An efficient new method for the synthesis of polysubstituted pyrroles

Article abstract of DOI:10.1055/s-0029-1218703

The three-component reactions of phenacyl bromide or its derivatives, amine, and dialkyl acetylenedicarboxylate in the presence of iron(III) chloride as a catalyst at room temperature afforded polysubstituted pyrroles in high yields. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0029-1218703

PAPER
1625
An Efficient New Method for the Synthesis of Polysubstituted Pyrroles1
S
ynthesis of Poly
i
substitu
s
ted Pyrro
w
les anath Das,* Gandolla Chinna Reddy, Penagaluri Balasubramanyam, Boyapati Veeranjaneyulu
Organic Chemistry Division-1, Indian Institute of Chemical Technology, Hyderabad 500 007, India
Fax +91(40)27193198; E-mail: biswanathdas@yahoo.com
Received 1 February 2010; revised 26 February 2010
amine and dimethyl acetylenedicarboxylate. Thus,
iron(III) chloride was considered to be the catalyst of
choice for the subsequent preparation of a series of pyr-
roles 4a–o from phenacyl bromide or its derivatives,
amine, and dialkyl acetylenedicarboxylate (Table 2). The
reaction was complete within 14–16 hours and the prod-
ucts 4a–o were formed in high yields (84–89%). Both ar-
omatic and aliphatic amines underwent the conversion
equally well. The derivatives of phenacyl bromide con-
taining electron-withdrawing groups also afforded the
products smoothly. Dimethyl as well as diethyl acetylene-
dicarboxylate was used to prepare the pyrrole derivatives.
The structures of the products were identified by their
Abstract: The three-component reactions of phenacyl bromide or
its derivatives, amine, and dialkyl acetylenedicarboxylate in the
presence of iron(III) chloride as a catalyst at room temperature af-
forded polysubstituted pyrroles in high yields.
Key words: polysubstituted pyrroles, three-component reaction,
iron(III) chloride
Pyrroles are among the most important heterocyclic com-
pounds as they are structural elements of various bioactive
natural products2 and pharmaceutical agents.3 They are
also valuable intermediates in organic synthesis.2a,4 Vari-
ous pyrrole derivatives are widely used as organic con-
ducting materials.5 Consequently, a wide range of
procedures have been devised for the synthesis of pyr-
roles.6 However, many of the methods are associated with
various drawbacks such as harsh reaction conditions, te-
dious experimental procedures, unsatisfactory yields, and
long reaction times. Moreover, the number of methods for
the synthesis of polysubstituted pyrroles is relatively lim-
ited. Herein we report an efficient, new method for the
synthesis of polysubstituted pyrroles.
In continuation of our work7 on the development of useful
synthetic methodologies, we have observed that the treat-
ment of phenacyl bromide, or its derivatives, with amine
and dialkyl acetylenedicarboxylate in the presence of a
catalytic amount of iron(III) chloride produced the corre-
sponding 1,2,3,5-substituted pyrroles at room temperature
(Scheme 1).
1
spectral (IR, H and 13C NMR and MS) and analytical
data.
Table 1 Evaluation of Catalytic Activity of Different Catalysts for
the Preparation of Polysubstituted Pyrroles 4a,na
Entry Substrates
Product
Catalyst
Yieldb
(%)
O
FeCl3
CuI
ZnCl2
SnCl2
CeCl3·6 H2O
ZrCl4
89
63
45
42
53
78
38
Br
Ph
COOEt
1
PhNH2
Ph
COOEt
N
COOEt
4a
Ph
I2
no catalyst
trace
COOEt
O
E
FeCl3
CuI
ZnCl2
SnCl2
CeCl3·6 H2O
ZrCl4
87
63
41
39
51
75
31
Br
E
FeCl3 (15 mol%)
O
Ph
CH2Cl2
COOMe
Br
+
+
RNH2
Ar
E
N
R
Ar
r.t., 14–16 h
2
MeNH2
E
Ph
COOMe
4n
N
85–89%
COOMe
1
2
3
4
Me
I2
Scheme 1
no catalyst
trace
COOMe
Initially phenacyl bromide was treated with aniline and di-
ethyl acetylenedicarboxylate using various catalysts
(Table 1). Considering reaction time and yield of the pre-
pared pyrrole 4a, iron(III) chloride was the most effective
catalyst. A similar result was also obtained in the synthe-
sis of 4n when phenacyl bromide was treated with methyl-
a Reaction conditions: phenacyl bromide (1.0 mmol), amine (1.0
mmol), diethyl or dimethyl acetylenedicarboxylate (1.0 mmol), cata-
lyst (15 mol%), r.t.
