Unprecedented N(H)-bridged tetraaza[1.1.1.1]m,p,m,p-cyclophanes

Article abstract of DOI:10.1016/j.tet.2010.03.114

The first uncatalyzed preparation of tetraaza[1.1.1.1]m,p,m,p-cyclophanes (symmetrical and unsymmetrical) gave access to previously unknown N(H)-bridged derivatives that could be further substituted. NMR studies and theoretical calculations show that thes

Full text of DOI:10.1016/j.tet.2010.03.114

Tetrahedron 66 (2010) 4377–4382
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Unprecedented N(H)-bridged tetraaza[1.1.1.1]m,p,m,p-cyclophanes
,
,
*
Mounia Touil a b, Jean-Manuel Raimundo a, Mohammed Lachkar b, Philippe Marsal a, Olivier Siri a
a Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), UPR 3118 CNRS, Aix-Marseille Universite´, Campus de Luminy, case 913, F-13288 Marseille cedex 09, France
b Universite´ Sidi Mohamed Ben Abdellah, Faculte´ des Sciences Dhar El Mahraz Laboratoire d’Inge´nierie des Mate´riaux Organome´talliques et Mole´culaires ‘L.I.M.O.M.’,
´
`
Departement de Chimie, B.P. 1796, Atlas, 30000, Fes, Morocco
a r t i c l e i n f o
a b s t r a c t
Article history:
The first uncatalyzed preparation of tetraaza[1.1.1.1]m,p,m,p-cyclophanes (symmetrical and un-
symmetrical) gave access to previously unknown N(H)-bridged derivatives that could be further
substituted. NMR studies and theoretical calculations show that these macrocycles adopt an 1,3-alter-
nated conformation.
Received 25 November 2009
Received in revised form 29 March 2010
Accepted 30 March 2010
Available online 8 April 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Macrocycle
Cyclophane
Nucleophilic aromatic substitution
1. Introduction
The reported syntheses of N(R)-bridged [14]m,p,m,p-cyclo-
phanes 1 (R¼alkyl or aryl) are based on palladium-catalyzed aryl
amination reactions (Scheme 1).18–21 To the best of our knowledge,
the access to the sole alkylated derivative of type 1 (R¼CH3) was
described with an abysmal yield of 0.28% preventing its use in
spintronic application despite a rare stability in the triplet state.19
Cyclophanes have attracted much attention owing to their re-
markable electronic and spectroscopic properties but also as
effective host molecules in molecular recognition chemistry.1,2
Although carbon is the most common bridging element in useful
macrocyclic compounds, such as calixarenes3–5 and cyclophanes,1,2
considerable efforts are now devoted to the synthesis of various
heteroatom-bridged [14]-cyclophanes in order to obtain additional
chemical and physical properties.6–16 Among them, tetraazacyclo-
phanes that contain two p-phenylenediamine units connected by
a m-phenylene unit (i.e., N(R)-bridged [14]m,p,m,p-cyclophanes of
type 1) appeared very attractive for the preparation of stable rad-
icals (R¼aryl or CH3),17–20 hole transport materials21 and/or organic
light emitting diodes (OLEDs).22–24
R
R
R
R
N
N
NH
NH
N
N
Pd(II)
Br
Br
R
R
H
H
R
R
N
N
1a R = aryl > 30 %
1b R = CH3 0.28 %
N
N
N
N
N
N
Scheme 1. Synthesis of aza[14]m,p,m,p-cyclophanes by Pd catalyzed amination.18,20,21
N(H)-bridged [14]-m,p,m,p-cyclophanes of type 2 are hitherto
unknown although they are much more attractive owing to pos-
sible direct substitutions of the NH sites, which open un-
precedented perspectives in m,p,m,p-azacyclophane chemistry. The
palladium-catalyzed synthesis of molecules 2 could not be per-
formed probably due to the unstability of the p-diaminobenzene
precursors (i.e., primary p-diamines) under these conditions so that
their access is still a challenge of major interest.
