InCl3 catalysed one-pot synthesis of substituted pyrroles and 2-pyrones

Article abstract of DOI:10.1071/CH12359

An efficient InCl3 catalysed one-pot strategy has been developed for the synthesis of tetra-substituted pyrroles and tri-substituted 2-pyrones in very good yields. Tetra-substituted pyrroles were prepared from 1,4-enediones and β-dicarbonyls employing NH4

Full text of DOI:10.1071/CH12359

CSIRO PUBLISHING
Aust. J. Chem. 2013, 66, 241–251
Full Paper
http://dx.doi.org/10.1071/CH12359
InCl3 Catalysed One-Pot Synthesis of Substituted
Pyrroles and 2-Pyrones
A C
,
A C
,
A B
,
Sanjit K. Mahato,
Jayaraman Vinayagam,
Sumit Dey,
A
A
A D
,
Ajay K. Timiri, Sourav Chatterjee, and Parasuraman Jaisankar
A
Department of Chemistry, CSIR-Indian Institute of Chemical Biology, Kolkata
700 032, India.
B
Current address: Department of Chemistry, Colorado State University, Fort Collins,
CO 80523, USA.
C
These two authors contributed equally to this work.
D
Corresponding author. Email: jaisankar@iicb.res.in
An efficient InCl3 catalysed one-pot strategy has been developed for the synthesis of tetra-substituted pyrroles and
tri-substituted 2-pyrones in very good yields. Tetra-substituted pyrroles were prepared from 1,4-enediones and
b-dicarbonyls employing NH4OAc as a nitrogen source, through a combination of Michael addition and Paal–Knorr
methods. Tri-substituted 2-pyrones were synthesised from 1,4-ynediones and appropriate b-dicarbonyls using a sequential
Michael addition and 6-exo-trig cyclisation.
Manuscript received: 31 July 2012.
Manuscript accepted: 24 October 2012.
Published online: 4 December 2012.
[Cp*RhCl2]2 (Cp*¼ 1,2,3,4,5-pentamethylcyclopentadiene),[22c]
and Ni(COD)2 (COD¼ 1,5-cyclooctadiene) with N-heterocyclic
carbenes (NHCs) as ligand.[22d] As with the pyrroles, most of
the above methods need expensive catalysts,[22a,22c] stoichio-
metric reagents,[21b] inert reaction conditions,[21a] tedius and
time consuming harsh conditions[22c] resulting in low yield of
the products,[22c] and result in the undesired generation of
toxic waste.[22d] To the best of our knowledge, there is no
suitable literature precedence for the synthesis of 2-pyrone using
simple Lewis acid catalysts. Consequently, the syntheses of
2-pyrone analogues continue to attract the attention of organic
chemists.
Reactions catalysed by Lewis acids such as AlCl3, BF3ꢀEt2O,
ZnCl2, TiCl4, and SnCl2 have brought about a radical change in
the approach towards the synthesis of several important hetero-
cycles. Indium belongs to the same group of the periodic table as
boron and aluminium, still InCl3 has become popular among
synthetic organic chemists due to its capacity to ensure chemo-
and regio-selectivity in various chemical transformations.[23,24]
It is generally non-toxic in nature, recyclable, and immune to
moisture.[25] In recent times, indium(III) chloride in particular
has emerged as a potent Lewis acid catalyst for Diels–Alder,[26a]
aldol,[26b] Friedel–Crafts,[26c] and various other organic
transformations.[27]
Introduction
The pyrrole[1] ring is one of the most common skeletal features
found in heterocycles and natural products.[2] Generally pyr-
roles possess a broad spectrum of biological activities such as
antimicrobial,[3a] telomerase inhibitory,[3b] antifungal,[3c]
cardiotonic,[3d] pheromonal,[3e] and phytotoxic effects.[3f] The
classical approaches for synthesising pyrroles are Knorr,[4]
Hantzsch,[5] and Paal–Knorr[6] methods. Different catalytic
methods based on Ti(OPr-i)4,[7] Cu(OTf)2,[8] AgBF4,[9]
Bi(NO3)3,[10] PtCl2,[11] Rh2(oct)4 (oct ¼ octanoate),[12]
Sc(OTf)3,[13] phosphomolybdic acid (PMA)/SiO2,[14a]
Zn(OTf)2,[14b] FeCl3[14c] and others[15] have also been reported to
prepare various substituted pyrrole moieties. The main dis-
advantages of almost all these methods are the requirement of
relatively expensive catalysts,[11–13] stoichiometric amounts of
reagents,[10] an inert reaction atmosphere,[11,12] long and harsh
reactions conditions[10] resulting in poor yield of the pro-
ducts,[10,12] and generation of toxic metal containing
waste.[7,11,12] In addition, there are few reports in the literature
of multi-component strategies for the synthesis of substituted
pyrroles.[16] Due to the diverse medicinal properties of different
pyrrole scaffolds, the syntheses of pyrroles is still unabated.
2-Pyrones[17] are another heterocyclic motif having various
biological activities[18] and found in several natural products.[19]
In addition to their biological activities, 2-pyrones have impor-
tant applications in synthetic chemistry. 2-Pyrones have limited
aromatic character, as a result they are valuable heterosubsti-
tuted dienes for the Diels–Alder [4 þ 2] cycloaddition reac-
tion.[20] The synthesis of 2-pyrones has been achieved by both
non-metal-mediated[21] and transition metal-catalyzed proce-
dures based on [(Ph3P)AuCl],[22a] PdCl2(PPh3)2–Et3N–CuI,[22b]
In connection with one of our ongoing research projects for
developing novel bioactive heterocyclic scaffolds,[28] we had
earlier observed that the reaction of 1,2-dibenzoylethylene (1a)
with methyl acetoacetate (2a) using InCl3 as a catalyst afforded
tetra-substituted furan 3[28b] (Scheme 1), whereas the treatment
of dibenzoylacetylene (4a) with ethyl acetoacetate (2b) and
NH4OAc yielded (ꢁ)-3,30-bipyrrole 5[28a] (Scheme 2). We soon
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242
S. K. Mahato et al.
realised that the introduction of NH4OAc in the reaction
between 1a and 2a led to the formation of a substituted pyrrole
6a (Scheme 1). On the other hand, treating 4a with 2b in the
absence of NH4OAc resulted in the formation of substituted
2-pyrone 8a instead of the expected 3,30-bifuran 7 (Scheme 2).
Accordingly, we set about optimising and examining the scope
of these interesting transformations.
Results and Discussion
Our initial efforts were focussed on reacting 1,2-
dibenzoylethylene (1a, 1.0 equiv.) and methyl acetoacetate (2a,
1.0 equiv.) in the presence of ammonium acetate (1.1 equiv.) and
10 mol % of InCl3 as a Lewis acid catalyst in acetonitrile at room
temperature which afforded, to our delight, the pyrrole 6a in
reasonable yield (Table 1, entry 2). Conducting the same reac-
tion in the absence of InCl3 did not generate the pyrrole 6a,
instead 1a and 2a were fully recovered (Table 1, entry 1). In
order to optimize the reaction conditions, various solvents and
Lewis acid catalysts were screened (Table 1, entries 2–11). The
study revealed that THF as solvent and 10 mol % of InCl3 as a
Lewis acid catalyst (Table 1, entry 5) gave the pyrrole 6a in
much improved yield (96 %). Increasing the catalyst loading to
20 mol % did not improve the product yield (Table 1, entry 6). It
is pertinent to mention that the presence of water prevented
pyrrole formation (Table 1, entry 7).
This optimized method was then exploited to prepare several
substituted pyrroles 6b–s (Table 2) from various substituted
b-dicarbonyls 2a–e and 1,4-enediones 1a–f.[28a,29] When a
mixture of 1a and NH4OAc was reacted with either ethyl
benzoylacetate (2d) or benzoylacetone (2e) in the presence of
10 mol % of InCl3, the desired pyrroles 6p and 6q were formed
with low yields, which did not change even after prolonging the
reaction at elevated temperatures (Table 2, entry 16, 17). The
reaction of unsymmetrical 1,4-enedione 1f with 2b in the
presence of NH4OAc afforded the expected regioisomeric
pyrroles 6r and 6s in approximately a 1.5 : 1 ratio in a total
61 % yield (Table 2, entry 18).