b Yield of pure isolated product after column chromatography.
Treatment of phenacyl bromide with ammonium acetate
and dimethyl acetylenedicarboxylate under these reaction
conditions gave the trisubstituted pyrrole 5 (Scheme 2).
SYNTHESIS 2010, No. 10, pp 1625–1628
x
x.
x
x
.
2
0
1
0
Advanced online publication: 15.03.2010
DOI: 10.1055/s-0029-1218703; Art ID: Z02110SS
© Georg Thieme Verlag Stuttgart · New York

1626
B. Das et al.
PAPER
COOMe
COOMe
FeCl3 (15 mol%)
CH2Cl2
O
O
E
E
E
Ar
E
Ar
Br +
+
NH4OAc
Ph
COOMe
Br
N
-
Ph
FeCl3
r.t., 14 h
1
H
COOMe
+
R-NH2
O
H
H
N
R
N
84%
5
E
R
E
3
A
B
2
Scheme 2
FeCl3
Table 2 Synthesis of Polysubstituted Pyrroles 4a–o Using Iron(III)
E
E
Chloridea
– H2O
Ar
HO
Entry ProductAr
R
E
Time Yieldb
E
Ar
E
N
N
R
(h)
14
14
15
15
15
16
15
16
14
14
16
16
14
14
15
(%)
89
89
86
86
85
85
84
84
87
86
84
85
88
87
87
R
4
1
2
4a
4b
4c
4d
4e
4f
Ph
Ph
Ph
Ph
Ph
CO2Et
CO2Me
CO2Et
CO2Me
CO2Et
CO2Me
CO2Me
CO2Et
Scheme 3
Ph
operational simplicity, and impressive yields are the ad-
vantages of the method.
3
4-BrC6H4
4-BrC6H4
4
5
4-O2NC6H4 Ph
4-O2NC6H4 Ph
The spectra were recorded with the following instruments: IR: Per-
kin-Elmer RX FT-IR spectrophotometer; NMR: Varian Gemini 300
MHz (1H) and 75 MHz (13C) spectrometer and ESI-MS: VG-Au-
tospec micromass (70eV) instrument. Column chromatography was
performed over silica gel (BDH, 100–200 mesh) and TLC with sil-
ica gel F254 (Merck) plates.
6
7
4g
4h
4i
Ph
4-FC6H4
8
4-O2NC6H4 4-FC6H4
9
Ph
Ph
4-MeC6H4 CO2Me
4-MeC6H4 CO2Et
Dialkyl 5-Aryl-1H-pyrrole-2,3-dicarboxylates 4a–o; General
Procedure
10
11
12
13
14
15
4j
To a stirred soln of phenacyl bromide or its derivatives 1 (1 mmol)
and amine 2 (1 mmol) in CH2Cl2 (6 mL) was added FeCl3 (15
mol%). After 5 min, dialkyl acetylenedicarboxylate 3 (1 mmol) was
added dropwise. The mixture was stirred at r.t. for 14–16 h (TLC
monitoring). After completion, the solvent was evaporated; the res-
idue was washed with cold H2O (2 × 5 mL) and subsequently ex-
tracted with EtOAc (2 × 10 mL). The extract was dried (anhyd
Na2SO4) and concentrated under vacuum. The residue was subject-
ed to column chromatography (silica gel, 3–8% EtOAc–hexane) to
give pure pyrrole derivative.