H
H
R
R
2
1
* Corresponding author. E-mail address: siri@univmed.fr (O. Siri).
0040-4020/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.03.114

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M. Touil et al. / Tetrahedron 66 (2010) 4377–4382
An alternative route that would: (1) not require the use of
catalyst, (2) give access to N(H)-bridged aza[14]m,p,m,p-
a
cyclophanes of type 2, and (3) allow further functionalization of the
macrocycle, would be obviously of great interest to enlarge the
scope of this family of compounds. Herein, we report a synthetic
strategy, that is, based on stepwise nucleophilic aromatic sub-
stitutions (SNAr), assisted by hydrogen bonding interactions for
controlling the conformation of the key intermediates. The new
N(H)-bridged aza[14]m,p,m,p-cyclophanes of type 2 could then be
further directly N-substituted.
2. Results and discussion
The commercially available p-diaminobenzene derivatives were
used as nucleophilic components for which introduction of
substituents could be achieved and because of the possibility to
prepare N(H)-bridged aza[14]cyclophanes of type 2. 1,5-Difluoro-
2,4-dinitrobenzene was identified as their coupling partner of
choice owing to the presence of structural elements for SNAr (the
C–F carbon atoms are strongly electrophile due to the two elec-
tronwithdrawing NO2 groups on the phenyl ring).
The condensation of the substituted diamine 3b with 4 was first
envisaged in order to discuss the regioselectivity of the reaction (i.e.,
the position of the methyl group in the formed product). Thus,
2,5-diaminotoluene 3b was reacted with 4 (1 equiv) in EtOH in the
presence of N(iPr)2(Et) to give the [1þ1] adduct 5, which precipitated
in 84% yield (Scheme 2). Its 1H NMR spectrum shows the NH reso-
nance at 10.07 ppm consistent with the presence of a NH/O2N
intramolecular hydrogen bond. The two doublets at 6.60 and
8.90 ppm correspond tothe couplingof thearomaticprotons with the
Scheme 2. Synthesis of aza[14]m,p,m,p-cyclophanes 7a–c.
The reported stepwise strategy also allowed the synthesis of the
unsymmetrical mixed macrocycle 7c from 5. Indeed, compound 5
could be condensed with 1,4-diaminobenzene at Cz10ꢀ2 M in
EtOH to furnish the unsymmetrical intermediate 6c as a brown
solid (70% yield). As expected, its 1H NMR spectrum shows two NH
4
fluoride atom (3J(HF)¼14.5 Hz and J(HF)¼8.0 Hz, respectively). We
anticipated that the presence of Me in 3b should ‘activate’ the NH2
function in ortho position by inductive donor effect (þI). As expected,
the NMR data are in agreement with the formation of a single
regioisomer 5 for which the location of the CH3 group on the phenyl
ringwithrespecttotheNHbridgeisinorthoposition(onlyoneisomer
could be observed in solution). The assignment of the peaks was
determined by HMQC, HMBC, NOESYand COSY 2DNMRexperiments.
More specifically, the NOESY NMR spectrum clearly indicates that the
NH proton is coupled through space with the methyl group.
signals at
d¼9.50 and 9.52 ppm in agreement with two H-bonds
that favour the cyclization step. The macrocyclization from
reactions between 6c and 4 in refluxing MeCN gave 7c in 66% yield.
These observations are consistent with SNAr reactions assisted by
H-bonding interactions, which prevent the formation of polymeric
materials or linear oligomers even under low dilution conditions
(Cz10ꢀ1 to 10ꢀ2 M).
The 1H NMR spectra of 7b and 7c show unusual high-field
chemical shifts. For instance, 7c exhibits two resonances of the
O2N
NO2
intraannular aromatic protons Ha at
d
¼5.43 and 5.64 ppm (Fig. 1).
