One-pot three-component reaction of ninhydrin, 1,3-dicarbonyl compounds, and primary amines to afford indeno[1,2-b]pyrrol-4(1H)-ones

Article abstract of DOI:10.1007/s10593-018-2388-6

[Figure not available: see fulltext.] A convenient one-pot three-component synthesis of indeno[1,2-b]pyrrol-4(1H)-ones has been developed. The reaction of ninhydrin, 1,3-dicarbonyl compounds, and primary amines in the presence of PPh₃ in MeCN at room temperature produces the respective indeno-[1,2-b]pyrrol-4(1H)-ones in high yields. The synthesized pyrrole derivatives have been used in the Diels–Alder reaction with dialkyl acetylenedicarboxylates in MeCN under reflux conditions to obtain indeno[1,2-b]pyrano[3,4-d]pyrroles in high yields.

Full text of DOI:10.1007/s10593-018-2388-6

DOI 10.1007/s10593-018-2388-6
Chemistry of Heterocyclic Compounds 2018, 54(11), 1040–1044
One-pot three-component reaction of ninhydrin,
1,3-dicarbonyl compounds, and primary amines
to afford indeno[1,2-b]pyrrol-4(1H)-ones
Hossein Karami1, Zinatossadat Hossaini1*,
Maryam Sabbaghan2*, Faramarz Rostami-Charati3
1 Department of Chemistry, Qaemshahr Branch, Islamic Azad University,
P. O. Box 14515-775, Qaemshahr, Iran; e-mail: zshossaini@yahoo.com
2 Department of Chemistry, Faculty of Sciences, Shahid Rajaee Teacher Training University,
P. O. Box 16785-163, Tehran, Iran; e-mail: msaba16us@yahoo.com
3 Department of Chemistry, Faculty of Science, Gonbad Kavous University,
P. O. Box 163, Gonbad, Iran; e-mail: f_rostami_ch@yahoo.com
Published in Khimiya Geterotsiklicheskikh Soedinenii,
2018, 54(11), 1040–1044
Submitted September 15, 2018
Accepted October 22, 2018
A convenient one-pot three-component synthesis of indeno[1,2-b]pyrrol-4(1H)-ones has been developed. The reaction of ninhydrin,
1,3-dicarbonyl compounds, and primary amines in the presence of PPh3 in MeCN at room temperature produces the respective indeno-
[1,2-b]pyrrol-4(1H)-ones in high yields. The synthesized pyrrole derivatives have been used in the Diels–Alder reaction with dialkyl
acetylenedicarboxylates in MeCN under reflux conditions to obtain indeno[1,2-b]pyrano[3,4-d]pyrroles in high yields.
Keywords: dialkyl acetylenedicarboxylate, 1,3-dicarbonyl compound, ninhydrin, primary amine, pyrrole, Diels–Alder reaction, three-
component reaction.