O
Me
OMe
Ph
Ph
ꢀ
O
O
O
1a
2a
InCl3 catalyst
NH4OAc
COOMe
Ph
Ph
COOMe
Me
O
O
Me
N
H
Ph
O
Ph
6a
3
Ref. [28b]
(This paper)
Scheme 1. Synthesis of furan 3 and pyrrole 6a.
O
O
Ph
Me
OEt
ꢀ
O
O
2b
Ph
4a
On the other hand, reaction of dibenzoylmethane (2f) with 1a
and NH4OAc afforded, to our disappointment, 3-amino-1,3-
diphenylprop-2-en-1-one (9)[30] as the only product instead of
the expected pyrrole (Scheme 3), probably due to reduction of
the nucleophilic character of 2f by the presence of phenyl groups
making it difficult to react with elctrophile 1a.
The formation of pyrrole 6a can be explained by the InCl3-
assisted Michael addition of 2a to the Michael acceptor 1a to
form the Michael adduct A, which then undergoes further
addition of ammonia followed by InCl3-assisted cyclisation
and dehydration (Scheme 4).
InCl3 catalyst
NH4OAc
Me
Me
O
HN
O
O
Ph
Ph
COOEt
COOEt
Ph
Ph
COOEt
COOEt
Ph
O
Me
Ph
HN
O
O
Me
Me
5
7
8a
The reaction between dibenzoylacetylene (4a, 1.0 equiv.)
and 2b (1.0 equiv.) in the presence of InCl3 (10 mol %) in THF,
with the exclusion of NH4OAc, afforded, to our surprise, tri-
substituted 2-pyrone 8a instead of the expected 3,30-bifuran 7 at
(This paper)
Ref. [28a]
Not formed
Scheme 2. Synthesis of (ꢁ)-3,30-bipyrrole 5 and 2-pyrone 8a.
Table 1. Optimization of reaction conditions for the synthesis of pyrrole 6a
EntryA
Catalyst
Solvent
Time [h]B
YieldC [%]
1
None
CH3CN
CH3CN
MeOH
i-PrOH
THF
8
5
0
48
25
22
96
96
NR
76
58
55
51
2
InCl3 (10 mol-%)
InCl3 (10 mol-%)
InCl3 (10 mol-%)
InCl3 (10 mol-%)
InCl3 (20 mol-%)
InCl3 (10 mol-%)
FeCl3 (10 mol-%)
ZnCl2 (10 mol-%)
AlCl3 (10 mol-%)
Montmorillonite K10 (10 wt-%)
3
18
11
2
4
5
6
THF
2
7
THF/H2O (7 : 3)
THF
40
8
8
9
THF
5.5
10
11
THF
10
18
THF
AReaction conditions: 1a (1.0 mmol), 2a (1.0 mmol), NH4OAc (1.1 mmol), rt.
BExtension of the reaction time did not improve the product yield.
CIsolated yield. NR = no reaction.

One-Pot Synthesis of Pyrroles and 2-Pyrones
243
Table 2. Synthesis of substituted pyrroles 6a s
]
O
R1
COR4
R3
InCl3 (10 mol-%)
THF, rt
R4
R2 ꢀ NH4OAc ꢀ R3
R1
O
N
H
R2
O
O
O
1
2
6
EntryA
1,4-Enedione
b-Dicarbonyl
Product
Time [h]B
YieldC [%]
1
1a: R1 ¼ R2 ¼ Ph
2a: R3 ¼ Me; R4 ¼ OMe
6a
6b
6c
2
2
96[31]
93
2
1a
1a
2b: R3 ¼ Me; R4 ¼ OEt
3
2c: R3 ¼ R4 ¼ Me
2
94
4
1b: R1 ¼ R2 ¼ 4-Me-C6H4
2a
6d
6e
2
94
5
1b
2b
2.5
2
92
6
1b
2c
6f
94
7
1c: R1 ¼ R2 ¼ 4-Cl–C6H4
2a
6g
2.5
3
96
8
1c
2b
6h
6i
91
9
1c
2c
3
93
10
11
12
13
14
15
16
17
18
1d: R1 ¼ R2 ¼ 4-Br-C6H4
2a
6j
3.5
3.5
3
93
1d
2b
6k
6l
94
1d
2c
93
1e: R1 ¼ R2 ¼ 3-Cl–4-Me-C6H3
2a
6m
6n
6o
5
96
1e
2b
5
92
1e
2c
4.5
24D
36D
3
93
1a
2d: R3 ¼ Ph; R4 ¼ OEt
2e: R3 ¼ Me; R4 ¼ Ph
2b
6p
6q
6r, 6s
32
1a
41
1f: R1 ¼ Ph; R2 ¼ Me
36, 25
AReaction conditions: 1 (1.0 mmol), 2 (1.0 mmol), NH4OAc (1.1 mmol).
BExtension of the reaction time did not improve the product yield.
CIsolated yield.
DReactions were performed at 65–708C.
O
O
O
O
NH2
Ph
NH4OAc, InCl3 (10 mol-%)
THF, reflux, 36h
Ph
Ph
Ph
Ph
Ph
O
9
1a
2f
Scheme 3. Reaction of 1a with 2f.
Cl3In
O
O
OH
O
O
O
OMe
Ph
O
Ph
H
ꢀ
MeO
Ph
OMe
Me
Me
O
2a
O
Ph
InCl3
1a
Me
O
O
O
O
H
Ph
Ph
Ph
OMe
H
OMe
H
Ph
NH4OAc
H
MeO
Me
O
Ph
O
O
O
InCl3
N
H
OH
Ph
O
NH
Me
O
Me
A
ꢁH2O
O
Ph
MeO
Me
O
N
Ph
H
6a
Scheme 4. Plausible mechanism for InCl3 catalyzed formation of substituted pyrrole 6a.

244
S. K. Mahato et al.
Table 3. Optimization of reaction conditions for the synthesis of 2-pyrone 8a
EntryA
Catalyst
Solvent
Time [h]B
YieldC [%]
1
None
THF
10
10
10
12
0
39
47
23
79
85
84
62
53
40
35
2
InCl3 (10 mol-%)
InCl3 (20 mol-%)
InCl3 (20 mol-%)
InCl3 (20 mol-%)
InCl3 (20 mol-%)
InCl3 (20 mol-%)
FeCl3 (20 mol-%)
ZnCl2 (20 mol-%)
AlCl3 (20 mol-%)
Montmorillonite K10 (20 wt-%)
THF
3
THF
4
CH3CN
MeOH
5
7.5
6
i-PrOH
i-PrOH/H2O (7 : 3)
i-PrOH
i-PrOH
i-PrOH
i-PrOH
6
8
7
8
15
11
24
24
9
10
11
AReaction conditions: 4a (1.0 mmol), 2b (1.0 mmol), reflux.
BExtension of the reaction time did not improve the product yield.
CIsolated yield.
Table 4. Synthesis of substituted 2-pyrones 8a f
]
O
O
R2
O
O
R1
R3
OEt
InCl3 (20 mol-%)
R3
ꢀ
O
i-PrOH, reflux
R2
R1
O
O
4
2
O
8
EntryA
1,4-Ynedione
b-Dicarbonyl
Product
Time [h]B
YieldC [%]
1
2
3
4
5
6
4a: R1 ¼ R2 ¼ Ph
2b: R3 ¼ Me
8a
8b
8c
8d
8e
8f
6
85[32]
76[32]
71
4b: R1 ¼ R2 ¼ 4-Me-C6H4
4c: R1 ¼ R2 ¼ 4-Cl–C6H4
4d: R1 ¼ R2 ¼ 4-Br-C6H4
2b
6
2b
7
2b
6.5
7
78
4e: R1 ¼ R2 ¼ 3-Cl–4-Me-C6H3
2b
62
4a
2d: R3 ¼ Ph
8
63
AReaction conditions: 4 (1.0 mmol), 2 (1.0 mmol).
BExtension of the reaction time did not improve the product yield.
CIsolated yield.
elevated temperature (Table 3, entry 2). Conducting the same
reaction in the absence of InCl3 did not generate any product,
instead 4a and 2b were fully recovered (Table 3, entry 1).
