Lipase catalyzed Cannizzaro-type reaction with substituted benzaldehydes in water

Article abstract of DOI:10.1016/j.tetlet.2014.05.022

Lipases were found to catalyze Cannizzaro-type reaction of substituted benzaldehydes in aqueous medium at 30 °C without the addition of any external redox reagent. The ratio of alcohol product to acid product varied with nature of the substituted benzaldehyde, enzyme, and the presence of organic co-solvent.

Full text of DOI:10.1016/j.tetlet.2014.05.022

Tetrahedron Letters xxx (2014) xxx–xxx
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Tetrahedron Letters
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Lipase catalyzed Cannizzaro-type reaction with substituted
benzaldehydes in water
a
a
b,
⇑
Benu Arora , Pramod S. Pandey , Munishwar N. Gupta
a
Chemistry Department, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Lipases were found to catalyze Cannizzaro-type reaction of substituted benzaldehydes in aqueous
medium at 30 °C without the addition of any external redox reagent. The ratio of alcohol product to acid
product varied with nature of the substituted benzaldehyde, enzyme, and the presence of organic
co-solvent.
Received 22 February 2014
Revised 10 May 2014
Accepted 12 May 2014
Available online xxxx
Ó 2014 Elsevier Ltd. All rights reserved.
Keywords:
Cannizzaro reaction
Catalytic promiscuity
Novozyme 435
Organic reaction in aqueous media
Enzymes are used in both aqueous and non-aqueous media for
organic synthesis. These applications of enzymes have been
benign solvent is increasingly being used as the reaction medium for
various organic reactions. The lipase catalyzed Cannizzaro-type
1
7
further expanded in recent years by exploiting their biocatalytic
promiscuity. Among enzymes, lipases have been used more often
for exploring new promiscuous activities. Numerous examples of
lipase catalyzed CAC, CAN, and CAS bond formation have been
reaction also uses water as the reaction medium.
Novozyme 435 (commercially available immobilized lipase B
from Candida antarctica) catalyzed the conversion of
p-nitrobenzaldehyde to p-nitrobenzyl alcohol and p-nitrobenzoic
acid (Scheme 1). The reaction medium was 100 mM sodium
phosphate buffer, pH 7.0 and reaction temperature was 30 °C.
Analysis of the reaction mixture after a period of 24 h showed
the formation of these two products in almost equal amounts. A
control reaction run in the absence of enzyme did not lead to the
formation of any product even after 24 h.
In order to evaluate the scope of this promiscuous lipase
catalyzed reaction, benzaldehyde and a few other substituted
benzaldehydes were tried as substrates. Table 1 summarizes the
product composition obtained after a period of 24 h. In each case,
both the redox products were obtained, although the ratio of
alcohol: acid showed variation.
2
reported. Besides this, lipases have also been reported to catalyze
various oxidative reactions in combination with hydrogen perox-
3
ide as the oxidant. Cannizzaro reaction is the redox disproportion-
ation of aldehydes that lack
a-hydrogen to an equimolar mixture
4
of a primary alcohol and a carboxylic acid salt. While the classical
Cannizzaro reaction requires strongly basic conditions along with
elevated temperatures, there have been reports in recent years
about the use of microwave irradiation, ultrasonication, and Lewis
5
acid catalysts as alternative ways of catalyzing the reaction.
Recently, the use of alcohol dehydrogenases (ADHs) for catalyzing
6
a Cannizzaro-type reaction has also been reported. We report here
that lipases are able to catalyze the Cannizzaro-type reaction of
benzaldehydes without the presence of any external redox reagent
such as hydrogen peroxide.
Novozyme 435 catalyzed Cannizzaro-type reaction of
p-nitrobenzaldehyde was further investigated by studying the time
8
The lipase catalyzed redox reaction is a very simple system
for obtaining the reduced as well as oxidized products of
course of this reaction by HPLC analysis. The reaction was found
6
p-nitrobenzaldehyde. Unlike alcohol dehydrogenases, this system
does not require any cofactor, thereby automatically eliminating
the need for any cofactor regeneration. Water as an environmentally
⇑
Corresponding author. Tel.: +91 11 2659 1503.
E-mail address: munishwar48@yahoo.co.uk (M.N. Gupta).
