic olefins. However, in all cases the C¼C bond is cleaved and
the aldehydes are produced.
Vethanol
/mL
Conv.
of CPE/%
Yield/%
GA
1
2
3
2
4
6
8630040
100
98
4
59
55
25
22
12
18
4
5
8
1028400
910650
4 20
25
3
Reaction condition: 22.7 mmol of H2O2 (30%), 1 mL of CPE, 66 mg of
catalyst, reaction temperature: 308 K, reaction time: 24 hours. 1:
cyclopentane-1,2-diol, 2: 2-ethoxy-1-cyclopentanol; 3, other little
amounts of by-products: cyclopentanone, cyclopentenone and cyclo-
pentene oxide.
an appropriate amount of the ethanol solvent is required for this
reaction. H2O2 was found to decompose apparently during the
reaction when small amount of ethanol was used, while extra
amount of ethanol would lead to the low concentrations of the
reagents and decrease the reaction rate, both resulting in the low
yield of GA in a given reaction time. Based on the experimental
data, the optimal volume ratio of ethanol to CPE was determined to
be 4 : 1.
Table 4. Reactivity of various olefins
Olefin
Conv./%
Yield/%
CPE
cyclohexene
1-hexene
styrene
100
100
100
84
a1(72)
a2(40)
a3(20)
a4(22)
b1(16)
c1(9)
c2(5)
c3(—)
c4(—)
d1(1)
d2(3)
d3(27)
d4(1)
b2(15)
b3(15)
b4(14)
The molar ratio of CPE to H2O2 has a substantial effect on the
oxidative reaction results. Low yield of GA (<50%) would
inevitably result from the incomplete conversion of CPE when the
ratio of H2O2 to CPE was less than 2 : 1. If the ratio was higher than
2 : 1, a co-product, pentanedioic acid would be produced due to the
over oxidation of CPE, which also leaded to the low GA yield. As a
result, the optimal molar ratio of H2O2 to CPE was fixed at 2 : 1.
This is in good agreement with the theoretically stoichiometric
oxidative cleavage of CPE to GA. The H2O2 weight content in its
aqueous solution also has an important effect on the oxidative
cleavage of CPE, as shown in Table 3. Excellent GA yield (72%)
was obtained when a 50wt% H 2O2 was used, which was much
higher than that reported when niobic acid or niobium oxide was
used as catalyst (ꢂ10%) and suggested the possibility of the
commercial application of the peroxy-niobic acid catalyst. Also, it
is obvious to find that the increase of the H2O2 concentration leads
to thecorresponding increase of theGA yield, which can be ascribed
to the decrease of the less valuable by-product of cyclopentane-1,2-
diol. Similar phenomenon was also observed in our previous
work.3;4
Reaction condition: 11.4 mmol of olefin, 66 mg of catalyst, other
reaction conditions are the same as in Table 3. a1, a2: dialdehydes; a3:
pentanal; a4: phenyl aledehyde; b1 ꢂ b4: diol; c1: 2-ethoxy-1-cyclo-
pentanol; c2: 2-ethoxy-1-cyclohexanol; c3: 2-ethoxy-1-hexanol; c4: 2-
ethoxy-phenethyl alcohol; d1 ꢂ d4: epoxides.
In conclusion, the catalytic reaction system in the presence of a
‘‘reaction-controlled phase-transfer’’ peroxy-niobic acid catalyst
provides an effective method to prepare GA at high yield (ꢂ72%)
from CPE with complete conversion, which has the advantages of
the homogeneous and heterogeneous catalysis. The utilization of
environmentally benign and clean aqueous H2O2 as the oxygen
donor in cheap ethanol solvent makes the reaction process highly
promising. A further work is under way to show the actual structure
of the catalyst before and during the oxidative cleavage reaction as
well as the detailed catalytic mechanism of the reaction system.
This work was supported by the National Natural Science
Foundation of China and SINOPEC.
Table 3. Effect of H2O2 concentration on the GA preparation
References and Notes
CH2O2
/%
059 301025
Conv. of
CPE/%
12
100
100
100
Yield/%
1
Conv. of
H2O2/%
1
2
3
4
5
6
S. P. Gorman, E. M. Scott, and A. D. Russell, J. Appl. Bacteriology, 48,
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(2001).
After the reaction, the mixture was poured into the centrifuge tubes and
was centrifugalized at 6000 rpm for 10 min. The precipitated yellow
solid was washed with purified water and centrifugalized for 3 times,
then it was dried in air at room temperature. Thus recovered catalyst
could be reused without any addition of fresh catalyst.
C. Djordjevic and N. Vuietic , Inorg. Chem., 7, 1864 (1968).
M. W. Droege and R. G. Finke, J. Mol. Catal., 69, 323 (1991).
V. A. Titova, I. G. Slatinskaya, and V. G. Pitsyuaga, Russ. J. Inorg.
Chem. (Transl. of Zh. Neorg Khim.), 20, 2699 (1975).
GA
2
3
4
99
36
45
50
62
68
72
23
17
16
11
11
9
4
4
3
100
100
100
Relaction condition: 1 mL of CPE, 4 mL of ethanol, 66 mg of catalyst,
22.7 mmol of H2O2, reaction temperature: 308 K, reaction time:
24 hours. 1: cyclopentane-1,2-diol; 2: 2-ethoxy-1-cyclopentanol; 3,
small amounts of cyclopentene oxide, cyclopentanone and cyclopente-
none.
After each reaction, the novel ‘‘reaction-controlled phase-
transfer’’ catalyst was self-precipitated with a >95% recovery yield
(by weight). After 10cycles of the catalytic reactions, in the FT-IR
spectrum, the band at 860cm À1 (v(O-O)) of the peroxy-niobic acid
was still observed, showing that the peroxide group was still
preserved in the catalyst after the reactions. Furthermore, the molar
7
8
9