An efficient one-pot, three-component synthesis of 5-hydrazinoalkylidene rhodanines from 1,2-diaza-1,3-dienes

Article abstract of DOI:10.1021/ol900545v

A novel three-component synthesis of 5-hydrazinoalkylidene rhodanine derivatives starting from aliphatic primary amines, carbon disulfide, and 1,2-diaza-1,3-dienes is described. The reaction proceeds successfully under both solution and solid-phase condit

Full text of DOI:10.1021/ol900545v

ORGANIC
LETTERS
2009
Vol. 11, No. 11
2265-2268
An Efficient One-Pot, Three-Component
Synthesis of 5-Hydrazinoalkylidene
Rhodanines from 1,2-Diaza-1,3-dienes
Orazio A. Attanasi,† Lucia De Crescentini,† Gianfranco Favi,*,† Paolino Filippone,†
Gianluca Giorgi,‡ Fabio Mantellini,† Giada Moscatelli,† and Mohamed S. Behalo§
Istituto di Chimica Organica, UniVersita` degli Studi di Urbino “Carlo Bo”, 61029
Urbino, Italy, Centro Interdipartimentale di Analisi e Determinazioni Strutturali,
UniVersita` di Siena, 53100 Siena, Italy, and Department of Chemistry, UniVersity of
Benha, 13518 Benha, Egypt
gianfranco.faVi@uniurb.it
Received March 18, 2009
ABSTRACT
A novel three-component synthesis of 5-hydrazinoalkylidene rhodanine derivatives starting from aliphatic primary amines, carbon disulfide,
and 1,2-diaza-1,3-dienes is described. The reaction proceeds successfully under both solution and solid-phase conditions.
Recently, multicomponent reactions (MCRs)1 have received
great attention from the chemical community because they
permit the building of architecturally complex molecules
† Universita` degli Studi di Urbino “Carlo Bo”.
‡ Universita` di Siena.
§ University of Benha.
(1) Zhu, J.; Bienayme´, H. Multicomponent Reactions; Wiley: Weinheim,
2005. For recent reviews on multicomponent reactions, see: (a) Ugi, I.;
Werner, B.; Dömling, A. In Targets in Heterocyclic Systems, Chemistry
and Properties; Attanasi, O. A., Spinelli, D., Eds.; Italian Society of
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2001, 73, 187–191. (c) Nair, V.; Rajesh, C.; Vinod, A.; U.; Bindu, S.;
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44, 1602–1634. (e) Do¨mling, A. Chem. ReV. 2006, 106, 17–89.
(2) For reviews on thiazolidinones, see: (a) Brown, F. C. Chem. ReV.
1961, 61, 463–521. (b) Singh, S. P.; Parmar, S. S.; Raman, K.; Stenberg,
V. I. Chem. ReV. 1981, 81, 175–203.
Figure 1. (a) Structures of 4-thiazolidinones. (b) Substituted
5-alkylidene rhodanines Aa as an important medicinal structure.
from relatively simple starting materials. Although significant
progress has been made in the area of MCRs, there is still a
high demand for new processes aimed at the rapid assembly
of heterocyclic molecules.
(3) (a) Troutman, H. D.; Long, L. M. J. Am. Chem. Soc. 1948, 70, 3436–
3439. (b) Foye, W. O.; Tovivich, P. J. Pharm. Sci. 1977, 66, 16076–1611.
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Miyhara, K.; Takano, T. Chem. Pharm. Bull. 1990, 38, 1911–1919. (d)
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4-Thiazolidinones2,3 are an important group of heterocyclic
compounds, which have been subject to extensive study in
the past years (Figure 1a). Among these 4-thiazolidinones,
the rhodanine A (2-thioxothiazolidin-4-ones4) motif repre-
sents an important medicinal scaffold. Thus, 5-benzyliden-
10.1021/ol900545v CCC: $40.75
Published on Web 04/27/2009
 2009 American Chemical Society