Scheme 1. Lipase catalyzed Cannizzaro-type reaction in water.
http://dx.doi.org/10.1016/j.tetlet.2014.05.022
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0
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2
B. Arora et al. / Tetrahedron Letters xxx (2014) xxx–xxx
Table 1
brought about the oxidation of p-nitrobenzyl alcohol to the corre-
sponding acid (Fig. S1).
Cannizzaro-type reaction of substituted benzaldehydes catalyzed by Novozyme 435
in aqueous mediuma
The oxidation of p-nitrobenzyl alcohol was found to be a much
slower reaction as compared to the conversion of p-nitrobenzalde-
hyde to p-nitrobenzyl alcohol. Presence of both air as well as
enzyme was found to be necessary for the oxidation reaction. Reac-
tion carried out either in the absence of air or in the absence of
enzyme led to the formation of less than 10% acid even after 72 h.
Lewis had reported that with sodium hydride as a base, the
Cannizzaro reaction with p-nitrobenzaldehyde followed two dif-
Entry
1
Substrate
Conversionb (%)
96
Product ratioc
1: 0.81
CHO
O2N
CHO
2
96
1: 1.28
9
ferent routes simultaneously. The classical mechanism involving
NO2
hydride transfer probably dominated in the early phase and
provided both alcohol and acid in equal amounts. However, the
radical anion mediated route later on converted even the alcohol
into acid. [The radical anion intermediate formation in Cannizzaro
reaction with benzaldehydes has also been reported in more recent
CHO
3
4
90
98
1: 0.80
1: 0.63
NO2
CHO
1
0
11
years by Chung (in alkaline aqueous dioxane) and Ashby et al.
Cl
(in alkaline tetrahydrofuran/hexamethylphosphoramide as the
reaction medium)].
CHO
5
6
98
78
1: 1.39
1: 0.44
To investigate whether there is some involvement of free radi-
cal intermediate(s) in the present case, Novozyme 435 catalyzed
reaction with p-nitrobenzaldehyde was carried out with either
ferrous sulfate or diphenylamine added to the reaction medium.
Both are known to inhibit free radical mediated reactions.12
Figure 2 shows the time course of the reaction carried out with
each of these additives. While both the additives partially inhibited
the formation of p-nitrobenzoic acid, no inhibitory effect could be
seen on the formation of p-nitrobenzyl alcohol. DMSO is known to
act as a scavenger of free radicals. Interestingly, addition of 10%
DMSO (v/v) as a co-solvent completely inhibited the formation of
the carboxylic acid, while the formation of the alcohol remained
unaffected (Fig. 2).
H CO
3
CHO
a
Reaction conditions: substrate (1 mM) in 100 mM sodium phosphate buffer, pH
.0 at 30 °C, 200 rpm.
Total conversion (alcohol + acid) obtained by HPLC analyses after a period of
4 h.
Ratio of the alcohol to the carboxylic acid, after a period of 24 h; the alcohol
concentration being arbitrarily set at 1.
7
2
b
c
1
3
to show an unusual pattern of formation of products. Usually in a
self-Cannizzaro reaction, the alcohol and acid are expected to be
formed in equal amounts, as these result from disproportionation
of the same aldehyde. As shown in Figure 1, in the presence of
the lipase, p-nitrobenzaldehyde underwent a quick conversion to
the alcohol; about 60% conversion was achieved in just 6 h. Until
this time, the acid appeared only in traces. As mentioned earlier,
the two products became almost equal after 24 h. Thereafter,
concentration of the alcohol kept decreasing while that of acid
kept increasing. This raised the possibility that the p-nitrobenzyl
alcohol was getting oxidized to p-nitrobenzoic acid.
It appears that radical anion intermediate(s) is also involved
during the lipase catalyzed Cannizzaro-type reaction. The autoxida-
tion of benzyl alcohols (catalyzed by bases) is known to involve
9
,14
radical anion intermediates.
Hence, it is likely that in the present
slow oxidation to
case p-nitrobenzyl alcohol undergoes
a
p-nitrobenzoic acid. It is interesting to observe that inspite of ESR
indicating formation of free radicals, Ashby et al. also found that
radical inhibitors or traps did not inhibit the rate of Cannizzaro
1
1
reaction.