H
N
These 1H NMR data suggest that molecules of type 7 adopt
a conformation in which the Ha protons (internal protons) are
located inside the anisotropic shielding cone of the adjacent aro-
matic rings (Fig. 2). This conformation can be described as an
1,3-alternated saddle-shape geometry in which the two
p-substituted phenyl units are tilted to the plane identified by the
four bridging nitrogen atoms. The resonance of the corresponding
F
CH3
NH2
Similarly to the synthesis of 5, molecules 3a–b were reacted
with 4 (0.5 equiv instead of 1) at Cz10ꢀ1 to 10ꢀ2 M in EtOH to
afford the [2þ1] adducts 6a,b, which precipitated in good yields
(Scheme 2). Their 1H NMR spectra show two down-field NH pro-
tons at
d
¼9.51 and 9.52 ppm for 6a and 6b, respectively, in agree-
ment with NH/O2N hydrogen bonding interactions that restrict
the rotation of the uncyclized precursors.25 By analogy with 5, the
formation of only one regioisomer of type 6 is controlled by elec-
tronic effect (þI). Molecules 6a and 6b appeared then preorganized
for an efficient cyclization. The macrocyclization from reactions
between 6a or 6b and 4 in refluxing MeCN (Cz10ꢀ2 M) afforded
the target molecules 7a and 7b in 84 and 50% yield, respectively
(Scheme 2). These compounds are easily obtained in pure form as
yellow (7a) or orange (7b) solids by precipitation (no need of
purification by chromatography).
Figure 1. 1H NMR spectra of 6c (top) and 7c (bottom) in DMSO-d6. The range 0–4 ppm
are omitted for clarity.

M. Touil et al. / Tetrahedron 66 (2010) 4377–4382
4379
Ha proton in 6c at
(Ha in 6c is poorly influenced by the adjacent aromatic rings due to
a higher degree of freedom).
d
¼6.37 ppm further supports the geometry of 7c
It is noteworthy that the parent N(H)-brided cyclophane 7a
could not be characterized in solution due its lack of solubility even
in DMSO. This result would suggest the formation of a supramo-
lecular polymer for which the p-substituted phenyl rings interact
intermolecularly with: (i) the dinitro substituted rings via strong
Hb
p–p interactions based on donor/acceptor principle, and/or (ii) the
O2N
HN
NO2
NH
p-substituted phenyl bridges. This hypothesis was supported by
X-ray powder diffraction studies of 7a, which revealed the presence
of several peaks consistent with an organized arrangement of the
molecules in different directions (Fig. 5).
Ha
Ha
NH
HN
O2N
NO2
Hb
Figure 2. View of the 1,3-alternated conformation of molecule 7c.
This geometry, suggested in solution, was also confirmed by
theoretical studies. We performed a simulated annealing calcula-
tion to explore the potential energy surface at SAM1/d27,28 level
with AMPAC package,29 defaults have been used. In a second step,
we characterised the obtained global energy minima by B3LYP/
6-31G(d),30 geometry optimisation, and by frequency calculation
(Gaussian03 package).31 As expected, the obtained geometrical
parameters show that macrocycle 7c has an 1,3-alternated con-
formation in which the two p-substituted phenyl units are tilted to
the plane identified by the four bridging nitrogen atoms by around
62ꢁ (for instance, the dihedral angle between atoms
C(7)–N(1)–C(1)–C(2) is of 62.55ꢁ, see Fig. 3).
Figure 5. X-ray diffraction spectrum of 7a.
Introduction of one (7c) or two (7b) substituents (Me) on such
phenyl units leads to soluble molecules due to the breaking of the
supramolecular network. The N-methyl analogue 8dwhich could
be prepared in 65% yield by alkylation of 7a with MeI in refluxing
DMF (Scheme 3)dis also insoluble. This observation supports that
molecule 8 leads in the solid-state to the formation of a supramo-
lecular polymer similar to that of 7a (the presence of N-Me sub-
stituents do not disturb the
p stacking).
Scheme 3. Synthesis of N-methylated aza[14]m,p,m,p-cyclophane 8.
Figure 3. Geometry optimisation of 7c.
