Synthesis of 4-(1,3-dioxo-2,3-dihydro-1H-2-indenyl) substituted 1-benzylpyrrole-3-carboxylates via a tandem four-component reaction

Article abstract of DOI:10.1016/j.crci.2012.10.003

An efficient approach for the preparation of functionalized 4-(1,3-dioxo-2,3-dihydro-1H-2-indenyl) substituted 1-benzylpyrrole-3- carboxylates is described. This four-component reaction between ninhydrin, 1-phenyl-2-(1,1,1-triphenyl-λ⁵-phosphanylidene)-1-ethanone, primary amines and alkyl acetoacetate proceeds in MeOH under reflux condition in good to excellent yields.

Full text of DOI:10.1016/j.crci.2012.10.003

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CRAS2C-3629; No. of Pages 4
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Full paper/Memoire
Synthesis of 4-(1,3-dioxo-2,3-dihydro-1H-2-indenyl) substituted
1-benzylpyrrole-3-carboxylates via a tandem four-component reaction
*
Abdolali Alizadeh , Javad Mokhtari
Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175 Tehran, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
An efficient approach for the preparation of functionalized 4-(1,3-dioxo-2,3-dihydro-1H-
2-indenyl) substituted 1-benzylpyrrole-3-carboxylates is described. This four-component
reaction between ninhydrin, 1-phenyl-2-(1,1,1-triphenyl-l5-phosphanylidene)-1-etha-
none, primary amines and alkyl acetoacetate proceeds in MeOH under reflux condition in
good to excellent yields.
Received 28 June 2012
Accepted after revision 3 October 2012
Available online xxx
Keywords:
Pyrroles
ß 2012 Published by Elsevier Masson SAS on behalf of Acade´mie des sciences.
Ninhydrin
1-Phenyl-2-(1,1,1-triphenyl-l5
phosphanylidene)-1-ethanone
Enaminone
-
Multicomponent reaction
1. Introduction
vitamin B12, and various cytochrome enzymes [4]. Some of
the recently isolated pyrrole containing marine natural
Multicomponent reactions (MCRs) are excellent strate-
gies, being employed in the synthesis of many natural
products. These MCRs are generally defined as reactions
where more than two starting materials react to form a
product, incorporating more or less all the atoms of the
starting materials [1]. The MCRs offer a wide range of
advantages such as a single-step procedure, avoiding
complicated purification processes and saving both
solvents and reagents.
The MCRs have attracted considerable interest owing to
their exceptional synthetic efficiency. Recently, there has
been tremendous development in three- and four-compo-
nent reactions [2].
products has been found to exhibit considerable cytotox-
icity and to function as multidrug-resistant reversal agents
[5]. Many of these biologically active compounds have
emerged as chemotherapeutic agents. In addition, poly-
substituted pyrroles are molecular frameworks with
immense importance in material science [6].
Consequently, a wide range of procedures have been
devised for the synthesis of pyrroles [7]. However, many of
the methods are associated with various drawbacks such
as harsh reaction conditions, tedious experimental proce-
dures, unsatisfactory yields, and long reaction times.
Moreover, the number of methods for the synthesis of
polysubstituted pyrroles is relatively limited. Herein we
report an efficient, new approach for the synthesis of
polysubstituted pyrroles.
As part of our program aimed at developing new
reactions for the preparation of heterocyclic compounds
[8], very recently, we have reported the synthesis of novel
spiro[indoline-3,40-pyridine]-30-carboxylates 1 and spir-
o[indole-3,60-[1,3]thiazin]-2-ones 2 (Fig. 1) by using of 1-
phenyl-2-(1,1,1-triphenyl-l5-phosphanylidene)-1-etha-
none as a new important reagent in heterocyclic synthesis
based on a one-pot reaction [9].
Five-membered, N-containing heterocycles are impor-
tant building blocks of an extensive number of biologically
active compounds [3]. Among them, pyrroles are hetero-
cycles of great importance because of their presence
in numerous natural products like heme, chlorophyll,
* Corresponding author.
E-mail addresses: aalizadeh@modares.ac.ir, abdol_alizad@yahoo.com
(A. Alizadeh).
1631-0748/$ – see front matter ß 2012 Published by Elsevier Masson SAS on behalf of Acade´mie des sciences.
http://dx.doi.org/10.1016/j.crci.2012.10.003
Please cite this article in press as: Alizadeh A, Mokhtari J. Synthesis of 4-(1,3-dioxo-2,3-dihydro-1H-2-indenyl)
substituted 1-benzylpyrrole-3-carboxylates via a tandem four-component reaction. C. R. Chimie (2012), http://
dx.doi.org/10.1016/j.crci.2012.10.003

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A. Alizadeh, J. Mokhtari / C. R. Chimie xxx (2012) xxx–xxx
R
Table 1
R
N
S
Me
Synthetic results of 5 under different reactions conditions.
