Environmentally benign and energy efficient methodology for condensation: An interesting facet to the classical Perkin reaction

Article abstract of DOI:10.1039/c0gc00712a

We have reported use of biodegradable deep eutectic solvent (DES) based on choline chloride and urea, for the synthesis of cinnamic acid and its derivatives via Perkin reaction. The reaction proceeds efficiently under mild condition without use of additional catalyst with better yields. Ease of recovery and reusability of solvent with consistent activity makes this method efficient and environmentally benign. This method is also energy efficient and easy to handle.

Full text of DOI:10.1039/c0gc00712a

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PAPER
Environmentally benign and energy efficient methodology for condensation:
an interesting facet to the classical Perkin reaction†
Poonam Mahadev Pawar, Krishna Jagannath Jarag and Ganapati Subray Shankarling*
Received 19th October 2010, Accepted 13th May 2011
DOI: 10.1039/c0gc00712a
We have reported use of biodegradable deep eutectic solvent (DES) based on choline chloride and
urea, for the synthesis of cinnamic acid and its derivatives via Perkin reaction. The reaction
proceeds efficiently under mild condition without use of additional catalyst with better yields.
Ease of recovery and reusability of solvent with consistent activity makes this method efficient and
environmentally benign. This method is also energy efficient and easy to handle.
Cinnamic acids have been synthesized by reacting aro-
1. Introduction
matic aldehydes with aliphatic carboxylic acids in N-methyl-
2-pyrrolidinone (NMP) at 180–190 ◦C in presence of either
Cinnamic acid and its derivatives are used in various fields
such as medicines1,2 perfumery, polymer, cosmetics3,4 and agri-
sodium borohydride27 or boron tribromide as a reagent and
cultural fields.5 They are also used as matrices for ultraviolet
4-dimethylaminopyridine (4-DMAP) and pyridine as bases.28
laser desorption mass spectrometry of protein,6 and as useful
Reaction time required to complete such type of reactions is
intermediates for the synthesis of heterocyclic compounds.7
8–10 h.
Conventionally, cinnamic acid and its derivatives are prepared
Microwave irradiation method is also used for Perkin re-
◦using benzaldehyde, acetic anhydride in presence of a base at 180
action. Cesium salts (acetate, carbonate, and fluoride) with
C.8 However, the conventional method has a lot of drawbacks
a small amount of pyridine29 or sodium acetate trihydrate30
such as use of strong and harmful base, organic solvents, higher
were used as catalysts for synthesis of cinnamic acid and its
reaction temperatures, longer reaction times and low yields.9 In
derivatives from aromatic aldehydes and acetic anhydride under
the literature various methods are reported to prepare cinnamic
microwave irradiation. Cinnamic acids were also synthesized
acid and its derivatives: Perkin reaction,10–14 halo-benzene with
from aromatic aldehydes and malonic acid on the surface
acrylic acid,15,16 benzaldehyde with acetone,17 benzaldehyde
of graphite under a microwave irradiation.31 Knoevenagel–
with ketene or acetic acid,18 from cinnamic aldehyde by air
Doebner synthesis used for preparation of cinnamic acid under
oxidation,19 styrene with carbon monoxide or carbon dioxide,20
microwave irradiation.32 Hydroxystilbenes with trans selectivity
and the hydrolyzation of 1,1,1,3-tetrachloro-3-phenylpropane
was synthesized through modified Perkin reaction between ben-
from styrene and CCl4.21 Cinnamic acid synthesis using the
zaldehydes and phenylacetic acids in the presence of piperidine–
Perkin condensation method involves use of different bases. The
methylimidazole and polyethylene glycol under microwave
effects of various bases such as fused sodium acetate, sodium
irradiation.33
formate, sodium tartrate, sodium borate, sodium sulfite, sodium
In spite of great variety of well known and established
carbonate, and potassium carbonate on yield of Perkin reaction
methods for cinnamic acid and its derivatives, organic solvents
and bases used in these transformations are high on the list
have been extensively studied.22 John et al.23 have reported
calcium hydrate as a catalyst and Ping et al.24 have reported
of hazardous and harmful chemicals because of their volatile
solid base K2O and Al2O3 as catalyst. NaF and K2CO3 are used
nature, considerable toxicity and their use in large quantities for
◦
as mixed catalyst for synthesis of cinnamic acid at 150 C–170
the reaction. To overcome these drawbacks Jianyang Weng34
◦C.25 Cinnamic acid and its derivatives are also synthesized from
and coworkers reported a process for synthesis of cinnamic
acid in quaternary ammonium ionic liquids at 120 ◦C for 8
benzaldehyde and malonic acid by Knoevenagel condensation
using pyridine as catalyst.26
h. The process developed by Jianyang Weng and coworkers
is environmentally benign, but higher reaction temperature
(120 ◦C) and longer reaction time (8 h) makes this process
Department of Dyestuff Technology, Institute of Chemical Technology,
more energy intensive. Therefore, development of new synthetic
protocols for cinnamic acid derivatives, inexpensive reagents and
environmentally benign conditions for such transformations is
still an active field for researcher.