Pyrrole and its derivatives are highly important com-
pounds because of the broad range of its biological
activities. They have been employed as antibacterial,1 anti-
tumor,2 anti-inflammatory,3 and antifungal agents.4 Pyrrole
core has been also incorporated in a cholesterol-lowering drug
atorvastatin.5 In addition, several pyrroles display signi-
ficant antioxidative properties6 or have been successfully
exploited as intermediates in the synthesis of numerous
natural products, agrochemicals, flavorings, dyes, and
functional materials.7 Pyrrole derivatives have been used as
chemosensors in production of lasers and image recogni-
tion.8 Polysubstituted pyrroles have been used as anti-
bacterial,9 inotropic,10 antitumor,11 anti-inflammatory,3 and
antifungal agents12 and antioxidants.6b Finally, indeno[1,2-b]-
pyrroles exhibit a wide range of biological activities.13
According to the aforementioned, pyrrole is one of the
most broadly available heterocyclic motif in bioactive
natural products, drugs, and materials. For this reason,
synthesis and application of substituted pyrroles have
attracted increased attention.14 Conventionally used proce-
dures for preparation of functionalized pyrroles involve the
Paal–Knorr, Hantzsch, and Knorr reactions. Recently,
advanced synthetic strategies for obtaining substituted
pyrroles have been developed. These methods include ring
opening cyclization,15 multicomponent reactions,16 cyclo-
addition,17 oxidative coupling reactions,18 isocyanide-based
reactions,19 rearrangement reactions,20 hydroamination/
cyclizations,21 and aza-Wittig reactions.22 Although these
divergent synthetic approaches are useful, many of them
require utilization of catalysts, elevated temperatures, and
relatively complex substrates.14f,23 Therefore, the develop-
ment of efficient procedures for the synthesis of functio-
nalized pyrroles using structurally simple and readily
available starting materials is still an important subject of
interest.24
Previously, a reaction of ninhydrin, 1,3-dicarbonyl com-
pounds, and primary amines was investigated and
dihydroxypyrroles were obtained at room temperature
without exploitation of any catalyst.25 Herein, we report a
synthesis of indeno[1,2-b]pyrrol-4(1H)-ones under mild
and catalyst-free conditions using ninhydrin, 1,3-dicarbo-
nyl compounds, primary amines, and PPh3.
0009-3122/18/54(11)-1040©2018 Springer Science+Business Media, LLC
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Chemistry of Heterocyclic Compounds 2018, 54(11), 1040–1044
Scheme 1
Functionalized pyrroles 1a–g were obtained in high
Table 1. Optimization of solvent for the synthesis
of indeno[1,2-b]pyrrol-4(1H)-one 1a*
yields via the reaction of ninhydrin (2), 1,3-dicarbonyl
compounds 3a,b, primary amines 4a–g, and PPh3 in MeCN
at room temperature (Scheme 1). The simplicity of the
demonstrated method suggests that it may be an interesting
alternative to the complex multistep approaches. The
synthesis was performed without any catalyst. However,
PPh3 played a crucial role in this reaction. Without PPh3,
the respective dihydroxypyrroles25 were generated, whereas
addition of PPh3 to the reaction mixture promoted the
formation of indeno[1,2-b]pyrrol-4(1H)-ones13 and sub-
sequent elimination of triphenylphosphine oxide.
Entry
Solvent
Yield, %
Entry
Solvent
Yield, %
1
2
3
4
5
CH2Cl2
CHCl3
DMF
67
72
6
7
H2O
–
–**
45
To provide the most suitable reaction conditions, effect
of different solvents and temperatures on formation of
pyrrole derivative 1a was examined. Solvents, such as
MeCN, DMF, H2O, PhMe, and Et2O, and solvent-free
conditions were tested. Among them, MeCN provided the
highest yield of product 1a (Table 1, entry 8). The most
favorable temperature for this chemical transformation was
room temperature. Increase in the temperature did not
change the yield of indeno[1,2-b]pyrrol-4(1H)-one 1a.
Therefore, the highest yield (92%) of product 1a was
obtained when the reaction was performed in MeCN at
room temperature.
58
8
MeCN
EtOH
THF
92
PhMe
Et2O
78
9
38
–**
10
54
* Reaction conditions: ninhydrin (2) (356 mg, 2 mmol), pentane-2,4-dione
(3a) (200 mg, 2 mmol), methylamine (4a) solution in THF (2 M, 0.1 ml,
2 mmol), PPh3 (524 mg, 2 mmol), MeCN (7 ml), rt, 3 h.
** The reaction did not proceed.
(Scheme 2). Enaminone 5, produced in initial reaction of
pentane-2,4-dione (3a) and methylamine (4a), as a nucleo-
phile attacks ninhydrin (2) and generates intermediate 6.
Adduct 6 is then converted into compound 7 by elimination
of H2O, and intermediate 7 further reacts with PPh3 to
produce zwitterion 8. Finally, elimination of triphenyl-
phosphine oxide leads to the formation of product 1a.
The obtained indeno[1,2-b]pyrrol-4(1H)-ones 1a–c were
further used in synthesis of other pyrrole derivatives 9a–c.
