Synthesis of new bis-iminocoumarins by Schmidt reaction catalyzed by ion-exchange resins

Article abstract of DOI:10.1081/SCC-120020190

A new synthetic route to bis-iminocoumarins is proposed which involves the synthesis of iminocoumarins from reaction of 2-hydroxybenzaldehydes with arylacetonitriles and their coupling with aromatic diamines. Ion-exchange resins were used as catalysts in

Full text of DOI:10.1081/SCC-120020190

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Synthesis of New bis-Iminocoumarins by Schmidt
Reaction Catalyzed by Ion-Exchange Resins
a
a
b
a
Houcine Ammar , Mehdi Fakhfakh , Yves Le Bigot & Rachid El Gharbi
a
Laboratoire de Chimie Appliquée: Hétérocycles, Corps Gras et Polymères, Faculté des
Sciences de Sfax, Sfax, Tunisia
b
Laboratoire de Catalyse, Chimie Fine et Polymères, ENSIACET, Toulouse, France
Published online: 17 Aug 2006.
To cite this article: Houcine Ammar , Mehdi Fakhfakh , Yves Le Bigot & Rachid El Gharbi (2003) Synthesis of New bis-
Iminocoumarins by Schmidt Reaction Catalyzed by Ion-Exchange Resins, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 33:11, 1821-1828, DOI: 10.1081/SCC-120020190
To link to this article: http://dx.doi.org/10.1081/SCC-120020190
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Õ
SYNTHETIC COMMUNICATIONS
Vol. 33, No. 11, pp. 1821–1828, 2003
Synthesis of New bis-Iminocoumarins by Schmidt
Reaction Catalyzed by Ion-Exchange Resins
1
1
Houcine Ammar, Mehdi Fakhfakh, Yves Le Bigot,
2
1
,
and Rachid El Gharbi *
1
LaboratoiredeChimieApplique
Corps Gras et Polymeres, Faculte
Sfax, Tunisia
Laboratoire de Catalyse, Chimie Fine et Polyme
´
e : H
et erocycles,
´ ´
`
´
des Sciences de Sfax,
2
`
res,
ENSIACET, Toulouse, France
ABSTRACT
A new synthetic route to bis-iminocoumarins is proposed which
involves the synthesis of iminocoumarins from reaction of 2-hydroxy-
benzaldehydes with arylacetonitriles and their coupling with aromatic
diamines. Ion-exchange resins were used as catalysts in both steps of
this synthesis. The reaction parameters were varied and obtained
ꢀ
using Amberlyst 15 resin in cyclohexane at 80 C.
*
Correspondence: Rachid El Gharbi, Laboratoire de Chimie Applique
Heterocycles, Corps Gras et Polymeres, Faculte des Sciences de Sfax, Sfax 3038,
Tunisia; E-mail: houcineammar@lycos.com.
´
e:
´
´
`
´
1
821
DOI: 10.1081/SCC-120020190
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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1
822
Ammar et al.
Key Words: bis-Iminocoumarins; Iminocoumarins; Diamine.
Thesynth sei s of coumarin and iminocoumarin compounds has
[
1]
attracted much interest of their photophysical properties and their
[2,3]
biological activity.
In contrast to the extensive work reported on
large number of coumarins, the work on the iminocoumarins and their
derivatives is scanty, probably because of their high sensitivity of the
hydrolyze when used homogenous catalysts. The use of ion-exchange
resins as catalysts is not only for interest from their advantage to prevent
this undesirable hydrolysis reaction, but offers considerable synthetic
advantages in terms of yield, selectivity, and simplicity of the reaction
procedure. Recently we reported the synthesis of several coumarin
compounds obtained by Knoevenagel reaction catalyzed by IRA 900 resin
[
4–6]
in good yield and high selectivity.
based on the use of ion-exchange resins as catalysts led us to examine
thepossibility of pr pe aring bis-iminocoumarins. To theb se t of our
Thepursuit of this inv es tigation
knowledge, this family of coumarin derivatives has been the subject of
only one report which described the spectroscopic and laser properties
of some bifluorophoric molecules obtained by linking coumarin and
[
7]
iminocoumarin moieties with thiazolyl cycle as a bridge. However,
the mechanism of the reaction, the process, and the detail structures of
the products were not tackled in this work.
In this report we describe a novel and versatile method for synthesis
of new bifluorophoric molecules incorporating two iminocoumarin
nuclei. This method involved the synthesis of several iminocoumarins
[8]
by Knoevenagel reaction and their coupling with aromatic diamines
by Schmidt reaction.
RESULTS AND DISCUSSION
0
0
The global reaction scheme leading to N,N -arylene bis(3,3 -arylimi-
nocoumarins) 6–20 is shown in Sch. 1.
The reaction of aldehydes 1–4 with arylacetonitrile a–c in presence
of basic resin Amberlite IRA 900 afford corresponding 3-aryliminocou-
marins in good yield (Table 1). Their structures were assigned by IR,
1
13
H NMR, and C NMR spectra.
In our approach to study thesynth es is of bis-iminocoumarins 6–20
using Schmidt reaction in heterogeneous medium, we first concentrated on
a model system 1a/5a in order to evaluate the best synthetic conditions

