Synthesis of new heteroatomic podands from ethyl 2-[(2-aminophenylamino) methylidene]-3-oxoalkanoates and thiophene-2,5-dicarboxaldehyde

Article abstract of DOI:10.1016/j.mencom.2012.09.020

Condensation of two moles of ethyl 2-[(2-aminophenylamino)methylidene]-3- oxo-3-(polyfluoroalkyl)propionates with 2,5-thiophene-dicarboxaldehyde results in new heteroatomic podands. X-ray data showed that in the solid state these molecules arrange in two

Full text of DOI:10.1016/j.mencom.2012.09.020

Mendeleev
Communications
Mendeleev Commun., 2012, 22, 284–286
Synthesis of new heteroatomic podands from
ethyl 2-[(2-aminophenylamino)methylidene]-3-oxoalkanoates
and thiophene-2,5-dicarboxaldehyde
Yulia S. Kudyakova,* Yanina V. Burgart, Pavel A. Slepukhin and Victor I. Saloutin
I. Ya. Postovsky Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences,
620990 Ekaterinburg, Russian Federation. Fax: +7 343 374 5954; e-mail: kud@ios.uran.ru
DOI: 10.1016/j.mencom.2012.09.020
Condensation of two moles of ethyl 2-[(2-aminophenylamino)methylidene]-3-oxo-3-(polyfluoroalkyl)propionates with 2,5-thiophene-
dicarboxaldehyde results in new heteroatomic podands. X-ray data showed that in the solid state these molecules arrange in two
independent chelating fragments of b-amino enone type, thiophene fragment being a spacer.
New podands and their metal complexes have attracted an
increasing interest owing to their importance in understanding
NH2
of the biochemical processes.1 The design of polydentate ligands
N
H
is directed to the recognition and transport of specific ions and
molecules2 and, also, to the developing of selective catalysts.3
O
a R = OEt
b R = Me
c R = CF3
d R = (CF2)2H
EtO2C
Having the ability to self-organization simple binuclear ligands
R
1a–d
form the complex three-dimensional supramolecular systems with
unique properties.4–9
O
O
Previously, we studied reactions of ethyl 2-[(2-aminophenyl-
amino)methylidene]-3-oxo-3-(polyfluoroalkyl)propionates of
type 1 with monoaldehydes10 and diamines11,12 leading to sym-
metrical and nonsymmetrical ligands with one complexation
centre. Recently,13 we described the use of thiophene-2,5-
dicarboxaldehyde 2 in the synthesis of polydentate ligands.13 This
dialdehyde has a wide application in the synthesis of macrocyclic
and acyclic Schiff bases,14–16 furthermore, sulfur atom
can participate in additional coordination with metal ions and,
thereby, provide the formation of polyene system. Its condensa-
tion with diethyl 2-[(2-aminophenylamino)methylidene]malonate
1a was found to give tetraethyl 2,2'-[2,5-thienylbis(aminomethyl-
idene-2-iminophenylene)]dimalonate 4a13 (Scheme 1) having the
single O2N4S macroacyclic chelating cavity.
S
C6H6, azeotropic
removal of water
H
H
2
1 :1
2 :1
R = OEt
R = (CF2)2H
CO2Et
EtO2C
OEt
EtO
CO2Et
(CF2)2H
O
O
N
N
O
H
N
N
H
H
O
H
N
N
S
S
The aim of this work was to synthesize similar polydentate
geteratomic ligands based on compounds 1b–d11,12 and thiophene-
2,5-dicarboxaldehyde 2. We anticipated that the compounds thus
obtained can find use in access to some binuclear metalcomplexes
or anion receptors.17 The presence of thiophene ring as a spacer in
the molecules of bis-condensation products providestheextensive
polyene system that can promote various practically useful properties
(e.g., electroconductivity).
4a, 80%
3, 72%
2 :1
R = Alk
N
R
N
S
O
H
H
O
CO2Et
N
EtO2C
N
We found that the interaction between compounds 1b–d
(2 equiv.) and dialdehyde 2 proceeded regioselectively with the
formation of bis-condensation products – bis-azomethines 4b–d
(Scheme 1). The reaction was carried out in benzene in the presence
of AcOH with the azeotropic removal of water.
R
4b–d, 62–74%
Scheme 1
We also changed the starting reactant ratios to get mono-con-
densation products. However, monoazomethine 3 was obtained
in only one case of tetrafluoroethyl-containing compound 1d.
Polyfluoroalkyl-substituted oxo esters seem to be less reactive
compared to the non-fluorinated analogues as seen from the lower
yields (62–64% for fluoroalkylated products 4c,d and 75–80%
for non-fluorinated podand 4b).
†
1
The H NMR spectrum of azomethine 3 contains two sets of signals
since in a CDCl3 solution this compound exists as a mixture of Z and E
isomers relative to the C=C bond.
According to the 1H and 19F NMR data podands 4b–d in CDCl3 solu-
tions exist as mixtures of EE- and ZZ-isomers. ZZ-isomers apprearance
seems to occur because of the partial isomerisation of crystalline EE-isomer
under dissolution. The ease of isomerisation of the C=C bonds in com-
pounds 4b–d is due to their being a push-pull conjugated system in which
the rotation barrier around the C=C double bonds is decreased.
The structures of compounds 3 and 4b–d were characterized
1
by IR, H and 19F NMR spectroscopy† and elemental analysis
© 2012 Mendeleev Communications. All rights reserved.
– 284 –

