Eco-friendly and facile one-pot multicomponent synthesis of acridinediones in water under microwave

Article abstract of DOI:10.1002/jhet.508

A rapid, improved, and environmentally benign synthesis of 4-arylacridinediones is reported via one-pot multicomponent reaction of aromatic aldehydes, dimedone, and ammonium acetate in water without any catalyst under microwave irradiation. Excellent yiel

Full text of DOI:10.1002/jhet.508

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January 2011
Eco-Friendly and Facile One-Pot Multicomponent Synthesis of
Acridinediones in Water under Microwave
69
Satish Kumar Singh and Krishna Nand Singh*
Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221005, India
*E-mail: knsinghbhu@yahoo.co.in
Received December 3, 2009
DOI 10.1002/jhet.508
Published online 2 September 2010 in Wiley Online Library (wileyonlinelibrary.com).
A rapid, improved, and environmentally benign synthesis of 4-arylacridinediones is reported via one-
pot multicomponent reaction of aromatic aldehydes, dimedone, and ammonium acetate in water without
any catalyst under microwave irradiation. Excellent yields, shortest reaction time, and easy work-up are
attractive features of this green protocol.
J. Heterocyclic Chem., 48, 69 (2011).
INTRODUCTION
4-Aryl-1,4-dihydropyridines (1,4-DHPs) are valuable
drugs for the treatment of cardiovascular disorders [6],
and constitute an important class of calcium channel
blockers [7]. Slight structural modification on the dihy-
dropyridine ring may result in a remarkable change in
its pharmacological effect [8]. Acridine-1,8-diones con-
taining a 1,4-DHP parent nucleus, are endowed with a
very high lasing efficiencies and are used as photoinitia-
tors [9]. As a result, acridinediones have been recently
synthesized by a number of methods [10–20]. However,
many of these methods suffer from drawbacks such as
the use of hazardous organic solvents, long reaction
time, low-yield, formation of side products and multi-
step synthesis. Subsequently, there stands a demand and
scope to develop an efficient, facile and eco-safe
approach to achieve acridinediones.
One-pot multicomponent reactions (MCRs) have
emerged as an effective tool for atom economic and be-
nign synthesis by virtue of their convergence, productiv-
ity, facile execution, and generation of highly diverse
and complex product from easily available starting
materials in a single operation. MCRs are now being tai-
lored and tuned for synthesizing various heterocyclic
scaffolds for diverse applications [1]. The environmental
acceptability of the process is improved if the multicom-
ponent strategy is applied under microwave irradiation
(MW) [2]. For many chemical processes, a major
adverse effect to the environment is the consumption of
energy for heating and cooling. To overcome this prob-
lem, it is highly desirable to develop efficient methods
that use microwave irradiation. Microwave heating pro-
vides a valuable tool to perform reactions faster with
enhanced product yields with high purities by reducing
unwanted side reactions [3]. In addition, aqueous medi-
ated reactions have recently received considerable
attention in organic synthesis, because of both economic
and environmental safety reasons. Because of the low-
solubility of common organic compounds in water, the
use of water as solvent often makes the purification of
products very easy by simple filtration or extraction [4].
The use of water as an environmentally benign solvent
for chemical transformations employing microwave
irradiation has become the demand of the present day
research [5].
RESULTS AND DISCUSSION
We describe herein a versatile, environmentally be-
nign, one-pot multicomponent synthesis of 4-arylacridi-
nediones by the reaction of aromatic aldehydes, dime-
done, and ammonium acetate under controlled micro-
wave irradiation in water without the use of any catalyst
(Scheme 1).
To optimize the reaction conditions, we undertook a
model reaction of benzaldehyde 1a, dimedone 2, and
ammonium acetate 3 in solvents viz., methanol, ethanol,
acetonitrile, and water using different MW powers at
C
V
2010 HeteroCorporation

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70
S. K. Singh and K. N. Singh
Vol 48
Scheme 1
A plausible mechanism for the formation of acridine-
diones 4 is outlined in scheme 2. The reaction is initi-
ated by the Knoevenagel type condensation of aldehyde
1 with a molecule of dimedone 2 giving 5; and simulta-
neously condensation of another mole of dimedone 2
with ammonium acetate 3 to provide enaminone 6. The
subsequent Michael addition of 6–5 followed by intra-
molecular cycloaddition and dehydration finally affords
the product 4.
different temperatures. The results are shown in Table 1
and reveal that water (entry 15) is the best choice as
medium for the said reaction with excellent product
yield (94%) using 220 W power at 100ꢀC. A marginally
low-performance was displayed by acetonitrile (entry
12), whereas ethanol and methanol could not do well.