Increasing the InCl3 loading (20 mol %) improved the product
yield only marginally (Table 3, entry 3). The best yield of 8a was
achieved (Table 3, entry 6) by employing i-PrOH and 20 mol %
of InCl3 among the various combinations of solvent and Lewis
acid catalyst used in this reaction. It is important to mention that
the presence of water had very little effect on the formation of 8a
(Table 3, entry 7).
With the above optimized reaction condition in hand, we
turned our attention to prepare various other tri-substituted
2-pyrones 8b–f by reacting different 1,4-ynediones 4a–e[28a]
with either 2b or 2d. The results are summarised in Table 4.
Similarly, reaction between 4a and 2d afforded the 2-pyrone 8f
in reasonable yield (Table 4, entry 6).
The structures of both tetra-substituted pyrroles 6a–s and
tri-substituted 2-pyrones 8a–f have been deduced mainly by
NMR spectroscopy, mass spectrometry (MS), and elemental
analysis. Moreover the structures of 6a (Fig. 1), 6d, 6i, 6l, and 8a
(Fig. 2) have been confirmed by single crystal X-ray analysis
(see Supplementary Material).
Conclusion
In conclusion, we have developed simple indium trichloride
catalysed one-pot synthetic methodologies for the synthesis of
tetra-substituted pyrroles and tri-substituted 2-pyrones in
excellent yields under mild reaction conditions. Further studies
involving screening of these compounds for specific biological
activities are in progress and the results will be reported in due
course.
Experimental
Reaction of 4a, which acts as a Michael acceptor with the
Michael donor 2b results in Michael adduct B, which follows the
more preferred 6-exo-trig over 5-exo-trig cyclisation with
elimination of EtOH to form 2-pyrone 8a as the only product
instead of 3,30-bifuran 7 (Scheme 5).
Melting points were determined in open glass capillaries and are
uncorrected. NMR spectra were obtained using a Bruker DRX
600 (or Bruker AMX 300) NMR spectrometer with TMS
(tetramethylsilane) as the internal standard. IR spectra were

One-Pot Synthesis of Pyrroles and 2-Pyrones
245
Ph
O
O
O
InCl3
Ph
OH
O
O
O
•
O
Ph
ꢀ
O
Ph
Me
OEt
InCl3
CO2Et
Me
EtO
Me
InCl3
4a
2b
O
O
O
O
O
O
Ph
Ph
6-exo-trig
Ph
O
Ph
Ph
Ph
ꢁEtOH
Ph
Me
Ph
Me
C
O
O
Me
OH
OEt
O
CO2Et
C
C
H
HO
OEt
O
Me
O
O
O
B
8a
Me
O
O
OH
Ph
Ph
Ph
CO2Et
CO2Et
Ph
Ph
Ph
O
5-exo-trig
O
x
O
CO2Et
C
H
O
CO2Et
Me
Me
Me
B
7
Scheme 5. Plausible mechanism for InCl3 catalysed formation of substituted 2-pyrone 8a.
C9
O2
C11
C8
C10
C21
N1
O3
C12
C7
C20
C13
C5
C19
C6
C1
C14
O1
C15
C16
C4
C3
C18
C17
C2
Fig. 1. ORTEP diagram of compound 6a.
recorded on KBr discs and wavelengths are given in cmꢂ1. All
chemical shift and coupling constant (J) values are reported in
ppm and Hz respectively. Analytical thin-layer chromatography
(TLC) was carried out on Merck silica gel 60 F254 plates.
Column chromatography was done over silica gel 60–120 mesh.
were used as received from commercial sources, with the
exception of NH4OAc, which was vacuum dried overnight
before use.
General Procedure for the Synthesis of Tetra-Substituted
Pyrroles 6a–s
1
All final compounds were characterised by H, 13C, and 2D
NMR and MS analyses. Electron impact (EI) MS spectra were
recorded on a GCMS-Shimadzu-QP5050A and electrospray
ionization (ESI) MS spectra on a Waters Micromass Q-TOF
MicroTM spectrometer. Elemental analyses were performed on
a Perkin–Elmer CHN/O analyzer model 2400, series II. All
reactions were carried out under an argon atmosphere. THF was
dried by distillation over Na/benzophenone under a nitrogen
atmosphere and all the other solvents were dried by using
standard procedures. Anhydrous InCl3 and all other reagents
Anhydrous InCl3 (22 mg, 10 mol %) and NH4OAc (85 mg, 1.1
mmol) were added to a mixture of a 1,4-endione 1a–f (1 mmol)
and a b-dicarbonyl compound 2a–e (1 mmol) in dry THF
(15 mL). The reaction mixture was then stirred at an appropriate
temperature for the indicated time (Table 2, entries 1–18). After
complete disappearance of the starting material (monitored by
TLC using methanol/chloroform, 1 : 9), the solvent was evapo-
rated in a rotary evaporator. The reaction mixture was diluted
with water (10 mL) and extracted with CHCl3 (3 ꢃ 25 mL). The

246
S. K. Mahato et al.
C18
C8
C17
C7
C9
C16
C19
C20
O4
C15
C14
C3
C4
C6
C10
C5
O2
C11
C2
O3
C1
C13
O1
C12
Fig. 2. ORTEP diagram of compound 8a.
organic layer was separated, washed with brine, and then dried
over anhydrous Na2SO4. Removal of the solvent resulted in the
crude product, which was chromatographed over silica gel using
petroleum ether and increasing proportions of chloroform as
eluent to provide the products 6a–s.
2-(4-Acetyl-5-methyl-2-phenyl-1H-pyrrol-3-yl)-1-
phenyl Ethanone (6c)
Pale yellow powder; yield: 299 mg (94 %); mp 172–1748C;
Rf 0.2 (chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1
3217 (N–H), 1687 (C¼O), 1609 (C¼O), 1474, 1448, 1419,
1335, 1216. dH (600 MHz, CDCl3) 9.14 (br s, NH), 8.07 (d, J 7.2,
2H, ArH), 7.55 (t, J 7.5, 1H, ArH), 7.46 (t, J 7.8, 2H, ArH), 7.24–
7.16 (m, 5H, ArH), 4.44 (s, 2H, –C(O)CH2–), 2.37 (s, 3H,
–C(O)CH3), 2.27 (s, 3H, pyrrole ring 5-CH3). dC (150 MHz,
CDCl3) 199.9, 194.6, 137.5, 135.3, 132.7 (ArCH), 131.7, 130.2,
128.6 (2 ꢃ ArCH), 128.5 (2 ꢃ ArCH), 128.2 (2 ꢃ ArCH), 127.2
(2 ꢃ ArCH), 127.0 (ArCH), 121.4, 115.0, 36.8 (–C(O)CH2–),
30.3 (–C(O)CH3), 15.4 (pyrrole ring 5-CH3). m/z (ESI) 340
([M þ Na]þ). Anal. Calc. for C21H19NO2: C 79.47, H 6.03,
N 4.41. Found: C 79.42, H 6.00, N 4.51 %.
2-Methyl-4-(2-oxo-2-phenyl-ethyl)-5-phenyl-1H-
pyrrole-3-carboxylic Acid Methyl Ester (6a)
Light green crystals; yield: 319 mg (96 %); mp 158–1608C,
Rf 0.2 (chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1
3262 (N–H), 1702 (C¼O), 1662 (C¼O), 1447, 1343, 1261,
1220, 1139, 1095. dH (600 MHz, CDCl3) 8.56–8.49 (br s, NH),
8.07 (d, J 7.2, 2H, ArH), 7.57 (t, J 7.5, 1H, ArH), 7.48 (t, J 7.8,
2H, ArH), 7.30–7.22 (m, 5H, ArH), 4.43 (s, 2H, –C(O)CH2–),
3.55 (s, 3H, –OCH3), 2.50 (s, 3H, pyrrole ring 2-CH3). dC (150
MHz, CDCl3) 199.4 (–CH2C(O)Ph), 166.0 (–C(O)OCH3),
137.4, 136.5 (2C), 132.8 (ArCH), 132.0, 129.8 (ArCH), 128.9
(2 ꢃ ArCH), 128.5 (2 ꢃ ArCH), 128.2 (2 ꢃ ArCH), 127.3
(ArCH), 127.1 (ArCH), 114.9, 111.4, 50.4 (–OCH3), 36.4
(–C(O)CH2–), 14.0 (pyrrole ring 2-CH3). m/z (ESI) 356
([M þ Na]þ). Anal. Calc. for C21H19NO3: C 75.66, H 5.74,
N 4.20. Found: C 75.61, H 5.71, N 4.19 %.
