Arylamino-thieno-oxobutanainides under Lawesson's conditions: Competition between thienylpyrrole and bithiophene formation

Article abstract of DOI:10.1055/s-2004-834952

1-Aryl-2-thienyl-substituted pyrroles and/or 5-arylamino-2,2′- bithiophenes were synthesized by treatment of arylamino-thieno-oxobutanamides with Lawesson's reagent. These in turn were prepared by direct amidation of 4-oxo-(2-thienyl)butanoic acid through DCC-BtOH mediated reactions.

Full text of DOI:10.1055/s-2004-834952

PAPER
199
Arylamino-thieno-oxobutanamides under Lawesson’s Conditions:
Competition between Thienylpyrrole and Bithiophene Formation
Competition between
T
.
hienylpyrro
M
a
nd Bithiophene
F
o
a
a
Centro de Química, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
Fax +351(253)678983; E-mail: mfox@quimica.uminho.pt
b
Laboratoire d´ Ingénierie Moléculaire et Biochimie Pharmacologique, UFR SciFA/Université de Metz 1, Boulevard Arago,
Metz Technopôle, 57078 Metz Cedex 3, France
Received 2 July 2004; revised 20 September 2004
pared via the condensation of 1,4-dicarbonyl compounds
with ammonia or primary amines,11–16 a reaction known as
the Paal–Knorr synthesis.26
Abstract: 1-Aryl-2-thienyl-substituted pyrroles and/or 5-arylami-
no-2,2¢-bithiophenes were synthesized by treatment of arylamino-
thieno-oxobutanamides with Lawesson’s reagent. These in turn
were prepared by direct amidation of 4-oxo-(2-thienyl)butanoic
acid through DCC–BtOH mediated reactions.
Due to their numerous potential applications, there is a
continuous interest in the development of versatile syn-
thetic routes.
Keywords: amides, substituent effects, pyrroles, bicyclic com-
pounds, heterocycles
We have previously reported an efficient method for the
synthesis of N,N-dialkyl-4-(2¢-thienyl)-4-oxobutana-
mides by direct amidation of 4-oxo-(2-thienyl)butanoic
acid through a DCC–1-hydroxybenzotriazole (BtOH) me-
diated reaction.27 We applied this approach to the synthe-
sis of aryl-4-(2¢-thienyl)-4-oxobutanamides, which
embody several different substituents [donating substituents
(F, Cl, Br, I, CH3, OH, OMe) or withdrawing substituents
(CO2Me, CN, NO2)]; thus extending our early work. As
part of our continuing interest in non-linear optical
materials27–30 and in order to obtain new compounds as
precursors with potential application in NLO in this paper
we describe the synthesis and the reactivity studies of
aryl-4-(2¢-thienyl)-4-oxobutanamides with the Lawes-
son’s reagent. In our study, instead of the expected 5-aryl-
amino-2,2¢-bithiophenes, we obtained 1-aryl-2-(2¢-
thienyl)pyrroles or a mixture of 1-aryl-2-(2¢-thienyl)pyr-
roles and 5-arylamino-2,2¢-bithiophenes. The conjugated
1-aryl-2-(2¢-thienyl)pyrroles and 5-arylamino-2,2¢-bithio-
phenes, as strong p-electron donor moieties, could be used
as precursors in the preparation of compounds with poten-
tial application in NLO.11–15,27
Thiophene and pyrrole moieties play important roles in
natural product chemistry,1,2 non-linear optics (NLO),3,4
and supramolecular chemistry.5 The development of new
methods of synthesis of these heterocycles is therefore im-
portant. 2-Aryl- and 2-heteroaryl-substituted pyrroles are
also of great interest to the pharmaceutical industry, for
instance, as precursors in the synthesis of chemotherapeu-
tics.1,6,7 Some of these molecules, in particular the thie-
nylpyrroles, have served as prospective monomers for
non-linear optical materials and organic conductive poly-
mers.8–18
The latter combine high electrical conductivity, with ther-
mal and environmental stability. The synthesis of thie-
nylpyrroles containing substituents at the nitrogen atom
attracts considerable attention because the substitution
makes it possible to modify the properties of polymers, in-
cluding the synthesis of chiral conducting polymeric ma-
terials with better properties for NLO. These new systems
are expected to show some advantageous features: i) the
aryl group is perpendicular to the p-system such that the
coplanarity is affected to a lesser extent and causes a ba-
thochromic shift in its UV-vis absorption spectrum; ii) the
perpendicular aryl group prevents the stacking of the p-
system and as a result increases its solubility; iii) various
aryl groups can be employed in order to modify the phys-
ical properties of 1-aryl-2-(2¢-thienyl)pyrroles.8,10,18,19
This method is interesting because the experimental pro-
cedures described use mild reaction conditions and simple
work-up procedures allow the preparation of these deriv-
atives in moderate to good yields.
Starting from succinic anhydride, we prepared the 3-car-
bomethoxypropionyl chloride which on Friedel–Crafts re-
action with thiophene afforded the methyl 4-(2-thienyl)-
4-oxobutanoate. Hydrolysis of the g-keto ester gave 4-
oxo-(2-thienyl)butanoic acid.27,31,32 Transformation of 4-
oxo-(2-thienyl)butanoic acid to the aryl-4-(2¢-thienyl)-4-
oxobutanamides 1a–v was carried out by direct amidation
of the acid with several commercial arylamines through
DCC–BtOH mediated reaction (Scheme 1). No secondary
products were detected and the yields were fair to good,
depending on the nucleophilicity of the aryl amine
(Table 1). A broad correlation could be observed between
reaction yields on the synthesis of amides 1 and the chem-
A common approach to the synthesis of both thiophene
and pyrrole groups involves the use of 1,4-dicarbonyl
compounds. In the thiophene case, the 1,4-dicarbonyl
compound is reacted with a source of sulfur, usually H2S
and HCl, phosphorus(V) sulfide or Lawesson’s reagent
(LR).20–25 Similarly, pyrroles have traditionally been pre-
SYNTHESIS 2005, No. 2, pp 0199–0210
x
x
.
x
x
.2
0
0
4
Advanced online publication: 03.12.2004
DOI: 10.1055/s-2004-834952; Art ID: T08004SS
© Georg Thieme Verlag Stuttgart · New York

200
M. M. M. Raposo et al.
PAPER
ical shift of the nitrogen protons of the starting aryl- Table 1 Yields Obtained in the Synthesis of Aryl-4-(2¢-thienyl)-4-
oxobutanamides 1a–v
amines; in fact, from the data in Table 1 one may infer that
an increase in the chemical shift of the NH2 protons results
Entry
Compound
1
R
Yield
(%)a
dH
in a decrease in the basic character of the aryl amine and
lower yields are obtained for the corresponding aryl-4-(2¢-
thienyl)-4-oxobutanamides 1a–v. The different effect of
substituents in the anilines used is noteworthy (20–73%).
As expected the amides 1d–e and 1j (Table 1, entries 4, 5
and 10) obtained from the anilines with electron-donating
groups in ortho or/and in para position (d = 3.99–4.64
ppm) were synthesized in better yields: 62–73%. The
amides 1t–v (Table 1, entries 19–21) obtained from
anilines with electron-withdrawing groups in meta or
para position (dH = 5.34–5.63 ppm) were synthesized in
fair yields: 24–35%. 1-Naphthylamine (dH = 5.23 ppm)
was even less reactive than the other arylamines giving
only 20% of amide 1b (Table 1, entry 2). Aryl amides 1b,
1n–o, 1q–r, 1t–v, were obtained in lower yields even after
seven days of reaction time. It was possible to detect, by
TLC, some unreacted 4-oxo-(2-thienyl)butanoic acid and
arylamine starting material.
(ppm)b
1
2
a
b
c
d
e
f
H
42
20
46
6227
6427
56
49
54
51
73
41
53
23
22
53
30
26
55
24
35
31
4.54
5.23
4.36
4.21
3.99
4.64
4.44
4.23
4.35
4.64
4.54
4.93
5.15
4.80
4.95
4.83
5.16
4.89
5.34
5.45
5.63
1-naphthyl
2-OMe
4-OMe
2,4-diOMe
3,5-diOMe
3,4,5-triOMe
2-OH
3
4
5
6
7
g
h
i
8
9
2-Me
10
11
12
13
14
15
16
17
18
19
20
21
j
2-F
l
4-F
m
n
o
p
q
r
s
2-Cl
3-Cl
4-Cl
2-Br
Scheme 1
4-Br
2,4-diBr
2-I
We also examined the effect of reaction time on the syn-
thesis of aryl-4-(2¢-thienyl)-4-oxobutanamides 1a–v. As
expected a longer reaction time was necessary for the syn-
thesis of aryl-4-(2¢-thienyl)-4-oxobutanamides 1a–v (7 d)
compared to the analogous reaction to obtain N,N-dialkyl-
4-(2¢-thienyl)-4-oxobutanamides (1 d).27 In the case of
aryl-4-(2¢-thienyl)-4-oxobutanamides 1j and 1r the yields
improved markedly when the reaction time increased
from one day to seven days (1j, 14–73%), (1r, 8–26%).
t
3-NO2
4-CO2Me
4-CN
u
v
a Reaction time: 7 d.
b For the NH2 protons of arylamines (300 MHz, acetone-d6).
The reaction of aryl-4-(2¢-thienyl)-4-oxobutanamides 1
with an equimolar amount of LR in toluene at reflux tem-
perature for 15–30 minutes yielded 1-aryl-2-(2¢-thie-
nyl)pyrroles 2 and/or 5-arylamino-2,2´-bithiophenes 3
(Scheme 2, Table 2).
Treatment of 2¢¢-hydroxyphenyl-4-(2¢-thienyl)-4-oxobu-
tanamide (1h) with LR under the same experimental con-
ditions gave a complex mixture with several products
(TLC). After purification by flash chromatography, it was
only possible to isolate and identify traces (3%) of pyrrole
2h. The very low yield of pyrrole 2h was probably due to
the formation of the corresponding phosphorous-contain-
ing heterocycle.22,25
Attempts to convert the aryl-4-(2¢-thienyl)-4-oxobutana-
mides 1a–v into the corresponding 5-arylamino-2,2¢-
bithiophenes 3 gave only thienylpyrroles 2 (3–55%),
(Table 2, entries 2 and 6–8) or a mixture of thienylpyr-
roles 2 (16–58%) and bithiophene derivatives 3 (Table 2,
entries 1, 3–5, 9–11, 14, 16, 17, 19–21) in low yields (7–
32%), with pyrroles being the major compounds (Table 2,
Scheme 2). Bithiophene derivatives 3m, 3n, 3p and 3s
were obtained as major compounds (21–55%) only in the
case of treatment of 2- or 3-haloaryl-4-(2´-thienyl)-4-oxo-
butanamides 1m, 1n, 1p and 1s with LR under the same
experimental conditions as described above (Table 2, en-
tries 12, 13, 15 and 18).
The moderate total yields obtained for compounds 2 + 3
from the reaction of the corresponding arylamides under
Lawesson’s conditions may be explained by two factors:
decomposition of the aryl amides during the refluxing
time and problems in the isolation by flash chromatogra-
phy of these compounds, particulary for pyrroles 2 and
bithiophenes 3 obtained from aryl amides substituted in
position 2, due to the similar polarity of the final products.
Synthesis 2005, No. 2, 199–210 © Thieme Stuttgart · New York

PAPER
Competition between Thienylpyrrole and Bithiophene Formation
201
Table 2 Yields Obtained in the Synthesis of Pyrroles 2 and Bithiophenes 3 from Aryl-4-(2¢-thienyl)-4-oxobutanamides 1a–v
Entry
R
Reaction
Compound
Yield (%)
Compound
Yield (%)
time (min)
2
3
1
2
H
15
20
15
15
15
15
30
20
15
20
15
30
30
15
15
30
25
15
25
15
15
a
b
c
d
e
f
58
55
16
33
32
24
49
3
a
b
c
d
e
f
9
–
1-naphthyl
2-OMe
4-OMe
2,4-diOMe
3,5-diOMe
3,4,5-triOMe
2-OH
3
1427
14
12
–
4
5
6
7
g
h
i
g
h
i
–
8
–
9
2-Me
35
30
58
16
24
22
6
16
17
8
10
11
12
13
14
15
16
17
18
19
20
21
2-F
j
j
4-F
l
l
2-Cl
m
n
o
p
q
r
s
m
n
o
p
q
r
s
21
31
15
46
7
3-Cl
4-Cl
2-Br
4-Br
34
24
8
2,4-diBr
2-I
15
55
21
32
19
3-NO2
4-CO2Me
4-CN
t
26
37
32
t
u
v
u
v
Reflux of 4-methoxyphenyl-4-(2¢-thienyl)-4-oxobutana-
mide (1d) in toluene for 9 hours without LR, resulted in
recovery of unchanged amide 1d.