Therefore, water was opted as the solvent for the subse-
quent reactions on the merit of higher yield, green na-
ture, and easy work-up as compared with acetonitrile.
Under the optimized set of reaction conditions (entry
15), a number of aromatic aldehydes 1 were allowed to
undergo MCR with dimedone 2 and ammonium acetate
3 in a molar ratio of 1:2:1.5 in water under microwave
(220 W, 100ꢀC) heating. The reactions were carried out
for 3–5 min, and the results are given in Table 2. All
the electron-rich and electron deficient aldehydes
worked well, leading to excellent yields of the products.
The progress of the reaction was monitored by TLC
(hexane/ethyl acetate; 8:2). Upon completion of the
reaction, the mixture was allowed to cool, and the
resulting solid was filtered and dried at room tempera-
ture. The crude material was purified by recrystallization
from methanol to afford pure substituted acridinediones
4a–4l in excellent yields (88–95%). All the products
were crystalline and fully characterized on the basis of
their melting points, elemental analyses, and spectral
CONCLUSION
In conclusion, we have developed a new, facile, and
efficient methodology for the eco-compatible preparation
of substituted acridinediones via one-pot three compo-
nent condensation of aromatic aldehyde, dimedone, and
ammonium acetate in an aqueous medium. The mildness
of the conversion, experimental simplicity, compatibility
with various functional groups, excellent product yield,
shorter reaction time, and the easy work-up procedure
makes this approach more attractive in synthesizing a
variety of such derivatives.
EXPERIMENTAL
All the chemicals were procured from Aldrich, USA, and E.
Merck, Germany and were purified before their use. IR spectra
were recorded on a JASCO FT/IR-5300 spectrophotometer.
NMR spectra were run on a JEOL AL300 FTNMR spectrome-
ter; chemical shifts are given in d ppm, relative to TMS as in-
ternal standard. Elemental microanalysis was performed on
Exeter Analytical Inc Model CE-440 CHN Analyzer. Melting
points were measured in open capillaries and are uncorrected.
The microwave irradiation was effected using the CEM’s Dis-
cover Bench Mate single-mode microwave synthesis system
1
data (IR, H NMR, and 13C NMR).
Table 1
Optimization of reaction conditions using compound 1a.
Microwave
Entry
Solvent
MW (Watt)
Temp. (ꢀC)
Time (min)
Yield (%)
1
2
Ethanol
Ethanol
Ethanol
120
120
180
220
120
120
180
220
120
120
180
220
180
180
220
250
60
80
5
5
5
5
5
5
5
5
5
5
5
5
5
5
3
3
57
58
69
72
43
43
58
64
60
66
83
92
71
87
94
92
3
4
100
100
60
Ethanol
5
6
Methanol
Methanol
Methanol
Methanol
Acetonitrile
Acetonitrile
Acetonitrile
Acetonitrile
Water
80
7
100
100
60
8
9
10
11
12
13
14
15
16
80
100
100
80
Water
Water
Water
100
100
100
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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January 2011
Eco-friendly and Facile One-pot Multicomponent Synthesis of Acridinediones in
Water Under Microwave
71
Table 2
Microwave induced synthesis of acridinedione derivatives in water.a
Mp (ꢀC)
Entry
Ar
Product
Time (min)
Yieldb (%)
Obs
Lit
1
2
C6H5
4-CH3C6H4
4-CH3OC6H4
4-ClC6H4
4a
4b
4c
4d
4e
4f
4g
4h
4i
3
3
3
3
3
3
3
3
5
5
3
3
94
95
93
94
92
94
91
92
90
89
88
90
251–252
227–228
266–267
>300
281–282
234–235
288–289
275–276
261–262
285–286
>300
250–252 [10b]
>300 [18]
269–270 [13]
296–298 [13]
3
4
5
3-ClC6H4
4-BrC6H4
3-BrC6H4
4-FC6H4
–
6
7
–
–
8
9
–
–
4-NO2C6H4
3-NO2C6H4
4-OH-3-CH3OC6H3
4-(CH3)2NC6H4
10
11
12
4j
4k
4l
285–286 [13]
296–298 [16]
264–266 [13]
256–257
a Microwave heating performed on 220 W power and 100ꢀC temperature.
b Isolated yield.
using safe pressure regulation 10-mL pressurized vials with
‘‘snap-on’’ cap.