2-Methyl-4-(2-oxo-2-p-tolyl-ethyl)-5-p-tolyl-1H-pyrrole-
3-carboxylic Acid Methyl Ester (6d)
Pale yellow powder; yield: 340 mg (94 %); mp 136–1388C;
Rf 0.2 (chloroform/petroleum ether, 3 : 1). nmax (KBr)/cm–1 3329
(N–H), 1683 (C¼O), 1657 (C¼O), 1448, 1334, 1264, 1181,
1094. dH (600 MHz, CDCl3) 8.32 (br s, NH), 7.96 (d, J 7.8, 2H,
ArH), 7.27 (d, J 8.4, 2H, ArH), 7.18 (d, J 7.8, 2H, ArH), 7.11 (d,
J 7.8, 2H, ArH), 4.38 (s, 2H, –C(O)CH2–), 3.56 (s, 3H, –OCH3),
2.52 (s, 3H), 2.42 (s, 3H), 2.32 (s, 3H). dC (150 MHz,
CDCl3) 198.8 (–CH2C(O)Ar), 166.0 (–C(O)OCH3), 143.4,
137.0, 136.1, 134.9, 129.8, 129.5 (2 ꢃ ArCH), 129.2, 129.1
(2 ꢃ ArCH), 128.3 (2 ꢃ ArCH), 127.3 (2 ꢃ ArCH), 114.7,
111.5, 50.4 (–OCH3), 36.3 (–C(O)CH2–), 21.6 (Ar-CH3),
21.2 (Ar-CH3), 14.0 (pyrrole ring 2-CH3). m/z (ESI) 384
([M þ Na]þ). Anal. Calc. for C23H23NO3: C 76.43, H 6.41,
N 3.88. Found: C 76.39, H 6.38, N 3.86 %.
2-Methyl-4-(2-oxo-2-phenyl-ethyl)-5-phenyl-1H-
pyrrole-3-carboxylic Acid Ethyl Ester (6b)
CAS Reg. No. 1326822-91-6. White powder; yield: 324 mg
(93 %); mp 182–1848C; Rf 0.2 (chloroform/petroleum ether,
3 : 1). nmax (KBr)/cmꢂ1 3316 (N–H), 1686 (C¼O), 1337, 1266,
1218, 1148, 1100. dH (600 MHz, CDCl3) 8.61 (br s, NH), 8.08
(d, J 8.1, 2H, ArH), 7.56 (t, J 7.5, 1H, ArH), 7.48 (t, J 7.8, 2H,
ArH), 7.28–7.19 (m, 5H, ArH), 4.45 (s, 2H, –C(O)CH2–), 4.05
(q, J 7.0, 2H, –OCH2CH3), 2.50 (s, 3H, pyrrole ring 2-CH3), 1.03
(t, J 7.2, 3H, –OCH2CH3). dC (150 MHz, CDCl3) 199.1
(–CH2C(O)Ph), 165.6 (–C(O)OCH2CH3), 137.3, 136.6, 132.8
(ArCH), 132.1, 129.7, 128.8 (2 ꢃ ArCH), 128.5 (2 ꢃ ArCH),
128.2 (2 ꢃ ArCH), 127.2 (2 ꢃ ArCH), 127.0 (ArCH), 114.6,
111.7, 59.1 (–OCH2CH3), 36.6 (–C(O)CH2–), 14.2, 14.0. m/z
(ESI) 370 ([M þ Na]þ). Anal. Calc. for C22H21NO3: C 76.06,
H 6.09, N 4.03. Found: C 76.02, H 6.07, N 4.01 %.
2-Methyl-4-(2-oxo-2-p-tolyl-ethyl)-5-p-tolyl-1H-pyrrole-
3-carboxylic Acid Ethyl Ester (6e)
White powder; yield: 345 mg (92 %); mp 248–2508C; Rf 0.2
(chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3347
(N–H), 1691 (C¼O), 1655 (C¼O), 1446, 1286, 1172, 1094.
dH (300 MHz, CDCl3) 8.18 (br s, NH), 7.97 (d, J 7.7, 2H, ArH),

One-Pot Synthesis of Pyrroles and 2-Pyrones
247
7.27 (d, J 7.7, 2H, ArH), 7.20 (d, J 7.7, 2H, ArH), 7.14 (d,
J 7.7, 2H, ArH), 4.41 (s, 2H, –C(O)CH2–), 4.08 (q, J 7.2,
2H, –OCH2CH3), 2.57 (s, 3H), 2.42 (s, 3H), 2.34 (s, 3H),
1.04 (t, J 7.2, 3H, –OCH2CH3). dC (75 MHz, CDCl3) 198.9
(–CH2C(O)Ar), 165.7 (–C(O)OCH2CH3), 143.5, 136.7, 136.4,
134.8, 129.7, 129.4 (2 ꢃ ArCH), 129.3, 129.1 (2 ꢃ ArCH),
128.3 (2 ꢃ ArCH), 127.1 (2 ꢃ ArCH), 114.3, 111.6, 59.0
(–OCH2CH3), 36.5 (–C(O)CH2–), 21.6, 21.1, 14.2, 14.0. m/z
(ESI) 398 ([M þ Na]þ). Anal. Calc. for C24H25NO3: C 76.77,
H 6.71, N 3.73. Found: C 76.72, H 6.67, N 3.70 %.
2-[4-Acetyl-2-(4-chloro-phenyl)-5-methyl-1H-pyrrol-3-
yl]-1-(4-chloro-phenyl) Ethanone (6i)
Pale yellow powder; yield: 359 mg (93 %); mp 228–2308C;
Rf 0.2 (chloroform/petroleum ether 3 : 1). nmax (KBr)/cmꢂ1 3202
(N–H), 1685 (C¼O), 1606 (C¼O), 1474, 1451, 1214, 1092. dH
(600 MHz, CDCl3) 8.38 (br s, NH), 8.02 (d, J 8.4, 2H, ArH), 7.45
(d, J 8.4, 2H, ArH), 7.30 (d, J 8.1, 2H, ArH), 7.22 (d, J 7.8, 2H,
ArH), 4.34 (s, 2H, –C(O)CH2–), 2.56 (s, 3H, –C(O)CH3), 2.37
(s, 3H, pyrrole ring 5–CH3). dC (150 MHz, CDCl3) 199.0, 194.3,
139.2, 135.8, 134.8, 133.5, 130.0, 129.7 (2 ꢃ ArCH), 129.3,
129.1 (2 ꢃ ArCH), 128.8 (2 ꢃ ArCH), 128.6 (2 ꢃ ArCH), 121.6,
115.7, 36.4 (–C(O)CH2–), 30.5 (–C(O)CH3), 15.7 (pyrrole ring
5-CH3). m/z (ESI) 408 ([M þ Na]þ). Anal. Calc. for
C21H17Cl2NO2: C 65.30, H 4.44, N 3.63. Found: C 65.24,
H 4.40, N 3.59 %.
2-(4-Acetyl-5-methyl-2-p-tolyl-1H-pyrrol-3-yl)-1-p-tolyl
Ethanone (6f)
White powder; yield: 325 mg (94 %); mp 170–1728C; Rf 0.2
(chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3216
(N–H), 1681 (C¼O), 1606 (C¼O), 1471, 1450, 1415, 1337,
1224, 1179. dH (300 MHz, CDCl3) 8.25 (br s, NH), 7.98 (d, J 8.0,
2H, ArH), 7.27 (d, J 8.0, 2H, ArH), 7.21 (d, J 7.4, 2H, ArH), 7.1
(d, J 7.4, 2H, ArH), 4.40 (s, 2H, –C(O)CH2–), 2.56 (s, 3H,
–C(O)CH3), 2.41 (s, 3H), 2.35 (s, 6H). dC (75 MHz, CDCl3)
200.0, 194.9, 143.8, 137.1, 135.6, 135.4, 130.7, 129.8 (2 ꢃ
ArCH), 129.6 (2 ꢃ ArCH), 129.4, 128.8 (2 ꢃ ArCH), 127.6
(2 ꢃ ArCH), 121.9, 115.2, 37.1 (–C(O)CH2–), 30.8 (–C(O)CH3),
22.1 (Ar-CH3), 21.6 (Ar-CH3), 15.9 (pyrrole ring 5-CH3). m/z
(ESI) 368 ([M þ Na]þ). Anal. Calc. for C23H23NO2: C 79.97,
H 6.71, N 4.05. Found: C 79.93, H 6.69, N 4.06 %.
