Silica sulfuric acid-catalyzed Claisen-Schmidt condensation of 1,3,4 trisubstituted pyrrole 2,5 dione to chalcones

Article abstract of DOI:10.1007/s11164-012-0553-6

A series of 11 chalcones was synthesized from 1-(4-acetylphenyl)-3,4- dibromo-1H-pyrrole-2,5-dione with various substituted benzaldehyde under solvent-free conditions using silica-sulphuric acid as a catalyst. The yields of chalcones are more than 90 %. All the compounds were characterized by physical, spectroscopic, and elemental analysis. Springer Science+Business Media B.V. 2012.

Full text of DOI:10.1007/s11164-012-0553-6

Res Chem Intermed (2012) 38:2371–2381
DOI 10.1007/s11164-012-0553-6
Silica sulfuric acid-catalyzed Claisen-Schmidt
condensation of 1,3,4 trisubstituted pyrrole 2,5 dione
to chalcones
•
J. R. Patel M. H. Malani B. Z. Dholakiya
•
Received: 11 February 2012 / Accepted: 30 March 2012 / Published online: 25 April 2012
Ó Springer Science+Business Media B.V. 2012
Abstract A series of 11 chalcones was synthesized from 1-(4-acetylphenyl)-3,4-
dibromo-1H-pyrrole-2,5-dione with various substituted benzaldehyde under sol-
vent-free conditions using silica-sulphuric acid as a catalyst. The yields of chalcones
are more than 90 %. All the compounds were characterized by physical, spectro-
scopic, and elemental analysis.
Keywords 1-(4-Acetylphenyl)-3,4-dibromo-1H-pyrrole-2,5-dione ꢀ
Claisen-Schmidt reaction ꢀ SiO2–H2SO4
Introduction
Since their development in the 1970s, Claisen-Schmidt reactions catalyzed by
strong base or Lewis acids have become one of the most important tools for
constructing chalcones. Traditionally, carbomethyls were widely studied and
broadly used as the electrophile, both in the laboratory an in industry. However,
with the further development of catalytic systems, a variety of electrophiles have
now been successfully applied to the Claisen-Schmidt reaction.
The chalcones are a,b-unsaturated ketones containing the reactive ketoethylenic
group –CO–CH=CH–. The presence of a,b-unsaturated carbonyl system in chalcone
makes it biologically active [1]. Chalcones (a,b unsaturated ketone) are natural
substances found in a number of plants or can also be synthetically prepared. They
display many biological activities, for example, antiviral, anti-inflammatory, anti-
microbial, antimitotic, antitumor, cytotoxicity, analgesic, and antipyretic properties.
They also act as potential antiulcer, antifungal, anti-cancer, and antimalarial agents
J. R. Patel ꢀ M. H. Malani ꢀ B. Z. Dholakiya (&)
Department of Applied Chemistry, S.V. National Institute of Technology, Ichhanath, Surat 395007,
Gujarat, India
e-mail: bzd.svnit@gmail.com
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[2]. Recently there has been tremendous interest in the application of solvent-free
methods in organic reactions such as the Claisen-Schmidt, Knoevenagel, aldol, and
crossed-aldol [3]. There has been tremendous interest in the application of solvent-
free aldol and crossed-aldol reactions, which are employed for synthesis of carbonyl
compounds due to the operational simplicity, easier work-up, better yield, and eco-
friendly nature [4]. Among reported solid acids, silica sulfuric acid has been used to
catalyze a wide variety of reactions ranging from aldol condensation, acetalization,
deacetalization, oxidation of alcohols, N-nitrosation of secondary amines, direct
etherification of trimethylsilyl ethers [5] and formation of carbamate [6], and
oxidation of alcohol [7]. The promoting effect of silica-sulphuric acid in their
reaction was shown good performance and it is proved by obtaining higher
percentage of yields. The product was isolated and the remaining catalyst was
washed and reused with fresh substrate for further reactions. No decrease in the
yield was observed, demonstrating that silica-sulphuric acid can be reused in the
Claisen-Schmidt condensation reaction without environmental discharge [8].