N. P. Marg, Matunga, Mumbai, 400 019, India.
E-mail: gsshankarling@gmail.com, gs.shankarling@ictmumbai.edu.in;
Fax: +91-22-33611020; Tel: +91-22-33612708
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c0gc00712a
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In our previous attempt, deep eutectic solvent (DES) have
been used for the synthesis of dye intermediates and novel dyes.35
In the area of organic synthesis, energy efficiency calculation
is recent phenomenon. Pandit and coworkers have made the
systematic approach for calculating energy balance of the
process.36 We have also reported the energy balance for the
chalcone synthesis process.37
In the present work, we report the room temperature synthesis
of cinnamic acid and its derivatives in DES based on choline
chloride and urea. We have also made an attempt to compare
energy balance for both the conventional as well as DES
process.
Benzaldehyde was reacted with symmetric and unsymmetric
anhydrides in DES such as acetic anhydride,◦acetic propionic
anhydride and propionic anhydride at 30 2 C. The reaction
proceeds with the acetic and acetic propionic anhydride but not
with the propionic anhydride. This may be because of the +I
effect of the methyl group in propionic anhydride which reduces
the acidity of the –CH2 group (the results are summarized
in Table 2). The results were compared with the conventional
method for three compounds (1a–3a). In conventional method,
the aldehydes (1 mmol), acetic anhydride (2 mmol) and sodium
acetate (3 mmol) were refluxed at 140 ◦C for 9 h. Reaction was
monitored on TLC. Reaction mass is then quenched in 50 ml
ice cold water followed by acidification with 1 : 1 solution of
concentrated hydrochloric acid and water. After being cooled to
20 ◦C, the acid is filtered over suction and washed with a ice cold
water. Solid is filtered and dried in oven.
2. Results and discussion
Recyclable DES is utilized as a catalyst and reaction media
for Perkin condensation, avoiding the use of additional catalyst
1
All the compounds are characterized by H-NMR, FTIR,
◦
and organic solvent. All reactions are carried out at 30 2 C
mass spectrometry. The probable reaction mechanism is pro-
vided in Appendix II of the ESI.†
temperature. DES is a mixture of two compounds where there
is a depression in the freezing point of the mixture compared
with that of the separate components. It comprises mixtures
of organic halide salts with hydrogen-bond donors, such as
amides, amines, alcohols, and carboxylic acids.38 Preparation
of DES is easy and economically viable as it shows 100% atom
economy. It is non-toxic and biodegradable.39 Hence owing to
these properties, we synthesized cinnamic acid and its derivatives
via Perkin reaction using DES. The DES was prepared by
Recycling of the choline chloride
Simple experimental procedures, ease of recovery and reuse
of the reaction media contribute to the development of a
green approach for synthesizing cinnamic acid derivatives.
Experiments for testing the recyclability of DES were performed
using benzaldehyde and acetic anhydride as reactants. The
recovered DES was then successfully used for three runs showing
no significant loss of yield (Table 3). It has been confirmed
through NMR that structure of DES after reaction has been
not changed.