The Diels–Alder reaction of compounds 1a–c and dialkyl
acetylenedicarboxylates 10a,b in MeCN under reflux
conditions furnished the respective indeno[1,2-b]pyrano-
[3,4-d]pyrroles 9a–c in high yields (Scheme 3). Two
slightly different procedures were tested for the synthesis
of products 9a–c. In the first one, compounds 1a–c were
not isolated and dialkyl acetylenedicarboxylates 10a,b
The structures of compounds 1a–g were assigned by IR,
1H and 13C NMR spectroscopic and mass spectral data. For
example, three singlets of methyl group protons at 2.52,
2.83, and 3.54 ppm along with signals of aromatic moiety
were observed in the 1H NMR spectrum of product 1a. The
13C NMR spectrum of indeno[1,2-b]pyrrol-4(1H)-one 1a,
containing signals of two carbonyl groups at 188.3 and
191.2 ppm, was in agreement with the proposed structure.
Furthermore, a peak of molecular ion with m/z 239 was
observed in the mass spectrum of compound 1a. Product 1c
has been described previously.26
A plausible mechanism for the formation of compounds
1a–g has been proposed on an example of pyrrole 1a
Scheme 2
Scheme 3
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Chemistry of Heterocyclic Compounds 2018, 54(11), 1040–1044
were added directly to the initial reaction mixture which
EtOAc, 5:1). After completion of the reaction (3 h), MeCN
was evaporated and the residue was purified by column
chromatography (silica gel, eluent hexane–EtOAc, 5:1).
3-Acetyl-1,2-dimethylindeno[1,2-b]pyrrol-4(1H)-one
(1a). Yield 440 mg (92%), pale-yellow powder, mp 138–
140°C. Rf 0.87. IR spectrum, ν, cm–1: 1727, 1725, 1694,
1584, 1487, 1357. 1H NMR spectrum, δ, ppm (J, Hz): 2.52
(3H, s, 2-CH3); 2.83 (3H, s, C(O)CH3); 3.54 (3H, s, NCH3);
was then refluxed for 4 h. In the second procedure, indeno-
[1,2-b]pyrrol-4(1H)-ones 1a–c were separated from the
starting mixture and further exploited in the reaction with
activated acetylenic compounds 10a,b, performed in
MeCN under reflux conditions for 4 h. Both of the tested
methods ensured the formation of products 9a–c. However,
the yields of indeno[1,2-b]pyrano[3,4-d]pyrroles 9a–c,
obtained in a one-pot synthesis, were lower than those
achieved in the second procedure.
3
3
7.53 (1H, d, J = 7.6, H Ar); 7.58 (1H, d, J = 7.5, H Ar);
3
3
7.63 (1H, t, J = 7.6, H Ar); 7.74 (1H, t, J = 7.6, H Ar).
13C NMR spectrum, δ, ppm: 14.2 (CH3); 31.3 (CH3); 36.3
(CH3); 109.2 (C); 120.8 (C Ar); 124.8 (C Ar); 125.2 (C);
128.6 (C Ar); 132.2 (C); 135.3 (C Ar); 142.6 (C); 148.2
(C); 148.7 (C); 188.3 (C=O); 191.2 (C=O). Mass spectrum,
m/z (Irel, %): 239 [M]+ (15), 196 [M–C2H3O]+ (84), 43
[CH3C≡O]+ (100). Found, %: C 75.43; H 5.62; N 5.97.
C15H13NO2. Calculated, %: C 75.30; H 5.48; N 5.85.
The structures of compounds 9a–c were confirmed by
IR, 1H and 13C NMR spectroscopic and mass spectral data.