Interestingly, molecule 1 for which R¼CH3 is soluble in organic
solvents (CHCl3 and AcOEt).19 This drastic difference of the solu-
bility between 1 (R¼CH3) and 8 can be explained by a ‘pseudo’
change of the nitrogen hybridation. Indeed, the bridging nitrogen
Interestingly, the 1H NMR spectrum of 7b in DMSO-d6 at room
temperature shows four resonances at 5.08, 5.10, 5.562 and
5.564 ppm integrating for 0.5H, in agreement with the presence of
two conformational isomers depending on the relative location of
the two methyl groups pointing to the same (syn) or opposite
direction (anti). This observation was supported by theoretical
calculations, which showed that the two conformers can co-exist in
solution because they are almost degenerated in energy (1.4 kJ/
mol) (Fig. 4).
atoms are sp3 for 1 (R¼CH3) preventing strong
p–p interactions
due to their flexibility. In contrast, they are strongly conjugated
with the nitro groups in 8 and as such, can be viewed as ‘pseudo’
sp2 nitrogen atoms by analogy with related tetranitro-tetraazacy-
clophanes.26 As a result, compound 8 is a more rigid macrocycle,
which favours the orientation of the phenyl rings for optimal p–p
interactions. This experimental assumption has been supported by
theoretical calculations performed on the analogous 7c, which
showed that nitrogen N(1) is ‘pseudo’ sp2 hybridized, making
a bond of 1.36 Å length with C(7), and of 1.42 Å with C(1). A similar
behaviour has been observed for N(2), N(3) and N(4) (Fig. 3).
The electronic properties of these new macrocycles were
examined on 7c (the most soluble) by cyclic voltammetry as well as
UV–vis spectroscopy. The redox potentials were measured in
Figure 4. Geometry optimisation of the two conformers (syn and anti) of 7c.

4380
M. Touil et al. / Tetrahedron 66 (2010) 4377–4382
a 0.1 M solution of tetrabutylammonium hexafluorophosphate
(TBAPF6) in DMF using a Ag/AgCl reference electrode and a plati-
num working electrode (1.6 mm2).
further substitutions). The new macrocycles 7 adopt in solution
an 1,3-alternated conformation (1H NMR analysis), which was
further supported by theoretical calculations. Such compounds
could be also easily and reversibly reduced (electrochemical
studies). This observation opens new perspectives for this class
of macrocycles (1, 2 and 7) because it should now be possible to
use them as n-dopable materials for the generation of radicals
anions as conductive species,40 or for the formation of iono-
metallic phases.41
The voltammogram of 7c exhibited an irreversible oxidationwave
at 1.270 V consistent with an EC mechanism due to a chemical evo-
lution after formation of the cation radical [7c]þꢂ (Fig. 6). As expected,
molecule 7c appeared much more difficult to oxidize than the
N(R)-bridged azacyclophanes 1 described in the lit.18,19 due to the
presence of the four nitro groups. In contrast, as electron-poor mac-
rocycle, 7c isdto the best of our knowledgedthe first example of
tetraaza[1.1.1.1]m,p,m,p-cyclophanes that could be reversibly reduced
(at ꢀ0.978 V). By analogy with related azacyclophanes,11,19 the access
to useful anion radicals might be now envisaged owing to the stabi-
lization of the charge by delocalization over the macrocycle.
4. Experimental
4.1. General remarks
Commercial analytical-grade reagents were obtained from
commercial suppliers and were used directly without further
purification. Solvents were distilled under argon prior to use and
dried by standard methods. 1H and 13C NMR spectra were recor-
ded in DMSO-d6 with a AC250 Bruker spectrometer, operating at
250 and 62 MHz, respectively. HMBC, HMQC NOESY and COSY 2D
NMR spectra were recorded in DMSO-d6 with AC400 or AC500
Bruker spectrometers. Chemical shifts are reported in
d units, in
parts per million (ppm). Splitting patterns are designed as s,
singlet; d, doublet; m, multiplet; br, broad. Elemental and MS
analyses were performed by the Spectropole of Marseille. ESI
mass spectral analyses were recorded on a 3200 QTRAP (Applied
Biosystems SCIEX) mass spectrometer. Cyclic voltammetric (CV)
data were acquired using a BAS100 Potentiostat (Bioanalytical
Systems) and a PC computer containing BAS100 W software
(v2.3). A three-electrode system with a Pt working electrode
(diameter 1.6 mm), a platinum counter electrode and an Ag/AgCl
(with 3 M NaCl filling solution) reference electrode was used.
