Fast and efficient method for imination of n-aminorhodanine using inorganic solid support under microwave irradiation and classical heating

Article abstract of DOI:10.1155/2011/351203

Reaction of N-aminorhodanine with various aldehydes under classical heating (in various solvents, using hydrochloric acid or acetic acid as catalyst) or by using Al₂O₃ under microwave irradiation in solventless system led to the corresponding imines (2 or 3). All the compounds have been characterized by elemental analyses, NMR and IR spectroscopy. Results indicate that treatment of N-aminorhodanine with aldehydes in acetonitrile as solvent or under solventless system led to the corresponding imines (2a-2e), while reactions were performed in solvent such as methanol 3a-3e was formed as products of ring cleavage and imination.

Full text of DOI:10.1155/2011/351203

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2011, 8(2), 535-540
http://www.e-journals.net
Fast and Efficient Method for Imination of
N-Aminorhodanine Using Inorganic Solid Support
under Microwave Irradiation and Classical Heating
MASOUMEH TABATABAEE*, MAJID M. HERAVI,
MAHBOUBEH SHARIF# and FATEMEH ESFANDIYARI§
*Scientific Society of Nanotechnology
Islamic Azad University, Yazd Branch, Yazd, Iran
Department of Chemistry
School of Sciences, Alzahra University, Tehran, Iran
#Department of Chemistry
Islamic Azad University- Qom Branch, Qom, Iran
§Department of Chemistry
Islamic Azad University- Yazd Branch, Yazd, Iran
tabatabaee45m@yahoo.com
Received 16 June 2010; Revised 13 September 2010; Accepted 6 November 2010
Abstract: Reaction of N-aminorhodanine with various aldehydes under
classical heating (in various solvents, using hydrochloric acid or acetic acid as
catalyst) or by using Al2O3 under microwave irradiation in solventless system
led to the corresponding imines (2 or 3). All the compounds have been
characterized by elemental analyses, NMR and IR spectroscopy. Results
indicate that treatment of N-aminorhodanine with aldehydes in acetonitrile as
solvent or under solventless system led to the corresponding imines (2a-2e),
while reactions were performed in solvent such as methanol 3a-3e was formed
as products of ring cleavage and imination.
Keywords: Imines, Microwave irradiation, Inorganic supports.
Introduction
There is considerable interest in the chemistry of iminic compounds1-4. Compounds
containing imine bond with different donor atoms, also use in analytical applications and
metal coordination5-7. Since many compounds containing sulfur and nitrogen atoms are
antihypertensive, analgesic, antiinflammatory, sedative or fungicidal, synthesis of the
corresponding derivatives could be of interest from the viewpoint of chemical reactivity and
biological activity8.