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Synthesis of bis-Iminocoumarins
1823
Scheme 1.
Table 1. Synthesized of the substituted iminocoumarins 1a–3a, 1b, 1c, and 4c.
a
Yield (%)
R1
R2
R3
R4
Time(h)
1a
2a
3a
1b
1c
4c
H
H
H
H
H
H
H
H
H
Cl
H
H
82
50
8
10
36
4
OMeH
H
OMe
H
25
H
H
H
H
72
69
61
H
OMeH
8
8
a
Isolated yield.

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1
824
Ammar et al.
and then extended the study to other iminocoumarins and different
diamines. Four parameters were varied in this context, namely the
reaction temperature, the nature of the organic solvent, the nature of
thecatalyst, and its hydratation state.
The best yield of the desired compound 6 was obtained when
ꢀ
Amberlyst 15 resin was utilized as a catalyst in cyclohexane at 80 C.
Different experiments carried out with various hydratation states of the
exchange resin led to a considerable variation in both yield and selectivity.
In the present context we found that the best conditions for the formation
of bis-iminocoumarins 6 required the use of Amberlyst 15 resin with
50 mg water/g of dry resin. The increase of resin hydratation state led
to a decrease in yield of 6 and favorized the transformation of 1a to
corresponding coumarin by hydrolysis reaction. Following this successful
synthesis several substituted bis-iminocoumarins were prepared (Table 2).
0
0
Table 2. Synthesized of the N,N -arylene bis(3,3 -aryliminocoumarins) 6–20.
a
Yield (%)
R
1
R
2
R
3
R
4
Time(h)
6
7
8
9
1
þa
þ
5a
5a
5a
5a
5a b
5b
5b
5b b
5a c
5c
5b c
5ca
5cb
5b
5c
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Cl
H
H
70
68
1
0.5
2a
3a
1
þ
OMeH
H
OMe
70
45
2
þb
H
H
Cl
H
57
36
42
2
2
3
1
1
1
1
1
1
1
1
1
1
2
0
1þ
þ
H
H
H
1
2a
H
OMeH
2
3
4
5
6
3þa
1þ
1þ
2þa
1þ
1þ
1þ
4þc
þ
OMe
4
H
H
H
Cl
H
H
H
H
H
H
H
H
H
38
29
38
31
75
75
43
55
3
H
2
H
3
H
4
7
8
9
H
0.5
2
H
OMeH
H
H
4
0
1c
H
H
2
a
Isolated yield.