erhodanines have been reported as small molecule inhibitors
of numerous targets such as cyclooxygenase and
5-lipoxygenase,5a ꢀ-lactamase,5b cathepsin D,5c HCV NS3
protease,5d aldose reductase,5e protein mannosyl transferase,5f
protein tyrosine phosphatases,5g phosphodiesterase-4,5h and
JNK-stimulating phosphatase.5i
Recent findings include the identification of certain
substituted rhodanines (for example Aa) as potential medici-
nal leads in developing therapeutic agents for the treatment
of Alzheimer’s disease6 (Figure 1b). Furthermore, efficient
synthetic inhibitors of anthrax lethal factor (ALF)7 as well
as small molecule matrix metalloprotease (MMP) inhibitors8
containing novel rhodanine zinc-chelating groups have been
identified.
istry. Recently, a simple and effective approach to the
synthesis of rhodanine derivatives via three-component
reactions in water has also been reported by Alizadeh et al.13
On the basis of these experiences, and in continuation of
our ongoing interest in the discovery of new reactions for
the synthesis of heterocycles from azo-ene systems, we
designed a novel method for the preparation of 5-hydrazi-
noalkylidene rhodanines from amines, carbon disulfide, and
1,2-diaza-1,3-dienes (Scheme 1).
Scheme 1
.
Retrosynthetic Strategy for the Preparation of
5-Hydrazinoalkylidene Rhodanines
Standard procedures for the preparation of the 2-thioxothi-
azolidin-4-ones, including reactions of isothiocyanate with
R-mercaptoacetic acid or its ester, reactions of ammonia or
primary amines with carbon disulfide, and R-haloalkanoic
acids are known.2 While these protocols in general are
suitable for construction of the rhodanine core, the 5-alky-
lidene rhodanine substructure may be accessed by coupling
the thiazolidinone nucleus assembly with subsequent second-
ary transformations.9 Despite the importance of these 5-un-
saturated rhodanine derivatives, there are no reports that
allow the direct formation of C5 hydrazinoalkylidene func-
tionalized rhodanine from acyclic building blocks.
Initially,. we explored tentatively the reaction of benzyl-
amine 1a (1 mmol), carbon disulfide (1 mmol), and 1,2-
diaza-1,3-diene 2a (1 mmol) at room temperature in THF
without the use of any base as catalyst. Under these
conditions, we were delighted to obtain the product 4a in
61% yield (Table 1, entry 1). In an attempt to improve the
yield, we varied the molar ratios of the reagents. When a
ratio of 1.5/1/3 was used, the reaction successfully gave the
desired rhodanine 4a in the best yield (83%) (Table 1, entry
3). The reaction was also carried out in different organic
solvents such as EtOH, CH2Cl2, CH3CN, H2O, and DMF
including solvent-free conditions (Table 1). In EtOH and
CH2Cl2, the yields were similar to the ones in THF, while
On the other hand, the utility of 1,2-diaza-1,3-dienes10 in
organic synthesis has been recognized for their ready
accessibility and good reactivity from the high electrophilic
(C4) center that can lead to a variety of heterocyclic rings
by means of a wide range of nucleophiles.10,11
Moreover, it is well-known that amines with carbon
disulfide and alkyl halides, epoxides, or Michael acceptors
afford dithiocarbamates,12 which have a variety of applica-
tions in organic, medicinal, material and agricultural chem-
(4) The thioxo group in rhodanines is known as a carboxylic acid
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H.; Kim, H.-S.; Wataya, Y.; Ihara, M. J. Comb. Chem. 2003, 5, 211–214.
(b) Anderluh, M.; Jukicˇ, M.; Petricˇ, R. Tetrahedron 2009, 65, 344–350.
(10) For a review on the chemistry of 1,2-diaza-1,3-dienes, see: Attanasi,
O. A.; De Crescentini, L.; Filippone, P.; Mantellini, F.; Santeusanio, S.
ArkiVoc 2002, xi, 274–292.
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Org. Lett., Vol. 11, No. 11, 2009

