Simple 1-dicyanomethylene-2-chloro-3-aminoindene push-pull chromophores: Applications in cation and anion sensing

Article abstract of DOI:10.1039/b916700e

Push-pull chromophores based on 1-dicyanomethylene-2-chloro-3-aminoindene are readily synthesized. These compounds undergo dramatic colour changes in the presence of metal cations as a result of the interaction of the amino substituent with the analytes. One of these compounds is a selective copper(ii) colorimetric probe in acetonitrile solution, displaying a dramatic colour change upon coordination of the amine group to the metal centre. These compounds are also selective cyanide sensors in acetonitrile solution because of the disruption of the intramolecular charge transfer process as the result of the nucleophilic addition of the anion to the indene moiety.

Full text of DOI:10.1039/b916700e

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Simple 1-dicyanomethylene-2-chloro-3-aminoindene push–pull chromophores:
applications in cation and anion sensing†
Sara Basurto,a Daniel Miguel,b Daniel Moreno,a Ana G. Neo,c Roberto Quesadaa and Toma´s Torroba*a
Received 13th August 2009, Accepted 23rd October 2009
First published as an Advance Article on the web 27th November 2009
DOI: 10.1039/b916700e
Push–pull chromophores based on 1-dicyanomethylene-2-chloro-3-aminoindene are readily
synthesized. These compounds undergo dramatic colour changes in the presence of metal cations as a
result of the interaction of the amino substituent with the analytes. One of these compounds is a
selective copper(II) colorimetric probe in acetonitrile solution, displaying a dramatic colour change
upon coordination of the amine group to the metal centre. These compounds are also selective cyanide
sensors in acetonitrile solution because of the disruption of the intramolecular charge transfer process
as the result of the nucleophilic addition of the anion to the indene moiety.
Introduction
Results and discussion
Development of molecular probes capable of detecting cations,
anions or neutral molecules by a change in their optical signals is
an area of intense research.1 Industrial processes often demand
detection methods that require sophisticated instrumentation
such as atomic absorption/emission spectrometry or inductively
coupled plasma mass spectroscopy.2 These analytical techniques
are not very suitable for fast detection protocols. Therefore, it
is important to develop methods allowing rapid, straightforward
analyte detection. In this regard, colorimetric sensors offer the
advantage of providing information with minimal equipment,
allowing the so-called “naked-eye” detection. There are numerous
examples of colorimetric probes for anionic and cationic species.3
Common drawbacks of these systems are that they often require
complicated synthesis and their design is not flexible, therefore
every analyte requires its own probe design.
Synthesis and characterization of novel compounds
Reaction of 1-dicyanomethylene-2,3-dichloroindene5 1 with dif-
ferent secondary amines in dichloromethane at room tempera-
ture gave the 1-dicyanomethylene-2-chloro-3-aminoindene chro-
mophores 2–9 in good yields (Scheme 1). Nucleophilic substitution
of the chlorine atom in position 3 is selective and the reaction
occurred with a wide range of amines. The presence of donor
amino and acceptor dicyanomethylene groups in these molecules
resulted in an intramolecular charge transfer band responsible
for their intense deep purple colour. Thus the UV/vis spectra
of these compounds showed an intense band centred around
In this work we describe an easy entry to a family of push–
pull chromophores based on 3-amino-1-dicyanomethyleneindene
moieties. These compounds are readily obtained by amination
reactions and they probed to be useful sensors for the detection
of cationic and anionic species. In a previous communication,
we have used this strategy to decorate a mesoporous solid with
this type of signalling unit, giving rise to a sensor of primary
amines.4
aDepartamento de Qu´ımica, Facultad de Ciencias, Universidad de Burgos,
Plaza Misael Ban˜uelos s/n, 09001, Burgos, Spain. E-mail: ttorroba@ubu.es;
Fax: +34 947 258831; Tel: +34 947 258088
bDepartamento de Qu´ımica F´ısica y Qu´ımica Inorga´nica, Facultad de
Ciencias, Universidad de Valladolid, 47011, Valladolid, Spain. E-mail:
dmsj@qi.uva.es; Fax: +34 983 423234; Tel: +34 983 184096
cDepartamento de Qu´ımica Orga´nica, Facultad de Veterinaria, Universidad
de Extremadura, Avenida de la Universidad s/n, 10071, Ca´ceres, Spain.
E-mail: aneo@unex.es; Fax: +34 927 257110; Tel: +34 927 257158
† Electronic supplementary information (ESI) available: NMR spectra of
1
2–10, UV-vis, H NMR and MS titration experiments. CCDC reference
numbers 744017. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/b916700e
Scheme 1 Synthesis of compounds 2–9.