5-(4-Bromo-phenyl)-4-[2-(4-bromo-phenyl)-2-oxo-
ethyl]-2-methyl-1H-pyrrole-3-carboxylic Acid Methyl
Ester (6j)
Pale yellow powder; yield: 457 mg (93 %); mp 156–1588C;
Rf 0.2 (chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1
3313 (N–H), 1685 (C¼O), 1660 (C¼O), 1483, 1448, 1266,
1095. dH (600 MHz, CDCl3) 8.74 (br s, NH), 7.94 (d, J 6.6, 2H,
ArH), 7.64 (d, J 6.6, 2H, ArH), 7.36 (d, J 8.4, 2H, ArH), 7.02 (d,
J 8.4, 2H, ArH), 4.34 (s, 2H, –C(O)CH2–), 3.59 (s, 3H, –OCH3),
2.43 (s, 3H, pyrrole ring 2-CH3). dC (150 MHz, CDCl3) 198.9
(–CH2C(O)Ar), 165.9 (–C(O)OCH3), 137.0, 135.9, 131.9 (4 ꢃ
ArCH), 130.8, 129.8 (2 ꢃ ArCH), 128.7 (2 ꢃ ArCH), 128.3,
128.2, 121.1, 115.0, 111.3, 50.6 (–C(O)OCH3), 36.3
(–C(O)CH2–), 13.9 (pyrrole ring 2-CH3). m/z (ESI) 514 ([M þ
Na]þ). Anal. Calc. for C21H17Br2NO3: C 51.35, H 3.49, N 2.85.
Found: C 51.39, H 3.45, N 2.81 %.
5-(4-Chloro-phenyl)-4-[2-(4-chloro-phenyl)-2-oxo-
ethyl]-2-methyl-1H-pyrrole-3-carboxylic Acid
Methyl Ester (6g)
White powder; yield: 386 mg (96 %); mp 62–648C; Rf 0.2
(chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3312
(N–H), 1682 (C¼O), 1588 (C¼O), 1487, 1450, 1265, 1214,
1142, 1091. dH (300 MHz, CDCl3) 9.14 (br s, NH), 8.04 (d, J 8.4,
2H, ArH), 7.49 (d, J 8.4, 2H, ArH), 7.16 (d, J 8.0, 2H, ArH), 7.04
(d, J 8.0, 2H, ArH), 4.37 (s, 2H, –C(O)CH2–), 3.60 (s, 3H,
–OCH3), 2.37 (s, 3H, pyrrole ring 2-CH3). dC (75 MHz, CDCl3)
199.5 (–CH2C(O)Ar), 166.5 (–C(O)OCH3), 140.0, 137.6,
135.9, 133.2, 130.8, 130.1 (2 ꢃ ArCH), 129.4 (2 ꢃ ArCH),
129.3 (2 ꢃ ArCH), 129.2, 128.3 (2 ꢃ ArCH), 115.3, 111.5,
50.9 (–C(O)OCH3), 36.8 (–C(O)CH2–), 14.2 (pyrrole ring
2-CH3). m/z (ESI) 424 ([M þ Na]þ). Anal. Calc. for
C21H17Cl2NO3: C 62.70, H 4.26, N 3.48. Found: C 62.67,
H 4.24, N 3.45 %.
5-(4-Bromo-phenyl)-4-[2-(4-bromo-phenyl)-2-oxo-
ethyl]-2-methyl-1H-pyrrole-3-carboxylic Acid Ethyl
Ester (6k)
White solid; yield: 475 mg (94 %); mp 106–1088C; Rf
0.2 (chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3601
(N–H), 1683 (C¼O), 1657 (C¼O), 1483, 1266, 1210, 1147,
1098. dH (600 MHz, CDCl3) 8.95 (br s, NH), 7.95 (d, J 8.4, 2H,
ArH), 7.63 (d, J 8.4, 2H, ArH), 7.31 (d, J 8.4, 2H, ArH), 6.95 (d,
J 8.4, 2H, ArH), 4.36 (s, 2H, –C(O)CH2–), 4.09 (q, J 7.0, 2H,
–OCH2CH3), 2.40 (s, 3H, pyrrole ring 2-CH3), 1.10 (t, J 7.2, 3H,
–OCH2CH3). dC (150 MHz, CDCl3) 198.8 (–CH2C(O)Ar),
165.5 (–C(O)OCH2CH3), 137.2, 135.8, 131.9 (2 ꢃ ArCH),
131.8 (2 ꢃ ArCH), 130.8, 129.8 (2 ꢃ ArCH), 128.6, 128.3,
128.2 (2 ꢃ ArCH), 120.9, 114.8, 111.5, 59.2 (–OCH2CH3),
36.5 (–C(O)CH2–), 14.3, 14.0. m/z (ESI) 528 ([M þ Na]þ).
Anal. Calc. for C22H19Br2NO3: C 52.30, H 3.79, N 2.77. Found:
C 52.24, H 3.76, N 2.74 %.
5-(4-Chloro-phenyl)-4-[2-(4-chloro-phenyl)-2-oxo-
ethyl]-2-methyl-1H-pyrrole-3-carboxylic Acid Ethyl
Ester (6h)
White solid; yield: 380 mg (91 %); mp 174–1768C; Rf 0.2
(chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3311
(N–H), 1680 (C¼O), 1487, 1444, 1334, 1263, 1213, 1143,
1091. dH (600 MHz, CDCl3) 8.65 (br s, NH), 8.02 (d, J 8.4,
2H, ArH), 7.46 (d, J 8.4, 2H, ArH), 7.22 (d, J 8.4, 2H, ArH), 7.10
(d, J 8.4, 2H, ArH), 4.37 (s, 2H, –C(O)CH2–), 4.09 (q, J 7.2, 2H,
–OCH2CH3), 2.47 (s, 3H, pyrrole ring 2-CH3), 1.09 (t, J 7.2, 3H,
–OCH2CH3). dC (150 MHz, CDCl3) 198.2 (–CH2C(O)Ar),
165.5 (–C(O)OCH2CH3), 139.5, 136.9, 135.5, 133.0, 130.4,
129.7 (2 ꢃ ArCH), 129.0 (2 ꢃ ArCH), 128.9 (2 ꢃ ArCH),
128.6, 128.2 (2 ꢃ ArCH), 114.9, 111.7, 59.2 (–OCH2CH3),
36.4 (–C(O)CH2–), 14.3, 14.0. m/z (ESI) 438 ([M þ Na]þ).
Anal. Calc. for C22H19Cl2NO3: C 63.47, H 4.60, N 3.36. Found:
C 63.42, H 4.57, N 3.34 %.
2-[4-Acetyl-2-(4-bromo-phenyl)-5-methyl-1H-pyrrol-
3-yl]-1-(4-bromo-phenyl) Ethanone (6l)
Pale yellow solid; yield: 442 mg (93 %); mp 114–1168C; Rf
0.2 (chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3198
(N–H), 1682 (C¼O), 1607 (C¼O), 1474, 1451, 1416, 1212,
1072. dH (600 MHz, CDCl3) 8.33 (br s, NH), 7.94 (d, J 6.9, 2H,
ArH), 7.62 (d, J 7.2, 2H, ArH), 7.47 (d, J 8.4, 2H, ArH), 7.17 (d,
J 8.4, 2H, ArH), 4.33 (s, 2H, –C(O)CH2–), 2.57 (s, 3H,
–C(O)CH3), 2.38 (s, 3H, pyrrole ring 5-CH3). dC (150 MHz,
CDCl3) 198.3, 194.2, 137.3, 136.6, 132.5 (4 ꢃ ArCH), 131.9,

248
S. K. Mahato et al.
130.9 (2 ꢃ ArCH), 130.0 (2 ꢃ ArCH), 129.1, 127.6, 121.9,
120.8, 116.0, 37.2 (–C(O)CH2–), 31.2 (–C(O)CH3), 15.7
(pyrrole ring 5-CH3). m/z (ESI) 498 ([M þ Na]þ). Anal. Calc.
for C21H17Br2NO2: C 53.08, H 3.61, N 2.95. Found: C 53.03,
H 3.58, N 2.90 %.