For example, three singlets of methyl group protons at
1.56, 2.35, and 3.12 ppm, two singlets of carbomethoxy
group protons at 3.75 and 3.83 ppm, and signals of
1
aromatic moiety were observed in H NMR spectrum of
indeno[1,2-b]pyrano[3,4-d]pyrrole 9a. The 13C NMR
spectrum of compound 9a, containing signals of three
carbonyl groups at 161.3, 165.3, and 188.4 ppm was in
agreement with the proposed structure. In addition, a peak
of molecular ion with m/z 381 was present in the mass
spectrum of product 9a.
3-Acetyl-1-ethyl-2-methylindeno[1,2-b]pyrrol-4(1H)-
one (1b). Yield 456 mg (90%), pale-yellow powder, mp
145–147°C. IR spectrum, ν, cm–1: 1732, 1728, 1687, 1589,
1
1462, 1373. Rf 0.52. H NMR spectrum, δ, ppm (J, Hz):
1.15 (3H, t, 3J = 7.4, NCH2CH3); 2.53 (3H, s, 2-CH3); 2.95
3
In summary, a reaction of ninhydrin, 1,3-dicarbonyl
compounds, primary amines, and PPh3 in MeCN at room
temperature has been studied and indeno[1,2-b]pyrrol-
4(1H)-ones have been obtained in high yields. These
compounds have been used in the Diels–Alder reaction
with dialkyl acetylenedicarboxylates to produce the respective
indeno[1,2-b]pyrano[3,4-d]pyrroles in high yields. The
advantages of the developed synthetic procedures are mild
and clean reaction conditions, short reaction times, and
high yields of the products. Moreover, the reactions
proceed smoothly without exploitation of a catalyst and
without activation or modification of the starting materials
prior to the synthesis.
(3H, s, C(O)CH3); 4.25 (2H, q, J = 7.4, NCH2CH3); 7.45
(1H, d, 3J = 7.6, H Ar); 7.54 (1H, t, 3J = 7.5, H Ar); 7.72 (1H,
3
3
d, J = 7.6, H Ar); 7.83 (1H, t, J = 7.6, H Ar). 13C NMR
spectrum, δ, ppm: 14.3 (CH3); 16.2 (CH3); 31.5 (CH3); 43.2
(CH2CH3); 109.3 (C); 121.2 (C Ar); 125.2 (C Ar); 125.5 (C);
128.7 (C Ar); 132.4 (C); 134.8 (C Ar); 142.7 (C); 147.6
(C); 148.3 (C); 187.6 (C=O); 192.3 (C=O). Mass spectrum,
m/z (Irel, %): 253 [M]+ (15), 210 [M–C2H3O]+ (78), 43
[CH3C≡O]+ (100). Found, %: C 75.96; H 6.12; N 5.68.
C16H15NO2. Calculated, %: C 75.87; H 5.97; N 5.53.
3-Acetyl-2-methyl-1-phenylindeno[1,2-b]pyrrol-4(1H)-
one (1c).26 Yield 470 mg (78%), pale-yellow powder, mp 163–
165°C. IR spectrum, ν, cm–1: 1730, 1727, 1696, 1564,
1
1487, 1378. Rf 0.38. H NMR spectrum, δ, ppm (J, Hz):
Experimental
2.52 (3H, s, 2-CH3); 2.83 (3H, s, C(O)CH3); 7.04 (1H, d,
3
IR spectra were acquired on a Shimadzu IR-460 spectro-
3J = 7.6, H Ar); 7.18 (1H, t, J = 7.5, H Ar); 7.28 (2H, t,
1
3
meter using KBr pellets. H and 13C NMR spectra were
3J = 7.5, H Ar); 7.36 (2H, d, J = 7.6, H Ar); 7.58 (1H, t,
3
recorded on a Bruker FT-500 spectrometer (500 and
126 MHz, respectively) in CDCl3 solutions, and TMS was
applied as internal standard. Mass spectra were obtained on
a Finnigan-MAT 8430 spectrometer using EI method
(70 eV). Elemental analyses were performed on a
PerkinElmer model 240-C instrument. Melting points were
determined on an Electrothermal 9100 apparatus. The
reaction progress was monitored by TLC on Silica gel 60G
F254 glass plates, visualization under UV light.