N
Entry
Solvent
Temp
Time/h
Yield (%)a
S
R'
R'
1
2
3
4
5
Methanol
Ethanol
Reflux
Reflux
Reflux
Reflux
Reflux
12
8
87
73
61
65
25
O
O
Acetonitrile
THF
8
N
H
N
H
10
10
Dichloromethane
1
2
a
Isolated yield
Fig. 1. A new class of important spiroheterocyclic compounds.
Table 2
Synthesis of polysubstituted pyrroles.
Also, in continuation of our works on this reagent,
we have observed that the reaction between ninhydrin,
1-phenyl-2-(1,1,1-triphenyl-l5-phosphanylidene)-1-
ethanone, and alkyl acetoacetae in presence of different
amines in MeOH produced the corresponding substituted
pyrroles at reflux condition (Scheme 1).
Product
R
R’
Time
Yield (%)
5a
5b
5c
5d
5e
5f
C6H5CH2-
Me
Et
6
8
87
83
84
86
81
86
82
C6H5CH2-
4-ClC6H4CH2-
4-ClC6H4CH2-
4-MeC6H4CH2-
C6H5-
Me
Et
6
7
Me
Me
Me
8
8
5g
n-Butyl
10
2. Results and discussion
The choice of an appropriate reaction medium is of
crucial importance for successful synthesis. Initially, the
four-component reaction of ninhydrin and 1-phenyl-2-
(1,1,1-triphenyl-l5-phosphanylidene)-1-ethanone in the
presence of benzylamine and methyl acetoacetate as a
simple model substrate was investigated to establish the
feasibility of the strategy and to optimize the reaction
conditions.
four-component reaction makes possible the synthesis of
libraries under similar circumstances (Table 2).
The structures of compounds 5a–g were deduced from
their elemental analysis, IR and high-field 1H and 13C NMR
spectra. The mass spectrum of 5a displayed the molecular
ion peak at m/z = 449, which is in agreement with the
proposed structure. The IR spectrum of this compound
showed absorption bands due to the CH at 2947 and the
C = O group at 1694 cmꢀ1. The 1H NMR spectrum of 5a
showed four singlet signals for the CH3, OCH3, CH, and CH2
Different solvents such as methanol, ethanol, acetoni-
trile, tetrahydrofuran (THF) and dichloromethane were
explored. The results are summarized in Table 1.
groups at
and the aromatic moieties gave rise to multiplets in the
aromatic region of the spectrum ( = 6.93–8.01 ppm). The
d = 2.44, 3.05, 4.16 and 5.05 ppm respectively,
As can be seen in Table 1, the best result was obtained
by refluxing the reaction mixture in methanol to yield
product 5a in good yield (Table 1, Entry 1). Encouraged by
this success, we extended this reaction of ninhydrin with
1-phenyl-2-(1,1,1-triphenyl-l5-phosphanylidene)-1-
ethanone, alkyl acetoacetate 3 and a range of aromatic and
aliphatic amines 4 with both electron withdrawing and
electron releasing substituents under similar conditions
(MeOH), and corresponding pyrroles 5 were synthesized in
high yields (81–87%) and the results are summarized in
Table 2. We have shown that the use of a wide diversity of
substituents in amines 4 and alkyl acetoacetate 3 in this
d
1H-decoupled 13C NMR spectrum of 5a showed 21 distinct
resonances in agreement with the suggested structure.
Although we have not established the mechanism of
reaction experimentally, a possible explanation is pro-
posed in Scheme 2. Compound 5 could result from the
initial addition of the amine to alkyl acetoacetate and
subsequent attack of the resulting reactive enaminone 7 on
the compound 6 to yield intermediate 8. Cyclization of the
intermediate 8 and subsequent loss of H2O lead to
compound 5.
O
O
O
O
O
R'
Me
O
O
O
Ph
R
O
N
MeOH
reflux
3
Me
Ph3P
R-NH2
O
R'
O
Ph
5
4
Scheme 1. Synthesis of polysubstituted pyrroles.
