An improved method for tricyanovinilation of aromatic amines under ultrasound irradiation

Article abstract of DOI:10.1016/j.dyepig.2011.03.004

A synthetic method for tricyanovinylation under ultrasound irradiation has been developed for preparation of tricyanovinyl aromatic amines. The method is reliable and can be applied to the synthesis of a variety of tricyanovinyl compounds, with high yields, purity and with short reaction times.

Full text of DOI:10.1016/j.dyepig.2011.03.004

Dyes and Pigments 91 (2011) 74e78
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journal homepage: www.elsevier.com/locate/dyepig
An improved method for tricyanovinilation of aromatic amines
under ultrasound irradiation
*
Todor Deligeorgiev , Nedyalko Lesev, Stefka Kaloyanova
University of Sofia, Faculty of Chemistry, 1164 Sofia, Bulgaria
a r t i c l e i n f o
a b s t r a c t
Article history:
A synthetic method for tricyanovinylation under ultrasound irradiation has been developed for prepa-
ration of tricyanovinyl aromatic amines. The method is reliable and can be applied to the synthesis of
a variety of tricyanovinyl compounds, with high yields, purity and with short reaction times.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 11 November 2010
Received in revised form
2 March 2011
Accepted 4 March 2011
Available online 12 March 2011
Keywords:
Aromatic amines
Tricyanovinylation
Tricyanovinyl compounds
Tetracyanoethylene
Ultrasound irradiation
1. Introduction
as cytotoxic agents against tumours [11], as X-ray protective agents
[12] and as photostabilizers in plastics against UV radiation [13].
The chemical applications of ultrasound, “sonochemistry”, have
become an exciting new field of research in the past decade. The use
of ultrasound in chemistry offers a convenient method of chemical
activation which has broad applications and uses equipment which
is relatively inexpensive. The advantages of ultrasonic irradiation
include not only improving classical reactions, shortening reaction
times, increasing yields, and suppressing by-product formation
compared with conventional thermal heating but also ultrasound
may offer cleaner reactions by improving selectivity, enhancing
product recoveryand purificationprocesses [1,2]. It is widely used to
improve traditional reactions which use expensive reagents,
strongly acidic conditions, long reaction times, high temperatures
and which are incompatible with other functional groups. Sonica-
tion allows the use of non-activated and crude reagents as well as an
aqueous solvent system; therefore it is friendly and non-toxic [3].
The 4-tricyanovinylarylamines are a class of dyes used to colour
synthetic polymer fibres [4], but their special optical and electrical
properties also make them of considerable interest in applications
in the field of nonlinear optics [5], in diode lasers in optical
recording [6] to monitor polymerization reactions [7] and in the
fabrication of hybrid organiceinorganic solar cells [8e10]. They act
Electronic excitation on these compounds induces an initial intra-
molecular charge transfer (ICT) state with partial electron transfer,
generally followed by molecular twisting to give a complete elec-
tron transfer in a twisted ICT (TICT) state, in which the donor orbital
is perpendicular to the acceptor orbital. Depending on the mole-
cule’s structure, both ICT and TICT states can be radiative, especially
in fluid polar media [14]. Because these flexible fluorescent dye
molecules are proven to be sensitive to both the local viscosity
(rigidity) and local polarity, they provide a suitable means to study
the relaxation processes in low density polyethylene films [15].
The reaction of tetracyanoethylene with secondary and tertiary
aromatic amines in which hydrogen is bonded to the annular
carbon in the 4-position and heterocyclic aromatic amines in which
the ring is resonance stabilized, takes place via a condensation to
give 4-tricyanovinylanilines or tricyanovinyl-substituted hetero-
cyclic aromatic amines and hydrogen cyanide. The 4-tricyanovi-
nylanilines absorb visible light very strongly and comprise a class of
brilliant red and blue dyes [16].
Various methods to prepare tricyanovinylaryl compounds have
been reported. These include condensations: the condensation of
tetracyanoethylene with arylamines or phenols, carried in dry
tetrahydrofuran, at boiling temperatures for between 0.5 and 18 h
gives low to good yields [16]; good or excellent yields were obtained
from the condensation in dimethylformamide at 50e90 ꢀC
[4,17e19]. Another method involves the tricyanovinylation of
* Corresponding author. Tel.: þ359 2 8161 269; fax: þ359 2 8625438.