Our group has worked to directly apply abundant and readily available oxygen-
containing compounds such as o-and p-substituted acetophenones. In this account, we
describe our recent efforts in silica-sulphuric acid-catalyzed Claisen-Schmidt reaction
of 1-(4-acetylphenyl)-3,4-dibromo-1H-pyrrole-2,5-dione, a versatile electrophile.
Results and discussion
The important infrared spectral bands and their tentative assignments for dibromo
compounds and its chalcones were recorded as KBr disks and are presented in
1
experimental section. H NMR spectra revealed signals 3.35 d ppm for DMSO
1
solvent and 3.53 d & 8.12 d ppm for DMF solvent. H NMR data of compound
1
revealed singlet at 2.58 d ppm for –CH3 group. The H NMR data of compounds
2a–h revealed signals between 6.78 and 8.50 d ppm for aromatic protons. The IR
spectra of compounds 2a–h revealed a characteristic band between 3,020 and
3,090 cm-1 confirming the presence of (C=C) groups. The 1H NMR data of
compounds revealed signals between 2.48 and 2.53 d ppm and 2.74–2.80 d ppm for
asymmetric aliphatic (C=C) of chalcones (Fig. 1). IR spectrum of the compounds
showed a characteristic bands between 1,580 and 1,716 cm-1, confirming the
presence of C=O groups and C–Br present between 537 and 655 cm-1of
dibromomaleimides. 13C NMR spectra of compounds showed a characteristic peak
around 40.1, 77, 118, 124, 126.9, 127.85, 129, 130.22, 131.01, 138, 167.78, and 171
d ppm (Fig. 2). IR spectrum of the compound 2c showed a characteristic band at
1,410 cm-1, confirming the presence of –NO2 group. 13C NMR spectra of
compounds 2c showed a characteristic peak around 39.91, 57.22, 76, 118, 124, 129,
130, 131, 138, 140, 143, 148, 168, and 172. In mass spectral studies, molecular ion
peak for the compound 2e have been used to confirm the molecular formulae. The
first peak at m/z 492 (M?) represents the molecular ion peak of the compound.
Molecular ion peak again confirmed by fragments observed in mass spectra at m/
z 410, 386, 354, 254 until stable fragment is formed (Figs. 3, 4).
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Silica sulfuric acid catalyzed Claisen-Schmidt condensation
2373
Fig. 1 1H NMR spectrum of compound 2b
Conclusions
This method is a very efficient and selective protocol for Claisen-Schmidt
condensation of 1-(4-acetylphenyl)-3,4-dibromo-1H-pyrrole-2,5-dione in the pres-
ence of silica sulfuric acid catalyst. Operative simplicity and easy work-up process
this approach provides better yielded products. The results obtained from this study
reconfirmed that the product has formed.
Experimental
Materials and instrumentation
All reagents were of analytical reagent grade and were used without further
purification. Solvents employed were purified by standard procedure before use. The
melting points were determined in open capillary on Veego (Model: VMP-D)
electronic apparatus and are uncorrected. To monitor the reactions as well as to
establish the identity and purity of reactants and products, thin-layer chromatog-
raphy was performed on microscopic glass slides (2 9 7.5 cm) coated with silica
gel-G, using toluene-acetone and chloroform–methanol, as the solvent systems and
spots were visualized under UV radiation. Elemental analysis (C, H, N) was
123

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J. R. Patel et al.
Fig. 2 13 C NMR spectrum of compound 2c
Fig. 3 ESI mass spectrum of compound 2e
performed using a PerkinElmer, USA 2400-II CHN analyzer. FTIR spectra
(4,000–400 cm-1) recorded on a Simadzu 8400-S spectrophotometer using a KBr
disk. Nuclear magnetic resonance spectra were recorded on a Varian 400-MHz
model spectrometer using DMSO and or DMF as a solvent and TMS as internal
reference (chemical shifts in d ppm).