536
M. TABATABAEE et al.
The use of microwave irradiation in organic synthesis has become increasingly popular
within the pharmaceutical and academic arenas, because it is a new technology to accelerate
the organic reaction dramatically. Microwave irradiation enhanced chemical reactions
especially under solvent-free conditions have attracted much attention9. In continuation of
our recent work on microwave-assisted reactions under solvent-free conditions for the
synthesis of some iminic compounds derived from 4-amino-6-methyl-1,2,4-triazine-3-
thione-5 (2H)-one (AMTTO) and 4-amino-5-methyl-1, 2,4-triazole-3 (4H)-thione (AMTT)8,10
.
In this communication, we wish to report our results for the synthesis of various iminic
compouds derived from N-aminorhodanine under classical heating and using Al2O3 as
inorganic support, under microwave irradiation in solventless system.
Experimental
FT-IR spectra bruker tensor 27 spectrometer (KBr pellets, nujol mulls, 4000-400 cm-1) was
1
used. H and 13CNMR were recorded on a Brucker (AX-200) 300 MH spectrometer using
TMS as an external standard. Elemental analyses were performed using a Costech ECS 4010
CHNS-O analyzer. All chemicals and solvents were purchased from Merck and Fluka and were
used without further purification or drying. Al2O3 active acidic (Merck) was used as solid support.
General procedure for the reaction of N-aminorhodanine with various aldehydes
under classical heating
A solution of N-aminorhodanine (2 mmol) in (CH3CN or CH3OH, 10 mL) was treated with
aldehydes in a molar ratio of 1:1.5 and the resulting mixture was acidified by 37% hydrochloric
acid (3 drops) or acetic acid (8 drops). The reaction mixture was refluxed for indicated
time (Table 1). The solid residue was filtered, washed with cold solvent (10 mL) to afford the
compound 2 (in CH3CN and 3 (in CH3OH).
General procedures for the reaction of N-aminorhodanine with various aldehydes
using inorganic solid supports under microwave irradiation
N-aminorhodanine (1 mmol) and aldehyde were taken in a molar ratio of 1:1.5 was mixed
with Al2O3 (1 g) in a beaker. The beaker was placed in microwave oven for appropriate
time. The reaction mixture was dissolved in acetone/THF (1:1 ratio) the solid residue was
filtered. The clear filtrate was kept to give the corresponding imine (2a-2e).
Selected physical data
3-(4-Chlorobenzylideneamino)-2-thioxothiazolodin-4-one (2a)
~
This compound was obtained as pale yellow crystalline, mp 139-141 °C; IR
υ
(KBr disc):
1
CO 1700, CN (imine) 1601(s) cm–1; H NMR (d6- DMSO): δ= 4.37 (s, 2H, CH2), 7.64
(d, 2H, Ar, J = 6.82), 7.94 (d, 2H, Ar, J = 8.81), 8.78 (s, 1H, CH=N) ppm. 13C NMR
(d6 - DMSO): δ = 35.65 (1C, CH2 (amine fragment), 130.30, 131.39, 131.57, 138.67(6C,
Ar), 169.94 (1C, C=N, imine), 170.44(C=O), 197.78 (C=S) ppm. Anal. Calcd. for
C10H7ClN2OS2 (M = 270.5): C, 44.36, H, 2.58, N, 10.38. Found: C, 44.18, H, 2.41, N, 10.26.
3-(3-Nitrobenzylideneamino)-2-thioxothiazolodin-4-one (2b)
~
Mp 283-286 °C; IR
υ
(KBr disc): CO 1729, CN(imine) 1610(s), NO2 (1523, 1345) cm–1; 1H
NMR (d6- DMSO): δ = 4.40 (s, 2H, CH2), 7.85 (t, 1H, Ar), 8.35 (d, 1H, Ar, j = 4.2), 8.45
(d, 1H, Ar, J = 4.8), 8.72 (s, 1H, Ar), 9.01 (s, 1H, CH=N) ppm, 13C NMR (d6 - DMSO):
δ = 35.65 (C, CH2 (amine fragment), 123.86, 128.04, 131.83, 134.32, 135.57, 149.15 (6C,
Ar), 168.39 (C, C=N, imine), 170.36 (C=O), 197.88 (C=S) ppm. Anal. Calcd. for
C10H7N3O3S2 (M = 281): C, 42.7, H, 2.49, N, 14.94. Found: C, 42.58, H, 2.29, N, 14.63.

