Preparation and Characterization of 3,4-Diaryl-Substituted 2-Diarylaminothiophenes

Article abstract of DOI:10.1055/s-2004-815933

Starting from N,N,C-triarylacetamides and 1-aryl-2-bromoethanones a series of new 3,4-diaryl-substituted 2-diarylaminothiophenes have been prepared and characterized spectroscopically.

Full text of DOI:10.1055/s-2004-815933

PAPER
377
Preparation and Characterization of 3,4-Diaryl-Substituted 2-Diarylamino-
thiophenes
P
reparation and Ch
l
aracter
a
ization of
3
f
,4-Diaryl-Sub
Z
stituted 2-Diary
e
laminothiop
i
henes ka,a Horst Hartmann*b
a
Institute of Applied Photophysics, Technical University Dresden, Mommsenstr. 13, 01346 Dresden, Germany
b
Department of Chemistry, University of Applied Sciences, Geusaer Str., 06217 Merseburg, Germany
Fax +49(3461)462192; E-mail: Horst.Hartmann@cui.fh-merseburg.de
Received 24 October 2003; revised 17 December 2003
Their synthesis can be carried out by carboxylation of 4
or, via their corresponding alkyl carboxylates, by a simple
ring-closure reaction.13
Abstract: Starting from N,N,C-triarylacetamides and 1-aryl-2-bro-
moethanones a series of new 3,4-diaryl-substituted 2-diarylami-
nothiophenes have been prepared and characterized
spectroscopically.
Since it has been demonstrated in several series of oligo-
thiophenes that the electronic properties of the appropriate
compounds can be strongly influenced by introducing
special substiuents in their 3,4-positions,14 it seems of in-
terest to synthesize such derivatives in the , -diarylami-
no-capped oligothiophene series 2n. For instance, aryl
substituents in these positions should influence not only
the stability of the cationic species generated by their ox-
idation but also the intramolecular interaction of the mol-
ecules in the solid state affecting a better migration of the
corresponding charge carriers from one molecular unit to
its adjacent units.
Key words: amines, cyclization, heterocycles, oxidations
Recently, N,N-diaryl-substituted 2-aminothiophenes 3 re-
ceived a lot of interest. They have not only been used for
the synthesis of highly stable dyes with pronounced non-
linear optical or elctrophotographic properties,1 but also
for the synthesis of , -bisdiarylamino-capped oligo-
thiophenes (Figure 1) 2n.2 These compounds were em-
ployed, similar to their carbocyclic analogues 1n,3 as
starting materials for the preparation of compounds with
tuneable electric conductivity,4 Due to the ease with
which they form amorphous glasses from their melts, rad-
ical cations generated by their oxidation have a high sta-
bility and large mobility.5 Such compounds can be used
for manufacturing electrooptical and microelectronic de-
vices, e.g., as photocopiers,6 organic light emitting di-
odes,7 organic field-effect transistors,8 or organic solar
cells.9
[Pd]
2n
+
Br
Br
Ar2N
X
S
S
j
(n = j+2)
3 X=H
7j
BuLi
4 X=Li
ClSnBu3
5 X=SnBu3
6 X=COOH
[Pd]
+
3
Ar2NH
Br
H
Ar2N
NAr2
S
Ar2N
NAr2
n
S
n
8
9
2n
1n
Scheme 1
Figure 1
Certain 2-(N,N-diarylamino)thiophenes with aryl groups
in 3- and 4-positions should be versatile staring materials
to prepare , -diarylamino-capped oligothiophenes with
additional aryl groups in these positions. However, such
compounds are almost unknown. To prepare these com-
pounds a simple ring-closure reaction starting from
N,N,C-triaryl-subtituted thioacetamides 10 and 1-aryl-2-
bromoethanones 11 can be employed (Scheme 2). This
synthetic method was previously applied to the synthesis
of 3,4-diaryl-substituted 2-dialkylaminothiophenes15 and
for some 5,5 -dialkylamino- and 5,5 -diarylamino-2,2 -
bithiophenes.16
The transformation of N,N-disubstituted 2-ami-
nothiophenes 3 into 5,5 -bisdiarylamino-capped oligoth-
iophenes 2n was performed by a palladium-catalyzed
coupling reaction of metallated 2-aminothiophenes 4 or 5
with the dibromothiophenes 7j (Scheme 1).10 The metal-
lated thiophenes 4 or 5 were available by standard metal-
lation methods from their 5H-substituted parent
compounds 3.11 Compounds 3 were prepared, in turn, ei-
ther from diarylamines 8 and 2-bromothiophene 9 by a
palladium-catalyzed coupling reaction1,12 or by decarbox-
ylation of 2-diarylaminothiophene-5-carboxylic acid 6.