4k
4l
4-O2NC6H4 4-MeC6H4 CO2Me
4-O2NC6H4 4-MeC6H4 CO2Et
4m
4n
4o
Ph
Ph
Ph
Bn
Me
Et
CO2Me
CO2Me
CO2Et
a Reaction conditions: phenacyl bromide 1 (1.0 mmol), amine 2 (1.0
mmol), dialkyl acetylenedicarboxylate 3 (1.0 mmol), FeCl3 (15
mol%), r.t.
Diethyl 1,5-Diphenyl-1H-pyrrole-2,3-dicarboxylate (4a)
IR (KBr): 1720, 1598, 1502, 1413, 1240 cm–1.
b Yields of pure isolated products after column chromatography.
1H NMR (300 MHz, CDCl3): d = 7.49–7.20 (m, 10 H), 6.93 (s, 1 H),
4.28 (q, J = 7.0 Hz, 2 H), 4.16 (q, J = 7.0 Hz, 2 H), 1.24 (t, J = 7.0
Hz, 3 H), 1.12 (t, J = 7.0 Hz, 3 H).
13C NMR (50 MHz, CDCl3): d = 166.4, 160.1, 140.0, 133.1, 128.8,
128.2, 127.9, 127.1, 126.4, 125.9, 124.4, 123.2, 122.2, 61.5, 61.0,
14.0, 13.9.
The possible mechanism of this conversion involves ini-
tial reaction of the amine 2 with dialkyl acetylenedicar-
boxylate 3 in the presence of the catalyst to form the anion
A8 which then attacks phenacyl bromide 1 to produce the
intermediate B. Subsequent cyclization of B followed by
dehydration afforded the polysubstituted pyrrole 4
(Scheme 3). When the reaction was carried out separately
with aniline and dimethyl acetylenedicarboxylate using
iron(III) chloride, only the alkene corresponding to the an-
ion A (with E-configuration) was obtained.
MS (ESI): m/z = 364 [M + H]+.
Anal. Calcd for C22H21NO4: C, 72.73; H, 5.79; N, 3.86. Found: C,
72.85; H, 5.72; N, 3.82.
Dimethyl 1,5-Diphenyl-1H-pyrrole-2,3-dicarboxylate (4b)
IR (KBr): 1727, 1498, 1447, 1255 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.52–7.21 (m, 10 H), 6.98 (s, 1 H),
In conclusion, we have demonstrated a new efficient
method for an easy access to 1,2,3,5-tetrasubstituted pyr-
roles by treatment of phenacyl bromide or its derivatives,
amine, and dialkyl acetylenedicarboxylate using iron(III)
chloride as a catalyst. The mild reaction conditions, appli-
cation of an easily available and less expensive catalyst,
3.81 (s, 3 H), 3.70 (s, 3 H).
13C NMR (50 MHz, CDCl3): d = 167.1, 160.8, 139.6, 133.3, 128.8,
128.2, 127.9, 127.0, 126.1, 126.0, 125.1, 123.2, 52.4, 52.0.
MS (ESI): m/z = 336 [M + H]+.
Anal. Calcd for C20H17NO4: C, 71.64; H, 5.08; N, 4.18. Found: C,
71.58; H, 5.12; N, 4.22.
Synthesis 2010, No. 10, 1625–1628 © Thieme Stuttgart · New York

PAPER
Synthesis of Polysubstituted Pyrroles
MS (ESI): m/z = 354 [M + H]+.
1627
Diethyl 5-(4-Bromophenyl)-1-phenyl-1H-pyrrole-2,3-dicarbox-
ylate (4c)
Anal. Calcd for C20H16FNO4: C, 67.99; H, 4.53; N, 3.97. Found: C,
67.89; H, 4.56; N, 3.91.