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Synthesis of bis-Iminocoumarins
CONCLUSION
1825
New heterocyclic compounds containing two iminocoumarin nuclei
have been synthesized and characterized. The process developed in this
investigation is particularly interesting for its simplicity and for the
advantageof providing this family of coumarin compounds in good
yield and high selectivity.
Experimental Section
Aldehydes 1–4, nitriles a–c, and diamines 5a–5c arecomm re cial
products. Solvents (toluene and cyclohexane) were purified by standard
techniques and redistilled prior to their use. Catalysts (IRA 900, A 15)
were conditioned then used. Melting points were taken using a
Electrothermal 9100 apparatus. IR spectra were obtained on a Jasco
1
FT-IR 420 spectrophotometer apparatus (in KBr pellets). H and
1
3
C NMR spectra were recorded with a Bruker WP 200 spectrometer at
00.0 MHz and 50.32 MHz respectively, in CDCl or DMSO-d , with
2
TMS as internal standard (chemical shifts in ppm).
3
6
General Procedure for the Synthesis of 3-Aryliminocoumarins
a–3a, 1b, 1c, and 4c
1
A mixture of aldehydes 1–4 (30 mmol), IRA 900 resin (3 g, 30 mmol
OH ), and cyclohexane (25 mL) are introduced in a 250 mL three-neck
À
ꢀ
flask equipped with a condenser and stirred for 3 h at 80 C under a
nitrogen atmosphere. After that, the arylacetonitriles a–c (30 mmol)
were added and the mixture was refluxed for an appropriate time
(
Table 1). After completion of the reaction, the mixture was separated
from the solid catalyst and the organic phase was concentrated under
reduced pressure. The solid phase was purified by crystallizing with the
hexane to give 3-aryliminocoumarins as a colorless solid.
À1
3
-Phenyliminocoumarin (1a): IR (KBr) [cm ]: ꢀ ¼ 3275, 3050, 1644,
1
1
594, 1063. H NMR (CDCl ) [ppm]: ꢁ ¼ 7.02–815 (m, 11H, Ar ).
3
1
1
3
C NMR (CDCl ) [ppm]: ꢁ ¼ 116.1, 119.3, 121.0, 123.6, 125.8, 127.9,
3
ꢀ
1
28.2, 128.9, 129.2, 129.4, 132.4, 138.6, 156.9. M.p. [ C] ¼ 105.
À1
6
-Chloro,3-phenyliminocoumarin (2a):IR (KBr) [cm ]:ꢀ ¼ 3272, 3041,
1
1
7
1
644, 1590, 1052. H NMR (CDCl ) [ppm]: ꢁ ¼ 7.02–7.62 (m, 8H, Ar ),
3
1
1
3
.82 (s, 1H, H4). C NMR (CDCl ) [ppm]: ꢁ ¼ 116.4, 117.0, 117.3, 126.6,
3
ꢀ
28.3, 128.6, 129.2, 129.9, 130.6, 131.4, 132.1, 136.0, 152.0. M.p. [ C] ¼ 128.