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Table 1 Association constants (log Ka) for receptors 2, 4 and 9 with
different cations (added as their triflate or perchlorate salts) at 298 K in
MeCN as determined by UV-vis titration techniques
550 nm. Compounds 2–9 were obtained as deep purple solids
and spectroscopically characterized. The structure of compound
3 was further confirmed by X-ray diffraction. Two different views
of the structure are shown in Fig. 1. The structural features of
the molecule showed the conjugation of the dicyanomethylene
and the diethylamine groups of the chromophore. Thus, the
dicyanomethylene indene moiety is coplanar with the aromatic
system and the nitrogen atom showed sp2 hybridization with angles
around the amine nitrogen atom close to 120◦. The bond distance
2
4
9
Al3+
Cu2+
Fe3+
Hg2+
4.47 0.03
5.17 0.06
5.56 0.09
—
—
—
5.93 0.23
—
—
5.70 0.08
—
3.67 0.14a
6.36 0.18a
Sc3+
Sn2+
3.96 0.67
4.54 0.11
—
—
—
—
˚
between this atom and the indene carbon is 1.343 A and the
dihedral angle of the amine and the pseudoaromatic system is
40.3◦.
a The titration profile fits a sequential 1 : 1+1 : 1 complexation process.
Fig. 1 Two different views of the crystal structure of compound 3.
Cation sensing
Since the strong colour displayed by compounds 2–9 is the result
of an intramolecular charge transfer band from the amine to the
dicyanomethyleneindene moieties we reasoned that coordination
of the amine to a metal centre would impact the conjugation of
the molecule resulting in a change of colour.
We first investigated the diethylamino derivative 2. Addition of 1
equivalent of different cations added as their triflate or perchlorate
salts to a 10-4 M solution of 2 in acetonitrile resulted in a change
of colour in the presence of Sc3+, Sn2+, Al3+, and especially Fe3+
and Cu2+ (Fig. 2 top).
Fig. 3 UV-vis spectral changes of receptor 2 (10-4 M) upon addition of
increasing amounts of Cu2+ (0 → 10 equiv.) in acetonitrile. Inset: titration
profile of the observed changes at l = 550 nm.
From all these experiments it is clear that compound 2 is able to
interact with different cations, signalling this event by a dramatic
change of colour. The lack of selectivity showed by this compound
can be explained in terms of the simplicity of the binding unit.
Therefore, the presence of more elaborate binding units with
additional coordination sites could improve the selectivity of the
probe. We next investigated the response of compound 4, bearing
two allyl groups, towards the same set of cations in acetonitrile
solution, as it was expected that the allyl groups could participate
in the coordination of the metal (Fig. 2 bottom). In this case,
a selective bleaching of the solution was observed only in the
presence of Cu2+ (perchlorate salt). Similar changes in the UV/vis
spectra to those described for compound 2 were observed, with
disappearance of the band centred at 539 nm upon addition of the
metal (Fig. 4).
An isosbestic point appeared at approximately 255 nm and
the changes of the absorbance at 539 nm fitted to a 1 : 1 model.
Association constants are shown in Table 1. Job’s plot analysis of
the UV-Vis titration of 4 and Cu2+, carried out in MeCN, revealed a
maximum at a 50% mole fraction, in accordance with the proposed
Fig. 2 Colour changes of receptors 2 (top row) and 4 (bottom row)
(10-4 M in acetonitrile) upon addition of 1 equiv. of different cations.
From left to right: none, Zn2+, Cd2+, Sc3+, Ag+, Hg2+, Sn2+, Ni2+, Pb2+, Al3+
,
Fe3+, Cu2+
.
The UV/vis spectrum of this compound showed an intense band
with a maximum at l = 550 nm (e = 10 324 M-1 cm-1). Addition
of increasing amounts of these cations resulted in the quenching
of this band accounting for the bleaching observed in the
presence of some of the cations (Fig. 3). An isosbestic point
appeared at approximately 343 nm and the changes of the
absorbance at 550 nm fitted to a 1 : 1 model. Apparent association
constants are included in Table 1.
1 : 1 binding stoichiometry (Fig. 5). The detection limit of 4 (10-4
M
in MeCN), calculated by the blank variability method,6 was 9.46 ¥
10-8 M.
We then studied the macrocyclic derivatives 6–9. Compounds
6–7 did not show immediate colour changes in the presence of
the usual cations, showing partial decolourisation after 20 min in
the presence of Sc3+, Sn2+, Al3+, Fe3+ and Cu2+ and compound
8 showed only partial decolourisation in the presence of Pb2+
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1 : 1 ML binding model with log Ka = 5.70 0.08 (Table 1). In the
case of Hg2+ the changes in the UV-vis were best described as a
sequential 1 : 1 + 1 : 1 process with log Ka1 = 3.67 0.14 and log
Ka2 = 6.36 0.18 (Table 1).
Job’s plot analysis of the UV-Vis titration of 9 and Cu2+, carried
out in MeCN, also revealed a maximum at a 50% mole fraction,
thus confirming the 1 : 1 binding mode (see ESI†). But the Job’s
plot analysis of the UV-Vis titration of 9 and Hg2+, carried out in
MeCN, revealed a maximum at a 40% mole fraction, confirming
in this case the proposed 2 : 1 binding stoichiometry (Fig. 7).
Fig. 4 UV-vis absorption spectrophotometric titration of compound 4
(10-4 M) with increasing amounts of Cu2+ (0 → 5 equiv.) in acetonitrile.