Please cite this article in press as: Alizadeh A, Mokhtari J. Synthesis of 4-(1,3-dioxo-2,3-dihydro-1H-2-indenyl)
substituted 1-benzylpyrrole-3-carboxylates via a tandem four-component reaction. C. R. Chimie (2012), http://
dx.doi.org/10.1016/j.crci.2012.10.003

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3
O
O
O
O
Ph3P
Ph
O
O
Ph
O
O
6
R
O
O
NH
O
R'
R'
R-NH2
Me
O
Me
7
O
O
Ph
HN
H2O
5
6
7
R
O
O
O
8
R'
Scheme 2. Probing the mechanism for the formation of title compounds.
3. Conclusions
reaction mixture was stirred for 6 h under reflux condi-
tions and the progress of the reaction was followed by thin
layer chromatography. When the reaction mixture was
cooled to room temperature, a white solid precipitated.
The precipitates were filtered and washed with diethyl
ether to give product 5a in 87% yields. All products gave
satisfactory spectral data in accordance with the assigned
structures.
In summary, a simple and easy approach has been
developed for the quick construction of alkyl benzyl-4-
(2,3-dihydro-1,3-dioxo-1H-2-indenyl)-1H-pyrrole-3-
carboxylates 5 by the reaction of amines, alkyl acetoace-
tate, ninhydrin and 1-phenyl-2-(1,1,1-triphenyl-l5
-
phosphanylidene)-1-ethanone. These types of hetero-
cycles contain a number of functional groups and are
therefore valuable precursors for diversity-oriented
synthesis of pyrroles libraries, which are of potential
uses in the facile preparation of biologically active
molecules.
4.3. Spectral data
Methyl 1-benzyl-4-(1,3-dioxo-2,3-dihydro-1H-2-
indenyl)-2-methyl-5-phenyl-1H-3-pyrrolecarboxylate
(5a): White crystals (yield 87%); mp: 214-216 8C; IR (KBr)
4. Experimental
(n
max, cmꢀ1): 2947 (CH), 1694 (C = O), 1447 (Ar). 1H NMR
(500.13 MHz, CDCl3): dH (ppm) 2.44 (3H, s, CH3), 3.05 (3H, s,
4.1. Materials and techniques
OCH3), 4.16 (1H, s, CH), 5.05 (2H, s, CH2), 6.93 (2H, d,
3JHH = 7.2 Hz, 2 CH of Ar), 7.25 (1H, t, 3JHH = 6.8 Hz, CH of Ar),
7.31 (5H, m, 5 CH of Ar), 7.40 (2H, m, 2 CH of Ar), 7.81-7.83
(2H, m, 2 CH of Ar), 8.00- 8.01 (2H, m, 2 CH of Ar). 13C NMR
(125.8 MHz, CDCl3): dC (ppm) 11.85, 48.02, 49.50, 54.95,
109.30, 112.78, 122.90, 125.68, 127.31, 128.56, 128.61,
128.82, 130.30, 131.19, 134.77, 137.08, 137.19, 137.48,
141.73, 164.63, 199.00. MS (EI, 70 eV): m/z (%) = 449 (M+,
12), 417 (38), 326 (20), 73 (100). Anal. calcd for C29H23NO4
(449.50): C, 77.49; H, 5.16; N, 3.12%. Found: C, 77.42; H,
5.10; N, 3.06%.
All reactions were carried out in oven-dried glassware.
Progress of reactions was monitored by thin layer chroma-
tography while purification was effected by column
chromatography, using silica gel (Merck 230-240 mesh).
Melting points were measured on an Electrothermal 9100
apparatus. Elemental analyses for C,
H and N were
performed using a Heraeus CHN–O–Rapid analyzer. Mass
spectra were recorded on a FINNIGAN-MATT 8430 mass
spectrometer operating at an ionization potential of 70 eV.
1H and 13C NMR spectra were measured (CDCl3) with a
Bruker DRX-500 AVANCE spectrometer at 500.1 and
125.8 MHz, respectively. IR spectra were recorded on a
Shimadzu IR-460 spectrometer; absorbencies are reported
Ethyl 1-benzyl-4-(1,3-dioxo-2,3-dihydro-1H-2-inde-
nyl)-2-methyl-5-phenyl-1H-3-pyrrolecarboxylate (5b):
White crystals (yield 83%); mp: 205-207 8C; IR (KBr) (nmax
,
cmꢀ1): 2926 (CH), 1683 (C = O), 1448 (Ar). 1H NMR
in cmꢀ1
.