3J = 7.6, H Ar); 7.65 (1H, d, J = 7.6, H Ar); 7.76 (1H, t,
3J = 7.6, H Ar). 13C NMR spectrum, δ, ppm: 15.2 (CH3);
31.4 (CH3); 113.8 (C); 120.4 (C Ar); 122.8 (2C Ar); 124.6
(C Ar); 125.7 (C Ar); 128.3 (C Ar); 129.4 (2C Ar); 131.7
(C); 135.4 (C Ar); 142.5 (C); 145.6 (C); 147.2 (C); 147.8
(C); 188.2 (C=O); 192.5 (C=O). Mass spectrum, m/z (Irel, %):
301 [M]+ (15), 258 [M–C2H3O]+ (64), 77 [C6H5]+ (68), 43
[CH3C≡O]+ (100). Found, %: C 79.85; H 5.18; N 4.78.
C20H15NO2. Calculated, %: C 79.72; H 5.02; N 4.65.
All reagents were purchased from Fluka and employed
without further purification. Methylamine (4a) and ethyl-
amine (4b) were applied as 2 M solutions in THF.
3-Acetyl-1-benzyl-2-methylindeno[1,2-b]pyrrol-4(1H)-
one (1d). Yield 536 mg (85%), pale-yellow powder, mp 175–
177°C. IR spectrum, ν, cm–1: 1735, 1728, 1697, 1585,
1489, 1374. Rf 0.29. 1H NMR spectrum, δ, ppm (J, Hz): 2.12
(2H, s, NCH2); 2.52 (3H, s, 2-CH3); 2.83 (3H, s, C(O)CH3);
Synthesis of indeno[1,2-b]pyrrol-4(1H)-ones 1a–g
(General method). A solution of 1,3-dicarbonyl compound
3a,b (2 mmol) and primary amine 4a–g (2 mmol) in MeCN
(5 ml) was prepared and stirred at room temperature for
30 min. Ninhydrin (2) (356 mg, 2 mmol) was added and
the reaction mixture was stirred at room temperature for
15 min. Subsequently, a solution of PPh3 (524 mg, 2 mmol)
in MeCN (2 ml) was slowly added to the mixture, and the
reaction progress was monitored by TLC (eluent hexane–
3
3
7.12 (1H, d, J = 7.6, H Ar); 7.23 (1H, t, J = 7.5, H Ar);
3
3
7.32 (2H, t, J = 7.5, H Ar); 7.43 (2H, d, J = 7.6, H Ar);
3
3
7.64 (1H, t, J = 7.6, H Ar); 7.73 (1H, d, J = 7.6, H Ar);
3
7.85 (1H, t, J = 7.6, H Ar). 13C NMR spectrum, δ, ppm:
14.5 (CH3); 31.6 (CH3); 47.3 (CH2); 109.2 (C); 120.5
(C Ar); 124.3 (C Ar); 124.8 (C); 128.5 (C Ar); 129.2
(2C Ar); 129.8 (2C Ar); 130.7 (C Ar); 132.3 (C); 135.2
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Chemistry of Heterocyclic Compounds 2018, 54(11), 1040–1044
(C Ar); 135.8 (C); 143.2 (C); 147.3 (C); 147.6 (C); 188.4
(2 mmol) was added to a stirred solution of indeno[1,2-b]-
pyrrol-4(1H)-one 1a–c (2 mmol) in MeCN (6 ml). The
mixture was refluxed, and the reaction progress was moni-
tored by TLC (eluent hexane–EtOAc, 7:1). After comple-
tion of the reaction (4 h), the mixture was cooled down and
MeCN was evaporated. The residue was purified by column
chromatography (silica gel, eluent hexane–EtOAc, 7:1).
Dimethyl 1,4a,5-trimethyl-10-oxo-4a,5-dihydro-10H-
indeno[1,2-b]pyrano[3,4-d]pyrrole-3,4-dicarboxylate (9a).
Yield 0.63 g (83%), pale-yellow powder, mp 172–174°C.