The ring-closure reaction was performed by allowing 10
and 11 to react in a solvent, such as dichloromethane, at
room temperature followed by addition of triethylamine
to the reaction mixture. The reaction proceeds via inter-
SYNTHESIS 2004, No. 3, pp 0377–0380
Advanced online publication: 26.01.2004
DOI: 10.1055/s-2004-815933; Art ID: T11303SS
© Georg Thieme Verlag Stuttgart · New York
x
x
.
x
x
.2
0
0
4

378
O. Zeika, H. Hartmann
PAPER
CH3
Ar3
O
Ar4
Ar3
O
Ar4
Br
+
Ar2
H3C
Ar2
+
N
S
N
S
Br-
Ar1
Ar1
10
12
11
H
N
S
- H2O
- HBr
Ar4
Ar3
Ar2
H3C
13h
N
H
for Ar1, Ar2, Ar3, Ar4 see Table 1
S
Ar1
- 2 e-, - 2 H+
13
CH3
CH3
Scheme 2
H3C
mediate thioamidinium salts 12 and gives the products 13
in satisfactory yields. The 3,4-diarylamino-substituted 2-
diarylaminothiophenes 13 so prepared are depicted in
Table 1.
N
S
S
N
CH3
They are colorless, air-stable compounds whose struc-
tures were unambiguously determined by elemental anal-
ysis, mass spectra, and NMR measurements. Some of
these data are recorded in Table 2.
H3C
H3C
14
Scheme 3
In contrast to the 13C NMR spectra, the 1H NMR spectra
of the aryl-substituted 2-aminothiophenes 13 are less in-
dicative since only unresolved multiplets were found be-
tween 6.75 and 7.95 ppm. These multiplets originate from
the aryl protons. The signals of the thiophene protons at
C(5) are usually hidden under these multiplets. Only pro-
tons of aliphatic groups, if present, can be detected by
their signals in the expected range.
As expected, the N,N,3,4-tetraaryl-substituted 2-ami-
nothiophenes 13 can be used as starting materials for the
preparation of N,N -peraryl-substituted 5,5 -diamino-2,2 -
bithiophenes and their homologues (Scheme 3). This
transformation can be performed by using several oxidiz-
ing reagents and certain preparative methods which will
Table 1 3,4-Diaryl-substituted 2-(N,N-Diarylamino)thiophenes 13 Prepared
Compd
13a
13b
13c
13d
13e
13f
Ar1Ar2N
Ar3
Ar4
Yield (%)
62
Mp ( °C)
108–110
151–152
175–176
128–129
110–112
148–150
145
(C6H5)2N
C6H5
C6H5
(C6H5)2N
C6H5
4-C6H5-C6H4
4-CH3-C6H4
4-CH3O-6H4
1-C10H7
69
(C6H5)2N
C6H5
75
(C6H5)2N
C6H5
76
(C6H5)2N
C6H5
68
(C6H5)2N
C6H5
2-C10H7
70
13g
13h
13i
(4-CH3-C6H4)2N
(4-CH3-C6H4)2N
(4-CH3-C6H4)2N
(4-CH3O-C6H4)2N
1-C10H7-(C6H5)N
1-C10H7-(C6H5)N
2-C10H7-(C6H5)N
2-C10H7-(C6H5)N
C6H5
C6H5
68
C6H5
4-CH3-C6H4
4-CH3-C6H4
4-CH3O-C6H4
C6H5
72
137–138
197
4-CH3-C6H4
4-CH3O-C6H4
C6H5
69
13j
63
147
13k
13l
62
153–154
167–169
168–169
125–127
C6H5
1-C10H7
64
13m
13n
C6H5
C6H5
59
C6H5
2-C10H7
65
Synthesis 2004, No. 3, 377–380 © Thieme Stuttgart · New York

PAPER
Preparation and Characterization of 3,4-Diaryl-Substituted 2-Diarylaminothiophenes
379
Table 2 Spectroscopic Data of the 3,4-Diaryl-Substituted 2-(N,N-Diarylamino)thiophenes 13 Prepareda
Compd
m/z
1H NMR (CDCl3), (ppm)
13C NMR (CDCl3), (ppm)
13a
403
6.88–7.23 (m, 20 Harom), 6.92
(s, 1 Hheteroarom.)
