A versatile route to N, N′-tetraaryl-substituted 2,5- diaminothiophenes

Article abstract of DOI:10.1055/s-0030-1260178

By reaction of N,N-tetraaryl-substituted succinic di-amides with Lawessons reagent, a series of N,N-tetraaryl-substituted 2,5-diaminothiophenes was prepared. The N,N-tetrakis(4-bromophenyl)-2,5-diaminothiophene, thus available, was used as an educt for th

Full text of DOI:10.1055/s-0030-1260178

PAPER
3375
A Versatile Route to N,N¢-Tetraaryl-Substituted 2,5-Diaminothiophenes
N
,
N
¢
-Tetraaryl-Su
h
bstituted 2,5
r
-Diamin
i
othioph
s
ene
s
toph Heichert, Marion Wrackmeyer, Horst Hartmann*
Department Chemie, Technische Universität Dresden, George-Bähr-Str. 1, 01069 Dresden, Germany
Fax +49(351)46339485; E-mail: hartmann@iapp.de
Received 20 June 2011; revised 21 July 2011
Dedicated to Prof. Dr. Dr. h. c. mult. Siegfried Hünig on the occasion of his 90th birthday
substituted 2-aminothiophenes, which are easily available
by a heavy-metal-free heterocyclisation method starting
from N-diaryl-substituted thioacetamides and haloke-
tones.10 Here, we report a simple synthetic route to N,N¢-
Abstract: By reaction of N,N¢-tetraaryl-substituted succinic di-
amides with Lawesson’s reagent, a series of N,N¢-tetraaryl-substi-
tuted 2,5-diaminothiophenes was prepared. The N,N¢-tetrakis(4-
bromophenyl)-2,5-diaminothiophene, thus available, was used as
an educt for the synthesis of N,N¢-tetrakis(4-diphenylaminophenyl)- peraryl-substituted 2,5-diaminothiophenes 6 (B; n = 1)
2,5-diaminothiophene by reaction with four equivalents of diphenyl-
that also avoids the use of heavy-metal catalysts.
amine in the presence of palladium as catalyst. Both the N,N¢-tet-
raaryl-substituted 2,5-diaminothiophenes and the N,N¢-tetrakis(4-
diphenylaminophenyl)-2,5-diaminothiophene can be electrochemi-
cally oxidised in a stepwise manner via the corresponding radical
cations into relatively stable dications. The latter compounds can
also be oxidised into tetracationic species.
Ar1
Ar1
Ar1
Ar2
Ar1
N
N
N
N
S
n
n
Ar2
[M]
Ar2
Ar2
Key words: amides, hiophenes, heterocycles, Lawesson’s reagent,
oxidation
B
A
[M]
Hal
Hal
Hal
Hal
N,N¢-Peraryl-substituted 1,4-phenylenediamines and their
phenylene homologues of type A have received a lot of in-
terest because of their ability to form amorphous glasses
in which the cationic species generated by oxidation have
a high mobility. Such compounds can be used as hole
transport materials, for example, for building optoelec-
tronic devices, such as OFET,2 OLED,3 OSOL,4 photo-
copiers,5 and others. The same applies to the N,N¢-peraryl-
substituted 2,5-diaminothiophenes and their thienylene
homologues B.6 Similar to the carbocyclic compounds A,
the heterocyclic analogues B have been prepared by
heavy-metal catalysed C–N coupling reactions starting
from diarylamines 3 and appropriate dihalo-arylenes 1 or
2,5-dihalothiophenes and homologues 2, respectively
(Scheme 1).7
S
Ar1
n
n
1
2
NH
Ar2
3
Scheme 1
The first step of this new route is similar to the C–N cou-
pling reactions mentioned above from diarylamines 3, but
these starting materials are transformed by reaction with
succinic dichloride 4 into the corresponding N,N¢-peraryl-
substituted succinic diamides 5, from which the target
compounds 6 are available by reaction with Lawesson’s
reagent (LR)11 according to the well-known Paal–Knorr
procedure (Scheme 2).12
In contrast to the preparation of the N,N¢-peraryl-substi-
tuted 1,4-phenylenediamines and their homologues A, the
N,N¢-peraryl-substituted 2,5-diaminothiophene analogues
B were frequently obtained in low yields by using such
heavy-metal catalysed procedures;8 clearly, undesirable
deactivation of the catalysts by the sulphur-containing re-
actants occurred in these cases.