In order to find out whether the oxidation of p-nitrobenzyl
alcohol by the lipase was responsible for the trend observed during
the later part of the reaction, a similar reaction was carried out
starting with p-nitrobenzyl alcohol and Novozyme 435 under
identical reaction conditions. It was found that the lipase indeed
Figure 1. Time course for Cannizzaro-type reaction of p-nitrobenzaldehyde cata-
lyzed by Novozyme 435.
Figure 2. Effect of additives on Novozyme 435 catalyzed Cannizzaro-type reaction
of p-nitrobenzaldehyde.
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B. Arora et al. / Tetrahedron Letters xxx (2014) xxx–xxx
3
Table 2
Acknowledgments
Lipase screening and control reactions for Cannizzaro-type reaction of
p-nitrobenzaldehydea
This work was supported by Grants from the Department of
Science and Technology (DST), Govt. of India (Grant No. SR/SO/
BB-68/2010). B.A. thanks CSIR, India for providing Senior
Research Fellowship. The authors also thank Dr. Abir Majumder
Entry
Catalyst
p-Nitrobenzyl
alcohol
p-Nitrobenzoic
acid
b
b
1
2
3
4
5
6
7
8
9
Novozyme 435
Lipozyme CAL-B
Palatase
Lipozyme RMIM
CAL-A
45
70
66
77
0
0
0
0
0
54
25
23
21
45
0
0.3
6
2
[
Department of Chemistry, Rajiv Gandhi University of Knowledge
Technologies, Andhra Pradesh, India] for his help in separation of
the products obtained in this reaction.
Triethylamine
Imidazole
Urea denatured Novozyme 435c
Supplementary data
No enzyme
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2014.05.
a
Reaction conditions: p-nitrobenzaldehyde (1 mM) in 100 mM sodium phos-
phate buffer, pH 7.0, and lipase (20 mg) or imidazole (0.1 mmol), or triethylamine
(
0
22.
0.1 mmol) at 30 °C, 200 rpm.
b
Corresponds to conversion values obtained by HPLC after a period of 24 h.
Enzyme was denatured by incubating overnight with 8 M urea at 100 °C.
c
References and notes
1.
(a) Stereoselective Biocatalysis; Patel, R. N., Ed.; Marcel Dekker: New York, 2000;
b) Methods in Non-Aqueous Enzymology; Gupta, M. N., Ed.; Birkhauser: Berlin,
000; (c) Modern Biocatalysis: Stereoselective and Environmentally Friendly
Reactions; Fessner, W.-D., Anthonsen, T., Eds.; Wiley-VCH: Weinheim, 2009;
d) Banoth, L.; Narayan, T. K.; Banerjee, U. C. Tetrahedron: Asymmetry 2012, 23,
(
2
Over the years, numerous mechanisms have been proposed for
9
–11,15
Cannizzaro reaction.
Obviously, a complete mechanistic
(
understanding of lipase catalyzed Cannizzaro-type reaction
reported here would need a lot more extensive investigation. Based
on the limited evidence that we have, we can only infer that: (a)
this enzyme catalyzed Cannizzaro-type reaction does not follow
the most widely accepted hydride transfer mechanism alone (b)
it looks as if like in the case of Lewis the enzyme catalyzed reaction
also follows twin routes simultaneously. Also, it appears as if con-
version of alcohol to acid is predominantly carried out via some
free radical intermediate. With our limited data, it may not be cor-
rect to speculate beyond this.
1272; (e) Adlercreutz, P. Chem. Soc. Rev. 2013, 42, 6406.
(a) Majumder, A. B.; Ramesh, N. G.; Gupta, M. N. Tetrahedron Lett. 2009, 50,
2
3
.
.
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4
190; (b) Busto, E.; Gotor-Fernandez, V.; Gotor, V. Chem. Soc. Rev. 2010, 39,
504; (c) Gupta, M. N.; Kapoor, M.; Majumder, A. B.; Singh, V. Curr. Sci. 2011,
100, 1152; (d) Kapoor, M.; Gupta, M. N. Process Biochem. 2012, 47, 555; (e) Xie,
Z.-B.; Wang, N.; Jiang, G.-F.; Yu, X.-Q. Tetrahedron Lett. 2013, 54, 945.
(a) Carlqvist, P.; Eklund, R.; Hult, K.; Brinck, T. J. Mol. Model. 2003, 9, 164; (b)
Rios, M. Y.; Salazar, E.; Olivio, H. F. Green Chem. 2007, 9, 459; (c) Sharma, U. K.;
Sharma, N.; Kumar, R.; Sinha, A. K. Org. Lett. 2009, 11, 4846.