A plausible mechanism for the formation of five-mem-
bered heterocycles pyrroles and/or thiophenes from sec-
ondary amides has already been proposed.33
In summary, the synthesis of 1-aryl-2-(2¢-thienyl)pyrroles
2 and 1-arylamino-2,2¢-bithiophenes 3 is reported for the
first time from aryl-4-(2¢-thienyl)-4-oxobutanamides 1a–
v through the combination of Friedel–Crafts and Lawes-
son reactions. If suitable aryl-4-(2¢-thienyl)-4-oxobutana-
mides were synthesized, the synthesis of a large range of
1-aryl-2-(2¢-thienyl)pyrroles 2 and 1-arylamino-2,2¢-
bithiophenes 3 would be possible.
Scheme 2
1-Aryl-2-(2¢-thienyl)pyrroles 2 and 1-arylamino-2,2¢-
bithiophenes 3 have been prepared from aryl-4-(2¢-thie-
nyl)-4-oxobutanamides 1. 1-Aryl-2-(2¢-thienyl)pyrroles
were the major products, except in the cases of 2 or 3-ha-
loaryl-4-(2¢-thienyl)-4-oxobutanamides 1m,n,p,s.
The yield of 1-(4¢¢-fluorophenyl)-2-(2¢-thienyl)pyrrole
(2l) dropped from 58–26% [and no 5-(4¢¢-fluoroanilino)-
2,2¢-bithiophene (3l) was isolated], when 0.5 equivalents
of LR was used in this reaction.
Synthesis 2005, No. 2, 199–210 © Thieme Stuttgart · New York

202
M. M. M. Raposo et al.
PAPER
Anal. Calcd for C18H15NO2S: C, 69.78; H, 5.08; N, 4.53; S, 10.70.
Found: C, 69.89; H, 4.85; N, 4.53; S, 10.37.
The thienylpyrroles
bithiophenes 3 described above could find application as
2
and the 5-arylamino-2,2¢-
precursors for non-linear optic materials.
2-Methoxyphenyl-4-(2¢-thienyl)-4-oxobutanamide (1c)
Beige solid (yield: 46%); mp 106.3–108.0 °C. Recrystallization
from EtOH–PE (1:1) gave a beige solid; mp 110.4–111.7 °C.
IR (Nujol): 3406 (NH), 1686 (C=O), 1659 (C=O) cm–1.
1H NMR (acetone-d6): d = 2.91 (t, J = 6.3 Hz, 2 H, CH2), 3.39 (t,
J = 6.3 Hz, 2 H, CH2), 3.90 (s, 3 H, OCH3), 6.87–6.95 (m, 1 H, 5¢¢-
H), 7.00–7.08 (m, 2 H, 3¢¢-H, 4¢¢-H), 7.24–7.30 (m, 1 H, 4¢-H), 7.92
(dd, J = 4.8, 1.2 Hz, 1 H, 5¢-H), 8.00 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H),
8.34 (br d, J = 8.1 Hz, 1 H, 6¢¢-H), 8.66 (br s, 1 H, NH).
1H NMR and 13C NMR spectra were obtained on a Varian Unity
Plus Spectrometer at 300 MHz and 75.4 MHz, respectively, using
the solvent peak as internal reference. The solvents are indicated in
parenthesis before the chemical shift values (d relative to TMS).
Melting points were determined on a Gallenkamp apparatus and are
uncorrected. IR spectra were recorded on a Perkin Elmer 1600 FTIR
spectrophotometer. EI mass spectra EI (70 eV) and HRMS were run
on a Unicam GC-MS 120. Elemental analysis was carried out on a
Leco CHNS-932. Column chromatography was performed on
Merck silica gel 60 (Art 9385). Petroleum ether (PE) refers to the
fraction with boiling point range of 40–60 °C.
13C NMR (CDCl3): d = 31.5, 34.6, 56.1, 111.2, 120.7, 121.2, 124.1,
125.2, 128.0, 129.3, 133.2, 134.4, 145.0, 170.8, 192.3.
Anal. Calcd for C15H15NO3S: C, 62.29; H, 5.19; N, 4.84; S, 11.10.
Found: C, 62.08; H, 5.34; N, 4.88; S, 10.92.
The phenyl amines were purchased from Aldrich and Merck and
were used as received. The synthesis of amides 1d,e has been de-
scribed elsewhere.27
3¢¢,5¢¢-Dimethoxyphenyl-4-(2¢-thienyl)-4-oxobutanamide (1f)
Beige solid (yield: 56%); mp 142.3–146.7 °C. Recrystallization
from EtOH–PE (1:1) gave a beige solid; mp 156.8–157.4 °C.
IR (Nujol): 3371 (NH), 1687 (C=O), 1661 (C=O) cm–1.
Compounds 1–3 were completely characterized by elemental anal-
ysis and/or HRMS, 1H and 13C spectroscopy and IR spectroscopy.
Synthesis of Amides 1a–c and 1f–v; General procedure
DCC–BtOH–CH2Cl2 Method:27 1,3-Dicyclohexylcarbodiimide
(DCC) (1.50 g, 7.10 mmol) and 1-hydroxybenzotriazole (BtOH)
(1.10 g, 7.10 mmol) were added to a stirred solution of 4-oxo-(2-
thienyl)butanoic acid (1.00 g, 5.40 mmol) in CH2Cl2 (30 mL) at 0
°C. The mixture was stirred for 30 min at r.t. after which the amine
(5.40 mmol) was added and the mixture was stirred during 7 d. The
by-product formed, dicyclohexylurea (DCU), was separated by fil-
tration affording a pale brown solution. This organic solution was
extracted with a solution of citric acid (5%) (3 × 25 mL), a solution
of NaHCO3 (5%) (3 × 25 mL), dried (MgSO4) and evaporated to
give an oily brown residue. Flash chromatography on silica gel with
increasing amounts of Et2O in PE as eluent gave the pure amides
1a–c and 1f–v.
1H NMR (CDCl3): d = 2.80 (t, J = 6.6 Hz, 2 H, CH2), 3.41 (t, J =
6.6 Hz, 2 H, CH2), 3.78 (s, 6 H, 2 × OCH3), 6.23 (t, J = 2.1 Hz, 1 H,
4¢¢-H), 6.78 (d, J = 2.1 Hz, 2 H, 2¢¢-H, 6¢¢-H), 7.13–7.19 (m, 1 H, 4¢-
H), 7.65 (br s, 1 H, NH), 7.67 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.80
(dd, J = 3.9, 1.2 Hz, 1 H, 3¢-H).
13C NMR (DMSO-d6): d = 30.3, 33.4, 55.0, 95.0, 97.2, 128.8,
133.2, 134.6, 141.0, 143.5, 160.5, 170.3, 192.0.
Anal. Calcd for C16H17NO4S: C, 60.18; H, 5.33; N, 4.39; S, 10.05.
Found: C, 60.05; H, 5.47; N, 4.42; S, 10.19.
3¢¢,4¢¢,5¢¢-Trimethoxyphenyl-4-(2¢-thienyl)-4-oxobutanamide
(1g)
Brown solid (yield: 49%); mp 181.5–183.4 °C. Recrystallization
from EtOH–PE (1:1) gave a pale brown solid; mp 182.2–183.4 °C.
Phenyl-4-(2¢-thienyl)-4-oxobutanamide (1a)
Colorless solid (yield: 42%); mp 153.2–155.0 °C. Recrystallization
from EtOH–PE (1:1) gave a colorless solid; mp 156.1–157.3 °C.
IR (Nujol): 3352 (NH), 1689 (C=O), 1656 (C=O) cm–1.
1H NMR (CDCl3): d = 2.82 (t, J = 6.3 Hz, 2 H, CH2), 3.42 (t, J =
6.3 Hz, 2 H, CH2), 7.10 (br t, J = 7.5 Hz, 1 H, Ar-H), 7.14–7.18 (m,
1 H, 4¢-H), 7.32 (br t, J = 7.5 Hz, 2 H, 2 × Ar-H), 7.53 (br d, J = 7.5
Hz, 2 H, 2 × Ar-H), 7.67 (dd, J = 4.8, 1.2 Hz, 1 H, 5¢-H), 7.70 (br s,
1 H, NH), 7.81 (dd, J = 3.3, 1.2 Hz, 1 H, 3¢-H).
IR (Nujol): 3336 (NH), 1683 (C=O), 1652 (C=O) cm–1.
1H NMR (CDCl3): d = 2.80 (t, J = 6.6 Hz, 2 H, CH2), 3.42 (t, J =
6.6 Hz, 2 H, CH2), 3.80 (s, 3 H, OCH3), 3.84 (s, 6 H, 2 × OCH3),
6.84 (br s, 2 H, 2¢¢-H, 6¢¢-H), 7.15–7.18 (m, 1 H, 4¢-H), 7.68 (dd, J =
4.9, 1.2 Hz, 1 H, 5¢-H), 7.75 (br s, 1 H, NH), 7.81 (dd, J = 4.0, 1.2
Hz, 1 H, 3¢-H).
13C NMR (CDCl3): d = 31.2, 34.4, 55.9, 60.9, 97.1, 128.3, 132.5,
134.1, 134.3, 143.3, 153.1, 170.2, 192.3.
Anal. Calcd for C17H19NO5S: C, 58.44; H, 5.44; N, 4.01; S, 9.18.
Found: C, 58.27; H, 5.70; N, 3.88; S, 9.11.
13C NMR (CDCl3): d = 31.4, 34.6, 119.7, 124.2, 128.2, 128.9,
132.4, 134.0, 137.8, 150.0, 170.1, 192.0.
Anal. Calcd for C14H13NO2S: C, 64.85; H, 5.02; N, 5.40; S, 12.38.
Found: C, 65.14; H, 5.26; N, 5.52; S, 12.20.
2¢¢-Hydroxyphenyl-4-(2¢-thienyl)-4-oxobutanamide (1h)
Beige solid (yield: 54%); mp 133.2–135.3 °C. Recrystallization
from EtOH–PE (1:1) gave a colorless solid; mp 139.0–140.0 °C.
1-Naphthyl-4-(2¢-thienyl)-4-oxobutanamide (1b)
Pale gray solid (yield: 20%); mp 164.9–166.3 °C. Recrystallization
from EtOH gave a pale gray solid; mp 168.8–169.8 °C.
IR (Nujol): 3332 (NH), 3300–3120 (OH), 1659 (C=O), 1634 (C=O)
cm–1.
1H NMR (acetone-d6): d = 2.97 (t, J = 6.6 Hz, 2 H, CH2), 3.45 (t,
J = 6.6 Hz, 2 H, CH2), 6.85 (dt, J = 8.1, 1.5 Hz, 1 H, 5¢¢-H), 6.93 (dd,
J = 8.1, 1.5 Hz, 1 H, 3¢¢-H), 7.05 (dt, J = 8.1, 1.5 Hz, 1 H, 4¢¢-H),
7.26–7.31 (m, 1 H, 4¢-H), 7.52 (dd, J = 8.1, 1.5 Hz, 1 H, 6¢¢-H), 7.93
(dd, J = 4.8, 1.2 Hz, 1 H, 5¢-H), 8.02 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H),
9.30 (br s, 1 H, NH).
IR (Nujol): 3275 (NH), 1660 (C=O, br) cm–1.
1H NMR (acetone-d6): d = 3.05 (t, J = 6.6 Hz, 2 H, CH2), 3.47 (t,
J = 6.6 Hz, 2 H, CH2), 7.25–7.31 (m, 1 H, 4¢-H), 7.46–7.60 (m, 3 H,
3 × Ar-H), 7.76 (br d, J = 8.1 Hz, 1 H, Ar-H), 7.90–8.00 (m, 3 H, 5¢-
H, 2 × Ar-H), 8.02 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 8.21–8.29 (m, 1
H, Ar-H), 9.34 (br s, 1 H, NH).
13C NMR (DMSO-d6): d = 29.9, 33.8, 121.6, 122.9, 125.1, 125.6,
125.8, 126.0, 127.8, 128.1, 128.8, 133.3, 133.7, 134.6, 143.6, 170.9,
192.2.
13C NMR (DMSO-d6): d = 30.1, 33.8, 115.8, 119.1, 122.3, 124.7,
126.5, 128.9, 133.4, 134.7, 143.6, 147.8, 170.9, 192.2.
Anal. Calcd for C14H13NO3S: C, 61.08; H, 4.73; N, 5.09; S, 11.65.
Found: C, 60.96; H, 4.93; N, 5.02; S, 11.44.
Synthesis 2005, No. 2, 199–210 © Thieme Stuttgart · New York

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Competition between Thienylpyrrole and Bithiophene Formation
203
2¢¢-Methylphenyl-4-(2¢-thienyl)-4-oxobutanamide (1i)
Beige solid (yield: 51%); mp 145.0–145.8 °C. Recrystallization
from EtOH–PE (1:1) gave a beige solid; mp 151.0–151.8 °C.
IR (Nujol): 3257 (NH), 3087, 1661 (C=O), 1651 (C=O) cm–1.
1H NMR (acetone-d6): d = 2.32 (s, 3 H, CH3), 2.90 (t, J = 6.7 Hz, 2
H, CH2), 3.40 (t, J = 6.7 Hz, 2 H, CH2), 7.06 (br t, J = 7.2 Hz, 1 H,
5¢¢-H), 7.13–7.26 (m, 2 H, 3¢¢-H, 4¢¢-H), 7.24–7.29 (m, 1 H, 4¢-H),
7.70–7.76 (m, 1 H, 6¢¢-H), 7.92 (dd, J = 4.5, 1.2 Hz, 1 H, 5¢-H), 8.00
(dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 8.65 (br s, 1 H, NH).