For the preparation of the N,N¢-peraryl-substituted succin-
ic diamides 5, the interaction of one equivalent of succinic
dichloride 4 with two equivalents of an appropriate diaryl-
amine 3 in dioxane at reflux temperature, was successful.
After cooling the reaction mixture, the precipitated N,N¢-
peraryl-substituted succinic diamides 5 could be isolated
by suction, mostly in satisfactory yields. For the prepara-
tion of the N,N¢-peraryl-substituted 2,5-diaminothio-
phenes 6, the reaction of succinic diamides 5 with the LR
in either 1,4-dioxane or 1,2-dimethoxyethane proved to be
successful. The reaction yields the 2,5-diaminothiophenes
6 in satisfactory yields, generally without the formation of
detectable by-products. Unfortunately, little evidence for
the mechanism of the reaction has, as yet, be gained, how-
ever, because thioamides are the usual reaction products
To overcome this disadvantage, we have searched for
heavy-metal-free synthetic routes with which to prepare
such sulphur-containing compounds. One of these routes,
which allows N,N¢-peraryl-substituted 5,5¢-diamino-2,2¢-
bithienyles (B; n = 2) to be prepared in satisfactory yields,
consists of an oxidative coupling reaction9 of N-diaryl-
SYNTHESIS 2011, No. 20, pp 3375–3378
x
x.
x
x
.
2
0
1
1
Advanced online publication: 18.08.2011
DOI: 10.1055/s-0030-1260178; Art ID: T47011SS
© Georg Thieme Verlag Stuttgart · New York

3376
C. Heichert et al.
PAPER
3
unambiguously confirmed from the analytic data. Thus,
all the prepared compounds give the expected elemental
analyses and mass spectra. In the 1H NMR spectra of the
N,N¢-peraryl-substituted succinic diamides 5, characteris-
tic signals at d = 4 ppm and between 7–9 ppm were mea-
sured that could be assigned to the protons in the aliphatic
methylene groups and in the aryl moieties, respectively. In
O
Cl
4
Cl
O
Ar1
Ar2
O
1
Ar1
N
the H NMR spectra of the N,N¢-peraryl-substituted 2,5-
diaminothiophenes 6, characteristic singlets at d = 6 ppm
and multiplets between 7–9 ppm were detected that could
be assigned to the protons at the 2,5-diaminothiophene
moieties as well as at the N-linked aryl groups, respective-
ly. In the 1H NMR spectra of the N,N¢-naphthyl-substituted
succinic diamide 5d and the 2,5-diaminothiophenes 6c
and 6d as well as in the spectra of the tetrahydroquinolyl-
substituted compounds 5f and 6f certain signals of the
aromatic protons appear as doublets or triplets indicating
the existence of certain rotamers in the corresponding
samples.