4-(2-Oxo-2-phenyl-ethyl)-2,5-diphenyl-1H-pyrrole-3-
carboxylic Acid Ethyl Ester (6p)
Light yellow solid; yield: 132 mg (32 %); mp 102–1048C; Rf
0.5 (ethyl acetate/petroleum ether, 1.5 : 8.5). nmax (KBr)/cmꢂ1
3300 (N–H), 2924, 1685 (C¼O), 1602 (C¼O), 1455. dH (600
MHz, CDCl3) 8.41 (br s, NH), 8.09 (d, J 7.8, 2H, ArH), 7.61–
7.56 (m, 3H, ArH), 7.49 (t, J 7.8, 2H, ArH), 7.42–7.30 (m, 8H,
ArH), 4.53 (s, 2H, –C(O)CH2–), 4.00 (q, J 7.2, 2H, –OCH2CH3),
0.92 (t, J 7.2, 3H, –OCH2CH3). dC (150 MHz, CDCl3) 198.4
(–CH2C(O)Ph), 165.0 (–C(O)OCH2CH3), 137.7, 137.3, 132.9
(ArCH), 132.6, 131.8, 131.7, 129.3 (2 ꢃ ArCH), 129.0 (2 ꢃ
ArCH), 128.5 (2 ꢃ ArCH), 128.2 (2 ꢃ ArCH), 128.0 (2 ꢃ
ArCH), 127.7 (2 ꢃ ArCH), 127.6 (2 ꢃ ArCH), 116.1, 112.5,
59.5 (–OCH2CH3), 36.6 (–C(O)CH2–), 13.9 (–OCH2CH3). m/
z (ESI) 432 ([M þ Na]þ). Anal. Calc. for C27H23NO3: C 79.20,
H 5.66, N 3.42. Found: C 79.27, H 5.72, N 3.35 %.
5-(3-Chloro-4-methyl-phenyl)-4-[2-(3-chloro-4-methyl-
phenyl)-2-oxo-ethyl]-2-methyl-1H-pyrrole-3-carboxylic
Acid Methyl Ester (6m)
White powder; yield: 413 mg (96 %); mp 128–1308C; Rf
0.2 (chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3300
(N–H), 1690 (C¼O), 1480, 1444, 1261, 1140, 1096. dH (600
MHz, CDCl3) 8.94 (br s, NH), 7.95 (s, 1H, ArH), 7.84 (d, J 8.4,
1H, ArH), 7.45 (d, J 8.4, 1H, ArH), 7.14 (d, J 7.8, 1H, ArH), 6.94
(s, 1H, ArH), 6.88 (d, J 7.8, 1H, ArH), 4.35 (s, 2H, –C(O)CH2–),
3.60 (s, 3H, –OCH3), 2.58 (s, 3H), 2.45 (s, 3H), 2.21 (s, 3H,
pyrrole ring 2-CH3). dC (150 MHz, CDCl3) 199.3 (–CH2C(O)Ar),
165.5 (–C(O)OCH3), 139.5, 137.2, 137.0, 136.5, 135.6,
133.0, 130.6 (ArCH), 130.5, 129.5 (ArCH), 129.4 (ArCH),
129.3 (ArCH), 128.7, 127.4 (ArCH), 125.9 (ArCH), 114.8,
111.1, 50.5 (–OCH3), 36.4 (–C(O)CH2–), 20.2 (Ar-CH3),
20.1 (Ar-CH3), 13.8 (pyrrole ring 2-CH3). m/z (ESI) 452
([M þ Na]þ). Anal. Calc. for C23H21Cl2NO3: C 64.19, H 4.92,
N 3.25. Found: C 64.11, H 4.90, N 3.24 %.
2-(4-Benzoyl-5-methyl-2-phenyl-1H-pyrrol-3-yl)-1-
phenyl Ethanone (6q)
Yellow solid; yield: 155 mg (41 %); mp 127–1298C; Rf 0.5
(ethyl acetate/petroleum ether, 1 : 9). nmax (KBr)/cmꢂ1 3289
(N–H), 2923, 2854, 1682 (C¼O), 1598 (C¼O), 1421, 1211. dH
(600 MHz, CDCl3) 8.51 (br s, NH), 7.99 (d, J 7.8, 2H, ArH), 7.64
(d, J 7.2, 2H, ArH), 7.52 (t, J 7.5, 1H, ArH), 7.45–7.40 (m, 3H,
ArH), 7.37 (t, J 7.5, 2H, ArH), 7.34–7.23 (m, 5H, ArH), 4.41 (s,
2H, –C(O)CH2–), 1.99 (s, 3H, pyrrole ring 5-CH3). dC (150 MHz,
CDCl3) 199.0, 194.1, 141.3, 137.3, 134.6, 132.7 (ArCH), 131.9,
131.2 (2 ꢃ ArCH), 130.7, 128.8 (2 ꢃ ArCH), 128.7 (2 ꢃ ArCH),
128.4 (2 ꢃ ArCH), 128.3 (2 ꢃ ArCH), 128.2 (2 ꢃ ArCH), 127.2
(2 ꢃ ArCH), 121.7, 114.1, 29.6 (–C(O)CH2–), 14.2 (pyrrole ring
5-CH3). m/z (EI) 379 (85 %, Mþ), 274 (100), 259 (12), 230 (8),
196 (7), 105(21), 77 (17). Anal. Calc. for C26H21NO2: C 82.30,
H 5.58, N 3.69. Found: C 82.43, H 5.65, N 3.65 %.
5-(3-Chloro-4-methyl-phenyl)-4-[2-(3-chloro-4-methyl-
phenyl)-2-oxo-ethyl]-2-methyl-1H-pyrrole-3-carboxylic
Acid Ethyl Ester (6n)
White powder; yield: 409 mg (92 %); mp 190–1928C; Rf 0.2
(chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3291
(N–H), 1695 (C¼O), 1676 (C¼O), 1479, 1449, 1262, 1138,
1096. dH (600 MHz, CDCl3) 8.97 (br s, NH), 7.95 (s, 1H, ArH),
7.86 (d, J 8.4, 1H, ArH), 7.45 (d, J 8.4, 1H, ArH), 7.13 (d, J 8.4,
1H, ArH), 6.92 (s, 1H, ArH), 6.87 (d, J 7.8, 1H, ArH), 4.40
(s, 2H, –C(O)CH2–), 4.10 (q, J 7.2, 2H, –OCH2CH3), 2.45
(s, 3H), 2.39 (s, 3H), 2.20 (s, 3H), 1.11 (t, J 7.2, 3H, –OCH2CH3).
dC (150 MHz, CDCl3) 198.5 (–CH2C(O)Ar), 165.5
(–C(O)OCH2CH3), 139.6, 137.1, 136.7, 136.1, 135.6, 132.9,
130.6 (ArCH), 130.5, 129.3 (ArCH), 129.2 (ArCH), 129.1
(ArCH), 128.9, 127.4 (ArCH), 125.4 (ArCH), 114.7, 111.3,
59.1 (–OCH2CH3), 36.6 (–C(O)CH2–), 20.5 (2C), 14.3, 13.9.
m/z (ESI) 466 ([M þ Na]þ). Anal. Calc. for C24H23Cl2NO3:
C 64.87, H 5.22, N 3.15. Found: C 64.81, H 5.17, N 3.15 %.