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Silica sulfuric acid catalyzed Claisen-Schmidt condensation
2375
Fig. 4 Suggested mass
fragmentation pattern of
compound 2e
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J. R. Patel et al.
Preparation of chalcone from dibromomaleimide (2a–h)
The target compounds were prepared as shown in Scheme 1. An equimolar mixture
of 1-(4-acetylphenyl)-3,4-dibromo-1H-pyrrole-2,5-dione 1 [9–11] (2 g), aromatic
aldehydes (2.1 g) and silica sulfuric acid prepared by reported method [12] (1.5 g
equal to 4 mmol of H?) were mixed thoroughly, placed in a glass tube, and capped
(Scheme 1). The mixture was heated in an oven at 80 °C for 2–3.5 h. After
complete conversion of the ketones, reactions were monitored by TLC, the mixture
was cooled to room temperature. Dichloromethane (20–30 ml) was added and
heated for 3–5 min. The reagent was removed by filtration. The filtrate was
concentrated and the solid residue was recrystallized from ethanol to afford final
product. The catalyst was recycled by washing ethyl acetate (20 ml) on solid
remaining on the filter followed by drying in an oven at 50 °C for 2 h, which can be
reusable for another reaction run. Spectral and microanalysis data of selective
compounds are summarized below [13]. New compounds were completely
characterized based on their spectroscopy data. Derivatives are shown in
Table 1.
1-(4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-dione 2a
1
Yellow solid, Yield 97 %; m.p. 149 °C; H NMR (500 MHz, DMF), 3.52 d and
8.23 d ppm (DMF solvent), 7.45 d ppm (1H, d, J = 15.5 Hz, E-vinylic-H), 7.66 d
ppm (2H, dd, Ar–H), 6.43–7.42 (5H, m, Ar–H), 7.75 d ppm (1H, d, J = 15.5 Hz,
E-vinylic-H); 13C NMR (500 MHz, DMF) 40.1, 77, 118, 124, 126.9, 127.85, 129,
130.22, 131.01, 138, 167.78, 171 d ppm; FTIR (KBr) tmax cm-1: 3028 (C=C), 1716
(C=O), 1527 (C=C of Ar), 835 (p-disubstituted Ar), 655 (C–Br); ESIMS m/z 462
(M ? 1) Anal. Calcd for CHNOBr: C, 49.49; H, 2.40; N, 3.04 Found: C, 49.44; H,
2.38; N, 2.99.
1-(30,40-Dimethoxy-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-
dione 2b
Yellow solid, Yield 95 %; m.p. 116 °C; 1H NMR (500 MHz, DMF) 2.9 d ppm (3H,
s, -OCH3), 3.04 d ppm (3H, s, –OCH3), 3.55 d and 8.063 d ppm (DMF solvent),
Br
Br
O
O
SiO2-H2SO4
R3
Br
Br
N
R3
R2
N
O
O
CH3
R2
O
R1
O
R1
1
2(a-k)
CHO
Scheme 1 Synthesis of compounds 2a–k from 1-(4-acetylphenyl)-3,4-dibromo-1H-pyrrole-2,5-dione 1
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Silica sulfuric acid catalyzed Claisen-Schmidt condensation
2377
Table 1 List of compounds 2a–k with their structures and groups
Structure of compounds
2a (R1, R2 & R3 = H)
2b (R1 = H, R2 & R3 = OCH3)
2c (R1= H, R2= -NO2 & R3=OCH3)
2d (R1= OH, R2& R3 =H)
2e (R1 & R2= H, R3 = Cl)
2f (R1= Cl & R2& R3 =H)
2g (R1 & R2= H, R3=CH3)
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J. R. Patel et al.