3–6 Ar1Ar2N
N
O
a
b
c
d
e
f
Ph2N
Ar2
5
(4-BrC6H4)2N
1-naphthyl(Ph)N
2-naphthyl(Ph)N
phenothiazinyl
tetrahydroquinolyl
LR
Ar1
Ar2
Ar1
N
N
S
Ar2
6
The N,N¢-peraryl-substituted 2,5-diaminothiophenes 6,
thus prepared, are rather stable as solids under anaerobic
conditions but are easily oxidised in solution. As demon-
strated earlier7a and further documented by electrochemi-
cal measurements depicted in Table 1 and Figure 1, all
N,N¢-peraryl-substituted 2,5-diaminothiophenes 6 can be
electrochemically oxidised to relatively stable radical cat-
ions 6·+ and dications 62+. Remarkably, the N,N¢-bis(2-
naphthyl)-N,N¢-diphenyl-2,5-diaminothiophene (6d) ex-
hibits an additional irreversible peak at approximately
0.83 V, indicating a further oxidative transformation.
Scheme 2
of N,N-disubstituted amides with LR,11 it can be assumed
that the first reaction step involves the formation of the
corresponding thioamides from the starting succinic di-
amides 5. Such compounds can be transformed, when par-
ticular structural requirements are satisfied, into the
appropriate N,N-disubstituted 2-aminothiophene deriva-
tives.13
It is worth mentioning that the synthesis of the N,N¢-tet-
rakis(4-diphenylaminophenyl)-substituted 2,5-diamino-
thiophene 7 from the corresponding N,N¢-tetrakis(4-
diphenylaminophenyl)-substituted succinic diamide using
the Paal–Knorr procedure was not efficient because the
preparation of the necessary and commercially unavail-
able 4,4¢-bis-(diphenylamino)diphenylamine starting ma-
terial is performed on the corresponding carbamide
derivative, which has to be transformed subsequently into
the free amine.14 Therefore, the synthetic route to 7 de-
scribed in Scheme 3 seems to be the most effective alter-
native.
Table 1 Electrochemical Data of the N,N¢-Peraryl-Substituted 2,5-
Diaminothiophenes 6 and 7
Compd.1st Ox [V]
2nd Ox [V]
3rd Ox [V]
a
a
a
E1/2
E1/2 (Fc)b E1/2
E1/2 (Fc)b E1/2
E1/2 (Fc)b
6a
6b
6c
6d
6e
6f
7
0.31
0.48
0.34
0.33
0.48
0.26
0.17
–0.07
0.09
0.74
0.85
0.57
0.71
0.83
0.68
0.40
0.36
0.46
0.18
0.34
0.46
0.26
0.00
–
–
–
–
–0.05
–0.04
0.11
0.83c
0.42c
–
–
The structures of both the succinic diamides 5 and the
N,N¢-peraryl-substituted 2,5-diaminothiophenes 6 were
–
–
–0.16
–0.24
–
–
1.02
0.62
a Measured vs. Ag/AgCl.
b E1/2(Fc/Fc+) = 0.40 V.
c Irreversible.
N
N
Pd(OAc)2,
(t-Bu)3P
N
N
S
The N,N¢-tetrakis(4-diphenylaminophenyl)-substituted
2,5-diaminothiophene 7, which was obtained in satisfac-
tory yield by reaction of the tetrabromo-compound 6b
with an excess of diphenylamine 3a in the presence of
Pd(OAc)2 and P(tert-Bu)3 as catalyst, could be electro-
chemically transformed in several well-separated steps
3a + 6b
7
N
N
Scheme 3
Synthesis 2011, No. 20, 3375–3378 © Thieme Stuttgart · New York

PAPER
N,N¢-Tetraaryl-Substituted 2,5-Diaminothiophenes
3377
Preparation of N,N¢-Tetrasubstituted Succinic Diamides 5;
General Procedure
To a mixture of a diarylamine 3 (0.1 mol) and zinc chloride (0.27 g,
2 mmol) in dioxane (150 mL), succinyl dichloride 4 (7.75 g, 0.05
mol) was added dropwise and the resulting solution was heated at
reflux for 4 h. The product precipitated by cooling was separated by
suction and air-dried. Because the products, thus obtained, con-
tained variable amounts of dioxane, analytical samples were typi-
cally recrystallised from toluene.
N,N¢-Tetraphenyl-succinic Diamide (5a)
Yield: (80%); mp 233 °C.
1H NMR (500 MHz, CDCl3): d = 2.58 (s, 4 H, CH2), 7.17–7.46 (m,
20 H, ArH).
Anal. Calcd for C28H24N2O2: C, 79.98; H, 5.75; N, 6.66. Found: C,
80.22; H, 5.82; N, 6.13.
N,N¢-Tetrakis(4-bromophenyl)succinic Diamide (5b)
Yield (78%); mp 230–232 °C.