2-Methyl-4-(2-oxo-propyl)-5-phenyl-1H-pyrrole-3-
carboxylic Acid Ethyl Ester (6r)
Light yellow solid; yield: 103 mg (36 %); mp 138–1408C; Rf
0.2 (chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3311
(N–H), 2924, 1689 (C¼O), 1605 (C¼O), 1446, 1358, 1263,
1163, 1094. dH (600 MHz, CDCl3) 8.44 (br s, NH), 7.33 (t, J 7.5,
2H, ArH), 7.28–7.23 (m, 3H, ArH), 4.24 (q, J 7.2, 2H,
–OCH2CH3), 3.85 (s, 2H, –C(O)CH2–), 2.50 (s, 3H, pyrrole
ring 2-CH3), 2.27 (s, 3H, –CH2C(O)CH3), 1.32 (t, J 7.2, 3H,
–OCH2CH3). dC (150 MHz, CDCl3) 208.5 (–CH2C(O)CH3),
165.7 (–C(O)CH2CH3), 136.1 (pyrrole ring 2-C), 131.9, 129.5
(pyrrole ring 4-C), 128.8 (2 ꢃ ArCH), 127.3 (2 ꢃ ArCH), 127.2
(ArCH), 115.0 (pyrrole ring 5-C), 111.5 (pyrrole ring 3-C), 59.3
(–OCH2CH3), 41.1 (–C(O)CH2–), 29.8 (–C(O)CH3), 14.5
(pyrrole ring 2-CH3), 14.1 (–OCH2CH3). m/z (ESI) 308
([M þ Na]þ). Anal. Calc. for C17H19NO3: C 71.56, H 6.71,
N 4.91. Found: C 71.63, H 6.77, N 4.84 %.
2-[4-Acetyl-2-(3-chloro-4-methyl-phenyl)-5-methyl-1H-
pyrrol-3-yl]-1-(3-chloro-4-methyl-phenyl) Ethanone (6o)
White solid; yield: 385 mg (93 %); mp 175–1778C; Rf 0.2
(chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3278
(N–H), 1679 (C¼O), 1615 (C¼O), 1476, 1446, 1231, 1050.
dH (600 MHz, CDCl3) 9.10 (br s, NH), 7.95 (s, 1H, ArH), 7.84
(d, J 8.4, 1H, ArH), 7.44 (d, J 8.4, 1H, ArH), 7.24 (d, J 8.4,
1H, ArH), 7.07 (s, 1H, ArH), 7.00 (d, J 8.7, 1H, ArH), 4.33
(s, 2H, –C(O)CH2–), 2.49 (s, 3H), 2.44 (s, 3H), 2.34 (s, 3H), 2.03
(s, 3H, pyrrole ring 5-CH3). dC (150 MHz, CDCl3) 199.7, 194.4,
139.5, 136.5, 135.9, 135.3, 133.3, 131.1 (ArCH), 130.7, 130.1,
129.4 (ArCH), 129.3 (ArCH), 129.1 (ArCH), 128.9, 127.1
(ArCH), 125.8 (ArCH), 121.4, 115.2, 36.7 (–C(O)CH2–), 30.4
(–C(O)CH3), 20.4 (Ar-CH3), 20.1 (Ar-CH3), 15.5 (pyrrole ring
5-CH3). m/z (ESI) 436 ([M þ Na]þ). Anal. Calc. for
C23H21Cl2NO2: C 66.67, H 5.11, N 3.38. Found: C 66.62,
H 5.08, N 3.33 %.
2,5-Dimethyl-4-(2-oxo-2-phenyl-ethyl)-1H-pyrrole-3-
carboxylic Acid Ethyl Ester (6s)
Yellow solid; yield: 71 mg (25 %); mp 122–1248C; Rf 0.2
(chloroform/petroleum ether, 3 : 1). nmax (KBr)/cmꢂ1 3329
(N–H), 2924, 2855, 1680 (C¼O), 1447, 1342, 1267, 1213,
1130. dH (600 MHz, CDCl3) 8.14 (br s, NH), 8.08 (d, J 7.8,
2H, ArH), 7.55 (t, J 7.2, 1H, ArH), 7.47 (t, J 7.8, 2H, ArH), 4.35
(s, 2H, –C(O)CH2–), 4.09 (q, J 7.2, 2H, –OCH2CH3), 2.43 (s,
3H, pyrrole ring 2-CH3), 2.08 (s, 3H, pyrrole ring 5-CH3), 1.09

One-Pot Synthesis of Pyrroles and 2-Pyrones
249
(t, J 7.2, 3H, –OCH2CH3). dC (150 MHz, CDCl3) 198.5
(–CH2C(O)Ph), 165.8 (–C(O)CH2CH3), 137.3, 134.5 (pyrrole
ring 2-C), 132.7 (ArCH), 128.4 (2 ꢃ ArCH), 128.2 (2 ꢃ ArCH),
124.3 (pyrrole ring 5-C), 113.1 (pyrrole ring 4-C), 110.3 (pyrrole
ring 3-C), 58.9 (–OCH2CH3), 35.7 (–C(O)CH2–), 14.2 (pyrrole
ring 5-CH3), 13.9 (pyrrole ring 2-CH3), 10.7 (–OCH2CH3). m/z
(ESI) 308 ([M þ Na]þ). Anal. Calc. for C17H19NO3: C 71.56, H
6.71, N 4.91. Found: C 71.65, H 6.80, N 4.81 %.
7.83–7.76 (m, 4H, ArH), 7.50–7.46 (m, 4H, ArH), 6.61 (s, 1H,
pyrone ring 5-CH), 2.63 (s, 3H, 3-C(O)CH3). dC (150 MHz,
CDCl3) 195.2, 192.6, 164.6 (pyrone ring 2-C(O)O–), 160.1,
159.3, 140.7, 139.5, 132.7, 129.9 (2 ꢃ ArCH), 129.8 (2 ꢃ
ArCH), 129.4 (2 ꢃ ArCH), 128.1, 127.9 (2 ꢃ ArCH), 117.9,
100.7 (pyrone ring 5-CH), 30.6 (3-C(O)CH3). m/z (ESI) 409
([M þ Na]þ). Anal. Calc. for C20H12Cl2O4: C 62.04, H, 3.12.
Found: C 62.10, H 3.09 %.
3-Acetyl-4-(4-bromo-benzoyl)-6-(4-bromo-phenyl)-
pyran-2-one (8d)
General Procedure for the Synthesis of Tri-Substituted
2-Pyrones 8a–f
Yellow solid; yield: 371 mg (78 %); mp 250–2528C; Rf 0.5
(ethyl acetate/petroleum ether, 5 : 95). nmax (KBr)/cmꢂ1 1728
(C¼O), 1663 (C¼O), 1605 (C¼O), 1483. dH (600 MHz, CDCl3)
7.76 (d, J 9.0, 2H, ArH), 7.69 (d, J 8.4, 2H, ArH), 7.66–7.63 (m,
4H, ArH), 6.62 (s, 1H, pyrone ring 5-CH), 2.63 (s, 3H,
3-C(O)CH3). dC (150 MHz, CDCl3) 195.2, 192.8, 164.7 (pyrone
ring 2-C(O)O–), 160.1, 159.2, 133.1, 132.7 (2 ꢃ ArCH), 132.4
(2 ꢃ ArCH), 130.0 (2 ꢃ ArCH), 129.4, 128.6, 128.1, 128.0
(2 ꢃ ArCH), 118.0, 100.7 (pyrone ring 5-CH), 30.6
(3-C(O)CH3). m/z (ESI) 499 ([M þ Na]þ). Anal. Calc. for
C20H12Br2O4: C 50.45, H 2.54. Found: C 50.39, H 2.51 %.
Anhydrous InCl3 (44 mg, 20 mol %) was added to a mixture of a
diaroyl acetylene 4a–f (1 mmol) and b-dicarbonyl 2b or 2d
(1 mmol) in dry isopropyl alcohol (10 mL). The reaction mixture
turned reddish-brown after a few minutes of stirring at 80–858C;
stirring was continued at that temperature for the indicated time
(Table 4, entry 1–6). The reaction was monitored by TLC using
CHCl3/petroleum ether (3 : 2). The solvent was removed under
reduced pressure, water (10 mL) was added, and the reaction
mixture was extracted with CHCl3 (3 ꢃ 10 mL). The organic
layer was washed with water (3 ꢃ 10 mL) and then with brine
(10 mL). The combined organic layers were dried over anhy-
drous Na2SO4. The solvent was removed to give an oily mass,
which was chromatographed over silica gel using petroleum
ether with an increasing proportion of ethyl acetate as eluent to
provide the products 8a–f.