Table 1. Three-Component Reaction of Benzylamine 1a,
Carbon Disulfide, and 1,2-Diaza-1,3-diene 2a: Optimization of
the Reaction Conditionsa
Table 2. One-Pot Synthesis of 5-Hydrazinoalkylidene
Rhodanines 4a-ta
amine 1
1,2-diaza-1,3-diene 2
R1 R2 R3
2a CO2t-Bu Me Et
product 4
yield (%)b
entry
1
2
4
molar ratios
1a/2a/CS2
product 3a
yield (%)
product 4a
1
2
1a
1a
1a
1a
1a
1a
1b
1b
1b
1b
1c
1c
1d
1d
1d
1e
1e
1f
4a
4b
83
73
56
83
85
43
59
57
52
73
44
69
59
82
88
81
54
60
72
80
entry
solvent
yield (%)c
2b CO2Me
2c CO2Bn
2d CO2Et
2e CO2Me
Me Et
Me Me 4c
Me Me 4d
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
9
THF
THF
THF
Et2O
CH3CN
EtOH
neat
CH2Cl2
H2O
1/1/1
1/1/2
s
63
74
83
s
Et
Me Et
2a CO2t-Bu Me Et
Me 4e
1.5/1/3
1.5/1/3
1.5/1/3
1.5/1/3
1.5/1/3
1.5/1/3
1.5/1/3
1.5/1/3
s
2f
C6H5
4f
4g
4h
77b
72b
s
s
s
2b CO2Me
2c CO2Bn
2e CO2Me
2e CO2Me
Me Et
Me Me 4i
81
29
80
trace
41
s
Et
Et
Me 4j
Me 4k
s
s
2f
2e CO2Me
2f C6H5
2a CO2t-Bu Me Et
C6H5
Me Et
Et Me 4m
Me Et
4l
10
DMF
27
a All reactions were carried out in the appropriate solvent (10 mL) using
benzylamine 1a, CS2, and 1,2-diaza-1,3-diene 2a until complete disappear-
ance of 2a (at rt for 10 min, TLC check). b Yields of isolated product by
precipitation. c Isolated yield after silica gel chromatography.
4n
4o
4p
2b CO2Me
2c CO2Bn
Me Et
Me Me 4q
2a CO2t-Bu Me Et
4r
4s
1f
1f
2b CO2Me
2d CO2Et
Me Et
Me Me 4t
in the case of H2O and neat condition the reaction proceeded
with lower yields and formation of byproduct. Other solvents
such as Et2O and CH3CN led exclusively to the formation
of the adduct intermediate 3a by simple precipitation from
the crude reaction mixture. To obtain the relative rhodanine
4a from compound 3a, we carried out the heterocyclization
process in EtOH and in the presence of DIPEA as base.
Having established the optimal conditions, we next
examined the extension of these conditions and the efficiency
of the protocol to other substrates by using several amines
1a-f and different 1,2-diaza-1,3-dienes 2a-f14 (Table 2,
entries 1-20). It is worth noting that the addition of DIPEA
(1.0 mmol) at the disappearance of the 1,2-diaza-1,3-dienes
2a-f (after 10-30 min, TLC check) is necessary to drive
the process to completion by conversion of the dithiocar-
bamate acyclic intermediate 3 into final 5-hydrazinoalky-
lidene rhodanines 4a-f.
In general, aliphatic primary amines such as benzylamine,
n-propylamine, n-butylamine, allylamine, 1-amino-2-pro-
panol, and 1-amino 2-acetaldehyde diethyl acetal worked
well to give the corresponding heterocyclic compounds.
Relatively hindered primary amines such as 1-phenyl-
ethylenamine and cyclohexylamine undergo efficient addition
with 1,2-diaza-1,3-diene Michael acceptors to give the
dithiocarbamate acyclic intermediate in excellent yields, but
a Reaction conditions. For a detailed experimental operation, see
Supporting Information. Amine (1.5 mmol), CS2 (3.0 mmol), 1,2-diaza-
1,3-diene (1.0 mmol), rt, 10 min (30 min when 2f was used). b Isolated
yield after silica gel chromatography.
only traces of the pertinent heterocycle were recovered. As
expected, moreover, the aromatic amines did not participate
in the reaction.
The structures of all products were established by spec-
troscopic methods.15 The structure of 4i was independently
confirmed by X-ray crystal structure analysis (see Supporting
Information). It is noteworthy that these rhodanine derivatives
4a-t were obtained exclusively in the hydrazino isomer with
E configuration.
On the basis of these findings and the well-established
chemistry of dithiocarbamates, a plausible mechanism for the
formation of hydrazinoalkylidene rhodanines 4 is presented in
Scheme 2. Initially, the intermediate 3A is produced by
nucleophilic attack of the in situ generated dithiocarbamic acid
I to the azo-ene system of 1,2-diaza-1,3-diene 2 via a Michael-
like 1,4-addition reaction. Successively, hydrazono-hydrazino
tautomerization of intermediates 3A produces 3B followed by
base-promoted intramolecular nucleophilic attack of the NH
dithiocarbamic group at the ester moiety with loss of the alcohol
molecule and formation of compound 4 (Scheme 2).
(13) Alizadeh, A.; Rostamnia, S.; Zohreh, N.; Hosseinpour, R. Tetra-
hedron Lett. 2009, 50, 1533–1535.
(14) 1,2-Diaza-1,3-dienes 1a-f were synthesized from the corresponding
chlorohydrazones by treatment with base (see Supporting Information).
Org. Lett., Vol. 11, No. 11, 2009
2267