Tetrabutylammonium hexafluorophosphate, was used as
received. The compound was studied at 1.10ꢀ3 M in DMF/TBAH
0.1 M. and cyclic voltammogram recorded at a scan rate of
100 mV sꢀ1. Ferrocene was used as internal standard. The dif-
fraction powder measurements were realized in transmission
mode by using an INEL diffractometer equipped with a linear
detector INEL CPS 120. The powder was disposed into a glass
capillary of 1 mm in diameter. The radiation length was 1.5418 Å
corresponding to Cu Ka.
Figure 6. Cyclic voltammogram of 7c in DMF at 25 ꢁC.
The UV–vis spectrum of 7c showed two major absorption peaks
at 226 (log
temperature (Fig. 7). The small shoulder lying at the longer wave-
length (near 400 nm) can be assigned to the n/ transition while
the peaks at the shorter should be caused by the transitions.
3
¼3.28) and 343 nm (log ¼3.54) in MeCN at room
3
p
l
p/p
*
4.2. Synthesis and characterization of the intermediates
4.2.1. N1-(5-Fluoro-2,4-dinitrophenyl)2-methylbenzene-1,4-diamine
(5). To
a
solution of 1,5-difluoro-2,4-dinitrobenzene
4
(m¼200 mg, 0.98 mmol, 1 equiv) and diisopropylethylamine
(v¼0.83 mL, 4.9 mmol, 5 equiv) in 10 mL of EtOH, was added
2,5-diaminotoluene 3b (m¼116 mg, 0.98 mmol, 1 equiv) at room
temperature. The mixture was then stirred at under reflux for
6 h and the reaction was monitored by TLC. The obtained pre-
cipitate was isolated by filtration and washed with hot water
and cold ethanol affording 5 as a brown solid in 84% yield
(m¼205 mg).
Figure 7. UV–vis spectrum of 7c in MeCN at room temperature.
3. Conclusion
In summary, we described the first metal-free synthesis of
tetraaza[1.1.1.1]m,p,m,p-cyclophanes, which allowed the access
to unprecedented N(H)-bridged derivatives 7a–c (symmetrical
and unsymmetrical). This preparation has been achieved by
SNAr assisted by hydrogen bonding interactions, which
preorganize the intermediates for an efficient cyclization (no
polymerization observed even under low dilution conditions). In
addition to the NH bridging sites that can be further directly
substituted (8), the potential presence of four NH2 functions (by
reduction of the NO2 groups) open new pespectives as electro-
nrich molecules for the preparation of high-spin organic mate-
rials,19 as new hosts in supramolecular chemistry2,5,32,33 and/or
as new N-donor ligands in coordination chemistry34–39 (possible
1H NMR (250 MHz, DMSO-d6):
d
ppm 2.07 (s, 3H, CH3), 5.16 (br s,
3
2H, NH2), 6.60 (d, 1H, JHF¼14.5 Hz, aromatic H), 6.66 (d, 1H,
3JHH¼8.3 Hz, aromatic H), 6.90 (m, 2H, aromatic H), 8.90 (d, 1H,
4JHF¼8.0 Hz, aromatic H), 10.07 (br s, 1H, NH); 13C{1H} NMR
2
(62 MHz, DMSO-d6):
d
ppm 17.34 (s, CH3), 102.70 (d, JCF¼26 Hz,
HC–CF), 114.24, 122.08, 124.41, 124.88, 127.10, 127.44, 127.67, 146.36,
1
148.90, 149.11 (s, aromatic C), 158.79 (d, JCF¼302 Hz, C–F); MS
(ESI): 307 [MþH]þ; calculated for C13H11N4O4F: C 50.98, H 3.62, N
18.29; found: C 51.27, H 3.74, N 18.27.