E-mail address: toddel@chem.uni-sofia.bg (T. Deligeorgiev).
0143-7208/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2011.03.004

T. Deligeorgiev et al. / Dyes and Pigments 91 (2011) 74e78
75
thiazoles and thiophenes carried in DMF for 12 h at room temper-
2.1.2. 2-[4-(Diethylamino)-2-methoxyphenyl]
ature, after refluxing for 1 h [20]. Two other widely used synthetic
routes use stepwise conversions starting from arylaldehydes where
the aldehydes are first converted to dicyanovinyl compounds via
condensation with malonodinitrile, then to tricyanovinyl by nucle-
ophilic substitution of dicyanovinyl with sodium cyanide, followed
by oxidation with lead tetraacetate [21] or by lithiation followed by
quenching with tetracyanoethylene [22,23].
We describe here a simple and convenient procedure to
synthesize 4-tricyanovinylanilines and 5-tricyanovinyl-2-amino-
thiazoles by reaction of tetracyanoethylene with aromatic amines
under mild conditions, generally at room or higher temperature
and atmospheric pressure, using ultrasonic irradiation.
ethene-1,1,2-tricarbonitrile (3g)
M.p.: 138e142. 1H-NMR (
d
ppm): 1.19 t (6H, NCH2CH3); 3.42 q
(4H, NCH2CH3); 3.88 s (3H, OCH3); 5.99 d (1H, ArH), 6.30 dd (1H,
ArH); 7.55 d (1H, ArH). 13C-NMR (
ppm): 161.35, 154.65, 135.53,
d
133.65, 128.40, 118.73, 114.90, 113.96, 113.56, 108.41, 106.07, 98.33,
93.44, 55.03, 45.53, 12.60. MS (API-ES) m/z: 281 [M þ H]þ. For
C16H16N4O (280.32) calcd: C, 68.55; H, 5.75; N, 19.99; O, 5.71;
found: C, 68.44; H, 5.90; N, 14.99; O, 13.71.
2.1.3. 2-{Benzyl[4-(1,2,2-tricyanovinyl)phenyl]amino}-N,N,
N-trimethylethanaminium perchlorate (3q)
M.p.: 138e140. 1H-NMR (
d
ppm): 3.13 s (9H, N(CH3)3; 3.50e3.54 m
(2H, CH2); 3.74 t (2H, CH2); 4.49 s (2H, CH2); 6.89e6.93 m (2H, ArH);
7.29e7.39 (7H, ArH). 13C-NMR (
ppm): 148.66, 147.32, 138.82, 138.61,
d
2. Experimental
137.92, 137.80, 129.06, 128.90, 127.73, 127.66, 127.03, 122.70, 118.25,
117.30,112,63,110.80, 91.81, 61.33, 59.54, 55.29, 54.61, 51.50, 48.13. MS
(API-ES) m/z: 470 [M þ H]þ. For C23H24ClN5O4 (469.92)calcd:C, 58.79;
H, 5.15; N, 14.90; O, 13.62; found: C, 58.60; H, 5.20; N, 14.99; O, 13.71.
All products were characterized and/or compared with reported
data. Melting points were obtained on a Kofler apparatus and are
uncorrected. 1H-NMR and 13C-NMR spectra of the previously unre-
ported compounds were recorded on a Bruker Avance DRX 600 MHz
spectrometer in CDCl3 as solvent. Mass spectrawere obtained on a LC-
HP1100 apparatus in methanol-water (3:1) as solvent. The experi-
ments were performed in the positive ion mode. Visible absorption
spectra were recorded on Unicam UV 500 (1 ꢁ10ꢂ5 mol/l). The reac-
tions were carried out in a Diamondback-UD50SH ultrasonic bath
operating at frequency of 40 kHz, acoustic power 50 W, capacity 2 l,
heating temperature up to 70 ꢀC. The progress of the reactions was
monitored by TLC (Merck F 254 silica gel; dichloromethane: n-
heptane, 9:1). Starting compounds 1ae1e, 1he1k, 1le1p are
commercial products from SigmaeAldrich. Tetracyanoethylene is
a commercial product from TCI Europe. Compounds 1f, 1g, 1l, 1q, 2a
and 2b were synthesized according to knownprocedures [24e30]. All
of the solvents are also commercial products from SigmaeAldrich and
are used without further purification. Analytical samples of the
reaction products were obtained by recrystallization from ethanol.