IR spectrum, ν, cm–1: 1743, 1727, 1695, 1587, 1465, 1325.
(C=O); 193.6 (C=O). Mass spectrum, m/z (Irel, %): 315 [M]+
(10), 272 [M–C2H3O]+ (68), 91 [C7H7]+ (88), 43 [CH3C≡O]+
(100). Found, %: C 80.12; H 5.58; N 4.62. C21H17NO2.
Calculated, %: C 79.98; H 5.43; N 4.44.
3-Acetyl-1-(4-methoxybenzyl)-2-methylindeno[1,2-b]-
pyrrol-4(1H)-one (1e). Yield 601 mg (87%), yellow
powder, mp 181–183°C. IR spectrum, ν, cm–1: 1729, 1725,
1
1696, 1578, 1487, 1375. Rf 0.25. H NMR spectrum, δ, ppm
(J, Hz): 2.15 (2H, s, NCH2); 2.54 (3H, s, 2-CH3); 2.85 (3H,
3
s, C(O)CH3); 3.78 (3H, s, OCH3); 7.15 (2H, d, J = 7.8,
3
3
1
H Ar); 7.25 (2H, d, J = 7.8, H Ar); 7.52 (1H, d, J = 7.6,
Rf 0.65. H NMR spectrum, δ, ppm (J, Hz): 1.56 (3H, s,
3
3
H Ar); 7.63 (1H, t, J = 7.6, H Ar); 7.72 (1H, d, J = 7.6,
4a-CH3); 2.35 (3H, s, 1-CH3); 3.12 (3H, s, NCH3); 3.75 (3H,
3
3
H Ar); 7.85 (1H, t, J = 7.6, H Ar). 13C NMR spectrum,
s, CO2CH3); 3.83 (3H, s, CO2CH3); 7.54 (1H, t, J = 7.6,
3
3
δ, ppm: 14.6 (CH3); 31.4 (CH3); 46.7 (CH2); 55.6 (OCH3);
108.7 (C); 113.2 (2C Ar); 120.7 (C Ar); 124.5 (C Ar);
125.2 (C); 128.6 (C Ar); 131.2 (C); 132.4 (C); 133.4
(2C Ar); 135.2 (C Ar); 143.3 (C); 147.2 (C); 148.3 (C);
158.6 (C); 187.6 (C=O); 193.5 (C=O). Mass spectrum, m/z
(Irel, %): 345 [M]+ (10), 302 [M–C2H3O]+ (56), 91 [C7H7]+
(86), 43 [CH3C≡O]+ (100). Found, %: C 76.63; H 5.65;
N 4.22. C22H19NO3. Calculated, %: C 76.50; H 5.54; N 4.06.
Ethyl 2-methyl-4-oxo-1-propyl-1,4-dihydroindeno-
[1,2-b]pyrrole-3-carboxylate (1f). Yield 517 mg (87%),
yellow powder, mp 145–147°C. IR spectrum, ν, cm–1:
1745, 1728, 1725, 1685, 1574, 1468, 1376. Rf 0.32.
H Ar); 7.64 (1H, t, J = 7.5, H Ar); 7.78 (1H, d, J = 7.6,
H Ar); 7.92 (1H, d, J = 7.6, H Ar). 13C NMR spectrum,
3
δ, ppm: 13.5 (CH3); 18.2 (CH3); 34.2 (CH3); 51.2
(CO2CH3); 52.4 (CO2CH3); 71.2 (C); 105.3 (C); 115.2 (C);
116.4 (C); 121.6 (C Ar); 124.3 (C Ar); 127.2 (C Ar); 131.2
(C); 133.4 (C Ar); 138.6 (C); 141.6 (C); 144.7 (C); 154.2
(C); 161.3 (C=O); 165.3 (C=O); 188.4 (C=O). Mass spectrum,
m/z (Irel, %): 381 [M]+ (10), 350 [M–CH3O]+ (68), 31
[CH3O]+ (100). Found, %: C 66.28; H 5.16; N 3.78.