Fast and Efficient Method for Imination of N-Aminorhodanine
537
3-(4-Methoxybenzylideneamino)-2-thioxothiazolodin-4-one (2c)
~
Mp 167-169 °C; IR
υ
(KBr disc): CO 1705, CN(imine) 1616(s) cm–1; 1H NMR (d6- DMSO):
δ= 3.86 (s, 3H, OCH3), 4.35 (s, 2H, CH2), 7.11 (d, 1H, Ar, J=5.4), 7.86 (d, 1H, Ar, J=5.1),
8.60 (s, 1H, CH=N) ppm, 13C NMR (d6 - DMSO): δ= 35.55 (C, CH2 (amine fragment),
56.45 (C, OCH3), 115.56, 125.17, 131.82, 164.03 (6C, Ar), 170.63 (C, C=N, imine), 171.15
(C=O), 197.69 (C=S) ppm. Anal. Calcd. for C11H10N2O2S2 (M = 266): C, 49.62, H, 3.75, N,
10.53. Found: C, 49.35, H, 3.37, N, 10.33.
3-(2-Hydroxy-3-methoxybenzylideneamino)-2-thioxothiazolodin-4-one (2d)
~
1
Mp 210-213 °C; IR
υ
(KBr disc): CO 1669, CN(imine) 1598(s) cm–1; H NMR (d6- DMSO):
δ= 3.82 (s, 3H, OCH3), 4.31 (s, 2H, CH2), 6.91 (m, 1H, Ar), 7.18 (d, 1H, Ar, J=7.5), 7.39
(d, 1H, Ar, J = 7.96), 9.15 (1H, CH=N), 10.16 (1H, OH) ppm,. Anal. Calcd. for
C11H10N2O3S2 (M = 282): C, 46.81, H, 3.55, N, 9.93. Found: C, 46.76, H, 3.48, N, 9.86.
3-(4-Hydroxybenzylideneamino)-2-thioxothiazolodin-4-one (2e)
~
1
Mp 264-265 °C; IR
υ
(KBr disc): OH 3413,CO 1697, CN(imine) 1574(s) cm–1; H NMR
(d6- DMSO): δ= 5.93 (s, 2H, CH2), 6.93 (d, 2H, Ar, J = 6.42), 7.53 (d, 2H, Ar, J = 6.63),
7.67 (s, 1H, CH=N), 10.50 (1H, OH) ppm, 13C NMR (d6 - DMSO): δ= 39.8 (C, CH2 (amine
fragment), 116.60, 123.10, 131.75, 133.95 (6C, Ar), 134.84 (C, C=N, imine), 171.51 (C=O),
190.00 (C=S) ppm, Anal. Calcd. for C10H8N2O2S2 (M = 252): C, 47.60, H, 3.17, N, 11.20.
Found: C, 47.46, H, 3.38, N, 11.08.
Methoxycarbonylmethyl 3-(4-chlorobenzylidene)-dithiocarbazate (3a)
~
This compound was obtained as pale yellow crystalline, mp 139-141 °C; IR
υ
(KBr disc):
CO 1712, CN(imine) 1582(s) cm–1; H NMR (d6- DMSO): δ= 3.65 (s, 3H, OCH3), 4.15
(s, 2H, CH2), 7.55 (d, 2H, Ar, J = 8.16), 7.76 (d, 2H, Ar, J = 8.13), 8.25 (s, 1H, CH=N) ppm.
13C NMR (d6 - DMSO): δ = 36.25 (1C, CH2), 53.17 (1C, OCH3), (amine fragment), 130.01,
130.04, 133.03, 136.31, 138.67(6C, Ar), 146.51 (1C, C=N, imine), 169.76(C=O), 197.78
(C=S) ppm. Anal. Calcd. for C11H11ClN2O2S2 (M = 302.7): C, 43.60, H, 3.63, N, 9.25.
Found: C, 43.18, H, 3.56, N, 9.36.
1
Methoxycarbonylmethyl 3-(3-nitrobenzylidene)-dithiocarbazate (3b)
~
Mp 139-141 °C; IR
υ
(KBr disc): CO 1719, CN(imine) 1602(m), NO2 (1513, 1340) cm–1;
1H NMR (d6- DMSO): δ = δ= 3.66 (s, 3H, OCH3), 4.16 (s, 2H, CH2), 7.73-8.37 (4H, Ar),
8.54 (s, 1H, CH=N) ppm, 13C NMR (d6 - DMSO): δ = 36.29 (C, CH2 (amine fragment),
53.18 (1C, OCH3), 122.35, 125.87, 131.53, 134.49, 135.97, 145.44 (6C, Ar), 149.15
(C, C=N, imine), 169.70 (C=O), 197.74 (C=S) ppm. Anal. Calcd. for C11H11N3O4S2
(M = 313): C, 42.17, H, 3.51, N, 13.42. Found: C, 42.08, H, 3.49, N, 13.63.
Methoxycarbonylmethyl 3-(4-methoxybenzylidene)-dithiocarbazate (3c)
~
1
Mp 167-169 °C; IR
υ
(KBr disc): CO 1705, CN(imine) 1616(s) cm–1; H NMR (d6- DMSO):
δ= 3.86 (s, 3H, OCH3), 4.35 (s, 2H, CH2), 7.11 (d, 1H, Ar, J=5.4), 7.86 (d, 1H, Ar, J=5.1),
8.60 (s, 1H, CH=N) ppm, 13C NMR (d6 - DMSO): δ= 35.55 (C, CH2 (amine fragment),
56.45 (C, OCH3), 115.56, 125.17, 131.82, 164.03 (6C, Ar), 170.63 (C, C=N, imine), 171.15
(C=O), 197.69 (C=S) ppm. Anal. Calcd. for C12H14N2O3S2 (M = 298): C, 48.32, H, 4.70, N,
9.39. Found: C, 48.35, H, 4.57, N, 9.33.