(500.13 MHz, CDCl3): dH (ppm) 0.84 (3H, t, JHH = 5.8 Hz,
3
CH3), 2.44 (3H, s, CH3), 3.65 (2H, q, 3JHH = 5.8 Hz, CH2), 4.17
(1H, s, CH), 5.05 (2H, s, CH2), 6.94 (2H, d, 3JHH = 6.4 Hz, 2 CH
of Ar), 7.25 (1H, m, CH of Ar), 7.32 (5H, m, 5 CH of Ar), 7.39
(2H, m, 2 CH of Ar), 7.81 (2H, m, 2 CH of Ar), 7.99 (2H, m, 2
CH of Ar). 13C NMR (125.8 MHz, CDCl3): dC (ppm) 11.52,
13.54, 47.53, 54.75, 58.46, 109.23, 112.17, 122.39, 125.22,
126.80, 128.06, 128.08, 128.32, 129.87, 130.69, 134.27,
136.53, 136.70, 136.75, 141.29, 163.94, 198.44. MS (EI,
70 eV): m/z (%) = 463 (M+, 46), 417 (68), 326 (42), 298 (38),
4.2. General procedure for the preparation of compounds 5a–
g, exemplified on 5a
A solution of 1-phenyl-2-(1,1,1-triphenyl-l5-phospha-
nylidene)-1-ethanone (0.38 g, 1 mmol), ninhydrin (0.16 g,
1 mmol) was magnetically stirred in 5 mL of MeOH for
20 min. Then, benzylamine (0.11 g, 1 mmol) and methyl
acetoacetate (1.2 mmol) were added simultaneously. The
Please cite this article in press as: Alizadeh A, Mokhtari J. Synthesis of 4-(1,3-dioxo-2,3-dihydro-1H-2-indenyl)
substituted 1-benzylpyrrole-3-carboxylates via a tandem four-component reaction. C. R. Chimie (2012), http://
dx.doi.org/10.1016/j.crci.2012.10.003

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91(100). Anal. calcd for C30H25NO4 (463.53): C, 77.74; H,
5.44; N, 3.02%. Found: C, 77.69; H, 5.36; N, 2.98%.
Methyl 1-(4-chlorobenzyl)-4-(1,3-dioxo-2,3-dihy-
dro-1H-2-indenyl)-2-methyl-5-phenyl-1H-3-pyrrole-
carboxylate (5c): White crystals (yield 84%); mp: 210-
212 8C; IR (KBr) (n
max, cmꢀ1): 2924 (CH), 1710 (2 C = O),
Ar), 7.98-7.99 (2H, m, 2 CH of Ar). 13C NMR (125.8 MHz,
CDCl3): dC (ppm) 11.23, 12.91, 19.27, 32.07, 43.76, 48.86,
54.42, 108.03, 111.89, 122.39, 128.01, 128.05, 130.33,
130.89, 134.23, 135.77, 136.41, 141.18, 164.13, 198.68. MS
(EI, 70 eV): m/z (%) = 415 (M+, 82), 383 (100), 341 (42), 56
(20). Anal. Calcd. for C26H25NO4 (415.49): C, 75.16; H, 6.06;
N, 3.37%. Found: C, 75.11; H, 6.01; N, 3.30%.
1684 (CO2Me), 1453 (Ar). 1H NMR (500.13 MHz, CDCl3): dH
(ppm) 2.43 (3H, s, CH3), 3.05 (3H, s, OCH3), 4.14 (1H, s, CH),
5.01 (2H, s, CH2), 6.85 (2H, d, 3JHH = 8.1 Hz, 2 CH of Ar), 7.28
(2H, d, 3JHH = 8.2 Hz, 2 CH of Ar), 7.29-7.37 (5H, m, 5 CH of
Ar), 7.82-7.83 (2H, m, 2 CH of Ar), 8.00-8.01 (2H, m, 2 CH of
Ar). 13C NMR (125.8 MHz, CDCl3): dC (ppm) 11.32, 46.90,
49.08, 54.40, 109.02, 112.48, 122.44, 126.55, 128.16,
128.25, 128.53, 129.60, 130.62, 132.72, 134.34, 135.20,
136.48, 136.75, 141.20, 164.05, 198.44. MS (EI, 70 eV): m/z
(%) = 483 (M+, 26), 451 (74), 326 (64), 298 (58), 125 (100).
Anal. Calcd. for C29H22ClNO4 (483.95): C, 71.97; H, 4.58; N,
2.89%. Found: C, 71.90; H, 4.54; N, 2.85%.