4.2.2. N,N0-(4,6-Dinitro-1,3-phenylene)dibenzene-1,4-diamine
(6a). To
a
solution of p-phenylenediamine 3a (m¼353 mg,

M. Touil et al. / Tetrahedron 66 (2010) 4377–4382
4381
1.96 mmol, 2 equiv) and diisopropylethylamine (v¼0.85 mL,
4.9 mmol, 5 equiv) in EtOH was added 1,5-difluoro-2,4-
dinitrobenzene 4 (m¼200 mg, 0.98 mmol, 1 equiv). The mixture
was then stirred for 24 h under reflux affording 6a (precipitate),
which was isolated by filtration as a brown solid (m¼320 mg, 86%
yield).
4.3.2.2. 3,15-Dimethyl-8,10,19,20-tetranitro-1,6,12,17-tet-
raaza[14]-cyclophane (7b). Orange solid (m¼140 mg, 50% yield): 1H
NMR (250 MHz, DMSO-d6):
d ppm 2.38 (s, 6H, CH3), 5.08 (s, 0.5H,
Ha), 5.10 (s, 0.5H, Ha), 5.562 (s, 0.5H, Ha), 5.564 (s, 0.5H, Ha), 7.20
(m, 6H) aromatic H, 9.08 (m, 2H, Hb), 9.78 (m, 4H, NH); MS (ESI):
573 [MþH]þ; calculated for C26H20N8O8$1/3H2O: C 53.98, H 3.60, N
19.37; found: C 53.61, H 3.63, N 18.97.
1H NMR (250 MHz, DMSO-d6):
d ppm 5.15 (br s, 4H, NH2), 6.24
(s, 1H, NH–C]CH–C–NH), 6.51 (d, 4H, Jortho¼8.65, aromatic H), 6.90
(d, 1H, Jortho¼8.65, aromatic H), 9.01 (s, 1H, O2N–C]CH–C–NO2),
4.3.2.3. 3-Methyl-8,10,19,20-tetranitro-1,6,12,17-tetraaza[14]cy-
9.51 (br s, 2H, NH); 13C{1H} NMR (62 MHz, DMSO-d6):
d
ppm 93.44,
clophane (7c). Orange solid (m¼112 mg, 66% yield); 1H NMR
113.45, 123.46, 124.70, 125.20, 127.90, 146.18, 146.48 (aromatic C);
MS (ESI): 381 [MþH]þ; calculated for C18H16N6O4: C 56.84, H 4.24,
N 22.10; found: C 56.51, H 4.25, N, 21.60.
(250 MHz, DMSO-d6): d ppm 2.09 (s, 3H, CH3), 5.43 (s, 1H, Ha), 5.64
(s,1H, Ha), 7.12 (m, 7H, aromatic H), 9.02 (s,1H, Hb), 9.04 (s,1H, Hb),
9.68 (br s, 1H, NH), 9.70 (br s, 1H, NH), 9.72 (br s, 1H, NH), 9.96 (br s,
1H, NH); MS (ESI): 557 [MꢀH]þ; calculated for C25H18N8O8$1/
3H2O: C 53.20, H 3.33, N 19.85; found: C 53.09, H 3.33, N 19.44.
4.2.3. N,N0-(4,6-Dinitro-1,3-phenylene)bis(2-methylbenzene-1,4-di-
amine) (6b). To a solution of p-phenylenediamine 3b (m¼431 mg,
1.96 mmol, 2 equiv) and diisopropylethylamine (v¼0.85 mL,
4.9 mmol, 5 equiv) in EtOH was added 1,5-difluoro-2,4-di-
nitrobenzene 4 (m¼200 mg, 0.98 mmol, 1 equiv). The mixture was
then stirred for 24 h under reflux affording 6b (precipitate), which
was isolated by filtration as an orange solid (m¼310 mg, 77%
yield).