CDCl3): d ¼ 190.5, 190.1, 146.3, 146.7, 134.5, 133.2, 129.2,
128.7, 114.8, 113.6, 55.7, 48.1, 45.6, 32.3, 30.4, 27.7, 26.8,
21.3; Anal. Calcd. for C24H29NO2: C, 79.30; H, 8.04; N, 3.85;
Found: C, 79.37; H, 7.90; N, 3.91.
General procedure for the synthesis of acridinediones
4. A mixture of aldehyde 1 (1 mmol), dimedone 2 (2 mmol),
ammonium acetate 3 (1.5 mmol), and water (2 mL) was placed
in a sealed pressure regulation 10-mL pressurized vial with
‘‘snap-on’’ cap and was irradiated in the single-mode microwave
synthesis system at 220 W power and 100ꢀC temperature for 3–
5 minutes. After completion of reaction (TLC), the mixture was
cooled and the resulting product was filtered, dried, and recrys-
tallized from methanol to afford the pure product 4a–4l.
3,3,6,6-Tetramethyl-9-phenyl-3,4,6,7,9,10-hexahydro-(2H,5H)-
acridine-1,8-dione (4a). Light yellow solid; IR (KBr): 3275,
9-(4-Methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexa-
hydro-(2H,5H)-acridine-1,8-dione (4c). Light yellow solid;
1
IR (KBr): 3296, 2947, 1645, 1628, 1605 cmꢁ1; H NMR (300
MHz, CDCl3): d ¼ 11.78 (s, 1H, NH), 6.58–7.23 (m, 4H, Ar-
H), 5.48 (s, 1H, CH), 3.75 (s, 3H, OCH3), 2.33–2.38 (m, 8H,
CH2), 1.22 (s, 6H, CH3), 1.10 (s, 6H, CH3); 13C NMR (75
MHz, CDCl3): d ¼ 190.7, 190.4, 149.8, 147.7, 140.1, 129.3,
128.5, 115.7, 113.9, 55.8, 47.6, 37.7, 32.3, 29.5, 27.9, 27.6;
Anal. Calcd. for C24H29NO3: C, 75.96; H, 7.70; N, 3.69;
Found: C, 76.11; H, 7.64; N, 3.77.
1
2958, 1652, 1627, 1601 cmꢁ1; H NMR (300 MHz, CDCl3): d
¼ 7.03–7.34 (m, 5H, Ar-H), 6.25 (s, 1H, NH), 5.08 (s, 1H,
CH), 2.18–2.39 (m, 8H, CH2), 1.08 (s, 6H, CH3), 0.97 (s, 6H,
CH3); 13C NMR (75 MHz, CDCl3): d ¼ 195.8, 149.0, 146.6,
128.0, 125.9, 113.3, 50.8, 40.7, 33.6, 32.6, 29.5, 27.1; Anal.
Calcd. for C23H27NO2: C, 79.05; H, 7.79; N, 4.01; Found: C,
78.93; H, 7.85; N, 3.97.
9-(4-Chlorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahy-
dro-(2H,5H)-acridine-1,8-dione (4d). Colourless solid; IR
(KBr): 3305, 2952, 1640, 1602 cmꢁ1 1H NMR (300 MHz,
;
CDCl3): d ¼ 11.86 (s, 1H, NH), 7.21–7.24 (m, 2H, Ar-H), 6.99–
7.02 (m, 2H, Ar-H), 5.47 (s, 1H, CH), 2.27–2.49 (m, 8H, CH2),
1.21 (s, 6H, CH3), 1.09 (s, 6H, CH3); 13C NMR (75 MHz,
CDCl3): d ¼ 190.6, 189.4, 136.7, 131.5, 128.3, 128.1, 115.3,
47.0, 46.4, 32.4, 31.4, 29.6, 27.4; Anal. Calcd. for C23H26ClNO2:
C, 71.96; H, 6.83; N, 3.65; Found: C, 72.12; H, 6.89; N, 3.54.