Table 1 continued
Structure of compounds
2h (R1 & R2= H, R3=OCH3)
2i (R1 & R2= H, R3 = OH)
2j (R1& R3= H, R2= -NO2)
2k (R1= H & R2& R3 = Cl)
7.56 d ppm (1H, d, J = 15.3 Hz, E-vinylic-H), 6.78–7.68 d ppm (2H, dd, Ar–H),
7.81 d ppm (1H, d, J = 15.3 Hz, E-vinylic-H), 6.38–8.37 d ppm (3H, m, Ar–H); 13
C
NMR (500 MHz, DMF) 41.21, 58.2,62.3, 76.44, 118, 124, 129, 129.8, 131, 131.1,
132, 137.6, 139.9, 144, 167.8, 171d ppm; FTIR (KBr) tmax cm-1: 3000 (C=C), 1580
(C=O), 1520 (C=C of Ar), 835 (p-disubstituted Ar), 650 (C–Br); ESIMS m/z 523
(M ? 2) Anal. Calcd for CHNOBr: C, 48.40; H, 2.90; N, 2.69 Found: C, 48.39; H,
2.99; N, 2.64.
1-(30-Nitro, 40-methoxy-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-
dione 2c
Orange solid, Yield 92 %; m.p. 118 °C; 1H NMR (500 MHz, DMF) 3.0 d ppm (3H,
s, –OCH3), 3.53 d and 8.12 d ppm (DMF solvent), 7.44 d ppm (1H, d, J = 15.4 Hz,
E-vinylic-H), 6.78–7.68 d ppm (2H, dd, Ar–H), 7.78 d ppm (1H, d, J = 15.4 Hz,
E-vinylic-H) 6.55–8.45 d ppm (3H, m, Ar–H); 13C NMR (500 MHz, DMF) 39.91,
123

Silica sulfuric acid catalyzed Claisen-Schmidt condensation
2379
57.22, 76, 118,124,127, 129, 130,131,138,140,143,148,168,172 d ppm; FTIR (KBr)
tmax cm-1: 2990 (C=C), 1589 (C=O), 1510 (C=C of Ar), 1250 (C–O), 840 (p-
disubstituted Ar), 653 (C–Br); ESIMS m/z 537 (M ? 1) Anal. Calcd for CHNOBr:
C, 44.81; H, 2.26; N, 5.23 Found: C, 44.79; H, 2.23; N, 5.25.
1-(20-Hydroxyl-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-dione
2d
Orange solid, Yield 93 %; m.p. 42 °C; 1H NMR (500 MHz, DMF) 3.34 d ppm (1H,
s, –OH), 3.50 d and 8.1 d ppm (DMF solvent), 7.56 d ppm (1H, d, J = 15.2 Hz,
E-vinylic-H) 6.73–7.74 d ppm (2H, dd, Ar–H), 7.77 d ppm (1H, d, J = 15.2 Hz,
E-vinylic-H) 6.45–8.2 d ppm (4H, m, Ar–H), 13C NMR (500 MHz, DMF) 40,
75.77,118, 127, 128, 131, 127, 129, 130, 138, 140.2, 142, 168, 170.98 d ppm; FTIR
(KBr) tmax cm-1: 3350 (–OH), 3084 (C=C), 1597 (C=O), 1525 (C=C of Ar), 1410
(NO2), 1230 (C–O), 840 (p-disubstituted Ar), 537 (C–Br); ESIMS m/z 477 (M?)
Anal. Calcd for CHNOBr: C, 47.83; H, 2.32; N, 2.92 Found: C, 47.85; H, 2.29; N,
2.96.