Mendeleev Commun., 2012, 22, 284–286
Table 1 Parameters of intramolecular hydrogen bonds in the molecules
O(1)
C(6)
C(5)
C(22)
of compounds 4b,d.
C(21)
C(20)
C(2)
C(23)
C(24)
C(3)
N(1)–H(1)···O(3)
N(4)–H(4)···O(4)
C(4)
O(3)
O(2)
C(25)
N(4)
C(19)
C(1)
C(7)
Parameter
N(3)
S(1)
C(32)
C(31)
4b
4d
4b
4d
C(18)
N(1)
C(8)
O(6)
N(2)
C(26)
C(27)
C(15)
C(17)
d(N–H)/Å
d(H···O)/Å
ÐNHO/°
0.93(2)
1.89(9)
131.3(5)
2.61(0)
0.84(6)
1.99(2)
132.6(9)
2.63(9)
0.85(1)
1.97(4)
133.6(1)
2.63(4)
0.86(8)
1.96(9)
136.4(0)
2.66(6)
C(9)
C(30)
O(5)
C(13)
C(14)
C(16)
O(4)
C(29)
C(28)
C(10)
C(11)
C(12)
d(N–O)/Å
Figure 1 X-ray structure of 4b (thermal ellipsoids at 50% probability
level, ORTEP drawing).
F(8)
C(30)
F(7)
C(10)
C(9)
(see Online Supplementary Materials). X-ray study for products
4b,d was carried out.
F(6)
O(5)
F(5)
C(11)
C(13)
C(29)
C(15)
S(1)
C(12)
C(7)
N(1)
C(6)
C(27)
C(26)
O(6)
C(8)
In contrast to the previously obtained podand13 4a, compound
4b‡ has two independent coordination centres of b-amino enone
type, which are connected via central thiophene cycle and located
in the trans-position with respect to each other. The deviation
of C(9)C(11)C(13) plane of one phenylene fragment from the
C(18)N(3)C(22) plane containing thiophene cycle and another
phenylene is 24.8°, that makes the molecule non-planar. In crystal
compound 4b is s-trans,s-cis-conformer of EE-isomer of bis(amino
enone) tautomer (Figure 1).
C(16)
C(32)
C(34)
O(4)
C(25)
C(14)
N(2)
C(17)
N(4)
N(3)
C(19)
C(20)
C(18)
O(2)
C(24)
C(2)
O(3)
C(3)
C(31)
F(2)
C(23)
C(22)
C(21)
F(1)
C(4)
C(33)
C(1)
O(1)
C(5)
F(3)
F(4)
Figure 3 X-ray structure of 4d (thermal ellipsoids at 50% probability
level, ORTEP drawing)
There are two intramolecular hydrogen bonds (IMHB) in the
molecule with the participation of two NH groups of phenylene-
diamine moiety and two oxygen atoms of acetyl groups: N(1)–
H(1)···O(3) and N(4)–H(4)···O(4) (Table 1). Note that carbonyl
groups of acetyl fragments take part in the formation of IMHB
rather than ethoxycarbonyl groups as in the case of compound 4a.
The molecular packing (Figure 2) in the unit cell of compound
4b is organized by the two types of intermolecular hydrogen
bonding. The first type includes the interactions between atoms
O(4) and H(29A) of acetyl groups [2.66(7) Å] and the second type
is realized through the interaction of atoms O(1) and H(31B) of
ethoxycarbonyl groups of the adjacent molecules [2.89(9) Å].
To determine the influence of fluoroalkyl substituents on the
spatial structure of the molecule the X-ray analysis of 4d‡ was
carried out. Similarly to 4b, diethyl 2,2'-[2,5-thienylbis(amino-
methylidene-2-iminophenylene)]bis(3-oxo-4,4,5,5-tetrafluoro-
pentanoate) 4d in crystal is s-trans,s-cis-conformer of EE-iso-
mer of bis(amino enone) tautomer (Figure 3) and also has two
independent coordination centres. Acceptor properties of the fluoro-
alkyl group lead to the intramolecular H-bonding between NH
groupsofphenylenediaminemoietyandoxygenatoms of fluoroacyl
fragment: N(1)–H(1)···O(3) and N(4)–H(4)···O(4) (Table 1).
The presence of the polyfluoroalkyl groups in the molecule
changes the crystal packing so that the orientation of polyfluoro-
alkyl and hydrocarbon chains as a result of the intermolecular