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826
Ammar et al.
À1
5
,7-Dimethoxy,3-phenyliminocoumarin(3a):IR(KBr)[cm ]:ꢀ ¼ 3276,
1
3
057, 1648, 1611, 1065. H NMR (CDCl ) [ppm]: ꢁ ¼ 3.80, 3.82 (2s, 6H,
3
R –R ), 6.15 (d, 1H, H6), 6.29 (d, 1H, H8), 7.43 (s, 1H, H4), 7.33–7.54
2 4
1
3
(
1
m, 5H, Ar1). C NMR (CDCl ) [ppm]: ꢁ ¼ 55.6, 55.7, 92.4, 93.7, 103.0,
3
ꢀ
25.0, 128.1, 128.4, 128.6, 136.9, 154.0, 156.7, 162.5. M.p. [ C] ¼ 150.
À1
3
-p-Chlorophenyliminocoumarin (1b): IR (KBr) [cm ]: ꢀ ¼ 3282, 3069,
1
1
7
ꢁ
649, 1596, 1067. H NMR (CDCl ) [ppm]: ꢁ ¼ 7.06–7.16 (m, 4H, Ar ),
3
1
1
.36 (s, 1H, H4), 7.30–7.61 (m, 4H, Ar). C NMR (CDCl ) [ppm]:
3
3
¼ 114.9, 115.9, 123.3, 127.3, 128.2, 129.9, 130.3, 133.5, 134.0, 135.0,
ꢀ
1
53.0, 156.1. M.p. [ C] ¼ 106.
À1
3
-(2-Thiophenyl)iminocoumarin (1c): IR (KBr) [cm ]: ꢀ ¼ 3276, 3099,
1
1
7
649, 1594, 1027. H NMR (CDCl ) [ppm]: ꢁ ¼ 7.04–7.12 (m, 2H, H6–H7),
3
.28 (2dd, 2H, H5–H8), 7.41 (s, 1H, H4), 7.10, 7.36, 7.66 (m, 3H, Ar) .
2
1
3
C NMR (CDCl ) [ppm]: ꢁ ¼ 115.3, 119.8, 123.7, 127.0, 127.2, 127.5,
3
ꢀ
1
27.6, 130.4, 130.9, 137.3, 152.6. M.p. [ C] ¼ 80.
À1
7
-Methoxy-3-(2-thiophenyl)iminocoumarin (4c): IR (KBr) [cm ]:
1
ꢀ
(
(
¼ 3295, 3086, 1658, 1606, 1021. H NMR (CDCl ) [ppm]: ꢁ ¼ 3.83
3
s, 3H, R ), 6.68 (dd, 1H, H6), 7.07 (d, 1H, H8), 7.24 (d, 1H, H5), 7.40
2
1
s, 1H, H4), 6.64, 7.34, 7.59 (m, 3H, Ar2). C NMR (CDCl ) [ppm]:
3
3
ꢁ
1
¼ 56.1, 94.0, 100.7, 111.3, 114.0, 126.8, 127.1, 127.5, 128.8, 132.0, 138.0,
ꢀ
56.0. M.p. [ C] ¼ 90.
0
0
Table 3. Selected spectroscopic data for N,N -arylene bis(3,3 -arylimino-
coumarins) 6–20.
1
a
H NMR/ꢁ in ppm (CDCl ) or (DMSO-d )
3
6
M.p.
ꢀ
À1
(
C)
IR/ꢀ in cm
MeO
CH2
H4
Ar –Ar
1 2
a
a
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
>300
240
260
1637, 1593
1632, 1593
1634, 1588
1627, 1585
1645, 1595
1644, 1592
1644, 1591
1643, 1595
1645, 1599
1641, 1594
1643, 1599
1644, 1591
1646, 1595
1652, 1599
1645, 1606
7.21–7.99
7.23–7.43
6.36–7.78
7.05–7.75
7.16–7.35
7.15–7.48
7.15–7.76
7.14–7.91
7.12–7.87
7.02–7.48
6.99–7.80
7.12–7.82
7.09–7.74
6.58–7.69
7.38–7.76
7.17
7.55
3.78–3.85
>300
219
182
1
1
1
1
1
1
1
1
1
1
2
4.02
3.99
3.96
4.01
7.67
7.17
7.56
248
3.78–3.85
a
a
>300
>300
185
7.67
7.16
200
260
7.67
7.60
7.55
7.63
200
165
4.01
4.02
3.84
204

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Synthesis of bis-Iminocoumarins
1827
0
General Procedure for the Synthesis of N,N -Arylene
0
bis(3,3 -Aryliminocoumarins) 6–20
þ
To a stirred mixture of A 15 resin (3 g, 30 mmol H ) and cyclo-
hexane or toluene (25 mL) in 250 mL three-neck flask equipped with a
condenser were added the 3-aryliminocoumarins (30 mmol). The mix-
ture was refluxed for 3 h under a nitrogen atmosphere. Then diamines
5a–5c (15 mmol) were added and the mixture was refluxed for an
appropriate time (Table 3). The separated organic layer was evapo-
rated from solvent and purified by crystallizing with the appropriate
0
0
solvent to give N,N -arylene bis(3,3 -aryliminocoumarins) 6–20 as a
colorless solids.
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Received in the Netherlands July 20, 2002