538
M. TABATABAEE et al.
Methoxycarbonylmethyl 3-(2- hedroxy-3-methoxybenzylidene)-dithiocarbazate (3d)
~
Mp 173-174 °C; IR
υ
(KBr disc): CO 1706, CN(imine) 1616(s) cm–1; 1H NMR (d6- DMSO):
δ= 3.65 (s, 3H, OCH3), δ= 3.82 (s, 3H, OCH3), 4.15 (s, 2H, CH2), 6.84 (m, 1H, Ar), 7.04 (d,
1H, Ar, J=7.8), 7.30 (d, 1H, Ar, J = 7.73), 8.58 (1H, CH=N), 9.60 (1H, OH) ppm, 13C NMR
(d6 - DMSO): δ= 35.82 (C, CH2 (amine fragment), 52.75 (C, OCH3), 56.36 (C, OCH3),
114.37, 118.35, 119.86, 119.98, 144.85, 147.45 (6C, Ar), 148.56 (C, C=N, imine), 169.40
(C=O), 195.44 (C=S) ppm. Anal. Calcd. for C12H14N2O4S2 (M = 314): C, 45.86, H, 4.46, N,
8.92. Found: C, 45.81, H, 4.48, N, 8.81.
Methoxycarbonylmethyl 3-(4- hedroxybenzylidene)-dithiocarbazate (3e)
~
1
Mp 185-186 °C; IR
υ
(KBr disc): CO 1708, CN(imine) 1575(s) cm–1; H NMR (d6-
DMSO): δ= 3.64 (s, 3H, OCH3), 4.08 (s, 2H, CH2), 6.43 (d, 2H, Ar, J=8.0), 7.57 (d, 2H, Ar,
J=8.0), 8.15 (1H, CH=N), 10.13 (1H, OH) ppm, 13CNMR (d6 - DMSO):, 13C NMR (d6 -
DMSO): δ= 35.76 (C, CH2 (amine fragment), 52.71 (C, OCH3), 116.71, 124.50, 129.96,
160.77 (6C, Ar), 147.80 (C, C=N, imine), 169.50 (C=O), 194.96 (C=S) ppm. Anal. Calcd.
for C11H12N2O3S2 (M = 284): C, 46.48, H, 4.22, N, 9.86. Found: C, 46.26, H, 4.28, N, 9.75.
Results and Discussion
Reaction of N-aminorhodanine with a series of aromatic aldehydes was investigated to
afford the corresponding imines (2a-3e and 3a-3e) (Scheme 1). The results are listed in Table 1.
Table 1. Synthesis of imines of N-aminorhodanine under different condition
CH3CN (HCl,
CH3COOH)
Time, Yield,
Al2O3, MV
irradiation
CH3OH ( HCl)
Time, Yield,
Aldehyde
Time Yield,
%
Entry
Entry
Entry
h
8
8
8
8
%
h
%
Sec
4-Chlorobenzaldeyde
3-Nitrobenzaldehyde
4-Methoxybenzaldehyde
2-Hydroxy-3-
> 80
> 80
> 80
> 80
8
82
85
82
78
220 84
340 85
220 79
240 76
2a
2b
2c
2d
3a
3b
3c
3d
2a
2b
2c
2d
8
8
8
methoxybenzaldehyde
4-Hydroxybenzaldehyde
8
> 80
8
81
180 70
2e
3e
2e
As shown in Scheme 1, reactions of N-aminorhodanine with aldehyde in CH3CN,
MeOH (CH3COOH as acidic catalyst) or on Al2O3 under microwave irradiation led to 2
(2a-2e), while reactions were performed in solvent such as methanol 3 (3a-3e) were formed.
The IR spectra of all compounds show a characteristic band in the region of 1595-1610 cm-1,
which can be assigned as stretching vibration bands for azomethine group (ν N=CH).
1
The similar range is also reported in literature8,10. H NMR spectra of the compounds
showed a sharp signal (singlet) in the region of 8.01- 9.10 ppm, which can be assigned
1
to the azomethine proton9,10. In addition to normal signals in H NMR spectra of 2 and
3, OCH3 signals of 3a-3e are obtained in the region of 3.61-3.6 ppm and 13C NMR
spectra showed a signal at in the region of 52.71-53.17 ppm which can be assigned to
the OCH3 group. As shown in scheme 2, HCl plays an important role to protonation of
carbonyl group and activation of carbon for nucleophilic attack of methanol oxygen,
followed by ring opening of N-aminorhodanine. Recently we reported the same ring
opening reaction in the reaction of N-aminorhodanine and 2-cholorobenzaldehyde in
ethanol and in the presence of HCl11.

Fast and Efficient Method for Imination of N-Aminorhodanine
539
S
S
N
1
H2N
O
Solvent: MeOH, Catalyst: HCl
Solvent: MeOH, Catalyst: MeCOOH
Solvent: MeCN, Catalyst: HCl or MeCOOH
Al2O3, MV iirradition
H
Ar
O
S
H
S
S
Ar
N
O
CH3
N
H
S
Ar
N
N
O
O
3
2
Scheme 1. Reaction of N-aminorhodanine with aromatic aldehydes under different
conditions
NH2
N
NH2
N
S
S
O
HCl/MeOH
OH
S
S
HOCH3
NH2
N
NH2
S
S
NH
OH
O
HOCH3
S
S
OCH3
Scheme 2
Acknowledgment
The author is grateful to Scientific Society of Nanotechnology, Islamic Azad University,
Yazd Branch, for the support of this work.

540
M. TABATABAEE et al.
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