interactions H···F [2.86(1) Å] becomes determinative (Figure 4).18
Unlike bis-azomethine 4b, where the intermolecular hydrogen
bonding makes the groups naturally equal, in the compound 4d
the interactions between fluorinated ethyl substituent and non-
fluorinated one take place. This reason accounts for the different
molecule packing.
H
H
2.89(9) Å
2.89(9) Å
O
O
2.66(7) Å
O
H
H
O
O
2.66(7) Å
O
2.89(9) Å
2.89(9) Å
H
H
Figure 2 The molecular packing of 4b (along the c axis).
‡
Crystallographic data for 4b: C32H32N4O6S, M = 600.68, monoclinic,
space group C2/c, a = 35.621(4), b = 10.5006(13) and c = 17.9570(9) Å,
b = 116.539(8)°, V = 6008.9(10) Å3, Z = 8, dcalc = 1.328 g cm–3, m(MoKa) =
= 0.159 cm–1, F(000) = 2528. A total number of 14194 reflections were
measured on an Xcalibur 3 diffractometer at 295(2) K [w/2q-scanning
technique, MoKa radiation (l = 0.71073 Å), graphite monochromator,
CCD detector], 5698 independent reflections (Rint = 0.0501), 2149 reflec-
tions with F0 > 4s(F0). The structure was solved by direct methods and
refined by the least-squares method with the use of SHELXL-9719
program package to R1 = 0.0416, wR2 = 0.0498 and GOOF = 0.998 [based
on reflections with I > 2s(I)].
Crystallographic data for 4d: C34H28F8N4O6S, M = 772.66, monoclinic,
space group C2/c, a = 65.3010(17), b = 5.4738(4) and c = 19.2195(13) Å,
b = 99.368(5)°, V = 6778.3(7) Å3, Z = 8, dcalc = 1.514 g cm–3, m(MoKa) =
= 0.192 cm–1, F(000) = 3168. A total number of 13122 reflections were
measured on an Xcalibur 3 diffractometer at 293(2) K [w/2q-scanning
technique, MoKa radiation (l = 0.71073 Å), graphite monochromator,
CCD detector], 6707 independent reflections (Rint = 0.0394), 3747
reflections with F0 > 4s(F0). The structure was solved by direct methods
and refined by the least-squares method with the use of SHELXL-9719
program package to R1 = 0.0561, wR2 = 0.1434 and GOOF = 1.004 [based
on reflections with I > 2s(I)].
H
2.84(8) Å
F
F
H
2.84(8) Å
2.84(8) Å
F
H
H
F
CCDC 848029 and 800075 contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
For details, see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 2012.
2.84(8) Å
Figure 4 The molecular packing of 4d (along the c axis).
– 285 –

Mendeleev Commun., 2012, 22, 284–286
7 S. J. Wezenberg and A. W. Kleij, Angew. Chem. Int. Ed., 2008, 47, 2354.
In summary, perspective approach to the synthesis of open-
chain macroacyclic heteroatomic polydentate ligands was demon-
strated. The ligands obtained are challenging for the further
physicochemical research.
8 A. W. Kleij, Dalton Trans., 2009, 24, 4635.
9 J. Niemeyer, G. Kehr, R. Fröhlich and G. Erker, Eur. J. Inorg. Chem.,
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This work was supported by the Russian Foundation for Basic
Research-Ural (project no. 10-03-96017) and the Presidium of
Ural Branch of the Russian Academy of Sciences (Programme
no. 12-T-3-1025).
13 Yu. S. Kudyakova, Ya. V. Burgart and V. I. Saloutin, Khim. Geterotsikl.
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Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.mencom.2012.09.020.
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Received: 3rd May 2012; Com. 12/3920
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