120.33, 122.31, 122.89, 127.46, 127.48, 128.46, 128.72, 129.45,
129.51, 130.52, 135.59, 137.54, 139.94, 142.22, 146.84, 148.14
13b
479
6.89–7.58 (m, 24 Harom.,
1 Hheteroarom.)
119.60, 121.59, 122.18, 126.63, 126.77, 126.85, 127.17, 127.79,
128.67, 128.77, 129.00, 129.82, 134.86, 135.75, 137.18, 139.36,
140.56, 140.97, 146.23, 147.37
13c
13d
13e
417
433
453
2.31 (s, 3 H, CH3), 6.89–7.2
21.77, 119.86, 122.25, 122.81, 127.37, 128.41, 129.24, 129.42, 129.46,
130.48, 134.63: 135.68, 137.08, 137.93, 142.12, 146.69, 148.11
(m, 19 Harom., 1 Hhetarom.
)
3.78 (s, 3 H OCH3) 6.75–7.22
(m, 19 H arom., 1 Hhetarom.)
55.78, 114.15, 119.35, 122.23, 122.81, 127.37, 128.42, 129.45, 130.12,
130.47, 130.48, 135.69, 137.88, 141.75, 146.66, 148.10, 159.21
6.81–7.95 (m, 22 Harom, 1 Hhetarom.
)
121.34, 121.63, 122.26, 125, 125.57, 125.81, 126.08, 126.52, 127.41,
127.63, 128.03, 128.12, 128.86, 129.13, 132.35, 133.52, 134.59,
135.06, 138.49, 139.81, 145.5, 147.46
13f
453
6.86–7.74 (m, 22 Harom., 1 Hhetarom.) 120.01, 121.55, 122.18, 125.73, 125.95, 126.79, 127.08, 127.32, 127.33
127.51, 127.80, 127.94, 128.8, 129.77, 132.19, 133.27, 134.37, 134.76,
137.24, 141.34, 146.22, 147.35
13g
13h
431
445
2.26 (s, 6 H, CH3), 6.85–7.22
(m, 18 Harom., 1 Hhetoarom.
20.66, 119.42, 121.42, 126.64, 126.68, 127.69, 127.96, 128.72, 129.35,
129.83, 131.43, 134.94, 136.85, 136.91, 141.37, 145.27, 146.6
)
2.27 (s, 6 H, CH3), 2.3 (s, 3 H,
CH3), 6.84–7.11 (m, 17 H arom.),
20.66, 21.09, 118.98, 121.42, 126.59, 127.67, 128.55, 128.70, 129.33,
129.84, 131.39, 134.06, 135.09, 136.32, 136.89, 141.31, 145.3, 146.47
7.13 (s, 1 Hhetarom.
)
13i
459
523
2.24 (s, 3 H, CH3), 2.27 (s, 6 H,
CH3), 2.30 (s, 3 H CH3), 6.83–7.08 129.64, 131.30, 131.99, 134.20, 136.09, 136.23, 137.13, 141.32,
(m, 16 Harom.), 7.12 (s, 1 Hheteroarom.
20.66, 21.12, 21.18, 119.16, 121,35, 128,41, 128.53, 128,69, 129.33,
)
145.39, 146.02
13jb
3.71 (s, 3 H, OCH3), 3.73
(s, 6 H, OCH3), 3.75 (s, 3 H
OCH3), 6.62–7.08 (m, 16 Harom.),
55.38, 55.47, 55.77, 113.51, 113.70, 114.46, 118.52, 122.94, 127.87,
130.06, 130.16, 131.33, 136.36, 141.47, 141.97, 147.01, 155.34,
158.83, 158.94
7.06 (s, 1 Hhetarom.
)
13k
13l
453
503
453
503
6.79–7.79 (m, 22 Harom., 1 Hhetarom.) 117.68, 119.09, 120.22, 124.54, 125.43, 125.62, 125.71, 125.88,
126.43, 126.68, 127.75, 127.93, 127.95, 128.00, 128.65, 128.74,
129.93, 130,00, 134.73, 135.17, 136.67, 136.82, 141.40, 142.56,
147.23, 150.15
6.76–7.95 (m, 24 Harom., 1 Hhetarom.
)
117.53, 120.18, 120.87, 124.54, 124.92, 125.51, 125.71, 125.73,
125.79, 125.95, 126.09, 126.46, 126.55, 127.40, 127.42, 127.52,
127.96, 128.05, 128.09, 128.81, 129.34, 130.03, 132.33, 133.42,
134.82, 134.91, 135.03, 138.02, 139.74, 142.64, 146.44, 150.27
13m
13n
6.92–7.74 (m, 22 Harom., 1 Hhetarom.