IR (KBr): 1719, 1452, 1403 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.52–7.38 (m, 6 H), 7.40–7.25 (m,
3 H), 6.91 (s, 1 H), 4.25 (q, J = 7.0 Hz, 2 H), 4.12 (q, J = 7.0 Hz, 2
H), 1.22 (t, J = 7.0 Hz, 3 H), 1.11 (t, J = 7.0 Hz, 3 H).
13C NMR (50 MHz, CDCl3): d = 166.1, 160.2, 139.2, 132.1, 131.8,
131.0, 129.2, 129.0, 128.2, 126.1, 125.6, 121.0, 61.2, 61.0, 13.9,
13.2.
Diethyl 1-(4-Fluorophenyl)-5-(4-nitrophenyl)-1H-pyrrole-2,3-
dicarboxylate (4h)
IR (KBr): 1721, 1600, 1515 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.22 (d, J = 8.0 Hz, 2 H), 7.59 (d,
J = 8.0 Hz, 2 H), 7.39–7.31 (m, 2 H), 7.12 (t, J = 8.0 Hz, 2 H), 7.00
(s, 1 H), 4.30 (q, J = 7.0 Hz, 2 H), 4.15 (q, J = 7.0 Hz, 2 H), 1.20 (t,
J = 7.0 Hz, 3 H), 0.88 (t, J = 7.0 Hz, 3 H).
13C NMR (50 MHz, CDCl3): d = 168.1, 164.9, 147.0, 140.1, 135.8,
130.9, 129.1, 129.0, 128.9, 125.1, 123.5, 122.2, 121.1, 115.6, 115.0,
61.2, 60.8, 13.0, 12.9.
MS (ESI): m/z = 444, 442 [M + H]+.
Anal. Calcd for C22H20BrNO4: C, 60.00; H, 4.55; N, 3.18. Found: C,
60.21; H, 4.62; N, 3.12.
Dimethyl 5-(4-Bromophenyl)-1-phenyl-1H-pyrrole-2,3-dicar-
boxylate (4d)
MS (ESI): m/z = 449 [M + Na]+.
IR (KBr): 1716, 1450, 1412 cm–1.
Anal. Calcd for C22H19FN2O6: C, 61.97; H, 4.46; N, 6.57. Found: C,
61.88; H, 4.52; N, 6.61.
1H NMR (300 MHz, CDCl3): d = 7.52–7.41 (m, 5 H), 7.38–7.21 (m,
4 H), 6.92 (s, 1 H), 3.81 (s, 3 H), 3.69 (s, 3 H).
Dimethyl 5-Phenyl-1-(4-tolyl)-1H-pyrrole-2,3-dicarboxylate
13C NMR (50 MHz, CDCl3): d = 166.6, 160.4, 140.0, 139.2, 132.3,
131.1, 130.8, 129.1, 129.0, 128.5, 128.2, 126.0, 125.2, 124.2, 123.5,
120.9, 120.2, 52.2, 52.0.
(4i)
IR (KBr): 1720, 1659, 1451, 1415 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.43–7.31 (m, 3 H), 7.30–7.20 (m,
4 H), 7.19–7.02 (m, 2 H), 6.95 (s, 1 H), 3.81 (s, 3 H), 3.70 (s, 3 H),
2.41 (s, 3 H).
13C NMR (50 MHz, CDCl3): d = 167.1, 161.1, 138.7, 136.3, 133.3,
131.2, 129.2, 128.6, 128.4, 128.2, 128.0, 127.2, 125.6, 51.8, 51.2,
22.0.
MS (ESI): m/z = 414, 416 [M + H]+.
Anal. Calcd for C20H16BrNO4: C, 57.97; H, 3.86; N, 3.38. Found: C,
57.91; H, 3.82; N, 3.41.
Diethyl 5-(4-Nitrophenyl)-1-phenyl-1H-pyrrole-2,3-dicarboxy-
late (4e)
IR (KBr): 1716, 1601, 1519, 1343 cm–1.