◦
reacting choline chloride with urea (1 : 2) at 80 C by reported
method40 (Scheme 1). The feasibility of the Perkin reaction
was examined using benzaldehyde as a model substrate. The
experimental procedure is very simple. Benzaldehyde (1 mmol),
acetic anhydride (1 mmol) and deep eutectic solvent (3 ml) were
stirred at room temperature. The reaction was monitored by
TLC. After completion, the reaction mass was diluted with
water. The white solid mass was separated by filtration. (Scheme
2) The DES was recovered easily from filtrate by evaporating the
water under vacuum. Product is purified from water followed by
methanol. DES was re-used for three succession of the reaction
without much loss of product yields.
Efficacy of energy utilization
Prasad et al.36 and our earlier research paper have reported the
procedure for the calculation of energy37 Appendix I shows
the comparison of the energy based performance of the two
types of synthesis methods, i.e. conventional and using DES for
synthesizing cinnamic acid (detailed information is provided in
the ESI†). The energy utilized for the synthesis of cinnamic acid
is the total energy supplied (kJ) per unit weight of the material
processed (g). The reaction time to synthesize cinnamic acid
was 4 h by DES method (1) and 9 h for conventional method
(1a). Total energy required per unit weight of the material
processed to synthesize cinnamic acid is 14.15 (kJ g-1) for DES
synthesis method and 37.85 (kJ g-1) for conventional synthesis
method.
Scheme 1 Schematic presentation of synthesis of DES based on choline
chloride and urea.
Thus, DES assisted method is proved to be energy efficient
which saved more than 62% of energy utilized by conventional
synthesis method and also a reduction in the reaction duration
was observed as reported in Table 1.
3. Experimental
Scheme 2 Schematic presentation of synthesis of cinnamic acid
derivatives, where R = aryl, heteroaryl.
3.1. Materials and equipment
From the above results, the reaction was tested for different
aromatic and heterocyclic aldehydes (results are summarized in
Table 1). The yields of the product were found to vary from
60–92%. The reaction is also studied for various anhydrides.
All melting points are uncorrected and are presented in
◦C. 1H NMR spectrums were recorded on Varian 499.85
MHz mercury plus spectrometer, and chemical shifts are
expressed in d (ppm) using TMS as an internal standard.
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Table 1 Synthesis of cinnamic acid derivatives using deep eutectic solventa and conventional methodb
Entry Substrate
1
Product
T/◦C
Reaction time (h)
4
Yieldc (%)
92
Mp (◦C), observed Mp (◦C), literature
30
2
132–133
131–133
175–176
131–13312
1a
2
140
30
9
4
60
90
2
176–17712
2a
140
9
62
176–177
3
30
2
4
9
8
8
9
92
63
60
75
62
230–233
232–234
211–212
254–255
133–135
233–23614
3a
4
140
30
2
2
2
213–215
5
30
255–25641
135–13738
6
30
7
8
30
30
2
2
6.5
7
68
65
184–185
115–116
185–18614
116–119
a Reaction condition: aromatic aldehydes: acetic anhydride, 1 : 1(mole ratio), DES, temp. 30
2
◦C. The reactions were monitored by thin layer
1
chromatography (TLC) analysis. All products were characterized by FT-IR, Mass, H NMR and their melting point matched previous literature.
b Conventional method: benzaldehyde, acetic anhydride, sodium acetate trihydrate, 1 : 2 : 3 (mole ratio), temp. 140 ◦C. c Isolated yields.
Mass spectral data were obtained with a micromass - Q -
TOF (YA105) spectrometer. FT-IR spectrum were recorded
on Perkin Elmer 100 FT spectrometer. Common reagent
grade chemicals were procured from SD Fine Chemical Ltd.
(Mumbai, India) and were used without further purification.
The reaction were monitored by TLC using 0.25 mm E-Merck
silica gel 60 F254 precoated plates, which were visualized with
UV light.
3.2 Synthesis of deep eutectic solvent
The synthesis of deep eutectic solvent has been carried out using
method reported in the literature.41 It is prepared by the mixing
of choline chloride (100 g, 71 mmol) and urea (86 g, 140 mmol)
in the ratio of 1 : 2. The two solids are then heated slowly and
maintained at 80 ◦C for 30 min resulting in the formation of
eutectic solvent with 100% atom economy. The liquid is allowed
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Table 2 Reaction using deep eutectic solvent with different aliphatic anhydridesa
Entry Substrate
1
Product
T/◦C
Reaction time (h)
4
Yield (%)
92
Mp (◦C), observed
132–133
Mp (◦C), literature
131–13312
30
30
30
2
2
2
2
3
6
85
—
131–133
—
—
a Reaction condition: benzaldehyde aldehydes: aliphatic anhydride, 1 : 1(mole ratio), DES, temp. 30 2 ◦C. The reactions were monitored by thin layer
chromatography (TLC) analysis. There is no reaction in case of entry 3.