1H NMR (acetone-d6): d = 2.86 (t, J = 6.6 Hz, 2 H, CH2), 3.39 (t,
J = 6.6 Hz, 2 H, CH2), 6.96–7.11 (m, 1 H, 4¢¢-H), 7.25–7.30 (m, 1
H, 4¢-H), 7.33 (t, J = 7.8 Hz, 1 H, 5¢¢-H), 7.48–7.54 (m, 1 H, 6¢¢-H),
7.92 (dd, J = 5.0, 1.2 Hz, 1 H, 5¢-H), 7.94 (t, J = 2.1 Hz, 1 H, 2¢¢-H),
8.00 (dd, J = 3.9, 1.2 Hz, 1 H, 3¢-H), 9.50 (br s, 1 H, NH).
Anal. Calcd for C14H12ClNO2S: C, 57.24; H, 4.09; N, 4.77; S, 10.92.
Found: C, 57.51; H, 4.25; N, 4.80; S, 10.85.
4¢¢-Chlorophenyl-4-(2¢-thienyl)-4-oxobutanamide (1o)
Beige solid (yield: 22%); mp 169.2–171.0 °C. Recrystallization
from EtOH–PE (1:1) gave a beige solid; mp 152.4–153.5 °C.
IR (Nujol): 3357 (NH), 1698 (C=O), 1652 (C=O) cm–1.
1H NMR (acetone-d6): d = 2.85 (t, J = 6.6 Hz, 2 H, CH2), 3.38 (t,
J = 6.6 Hz, 2 H, CH2), 7.24–7.28 (m, 1 H, 4¢-H), 7.33 (d, J = 9.0 Hz,
2 H, 2¢¢-H, 6¢¢-H), 7.72 (d, J = 9.0 Hz, 2 H, 3¢¢-H, 5¢¢-H), 7.91 (dd,
J = 4.8, 1.2 Hz, 1 H, 5¢-H), 7.99 (dd, J = 3.9, 1.2 Hz, 1 H, 3¢-H), 9.40
(br s, 1 H, NH).
13C NMR (DMSO-d6): d = 18.0, 29.9, 35.9, 125.2, 125.2, 126.0,
129.0, 130.4, 131.9, 133.4, 134.7, 136.5, 143.7, 170.4, 192.3.
Anal. Calcd for C15H15NO2S: C, 65.92; H, 5.49; N, 5.13; S, 11.74.
Found: C, 65.67; H, 5.59; N, 5.14; S, 11.91.
2¢¢-Fluorophenyl-4-(2¢-thienyl)-4-oxobutanamide (1j)
Beige solid (yield: 73%); mp 127.4–128.6 °C. Recrystallization
from EtOH–PE (1:1) gave a colorless solid; mp 126.0–127.6 °C.
Anal. Calcd for C14H12ClNO2S: C, 57.24; H, 4.09; N, 4.77; S, 10.92.
Found: C, 57.12; H, 4.33; N, 4.69; S, 10.63.
IR (Nujol): 3376 (NH), 1694 (C=O), 1652 (C=O) cm–1.
1H NMR (CDCl3): d = 2.85 (t, J = 6.3 Hz, 2 H, CH2), 3.45 (t, J =
6.3 Hz, 2 H, CH2), 7.00–7.12 (m, 3 H, 3 × Ar-H), 7.12–7.17 (m, 1
H, 4¢-H), 7.14–7.18 (dd, J = 4.8, 1.2 Hz, 1 H, 5¢-H), 7.69 (br s, 1 H,
NH), 7.81 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 8.29 (m, 1 H, Ar-H).
2¢¢-Bromophenyl-4-(2¢-thienyl)-4-oxobutanamide (1p)
Brown solid (yield: 53%); mp 114.0–115.7 °C. Recrystallization
from EtOH–PE (1:1) gave a beige solid; mp 121.6–123.5 °C.
IR (Nujol): 3281 (NH), 1665 (C=O, broad) cm–1.
Anal. Calcd for C14H12FNO2S: C, 60.65; H, 4.33; N, 5.05; S, 11.55.
Found: C, 60.50; H, 4.45; N, 5.06; S, 11.41.
1H NMR (CDCl3): d = 2.90 (t, J = 7.0 Hz, 2 H, CH2), 3.42 (t, J =
7.0 Hz, 2 H, CH2), 6.98 (dt, J = 7.8, 1.5 Hz, 1 H, 5¢¢-H), 7.13–7.18
(m, 1 H, 4¢-H), 7.30 (dt, J = 7.8, 1.5 Hz, 1 H, 4¢¢-H), 7.54 (dd, J =
7.8, 1.5 Hz, 1 H, 6¢¢-H), 7.67 (dd, J = 4.8, 1.2 Hz, 1 H, 5¢-H), 7.82
(dd, J = 3.3, 1.2 Hz, 1 H, 3¢-H), 7.93 (br s, 1 H, NH), 8.32 (br d, J =
7.8 Hz, 1 H, 3¢¢-H).
4¢¢-Fluorophenyl-4-(2¢-thienyl)-4-oxobutanamide (1l)
Colorless solid (yield: 41%); mp 144.0–145.3 °C. Recrystallization
from Et2O gave a colorless solid; mp 153.7–155.2 °C.
IR (Nujol): 3357 (NH), 1694 (C=O), 1658 (C=O) cm–1.
1H NMR (CDCl3): d = 2.81 (t, J = 6.6 Hz, 2 H, CH2), 3.42 (t, J =
6.6 Hz, 2 H, CH2), 7.01 (t, J = 8.7 Hz, 2 H, 3¢¢-H, 5¢¢-H), 7.14–7.18
(m, 1 H, 4¢-H), 7.48 (dd, J = 8.6, 4.8 Hz, 2 H, 2¢¢-H, 6¢¢-H), 7.68 (dd,
J = 4.7, 1.2 Hz, 1 H, 5¢-H), 7.78 (br s, 1 H, NH), 7.81 (dd, J = 3.4,
1.2 Hz, 1 H, 3¢-H).
13C NMR (CDCl3): d = 31.4, 34.3, 113.3, 121.9, 125.1, 128.2,
128.3, 132.2, 132.3, 133.9, 135.6, 143.4, 170.1, 191.4.
Anal. Calcd for C14H12BrNO2S: C, 49.71; H, 3.55; N, 4.14; S, 9.49.
Found: C, 49.61; H, 3.45; N, 4.18; S, 9.17.
13C NMR (acetone-d6): d = 31.1, 34.4, 115.6, 115.9 (d, J = 22 Hz,
C3¢¢, C5¢¢), 121.6, 121.6 (d, J = 8 Hz, C2¢¢, C6¢¢), 129.2, 133.3,
134.5, 136.7, 137.2, 144.8, 145.5, 157.7, 160.9 (d, J = 238 Hz, C4¢¢),
171.0, 192.4.
4¢¢-Bromophenyl-4-(2¢-thienyl)-4-oxobutanamide (1q)
Beige solid (yield: 30%); mp 168.0–170.0 °C. Recrystallization
from EtOH–PE (1:1) gave a beige solid; mp 176.0–178.0 °C.
IR (Nujol): 3359 (NH), 1698 (C=O), 1654 (C=O) cm–1.
1H NMR (acetone-d6): d = 2.81 (t, J = 6.6 Hz, 2 H, CH2), 3.37 (t,
J = 6.6 Hz, 2 H, CH2), 7.24–7.28 (m, 1 H, 4¢-H), 7.46 (d, J = 9.0 Hz,
2 H, 2¢¢-H, 6¢¢-H), 7.65 (d, J = 9.0 Hz, 2 H, 3¢¢-H, 5¢¢-H), 7.91 (dd,
J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.98 (dd, J = 3.8 Hz, 1.2 Hz, 1 H, 3¢-H),
9.43 (br s, 1 H, NH).
Anal. Calcd for C14H12FNO2S: C, 60.49; H, 4.48; N, 5.07; S, 11.59.
Found: 60.64; H, 4.33; N, 5.05; S, 11.57.
2¢¢-Chlorophenyl-4-(2¢-thienyl)-4-oxobutanamide (1m)
Brown solid (yield: 53%); mp 117.0–118.3 °C. Recrystallization
from EtOH–PE (1:1) gave a beige solid; mp 123.9–125.0 °C.
Anal. Calcd for C14H12BrNO2S: C, 49.71; H, 3.55; N, 4.14; S, 9.49.
Found: C, 49.56; H, 3.71; N, 4.17; S, 9.59.
IR (Nujol): 3313 (NH), 1667 (C=O, br) cm–1.
1H NMR (acetone-d6): d = 2.97 (t, J = 6.6 Hz, 2 H, CH2), 3.42 (t,
J = 6.6 Hz, 2 H, CH2), 7.14 (dt, J = 8.1, 1.5 Hz, 1 H, 4¢¢-H), 7.25–
7.29 (m, 1 H, 4¢-H), 7.33 (dt, J = 8.1, 1.5 Hz, 1 H, 5¢¢-H), 7.47 (dd,
J = 8.1, 1.5 Hz, 1 H, 3¢¢-H), 7.93 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H),
8.01 (dd, J = 3.8, 1.2 Hz, 1 H, 3¢-H), 8.22 (dd, J = 8.1, 1.2 Hz, 1 H,
6¢¢-H), 8.78 (br s, 1 H, NH).
2¢¢,4¢¢-Dibromophenyl-4-(2¢-thienyl)-4-oxobutanamide (1r)
Pale brown solid (yield: 26%); mp 146.4–149.0 °C. Recrystalliza-
tion from EtOH gave a beige solid; mp 156.2–156.6 °C.
IR (Nujol): 3382 (NH), 1701 (C=O), 1659 (C=O) cm–1.
1H NMR (CDCl3): d = 2.89 (t, J = 6.6 Hz, 2 H, CH2), 3.42 (t, J =
6.6 Hz, 2 H, CH2), 7.15–7.18 (m, 1 H, 4¢-H), 7.42 (dd, J = 8.7, 2.4
Hz, 1 H, 5¢¢-H), 7.66–7.71 (m, 2 H, 5¢-H, 3¢¢-H), 7.82 (dd, J = 3.9,
1.2 Hz, 1 H, 3¢-H), 7.93 (br s, 1 H, NH), 8.25 (d, J = 9 Hz, 1 H, 6¢¢-
H).
13C NMR (DMSO-d6): d = 29.7, 33.6, 126.0, 126.2, 127.3, 128.7,
129.4, 133.2, 134.6, 135.0, 139.4, 143.5, 170.6, 191.9.
Anal. Calcd for C14H12ClNO2S: C, 57.24; H, 4.09; N, 4.77; S, 10.92.
Found: C, 57.07; H, 4.33; N, 4.78; S, 10.84.
13C NMR (CDCl3): d = 31.4, 34.3, 113.7, 116.6, 122.8, 128.2,
3¢¢-Chlorophenyl-4-(2¢-thienyl)-4-oxobutanamide (1n)
Beige solid (yield: 23%); mp 126.0–129.0 °C. Recrystallization
from EtOH–PE (1:1) gave a beige solid; mp 166.6–169.4 °C.
IR (Nujol): 3353 (NH), 1703 (C=O), 1661 (C=O) cm–1.
131.3, 132.3, 134.0, 134.4, 134.9, 143.3, 170.2, 191.3.
Anal. Calcd for C14H11Br2NO2S: C, 40.30; H, 2.64; N, 3.36; S, 7.68.
Found: C, 40.60; H, 2.71; N, 3.38; S, 7.55.
Synthesis 2005, No. 2, 199–210 © Thieme Stuttgart · New York

204
M. M. M. Raposo et al.
PAPER
2¢¢-Iodophenyl-4-(2¢-thienyl)-4-oxobutanamide (1s)
Beige solid (yield: 55%); mp 124.0–125.2 °C. Recrystallization
from EtOH gave a beige solid; mp 129.2–131.0 °C.
IR (Nujol): 3282 (NH), 1660 (C=O), 1652 (C=O) cm–1.
13C NMR (acetone-d6): d = 31.3, 34.2, 106.6, 119.5, 119.9, 129.2,
133.3, 133.9, 134.5, 144.4, 144.8, 171.7, 192.1.
Anal. Calcd for C15H12N2O2S: C, 63.54; H, 4.44; N, 9.78; S, 11.51.
Found: C, 63.35; H, 4.22; N, 9.85; S, 11.26.
1H NMR (CDCl3): d = 2.90 (t, J = 6.7 Hz, 2 H, CH2), 3.41 (t, J =
6.6 Hz, 2 H, CH2), 6.85 (dt, J = 7.8, 1.5 Hz, 1 H, 4¢¢-H), 7.15–7.18
(m, 1 H, 4¢-H), 7.33 (dt, J = 7.8, 1.5 Hz, 1 H, 5¢¢-H), 7.67 (dd, J =
4.8, 1.2 Hz, 1 H, 5¢-H), 7.71 (br s, 1 H, NH), 7.78 (dt, J = 7.8 1.5 Hz,
1 H, 3¢¢-H), 7.82 (dd, J = 3.9, 1.2 Hz, 1 H, 3¢-H), 8.20 (br d, J = 7.8
Hz, 1 H, 6¢¢-H).