Inset: variation of absorbance at l = 539 nm vs. concentration of metal.
Fig. 7 Job’s plot analysis of 9 (10-4 M in MeCN) with Hg2+
.
The sensing action of 4 and Cu2+ was equally effective in a
mixture of a 10-4 M solution of 5 and 2 equiv. of every cation:
Zn2+, Cd2+, Sc3+, Ag+, Hg2+, Sn2+, Ni2+, Pb2+, Al3+ and Fe3+ in
MeCN, without losing sensitivity to Cu2+ (Fig. 8).
Fig. 5 Job’s plot analysis of 4 (10-4 M in MeCN) with Cu2+
.
Fig. 8 (a) A solution of 4 (10-4 M in MeCN). (b) Addition of 2 equiv. of
every cation: Zn2+, Cd2+, Sc3+, Ag+, Hg2+, Sn2+, Ni2+, Pb2+, Al3+, Fe3+ to
solution (a). (c) Addition of 2 equiv. of Cu2+ to solution (b).
In addition, a 10-4 M solution of 4 that lost the colour in the
-
presence of 4 equiv. of Cu2+ (ClO4 )2, recovered the colour in the
presence of 2 equiv. of 3,6-dioxa-1,8-octanedithiole, thus proving
the reversibility of the detection (see ESI†).
Anion sensing
Cyanide is one of the most toxic anions yet is widely used
industrially.7 Therefore, development of cyanide receptors and
sensors is an area of interest.8 Among the various strategies used to
produce these probes, those relying on the nucleophilicity of this
anion have proven successful.9 Since our system could undergo
nucleophilic additions we decided to explore the interactions of the
diethylamino derivative 2 with anions. Addition of 10 equivalents
of different anions added as their tetrabutylammonium salts to a
10-4 M solution of 2 in acetonitrile resulted in a selective bleaching
of the solution in the presence of CN- (Fig. 9). The same behaviour
was observed for the rest of compounds 3–9.
Fig. 6 UV-vis absorption spectrophotometric titration of compound 9
(10-4 M) with increasing amounts of Cu2+ (0 → 2 equiv.) in acetonitrile.
Inset: variation of absorbance at l = 550 nm vs. concentration of metal
cation.
and Fe3+. Instead compound 9 underwent colour changes in the
presence of Hg2+ (decolourisation) and Cu2+ (purple to yellow).† A
UV/vis titration experiment with increasing amounts of copper(II)
perchlorate is shown in Fig. 6. Decreasing of the band centred at
l = 550 nm and appearance of a new band at 478 nm was observed,
with isosbestic points at 498 and 343 nm. These changes fitted a
UV-Vis spectra reflected these changes with the disappearance
of the absorbance in the 550 nm region and appearance of
isosbestic points at ca. 390, 291 and 252 nm for compound 2
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Fig. 9 Colour changes induced by the addition of 10 equiv. of different
anions to a solution of receptor 2 (10-4 M in acetonitrile). From left to
right: none, F-, Cl-, Br-, I-, BzO-, NO3-, H2PO4-, HSO4-, AcO-, CN-,
SCN-.
(Fig. 10). The changes in the absorbance as a function of the
concentration of anion added can be fitted to a 1 : 1 binding
equilibrium model, giving an association constant of log Ka
=
6.39 0.28. The detection limit of 2 (10-4 M in MeCN), calculated
by the blank variability method,6 was 1.01 ¥ 10-7 M.
Fig. 11 1H NMR (300 MHz) titration of chromophore 5 (13 mM) with
CN- in CD3CN. In red: signals disappearing. In blue: signals appearing
during titration.
Scheme 2 Proposed mechanism for the addition of cyanide to the indene
moiety.
cyanide anion to the indene ring would induce the formation
of a stereogenic carbon, therefore the methylene protons would
become diastereotopic and hence the signal pattern observed. This
mechanism is also supported by the fact that the parent 3-amino-
1-dicyanomethyleneindene compound 10, lacking the chlorine
atom in the 2 position, showed no changes in the presence of
cyanide. This result could be explained because of the attenuated
electrophilicity of the chromophore as the result of the lack of the
electron-withdrawing halogen atom.
Fig. 10 UV-vis spectral changes of receptor 2 (10-4 M) upon addition
of increasing amounts of TBACN (0 → 5 equiv.) in acetonitrile. Inset:
titration profile of the observed changes at l = 550 nm.
In order to shed light on the interaction of cyanide and receptor
2, NMR titration experiments were carried out. 1H NMR titration
of 2 with 1 equiv. CN- Bu4N+ in CDCl3 causes a large upfield shift
of the methylene group signals, from d 3.9 to 2.7, that become
diastereotopic (two sextets), indicating a close proximity to a
quaternary chiral centre. 13C NMR (and DEPT) titration of 2 and
CN- (1 equiv) show an adduct (see ESI†) having two equivalent
CN groups (a double intensity signal at d 126), a third CN group
at d 111, and two new quaternary carbon signals at d 72 and 26,
all of them corresponding most probably to the addition product
shown in Scheme 2.† The NMR changes by titration with cyanide
are even clearer by using the dibenzylamine derivative 5, which
undergoes similar colorimetric changes upon addition of cyanide.