9-(3-Chlorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahy-
dro-(2H,5H)-acridine-1,8-dione (4e). White solid; IR (KBr):
3,3,6,6-Tetramethyl-9-(4-methylphenyl)-3,4,6,7,9,10-hexa-
hydro-(2H,5H)-acridine-1,8-dione (4b). Colourless solid; IR
(KBr): 3276, 2952, 1630, 1610 cmꢁ1 1H NMR (300 MHz,
;
CDCl3): d ¼ 11.76 (s, 1H, NH), 7.08–7.28 (m, 4H, Ar-H),
5.11 (s, 1H, CH), 2.21–2.41 (m, 8H, CH2), 2.18 (s, 3H, CH3),
1.06 (s, 6H, CH3), 0.96 (s, 6H, CH3); 13C NMR (75 MHz,
3288, 2955, 1642, 1627, 1605 cmꢁ1 1H NMR (300 MHz,
;
Scheme 2. Proposed mechanism for the formation of 4.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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72
S. K. Singh and K. N. Singh
Vol 48
CDCl3): d ¼ 11.89 (s, 1H, NH), 6.95–7.22 (m, 4H, Ar-H),
5.48 (s, 1H, CH), 2.28–2.50 (m, 8H, CH2), 1.23 (s, 6H, CH3),
1.10 (s, 6H, CH3); 13C NMR (75 MHz, CDCl3): d ¼ 190.6,
189.4, 140.4, 134.1, 129.3, 127.1, 126.0, 124.9, 115.0, 47.0,
46.4, 32.6, 31.9, 29.5, 27.3; Anal. Calcd. for C23H26ClNO2: C,
71.96; H, 6.83; N, 3.65; Found: C, 71.85; H, 6.91; N, 3.76.
9-(4-Bromophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahy-
dro-(2H,5H)-acridine-1,8-dione (4f). Yellow solid; IR (KBr):
9-(4-Dimethylaminophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,
10-hexahydro-(2H,5H)-acridine-1,8-dione (4l). Light Yel-
1
low solid; IR (KBr): 3283, 2957, 1696, 1605 cmꢁ1; H NMR
(300 MHz, CDCl3): d ¼ 11.93 (s, 1H, NH), 6.57–7.19 (m, 4H,
Ar-H), 5.47 (s, 1H, CH), 2.84–3.09 (m, 8H, CH2), 2.32 (s, 6H,
NCH3), 1.09 (s, 6H, CH3), 0.99 (s, 6H, CH3); 13C NMR (75
MHz, CDCl3): d ¼ 190.2, 189.3, 148.7, 147.7, 135.3, 128.6,
127.4, 125.5, 115.9, 113.8, 112.4, 50.8, 46.4, 40.7, 32.5, 31.8,
31.3, 29.7, 29.5, 27.3; Anal. Calcd. for C25H32N2O2: C, 76.49;
H, 8.22; N, 7.14; Found: C, 76.62; H, 8.14; N, 7.07.
1
3276, 2958, 1656, 1607 cmꢁ1; H NMR (300 MHz, CDCl3): d
¼ 11.88 (s, 1H, NH), 7.01–7.26 (m, 4H, Ar-H), 5.47 (s, 1H,
CH), 2.29–2.51 (m, 8H, CH2), 1.22 (s, 6H, CH3), 1.10 (s, 6H,
CH3); 13C NMR (75 MHz, CDCl3): d ¼ 188.3, 185.5, 137.7,
132.6, 129.1, 128.7, 116.3, 47.7, 45.8, 33.2, 31.6, 29.5, 27.1;
Anal. Calcd. for C23H26BrNO2: C, 64.49; H, 6.12; N, 3.27;
Found: C, 64.51; H, 6.18; N, 3.16.
Acknowledgments. The authors thank the Department of Bio-
technology, New Delhi for financial assistance.
9-(3-Bromophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahy-
dro-(2H,5H)-acridine-1,8-dione (4g). Colourless solid; IR
REFERENCES AND NOTES
(KBr): 3273, 2956, 1654, 1605 cmꢁ1 1H NMR (300 MHz,
;
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CDCl3): d ¼ 11.89 (s, 1H, NH), 6.99–6.31 (m, 4H, Ar-H),
5.48 (s, 1H, CH), 2.28–2.50 (m, 8H, CH2), 1.23 (s, 6H, CH3),
1.10 (s, 6H, CH3); 13C NMR (75 MHz, CDCl3): d ¼ 190.6,
189.6, 140.6, 134.3, 129.5, 128.1, 126.6, 124.2, 115.5, 47.6,
46.5, 32.4, 31.6, 29.4, 26.8; Anal. Calcd. for C23H26BrNO2: C,
64.49; H, 6.12; N, 3.27; Found: C, 64.38; H, 6.17; N, 3.30.