1-(40-Chloro-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-dione 2e
1
Yellow solid, Yield 98 %; m.p. 163 °C; H NMR (500 MHz, DMF) 3.55 d and
8.063 d ppm (DMF solvent), 7.6 d ppm (1H, d, J = 15.3 Hz, E-vinylic-H),
6.78–7.68 d ppm (2H, dd, Ar–H), 7.78 d ppm (1H, d, J = 15.3 Hz, E-vinylic-H),
6.55–8.45 d ppm (4H, m, Ar–H); 13C NMR (500 MHz, DMF) 39.9, 75.23, 118, 124,
127, 129, 129.4, 130, 140, 138, 140, 166.78, 171.2 d ppm; FTIR (KBr) tmax cm-1
:
3020 (C=C), 1585 (C=O), 1525 (C=C of Ar), 835 (p-disubstituted Ar), 697 (C–Cl),
538 (C–Br); ESIMS m/z 492 (M?) Anal. Calcd for CHNOBr: C, 47.83; H, 2.32; N,
2.92 Found: C, 47.85; H, 2.29; N, 2.96.
1-(20-Chloro-4-((E)-3-arylacryloyl) phenyl)-3, 4 dibromo-1H-pyrrole-2,5-dione 2f
1
Yellow solid, Yield 93 %; m.p. 166 °C; H NMR (500 MHz, DMF) 3.53 d and
8.063 d ppm (DMF solvent), 7.54 d ppm (1H, d, J = 15.5 Hz, E-vinylic-H),
6.77–7.66 d ppm (2H, dd, Ar–H), 7.82 d ppm (1H, d, J = 15.5 Hz, E-vinylic-H),
6.53–8.44 d ppm (4H, m, Ar–H); 13C NMR (500 MHz, DMF) 40.01, 75.23, 118.5,
123, 128, 129,131,133, 137, 138, 140, 167, 171 d ppm; FTIR (KBr) tmax cm-1
:
3022 (C=C), 1578 (C=O), 1527 (C=C of Ar), 836 (p-disubstituted Ar), 700 (C–Cl),
654(C–Br); ESIMS m/z 493 (M ?1) Anal. Calcd for CHNOBr: C, 47.85; H, 2.29; N,
2.93 Found: C, 47.87; H, 2.31; N, 2.97.
1-(40-Methyl-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-dione 2g
Pale yellow solid, Yield 96 %; m.p. 170 °C; 1H NMR (500 MHz, DMF) 3.37d ppm
(3H, s, –CH3) 3.54 d and 8.02 d ppm (DMF solvent), 7.67 d ppm (1H, d,
J = 15.2 Hz, E-vinylic-H), 6.76–7.68 d ppm (2H, dd, Ar–H), 7.77 d ppm (1H, d,
J = 15.2 Hz, E-vinylic-H), 6.51–8.43 d ppm (4H, m, Ar–H); 13C NMR (500 MHz,
123

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J. R. Patel et al.
DMF) 40.12,57, 72, 118, 123.2, 128, 129, 131.1, 133, 137.2, 138, 140.1, 162.8, 171
d ppm; FTIR (KBr) tmax cm-1: 3030 (C=C), 1582 (C=O), 1529 (C=C of Ar), 839
(p-disubstituted Ar), 657(C–Br); ESIMS m/z 476 (M ? 1) Anal. Calcd for
CHNOBr: C, 50.56; H, 2.76; N, 2.95 Found: C, 50.53; H, 2.78; N, 2.93.
1-(40-Methoxy-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-dione 2h
1
Yellow solid Yield, 92 %; m.p. 158 °C; H NMR (500 MHz, DMF) 3.01 d ppm
(3H, s, –OCH3), 3.53 d and 8.13 d ppm (DMF solvent), 7.68 d ppm (1H, d,
J = 15.5 Hz, E-vinylic-H), 6.72–7.63 d ppm (2H, dd, Ar–H), 7.76 d ppm (1H, d,
J = 15.5 Hz, E-vinylic-H) 6.39–8.39 d ppm (3H, m, Ar–H); 13C NMR (500 MHz,
DMF) 41.2, 58.21, 76.43, 119, 125, 129, 129, 129.9, 131.2, 133, 137.6, 140, 143,
167, 173 d ppm; FTIR (KBr) tmax cm-1: 3000 (C=C), 1580 (C=O), 1600 (C=C of
Ar), 835 (p-disubstituted Ar), 650 (C–Br); ESIMS m/z 492 (M ? 1) Anal. Calcd for
CHNOBr: C, 48.91; H, 2.67; N, 2.85 Found: C, 48.89; H, 2.64; N, 2.83.