This process is slow on the NMR time scale (Fig. 11). Addition of
cyanide resulted in the disappearance of the signals corresponding
to the receptor and the appearance of a new set of signals.
The biggest difference corresponded to the methylene protons
of the amine substituents which underwent an upfield shift of
approximately 1.2 ppm whereas only minor changes are observed
for the aromatic protons. All these data suggest a nucleophilic
attack at the carbon 3 as the likely mechanism for the interaction
between 2 and cyanide (Scheme 2). Nucleophilic addition of
The sensing action of 2 and CN- was equally effective in a
mixture of a 10-4 M solution of 2 and 2 equiv. of every anion:
F-, Cl-, Br-, I-, BzO-, NO3 , H2PO4 , HSO4 , AcO- and SCN- in
MeCN, without losing sensitivity to CN- (Fig. 12).
-
-
-
Fig. 12 (a) A solution of 2 (10-4 M in MeCN). (b) Addition of 2 equiv.
of every anion: F-, Cl-, Br-, I-, BzO-, NO3-, H2PO4-, HSO4-, AcO- and
SCN- to solution (a). (c) Addition of 2 equiv. of CN- to solution (b).
A 10-4 M solution of 2 that lost the colour in the presence
of 4 equiv. of CN-Bu4N+, recovered the colour in the presence
-
of 4 equiv. of Ag+ClO4 . The low resolution EIMS spectrum of a
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mixture of 4 and 1 equiv. CN- showed only the peaks characteristic
of 4. Both experiments proved the reversibility of the detection (see
ESI†).
(t, J = 7.2 Hz, 6H, CH3) ppm. 13C NMR (CDCl3, 100 MHz)
d: 157.33, 157.22, 134.96, 134.30, 131.06, 130.53, 123.46, 122.72,
116.97 (CN), 115.41 (CN), 99.05, 62.45, 46.95 (CH2), 14.63 (CH3)
ppm. MS (EI) m/z (%): 285 (M+ + 2, 35), 284 (M+ + 1, 19), 283
∑
(M+ , 100), 268 (M+ - CH3, 66), 248 (M+ - Cl, 92), 240 (58), 227
Conclusions
(85), 220 (50), 177 (49), 176 (47). HRMS: Calc. for C16H14N3Cl:
283.0876, found: 283.0864. UV-Vis (2.5 ¥ 10-5 M, CH3CN), l:
538 nm (e = 9845 M-1 cm-1), 337 nm (e = 12 071 M-1 cm-1), 237 nm
(emax = 15 490 M-1 cm-1).
Amination of 1-dicyanomethylene-2,3-dichloroindene provides
straightforward access to a family of push–pull chromophores.
One of these compounds is a selective copper(II) colorimetric
probe in acetonitrile solution, displaying a dramatic colour change
upon coordination of the amine group to the metal centre. The
selectivity of the probe for Cu2+ depends on the basicity of the
amine nitrogen and the interaction of the lateral groups. It is
improved by the presence of the diallylamine group but is worse
when dialkylamine or azacrown ether groups are present. Those
compounds are also selective cyanide dosimeters under similar
conditions, through the nucleophilic addition of the anion to the
indene moiety. The simplicity and versatility of the design could
offer opportunities for improved designs. Efforts to develop fluoro-
chromogenic probes based on this fragment are currently under
way in our laboratory.
1-Dicyanomethylene-2-chloro-3-(N,N -diisobutylamino)indene
(3). The procedure was similar to that described above using
a solution of 1 (27 mg, 0.109 mmol) in 5 mL of CH2Cl2
and diisobutylamine (0.25 mL, r = 0.740 g mL-1, 1.43 mmol)
at room temperature and the mixture was stirred for 30 min.
Chromatographic work up of the reaction crude (silica gel, 1.5 ¥
25 cm, elution with hexane–CH2Cl2 6 : 4) yielded 3 as a purple
solid. Yield 24 mg (65%). Mp: 163–164 ◦C. IR (KBr, cm-1): 2955,
2924, 2202 (CN), 1515, 1441, 1091. 1H NMR (CDCl3, 400 MHz)
=
=
d: 8.25 (m, 1H, CH ), 7.35 (m, 3H, CH ), 3.58 (d, J = 7.5 Hz,
4H, CH2), 2.06 (m, 2H, CH), 0.91 (d, J = 6.7 Hz, 12H, CH3) ppm.
13C NMR (CDCl3, 100 MHz) d: 157.88, 135.48, 134.21, 131.20,
130.06, 123.61, 122.24, 116.08 (CN), 114.49 (CN), 102.88, 65.26,
Experimental
60.43 (CH2N), 27.72 (CH), 19.75 (CH3) ppm. MS (EI) m/z (%):
∑
341 (M+ + 2, 32), 340 (M+ + 1, 26), 339 (M+ , 87), 304 (M+
-
Materials and instrumentation
Cl, 15), 296 (54), 283 (27), 240 (100), 177 (12). HRMS: Calc.