MS (ESI): m/z = 350 [M + H]+.
1H NMR (300 MHz, CDCl3): d = 8.22 (d, J = 8.0 Hz, 2 H), 7.61 (d,
J = 8.0 Hz, 2 H), 7.51–7.42 (m, 3 H), 7.40–7.32 (m, 2 H), 7.06 (s, 1
H), 4.32 (q, J = 7.0 Hz, 2 H), 4.15 (q, J = 7.0 Hz, 2 H), 1.28 (t,
J = 7.0 Hz, 3 H), 1.11 (t, J = 7.0 Hz, 3 H).
13C NMR (50 MHz, CDCl3): d = 166.0, 160.1, 157.2, 140.1, 138.7,
129.1, 129.0, 128.2, 126.3, 123.5, 122.8, 122.6, 121.0, 61.2, 61.0,
13.1, 13.0.
Anal. Calcd for C21H19NO4: C, 72.21; H, 5.44; N, 4.01. Found: C,
72.28; H, 5.40; N, 4.07.
Diethyl 5-Phenyl-1-(4-tolyl)-1H-pyrrole-2,3-dicarboxylate (4j)
IR (KBr): 1720, 1601, 1519, 1460 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.42 (d, J = 8.0 Hz, 2 H), 7.33 (t,
J = 8.0 Hz, 2 H), 7.30–7.21 (m, 5 H), 6.94 (s, 1 H), 4.30 (q, J = 7.0
Hz, 2 H), 4.15 (q, J = 7.0 Hz, 2 H), 2.41 (s, 3 H), 1.31 (t, J = 7.0 Hz,
3 H), 1.18 (t, J = 8.0 Hz, 3 H).
13C NMR (50 MHz, CDCl3): d = 166.7, 160.1, 138.9, 137.1, 133.8,
131.1, 129.8, 128.5, 127.8, 127.0, 126.1, 126.0, 61.2, 61.0, 21.0,
13.6, 13.5.
MS (ESI): m/z = 409 [M + H]+.
Anal. Calcd for C22H20N2O6: C, 64.71; H, 4.90; N, 6.86. Found: C,
64.78; H, 4.86; N, 6.82.
Dimethyl 5-(4-Nitrophenyl)-1-phenyl-1H-pyrrole-2,3-dicar-
boxylate (4f)
MS (ESI): m/z = 378 [M + H]+.
IR (KBr): 1712, 1600, 1511, 1443 cm–1.
Anal. Calcd for C23H23NO4: C, 73.21; H, 6.10; N, 3.71. Found: C,
73.29; H, 6.15; N, 3.78.
1H NMR (300 MHz, CDCl3): d = 8.22 (d, J = 8.0 Hz, 2 H), 7.58 (d,
J = 8.0 Hz, 2 H), 7.51–7.41 (m, 3 H), 7.39–7.32 (m, 2 H), 7.02 (s, 1
H), 3.82 (s, 3 H), 3.71 (s, 3 H).
13C NMR (50 MHz, CDCl3): d = 166.2, 160.1, 146.5, 139.9, 138.2,
129.0, 128.9, 128.2, 126.1, 126.0, 125.2, 123.8, 122.0, 120.5, 52.1,
52.0.
Dimethyl 5-(4-Nitrophenyl)-1-(4-tolyl)-1H-pyrrole-2,3-dicar-
boxylate (4k)
IR (KBr): 1731, 1556, 1492 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.21 (d, J = 8.0 Hz, 2 H), 7.58 (d,
J = 8.0 Hz, 2 H), 7.39–7.03 (m, 4 H), 7.01 (s, 1 H), 3.82 (s, 3 H),
3.60 (s, 3 H), 2.41 (s, 3 H).
13C NMR (50 MHz, CDCl3): d = 166.1, 160.2, 146.4, 139.0, 130.1,
129.9, 128.3, 128.1, 127.1, 125.7, 125.1, 123.2, 123.1, 52.1, 52.0,
22.2.