3-Acetyl-4-(3-chloro-4-methyl-benzoyl)-6-(3-chloro-4-
methyl-phenyl)-pyran-2-one (8e)
Yellow solid; yield: 258 mg (62 %); mp 170–1728C; Rf 0.5
(ethyl acetate/petroleum ether, 5 : 95). nmax (KBr)/cmꢂ1 1735
(C¼O), 1672 (C¼O), 1607 (C¼O), 1477. dH (600 MHz, CDCl3)
7.78 (d, J 1.8, 1H, ArH), 7.72 (d, J 1.8, 1H, ArH), 7.65 (dd, J 8.4,
2.4, 1H, ArH), 7.56 (dd, J 8.1, 2.1, 1H, ArH), 7.47 (d, J 8.4, 1H,
ArH), 7.45 (d, J 8.4, 1H, ArH), 6.61 (s, 1H, pyrone ring 5-CH),
2.63 (s, 3H, 3-C(O)CH3), 2.44 (s, 3H, Ar-CH3), 2.43 (s, 3H,
Ar-CH3). dC (150 MHz, CDCl3) 195.3, 193.0, 164.8 (pyrone
ring 2-C(O)O–), 160.4, 159.5, 140.9, 139.7, 137.7, 137.3, 132.7,
130.8 (ArCH), 130.1 (ArCH), 129.8 (ArCH), 128.9 (ArCH),
128.1, 127.3 (ArCH), 125.3 (ArCH), 117.7, 100.8 (pyrone ring
5-CH), 30.7 (3-C(O)CH3), 20.2 (2 ꢃ ArCH3). m/z (ESI) 437
([M þ Na]þ). Anal. Calc. for C22H16Cl2O4: C 63.63, H 3.88.
Found: C 63.55, H 3.80 %.
3-Acetyl-4-benzoyl-6-phenyl-pyran-2-one (8a)
Yellow solid; yield: 273 mg (85 %); mp 134–1368C (Lit.[32]
135–1378C); Rf 0.5 (ethyl acetate/petroleum ether, 4 : 96). nmax
(KBr)/cmꢂ1 1733 (C¼O), 1665 (C¼O), 1605 (C¼O), 1484. dH
(600 MHz, CDCl3) 7.90 (d, J 7.8, 2H, ArH), 7.85 (d, J 7.2, 2H,
ArH), 7.63–7.49 (m, 6H, ArH), 6.68 (s, 1H, pyrone ring 5-CH),
2.64 (s, 3H, 3-C(O)CH3). dC (150 MHz, CDCl3) 195.3, 194.0,
165.5 (pyrone ring 2-C(O)O–), 160.8, 159.7, 134.3, 134.1
(ArCH), 132.9 (ArCH), 129.8, 129.3 (2 ꢃ ArCH), 129.0 (2 ꢃ
ArCH), 128.7 (2 ꢃ ArCH), 126.9 (2 ꢃ ArCH), 117.8, 100.9
(pyrone ring 5-CH), 30.7 (3-C(O)CH3). m/z (ESI) 341 ([M þ
Na]þ). Anal. Calc. for C20H14O4: C 75.46, H 4.43. Found:
C 75.41, H 4.45 %.
3,4-Dibenzoyl-6-phenyl-pyran-2-one (8f)
3-Acetyl-4-(4-methyl-benzoyl)–6-p-tolyl-pyran-2-one
(8b)
Yellow solid; yield: 242 mg (63 %); mp 156–1588C; Rf 0.5
(ethyl acetate/petroleum ether, 4 : 96). nmax (KBr)/cmꢂ1 1728
(C¼O), 1778 (C¼O), 1607 (C¼O), 1499, 1263. dH (300 MHz,
CDCl3) 7.89–7.79 (m, 5H, ArH), 7.63–7.39 (m, 10H, ArH), 6.80
(s, 1H, pyrone ring 5-CH). dC (75 MHz, CDCl3) 193.2, 191.5,
163.2 (pyrone ring 2-C(O)O–), 159.3, 156.2, 136.3, 134.6
(ArCH), 134.3, 133.8 (ArCH), 132.3 (ArCH), 130.1, 129.6
(2 ꢃ ArCH), 129.3 (2 ꢃ ArCH), 129.2 (2 ꢃ ArCH), 128.9 (2 ꢃ
ArCH), 128.4 (2 ꢃ ArCH), 126.2 (2 ꢃ ArCH), 122.2, 100.4
(pyrone ring 5-CH). m/z (ESI) 403 ([M þ Na]þ). Anal. Calc.
for C25H16O4: C 78.94, H 4.24. Found: C 79.03, H 4.30 %.
Yellow solid; yield: 262 mg (76 %); mp 126–1288C (Lit.[32]
127–1308C); Rf 0.5 (ethyl acetate/petroleum ether, 5 : 95). nmax
(KBr)/cmꢂ1 1734 (C¼O), 1667 (C¼O), 1609 (C¼O), 1483. dH
(300 MHz, CDCl3) 7.81–7.72 (m, 4H, ArH), 7.31–7.26 (m, 4H,
ArH), 6.62 (s, 1H, pyrone ring 5-CH), 2.62 (s, 3H, 3-C(O)CH3),
2.43 (s, 6H, Ar-CH3). dC (75 MHz, CDCl3) 195.7, 194.1, 166.1
(pyrone ring 2-C(O)O–), 161.4, 160.3, 145.5, 144.3, 132.4,
130.5 (2 ꢃ ArCH), 130.1 (2 ꢃ ArCH), 129.2 (2 ꢃ ArCH),
127.6, 127.1 (2 ꢃ ArCH), 117.7, 100.8 (pyrone ring 5-CH),
31.0 (3-C(O)CH3), 22.2 (Ar-CH3), 22.1 (Ar-CH3). m/z (ESI)
369 ([M þ Na]þ). Anal. Calc. for C22H18O4: C 76.29, H 5.24.
Found: C 76.24, H 5.29 %.
3-Amino-1,3-diphenylprop-2-en-1-one (9)
White solid; yield: 172 mg (77 %); mp 76–788C [lit.[31] mp
78–798C]. dH (600 MHz, CDCl3) 10.43 (br s, NH), 7.96–7.94
(m, 2H, ArH), 7.65–7.63 (m, 2H, ArH), 7.52–7.42 (m, 6H, ArH),
6.16 (s, 1H, ¼CH–), 5.44 (br s, NH). dC (150 MHz, CDCl3)
190.2 (PhC(O)CH¼), 162.8 (C-NH2), 140.3, 137.6, 131.1
(ArCH), 130.7 (ArCH), 129.1 (2 ꢃ ArCH), 128.3 (2 ꢃ ArCH),
127.2 (2 ꢃ ArCH), 126.3 (2 ꢃ ArCH), 91.9 (¼CH–). m/z (ESI)
3-Acetyl-4-(4-chloro-benzoyl)-6-(4-chloro-phenyl)-
pyran-2-one (8c)
Yellow solid; yield: 275 mg (71 %); mp 244–2468C; Rf 0.5
(ethyl acetate/petroleum ether, 5 : 95). nmax (KBr)/cmꢂ1 1733
(C¼O), 1663 (C¼O), 1607 (C¼O), 1481. dH (600 MHz, CDCl3)

250
S. K. Mahato et al.
246 ([M þ Na]þ). Anal. Calc. for C15H13NO: C 80.69, H 5.87,
(b) G. Minetto, L. F. Raveglia, M. Taddei, Org. Lett. 2004, 6, 389.
doi:10.1021/OL0362820
N 6.27. Found: C 80.61, H 5.94, N, 6.19 %.
(c) B. K. Banik, S. Samajdar, I. J. Banik, J. Org. Chem. 2004, 69, 213.
doi:10.1021/JO035200I
Supplementary Material
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1H and 13C NMR spectra for compounds 6a–s and 8a–f and
ORTEP diagrams of 6d, 6i, and 6l are available on the Journal’s
website. The CCDC numbers of 6a, 6d, 6i, 6l, and 8a are
759230, 836577, 836578, 836579, and 869936. These data can
be obtained free of charge from the Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
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Acknowledgements
This project was funded by the Council of Scientific and Industrial Research
(CSIR), New Delhi, India in the form of Network Project (ORIGIN). Author
S.K.M. thanks the CSIR, New Delhi, India for award of Senior Research
Fellowship (SRF). Thanks are also due to Mr. Partha Mitra of Department of
Inorganic Chemistry, IACS, Kolkata, India for his help in refining raw data
of X-ray analysis.
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