2.1.4. 2,20-[2,20-(piperazine-1,4-diyl)bis(4-phenylthiazole-5,2-diyl)]
diethene-1,1,2-tricarbonitrile (4b)
M.p.: 220e222. 1H-NMR (
d
ppm): 3.72 s (4H, CH2NCH2); 3.93
s (4H, CH2NCH2); 7.19 s (2H, ArH); 7.24 t (1H, ArH); 7.33 t (2H, ArH);
7.44e7.48 m (4H, ArH); 7.53 t (1H, ArH). 13C-NMR (
ppm): 159.02,
d
158.72, 153.03, 152.81, 146.90, 146.01, 133.88, 133.45, 132.06, 130.45,
130.36, 130.31, 129.15, 129.10, 128.93, 128.88, 128.68, 128.24, 128.19,
126.28, 126.14, 112.09, 104.21, 102.73, 102.28, 60.51, 60.48, 50.92,
47.99, 47.82, 47.49, 47.27. MS (API-ES) m/z: 607 [M þ H]þ. For
C32H18N10S2 (606.68) calcd: C, 63.35; H, 2.99; N, 23.09; S, 10.57;
found: C, 63.42; H, 2.95; N, 22.98; S, 10.55.
3. Results and discussion
The tricyanovinylation reaction of aromatic amines with tet-
racyanoethylene is
a typical termal reaction involving the
2.1. General procedure for tricyanovynilation of N,N-dialkylanilines
and 2-aminosubstituted 4-phenylthiazoles by a sonochemical
method
formation of charge-transfer (CT) complex. The reaction
proceeds in two steps: formation of an accumulating interme-
diate, and slow formation of the final product. Rappoport [31]
studied systematically the tetracyanovinylation reactions of
N,N-dimethylaniline and N-methylaniline with tetracyano-
ethylene for the first time and found that the complex formed
between reactants gradually disappears to form the intermediate
Caution! Because hydrogen cyanide is formed in this reaction,
all operations up to the recrystallization of the product should be
carried out in a good hood. Skin contact with tetracyanoethylene
should be avoided.
zwitterionic
s-complex and thereafter the final tricyanovinyl
Tetracyanoethylene (0.004 mol) and the corresponding N-alkyl
or N,N-dialkylaniline or 2-aminothiazole (0.004 mol; for compound
2c 0.002 mol) were dissolved in 2 ml N,N-dimethylformamide in
a 25 ml Erlenmeyer flask. The reaction mixture was sonicated at
a frequency of 40 kHz at room temperature or 60 ꢀC for a time
between 5 and 20 min (see Table 1). The mixture was poured into
water (100 ml) and isolated by filtration. Compound 3q was iso-
lated as oil after addition of Et2O. The oil was dissolved in methanol
and a concentrated water solution of NaClO4 was added to obtain
the product as dark red solid.
compound is slowly produced.
There is another proposed mechanism for this reaction where
the zwitterionic
s-complex produce neutral intermediate by
deprotonation from another donor molecule followed by back
proton transfer from the quarternary amine to carbanion resulting
from the zwitterionic complex [32].
A variety of N-alkyl-, N,N-dialkylanilines 1ae1q and two
2-aminosubstituted 4-phenylthiazoles 2a, 2b were coupled with
tetracyanoethylene for the first time under ultrasonic irradiation to
form the corresponding 4-tricyanovynylarylamines 3ae3q and
5-tricyanovynil thiazoles 4a, 4b according to Scheme 1.
