Cu(II) schiff base as catalyst in the synthesis of 1,8- dioxodecahydroacridine

Article abstract of DOI:10.2174/1386207311316010002

The catalytic property of Cu(II) Schiff-base complex in an efficient synthesis of 1,8-dioxodecahydroacridines was investigated. The one-pot three component reaction of dimedone, aromatic aldehydes and aromatic amines or ammonium acetate in water afforded

Full text of DOI:10.2174/1386207311316010002

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Combinatorial Chemistry & High Throughput Screening, 2013, 16, 2-6
Cu(II) Schiff Base as Catalyst in the Synthesis of 1,8-Dioxodecahydroacridine
Seyed Mohammad Vahdat*,1, Hamid Reza Mardani2, Hamid Golchoubian3, Maryam Khavarpour4,
Saeed Baghery5 and Ziba Roshankouhi5
1Department of Chemistry, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran
2Department of Chemistry, PayameNoor University, Tehran, Iran
3Department of Chemistry, University of Mazandaran, Babolsar, Iran
4Department of Chemical Engineering, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran
5Young Researchers Club, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran
Abstract: The catalytic property of Cu(II) Schiff-base complex in an efficient synthesis of 1,8-dioxodecahydroacridines
was investigated. The one-pot three component reaction of dimedone, aromatic aldehydes and aromatic amines or
ammonium acetate in water afforded the corresponding 1,8-dioxodecahydroacridines with excellent yields. This reaction
was carried out in the presence of 1 mol% of catalysts at room temperature. The reusability of the catalysts was
demonstrated by a five-run test without loss of its activity. Also, this catalyst possesses several advantages including mild
reaction conditions, lower catalytic loading, shorter reaction times, high yield of the products, inexpensive and cleaner
(Green chemistry) reactions.
R1
O
CHO
O
O
cat-i (1 mol%)
R2NH2 or NH4OAc
+
+
H2O, r.t., 5-20 min
O
R1
N
Ph
N
R3
R3= H, Aryl
O
N
Cu
O
Cu(II) Schiff-base catalyst (i)
Ph
Keywords: 1,8-Dioxodecahydroacridine, Cu(II) Schiff-base catalyst, multi component reaction, one-pot synthesis, water
solvent.
INTRODUCTION
Extensive studies have been carried out to synthesize
acridine and its derivatives utilizing different catalytic
agents, such as: glycerol [14], BF3.Et2O [15], Ceric
ammonium nitrate [16] and Amberlyst-15 [1]. In previous
work, we also reported the synthesis of acridine and its
derivatives utilizing ionic-liquids as acid catalyst [17, 18].
Acridine and its derivatives are interesting compounds,
because of their well-known properties in fields of medicinal
[1, 62] and biological activities (such as antibacterial [3],
antimalarial [4], anticancer [5], antitumor [6], analgesic [7],
anticonvulsant [8], hypertensive and anti-inflammatory [9]),
applications in material science (semiconductors) [10] and
spectroscopy (luminescent agent) [11]. Therefore, their
syntheses have been attracted by a large number of organic
chemists [12, 13]. The preparation of acridine and its
derivatives is a three component reaction that is an important
class in organic reaction. The dimedone, aldehyde and
primary amine or ammonium acetate are the components of
this reaction (Scheme 1).
Whilst the syntheses of organic compounds catalyzed by
several transition metal complexes have been reported,
reactions catalyzed by Schiff-base metal complexes have
received less attention. The salen-type ligand is one of well-
known Schiff-base ligand that its metal complexes have
widely been employed widely as catalyst of more organic
reactions [19, 20], fluorescent sensor [21], photo degradation
of organic dyes [22], antimicrobial activities [23], it is also
used in DNA cleavage [24] and many other catalytic
purposes. Schiff-base metal complexes are also considered
as ideal “green” catalysts due to their low toxicities. Easy
preparations and inexpensive starting materials are other
*Address correspondence to this author at the Department of Chemistry,
Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran;
Fax:(+98)-121-2517087;
E-mails: m.vahdat@iauamol.ac.ir, vahdat_mohammad@yahoo.com
1875-5402/13 $58.00+.00
© 2013 Bentham Science Publishers