Reaction of Amides 1a–v with Lawesson’s Reagent (LR);
General Procedure
A mixture of the Lawesson reagent (0.93 g, 2.30 mmol) and the
amides 1a–v (2.30 mmol) was heated at reflux in toluene (12 mL)
for the time indicated in Table 2. The mixture was cooled and the
solvent was evaporated under reduced pressure to give the crude
mixture of aryl pyrroles 2 and/or bithiophenes 3, which was purified
by flash chromatography on silica gel with increasing amounts of
Et2O in PE as eluent.
Anal. Calcd for C14H12INO2S: 43.64; H, 3.12; N, 3.64; S, 8.33.
Found: C, 43.91; H, 3.43; N, 3.69; S, 8.10.
3¢¢-Nitrophenyl-4-(2¢-thienyl)-4-oxobutanamide (1t)
The pure amide precipitated as a brown solid after addition of ace-
tone to the crude mixture. Evaporation of the filtrate under reduce
pressure gave more crude amide which was submitted to flash chro-
mathography [Et2O–PE, 2:8 → 5:5] to give another crop of pure
amide as a colorless solid; global yield: 24%; mp 143.7–145.5 °C.
Recrystallization from EtOH–PE (1:1) gave a colorless solid; mp
159.2–160.1 °C.
1-Phenyl-2-(2¢-thienyl)pyrrole (2a) and 5-Anilino-2,2¢-bithio-
phene (3a)
Treatment of amide 1a with Lawesson’s reagent gave a mixture of
1-phenyl-2-(2¢-thienyl)pyrrole (2a) and 5-anilino-2,2¢-bithiophene
(3a). The first component eluted was 1-phenyl-2-(2¢-thienyl)pyrrole
(2a) as a beige solid (yield: 58%); mp 96.4–97.6 °C [Et2O–PE
(1:2)].
IR (Nujol): 3333 (NH), 1698 (C=O), 1646 (C=O) cm–1.
IR (Nujol): 1593, 1560, 1496, 1428, 1403, 1353, 1325, 1316, 1303,
1227, 1161, 1093, 1081, 1072, 1034, 976, 917, 841, 792, 776, 727,
705, 697 cm–1.
1H NMR (CDCl3): d = 6.32–6.36 (m, 1 H, 4-H), 6.50 (dd, J = 4.2,
1.8 Hz, 1 H, 3-H), 6.57 (dd, J = 3.8, 1.2 Hz, 1 H, 3¢-H), 6.84–6.88
(m, 1 H, 4¢-H), 6.89–6.92 (m, 1 H, 5-H), 7.12 (dd, J = 5.4, 1.2 Hz,
1 H, 5¢-H), 7.25–7.30 (m, 2 H, 2 × Ar-H), 7.34–7.42 (m, 3 H, 3 ×
Ar-H).
1H NMR (acetone-d6): d = 2.76 (t, J = 6.7 Hz, 2 H, CH2), 3.43 (t,
J = 6.7 Hz, 2 H, CH2), 7.27–7.30 (m, 1 H, 4¢-H), 7.63 (t, J = 8.1 Hz,
1 H, 5¢¢-H), 7.92–8.04 (m, 4 H, 4¢¢-H, 6¢¢-H, 3¢-H, 5¢-H), 8.76 (t, J =
2.1 Hz, 1 H, 2¢¢-H), 9.75 (br s, 1 H, NH).
13C NMR (DMSO-d6): d = 30.3, 33.3, 112.9, 117.5, 124.8, 128.8,
130.2, 133.3, 134.7, 140.4, 143.4, 148.1, 171.1, 191.9.
Anal. Calcd for C14H12N2O4S: C, 55.29; H, 4.23; N, 9.00; S, 10.42.
Found: C, 55.15; H, 3.95; N, 9.21; S, 10.54.
13C NMR (CHCl3): d = 110.9, 109.1, 124.1, 124.4, 124.8, 126.5,
126.9, 127.4, 128.9, 134.9, 140.0.
MS (EI): m/z (%) = 225 (100) [M+].
4¢¢-Methyloxycarbonylphenyl-4-(2¢-thienyl)-4-oxobutanamide
(1u)
Beige solid (yield: 35%); mp 128.6–130.5 °C. Recrystallization
HRMS (EI): m/z calcd for C14H11NS: 225.0612; found: 225.0611.
from EtOH–PE (1:1) gave a beige solid; mp 138.4–139.7 °C.
The second component eluted was 5-anilino-2,2¢-bithiophene (3a)
as a pale green solid (yield: 9%); mp 81.0–83.0 °C [Et2O–PE (1:2)].
IR (Nujol): 3356 (NH), 1716 (C=O), 1697 (C=O), 1652 (C=O)
cm–1.
IR (Nujol): 3367 (NH), 2925, 1598, 1556, 1515, 1498, 1434, 1305,
1258, 1233, 1173, 1150, 1077, 1049, 886, 834, 791, 747, 690, 685
cm–1.
1H NMR (CDCl3): d = 6.64 (d, J = 3.9 Hz, 1 H, 4-H), 6.89 (br t, J =
6.6 Hz, 1 H, 4¢¢-H), 6.93–6.97 (m, 3 H, 3-H, 2 × Ar-H), 6.98–7.00
(m, 1 H, 4¢-H), 7.09 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 7.18 (dd, J =
4.5, 1.2 Hz, 1 H, 5¢-H), 7.22–7.32 (m, 2 H, 2 × Ar-H).
13C NMR (acetone-d6): d = 115.7, 115.7, 116.3, 116.4, 120.6, 123.2,
123.3, 124.4, 128.7, 130.1.
MS (EI): m/z (%) = 257 (100) [M+].
1H NMR (CDCl3): d = 2.84 (t, J = 7.0 Hz, 2 H, CH2), 3.42 (t, J =
7.0 Hz, 2 H, CH2), 3.90 (s, 3 H, OCH3), 7.14–7.19 (m, 1 H, 4¢-H),
7.62 (d, J = 8.7 Hz, 2 H, 2 × Ar-H), 7.69 (dd, J = 5.3, 1.2 Hz, 1 H,
5¢-H), 7.82 (dd, J = 3.5, 1.2 Hz, 1 H, 3¢-H), 8.00 (m, 3 H, NH, 2 ×
Ar-H).
13C NMR (DMSO-d6): d = 30.5, 33.5, 52.0, 118.4, 123.8, 129.1,
130.5, 133.4, 134.8, 143.6, 143.8, 166.0, 171.1, 192.1.
Anal. Calcd for C16H15NO4S: C, 60.56; H, 4.73; N, 4.42; S, 10.11.
Found: 60.66; H, 4.99; N, 4.44; S, 10.14.
HRMS (EI): m/z calcd for C14H11NS2: 257.0333; found: 257.0336.
4¢¢-Cyanophenyl-4-(2¢-thienyl)-4-oxobutanamide (1v)
The pure amide precipitated as a brown solid after addition of ace-
tone to the crude mixture. Evaporation of the filtrate under reduce
pressure gave the crude amide which was submitted to flash chro-
mathography [Et2O–PE (3:7 → 1:0) and EtOAc–PE (5:5)] to give
more pure amide as a colorless solid; global yield: 31%; mp 206.9–
208.1 °C. Recrystallization from EtOH gave a colorless solid; mp
206.7–207.8 °C.
1-Naphthyl-2-(2¢-thienyl)pyrrole (2b)
Treatment of amide 1b with Lawesson’s reagent gave the crude 1-
naphthyl-2-(2¢-thienyl)pyrrole (2b) which was purified by flash
chromatography; green solid (yield: 55%); mp 111.8–112.7 °C
[Et2O–PE (1:2)].
IR (Nujol): 2921, 1594, 1463, 1375, 1300, 1200, 1169, 1143, 1075,
1001, 843, 780, 711 cm–1.
IR (Nujol): 3341 (NH), 2224 (CN), 1704 (C=O), 1644 (C=O) cm–1.
1H NMR (acetone-d6): d = 6.40–6.45 (m, 1 H, 4-H), 6.46 (dd, J =
3.9, 1.2 Hz, 1 H, 3¢-H), 6.65 (dd, J = 3.8, 1.8 Hz, 1 H, 3-H), 6.70–
6.75 (m, 1 H, 4¢-H), 6.98–7.02 (m, 1 H, 5-H), 7.07 (dd, J = 5.1, 1.2
Hz, 1 H, 5¢-H), 7.27 (br d, J = 8.1 Hz, 1 H, Ar-H), 7.46–7.70 (m, 4
H, 4 × Ar-H), 8.05 (br d, J = 8.1 Hz, 1 H, Ar-H), 8.12 (br d, 1 H, Ar-
H).
1H NMR (CDCl3): d = 2.83 (t, J = 6.3 Hz, 2 H, CH2), 3.43 (t, J =
6.3 Hz, 2 H, CH2), 7.16–7.19 (m, 1 H, 4¢-H), 7.60 (d, J = 8.7 Hz, 2
H, 2 × Ar-H), 7.67 (d, J = 8.7 Hz, 2 H, 2 × Ar-H), 7.70 (dd, J = 5.1,
1.2 Hz, 1 H, 5¢-H), 7.81 (dd, J = 3.5, 1.2 Hz, 1 H, 3¢-H), 8.14 (br s,
1 H, NH).
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Competition between Thienylpyrrole and Bithiophene Formation
205
13C NMR (acetone-d6): d = 110.0, 109.9, 123.6, 124.1, 124.4, 126.3,
126.4, 127.1, 127.5, 127.6, 128.1, 129.0, 130.0, 130.2, 132.6, 135.0,
135.7, 137.7.
The second component eluted was 5-(4¢¢-methoxyanilino)-2,2¢-
bithiophene (3d) as a green solid (yield: 14%); mp 113.0–115.0 °C
[Et2O–PE (1:2)] [lit.27 113.0–115.0 °C].
MS (EI): m/z (%) = 275 (100) [M+].
1-(2¢¢,4¢¢-Dimethoxyphenyl-2-(2¢-thienyl)pyrrole (2e) and 5-
(2¢¢,4¢¢-Dimethoxyanilino)-2,2¢-bithiophene (3e)
HRMS (EI): m/z calcd for C18H13NS: 275.0769; found: 275.0772.
Treatment of amide 1e with Lawesson’s reagent gave a mixture of
1-(2¢¢,4¢¢-dimethoxyphenyl-2-(2¢-thienyl)pyrrole (2e) and 5-(2¢¢,4¢¢-
dimethoxyanilino)-2,2¢-bithiophene (3e). The first component elut-
ed was 1-(2¢¢,4¢¢-dimethoxyphenyl-2-(2¢-thienyl)pyrrole (2e) as a
pale green solid (yield: 32%); mp 107.0–109.0 °C [Et2O–PE (1:2)].
1-(2¢¢-Methoxyphenyl)-2-(2¢-thienyl)pyrrole (2c) and 5-(2¢¢-
Methoxyanilino)-2,2¢-bithiophene (3c)
Treatment of amide 1c with Lawesson’s reagent gave a mixture of
1-(2¢¢-methoxyphenyl)-2-(2¢-thienyl)pyrrole (2c) and 5-(2¢¢-meth-
oxyanilino)-2,2¢-bithiophene (3c). The first component eluted was
1-(2¢¢-methoxyphenyl)-2-(2¢-thienyl)pyrrole (2c) as a pale yellow
solid (yield: 16%); mp 113.6–116.2 °C [Et2O–PE (1:2)].
IR (Nujol): 1611, 1587, 1515, 1464, 1439, 1419, 1302, 1285, 1208,
1159, 1135, 1091, 1044, 1029, 927, 841, 710, 690 cm–1.
1H NMR (acetone-d6): d = 3.70 (s, 3 H, OCH3), 3.90 (s, 3 H, OCH3),
6.20–6.25 (m, 1 H, 4-H), 6.45 (dd, J = 4.2, 1.5 Hz, 1 H, 3-H), 6.62
(dd, J = 9.0, 2.7 Hz, 1 H, 5¢¢-H), 6.66 (dd, J = 3.5, 1.2 Hz, 1 H, 3¢-
H), 6.72 (d, J = 2.7 Hz, 1 H, 3¢¢-H), 6.74–6.77 (m, 1 H, 5-H), 6.86–
6.90 (m, 1 H, 4¢-H), 7.16 (d, J = 9.0 Hz, 1 H, 6¢¢-H), 7.19 (dd, J =
4.9, 1.2 Hz, 1 H, 5¢-H).
13C NMR (CDCl3): d = 55.5, 55.7, 99.6, 104.1, 108.6, 108.7, 122.2,
123.1, 123.2, 124.8, 126.7, 128.8, 129.9, 135.4, 156.5, 160.8.
MS (EI): m/z (%) = 285 (100) [M+].
IR (Nujol): 3098, 2925, 1599, 1565, 1504, 1428, 1404, 1349, 1328,
1310, 1279, 1249, 1235, 1208, 1188, 1179, 1161, 1084, 1021, 981,
943 cm–1.