The reactions performed with air sensitive reagents were con-
ducted under dry nitrogen. The solvents were previously dis-
tilled under nitrogen over calcium hydride or sodium filaments.
Commercial reagents were used as received. 1-Dicyano-2,3-
dichloroindene was synthesized as previously reported.2 Melting
points were determined in a Gallenkamp apparatus and are not
corrected. Infrared spectra were registered in a Nicolet Impact
410 spectrometer in potassium bromide tablets. NMR spectra
were recorded in Varian Mercury-300 and Varian Unity Inova-
400 machines, in DMSO-d6, CDCl3, CD3CN, CD3OD. Chemical
shifts are reported in ppm with respect to residual solvent protons,
coupling constants (JX-X¢) are reported in Hz. Elemental analyses
of C, H and N were taken in a Leco CHNS-932. Mass spectra were
taken in a Micromass AutoSpec machine, by electronic impact at
70 eV. Quantitative UV-visible measurements were performed with
a Varian, Cary 300 Bio UV spectrophotometer, in 1 cm UV cells
at 25 ◦C.
for C20H22N3Cl: 339.1502, found: 339.1487. Crystal data for 3,
¯
˚
C20H22ClN3, M = 339.86, triclinic, P1, a = 8.3304(16) A, b =
◦
◦
˚
˚
˚
9.1897(18) A, c = 13.096(3) A, a = 92.955(4) , b = 97.382(4) ,
◦
3
-1
g = 108.536(4) ; V = 938.1(3) A , Z = 2, Dc = 1.203 g cm , m(Mo-
Ka) = 0.209 mm-1. Purple-black prism, (0.31 ¥ 0.13 ¥ 0.09) mm3.
4227 measured reflections, 2673 independent (Rint = 0.0248), 1797
observed (I > 2s(I)). R1 = 0.0873, wR2 =0.1890 (all data).†
1-Dicyanomethylene-2-chloro-3-(N,N-diallylamino)indene (4).
The procedure was similar to that described above using a solution
of 1 (30 mg, 0.122 mmol) in 5 mL of CH2Cl2 and diallylamine
(0.1 mL, r = 0.787 g mL-1, 0.811 mmol) at room temperature
and the mixture was stirred for 15 min. Chromatographic work up
of the reaction crude (silica gel, 3 ¥ 20 cm, elution with hexane–
CH2Cl2 7 : 3) gave 4 as a purple solid. Yield 36 mg (97%). Mp:
◦
117–118 C. IR (KBr, cm-1): 2924, 2205 (CN), 1522, 1448, 1417,
1
=
1336, 1293. H NMR (CDCl3, 400 MHz) d: 8.19 (m, 1H, CH ),
=
=
=
7.41 (m, 1H, CH ), 7.30 (m, 2H, CH ), 5.98 (m, 2H, CH ),
1
2
=
5.44 (d, J = 10.4 Hz, 2H, CH2 ), 5.33 (d, J = 17.2 Hz, 2H,
Syntheses and characterization
1
2
CH2 ), 4.38 (d, J = 5.2 Hz, 4H, CH2N) ppm. 13C NMR (CDCl3,
=
1-Dicyanomethylene-2-chloro-3-(N,N-diethylamino)indene (2).
Diethylamine (0.25 mL, r = 0.707 g mL-1, 2.421 mmol) was added
to a solution of 1 (50 mg, 0.202 mmol) in CH2Cl2 (15 mL) at
room temperature and the mixture stirred for 30 min. Then the
reaction mixture was poured into a chilled solution of HCl in
water (50 mL HCl, 10% w/v, and 100 g ice). The aqueous phase
was extracted with dichloromethane (3 ¥ 30 mL). The combined
organic extracts were dried (Na2SO4) and the solvent evaporated.
The residue was purified by flash chromatography (silica gel, 1.5 ¥
30cm), fromhexane–CH2Cl2 7 : 3 to 1 : 1, obtaining compound 2 as
a purple solid. Yield 56 mg (98%). Mp 150–151 ◦C. IR (KBr, cm-1):
2202 (CN), 1600, 1588, 1511, 1483, 1476, 1452. 1H NMR (CDCl3,
100 MHz) d: 157.75, 157.42, 134.31, 134.16, 131.98 (CH), 131.16
=
(CH), 130.35 (CH), 123.43 (CH), 122.63 (CH), 120.13 (CH2 ),
116.29 (CN), 114.68 (CN), 102.18, 99.67, 64.15, 53.53 (CH2N)
∑
ppm. MS (EI) m/z (%): 309 (M+ + 2, 8), 307 (M+ , 22), 272
(M+ - Cl, 100), 230 (44), 176 (19). HRMS: Calc. for C18H14N3Cl:
307.0876, found: 307.0854. UV-Vis (10-4 M, CH3CN) l: 539 nm
(e = 9139 M-1 cm-1), 342 nm (e = 13 078 M-1 cm-1), 237 nm (emax
=
18 363 M-1 cm-1).
1-Dicyanomethylene-2-chloro-3-(N,N-dibenzylamino)indene (5).