Synthesis of 1,8-Dioxodecahydroacridines
Combinatorial Chemistry & High Throughput Screening, 2013, Vol. 16, No. 1 3
R1
O
CHO
O
O
cat-i (1 mol%)
R2NH2 or NH4OAc
+
+
H2O, r.t., 5-20 min
O
R1
3
N
1
2
Ph
4
R3
R3= H, Aryl
N
O
Cu
O
Cu(II) Schiff-base catalyst (i)
N
Ph
Scheme 1. Synthesis of 1,8-dioxodecahydroacridines in the presence of Cu(II) Schiff-base catalyst (i).
advantage of Schiff-base metal complexes. In this work, we
report an efficient, high yield and rapid method for synthesis
of acridine and derivatives by new reusable Cu(II) Schiff-
base catalyst (i) [25].
stretching), 1345, 1551 (NO2 stretching), 1375, 1575 (C=C–
stretching of aromatic ring), 1671 (C=O– of 1,3-diketone),
2945 (–CH stretching of aliphatic), 3055 (–CH stretching of
1
aromatic ring); H NMR spectrum (400 MHz, CDCl3, ꢁ,
ppm): 1.63 (s, 6H, 2 * CH3), 1.81 (s, 6H, 2 * CH3), 2.51 (dd,
4H, J= 16.2 Hz, 2 * CH2), 2.71 (dd, 4H, J= 16.3 Hz, 2 *
CH2), 5.07 (s, 1H, CH), 7.21-7.34 (m, 5H, ArH), 7.51 (d, 2H,
J= 9.5 Hz, ArH), 7.63 (d, J= 9.3 Hz, 2H, ArH).
A three-component condensation of dimedone 1 (2
mmol), 4-chlorobenzaldehyde 2 (1 mmol) and p-toluidine 3
(1 mmol) was employed to optimize the reaction conditions
with respect to temperature, reaction time, solvent, molar
ratio of catalyst to the substrate and the reusability of the
catalyst. The reaction was carried out under aqueous
conditions at room temperature and it was found that 1 mol%
of Cu(II) Schiff-base catalyst was sufficient to obtain the
desired 1,8-dioxodecahydroacridines in 97% yield within 7
min (Scheme 1).
9-(2-chlorophenyl)-10-(4-chlorophenyl)-3,3,6,6-tetram-
ethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione (Table
3, entry 24): Yield: 95%; M.p 319-321 °C; IR spectrum
(KBr, ꢀ, cm-1): 978 (–CH out of bending of aromatic ring),
1237 (CN stretching), 1365, 1570 (C=C– stretching of
aromatic ring), 1675 (C=O– of 1,3-diketone), 2957 (–CH
stretching of aliphatic), 3057 (–CH stretching of aromatic
1
ring); H NMR spectrum (400 MHz, CDCl3, ꢁ, ppm): 1.71
EXPERIMENTAL
(s, 6H, 2 * CH3), 1.79 (s, 6H, 2 * CH3), 2.33 (dd, 4H, J= 16.1
Hz, 2 * CH2), 2.40 (dd, 4H, J= 16.4 Hz, 2 * CH2), 5.24 (s,
1H, CH), 7.31 (d, 2H, J= 9.3 Hz, ArH), 7.35 (d, 1H, J= 7.8
Hz, ArH), 7.38-7.43 (m, 2H, ArH), 7.47 (d, 2H, J= 9.2 Hz,
ArH), 7.51 (d, 1H, J= 7.7 Hz, ArH).
Materials and Methods: NMR spectra were determined
on
a Fourier-transform (FT)- NMR Bruker AV-400
spectrometer in DMSO-d6 and CDCl3 are expressed in ꢀ
values relative to tetramethylsilane; coupling constants (J)
are measured in Hz. Melting points were determined on a
ELECTR THERMAL9100. Infrared spectra were recorded
on a RAYLEIGH WQF-510 Fourier transform instrument.
Commercially available reagents were used throughout
without further purification.
9,10-bis(4-chlorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,
10-hexahydroacridine-(2H,5H)-dione (Table 3, entry 25):
Yield: 96%; M.p 305-307 °C; IR spectrum (KBr, ꢀ, cm-1):
778 (–CH out of bending of aromatic ring), 1225 (CN
stretching), 1367, 1545 (C=C– stretching of aromatic ring),
1671 (C=O– of 1,3-diketone), 2953 (–CH stretching of
aliphatic), 3065 (–CH stretching of aromatic ring); 1H NMR
spectrum (400 MHz, CDCl3, ꢁ, ppm): 1.71 (s, 6H, 2 * CH3),
1.76 (s, 6H, 2 * CH3), 2.35 (dd, 4H, J= 16.1 Hz, 2 * CH2),
2.43 (dd, 4H, J= 16.3 Hz, 2 * CH2), 5.31 (s, 1H, CH), 7.21
(d, 2H, J= 9.4 Hz, ArH), 7.32 (d, 2H, J= 9.4 Hz, ArH), 7.47
(d, 2H, J= 9.3 Hz, ArH), 7.52 (d, 2H, J= 9.1 Hz, ArH).
General procedure for the synthesis of 1,8-dioxodeca-
hydroacridine derivatives: A mixture of dimedone (2.0
mmol), aromatic aldehyde (1.0 mmol), aromatic amine or
ammonium acetate (1.0 mmol) and Cu(II) Schiff-base
catalyst (1 mol%) in water (2 mL) was stirred at room
temperature for an appropriate time (5-20 min). The progress
of the reaction was monitored by TLC (n-hexan/ethyl acetate
4:1). After completion of the reaction, the resulting solid
crude product was filtered and then recrystallized from
ethanol–water to obtain pure product. The physical data
(M.p, IR, NMR) of these known compounds were found to
be identical with those reported in the literature.
RESULTS AND DISCUSSION
To investigate the solvent effect the Cu(II) Schiff-base
catalyst (i) was tested as a model reaction between
dimedone, p-toluidine and 4-chlorobenzaldehyde in different
reaction media. The results are gathered in Table 1. The
obtained results show that the reaction operates better in
polar solvents than non-polar ones. Among the polar
3,3,6,6-tetramethyl-9-(4-nitrophenyl)-10-phenyl-3,4,6,7,
9,10-hexahydroacridine-(2H,5H)-dione (Table 3, entry
12): Yield: 98%; M.p 257-259 °C; IR spectrum (KBr, ꢀ, cm-1):
785 (–CH out of bending of aromatic ring), 1235 (CN