1H NMR (acetone-d6): d = 3.68 (s, 3 H, OCH3), 6.24–6.29 (m, 1 H,
4-H), 6.46 (dd, J = 3.8, 1.8 Hz, 1 H, 3-H), 6.59 (dd, J = 3.6, 1.2 Hz,
1 H, 3¢-H), 6.84–6.88 (m, 1 H, 4¢-H), 7.04–7.10 (m, 2 H, 5-H, 5¢-H),
7.15–7.22 (m, 2 H, 2 × Ar-H), 7.26 (dd, J = 7.5, 1.5 Hz, 1 H, Ar-H),
7.47 (dt, J = 7.5, 1.5 Hz, 1 H, Ar-H).
13C NMR (acetone-d6): d = 55.9, 109.4, 109.8, 113.4, 121.4, 123.8,
124.2, 125.5, 127.6, 129.2, 130.1, 130.7, 136.4, 156.5.
MS (EI): m/z (%) = 255 (100) [M+].
Anal. Calcd for C16H15NO2S: C, 67.35; H, 5.26; N, 4.91; S, 11.25.
Found: C, 67.36; H, 5.42; N, 4.98; S, 11.25.
The second component eluted was 5-(2¢¢,4¢¢-dimethoxyanilino)-
2,2¢-bithiophene (3e) as a green oil (yield: 8%).
HRMS (EI): m/z calcd for C15H13NOS: 255.0718; found: 255.0719.
The second component eluted was 5-(2¢¢-methoxyanilino)-2,2¢-
bithiophene (3c) as a green oil (yield: 14%).
IR (liquid film): 3372 (NH), 3104, 3071, 2926, 2246, 2067, 1614,
1600, 1565, 1556, 1538, 1505, 1456, 1417, 1283, 1258, 1208, 1158,
1125, 1029, 931, 909, 834, 726, 694, 630 cm–1.
1H NMR (CDCl3): d = 3.79 (s, 3 H, OCH3), 3.89 (s, 3 H, OCH3),
6.44 (dd, J = 8.7, 2.7 Hz, 1 H, 5¢¢-H), 6.52 (d, J = 2.7 Hz, 1 H, 3¢¢-
H), 6.55 (br d, J = 3.6 Hz, 1 H, 4-H), 6.93 (br d, J = 3.6 Hz, 1 H, 3-
H), 6.96–7.01 (m, 1 H, 4¢-H), 7.04 (br d, J = 3.6 Hz, 1 H, 3¢-H), 7.13
(m, 2 H, 5¢-H, 6¢¢-H).
13 C NMR (CDCl3): d = 55.7, 55.7, 99.2, 103.8, 114.3, 115.4, 122.3,
123.2, 127.6, 128.3, 130.0, 138.1, 146.8, 148.4, 154.0.
MS (EI): m/z (%) = 317 (100) [M+].
IR (liquid film): 3397 (NH), 1500, 1525, 1504, 1462, 1243, 1113,
1021, 740, 692 cm–1.
1H NMR (acetone-d6): d = 3.91 (s, 3 H, OCH3), 6.70 (d, J = 3.9 Hz,
1 H, 4-H), 6.84–6.92 (m, 2 H, 2 × Ar-H), 6.99 (dd, J = 9.0, 1.8 Hz,
1 H, Ar-H), 7.05 (m, 2 H, 3-H, 4¢-H), 7.17 (dd, J = 3.6, 1.2 Hz, 1 H,
3-H), 7.24 (dd, J = 9.0, 1.8 Hz, 1 H, Ar-H), 7.36 (dd, J = 5.1, 1.2 Hz,
1 H, 5¢-H).
13C NMR (acetone-d6): d = 56.0, 111.4, 113.8, 117.2, 117.4, 120.5,
121.7, 123.2, 124.4, 128.7, 130.7, 137.8, 138.7, 146.8, 154.0.
MS (EI): m/z (%) = 287 (100) [M+].
HRMS (EI): m/z calcd for C16H15NO2S2: 317.0544; found:
317.0544.
HRMS (EI): m/z for C15H13NOS2: 287.0438; found: 287.0447.
1-(4¢¢-Methoxyphenyl)-2-(2¢-thienyl)pyrrole (2d) and 5-(4¢¢-
Methoxyanilino)-2,2¢-bithiophene (3d)
Treatment of amide 1d with Lawesson’s reagent gave a mixture of
1-(4¢¢-methoxyphenyl)-2-(2¢-thienyl)pyrrole (2d) and 5-(4¢¢-meth-
oxyanilino)-2,2¢-bithiophene (3d). The first component eluted was
1-(4¢-methoxyphenyl)-2-(2¢-thienyl)pyrrole (2d) as a yellow solid
(yield: 33%); mp 83.0–85.0 °C [Et2O–PE (1:2)].
1-(3¢¢,5¢¢-Dimethoxyphenyl)-2-(2¢-thienyl)pyrrole (2f)
Treatment of amide 1f with Lawesson’s reagent gave the crude 1-
(3¢¢,5¢¢-dimethoxiphenyl)-2-(2¢-thienyl)pyrrole (2f) which was puri-
fied by flash chromatography; yellow oil (yield: 24%).
IR (liquid film): 3104, 2958, 2935, 1508, 1476, 1463, 1428, 1322,
1265, 1231, 1205, 1156, 1098, 1064, 1035, 928, 846, 814, 790, 716,
691, 623 cm–1.
1H NMR (CDCl3): d = 3.72 (s, 6 H, 2 × OCH3), 6.28–6.31 (m, 1 H,
4-H), 6.41–6.46 (m, 3 H, 2¢¢-H, 4¢¢-H, 6¢¢-H), 6.48 (dd, J = 3.4, 2.1
Hz, 1 H, 3-H), 6.67 (dd, J = 3.4, 1.2 Hz, 1 H, 3¢-H), 6.87–6.89 (m,
1 H, 4¢-H), 6.91 (dd, J = 3.2, 1.8 Hz, 1 H, 5-H), 7.14 (dd, J = 5.1, 1.2
Hz, 1 H, 5¢-H).
13C NMR (acetone-d6): d = 55.8, 100.2, 105.4, 109.8, 111.8, 125.2,
125.4, 125.9, 127.7, 127.8, 135.7, 142.5, 161.9.
MS (EI): m/z (%) = 285 (100) [M+].
IR (Nujol): 1508, 1480, 1465, 1436, 1412, 1240, 1180, 1122, 1034,
819, 796, 763, 690, 628, 618 cm–1.
1H NMR (CDCl3): d = 3.85 (s, 3 H, OCH3), 6.28–6.32 (m, 1 H, 4-
H), 6.46 (dd, J = 3.6, 1.5 Hz, 1 H, 3-H), 6.59 (dd, J = 3.3, 1.2 Hz, 1
H, 3¢-H), 6.82–6.87 (m, 2 H, 5-H, 4¢-H), 6.90 (d, J = 8.9 Hz, 2 H,
2 × Ar-H), 7.09 (dd, J = 5.2, 1.2 Hz, 1 H, 5¢-H), 7.20 (d, 2 H, 8.9 Hz,
2 × Ar-H).
13C NMR (acetone-d6): d = 55.8, 109.6, 110.8, 115.0, 124.9, 125.1,
125.5, 127.8, 128.4, 128.8, 133.8, 135.9, 160.1.
HRMS (EI): m/z calcd for C16H15NO2S: 285.0823; found:
285.0824.
MS (EI): m/z (%) = 255 (100) [M+].
Anal. Calcd for C15H13NOS: C, 70.57; H, 5.10; N, 5.49; S, 12.57.
Found: C, 70.35; H, 5.22; N, 5.57; S, 12.83.
Synthesis 2005, No. 2, 199–210 © Thieme Stuttgart · New York

206
M. M. M. Raposo et al.
PAPER
1-(3¢¢,4¢¢,5¢¢-Trimethoxyphenyl)-2-(2¢-thienyl)pyrrole (2g)
Treatment of amide 1g with Lawesson’s reagent gave the crude 1-
(3¢¢,4¢¢,5¢¢-trimethoxiphenyl)-2-(2¢-thienyl)pyrrole (2g) which was
purified by flash chromatography; pale green solid (yield: 49%); mp
103.7–104.7 °C [Et2O–PE (1:2)].
7.01 (d, J = 3.6 Hz, 1 H, 3-H), 6.99–7.02 (m, 1 H, 4¢-H), 7.07–7.20
(m, 5 H, 3¢-H, 5¢-H, 3 × Ar-H).
13C NMR (acetone-d6): d = 17.9, 116.0, 116.9, 121.4, 123.2, 123.2,
124.3, 124.9, 126.2, 127.6, 128.4, 128.7, 128.7, 131.5, 138.8.
MS (EI): m/z (%) = 271 (100) [M+].
IR (Nujol): 3104, 3072, 2999, 2937, 1506, 1417, 1365, 1340, 1297,
1266, 1243, 1230, 1180, 1164, 1127, 1063, 1006, 953, 944, 852,
836, 769, 715, 666, 631, 611 cm–1.
1H NMR (acetone-d6): d = 3.79 (s, 9 H, 3 × OCH3), 6.27 (m, 1 H, 4-
H), 6.46 (dd, J = 3.6, 1.7 Hz, 1 H, 3-H), 6.59 (s, 2 H, 2¢¢-H, 6¢¢-H),
6.73 (dd, J = 3.3, 1.2 Hz, 1 H, 3¢-H), 6.94–7.00 (m, 1 H, 4¢-H), 7.00–
7.03 (m, 1 H, 5-H), 7.33 (dd, J = 4.7, 1.2 Hz, 1 H, 5¢-H).
HRMS (EI): m/z calcd for C15H13NS2: 271.0489; found: 271.0494.
1-(2¢¢-Fluorophenyl)-2-(2¢-thienyl)pyrrole (2j) and 5-(2¢¢-Fluo-
roanilino)-2,2¢-bithiophene (3j)
Treatment of amide 1j with Lawesson’s reagent gave a mixture of
1-(2¢¢-fluorophenyl)-2-(2¢-thienyl)pyrrole (2j) and 5-(2¢¢-fluoroa-
nilino)-2,2¢-bithiophene (3j). The first component eluted was 1-(2¢¢-
fluorophenyl)-2-(2¢-thienyl)pyrrole (2j) as a green solid (yield:
30%); mp 64.4–66.0 °C [Et2O–PE (1:2)].
13C NMR (acetone-d6): d = 56.4, 60.6, 105.0, 109.6, 111.3, 125.3,
125.8, 127.8, 127.9, 135.7, 136.4, 138.4, 154.28.
Anal. Calcd for C17H17NO3S: C, 64.75; H, 5.40; N, 4.44; S, 10.17.
Found: C, 64.58; H, 5.54; N, 4.54; S, 10.47.
IR (Nujol): 2924, 1610, 1588, 1455, 1401, 1352, 1328, 1308, 1266,
1227, 1162, 1152, 1114, 1085, 1033, 987, 950, 919, 842, 817, 792,
769, 722, 700, 639 cm–1.
1-(2¢¢-Hydroxyphenyl)-2-(2¢-thienyl)pyrrole (2h)
1H NMR (acetone-d6): d = 6.38–6.34 (m, 1 H, 4-H), 6.50–6.54 (dd,
J = 3.6, 1.5 Hz, 1 H, 3-H), 6.65 (dd, J = 3.8, 1.2 Hz, 1 H, 3¢-H), 6.89–
6.93 (m, 1 H, 4¢-H), 6.94–6.97 (m, 1 H, 5-H), 7.27 (dd, J = 5.1, 1.2
Hz, 1 H, 5¢-H), 7.30–7.38 (m, 2 H, 2 × Ar-H), 7.45 (dt, J = 8.1, 1.8
Hz, 1 H, Ar-H), 7.52–7.60 (m, 1 H, Ar-H).
Treatment of amide 1h with Lawesson’s reagent gave a complex
mixture with several products (TLC). After purification by flash
chromatography it was possible to purify and identify only 1-(2¢¢-
hydroxyphenyl)-2-(2¢-thienyl)pyrrole (2h); pale green solid (yield:
3%); mp 135.8–136.9 °C [Et2O–PE (1:2)].
MS (EI): m/z (%) = 243 (100) [M+].
IR (Nujol): 3510–3290 (OH), 2923, 1585, 1501, 1323, 1306, 1195,
1144, 1080, 1050, 1033, 949, 919, 844, 832, 793, 767, 723, 704, 616
cm–1.
1H NMR (acetone-d6): d = 6.25–6.28 (m, 1 H, 4-H), 6.46–6.48 (m,
1 H, 3-H), 6.66 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.82–6.83 (m, 1 H,
4¢-H), 6.85–6.88 (m, 1 H, 5-H), 6.94 (dt, J = 7.8, 1.5 Hz, 1 H, 5¢¢-
H), 7.07 (dd, J = 8.1, 1.2 Hz, 1 H, 6¢¢-H), 7.15–7.19 (m, 2 H, 5¢-H,
3¢¢-H), 7.34 (dt, J = 7.8, 1.5 Hz, 1 H, 4¢¢-H).