The procedure was similar to that described above using a solution
of 1 (30 mg, 0.121 mmol) in 10 mL of CH2Cl2 and dibenzylamine
(0.50 mL, r = 1.026 g mL-1, 2.604 mmol) at room temperature
and the mixture was stirred for 60 min. Chromatographic work up
=
400 MHz) d: 8.18 (d, J = 7.4 Hz, 1H, CH ), 7.39 (d, J = 7.3 Hz,
1H, CH ), 7.31 (m, 2H, CH ), 3.91 (c, J = 7.2 Hz, 4H, CH2), 1.44
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of the reaction crude (silica gel, 3 ¥ 25 cm, elution with hexane–
CH2Cl2 4 : 6) yielded 5 as a purple solid. Yield 31 mg (63%). Mp:
1-Dicyanomethylene-2-chloro-3-(4,7,10,13,16-pentaoxa-1-aza-
cyclooctadec-1-yl)indene (8). The procedure was similar to
that described above using a solution of 1 (30 mg,
◦
178–179 C. IR (KBr, cm-1): 3021, 2916, 2850, 2214 (CN), 1604,
1
1522, 1441, 1355. H NMR (CDCl3, 400 MHz) d: 8.30 (d, J =
0.121 mmol) in 10 mL of CH2Cl2 and 1,4,7,10,13-pentaoxa-16-
azacyclooctadecane (79 mg, 0.303 mmol) at room temperature
and the mixture was stirred for 60 min. Chromatographic work up
of the reaction crude (silica gel, 1.5 ¥ 30 cm, elution with CH2Cl2
to AcOEt, then AcOEt–MeOH 3 : 1) yielded 8 as a purple solid.
=
=
=
8 Hz, 1H, CH ), 7.33 (m, 9H, CH ), 7.19 (m, 4H, CH ), 4.92 (s,
4H, CH2N) ppm. 13C NMR (CDCl3, 100 MHz) d: 158.60, 157.79,
135.16, 134.91, 134.01, 131.40, 130.35, 129.09, 128.23, 127.35,
123.81, 122.43, 115.96 (CN), 114.29 (CN), 101.65, 66.11, 54.81
(CH2N) ppm. MS (FAB+) m/z (%): 410 (M+ + 3, 10), 409 ((M+ +
◦
Yield 52 mg (90%). Mp: 84–85 C. IR (KBr, cm-1): 2908, 2870,
∑
2, 7), 408 (M+ + 1, 23), 407 (M+ , 11), 372 (M+ - Cl, 3), 309
2206 (CN), 1600, 1584, 1515, 1445, 1336, 1126. 1H NMR (CDCl3,
=
=
(11), 278 (14), 263 (10), 231 (43), 197 (10), 154 (71), 139 (12), 137
(100), 109 (30), 105 (12). HRMS: Calc. for C26H18ClN3: 407.1189,
found: 407.1196. UV-Vis (2.5 ¥ 10-5 M, CH2Cl2), l: 535 nm (e =
9666 M-1 cm-1), 347 nm (e = 15 134 M-1 cm-1), 301 nm (e =
10 112 M-1 cm-1), 237 nm (emax = 18 699 M-1 cm-1).
400 MHz) d: 8.23 (m, 1H, CH ), 7.55 (m, 1H, CH ), 7.30 (m,
2H, CH ), 4.19 (t, J = 5.3 Hz, 4H, CH2), 3.91 (t, J = 5.3 Hz,
=
4H, CH2), 3.65 (m, 16H, CH2) ppm. 13C NMR (CDCl3, 100 MHz)
d: 158.36, 157.76, 134.86, 134.61, 131.42, 130.47, 123.60, 123.50,
116.76 (CN), 115.19 (CN), 100.31, 96.95, 70.92 (CH2), 70.85
(CH2), 70.78 (CH2), 70.36 (CH2), 53.27 (CH2) ppm. MS (EI) m/z
∑
(%):475 (M+ + 2, 9), 473 (M+ , 24), 438 (M - Cl, 16), 298 (44),
1-Dicyanomethylene-2-chloro-3-(4,7,10-trioxa-1-azacyclododec-
1-yl)indene (6). The procedure was similar to that described
262 (38), 254 (41), 239 (100), 225 (35), 211 (20), 204 (26), 176
(24). HRMS: Calc. for C24H28ClN3O5: 473.1717, found: 473.1710.
UV-Vis (2.5 ¥ 10-5 M, CH3CN), l: 538 nm (e = 10 023 M-1 cm-1),
348 nm (e = 13 377 M-1 cm-1), 233 nm (emax = 18 624 M-1 cm-1).
above using
a solution of 1 (40 mg, 0.162 mmol) in
15 mL of CH2Cl2 and 1,4,7-trioxa-10-azacyclododecane (70 mg,
0.400 mmol) at room temperature and the mixture was stirred for
30 min. Chromatographic work up of the reaction crude (silica
gel, 1.5 ¥ 30 cm, elution with CH2Cl2 to CH2Cl2–AcOEt 3 : 1)
yielded 6 as a purple solid. Yield 58 mg (94%). Mp: 141–142 ◦C.
IR (KBr, cm-1): 2928, 2858, 2202 (CN), 2189 (CN), 1599, 1525,
1479, 1444, 1157, 1090. 1H NMR (CDCl3, 400 MHz) d: 8.25 (m,
1-Dicyanomethylene-2-chloro-3-(1-aza-7,10-dioxa-4,13-dithia-
cyclopentadecyl)indene (9). The procedure was similar to that
described above using a solution of 1 (40 mg, 0.16 mmol) in 20 mL
of CH2Cl2 and 10-aza-1,4-dioxa-7,13-dithiacyclopentadecane10
(122 mg, 0.49 mmol, in 15 mL of CH2Cl2) at room temperature
and the mixture was stirred for 15 min. Chromatographic work up
of the reaction crude (silica gel, 3 ¥ 20 cm, elution with CH2Cl2 to
ethyl acetate–CH2Cl2 1 : 5) yielded 6 as a purple solid. Yield 79 mg
=
=
=
1H, CH ), 7.77 (m, 1H, CH ), 7.31 (m, 2H, CH ), 4.18 (t, J =
4.9 Hz, 4H, CH2), 3.96 (t, J = 4.9 Hz, 4H, CH2), 3.66 (m, 8H,
CH2) ppm. 13C NMR (CDCl3, 100 MHz) d: 157.59, 157.02, 134.54,
134.29, 131.14, 130.21, 123.55, 123.32, 116.48 (CN), 114.90 (CN),
99.64, 70.99 (CH2), 70.93 (CH2), 70.02 (CH2), 53.35 (CH2) ppm.
◦
(98%). Mp: 194–196 C. IR (KBr, cm-1): 2961, 2923, 2855, 2205
(CN), 1514, 1456, 1446, 1350, 1100. 1H NMR (CDCl3, 400 MHz)
∑
MS (EI) m/z (%): 387 (M+ + 2, 14), 386 (M+ + 1, 12), 385 (M+ ,
d: 8.27 (m, 1H, CH ), 7.36-7.32 (m, 3H, CH ), 4.14 (m, 4H,
CH2N), 3.81 (m, 4H, CH2O), 3.66 (m, 4H, CH2O), 3.06 (m, 4H,
CH2S), 2.76 (m, 4H, CH2S) ppm. 13C NMR (CDCl3, 100 MHz)
d: 157.23, 156.34, 134.36, 134.33, 131.34, 130.30, 123.57, 122.56,
116.38 (CN), 114.77 (CN), 99.99, 77.20, 74.43 (CH2O), 70.55
(CH2O), 64.36, 53.92 (CH2N), 31.66 (CH2S), 31.56 (CH2S) ppm.
=
=
40), 350 (M - Cl, 11), 298 (12), 262 (35), 248 (29), 239 (100), 225
(24), 190 (8), 176 (22). HRMS: Calc. for C20H20N3ClO3: 385.1193,
found: 385.1182. UV-Vis (2.5 ¥ 10-5 M, CH3CN), l: 533 nm (e =
10861 M-1 cm-1), 345 nm (e = 15053 M-1 cm-1), 233 nm (emax
=
21285 M-1 cm-1).
∑
MS (IE) m/z (%): 461 (M+ , 1), 426 (M+ - Cl, 29), 360 (17),
301 (14), 242 (24), 211 (16), 184 (23), 142 (71), 123 (16), 103
(26), 87 (31), 75 (26), 60 (100) HRMS: Calc. for C22H24N3O2S2Cl:
461.0998, found: 461.0984. UV-Vis (10-4 M, CH3CN), l: 549 nm
1-Dicyanomethylene-2-chloro-3-(4,7,10,13-tetraoxa-1-azacyclo-
pentadec-1-yl)indene (7). The procedure was similar to that
described above using a solution of 1 (40 mg, 0.162 mmol) in 20 mL
of CH2Cl2 and 1,4,7,10-tetraoxa-13-azacyclopentadecane (88 mg,
0.402 mmol) at room temperature and the mixture was stirred for
60 min. Chromatographic work up of the reaction crude (silica gel,
1.5 ¥ 25 cm, elution with CH2Cl2 to AcOEt) yielded 7 as a purple
solid. Yield 69 mg (99%). Mp: 193–194 ◦C. IR (KBr, cm-1): 2889,
(e = 9092 M-1 cm-1), 362 nm (e = 12 026 M-1 cm-1), 240 nm (emax
=
17 463 M-1 cm-1).
1-Dicyanomethylene-3-(N,N-diethylamino)indene (10). PdCl2-
(dppf) (5 mg, 0.004 mmol) was added with continuous stirring to
a solution of 2 (30 mg, 0.106 mmol) in dry THF (15 mL) at room
temperature under a nitrogen atmosphere and stirred for 30 min.
Then TMEDA (0.21 mL, r = 0.770 g mL-1, 1.420 mmol) was
1
2865, 2206 (CN), 2193, 1509, 1471, 1441, 1343, 1126. H NMR
=
=
(CDCl3, 400 MHz) d: 8.25 (m, 1H, CH ), 7.53 (m, 1H, CH ), 7.32
(m, 2H, CH ), 4.13 (t, J = 6.0 Hz, 4H, CH2), 3.93 (t, J = 6.0 Hz,
◦
=
added and the reaction mixture cooled to 0 C with an ice bath.
4H, CH2), 3.65 (m, 12H, CH2) ppm. 13C NMR (CDCl3, 100 MHz)
d: 157.36, 157.19, 134.45, 134.40, 131.19, 130.25, 123.38, 123.12,
116.50 (CN), 114.93 (CN), 99.41, 71.08 (CH2), 70.52 (CH2), 70.05
(CH2), 69.79 (CH2), 63.12, 54.46 (CH2) ppm. MS (EI) m/z (%):
To this mixture NaBH4 (20 mg, 0.530 mmol) suspended in THF
(5 mL) was added dropwise and the mixture stirred for 2 h. Then
the reaction mixture was poured into a chilled solution of HCl in
water (50 mL HCl, 10% w/v, and 100 g ice). The aqueous phase
was extracted with dichloromethane (3 ¥ 50 mL). The combined
organic extracts were dried (Na2SO4) and the solvent evaporated.
The residue was purified by flash chromatography (silica gel, 3 ¥
15 cm), from hexane–CH2Cl2 7 : 3 to 1 : 4, obtaining compound 2
as a pink solid. Yield 8 mg (30%). Mp: 108–110 ◦C. IR (KBr, cm-1):
∑
429 (M+ , 2), 254 (39), 240 (56), 239 (100), 238 (75), 225 (36),
211 (12), 176 (16). HRMS: Calc. for C22H24N3ClO4: 429.1455,
found: 429.1453. UV-Vis (2.5 ¥ 10-5 M, CH3CN), l: 538 nm (e =
8303 M-1 cm-1), 345 nm (e = 11 355 M-1 cm-1), 302 nm (e =
8723 M-1cm-1), 234 nm (emax = 16 532 M-1cm-1).
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1
2920, 2197 (CN), 1603, 1591, 1527, 1465, 1434, 1230. H NMR
3 For recent examples see: (a) R. Nishiyabu and P. Anzenbacher Jr.,
J. Am. Chem. Soc., 2005, 127, 8270; (b) H. D. P. Ali, P. E. Kruger and
T. Gunnlaugsson, New J. Chem., 2008, 32, 1153; (c) T. Gunnlaugsson,
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M. M. M. Raposo, Org. Lett., 2007, 9, 3201; (i) E. Ballesteros, D.
Moreno, T. Go´mez, T. Rodriguez, J. Rojo, M. Garc´ıa-Valverde and T.
Torroba, Org. Lett., 2009, 11, 1269.
=
=
(CDCl3, 400 MHz) d: 8.15 (m, 1H, CH ), 7.41 (m, 1H, CH ),
7.36-7.31 (m, 2H, CH ), 5.4 (s, 1H, CH ), 3.94-3.44 (m, 4H,
CH2), 1.41 (m, 6H, CH3) ppm. 13C NMR (CDCl3, 100 MHz)
d: 162.59, 161.34, 137.74, 135.18, 130.47 ( CH), 130.40 ( CH),
123.78 ( CH), 123.04 ( CH), 116.71 (CN), 116.68 (CN), 96.08
( CH), 58.32, 49.21–46.22 (m, CH2), 14.59–12.55 (m, CH3) ppm.
MS (EI) m/z (%): 249 (M+ , 23), 234 (16), 220 (26), 206 (44), 193
(17), 178 (6). Anal.: Calc. for C16H15N3. C: 77.08, H: 6.06, N: 16.85.
Found: C: 76.89, H, 5.93, N: 16.60%. UV-Vis (10-4 M, CH3CN) l:
574 nm (e = 5505 M-1 cm-1), 534 nm (e = 10 607 M-1 cm-1), 506 nm
(e = 10 230 M-1 cm-1), 324 nm (e = 9967 M-1 cm-1), 299 nm (e =
9819 M-1 cm-1), 232 nm (emax = 24 673 M-1 cm-1).
=
=
=
=
=
=
=
∑
4 S. Basurto, T. Torroba, M. Comes, R. Mart´ınez-Ma´n˜ez, F. Sanceno´n,
L. Villaescusa and P. Amoro´s, Org. Lett., 2005, 7, 5469.
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and Qualimetrics: Part A, Elsevier, Amsterdam, The Netherlands, 1997,
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Acknowledgements
We gratefully acknowledge financial support from the Ministerio
de Ciencia e Innovacio´n of Spain (Project CTQ2009-12631-BQU),
Junta de Castilla y Leo´n, Consejer´ıa de Educacio´n y Cultura, y
Fondo Social Europeo (Projects BU023A09 and GR170). R. Q.
thanks the Ministerio de Ciencia e Innovacio´n of Spain for a
Ramo´n y Cajal contract.
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¨
558 | Org. Biomol. Chem., 2010, 8, 552–558
This journal is
The Royal Society of Chemistry 2010
©