4
Combinatorial Chemistry & High Throughput Screening, 2013, Vol. 16, No. 1
Vahdat et al.
Table 1. Solvent Effect on the Reaction Between Dimedone, p-Toluidine and 4-Chlorobenzaldehyde
Solvent
H2O
C2H5OH
CH3CN
THF
Toluene
Time (min)
Yield (%)
7
7
10
92
15
89
19
85
97
96
Reaction condition: a 4-chlorobenzaldehyde (1 mmol), dimedone (2 mmol) p-toluidine (1 mmol), Cu(II) Schiff-base catalyst (1 mol %), solvent (2 mL); b Isolated yield.
solvents examined, water was found to be the most effective
solvent. Remarkably, the condensation reaction preceded
smoothly both in water and ethanol conditions to afford
desired product in good yields. This result confirms that the
Cu(II) Schiff-base catalyst (i) is not only a water-stable
catalyst but also demonstrates high catalytic activity.
According to the results, the catalyst amounts for the most
systems are greater than 1 mol% which requires longer
reaction times and lower yields than this catalytic system.
To study the generality of this process, the reaction was
carried out with a variety of aldehyde derivatives and
aromatic amines to synthesize the corresponding
polyfunctionalized -dioxo-9,10-aryl-decahydroacridines. The
results are summarized in Table 3. In this way, a series of
aromatic aldehydes and amines underwent electrophilic
substitution reaction with dimedone to afford a wide range of
To underline the merit of this method, the one-pot
synthesis of 1,8-dioxodecahydroacridines using Cu(II)
Schiff-base catalyst (i) was faster and gave higher yields
than those catalysts reported in the literature (Table 2).
Table 2. Reaction Between Dimedone, 4-Chlorobenzaldehyde and p-Toluidine in Presence of Different Catalysts
Entry
Catalyst
Catalyst (mol%)
Time (min)
Yield (%)
Ref.
1
2
3
4
5
6
7
8
Cu(II) Schiff-base
C11H15COOH
PTSA
1
10
2
7
97
26.8
18
This work
[26a]
[12]
360
360
360
300
360
360
360
Sc(DS)3
10
0.1 gr
2
78.3
84
[26a]
[26b]
[12]
[HMIM]TFA
C7H15COOH
TsOH
31
10
2
13.2
41
[26a]
[12]
DBSA
Table 3. Synthesis of 1,8-Dioxodecahydroacridine Derivatives in the Presence of Cu(II) Schiff-Base Catalyst
Entry
R1
R2
Mp (oC)
Time (min)
Yield (%) [Ref.]
1
2
4-H
4-Cl
NH4OAc
NH4OAc
281-283
295-297
303-305
269-271
320-322
285-287
315-317
255-257
245-247
217-219
295-297
257-259
263-265
287-289
273-275
347-349
281-283
295-297
283-285
217-219
251-253
208-210
238-240
319-321
305-307
20
14
17
15
17
14
11
13
10
10
8
93 [2]
95 [2]
3
4-OH
4-OMe
4-Me
3-NO2
4-NO2
4-H
NH4OAc
93 [2]
4
NH4OAc
93 [27a]
95 [27b]
96 [2]
5
NH4OAc
6
NH4OAc
7
NH4OAc
98 [27c]
94 [26b]
95 [27d]
95 [26b]
97 [16]
98
8
Aniline
9
4-Cl
Aniline
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
4-OMe
3-NO2
4-NO2
4-H
Aniline
Aniline
Aniline
7
p-toluidine
p-toluidine
p-toluidine
p-toluidine
p-toluidine
p-toluidine
p-toluidine
4-methoxyaniline
4-methoxyaniline
4-methoxyaniline
4-methoxyaniline
4-chloroaniline
4-chloroaniline
12
9
94 [27e]
95 [26a]
97 [27e]
93 [26a]
94 [27e]
96 [27e]
98 [27e]
95 [12]
97 [12]
95 [12]
96 [12]
95
2-Cl
4-Cl
7
4-OH
4-OMe
4-Me
3-NO2
4-H
10
10
8
5
14
9
4-Cl
4-OMe
4-Me
2-Cl
9
10
11
8
4-Cl
96