Methyl 4-(1,3-dioxo-2,3-dihydro-1H-2-indenyl)-2-
methyl-1,5-diphenyl-1H-3-pyrrolecarboxylate (5g):
White crystals (yield 82%); mp: 217-220 8C; IR (KBr) (nmax
cmꢀ1): 2924 (CH), 1707 (CO2Me), 1526, 1441 (Ar). 1H NMR
(500.13 MHz, CDCl3): H (ppm) 2.37 (3H, s, CH3), 3.10 (3H,
,
d
s, OCH3), 4.32 (1H, s, CH), 7.13-7.16 (5H, m, 5 CH of Ar), 7.22
(2H, m, 2 CH of Ar), 7.31 (3H, m, 3 CH of Ar), 7.84 (2H, m, 2
CH of Ar), 8.03 (2H, m, 2 CH of Ar). 13C NMR (125.8 MHz,
CDCl3): dC (ppm) 12.41, 49.18, 54.49, 109.01, 112.25,
122.50, 127.23, 127.58, 127.61, 128.00, 128.42, 129.91,
130.37, 134.37, 136.56, 137.01, 137.78, 141.73, 164.23,
198.58. MS (EI, 70 eV): m/z (%) = 435 (M+, 34), 403 (100),
104 (24), 77 (76). Anal. Calcd. for C28H21NO4 (435.48): C,
77.23; H, 4.86; N, 3.22%. Found: C, 77.18; H, 4.80; N, 3.17%.
Ethyl 1-(4-chlorobenzyl)-4-(1,3-dioxo-2,3-dihydro-
1H-2-indenyl)-2-methyl-5-phenyl-1H-3-pyrrolecarbox-
ylate (5d): White crystals (yield 86%); mp: 256-258 8C; IR
(KBr) (
(CO2Et), 1446 (Ar). 1H NMR (500.13 MHz, CDCl3):
n
max, cmꢀ1): 2960, 2922 (CH), 1713 (2 C = O), 1674
Acknowledgements
dH (ppm)
0.84 (3H, t, 3JHH = 5.9 Hz, CH3), 2.43 (3H, s, CH3), 3.65 (2H, q,
3JHH = 5.9 Hz, CH2), 4.15 (1H, s, CH), 5.01 (2H, s, CH2), 6.86
(2H, d, 3JHH = 7.0 Hz, 2 CH of Ar), 7.28-7.36 (7H, m, 7 CH of
We gratefully acknowledge financial support from the
Research Council of Tarbiat Modares University.
Ar), 7.81 (2H, m, 2 CH of Ar), 7.99 (2H, m, 2 CH of Ar). 13
C
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136.42, 136.48, 141.26, 163.86, 198.35. MS (EI, 70 eV): m/z
(%) = 497 (M+, 42), 451 (82), 326 (84), 298 (72), 125 (100).
Anal. Calcd. for C30H24 ClNO4 (497.97): C, 72.36; H, 4.86; N,
2.81%. Found: C, 72.30; H, 4.80; N, 2.77%.
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105 (100). Anal. calcd for C30H25NO4 (463.53): C, 77.74; H,
5.44; N, 3.02%. Found: C, 77.69; H, 5.40; N, 2.98%.
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nyl)-2-methyl-5-phenyl-1H-3-pyrrolecarboxylate (5f):
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,
cmꢀ1): 2927 (CH), 1707 (C = O), 1533, 1439 (Ar). 1H NMR
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(e) A. Alizadeh, A. Rezvanian, L.G. Zhu, Journal of Organic Chemistry 77
(2012) 4385.
3
(500.13 MHz, CDCl3): dH (ppm) 0.78 (3H, t, JHH = 7.3 Hz,
CH3), 1.15-1.19 (2H, m, CH2), 1.49-1.54 (2H, m, CH2), 2.57
3
(3H, s, CH3), 3.02 (3H, s, OCH3), 3.77 (2H, t, JHH = 8.2 Hz,
CH2-N), 4.06 (1H, s, CH), 7.38-7.43 (3H, m, 3 CH of Ar), 7.48
(2H, d, 3JHH = 7.2 Hz, 2 CH of Ar), 7.80-7.81 (2H, m, 2 CH of
[9] (a) A. Alizadeh, J. Mokhtari, Tetrahedron 67 (2011) 3519;
(b) A. Alizadeh, J. Mokhtari, Helvet. Chim. Acta. 94 (2011) 1315.
Please cite this article in press as: Alizadeh A, Mokhtari J. Synthesis of 4-(1,3-dioxo-2,3-dihydro-1H-2-indenyl)
substituted 1-benzylpyrrole-3-carboxylates via a tandem four-component reaction. C. R. Chimie (2012), http://
dx.doi.org/10.1016/j.crci.2012.10.003