13C NMR (acetone-d6): d = 109.8, 109.6, 117.6, 120.6, 123.8, 124.1,
125.6, 127.7, 130.5, 130.6, 130.6, 136.3, 154.6, 157.4.
MS (EI): m/z (%) = 241 (100) [M+].
HRMS (EI): m/z calcd for C14H10FNS: 243.0518; found: 243.0510.
The second component eluted was 5-(2¢¢-fluoroanilino)-2,2¢-
bithiophene (3j) as a green oil (yield: 17%).
IR (liquid film): 3365 (NH), 3070, 2925, 2853, 1619, 1592, 1562,
1575, 1505, 1478, 1463, 1428, 1325, 1292, 1258, 1242, 1185, 1096,
1035, 920, 836, 805, 745, 694, 693 cm–1.
1H NMR (acetone-d6): d = 6.75 (d, J = 3.6 Hz, 1 H, 4-H), 6.84–6.92
(m, 1 H, Ar-H), 7.07 (d, J = 3.6 Hz, 1 H, 3-H), 7.10–7.17 (m, 3 H,
4¢-H, 2 × Ar-H), 7.20 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 7.29 (dt, J =
8.1, 1.8 Hz, 1 H, Ar-H), 7.39 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.67
(br s, 1 H, NH).
HRMS (EI): m/z calcd for C14H11NOS: 241.0561; found: 241.0560.
MS (EI): m/z (%) = 275 (100) [M+].
1-(2¢¢-Methylphenyl)-2-(2¢-thienyl)pyrrole (2i) and 5-(2¢¢-Meth-
ylanilino)-2,2¢-bithiophene (3i)
HRMS (EI): m/z calcd for C14H10FNS2: 275.0239; found: 275.0236.
Treatment of amide 1i with Lawesson’s reagent gave a mixture of
1-(2¢¢-methylphenyl)-2-(2¢-thienyl)pyrrole (2i) and 5-(2¢¢-methyla-
nilino)-2,2¢-bithiophene (3i). The first component eluted was 1-(2¢¢-
methylphenyl)-2-(2¢-thienyl)pyrrole (2i) as a pale yellow oil (yield:
35%).
1-(4¢¢-Fluorophenyl)-2-(2¢-thienyl)pyrrole (2l) and 1-(4¢¢-Fluo-
rophenyl)-2-(2¢-thienyl)pyrrole (3l)
Treatment of amide 1l with Lawesson’s reagent gave a mixture of
1-(4¢¢-fluorophenyl)-2-(2¢-thienyl)pyrrole (2l) and 5-(4¢¢-fluoroa-
nilino)-2,2¢-bithiophene (3l).
IR (liquid film): 3104, 3071, 2957, 2925, 2858, 1605, 1583, 1497,
1463, 1430, 1405, 1382, 1348, 1326, 1309, 1279, 1227, 1212, 1200,
1168, 1091, 1081, 1014, 917, 844, 823, 766, 715, 692, 616 cm–1.
The first component eluted was 1-(4¢¢-fluorophenyl)-2-(2¢-thie-
nyl)pyrrole (2l); pale yellow solid (yield: 58%); mp 77.7–78.7 °C
[Et2O–PE (1:2)].
1H NMR (CDCl3): d = 1.96 (s, 3 H, CH3), 6.33–6.35 (m, 1 H, 4-H),
6.49 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.54 (dd, J = 3.6, 1.8 Hz, 1 H,
3-H), 6.72–6.73 (m, 1 H, 5-H), 6.78–6.81 (m, 1 H, 4¢-H), 7.01 (dd,
J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.25–7.33 (m, 4 H, 4 × Ar-H).
13C NMR (acetone-d6): d = 17.3, 109.6, 109.9, 123.6, 124.2, 124.7,
127.5, 127.8, 129.0, 129.3, 129.7, 131.5, 136.0, 137.4, 140.2.
IR (Nujol): 1593, 1560, 1519, 1496, 1428, 1403, 1353, 1325, 1316,
1303, 1227, 1161, 1093, 1081, 1072, 1034, 976, 917, 841, 792, 776,
727, 705, 697 cm–1.
1H NMR (acetone-d6): d = 6.29–6.33 (m, 1 H, 4-H), 6.48 (dd, J =
3.8, 1.8 Hz, 1 H, 3-H), 6.65 (dd, J = 3.8, 1.2 Hz, 1 H, 3¢-H), 6.92–
6.96 (m, 1 H, 4¢-H), 6.98–7.01 (m, 1 H, 5-H), 7.26 (t, J = 8.7 Hz, 2
H, 2 × Ar-H), 7.31 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.36 (dd, J = 9.3,
4.8 Hz, 2 H, 2 × Ar-H).
MS (EI): m/z (%) = 239 (100) [M+].
HRMS (EI): m/z calcd for C15H13NS: 239.0769; found: 239.0772.
13C NMR (acetone-d6): d = 110.0, 110.0, 111.5, 116.5, 116.8 (d, J =
9 Hz, C2¢¢, C6¢¢), 135.5, 161.0, 164.2 (d, J = 245 Hz, C4¢¢), 125.3,
125.5, 125.6, 127.9, 128.2, 129.4, 129.5 (d, J = 23 Hz, C3¢¢, C5¢¢).
The second component eluted was 5-(2¢¢-methylanilino)-2,2¢-
bithiophene (3i) as a green oil (yield: 16%).
IR (liquid film): 3399 (NH), 3105, 3069, 2958, 2924, 2854, 1606,
1586, 1521, 1498, 1467, 1446, 1382, 1294, 1260, 1241, 1199, 1159,
1109, 1079, 1048, 836, 778, 747, 693 cm–1.
MS (EI): m/z (%) = 243 (100) [M+].
HRMS (EI): m/z calcd for C14H10FNS: 243.0518; found: 243.0516.
1H NMR (acetone-d6): d = 2.29 (s, 3 H, CH3), 5.41 (br s, 1 H, NH),
6.62 (d, J = 3.6 Hz, 1 H, 4-H), 6.85 (dt, J = 7.2, 1.8 Hz, 1 H, Ar-H),
The second component eluted was 1-(4¢¢-fluorophenyl)-2-(2¢-thie-
nyl)pyrrole (3l) as a green oil (yield: 8%).
Synthesis 2005, No. 2, 199–210 © Thieme Stuttgart · New York

PAPER
Competition between Thienylpyrrole and Bithiophene Formation
207
IR (liquid film): 3377 (NH), 2924, 2728, 1563, 1509, 1407, 1304,
1260, 1226, 1154, 1045, 1019, 819, 769, 722, 689, 615 cm–1.
HRMS (EI): m/z calcd for C14H1035ClNS: 259.0222; found:
259.0226.
1H NMR (acetone-d6): d = 6.62 (d, J = 3.9 Hz, 1 H, 4-H), 7.02–7.14
(m, 6 H, 3¢-H, 4¢-H, 4 × Ar-H), 7.30 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H),
7.36 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.84 (br s, 1 H, NH).
The second component eluted was 5-(3¢¢-chloroanilino)-2,2¢-
bithiophene (3n) as a green solid (yield: 31%); mp 74.7–75.6 °C
[Et2O–PE (1:2)].
MS (EI): m/z (%) = 275 (100) [M+].
IR (liquid film): 3372 (NH), 1595, 1519, 1479, 1301, 1226, 1075,
1049, 990, 836, 790, 769 cm–1.
HRMS (EI): m/z calcd for C14H10FNS2: 275.0239; found: 275.0243.
1H NMR (CDCl3): d = 5.63 (br s, 1 H, NH), 6.69 (d, J = 3.9 Hz, 1
H, 4-H), 6.76–6.80 (m, 1 H, Ar-H), 6.81–6.86 (m, 1 H, Ar-H), 6.90–
6.92 (m, 1 H, Ar-H), 6.99 (d, J = 3.9 Hz, 1 H, 3-H), 7.00–7.04 (m,
1 H, 4¢-H), 7.10–7.15 (m, 2 H, 3¢-H, 5¢-H), 7.17–7.22 (m, 1 H, Ar-
H).
13C NMR (CDCl3): d = 113.7, 119.1, 119.9, 123.3, 123.7, 124.9,
128.7, 130.0, 131.5, 135.5, 135.3, 138.3, 145.2, 148.1.
1-(2¢-Chlorophenyl)-2-(2¢-thienyl)pyrrole (2m) and 5-(2¢¢-Chlo-
roanilino)-2,2¢-bithiophene (3m)
Treatment of amide 1m with Lawesson’s reagent gave a mixture of
1-(2¢-chlorophenyl)-2-(2¢-thienyl)pyrrole (2m) and 5-(2¢¢-chloroa-
nilino)-2,2¢-bithiophene (3m).
The first component eluted was 1-(2¢-chlorophenyl)-2-(2¢-thie-
nyl)pyrrole (2m); green solid (yield: 16%); mp 72.8–74.0 °C [Et2O–
PE (1:2)].
MS (EI): m/z (%) = 293 (42) [M+, 37Cl], 291 (100) [M+, 35Cl].
HRMS (EI): m/z calcd for C14H1037ClNS2: 292.9914; found:
IR (Nujol): 2922, 2840, 1587, 1510, 1441, 1426, 1328, 1222, 1187,
1160, 1104, 1083, 1067, 1030, 917, 843, 827, 790, 770, 700 cm–1.
292.9915.
1H NMR (acetone-d6): d = 6.32–6.36 (m, 1 H, 4-H), 6.53 (dd, J =
3.6, 1.8 Hz, 1 H, 3-H), 6.60 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.85–
6.90 (m, 2 H, 4¢-H, 5-H), 7.23 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.47–
7.65 (m, 4 H, 3¢¢-H, 4¢¢-H, 5¢¢-H, 6¢¢-H).
13C NMR (acetone-d6): d = 110.1, 110.2, 110.6, 124.2, 124.7, 125.1,
127.8, 128.8, 131.0, 131.2, 131.4, 133.7, 135.6, 138.7.
MS (EI): m/z (%) = 261 (35) [M+, 37Cl], 259 (100) [M+, 35Cl].
HRMS (EI): m/z calcd for C14H1035ClNS: 259.0222; found:
1-(4¢¢-Chlorophenyl-2-(2¢-thienyl)pyrrole (2o) and 5-(4¢¢-Chlo-
roanilino)-2,2¢-bithiophene (3o)
Treatment of amide 1o with Lawesson’s reagent gave a mixture of
1-(4¢¢-chlorophenyl-2-(2¢-thienyl)pyrrole (2o) and 5-(4¢¢-chloroa-
nilino)-2,2¢-bithiophene (3o). The first component eluted was 1-
(4¢¢-chlorophenyl)-2-(2¢-thienyl)pyrrole (2o) as a green solid (yield:
22%); mp 51.7–53.0 °C [Et2O–PE (1:2)].
IR (liquid film): 3104, 1596, 1496, 1463, 1430, 1408, 1348, 1328,
1313, 1211, 1187, 1165, 1091, 1034, 1017, 915, 878, 844, 832, 790,
739, 711, 696 cm–1.
259.0222.
1H NMR (acetone-d6): d = 6.30–6.34 (m, 1 H, 4-H), 6.48 (dd, J =
3.6, 1.8 Hz, 1 H, 3-H), 6.67 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.92–
6.97 (m, 1 H, 4¢-H), 7.00–7.02 (m, 1 H, 5-H), 7.29–7.35 (m, 3 H, 5-
H, 2¢¢-H, 6¢¢-H), 7.50 (d, J = 9.0 Hz, 2 H, 3¢¢-H, 5¢¢-H).
13C NMR (acetone-d6): d = 110.3, 110.5, 112.1, 125.3, 125.5, 126.0,
128.0, 128.8, 130.0, 133.5, 135.3, 139.7.
MS (EI): m/z (%) = 261 (34) [M+, 37Cl], 259 (100) [M+, 35Cl], 224
(14).
HRMS (EI): m/z calcd for C14H1037ClNS: 261.0193; found:
261.0195.
The second component eluted was 5-(2¢¢-chloroanilino)-2,2¢-
bithiophene (3m) as a green oil (yield: 21%).
IR (liquid film): 3377 (NH), 1624, 1587, 1488, 1441, 1426, 1403,
1348, 1328, 1258, 1222, 1208, 1187, 1164, 1082, 1067, 1031, 917,
827, 769, 699, 612 cm–1.
1H NMR (acetone-d6): d = 6.81 (d, J = 3.8 Hz, 1 H, 4-H), 6.87 (dt,
J = 7.5, 1.8 Hz, 1 H, 4¢¢-H), 7.06–7.10 (m, 1 H, 4¢-H), 7.13 (d, J =
3.8 Hz, 1 H, 3-H), 7.16–7.27 (m, 3 H, 3¢-H, 5¢¢-H, 6¢¢-H), 7.36 (br s,
1 H, NH), 7.38 (m, 2 H, 5¢-H, 3¢¢-H).
13C NMR (acetone-d6): d = 110.3, 115.2, 120.7, 121.4, 122.8, 123.6,
124.8, 128.4, 128.5, 130.1, 131.5, 138.0, 143.0, 144.4.
MS (EI): m/z (%) = 293 (40) [M+, 37Cl], 291 (100) [M+, 35Cl].