4.4. Synthesis and characterization of the N(R)-bridged
macrocycle
4.4.1. N,N0,N00,N%-Tetramethyl-8,10,19,20-tetranitro-1,6,12,17-tetraa-
za[14]cyclophane (8). To a stirred solution of 7a (m¼250 mg,
0,46 mmol, 1 equiv) in 10 mL of anhydrous DMF was added
potassium carbonate (m¼634 mg, 4,60 mmol, 10 equiv) under an
Ar atmosphere. The solution turns immediately into a dark red
colour and is left at room temperature for 20 min. To this red so-
1H NMR (250 MHz, DMSO-d6):
s, 4H, NH2), 6.33 (s, 1H, NH–C]CH–C–NH), 6.56 (d, 4H, Jortho
d ppm 2.01 (s, 6H, CH3), 4.94 (br
¼
8.09 Hz, aromatic H), 6.80 (m, 4H, aromatic H), 9.02 (s, 1H,
O2N–C]CH–C–NO2), 9.52 (br s, 2H, NH); 13C{1H} NMR (62 MHz,
lution was added methyl iodide (v¼242
ml, 3,68 mmol, 8 equiv) and
the obtained solution was then stirred overnight at 80 ꢁC affording
8, which was isolated by filtration as an orange solid and washed
with MeCN (m¼208 mg, 65% yield).
DMSO-d6):
d ppm 17.36 (CH3), 93.97, 114.00, 121.76, 123.18, 124.08,
125.47, 126.40, 128.54, 145.09, 146.70; MS (ESI): 409 [MþH]þ; cal-
culated for C20H20N6O4: C 58.82, H 4.94, N 20.58; found: C 58.77, H
4.97, N 20.21.
MS (ESI): 601 [MþH]þ; calculated for C28H24N8O8$CH3CN$1/
2 K2CO3: C 51.54, H 3.83, N 17.74; found: C 51.69, H 3.39, N 18.25.
4.2.4. N1-(4-Amino-2-methylphenyl)-N3-(4-aminophenyl)-4,6-di-
nitrobenzene-1,3-diamine (6c). To a solution of p-phenylenediamine
3a (m¼117.6 mg, 0.65 mmol, 1 equiv) and diisopropylethylamine
(v¼0.65 mL, 3.26 mmol, 5 equiv) in MeCN was added 5 (m¼306 mg,
0.65 mmol, 1 equiv). The mixture was then stirred for 8 h under
reflux to afford 6c (precipitate), which were isolated by filtration as
an orange solid (m¼180 mg, 70% yield).
Acknowledgements
This work was supported by the Centre National de la Recherche
Scientifique, the Ministere de la Recherche et des Nouvelles Tech-
nologies and the Agence Universitaire de la Francophonie (PhD
grant of M.T.). We thank Roselyne Rosas and Rose Haddoub for the
2D NMR studies, and Vasile Heresanu for the diffraction powder
measurements.
`
1H NMR (250 MHz, DMSO-d6):
d
ppm 2.03 (s, 3H, CH3), 4.94 (br
s, 2H, NH2), 5.19 (br s, 2H, NH2), 6.37 (s, 1H, NH–C]CH–C–NH), 6.53
(dd, 4H, Jortho¼8.6 Hz, Jmeta¼3.3 Hz, aromatic H), 6.77 (dd, 1H, Jortho
¼
8.36 Hz, Jmeta¼2.36 Hz, aromatic H), 6.85 (d, 1H, Jmeta¼2.36 Hz,
aromatic H), 6.92 (d, 1H, Jortho¼8.36 Hz, aromatic H), 9.00 (s, 1H,
O2N–C]CH–C–NO2), 9.50 (br s,1H, NH), 9.52 (br s,1H, NH); 13C{1H}
References and notes
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