Geismann, T. A. Org. React. 1944, 2, 94.
(a) Varma, R. S.; Naicker, K. P.; Liessen, P. J. Tetrahedron Lett. 1998, 39, 8437; (b)
Entezari, M. H.; Shameli, A. A. Ultrason. Sonochem. 2000, 7, 169; (c) Curini, M.;
Epifano, F.; Genovese, S.; Marcotullio, M. C.; Rosatti, O. Org. Lett. 2005, 7, 1331.
Wuensch, C.; Lechner, H.; Glueck, S. M.; Zangger, K.; Hall, M.; Faber, K.
ChemCatChem 2013, 5, 1744.
4
5
.
.
6
7
.
.
Some of the other commercially available lipases were also
screened for their activity in the Cannizzaro-type reaction of p-
nitrobenzaldehyde. Table 2 summarizes the product composition
obtained after a period of 24 h by HPLC. Lack of formation of either
of the reaction products in significant amount in entries 8 and 9
indicates the specific role of the lipase for the Cannizzaro-type
reaction. Bases such as triethylamine and imidazole are known to
act as catalyst/co-catalyst in various reactions of aryl aldehydes
Li, C.-J.; Chen, L. Chem. Soc. Rev. 2006, 35, 68.
8. General procedure for lipase catalyzed redox reaction of p-nitrobenzaldehyde. A
solution of p-nitrobenzaldehyde (1 mM) in 100 mM sodium phosphate buffer,
pH 7.0 was shaken with 20 mg lipase at 30 °C. Total reaction volume was
1.25 ml. Aliquots were taken at different points of time and analyzed by HPLC.
Experiments were done in duplicate and found to have ±5% error. HPLC analysis
was carried out on Zorbax C-18 reverse phase column (150 mm  4.6 mm). The
eluent was composed of 25% acetonitrile in water containing trifluoroacetic
acid (0.1%), at a flow rate of 1 ml/min. The peaks were detected at 254 nm and
the retention times were matched with those of commercially available
compounds. The amount of product formed at a given point of time was
calculated from the peak area(s) of the product(s).
16
17
such as Henry reaction, benzoin condensation, and aldol con-
1
8
densation. However, p-nitrobenzaldehyde did not show any sig-
nificant product formation in the presence of these bases under the
mild conditions used during biocatalysis (Table 2, entries 6 and 7).
To sum up, we believe that this is the first report of lipases car-
rying out a Cannizzaro-type reaction without the involvement of
any externally added redox reagent. Furthermore, the reaction
was carried out under benign conditions using water as the reac-
tion medium (and air as the oxidizing agent for the oxidation step).
Lipases are considered to have a very wide specificity among
9
1
.
Lewis, G. E. J. Org. Chem. 1965, 30, 2433.
0. Chung, S. K. J. Chem. Soc., Chem. Commun. 1982, 480.
11. Ashby, E. C.; Coleman, D.; Gamasa, M. J. Org. Chem. 1987, 52, 4079.
2. Alexander, E. R. J. Am. Chem. Soc. 1947, 69, 289.
1
1
3. Kluska, R. H.; Masarwa, A.; Saphier, M.; Cohen, H.; Meyerstein, D. Chem. Eur. J.
2008, 14, 5880.
14. Russell, G. A.; Janzen, E. G. J. Am. Chem. Soc. 1962, 84, 4153.
1
1
5. Swain, C. G.; Powell, A. L.; Sheppard, W. A.; Morgan, C. R. J. Am. Chem. Soc. 1979,
01, 3576.
6. Phukan, M.; Borah, K. J.; Borah, R. Synth. Commun. 2008, 38, 3068.
1
1
c,2d
enzymes.
The above results show that the range of reactions
17. Iwamoto, K.; Hamaya, M.; Hashimoto, N.; Kimura, H.; Suzuki, Y.; Sato, M.
Tetrahedron Lett. 2006, 47, 7157.
8. Chen, X.; Liu, B.-K.; Kang, H.; Lin, X.-F. J. Mol. Catal. B: Enzym. 2011, 68, 71.
which these enzymes catalyze may be even wider than thought
so far. This certainly expands their synthetic utility.
1
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