2.1.1. 2-{4-[Methyl(phenethyl)amino]phenyl}
We tried a variety of solvents, including THF, chloroform,
dichloromethane, acetic acid, ethanol and others, but the best
results were obtained in N, N-dimethylformamide. The reactions
were carried for 5 to 20 min, at room temperature (20e25 ꢀC) for
compounds 3ae3d, 3f, 3g, 3ke3q, 4b, and at 60 ꢀC for compounds
3e, 3he3j, and 4a. In general, the desired products were isolated in
good to excellent yields (Table 1).
ethene-1,1,2-tricarbonitrile (3f)
M.p.:116e118. 1H-NMR (
d
ppm): 2.87 t (2H, CH2); 2.96 s (3H,
CH3); 3.69 t (2H, NCH2); 6.65 d (2H, ArH); 7.10 d (2H, ArH); 7.19 t
(2H, ArH); 7.24e7.26 m (3H, ArH). 13C-NMR (
ppm): 154.10, 148.11,
d
137.73, 137.46, 133.04, 128.99, 128.96, 128.92, 128.91, 128.75, 127.08,
117.56, 114.48, 114.03, 113.74, 112.26, 77.79, 54.70, 39.38, 33.59. MS
(API-ES) m/z: 313 [M þ H]þ. For C20H16N4 (312.37) calcd: C, 76.90; H,
5.16; N, 17.94; found: C, 76.79; H, 5.16; N, 18.05.
Initially we studied the reaction progress by conventional
conditions for compounds 3b, 3k and 4a e without using of

76
T. Deligeorgiev et al. / Dyes and Pigments 91 (2011) 74e78
Table 1
Sonication times, reaction temperature, starting compounds (1ae1q, 2a, 2b), products (3ae3q, 4a, 4b) and yields (%).
Sonication time [min]
Temperature [ꢀC]
Starting compound
Product structure
Yield %/Lita
99/83 [21]
CH3
CH3
NC
CH3
N
CH3
N
N
N
N
5
r.t.
NC
CN
3a
3b
3c
3d
3e
CH2CH3
CH2CH3
NC
CH2CH3
N
CH2CH3
5
r.t.
r.t.
r.t.
60
r.t.
r.t.
60
60
60
r.t.
r.t.
r.t.
r.t.
91/80 [21]/51c
90/66 [33]
73/63 [21]
82/50 [21]
99
NC
CN
CH2CH3
NC
CH2CH3
N
CH2CH2OH
10
15
20
10
10
15
10
15
5
CH2CH2OH
NC
CN
CH2CH3
NC
CH2CH3
N
CH2CH2CN
NC
CN
CH2CH2CN
CH2CH2CN
CH2CH2CN
NC
CH2CH2CN
N
N
N
NC
CN
NC
CH2CH2CN
CH3
CH3
N
CH2CH2
CH2CH2
NC
CN
3f
H3CO
NC
H3CO
CH2CH3
CH2CH3
CH2CH3
N
N
79
N
NC
CN
CH2CH
3 1g
3g
NC
N
70/59 [21]
88/37 [21]
77/65 [21]
82/47 [21]/35c
92/63 [34]
71/35 [16]
NC
CN
1h
1i
3h
3i
NC
NH
NC
CN
N
H
NC
CH3
CH3
N
N
NC
CN
1j
3j
NC
CH2CH2OH
CH2CH2OH
N
N
N
NC
CN
H
H
1k
3k
NC
CH2CH2OH
CH2CH2OH
N
5
NC
CN
CH2CH2OH
CH2CH2OH
1l
3l
3m
3n
NC
CH2CH2CN
CH2CH2CN
N
N
15
5
NC
CN
H
H
1m
NC
CH3
CH3
N
N
82/70 [21]
NC
CN
H
H
1n
(continued on next page)

T. Deligeorgiev et al. / Dyes and Pigments 91 (2011) 74e78
77
Table 1 (continued)
Sonication time [min]
Temperature [ꢀC]
r.t.
Starting compound
Product structure
NC
NC
Yield %/Lita
70/b [35]
CH2CH3
CH2CH3
N
H
N
N
10
15
10
20
H
1o
CN
3o
3p
NC
NC
C4H7
C4H7
N
r.t.
r.t.