1H NMR (500 MHz, CDCl3): d = 2.52 (s, 4 H, CH2), 7.48 (m, 16 H,
ArH).
Anal. Calcd for C28H20Br4N2O2: C, 45.69; H, 2.74; Br, 43.42; N,
3.81. Found: C, 45.45; H, 2.50; Br, 43.70; N, 4.12.
N,N¢-Bis(1-naphthyl)-N,N¢-diphenyl-succinic Diamide (5c)
Yield (60%); mp 242–245 °C.
1H NMR (500 MHz, CDCl3): d = 2.18–2.76 (m, 4 H, CH2), 7.17 (s,
2 H, ArH), 7.26–7.33 (m, 4 H, ArH), 7.44–7.49 (m, 12 H, ArH),
7.86–7.92 (m, 4 H, ArH), 8.04–8.12 (m, 2 H, ArH).
Anal. Calcd. for C36H28N2O2: C, 83.05; H, 5.42; N, 5.38. Found: C,
83.20; H, 5.12; N, 5.33.
N,N¢-Bis(2-naphthyl)-N,N¢-diphenyl-succinic Diamide (5d)
Yield (68%); mp 250 °C.
1H NMR (500 MHz, CDCl3): d = 2.65 (br s, 4 H, CH2), 6.95–7.12
(t, 2 H, ArH), 7.18–7.50 (m, 16 H, ArH), 7.62–7.65 (d, 2 H, ArH),
7.71–7.74 (d, 4 H, ArH).
Figure 1 Cyclic voltammograms of some of the N,N¢-persubstitu-
ted 2,5-diaminothiophenes 6 and 7
Anal. Calcd for C36H28N2O2: C, 83.05; H, 5.42; N, 5.38. Found: C,
83.27; H, 5.04; N, 5.00.
into the corresponding radical cation 7·+, dication 72+, and
tetracation 74+ at 0.17, 0.40 and 1.02 V, respectively.
1,4-Bis(N-phenothiazinyl)butane-1,4-dione (5e)
Yield (75%); mp 286 °C.
1H NMR (500 MHz, CDCl3): d = 2.50 (s, 2 H, CH2), 2.78 (br s, 2 H,
Further efforts to study the chemical nature and the elec-
tronic properties of the oxidised species of the N,N¢-per- CH2), 7.17–7.22 (m, 4 H, ArH), 7.27–7.32 (m, 4 H, ArH), 7.40 (d,
aryl-substituted 2,5-diaminothiophenes 6 and 7 are in
J = 10.0 Hz, 4 H, ArH), 7.56 (d, J = 10.4 Hz, 4 H, ArH).
progress and will be reported later.
Anal. Calcd for C28H20N2O2S2: C, 69.97; H, 4.19; N, 5.83; S, 13.34.
Found: C, 70.14; H, 4.06; N, 6.11; S, 13.84.
1H NMR spectra were recorded with a Bruker DRX 500 P instru-
ment at 500.13 MHz. Elemental analyses were performed with a
Eurovektor Hekatech EA-3000 elemental analyzer. Mass spectra
were recorded in MeOH with a Bruker Esquire-LC 00084 instru-
ment, operating at 10 V with electrospray ionisation. Melting points
were measured with a Boetius heating-table microscope. Cyclic
voltammetry was conducted with a Metrohm m-Autolab potentiostat
in a single-component cell under a nitrogen atmosphere. A typical
three-electrode configuration was used with an inlaid platinum disk
as working electrode, platinum wire as counter electrode, and a sil-
ver rod electrochemically coated with AgCl. Potentials were mea-
sured versus a Ag/AgCl electrode and referenced to ferrocene (Fc)
as an internal standard. The measurements were performed with a
scan rate of 100 mV·s–1 in CH2Cl2 under a nitrogen atmosphere and
with tetra-n-butylammonium hexafluorophosphate (0.1 M) as elec-
trolyte. No reduction peaks were observed between 0 and –2.3 V.
1,4-Bis(N-tetrahydroquinolyl)butane-1,4-dione (5f)
Yield (82%); mp 77 °C.