)
117.61, 119.74, 121.87, 121.98, 122.45, 124.21, 126.17, 126.78,
126.80, 126.97, 127.48, 127.75, 128.01, 128.50, 128.72, 128.83,
129.67, 129.76, 134.13, 134.78, 136.74, 137.31, 141.50, 145.14,
146.04, 147.27
6.94–7.8 (m, 24 Harom., 1 Hhetarom.
)
117.41, 119.56, 121.69, 121.76, 122.31, 124.04, 125.57, 125.78,
126.01, 126.65, 126.76, 126.88, 127.15, 127.17, 127.28, 127.31,
127.62, 127.74, 128.34, 128.67, 129.49, 129.57, 132.04, 133.09,
133.95, 134.15, 134.56, 137.15, 141.21, 144.95, 145.00, 147.07
a All compounds gave satisfactory elemental analysis C 0.25, H 0.22, N 0.2, S 0.21.
b Measured in CD2Cl2.
be described in detail elsewhere.17 The course of this process the formation of a rather unstable radical cation
transformation can be studied by cyclic voltammetry.
13h·+ can be assumed. It dimerizes immediately upon for-
mation giving rise to the formation of a corresponding
N,N -peraryl-substituted 5,5 -diamino-2,2 -bithiophene
14 as consequence of a radical-radical dimerization or
As exemplified in Figure 2 for compound 13h, its oxida-
tion starts at about +0.45 V, the other thiophene com-
pounds 13 are similar. Due to the irreversibility of this
Synthesis 2004, No. 3, 377–380 © Thieme Stuttgart · New York

380
O. Zeika, H. Hartmann
PAPER
radical-substrate coupling process.18 The formation of the
5,5 -diamino-2,2 -bithiophene 14 during the electrochem-
Yield: 3.65g, (82%); mp 224–225 °C.
1H NMR(CDCl3): = 2.25 (s, 12 H, CH3), 2.28 (s, 6 H, CH3), 6.70–
ical process is indicated by a reversible peak appearing at 7.00 (m, 34 Harom.).
13C NMR(CDCl3):
127.71, 128.13, 129.22, 129.79, 130.57, 131.30, 132.66, 135.10,
136.02, 137.55, 140.57, 144.96, 145.86.
= 20.64, 21.25, 121.35, 126.30, 127.36,
about +0.06 V. Its intensity increases continuously with
the number of scans and its potential is measured in the
same range as is found for the 5,5 -diamino-2,2 -
bithiophene reference compound 14 prepared from the
same precursor 13h by its reaction with bromine as oxi-
dizing reagent.
MS: m/z (%) = 888 (100), 444 (26).
Anal. Calcd for C62H52N2S2 (889.23): C, 83.74; H, 5.91; N, 3.15; S,
7.20. Found: C, 83.80; H, 5.72; N, 3.06; S, 7.17.
Acknowledgment
The authors thank Dirk Rohde for the measurement and discussion
of cyclic voltammogramms as well the Bundesministerium für Bil-
dung und Forschung (BMBF) for financial support. The authors are
also grateful to Prof. Karl Leo for his support.
References
(1) (a) Bedworth, P. V.; Marder, S. R.; Jen, A. K.-Y.; Cai, M. J.
Org. Chem. 1996, 61, 2242. (b) Jen, A. K.-Y.; Cai, Y.;
Bedworth, P. V.; Marder, S. R. Adv. Mater. 1997, 9, 132.
(c) Shoshi, M. N. S. Sasaki M. S. S. DE 3 439 113, 1984;
Chem. Abstr. 1986, 104: 59361.
(2) (a) Gerstner, P.; Rohde, D.; Hartmann, H. Synthesis 2002,
2487. (b) Wong, K. T.; Hung, T. H.; Kao, S. C.; Chou, C. H.;
Su, Y. O. Chem. Commun. 2001, 1628.
Figure 2 Cylic voltammogramm of compound 13h
(3) (a) Goodbrand, H. C.; Hu, N. X. J. Org. Chem. 1999, 64,
670. (b) O’Brien, D. F.; Burrows, P. E.; Forrest, S. R.;
Koene, B. E.; Loy, D. E.; Thompson, M. E. Adv. Mater.
1998, 10, 1109.
(4) Shirota, Y. J. Mater. Chem. 2000, 10, 1.
(5) Fuhrmann, T.; Salbeck, J. Adv. Photochem. 2002, 27, 83.