HRMS (EI): m/z calcd for C14H1035ClNS2: 290.9943; found:
The second component eluted was 5-(4¢¢-chloroanilino)-2,2¢-
bithiophene (3o) as a green solid (yield: 15%); mp 123.0–125.0 °C
[Et2O–PE (1:2)].
290.9944.
IR (liquid film): 3393 (NH), 2256, 1248, 1169, 1086, 1033, 963,
889, 671 cm–1.
1H NMR (acetone-d6): d = 6.68 (d, J = 3.8 Hz, 1 H, 4-H), 7.05–7.12
(m, 4 H, 3¢-H, 4¢-H, 2¢¢-H, 6¢¢-H), 7.18, (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-
H), 7.27 (d, J = 9.0 Hz, 2 H, 3¢¢-H, 5¢-H), 7.38 (dd, J = 5.1, 1.2 Hz,
1 H, 5¢-H), 7.95 (br s, 1 H, NH).
13C NMR (acetone-d6): d = 116.8, 117.7, 123.3, 123.5, 124.4, 124.7,
128.7, 129.1, 129.9, 138.0, 145.2, 146.1.
MS (EI): m/z (%) = 293 (24) [M+, 37Cl], 291 (81) [M+, 35Cl], 207
(100).
1-(3¢¢-Chlorophenyl)-2-(2¢-thienyl)pyrrole (2n) and 5-(3¢¢-Chlo-
roanilino)-2,2¢-bithiophene (3n)
Treatment of amide 1n with Lawesson’s reagent gave a mixture of
1-(3¢¢-chlorophenyl-2-(2¢-thienyl)pyrrole (2n) and 5-(3¢¢-chloroa-
nilino)-2,2¢-bithiophene (3n).
The first component eluted was 1-(3¢¢-chlorophenyl-2-(2¢-thie-
nyl)pyrrole (2n); green oil (yield: 24%).
IR (Nujol): 1594, 1483, 1436, 1348, 1325, 1187, 1167, 1108, 1077,
1037, 924, 876, 844, 786, 767, 689, 610 cm–1.
1H NMR (CDCl3): d = 6.32–6.36 (m, 1 H, 4-H), 6.49 (dd, J = 3.6,
1.8 Hz, 1 H, 3-H), 6.62 (dd, J = 3.9, 1.2 Hz, 1 H, 3¢-H), 6.86–6.92
(m, 2 H, 4¢-H, 5-H), 7.10–7.18 (m, 2 H, 5¢-H, Ar-H), 7.28–7.34 (m,
3 H, 3 × Ar-H).
13C NMR (acetone-d6): d = 110.1, 110.2, 110.6, 124.2, 124.7, 125.1,
127.8, 128.8, 131.0, 131.2, 131.4, 133.7, 135.6, 138.7.
MS (EI): m/z (%) = 261 (36) [M+, 37Cl], 259 (100) [M+, 35Cl].
HRMS (EI): m/z calcd for C14H1037ClNS2: 292.9914; found:
292.9917.
1-(2¢¢-Bromophenyl-2-(2¢-thienyl)pyrrole (2p) and 5-(2¢¢-Bro-
moanilino)-2,2¢-bithiophene (3p)
Treatment of amide 1p with Lawesson’s reagent gave a mixture of
1-(2¢¢-bromophenyl-2-(2¢-thienyl)pyrrole (2p) and 5-(2¢¢-bromoa-
nilino)-2,2¢-bithiophene (3p). The first component eluted was 1-
(2¢¢-bromophenyl-2-(2¢-thienyl)pyrrole (2p; yield: 6%) as a green
solid; mp 94.5–96.0 °C [Et2O–PE (1:2)].
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IR (Nujol): 2925, 1582, 1504, 1482, 1328, 1308, 1221, 1208, 1187,
1161, 1083, 1056, 1028, 955, 918, 843, 828, 771, 724, 701 cm–1.
1H NMR (acetone-d6): d = 6.32–6.34 (m, 1 H, 4-H), 6.52–6.54 (m,
1 H, 3-H), 6.59 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.84–6.89 (m, 2 H,
4¢-H, 5-H), 7.22 (dd, J = 5.4, 1.2 Hz, 1 H, 5¢-H), 7.46–7.56 (m, 3 H,
4¢¢-H, 5¢¢-H, 6¢¢-H), 7.80 (dd, J = 8.0, 1.8 Hz, 1 H, 3¢¢-H).
dibromoanilino)-2,2¢-bithiophene (3r). The first component eluted
was 1-(2¢¢,4¢¢-dibromophenyl)-2-(2¢-thienyl)pyrrole (2r; yield:
24%) as a pale yellow oil.
IR (Nujol): 3104, 3081, 2924, 2855, 1576, 1554, 1508, 1481, 1428,
1407, 1378, 1347, 1327, 1245, 1209, 1187, 1167, 1102, 1079, 1057,
1009, 915, 869, 844, 823, 788, 759, 696, 610, 566 cm–1.
13C NMR (acetone-d6): d = 110.0, 110.1, 124.0, 124.2, 124.7, 125.0,
1H NMR (acetone-d6): d = 6.32–6.38 (m, 1 H, 4-H), 6.53 (dd, J =
3.6, 1.5 Hz, 1 H, 3-H), 6.66 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.86–
6.88 (m, 1 H, 5-H), 6.90–6.94 (m, 1 H, 4¢-H), 7.26 (dd, J = 5.1, 1.2
Hz, 1 H, 5¢-H), 7.45 (d, J = 8.4 Hz, 1 H, 6¢¢-H), 7.74 (dd, J = 8.4, 2.1
Hz, 1 H, 5¢¢-H), 8.0 (d, J = 2.1 Hz, 1 H, 3¢¢-H).
13C NMR (acetone-d6): d = 110.4, 110.5, 123.5, 124.6, 124.9, 125.0,
125.2, 127.9, 129.0, 132.5, 132.9, 135.3, 136.3, 139.8.
127.8, 129.1, 129.4, 131.4, 131.5, 134.2, 135.6, 140.4.
MS (EI): m/z (%) = 305 (70) [M+, 81Br], 303 (67) [M+, 79Br].
HRMS (EI): m/z calcd for C14H1081BrNS: 304.9697; found:
304.9696.
The second component eluted was 5-(2¢¢-bromoanilino)-2,2¢-
bithiophene (3p) as a yellow oil (yield: 46%).
MS (EI): m/z (%) = 385 (53) [M+, 2 × 81Br], 383 (100) [M+,
79Br81Br], 381 (51) [M+, 2 × 79Br].
IR (liquid film): 3375 (NH), 3105, 3022, 2926, 2853, 2589, 1592,
1561, 1488, 1451, 1427, 1353, 1320, 1298, 1254, 1223, 1164, 1118,
1046, 1022, 931, 916, 888, 836, 800, 745, 694, 666, 629, 611 cm–1.
1H NMR (acetone-d6): d = 6.78–6.84 (m, 2 H, 4-H, 4¢¢-H), 7.07–
7.12 (m, 2 H, 3-H, 4¢-H), 7.14 (dd, J = 8.3, 1.8 Hz, 1 H, 6¢¢-H), 7.18
(br s, 1 H, NH), 7.23 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 7.28 (dt, J =
8.0, 1.5 Hz, 1 H, 5¢¢-H), 7.41 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.56
(dd, J = 7.8, 1.5 Hz, 1 H, 3¢¢-H).
HRMS (EI): m/z calcd for C14H981Br2NS: 384.8782; found:
384.8782.
The second component eluted was 5-(2¢¢,4¢¢-dibromoanilino)-2,2¢-
bithiophene (3r) as a green oil (yield: 15%).
IR (Nujol): 3375 (NH), 1585, 1563, 1486, 1427, 1383, 1293, 1264,
1247, 1176, 1031, 867, 838, 800, 694, 529 cm–1.
13C NMR (acetone-d6): d = 110.6, 115.8, 121.6, 122.1, 123.1, 123.9,
1H NMR (acetone-d6): d = 6.84 (d, J = 3.9 Hz, 1 H, 4-H), 7.05 (d,
J = 8.7 Hz, 1 H, 6¢¢-H), 7.08–7.12 (m, 1 H, 4¢-H), 7.14 (d, J = 3.9
Hz, 1 H, 3-H), 7.24 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 7.31 (br s, 1 H,
NH), 7.40–7.46 (m, 2 H, 5¢-H, 5¢¢-H), 7.72 (d, J = 2.4 Hz, 1 H, 3¢¢-
H).
13C NMR (acetone-d6): d = 110.8, 111.3, 116.9, 123.1, 123.2, 124.2,
125.3, 128.8, 132.2, 132.9, 135.4, 138.1, 143.9, 144.3.
125.1, 128.8, 129.4, 132.0, 133.6, 138.3, 144.4, 144.8.
MS (EI): m/z (%) = 337 (100) [M+, 81Br], 335 (93) [M+, 79Br].
HRMS (EI): m/z calcd for C14H1081BrNS2: 336.9417; found:
336.9418.
1-(4¢¢-Bromophenyl-2-(2¢-thienyl)pyrrole (2q) and 5-(4¢¢-Bro-
moanilino)-2,2¢-bithiophene (3q)
Treatment of amide 1q with Lawesson’s reagent gave a mixture of
1-(4¢¢-bromophenyl-2-(2¢-thienyl)pyrrole (2q) and 5-(4¢¢-bromoa-
nilino)-2,2¢-bithiophene (3q). The first component eluted was 1-
(4¢¢-bromophenyl)-2-(2¢-thienyl)pyrrole (2q; yield: 34%) as a pale
yellow oil.
MS (EI): m/z (%) = 417 (56) [M+, 2 × 81Br], 415 (100) [M+,
79Br81Br], 413 (49) [M+, 2 × 79Br].
HRMS (EI): m/z calcd for C14H981Br2NS2: 416.8502; found:
416.8495.
1-(2¢¢-Iodophenyl)-2-(2¢-thienyl)pyrrole (2s) and 5-(2¢¢-Iodo-
anilino)-2,2¢-bithiophene (3s)
Treatment of amide 1s with Lawesson’s reagent gave a mixture of
1-(2¢¢-iodophenyl)-2-(2¢-thienyl)pyrrole (2s) and 5-(2¢¢-iodoanili-
no)-2,2¢-bithiophene (3s). The first component eluted was 1-(2¢¢´-
iodophenyl)-2-(2¢-thienyl)pyrrole (2s) as a green solid (yield: 8%);
mp 97.6–99.0 °C [Et2O–PE (1:2)].
IR (Nujol): 1632, 1491, 1428, 1347, 1097, 1069, 913, 828, 712, 674
cm–1.
1H NMR (CDCl3): d = 6.28–6.32 (m, 1 H, 4-H), 6.48 (dd, J = 3.6,
1.8 Hz, 1 H, 3-H) 6.60 (dd, J = 3.6, 1.0 Hz, 1 H, 3¢-H), 6.85–6.92
(m, 2 H, 5-H, 4¢-H), 7.13 (d, J = 8.9 Hz, 2 H, 2 × Ar-H), 7.16 (dd,
J = 5.2, 1.2 Hz, 1 H, 5¢-H), 7.50 (d, J = 8.9 Hz, 2 H, 2 × Ar-H).
MS (EI): m/z (%) = 305 (100) [M+, 81Br], 303 (97) [M+, 79Br].
HRMS (EI): m/z calcd for C14H1079BrNS: 302.9917; found:
IR (Nujol): 1580, 1504, 1479, 1423, 1402, 1348, 1326, 1309, 1260,
1220, 1187, 1167, 1096, 1021, 917, 794, 764, 709 cm–1.
1H NMR (acetone-d6): d = 6.31–6.34 (m, 1 H, 4-H), 6.53 (dd, J =
3.6, 1.8 Hz, 1 H, 3-H), 6.58 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.78–
6.82 (m, 1 H, 5-H), 6.85 (m, 1 H, 4¢-H), 7.22 (dd, J = 5.2, 1.2 Hz, 1
H, 5¢-H), 7.31 (dt, J = 8.1, 1.5 Hz, 1 H, 4¢¢-H), 7.46 (dd, J = 8.1, 1.5
Hz, 1 H, 6¢¢-H), 7.58 (dt, J = 8.1, 1.5 Hz, 1 H, 5¢¢-H), 8.04 (dd, J =
8.1, 1.5 Hz, 1 H, 3¢¢-H).
13C NMR (acetone-d6): d = 110.1, 110.2, 124.2, 124.6, 124.7, 127.8,
130.1, 130.8, 131.4, 135.8, 138.5, 140.5, 143.3, 144.0.
MS (EI): m/z (%) = 351 (100) [M+].
302.9713.
The second component eluted was 5-(4¢¢-bromoanilino)-2,2¢-
bithiophene (3q) as a green metallic solid (yield: 7%); mp 129–131
°C [Et2O–PE (1:2)].
IR (liquid film): 3428 (NH), 1592, 1519, 1488, 1426, 1175, 1072,
814, 693, 629 cm–1.