MS (ESI): m/z = 381 [M + H]+.
Anal. Calcd for C20H16N2O6: C, 63.17; H, 4.21; N, 7.37. Found: C,
63.23; H, 4.26; N, 7.31.
Dimethyl 1-(4-Fluorophenyl)-5-phenyl-1H-pyrrole-2,3-dicar-
boxylate (4g)
MS (ESI): m/z = 395 [M + H]+.
IR (KBr): 1714, 1451, 1415 cm–1.
Anal. Calcd for C21H18N2O6: C, 63.96; H, 4.57; N, 7.11. Found: C,
63.87; H, 4.52; N, 7.14.
1H NMR (300 MHz, CDCl3): d = 7.50–7.29 (m, 7 H), 7.12 (t, J = 7.0
Hz, 2 H), 6.98 (s, 1 H), 3.83 (s, 3 H), 3.71 (s, 3 H).
Diethyl 5-(4-Nitrophenyl)-1-(4-tolyl)-1H-pyrrole-2,3-dicarbox-
ylate (4l)
13C NMR (50 MHz, CDCl3): d = 166.0, 161.1, 146.9, 141.0, 138.3,
132.5, 129.2, 129.0, 127.8, 127.2, 126.7, 125.5, 121.2, 115.2, 115.0,
52.2, 51.7.
IR (KBr): 1718, 1607, 1519, 1432 cm–1.
Synthesis 2010, No. 10, 1625–1628 © Thieme Stuttgart · New York

1628
B. Das et al.
PAPER
1H NMR (300 MHz, CDCl3): d = 8.21 (d, J = 8.0 Hz, 2 H), 7.62 (d,
J = 8.0 Hz, 2 H), 7.29–7.09 (m, 4 H), 7.02 (s, 1 H), 4.31 (q, J = 7.0
Hz, 2 H), 4.14 (q, J = 7.0 Hz, 2 H), 2.41 (s, 3 H), 1.32 (t, J = 7.0 Hz,
3 H), 1.14 (t, J = 7.0 Hz, 3 H).
13C NMR (50 MHz, CDCl3): d = 165.7, 160.0, 147.1, 139.0, 130.0,
129.9, 128.1, 128.0, 127.6, 126.2, 126.0, 123.3, 123.1, 61.5, 61.2,
22.5, 13.5, 13.2.
1H NMR (300 MHz, CDCl3): d = 9.32 (s, 1 H), 7.60 (d, J = 8.0 Hz,
2 H), 7.40 (t, J = 8.0 Hz, 2 H), 7.28 (t, J = 8.0 Hz, 1 H), 6.82 (d,
J = 2.0 Hz, 1 H), 3.92 (s, 3 H), 3.84 (s, 3 H).
13C NMR (50 MHz, CDCl3): d = 167.5, 161.0, 135.2, 130.5, 128.6,
128.1, 126.5, 123.6, 122.3, 110.8, 51.2, 50.5.
MS (ESI): m/z = 260 [M + H]+.
Anal. Calcd for C14H13NO4: C, 64.87; H, 5.02; N, 5.41. Found: C,
64.81; H, 5.08; N, 5.45.
MS (ESI): m/z = 423 [M + H]+.
Anal. Calcd for C23H22N2O6: C, 65.40; H, 5.21; N, 6.64. Found: C,
65.32; H, 5.27; N, 6.59.
Acknowledgment
Dimethyl 1-Benzyl-5-phenyl-1H-pyrrole-2,3-dicarboxylate
The authors thank CSIR and UGC, New Delhi for financial assi-
stance.
(4m)
IR (KBr): 1711, 1449, 1404 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.41–7.12 (m, 10 H), 6.92 (s, 1 H),
5.51 (s, 2 H), 3.81 (s, 3 H), 3.73 (s, 3 H).