(6) Getautis, V.; Stanisauskaite, A.; Paululis, O.; Uss, S.; Uss,
V. J. Prakt. Chem. 2000, 342, 58.
The following instruments and analytical techniques were used:
melting points: Kofler hot-stage microscope, corrected; NMR: Ino-
va 500 ‘max 2’, Varian 300 MHz spectrometer, Gemini 300, with
CDCl3 as solvent; elemental analysis: LECO analyzer CHNS 932;
MS: AMOspectrometer 402 (70 eV, EI); mass spectra: ESI, LCQ,
Finnigan MAT.
(7) (a) Johnson, G. E.; McGrane, K. M.; Stolka, M. Pure Appl.
Chem. 1995, 67, 175. (b) Noda, T.; Ogawa, H.; Noma, N.;
Shirota, Y. J. Mater. Chem. 1999, 9, 2177. (c) Shirota, Y.;
Okumoto, K.; Inada, H. Synth. Met. 2000, 111-112, 387.
(8) Horowitz, G. Adv. Mater. 1998, 10, 365.
(9) (a) Cariciftci, N. S.; Smilowitz, L.; Heeger, A. J.; Wudl, F.
Science 1992, 258, 1474. (b) Halls, J. J. M.; Walsh, C. A.;
Greenham, N. C.; Marseglia, E. A.; Friend, R. H.; Moratti,
S. C.; Holmes, A. B. Nature (London, U.K.) 1965, 376, 498.
(10) Tabet, A.; Schröder, A.; Hartmann, H.; Rohde, D.; Dunsch,
L. Org. Lett. 2003, 5, 1817.
Cyclic voltammetry: Autolab instrument PGSTAT 20. The mea-
surements were performed under N2 in benzonitrile containing
Bu4NPF6 as supporting electrolyte with a scan rate of 0.1 V/s using
a stationary working platinum electrode, a platinum counter elec-
trode, and a stationary platinum reference electrode. Standard redox
potentials have been estimated versus ferrocene/ferrocenium in
benzonitrile as reference redox system for a nearly reversible elec-
trode processes.
N,N-Diarylamino-Substituted 3,4-Diarylthiophenes 13; Gener-
al Procedure
(11) (a) Effenberger, F.; Würthner, F.; Steybe, F. J. Org. Chem.
1995, 60, 2082. (b) Noack, A.; Hartmann, H. Chem. Lett.
2002, 644.
(12) (a) Kisselev, R.; Thelakkat, M. Chem. Commun. 2002,
1530. (b) Wu, I. Y.; Lin, J. T.; Tao, Y.-T.;
A solution of a N,N-disubstituted thioacetamide (10, 0.01 mol) and
a bromoketone (11, 0.01 mol) in EtOH (100 mL) was refluxed for 6
h. After cooling, the mixture was diluted with ice-water (200 mL)
and the precipitate was isolated by filtration, followed by recrystal-
lization from EtOH or HOAc.
Balasubramaniam, E.; Su, Y. Z.; Ko, C.-W. Chem. Mater.
2001, 13, 2626.
(13) Hartmann, H.; Gerstner, P.; Rohde, D. Org. Lett. 2001, 3,
1673.
(14) (a) McCullough, R. D. Adv. Mater. 1998, 10, 93.
(b) Roncali, J. Chem. Rev. 1992, 92, 711.
(15) Hartmann, H.; Mayer, R. Z. Chem. 1966, 6, 28.
(16) Schumann, J.; Kanitz, A.; Hartmann, H. Synthesis 2002,
1268.
Bis-5,5 [(4-toly)amino-4-phenyl-3(4-tolyl)]2,2 -bithiophene (14)
A solution of Br2 (6.39g, 40 mmol) in dichloroethane (20 mL) was
added at ambient temperature under stirring to a solution of 2-bis-
[(4-tolyl)amino]-3-phenyl-4-(4-tolyl)thiophene (13h, 4.46g, 10
mmol) in dichloroethane (60 ml) and refluxed for 0.5 h. After cool-
ing, the dark blue precipitate was separated by filtration und washed
with Et2O. The product was dissolved in acetone (100 mL), NaBH4
(0.86g) was added and the solution heated to reflux until it became
colorless. The solution was concentrated and the product precipitat-
ed with MeOH and recrystallized from MeCN.
(17) Zeika, O.; Hartmann, H. European Patent claimed.
(18) Hammerich, O.; Parker, V. D. Adv. Phys. Org. Chem. 1984,
20, 55.
Synthesis 2004, No. 3, 377–380 © Thieme Stuttgart · New York