9-(4-Fluorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahy-
dro-(2H,5H)-acridine-1,8-dione (4h). Colourless solid; IR
(KBr): 3285, 2961, 1692, 1610 cmꢁ1 1H NMR (300 MHz,
;
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CDCl3): d ¼ 11.88 (s, 1H, NH), 6.92–7.06 (m, 4H, Ar-H),
5.48 (s, 1H, CH), 2.28–2.49 (m, 8H, CH2), 1.22(s, 6H, CH3),
1.10 (s, 6H, CH3); 13C NMR (75 MHz, CDCl3): d ¼ 190.5,
189.6, 136.5, 131.7, 129.4, 127.7, 115.6, 47.3, 46.8, 32.6, 31.3,
29.5, 27.3; Anal. Calcd. for C23H26FNO2: C, 75.18; H, 7.13;
N, 3.81; Found: C, 75.08; H, 7.21; N, 3.76.
3,3,6,6-Tetramethyl-9-(4-nitrophenyl)-3,4,6,7,9,10-hexahy-
dro-(2H,5H)-acridine-1,8-dione (4i). Colourless solid; IR
(KBr): 3289, 2961, 1678, 1607 cmꢁ1 1H NMR (300 MHz,
;
CDCl3): d ¼ 11.79 (s, 1H, NH), 8.13 (d, J ¼ 8.7 Hz, 2H, Ar-
H), 7.24 (d, J ¼ 8.7 Hz, 2H, Ar-H), 5.54 (s, 1H, CH), 2.30–
2.53 (m, 8H, CH2), 1.24 (s, 6H, CH3), 1.12 (s, 6H, CH3); 13C
NMR (75 MHz, CDCl3): d ¼ 190.9, 189.5, 146.5, 146.0,
127.6, 123.4, 114.8, 46.9, 46.3, 33.2, 31.4, 29.4, 27.4; Anal.
Calcd. for C23H26N2O4: C, 70.03; H, 6.64; N, 7.10; Found: C,
78.99; H, 6.71; N, 7.18.
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3,3,6,6-Tetramethyl-9-(3-nitrophenyl)-3,4,6,7,9,10-hexahy-
dro-(2H,5H)-acridine-1,8-dione (4j). Colourless solid; IR
(KBr): 3281, 2962, 1694, 1610 cmꢁ1 1H NMR (300 MHz,
;
CDCl3): d ¼ 11.79 (s, 1H, NH), 8.00–8.05 (m, 2H, Ar-H), 7.41–
7.47 (m, 2H, Ar-H), 5.54 (s, 1H, CH), 2.30–2.54 (m, 8H, CH2),
1.28 (s, 6H, CH3), 1.12 (s, 6H, CH3); 13C NMR (75 MHz, CDCl3):
d ¼ 190.6, 189.4, 140.4, 134.1, 129.3, 127.1, 126.0, 124.9, 115.0,
47.0, 46.4, 32.6, 31.4, 29.5, 27.3; Anal. Calcd. for C23H26N2O4: C,
70.03; H, 6.64; N, 7.10; Found: C, 70.16; H, 6.54; N, 7.21.
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10-hexahydro-(2H,5H)-acridine-1,8-dione (4k). Yellow solid;
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1
IR (KBr): 3397, 3287, 2941, 1688, 1601 cmꢁ1; H NMR (300
MHz, CDCl3): d ¼ 11.97 (s, 1H, NH), 6.57–6.82 (m, 3H, Ar-
H), 5.54 (s, 2H, CH, and OH), 3.77 (s, 3H, OCH3) 2.36–2.40
(m, 8H, CH2), 1.23 (s, 6H, CH3), 1.11 (s, 6H, CH3); 13C NMR
(75 MHz, CDCl3): d ¼ 190.3, 189.3, 146.3, 143.5, 129.5,
119.3, 115.7, 114.0, 109.7, 55.5, 46.9, 46.3, 32.2, 31.1, 29.8,
26.9; Anal. Calcd. for C24H29NO4: C, 72.89; H, 7.39; N, 3.54;
Found: C, 73.01; H, 7.32; N, 3.48.
[10] (a) Shanmugasundaram, P.; Prabahar, K. J.; Ramakrishnan,
V. T.
J Heterocycl Chem 1993, 30, 1003; (b) Srividya, N.;
Ramamurthy, P.; Shanmugasundaram, P.; Ramakrishnan, V. T. J Org
Chem 1996, 61, 5083; (c) Murugan, P.; Shanmugasundaram, P.;
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet