N-Arylated pyridinium salts having reactive groups

Article abstract of DOI:10.1016/j.tetlet.2007.09.009

The pyridinium salts having reactive amine and/or pyridyl groups were obtained by the reaction using Zincke salts. Optical properties and anion exchange behavior of the obtained pyridinium salts were investigated.

Full text of DOI:10.1016/j.tetlet.2007.09.009

Tetrahedron Letters 48 (2007) 7778–7781
N-Arylated pyridinium salts having reactive groups
*
Isao Yamaguchi, Hideo Higashi, Sachiko Shigesue, Saki Shingai and Moriyuki Sato
Department of Material Science, Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu,
Matsue 690-8504, Japan
Received 2 August 2007; revised 31 August 2007; accepted 4 September 2007
Available online 6 September 2007
Abstract—The pyridinium salts having reactive amine and/or pyridyl groups were obtained by the reaction using Zincke salts.
Optical properties and anion exchange behavior of the obtained pyridinium salts were investigated.
Ó 2007 Elsevier Ltd. All rights reserved.
Pyridinium salts are an important class of compounds
organic syntheses in water, except for simple hydrolysis
reactions, are limited due to the poor solubility of
organic reactants in water. The Zincke salts and certain
amines used as starting materials in this work are solu-
ble in water. These situations urged us to carry out the
reaction of Zincke salts with amines in water.
1
that are used as initiators of cationic polymerization,
2
3
cationic surfactants, non-linear optical materials, and
4
phase transfer catalysts. Among the several synthetic
approaches to obtain pyridinium salts, Zincke’s reaction
is a versatile method. The reaction of Zincke salts, a
highly electrophilic species formed by reaction between
a pyridine derivative and 1-chloro-2,4-dinitrobenzene,
with primary amines has been employed for the synthe-
Herein, we report the synthesis of Zincke salts having a
phenyl, pyridyl, 9-anthryl, or 9-anthrylvinylene group
on the pyridine ring and their reactions with amines or
diamines (2) in EtOH and water to afford pyridinium
salts (3). Optical properties and anion exchange of the
obtained pyridinium salts are also reported. To our best
knowledge, there has been no report on investigation of
anion exchange behavior of pyridinium salt by electric
conductivity measurement so far.
5
sis of various pyridinium salts. Synthesis of N-aryl-
pyridinium salts from the Zincke salt was for the first
5
f–h
time reported by Marvell and Ise.
Recently, pyridin-
5
a
ium salts containing a chiral alkyl group and electron
donor and acceptor groups for nonlinear optical
materials have been synthesized. For the Zincke’s
reaction, use of Zincke salts with a functional group
on the pyridine ring and diamine instead of amine will
yield pyridinium salts having functional and reactive
3
b
The Zincke salts, N-(2,4-dinitrophenyl)-4-arylpyridi-
nium chlorides (aryl (Ar) = phenyl; 1a, 4-pyridyl; 1b,
NH groups. The reactive pyridinium salts could be used
2
7
8
as a starting species for functional materials such as
dyes, nonlinear optical polymers, and polymer catalysts.
However, reports on such reactive pyridinium salts are
9-anthryl; 1c, and 9-anthrylvinylene; 1d ), were
obtained by reaction of 1-chloro-2,4-dinitrobenzene
with the corresponding pyridine derivatives in 70, 85,
5
a
9
limited.
63, and 91% yields, respectively (Scheme 1).
Organic reactions in aqueous media have received con-
siderable attention because of their potential advantages
with regard to costs, safety, and environmental con-
cerns. In contrast to many reports on the organic reac-
tions in the mixtures of water and organic solvents,
The pyridinium salts (3) were obtained by the reaction
of 1 with 2 in refluxing EtOH, as shown in Scheme
2. The reaction of water-soluble pyridinium salts 1a
and 1b with the water-soluble amines 2a and 2b in
refluxing water also yielded the pyridinium salts (3).
1
0
6
The results of these reactions are summarized in Table 1.
The reactions in both EtOH and water gave the pyridi-
nium salts in moderate to high yields. The yields are
independent of the amine substituent(s). On the other
hand, the reactions of 1a with 4-nitroaniline and with
Keywords: Pyridinium salts; Pyridines; Reactive group; Zincke’s
reaction.
*
Corresponding author. Tel./fax: +81 852326421; e-mail: iyamaguchi@
riko.shimane-u.ac.jp
0040-4039/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.09.009

I. Yamaguchi et al. / Tetrahedron Letters 48 (2007) 7778–7781
7779
O2N
N + Cl
O2N
acetone
reflux for 12 h
Ar
NO2
Ar
N
-
NO2
N; 1b,
Cl
H
Ar =
; 1a,
; 1c, C C
; 1d
H
Scheme 1. Synthesis of N-(2,4-dinitrophenyl)-4-arylpyridinium chlorides (1).
O N
2
O N
2
EtOH or H O
2
Ar
N
-
NO2
+
NH2 Ar'
Ar
N
Ar' + H N
NO2
2
-
Cl
Cl
2
3
Scheme 2. Synthesis of pyridinium salts (3) using Zincke’s reaction.
Table 1. Synthesis of pyridinium salts by reaction of 1 with 2
O N
2
NH2 Ar' 2
Ar
N
-
NO2
Ar
N
-Ar'
Cl
Cl
1
3
0
Entry
1
Ar
2
Ar
Solvent
EtOH
H O
2
EtOH
3, Yield (%)
1
2
3
4
5
6
7
8
9
1a
C
6
H
5
2a
p-MeO–C
6
H
4
3a, 96
98
3b, 96
94
3c, 64
3d, 86
3e, 77
94
3f, 91
94
3g, 89
3h, 97
3i, 69
3j, 94
3k, 94
3l, 63
3m, 89
3n, 90
3o, 98
3p, 80
3q, 72
2b
p-F–C
6
H
4
2
H O
2d
2f
p-Br–C
4-NH -2,5-Me–C
p-MeO–C
6
H
4
EtOH
EtOH
EtOH
H O
2
EtOH
2
6
H
2
1b
C
5
H
4
N
2a
6 4
H
2b
p-F–C
6
H
4
10
11
12
13
14
15
16
17
18
19
20
21
2
H O
2c
2d
2e
2f
p-Cl–C
p-Br–C
p-I–C
4-NH
p-MeO–C
p-F–C
p-MeO–C
p-Br–C
6
H
4
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
6
H
4
6
H
4
2
-2,5-Me–C
6
H
2
1c
1d
9-Anthryl
9-Anthrylvinylene
2a
2b
2a
2d
2f
6
H
4
6
H
4
6
H
4
6
H
4
4-NH
p-NH
2,5-Me–C H
6 3
2
-2,5-Me–C
–C
6
H
2
2g
2h
2
6 4
H
4
-aminoacetophenone gave no pyridinium salts. A pos-
the amounts of AgClO4 after the equivalence point.
ꢀ
sible reason for this is that low basicity of the amines
prevents nucleophilic addition to the pyridinium ring
of 1a. The pyridinium salts 3 were soluble in water
and in organic solvents such as methanol, N,N-di-
methylformamide, and dimethyl sulfoxide. Their struc-
These results suggest that the Cl of 3a is exchanged
ꢀ
with ClO4 until the addition of an equimolar amount
of the silver salt. The decrease of the conductivities
seems to be ascribed to a smaller mobility of the pyri-
dinium perchlorate having a larger molecular size than
the pyridinium chloride.
1
13
tures were determined by
H
and
C
NMR
spectroscopy and elemental analysis.
The absorption positions of 3 are influenced by the struc-
tures of the substituents, as summarized in Table 2.
Pyridinium salts 3k–q give rise to characteristic absorp-
It has been reported that anions in aqueous solutions of
1
1
pyridinium salts influence their optical properties. To
investigate the behavior of anion exchange in aqueous
solutions of 3, electric conductivity measurements of
aqueous solutions of 3a were carried out when limited
*
*
tions due to p–p and n–p transitions of the anthryl
and anthrylvinylene groups at approximately 255 nm
and in the range of 283–475 nm, respectively. Among
the pyridinium salts having a phenyl or pyridyl group,
3a,d,e, and 3j with electron-donating substituent(s) show
peaks at longer wavelengths as compared to the other
pyridinium salts with an electron-accepting substituent.
These observations seem to be ascribed to the occurrence
amounts of AgClO were added to the solutions. During
4
the measurements, AgCl precipitated from the solutions.
As depicted in Figure 1, the conductivities of these solu-
tions decrease until the addition of an equimolar
amount of AgClO and then increase in proportion to
4

7780
I. Yamaguchi et al. / Tetrahedron Letters 48 (2007) 7778–7781
In conclusion, pyridinium salts having reactive amine
and/or pyridyl groups were obtained in moderate to
high yields by the Zincke’s reaction. The addition of
AgClO to aqueous solutions of these pyridinium salts
4
caused anion exchange reactions. The UV–vis measure-
ments suggest that intramolecular charge transfer
occurred in the pyridinium salts having electron-
donating group(s) on N-phenyl ring.
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tetlet.
2
007.09.009.
Figure 1. Conductivity changes of aqueous solutions of 3a (0.01 mM,
0 mL) by addition of AgClO in amounts of every 0.07 mmol.
7
4
References and notes
. (a) Takahashi, E.; Sanda, F.; Endo, T. J. Polym. Sci., Part
A: Polym. Chem. 2002, 40, 1037–1046; (b) Onciu, M.;
Onen, A.; Yagci, Y. Polym. Int. 2001, 50, 144–147; (c)
Schnabel, W. Macromol. Rapid Commun. 2000, 628–642.
2. (a) Mchedlov-Petrossyan, N. O.; Vodolazkaya, N. A.;
Kornienko, A. A.; Karyakina, E. L.; Reichardt, C.
Langmuir 2005, 21, 7090–7096; (b) Pernak, J.; Kalewska,
J.; Ksycin’ska, H.; Cybulski, J. Eur. J. Med. Chem. 2001,
36, 899–907.
3. (a) Umezawa, H.; Okada, S.; Oikawa, H.; Matsuda, H.;
Nakanishi, H. Bull. Chem. Soc. Jpn. 2005, 78, 344–348; (b)
Coe, B. J.; Harris, J. A.; Asselberghs, I.; Wostyn, K.;
Clays, K.; Persoons, A.; Brunschwig, B. S.; Coles, S. J.;
Gelbrich, T.; Light, M. E.; Hursthouse, M. B.; Nakatani,
K. Adv. Funct. Mater. 2002, 12, 110–116.
Table 2. UV–vis data of the pyridinium salts
1
a
ꢀ1
ꢀ1
)
Entry
3
Absorption, nm (loge, M cm
b
1
2
3
4
5
6
7
8
9
3a
3b
3c
3d
3e
3f
280 (3.60), 329 (3.78)
280 (4.52), 307 (4.50)
280 (4.49), 316 (4.51)
300 (4.31), 388 (3.37)
262 (4.68), 331 (4.48)
282 (4.40)
3g
3h
3i
275 (4.90)
282 (4.41)
271 (5.02)
1
1
0
1
3j
3k
254 (5.00), 365 (3.90)
251 (5.05), 320 (3.47), 345 (3.94),
82 (3.82), 410 (3.74)
258 (4.93), 351 (3.63), 368 (3.70),
3
12
3l
b
3
87 (3.69), 408 (3.56)
4. (a) Wang, D.; Wang, M.; Wang, X.; Zhang, R.; Ma, J.;
Sun, L. J. Mol. Catal. A: Chem. 2007, 270, 278–283; (b)
Dere, R. T.; Pal, R. R.; Patil, P. S.; Salunkhe, M. M.
Tetrahedron Lett. 2003, 44, 5351–5353.
5. (a) Viana, G. H. R.; Santos, I. C.; Alves, R. B.; Gil, L.;
Marazano, C.; Gil, R. P. F. Tetrahedron Lett. 2005, 46,
13
14
15
16
17
3m
3n
3o
3p
3q
254 (5.57), 286 (4.87), 464 (4.34)
254 (5.67), 302 (4.88), 475 (4.61)
253 (5.18), 283 (4.40), 453 (4.16)
254 (5.26), 274 (4.62), 451 (4.20)
254 (5.44), 289 (4.60), 462 (4.09)
7
773–7776; (b) Eda, M.; Kurth, M. J.; Nantz, M. H. J.
a
In EtOH.
Shoulder peak.
Org. Chem. 2000, 65, 5131–5135; (c) Urban, D.; Duval, E.;
Langlois, Y. Tetrahedron Lett. 2000, 41, 9251–9256; (d)
Gnecco, D.; Ju a´ rez, J.; Galindo, A.; Marazano, C.;
Enri’quez, R. G. Synth. Commun. 1999, 29, 281–287; (e)
Levillain, J.; Paquer, D.; Sene, A.; Vazeux, M. Synthesis
b
of an intramolecular charge transfer (CT) transition be-
tween the 4-methoxypheny or 4-amino-2,5-dimethylphe-
nyl and pyridinium groups.
1
998, 99–104; (f) Kunugi, S.; Okubo, T.; Ise, N. J. Am.
Chem. Soc. 1976, 98, 2282–2287; (g) Marvell, E. N.; Caple,
G.; Shahidi, I. J. Am. Chem. Soc. 1970, 92, 5641–5645; (h)
Marvell, E. N.; Shahidi, I. J. Am. Chem. Soc. 1970, 92,
A similar intramolecular CT transition has been
reported to give rise to CT absorption peaks in the
UV–vis spectrum of the pyridinium salt, 4-MeO–
C H –CH@CH–C H N ðPhÞPF .
5
646–5649.
. (a) Herrer ´ı as, C. I.; Yao, X.; Li, Z.; Li, C.-J. Chem. Rev.
007, 107, 2546–2562; (b) Dallinger, D.; Kappe, C. O.
Chem. Rev. 2007, 107, 2563–2591; (c) Li, C.-J. Chem. Rev.
005, 105, 3095–3165; (d) Lindstr o¨ m, U. M. Chem. Rev.
2002, 102, 2751–2772.
6
2
þ
ꢀ
6
3b
6
4
6
3
2
The pyridine derivatives 4-(9-anthryl)pyridine and 1-(9-
anthryl)-2-(4-pyridyl)ethylene were photoluminescent
(
7. The compound 1c was synthesized by Suzuki cross-
coupling of 9-bromoanthracene with 4-pyridineboronic
acid. See Supplementary data.
. The compound 1d was synthesized by Wittig reaction of
anthracene-9-yl-methyltriphenylphosphine chloride with
PL) in MeOH, and showed a PL peak at 421 and
92 nm, respectively. N-Arylation of those compounds
4
8
quenched their photoluminescence probably due to
intermolecular interactions between the pyridinium salts
generated by the N-arylation. It was reported that the
N-alkylation of fluorescent pyridine derivatives drasti-
cally decreased their fluorescence due to the stronger
intermolecular interactions between the N-alkylated
4
-pyridinecarboxaldehyde. See Supplementary data.
9
. A representative procedure to obtain the Zincke salt is as
follows: After an acetone solution (100 mL) of 1-chloro-
2
,4-dinitrobenzene (20.3 g, 100 mmol) and 4-phenylpyri-
dine (15.5 g, 100 mmol) was heated at reflux for 11 h, the
precipitate from the reaction solution was collected by
1
2
molecules.

I. Yamaguchi et al. / Tetrahedron Letters 48 (2007) 7778–7781
7781
filtration, which was washed with n-pentane (300 mL) and
washed with acetone (300 mL). Compound 3d was col-
dried under vacuum to afford 1a as a light green powder
lected by filtration, dried under vacuum, and obtained as a
light brown powder (Table 1, entry 6, 0.53 g, 86%). H
1
1
(
25.1 g, 70%). H NMR (DMSO-d , 400 MHz): d 9.53 (d,
6
J = 5.2 Hz, 2H), 9.12 (s, 1H), 8.99 (dd, J = 2.4, 8.8 Hz,
6
NMR (400 MHz, DMSO-d ): d 9.11 (d, J = 7.2 Hz, 2H),
1
8
H), 8.89 (d, J = 7.2 Hz, 2H), 8.53 (d, J = 8.8 Hz, 1H),
.28 (d, J = 6.8 Hz, 2H), 7.68–7.76 (m, 3H). C NMR
8.58 (d, J = 7.2 Hz, 2H), 8.17 (d, J = 7.2 Hz, 2H), 7.69–
1
3
7.66 (m, 3H), 7.21 (s, 1H), 6.64 (s, 1H), 2.09 (s, 3H), 2.04
1
3
1
(
DMSO-d , 100 MHz): d 157.2, 149.0, 145.9, 143.2, 138.5,
(s, 3H). C{ H} NMR (100 MHz, DMSO-d ): d 154.6,
6
6
1
33.1, 133.0, 132.2, 130.2, 129.9, 128.7, 124.1, 121.3.
149.1, 146.2, 133.4, 132.3, 130.5, 129.7, 129.6, 128.3, 127.1,
124.3, 119.4, 114.9, 16.9, 16.6. Anal. Calcd for
C H ClN 2.5H O: C, 64.66; H, 6.18; N, 12.57. Found:
1
0. A representative procedure to obtain the pyridinium salt is
as follows: N-(2,4-Dinitrophenyl)-4-phenylpyridinium
chloride (1a) (0.72 g, 2.0 mmol) and 2,5-dimethyl-1,4-
phenylenediamine (2f) (0.55 g, 4.0 mmol) were dissolved
1
9
19
2
2
C, 64.63; H, 5.85; N, 12.30.
11. Turshatov, A. A.; M o¨ bius, D.; Bossi, M. L.; Hell, S. W.;
Vedernikov, A. I.; Lobova, N. A.; Gromov, S. P.; Alfimov,
M. V.; Zaitsev, S. Y. Langmuir 2006, 22, 1571–1579.
12. Akhtaruzzaman, M.; Tomura, M.; Nishida, J.; Yamash-
ita, Y. J. Org. Chem. 2004, 69, 2953–2958.
2
in 3 mL of dry ethanol under N . After the solution was
refluxed for 12 h, 2,4-dinitroaniline precipitated from the
reaction solution was removed by filtration. The solvent
was evaporated under vacuum, and the resulting solid was