in dichloromethane at room temperature to afford directly
hydrazinoalkylidene rhodanines 4a,o,r (Table 4). The overall
Scheme 2. Plausible Mechanism for the Formation of
5-Hydrazinoalkylidene Rhodanine Derivatives 4
Table 4. Solid-Phase Synthesis of 5-Hydrazinoalkylidene
Rhodanine Derivatives 4a,o,r
entry
amine 1
product 4
yield (%)b
1
2
3
1a
1d
1f
4a
4o
4r
25
18
15
To improve the usefulness of our synthetic protocol and with
the aim to obtain molecules containing two differently spaced
rhodanine rings, we next applied our procedure to the diamines
1g-i. The use of ethylenediamine 1g, 1,3-diaminopropane 1h,
and 1,4-diaminobutane 1i gave rise to the di(5-hydrazinoalky-
lidene rhodanine) derivatives 4u-w (Table 3).
a Reaction conditions. For a detailed experimental operation, see
Supporting Information. Amine (0.75 mmol), CS2 (1.5 mmol), 1,2-diaza-
1,3-diene (1.0 mmol), rt, 30 min. b Overall yields (after silica gel
chromatography) for the multistep process of pure isolated 4a,o,r with
respect to the starting Wang resin.
yields for the multistep process of these solid-phase reactions
are in the range of 15-25% and, therefore, comparable with
the corresponding reactions in solution.
Table 3. One-Pot Synthesis of Bis(5-hydrazinoalkylidene
rhodanines) 4u-wa
In summary, we have reported a novel, highly efficient, and
selective three-component synthesis of 5-hydrazinoalkylidene
rhodanine derivatives (exclusively in the E-hydrazino isomeric
form) starting from aliphatic primary amines, carbon disulfide,
and 1,2-diaza-1,3-dienes. When diamines were used in these
reactions, di(5-hydrazinoalkylidene rhodanines) were also pro-
duced.
In addition, we have shown that this procedure can be
applied successfully in a solid-phase approach. Therefore,
the usefulness of the present MCR as a powerful method to
obtain interesting final products, together with the mild and
simple reaction conditions of these procedures (no dry
solvents or inert atmosphere), makes it well suitable for the
generation of combinatorial libraries.
entry
amine 1
n
product 4
yield (%)b
1
2
3
1g
1h
1i
2
3
4
4u
4v
4w
64
59
65
a Reaction conditions. For a detailed experimental operation, see
Supporting Information. Amine (0.75 mmol), CS2 (3.0 mmol), 1,2-diaza-
1,3-diene (1.0 mmol), rt, 10 min. b Isolated yield after silica gel
chromatography.
Acknowledgment. This work was supported by the
financial assistance from the Ministero dell’Istruzione,
dell’Universita` e della Ricerca (MIUR) Roma, Universita`
degli Studi di Urbino, Italy, and Ministry of Higher Educa-
tion, Scientific Research, Egypt (Parown grant).
In consideration of the mild and simple conditions required
from these reactions in the liquid phase, we finally investigated
the solid-phase16 version of this methodology. Thus, Wang resin
polymer-bound 1,2-diaza-1,3-diene 2g (1.25 g) obtained by a
modified procedure previously reported17 readily reacted with
1.5 equiv of carbon disulfide and 0.75 equiv of amines 1a,d,f
Supporting Information Available: Experimental pro-
cedures and full characterization for all compounds. X-ray
crystallographic data (CIF file) and ORTEP drawing of
compound 4i. This material is available free of charge via
the Internet at http://pubs.acs.org.
(15) For example, the hydrazinoalkylidene rhodanine 4a has been
elucidated as follows: (a) its IR spectrum exhibited strong absorption bands
1
at 1707, 1658 (CdO), and 1191 cm-1 (CdS); (b) the H NMR spectrum
of 4a in CDCl3 showed two singlets attributed to the hydrazino (δ ) 10.33
and 6.52 ppm) protons; (c) its 13C NMR showed characteristic signals at δ
) 191.2 (CdS), 166.7, 157.2 (CdO), 154.7, and 92.8 (CdC). (d) The mass
spectrum of 4a displayed a molecular ion peak at m/z ) 379 [M+].
(16) For a solid-phase synthesis of rhodanines by a different strategy,
see: Lee, C. L.; Sim, M. M. Tetrahedron Lett. 2000, 41, 5729–5732.
OL900545V
(17) Attanasi, O. A.; De Crescentini, L.; Filippone, P.; Mantellini, F.;
Tietze, L. F. Tetrahedron 2001, 57, 5855–5863. For the modified procedure,
see Supporting Information.
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