1H NMR (CDCl3): d = 5.63 (br s, 1 H, NH), 6.65 (d, J = 3.6 Hz, 1
H, 4-H), 6.82 (d, J = 8.7, 2 H, 2¢¢-H, 6¢¢-H), 6.97 (d, J = 3.6 Hz, 1 H,
3-H), 6.98–7.02 (m, 1 H, 4¢-H), 7.09 (br d, J = 2.4 Hz, 1 H, 3¢-H),
7.19 (br d, J = 5.4 Hz, 1 H, 5¢-H), 7.33 (d, J = 8.7, 2 H, 3¢¢-H, 5¢¢-H).
HRMS (EI): m/z calcd for C14H10INS: 350.9579; found: 350.9582.
The second component eluted was 5-(2¢¢-iodoanilino)-2,2¢-
bithiophene (3s) as a green solid (yield: 55%); mp 91.5–92.5 °C
[Et2O–PE (1:1)].
MS (EI): m/z (%) = 337 (100) [M+, 81Br], 335 (93) [M+, 79Br].
HRMS (EI): m/z calcd for C14H1079BrNS2: 334.9438; found:
334.9429.
IR (liquid film): 3342 (NH), 1582, 1558, 1523, 1480, 1443, 1426,
1292, 1279, 1171, 1079, 1048, 1008, 836, 807, 746, 693 cm–1.
1H NMR (acetone-d6): d = 6.69 (dt, J = 8.0, 1.5 Hz, 1 H, 4¢¢-H), 6.78
(d, J = 3.6 Hz, 1 H, 4-H), 6.90 (br s, 1 H, NH), 7.06–7.10 (m, 2 H,
4¢-H, 6¢¢-H), 7.12 (d, J = 3.6 Hz, 1 H, 3-H), 7.23 (dd, J = 3.6, 1.2 Hz,
1-(2¢¢,4¢¢-Dibromophenyl)-2-(2¢-thienyl)pyrrole (2r) and 5-
(2¢¢,4¢¢-Dibromoanilino)-2,2¢-bithiophene (3r)
Treatment of amide 1r with Lawesson’s reagent gave a mixture of
1-(2¢¢,4¢¢-dibromophenyl)-2-(2¢-thienyl)pyrrole (2r) and 5-(2¢¢,4¢¢-
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Competition between Thienylpyrrole and Bithiophene Formation
209
1 H, 3¢-H), 7.31 (dt, J = 8.0, 1.5 Hz, 1 H, 5¢¢-H), 7.41 (dd, J = 5.1,
1.2 Hz, 1 H, 5¢-H), 7.82 (dd, J = 8.0, 1.5 Hz, 1 H, 3¢¢-H).
13C NMR (acetone-d6): d = 110.6, 115.8, 121.6, 122.6, 123.2, 123.9,
125.1, 128.8, 130.2, 131.8, 138.3, 140.4, 145.5, 147.1.
13C NMR (acetone-d6): d = 110.7, 112.9, 125.2, 125.8, 126.4, 126.8,
127.7, 128.0, 129.6, 131.1, 135.2, 144.7, 166.5.
MS (EI): m/z (%) = 283 (100) [M+].
HRMS (EI): m/z calcd for C16H13NO2S: 283.0667; found:
283.0666.
MS (EI): m/z (%) = 383 (100) [M+].
HRMS (EI): m/z calcd for C14H10INS2: 382.9299; found: 382.9298.
The second component eluted was 5-(4¢¢-methyloxycarbonylanili-
no)-2,2¢-bithiophene (3u) as a yellow solid (yield: 32%); mp 146.4–
148.3 °C [Et2O–PE (1:2)].
1-(3¢¢-Nitrophenyl)-2-(2¢-thienyl)pyrrole (2t) and 5-(3¢¢-Nitro-
anilino)-2,2¢-bithiophene (3t)
Treatment of amide 1t with Lawesson’s reagent gave a mixture of
1-(3¢¢-nitrophenyl)-2-(2¢-thienyl)pyrrole (2t) and 5-(3¢¢-nitroanili-
no)-2,2¢-bithiophene (3t). The first component eluted was 1-(3¢¢-ni-
trophenyl)-2-(2¢-thienyl)pyrrole (2t) as a green oil (yield: 26%).
IR (Nujol): 3314 (NH), 2922, 1679 (C=O), 1601, 1583, 1558, 1530,
1515, 1417, 1266, 1243, 1197, 1173, 1122, 1051, 971, 886, 838,
814, 790, 763, 689 cm–1.
1H NMR (acetone-d6): d = 3.85 (s, 3 H, CO2CH3), 6.80 (d, J = 3.8
Hz, 1 H, 4-H), 7.07–7.15 (m, 4 H, 3-H, 4¢-H, 2¢¢-H, 6¢¢-H), 7.23 (dd,
J = 3.6, 1.2 Hz, 1 H, 3¢-H), 7.41 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.92
(d, J = 8.4 Hz, 2 H, 3¢¢-H, 5¢¢-H), 8.30 (br s, 1 H, NH).
13C NMR (acetone-d6): d = 51.8, 114.2, 119.9, 121.4, 123.25, 123.9,
125.0, 128.8, 130.6, 132.0, 138.2, 144.3, 150.6, 166.9.
MS (EI): m/z (%) = 315 (100) [M+].
IR (Nujol): 3105, 2957, 2926, 2870, 1617, 1587, 1531, 1487, 1463,
1426, 1351, 1328, 1273, 1187, 1167, 1113, 1087, 1038, 928, 896,
865, 844, 804, 738, 710, 683 cm–1.
1H NMR (acetone-d6): 6.38–6.42 (m, 1 H, 4-H), 6.53 (dd, J = 3.6,
1.8 Hz, 1 H, 3-H), 6.74 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.95–7.00
(m, 1 H, 4¢-H), 7.18–7.22 (m, 1 H, 5-H), 7.38 (dd, J = 5.1, 1.2 Hz,
1 H, 5¢-H), 7.74–7.82 (m, 2 H, 2 × Ar-H), 8.12–8.16 (m, 1 H, Ar-H),
8.26–8.32 (m, 1 H, Ar-H).
HRMS (EI): m/z calcd for C16H13NO2S2: 315.0388; found:
315.0386.
13C NMR (acetone-d6): d = 111.0, 113.0, 121.6, 122.7, 125.4, 126.2,
1-(4¢¢-Cyanophenyl)-2-(2¢-thienyl)pyrrole (2v) and
5-(4¢¢-Cyanoanilino)-2,2¢-bithiophene (3v)
Treatment of amide 1v with Lawesson’s reagent gave a mixture of
1-(4¢¢-cyanophenyl)-2-(2¢-thienyl)pyrrole (2v) and 5-(4¢¢-cyano-
anilino)-2,2¢-bithiophene (3v). The first component eluted was 1-
(4¢¢-cyanophenyl)-2-(2¢-thienyl)pyrrole (2v) as a beige solid (yield:
32%); mp 114.2–115.5 °C (Et2O).
126.8, 127.8, 128.2, 131.2, 133.1, 134.5, 134.8, 141.7.
MS (EI): m/z (%) = 270 (100) [M+].
HRMS (EI): m/z calcd for C14H10N2OS2: 270.0463; found:
270.0463.
The second component eluted was 5-(3¢¢-nitroanilino)-2,2¢-
bithiophene (3t) as a green solid (yield: 21%); mp 134.1–136.2 °C
[Et2O–PE (1:2)].
IR (Nujol): 2227 (CN), 1576, 1559, 1569, 1540, 1521, 1507, 1457,
1436, 1390, 1318, 1209, 1188, 914, 844, 794, 719, 697, 668 cm–1.
IR (Nujol): 3351 (NH), 1615, 1563, 1539, 1520, 1344, 1271, 1260,
1169, 993, 864, 838, 818, 799, 792, 730 cm–1.
1H NMR (acetone-d6): d = 6.38–6.42 (m, 1 H, 4-H), 6.52 (dd, J =
3.5, 1.8 Hz, 1 H, 3-H), 6.72 (dd, J = 3.6, 1.2 Hz, 1 H, 3¢-H), 6.97–
7.02 (m, 1 H, 4¢-H), 7.14–7.18 (m, 1 H, 5-H), 7.40 (dd, J = 5.1, 1.2
Hz, 1 H, 5¢-H), 7.50 (d, J = 8.7 Hz, 2 H, 2¢¢-H, 6¢¢-H), 7.88 (d, J =
8.7 Hz, 2 H, 3¢¢-H, 5¢¢-H).
13C NMR (acetone-d6): d = 111.1, 111.4, 113.4, 118.8, 125.3, 126.2,
126.8, 127.5, 127.6, 128.2, 134.0, 134.9, 144.5.
1H NMR (acetone-d6): d = 6.85 (d, J = 3.9 Hz, 1 H, 4-H), 7.07–7.12
(m, 1 H, 4¢-H), 7.16 (d, J = 3.9 Hz, 1 H, 3-H), 7.25 (dd, J = 3.6, 1.2
Hz, 1 H, 3¢-H), 7.41–7.46 (m, 2 H, 5¢-H, 6¢¢-H), 7.54 (t, J = 8.1 Hz,
1 H, 5¢¢-H), 7.69 (m, 1 H, 4¢¢-H), 7.86 (d, J = 2.4 Hz, 1 H, 2¢¢-H),
8.24 (br s, 1 H, NH).
13C NMR (acetone-d6): d = 108.8, 114.4, 120.5, 122.0, 123.4, 124.0,
125.2, 128.8, 131.2, 137.1, 138.1, 144.3, 148.1, 150.2.
MS (EI): m/z (%) = 250 (100) [M+].
MS (EI): m/z (%) = 302 (100) [M+].
HRMS (EI): m/z calcd for C15H10NO2S: 250.0565; found:
250.0566.
HRMS (EI): m/z calcd for C14H10N2O2S2: 302.0184; found:
302.0186.
The second component eluted was 5-(4¢¢-cyanoanilino)-2,2¢-
bithiophene (3v) as a yellow solid (yield: 19%); mp 139.6–141.1
1-(4¢¢-Methyloxycarbonylphenyl)-2-(2¢-thienyl)pyrrole (2u)and
5-(4¢¢-Methyloxycarbonylanilino)-2,2¢-bithiophene (3u)
Treatment of amide 1u with Lawesson’s reagent gave a mixture of
1-(4¢¢-methyloxycarbonylphenyl)-2-(2¢-thienyl)pyrrole (2u) and 5-
(4¢¢-methyloxycarbonylanilino)-2,2¢-bithiophene (3u). The first
component eluted was 1-(4¢¢-methyloxycarbonylphenyl)-2-(2¢-thie-
nyl)pyrrole (2u) as a greenish yellow solid (yield: 37%); mp 76.7–
77.8 °C [Et2O–PE (1:2)].
°C.
IR (Nujol): 3272 (NH), 2213 (CN), 1604, 1562, 1517, 1322, 1266,
1172, 1116, 1047, 1021, 830, 789, 722, 693, 612 cm–1.
1H NMR (acetone-d6): d = 6.83 (d, J = 3.6 Hz, 1 H, 4-H), 7.08–7.12
(m, 1 H, 4¢-H), 7.13 (m, 3 H, 3-H, 2¢¢-H, 6¢¢-H), 7.24 (dd, J = 3.6,
1.2 Hz, 1 H, 3¢-H), 7.43 (dd, J = 5.1, 1.2 Hz, 1 H, 5¢-H), 7.63 (d, J =
9.0 Hz, 2 H, 3¢¢-H, 5¢¢-H), 8.39 (br s, 1 H, NH).
13C NMR (acetone-d6): d = 102.0, 115.0, 120.1, 121.0, 123.3, 124.1,
125.2, 128.8, 131.6, 134.4, 138.0, 143.4, 150.5.
MS (EI): m/z (%) = 282 (100) [M+].
IR (liquid film): 3132, 3103, 3084, 3063, 3017, 2950, 2842, 1727
(C=O), 1512, 1505, 1462, 1455, 1436, 1413, 1348, 1328, 1319,
1305, 1288, 1253, 1213, 1190, 1170, 1099, 1053, 1036, 1021, 1013,
966, 915 cm–1.
1H NMR (acetone-d6): d = 3.94 (s, 3 H, CO2CH3), 6.35 (m, 1 H, 4-
H), 6.50 (dd, J = 3.6, 1.8 Hz, 1 H, 3-H), 6.68 (dd, J = 3.6, 1.2 Hz, 1
HRMS (EI): m/z calcd for C15H10N2S2: 282.2854; found: 282.2885.
H, 3¢-H), 6.94–6.98 (m, 1 H, 4¢-H), 7.10–7.13 (m, 1 H, 5-H), 7.36 Acknowledgment
(dd, J = 5.2, 1.2 Hz, 1 H, 5¢-H), 7.43 (d, J = 8.7 Hz, 2 H, 2¢¢-H, 6¢¢-
Thanks are due to Foundation for Science and Technology (Portu-
gal) for financial support through IBQF (UM) and through FEDER,
POCTI (ref. POCTI/QUI/37816/2001).
H), 8.08 (d, J = 8.7 Hz, 2 H, 3¢¢-H, 5¢¢-H).
Synthesis 2005, No. 2, 199–210 © Thieme Stuttgart · New York

210
M. M. M. Raposo et al.
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