◦
Table 3 Recycling of deep eutectic solvent for cinnamic acid formation
3-Pyridyl cinnamic acid (4). White Solid. m.p. 211–212 C;
reaction using benzaldehydea
n
max/cm-1 3000–2500 (O–H), 1678(C O), 1630 (C C); 1H-
NMR (499.85 MHz; DMSO; Me4 Si) d = 6.648–6.680 (1H, d,
J = 15.9 Hz), 7.591–7.623 (1H, d, J = 15.9 Hz), 8.121–8.144 (1H,
tt, J = 6.1 Hz), 8.553–8.565 (1H, dd, J = 4.9 Hz), 12.540 (1H, s);
EIMS m/z 149. C8H7NO2 calculated m/z: 149.15
Entry
Cycle
% Yield
1.
2.
3.
4.
Fresh
92
87
85
85
1st recycle
2nd recycle
3rd recycle
4-Cyano cinnamic acid (5). White Solid. m.p. 254–255 ◦C;
n
max/cm-1 3000–2500 (O–H), 1693(C O), 1627(C C); 1H-
a Reaction condition: benzaldehyde: acetic anhydride, DES.
NMR (499.85 MHz; DMSO; Me4 Si) d = 6.675–6.707 (1H, d,
J = 16.2), 7.607–7.639 (1H, d, J = 16.2), 7.838–7.891(4H, m),
12.623(1H, s); mz (EI) 149. C8H7NO2 calculated m/z: 149.15
to cool till it attains room temperature and is used for synthesis of
cinnamic acid and their derivatives without further purification.
3-Trifluoro methyl cinnamic acid (6). White Solid. m.p. 133–
135 ◦C; nmax/cm-1 3000–2500 (O–H), 1684(C O), 1630 (C C);
1H-NMR (499.85 MHz; DMSO; Me4 Si) d = 6.678–6.711 (1H,
d, J = 16.5 Hz), 7.613–7.645 (1H, t), 7.681–7.650 (1H, d, J =
15.9 Hz), 7.731–7.746 (1H, d) 7.996–8.012 (1H, d), 8.059 (1H,s),
12.522 (1H, s); EIMS m/z 216. C10H7F3O2 calculated m/z:
216.16
3.3 Cinnamic acid formation reaction: a typical procedure (1–8)
In a typical reaction, benzaldehyde (0.5 g, 4.7 mmol), acetic
anhydride (0.48 g, 4.7 mmol) and deep eutectic solvent (1.5 ml)
were mixed and stirred at 30
2
◦C in a round bottom flask
fitted with guard tube. The reaction was monitored by TLC.
After completion of reaction, water was added. The DES being
soluble in water comes in the water layer. The solid was separated
by filtration. It was purified with water followed by methanol and
dried in oven.