References
13C NMR (50 MHz, CDCl3): d = 167.2, 160.8, 137.1, 133.2, 129.0,
128.9, 128.2, 127.2, 127.1, 127.0, 125.7, 124.5, 122.2, 121.1, 52.5,
52.4, 51.7.
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Anal. Calcd for C21H19NO4: C, 72.21; H, 5.44; N, 4.01. Found: C,
72.28; H, 5.52; N, 4.08.
Dimethyl 1-Methyl-5-phenyl-1H-pyrrole-2,3-dicarboxylate
(4n)
IR (KBr): 1710, 1596, 1447 cm–1.
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3.90 (s, 3 H), 3.78 (s, 3 H), 3.72 (s, 3 H).
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126.9, 126.5, 125.8, 123.2, 121.1, 51.6, 51.0, 29.1.
MS (ESI): m/z = 274 [M + H]+.
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Chem. Mater. 2003, 15, 1064. (b) Pu, S.; Liu, G.; Shen, L.;
Xu, J. Org. Lett. 2007, 9, 2139.
Anal. Calcd for C15H15NO4: C, 65.93; H, 5.50; N, 5.13. Found: C,
65.86; H, 5.54; N, 5.07.
Diethyl 1-Ethyl-5-phenyl-1H-pyrrole-2,3-dicarboxylate (4o)
IR (KBr): 1721, 1607, 1462 cm–1.
(6) Some recent examples: (a) Larionov, O. V.; de Meijere, A.
Angew. Chem. Int. Ed. 2005, 44, 5664. (b) Minetto, G.;
Raveglia, L. F.; Sega, A.; Taddei, M. Eur. J. Org. Chem.
2005, 24, 5277. (c) Shiner, C. M.; Laner, T. D. Tetrahedron
2005, 61, 11628. (d) Hwang, S. J.; Cho, S. H.; Chang, S.
J. Am. Chem. Soc. 2008, 130, 16158. (e) Abid, M.;
Teixeira, L.; Torok, B. Org. Lett. 2008, 10, 933. (f) La, Y.
D.; Arndtsen, B. A. Angew. Chem. Int. Ed. 2008, 47, 5430.
(7) (a) Das, B.; Balasubramanyam, P.; Krishnaiah, M.;
Veeranjaneyulu, B.; Reddy, G. C. J. Org. Chem. 2009, 74,
4393. (b) Das, B.; Damodar, K.; Bhunia, N. J. Org. Chem.
2009, 74, 5607. (c) Das, B.; Satyalakshmi, G.; Suneel, K.;
Damodar, K. J. Org. Chem. 2009, 74, 8400. (d) Das, B.;
Balasubramanyam, P.; Veeranjaneyulu, B.; Reddy, G. C.
J. Org. Chem. 2009, 74, 9505.
1H NMR (300 MHz, CDCl3): d = 7.41–7.12 (m, 5 H), 6.87 (s, 1 H),
4.40–4.11 (m, 6 H), 1.42 (t, J = 7.0 Hz, 3 H), 1.31 (t, J = 7.0 Hz, 3
H), 1.22 (t, J = 7.0 Hz, 3 H).
13C NMR (50 MHz, CDCl3): d = 167.2, 159.8, 133.5, 128.0, 127.2,
126.4, 123.2, 122.0, 120.1, 61.0, 60.3, 44.5, 17.0, 13.7.
MS (ESI): m/z = 316 [M + H]+.
Anal. Calcd for C18H21NO4: C, 68.57; H, 6.67; N, 4.44. Found: C,
68.69; H, 6.61; N, 4.40.
Dimethyl 5-Phenyl-1H-pyrrole-2,3-dicarboxylate (5)
IR (KBr): 1720, 1450, 1408 cm–1.
(8) Zhu, Q.; Jiang, H.; Li, J.; Zhang, M.; Wang, X.; Qi, C.
Tetrahedron 2009, 65, 4604.
Synthesis 2010, No. 10, 1625–1628 © Thieme Stuttgart · New York