1H NMR (500 MHz, CDCl3): d = 1.94 (m, 4 H, CH2), 2.70 (t, 4 H,
CH2), 2.84 (s, 4 H, CH2), 3.77 (t, 4 H, CH2), 7.13 (m, 8 H, ArH).
Anal. Calcd for C22H24N2O2: C, 75.83; H, 6.94; N, 8.04. Found: C,
76.05; H, 7.11; N, 8.24.
Preparation of N,N¢-Tetrasubstituted 2,5-Diaminothiophenes
6; General Procedure
A mixture of appropriate N,N¢-tetraaryl-substituted succinic di-
amide 5 (0.1 mol) and Lawesson’s reagent (50 g, 0.12 mol) in either
dioxane or 1,2-dimethoxyethane (250 mL) was heated at reflux un-
der stirring for 24 h. After cooling, the reaction mixture was neutr-
alised by addition of aqueous NaOH (10%) under stirring, and the
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3378
C. Heichert et al.
PAPER
precipitated products were isolated by suction, washed with water
and air-dried.
1H NMR (500 MHz, CDCl3): d = 2.08 (m, 4 H, CH2), 2.85 (t,
J = 6.3 Hz, 4 H, CH2), 3.64 (t, J = 5.6 Hz, 4 H, CH2), 6.59 (s, 2 H,
CHth), 6.73 (t, 2 H, ArH), 6.88 (d, 2 H, ArH), 7.02 (m, 4 H, ArH).
N,N¢-Tetraphenyl-2,5-diaminothiophene (6a) from 5a
MS (ESI, 70 eV): m/z calcd for C22H22N2S: 346.49; found: 347.2.
Yield (70%); mp 148 °C (Lit.7b 144–145 °C).
Anal. Calcd for C22H22N2S: C, 76.26; H, 6.40; N, 8.08; S, 9.25.
Found: C, 76.00; H, 6.40; N, 8.00; S, 9.00.
1H NMR (500 MHz, CDCl3): d = 6.44 (s, 2 H, CHth), 6.9–7.02 (m,
4 H, ArH), 7.14–7.26 (m, 8 H, ArH), 7.25–7.30 (m, 8 H, ArH).
MS (ESI, 70 eV): m/z calcd for C28H22N2S: 418.55; found: 419.2.
Preparation of N,N,N¢,N¢-[Tetrakis(4-diphenylamino)phe-
nyl]thiophene-2,5-diamine (7)
Anal. Calcd for C28H22N2S: C, 80.35; H, 5.30; N, 6.69; S, 7.66.
Found: C, 80.63; H, 5.18; N, 7.02; S, 7.50.
To an argon-degassed solution of N,N,N¢,N¢-tetrakis(4-bromophe-
nyl)-2,5-diaminothiophene (6b; 3.67 g, 0.05 mol) and diphenyl-
amine (3a; 3.72 g, 0.022 mol) in p-xylene (50 mL), palladium
diacetate (22.45 mg, 0.001 mol), tri-tert-butylphosphine in xylene
(27%, 0.001 mol, 0.82 mL), and sodium tert-butylate (2.4 g, 0.025
mol) were successively added and the resulting mixture was heated
at reflux for 15 min. After cooling to r.t., the mixture was diluted
with MeOH (200 mL) and stirred for 30 min. The precipitated prod-
uct was filtrated, washed with MeOH (100 mL) and dried.
N,N¢-Tetrakis(4-bromophenyl)-2,5-diaminothiophene (6b)
from 5b
Yield (78%); mp 142–145 °C.
1H NMR (500 MHz, CDCl3): d = 6.46 (s, 2 H, CHth), 6.99 (d,
J = 8.9 Hz, 8 H, ArH), 7.36 (d, J = 8.9 Hz, 8 H, ArH).
MS (ESI, 70 eV): m/z calcd for C28H18Br4N2S: 734.14; found:
734.8.
Yield (96%); mp 229–234 °C.