60
78/42 [21]
H
H
1p
CN
NC
H2C
N
CH2CH2N(CH3)3
ClO4
H2C
N
CH2CH2N(CH3)3
ClO4
40
NC
CN
1q
3q
89/22 [20]/7c
NC
NC
N
N
N
N
O
S
N
S
2a
O
CN
4a
N
N
10
r.t.
82
N
N
S
N
CN
NC
NC
N
N
S
S
S
2b
NC
CN 4b
CN
a
Literature data.
No yield reported.
b
c
Blank reaction: same reaction conditions with stirring, without ultrasound irradiation.
ultrasound (see Table 1, note c). The desire product was isolated
with significantly lower yield in comparison with the same reaction
carried out by sonication (Table 1).
molar absorptivities are in the range 27 900e85 900 l
molꢂ1 cmꢂ1. The absorption spectra of the new chromophores
are characterized by an intense, low energy band. The most
bathochromic shift was observed for 3-methoxy-N,N-diethyl
derivative dye 3g. Dye 3q, which contains a positive charge,
showed the highest molar absorptivity compared to the other
dyes. Table 2 summarizes the visible absorption spectral data for
the four new dyes measured in methanol.
A
number of the compounds have not been previously
reported, specifically 3f, 3g, 3q and 4b. These were fully char-
acterized by 1H-NMR, 13C-NMR, mass spectra and by elemental
analyses. The longest wavelength absorption maxima of the
structures are in the region 484e520 nm. The corresponding
R5
R4
R5
R4
R1
R2
NC
NC
R1
R2
N
N
R3
1a - 1q
CN
R3
3a - 3q
DMF, 20 - 600C, )))
NC
NC
CN
CN
+
Ph
Ph
N
S
N
R
S
NC
NC
R
2a - 2b
CN
4a - 4b
1a, 3a: R1=R2=CH3, R3,R4, R5=H; 1b, 3b: R1=R2=C2H5, R3=R4=R5=H; 1c, 3c: R1=CH3, R2=C2H4OH,
R3=R4=R5=H; 1d, 3d: R1=C2H5, R2=C2H4CN, R3=R4=R5=H; 1e, 3e: R1=R2=C2H4CN, R3=R4=R5=H;
1f, 3f: R1=CH3, R2=CH2CH2Ph, R3=R4=R5=H; 1g, 3g: R1=R2=C2H5, R3=R4=H, R5=OCH3;
1h, 3h: R1,R4 and R2, R3=CH2CH2CH2, R5=H; 1i, 3i: R1=H, R2,R3=CH2CH2CH2, R4=R5=H;
1j, 3j: R1=CH3, R2=Ph, R3=R4=R5=H; 1k, 3k: R1=C2H4OH, R2=R3=R4=R5=H; 1l,3l: R1=R2=C2H4OH,
R3=R4=R5=H; 1m, 3m: R1=C2H4CN, R2=R3=R4=R5=H; 1n, 3n: R1=CH3, R2=R3=R4=R5=H;
1o, 3o: R1=C2H5, R2=R3=R4=R5=H; 1p, 3p: R1=C4H7, R2=R3=R4=R5=H;
1q, 3q: R1=CH2Ph, R2=CH2CH2N+(CH3)3, R3=R4=R5=H;
Ph
Ph
N
S
N
CN
CN
;
4b: R=
N
;
O
2b: R=
N
2a, 4a: R= N
N
N
S
NC
Scheme 1.

78
T. Deligeorgiev et al. / Dyes and Pigments 91 (2011) 74e78
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Absorption maxima and molar absorptivities for compounds 3ae3q and 4a, 4b.
a
Compound
lmax [nm]
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[l molꢂ1 cmꢂ1
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
4a
4b
514
521
518
507
488
517
520
555
519
509
503
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487
498
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484
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502
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46,500 [21]
44,000 [7]
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37,200 [21]
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79,000
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40,900 [21]
32,600 [21]
38,400b [29]
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41,400 [21]
41,400b [30]
44,000 [21]
85,900
23,000 [20]
27,900
a
Reported data.
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In summary we developed an effective and reliable method for
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2-aminosubstituted-4-phenylthiazoles under ultrasound irradia-
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