1-(40-Hydroxyl-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-dione 2i
1
Orange solid, Yield 48 %; m.p. 41–43 °C; H NMR (500 MHz, DMF) 3.34 d ppm
(1H, s, –OH), 3.52 d and 8.12 d ppm (DMF solvent), 7.56 d ppm (1H, d,
J = 15.2 Hz, E-vinylic-H) 6.73–7.74 d ppm (2H, dd, Ar–H), 7.77 d ppm (1H, d,
J = 15.2 Hz, E-vinylic-H) 6.45–8.2 d ppm (4H, m, Ar–H), 13C NMR (500 MHz,
DMF) 41, 75.7, 116, 126, 127, 131, 127, 129, 129.4, 130, 138, 139, 142, 167, 168.9
d ppm; FTIR (KBr) tmax cm-1: 3350 (–OH), 3084 (C=C), 1597 (C=O), 1525 (C=C
of Ar), 1230 (C–O), 840 (p-disubstituted Ar), 537 (C–Br); ESIMS m/z 477 (M?)
Anal. Calcd for CHNOBr: C, 47.83; H, 2.32; N, 2.92 Found: C, 47.80; H, 2.31; N,
2.94.
1-(30-Nitro-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-dione 2j
Dark yellow solid, Yield 71 %; m.p. 146 °C; 1H NMR (500 MHz, DMF) 3.53 d and
8.12 d ppm (DMF solvent), 7.44 d ppm (1H, d, J = 15.4 Hz, E-vinylic-H),
6.78–7.68 d ppm (2H, dd, Ar–H), 7.78 d ppm (1H, d, J = 15.4 Hz, E-vinylic-H)
6.55–8.45 d ppm (3H, m, Ar–H); 13C NMR (500 MHz, DMF) 38, 74, 117, 124, 128,
129.9, 131, 138, 141, 143, 146, 169, 171 d ppm; FTIR (KBr) tmax cm-1: 2990
(C=C), 1589 (C=O), 1510 (C=C of Ar), 1410 (NO2), 1250 (C–O), 840 (p-
disubstituted Ar), 653 (C–Br); ESIMS m/z 507 (M ? 1) Anal. Calcd for CHNOBr:
C, 45.09; H, 1.99; N, 5.54 Found: C, 44.99; H, 2.01; N, 5.54.
1-(20,40-Dichloro-4-((E)-3-arylacryloyl) phenyl)-3,4 dibromo-1H-pyrrole-2,5-dione
2k
1
Orange solid Yield 79 %; m.p. 158 °C; H NMR (500 MHz, DMF) 3.55 d and
8.063 d ppm (DMF solvent), 7.6 d ppm (1H, d, J = 15.3 Hz, E-vinylic-H),
6.78–7.68 d ppm (2H, dd, Ar–H), 7.78 d ppm (1H, d, J = 15.3 Hz, E-vinylic-H),
6.55–8.45 d ppm (3H, m, Ar–H); 13C NMR (500 MHz, DMF) 40,77, 118, 123, 128,
123

Silica sulfuric acid catalyzed Claisen-Schmidt condensation
2381
129,130, 138,141,142,165, d ppm; FTIR (KBr) tmax cm-1: 3020 (C=C), 1585
(C=O), 1525 (C=C of Ar), 835 (p-disubstituted Ar), 697 (C–Cl), 538 (C–Br);
ESIMS m/z 530 (M?) Anal. Calcd for CHNOBr: C, 43.06; H, 1.71; N, 2.64 Found:
C, 42.93; H, 1.69; N, 2.65.
Acknowledgments The author wishes thank to the Department of Applied Chemistry, SVNIT, Surat,
for providing laboratory facilities. Analytical facilities provided by the Centre of Excellence, Vapi and
Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat, India, are gratefully
acknowledged.
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