Synthesis of 1,8-Dioxodecahydroacridines
Combinatorial Chemistry & High Throughput Screening, 2013, Vol. 16, No. 1 5
Table 4. Reusability Studies of the Catalyst for Synthesis of 9-(4-Chlorophenyl)-3,3,6,6-Tetramethyl-10-p-tolyl-3,4,6,7,9,10-
Hexahydroacridine-(2H,5H)-dione (Table 4- Entry 15)
Number of Experiments
Fresh
1
2
3
4
Isolated yield (%)
97
96
95
95
93
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yields. As shown in Table 3, the electronic property of the
substituents attached on the aromatic ring has an effective
role in the conversion rate. So that, aromatic aldehydes with
electron-withdrawing groups on the aromatic ring (Table 3,
entries 6, 7, 11, 12, 18) react faster than electron-donating
groups (Table 3, entries 3, 4, 5, 10, 17, 21, 25). Furthermore,
both aromatic amines and ammonium acetate similarly
underwent well to the conversion.
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The reusability of the catalysts was checked using
dimedone, 4-chlorobenzaldehyde and p-toluidine as a model
substrate. In this regard, at the end of the reaction, ethyl
acetate was added to the reaction mixture. The aqueous layer
was then separated and used directly in the next reaction
without further purification. As shown in (Table 4), the
recovered catalyst was reused at five successive runs without
appreciable loss in its catalytic activity.
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CONCLUSION
In summary, Cu(II) Schiff-base was used as an efficient
catalyst for the synthesis of 1,8-dioxodecahydroacridines
which resulted in better yields. Cu(II) Schiff-base effective
catalysis the one-pot three-component condensation of
dimedone, aromatic aldehydes and aromatic amines or
ammonium acetate in water to produce 1,8-
dioxodecahydroacridines in excellent yields. The catalyst
offers several advantages including shorter reaction times,
high yield of the products, mild reaction conditions, lower
catalytic loading, cleaner reactions, green solid acid catalyst
as well as simple experimental and isolation procedures.
Also, the catalysts were able to be reused easily for five-run
test with a smooth decrease in the catalytic activity of the
recovered catalyst.
[13]
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CONFLICT OF INTEREST
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The authors confirm that this article content has no conflict
of interest.
ACKNOWLEDGEMENTS
The authors are thankful for the facilities provided to
carry out research in Chemistry Research Laboratory at
Ayatollah Amoli Branch, Islamic Azad University.
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Received: March 30, 2012
Revised: September 9, 2012
Accepted: September 10, 2012