1H NMR (500 MHz, C6D6): d = 6.46 (s, 2 H, CHth), 6.87 (t,
J = 7.3 Hz, 8 H, ArH), 7.01 (d, J = 8.9 Hz, 8 H, ArH), 7.08 (m,
16 H, ArH), 7.14 (d, J = 8.9 Hz, 8 H, ArH), 7.24 (m, 16 H, ArH).
Anal. Calcd for C28H18Br4N2S: C, 45.81; H, 2.47; Br, 43.54; N,
3.82; S, 4.37. Found: C, 46.02; H, 2.50; Br, 44.24; N, 3.71; S, 4.84.
N,N¢-Bis(1-naphthyl)-N,N¢-diphenyl-2,5-diaminothiophene (6c)
from 5c
MS (ESI, 70 eV): m/z calcd for C76H58N6S: 1087.38; found: 1087.7.
Yield (72%); mp 173 °C (Lit.7b 120–125 °C).
Anal. Calcd for C76H58N6S: C, 83.95; H, 5.38; N, 7.73; S, 2.95.
Found: C, 84.00; H, 5.00; N, 7.73; S, 3.00.
1H NMR (500 MHz, CDCl3): d = 6.73 (d, 2 H, CHth), 6.84 (t, 2 H,
ArH), 6.87–6.92 (m, 6 H, ArH), 7.17 (t, 2 H, ArH), 7.43 (t, 2 H,
ArH), 7.47–7.51 (m, 6 H, ArH), 7.80 (d, 2 H, ArH), 7.90 (d, 2 H,
ArH), 8.04 (d, 2 H, ArH).
References
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MS (ESI, 70 eV): m/z calcd for C36H26N2S: 518.67; found: 519.2.
Anal. Calcd for C36H26N2S: C, 83.36; H, 5.05; N, 5.40; S, 6.18.
Found: C, 83.12; H, 4.89; N, 5.85; S, 6.26.
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N,N¢-Bis(2-naphthyl)-N,N¢-diphenyl-2,5-diaminothiophene(6d)
from 5d
Yield (66%); mp 119 °C.
1H NMR (500 MHz, CDCl3): d = 6.41 (d, J = 10.0 Hz, 2 H, CHth),
6.85 (t, J = 10.0 Hz, 2 H, ArH), 7.05 (t, J = 9.5 Hz, 4 H, ArH), 7.14–
7.16 (m, 4 H, ArH), 7.24–7.27 (m, 4 H, ArH), 7.35–7.41 (m, 4 H,
ArH), 7.47 (br s, 2 H, ArH), 7.49–7.54 (m, 2 H, ArH), 7.64 (br s,
2 H, ArH).
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MS (ESI, 70 eV): m/z calcd for C36H26N2S: 518.67; found: 519.3.
Anal. Calcd for C36H26N2S: C, 83.36; H, 5.05; N, 5.40; S, 6.18.
Found: C, 82.96; H, 5.00; N, 5.27; S, 6.38.
2,5-Bis(N-phenothiazyl)thiophene (6e) from 5e
Yield (97%); mp 215 °C.
1H NMR (500 MHz, CDCl3): d = 6.90 (dd, J = 8.2, 0.9 Hz, 4 H,
ArH), 6.94 (dt, J = 8.6, 1.1 Hz, 4 H, ArH), 7.07 (s, 2 H, CHth), 7.06
(m, 4 H, ArH), 7.10 (dd, J = 7.6, 1.3 Hz, 4 H, ArH).
MS (ESI, 70 eV): m/z calcd for C28H18N2S3: 478.65; found: 481.1.
Anal. Calcd for C28H18N2S3: C, 70.26; H, 3.79; N, 5.85; S, 20.10.
Found: C, 70.02; H, 4.03; N, 6.12; S, 20.56.
2,5-Bis(N-tetrahydroquinolyl)thiophene (6f) from 5f
(14) Hirao, Y.; Ito, A.; Tanaka, K. J. Phys. Chem. A 2007, 111,
2951.
Yield (82%); mp 111–113 °C.
Synthesis 2011, No. 20, 3375–3378 © Thieme Stuttgart · New York