2-Methoxy cinnamic acid (7). White Solid. m.p. 180–182 ◦C;
n
max/cm-1 3000–2500 (O–H), 1682(C O), 1620 (C C); 1H-
NMR (499.85 MHz; DMSO; Me4 Si) d = 3.836–3.978 (3H, s),
6.481–6.513 (1H, d, J = 15.9 Hz), 6.940–6.971 (1H, t, J = 6.7
Hz), 7.040–7.056 (1H, d, J = 7.9 Hz), 7.359–7.387 (1H, t, J = 6.7
Hz), 7.641–7.653 (1H, d, J = 6.1 Hz), 7.816–7.847 (1H, d, J =
15.9 Hz); 12.315 (1H, s); EIMS m/z 178. C10H10O3 calculated
m/z: 178.18
Cinnamic acid (1). White solid. m.p. 131–133 ◦C; nmax/cm-1
3000–2500 (O–H), 1678(C O), 1630 (C C); 1H-NMR (499.85
MHz; DMSO; Me4 Si) d = 6.496–6.527 (1H, d, J = 15.9 Hz, C–
H), 7.392–7.397 (2H, d, J = 2.5 Hz), 7.557–7.589 (1H, d, J =
15.9 Hz), 7.657–7.667 (3H, t, J = 2.5 Hz), 12.384(1H, s); EIMS
m/z 147. C9H8O2 calculated m/z 148.05
3-Methoxy cinnamic acid (8). White solid. m.p. 115–116 ◦C;
n
max/cm-1 3000–2500 (O–H), 1680(C O), 1629 (C C); 1H-
NMR (499.85 MHz; DMSO; Me4 Si) d = 3.764 (3H, s), 6.524–
6.556 (1H, d, J = 15.8 Hz), 6.939–6.960 (1H, dd, J = 8.0 Hz),
7.206–7.221 (1H, d, J = 7.3 Hz), 7.276–7.308 (1H, t, J = 7.9 Hz),
7.540–7.573 (1H, d, J = 16.5 Hz), 12.392 (1H, s) EIMS m/z 178.
C10H10O3 calculated m/z: 178.18
3-Chloro cinnamic acid (2). White solid. m.p. 175–176 ◦C;
n
max/cm-1 3000–2500 (O–H), 1652(C O), 1602(C C); 1H-
NMR (499.9 MHz; DMSO; Me4 Si) d = 6.983–6.998 (1H, d,
CH), 7.047–7.093 (3H, m), 7.095–7.110 (1H, s), 12.006 (1H,
s);EIMS m/z 182. C9H7ClO2 calculated m/z: 182.6
DES before reaction. 1H NMR (300 MHz; CDCl3; Me4 Si)
d = 3.187 (9H), 3.505 (2H), 3.95 (2H), 4.424 (1H), 6.095 (8H).
13C NMR (75 MHz, CDCl3), d = 161.945, 67.804, 55.937,
54.006
2,4-Dichloro cinnamic acid (3). White Solid. m.p. 230–233
◦C; nmax/cm-1 3000–2500 (O–H), 1668(C O), 1602 (C C); 1H-
NMR (499.85 MHz; DMSO; Me4 Si) d = 6.779–6.796 (1H, d),
7.246–7.340 (3H, m), 7.354–7.370 (1H, d), 12.482 (1H, s); EIMS
m/z 216. C9H6Cl2O2 calculated m/z: 217.05
DES after reaction. 1H NMR (300 MHz; CDCl3; Me4 Si)
d = 3.193 (9H), 3.509 (2H), 3.978 (2H), 4.870(1H), 6.091 (8H).
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13C NMR (75 MHz, CDCl3), d = 162.003, 67.765, 55.937,
54.128
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anhydride (0.96 g, 9.4 mmol) and sodium acetate trihydrate
(1.93 g, 14.1 mmol) were mixed and stirred at 140 ◦C for 9 h
in round bottom flask fitted with reflux condenser. The reaction
was monitored on TLC. The reaction mass quenched in 20 ml
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at room temperature 30 2 C in a round bottom flask fitted
with guard tube. After 4 h, the reaction mixture became viscous
and solidified. The reaction was monitored by TLC. After
completion of reaction, water was added. The DES being soluble
in water comes in the water layer. The solid was separated by
filtration, purified from water and methanol and dried in oven
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Perkin condensation using biodegradable ammonium deep
eutectic solvent based on choline chloride and urea provides an
efficient and convenient method for the synthesis of cinnamic
acid and their derivatives. This method offers marked improve-
ments in terms of decreased reaction time, general applicability,
good isolated product yields, energy efficient reaction and the
use of environmentally benign procedures and solvents. This
method also eliminates the use of hazardous organic solvents
and toxic catalysts, and thus provides a better and practical
alternative to existing methods. Deep eutectic solvents provide a
good alternative for industrial synthesis as the reaction is readily
scalable. The recyclability and biodegradability of deep eutectic
solvent makes the process greener and economically more viable
for the synthesis of cinnamic acid as compared to the reported
protocols.
Acknowledgements
Authors are thankful to chemistry department, ICT, Mumbai,
for recording FT-IR. One of the authors, Ms Poonam M. Pawar,
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