C21H19NO6. Calculated, %: C 66.14; H 5.02; N 3.67.
Dimethyl 5-ethyl-1,4a-dimethyl-10-oxo-4a,5-dihydro-
10H-indeno[1,2-b]pyrano[3,4-d]pyrrole-3,4-dicarboxy-
late (9b). Yield 0.63 g (80%), pale-yellow powder, mp 183–
185°C. IR spectrum, ν, cm–1: 1745, 1729, 1698, 1586,
3
1H NMR spectrum, δ, ppm (J, Hz): 1.12 (3H, t, J = 7.4,
3
N(CH2)2CH3); 1.38 (3H, t, J = 7.4, CO2CH2CH3); 1.65–
1
1.73 (2H, m, NCH2CH2CH3); 2.92 (3H, s, 2-CH3); 4.26
1478, 1373. Rf 0.43. H NMR spectrum, δ, ppm (J, Hz):
3
3
3
(2H, q, J = 7.4, CO2CH2CH3); 4.93 (2H, t, J = 7.3,
1.15 (3H, t, J = 7.4, NCH2CH3); 1.56 (3H, s, 4a-CH3);
3
NCH2CH2CH3); 7.56 (1H, d, J = 7.6, H Ar); 7.64 (1H, d,
2.37 (3H, s, 1-CH3); 3.75 (3H, s, CO2CH3); 3.87 (3H, s,
CO2CH3); 4.25–4.38 (2H, m, NCH2CH3); 7.56 (1H, t,
3J = 7.5, H Ar); 7.73 (1H, t, J = 7.6, H Ar); 7.82 (1H, t,
3
3
3J = 7.6, H Ar). 13C NMR spectrum, δ, ppm: 11.3 (CH3);
14.2 (CH3); 15.6 (CH3); 26.3 (CH2); 52.4 (CH2); 61.3
(CO2CH2); 101.2 (C); 109.4 (C); 121.4 (C Ar); 124.6
(C Ar); 127.2 (C Ar); 131.2 (C); 133.6 (C Ar); 142.2 (C);
146.4 (C); 149.2 (C); 167.3 (C=O); 188.3 (C=O). Mass
spectrum, m/z (Irel, %): 297 [M]+ (10), 252 [M–C2H5O]+
(86), 45 [C2H5O]+ (100). Found, %: C 72.83; H 6.58;
N 4.82. C18H19NO3. Calculated, %: C 72.71; H 6.44; N 4.71.
Ethyl 1-(4-methoxyphenyl)-2-methyl-4-oxo-1,4-dihydro-
indeno[1,2-b]pyrrole-3-carboxylate (1g). Yield 578 mg
(80%), yellow powder, mp 168–170°C. IR spectrum, ν, cm–1:
3J = 7.8, H Ar); 7.68 (1H, t, J = 7.8, H Ar); 7.82 (1H, d,
3
3J = 7.7, H Ar); 7.95 (1H, d, J = 7.8, H Ar). 13C NMR
spectrum, δ, ppm: 13.4 (CH3); 13.8 (CH3); 19.2 (CH3); 43.2
(CH2); 51.4 (CO2CH3); 52.6 (CO2CH3); 68.2 (C); 105.4
(C); 115.6 (C); 117.2 (C); 121.2 (C Ar); 124.5 (C Ar);
127.6 (C Ar); 130.8 (C); 133.2 (C Ar); 137.2 (C); 142.3
(C); 144.5 (C); 154.3 (C); 162.4 (C=O); 166.7 (C=O);
188.5 (C=O). Mass spectrum, m/z (Irel, %): 395 [M]+ (15),
364 [M–CH3O]+ (78), 31 [C2H5O]+ (100). Found, %:
C 66.94; H 5.47; N 3.67. C22H21NO6. Calculated, %:
C 66.83; H 5.35; N 3.54.
1
1747, 1725, 1697, 1578, 1464, 1386. Rf 0.27. H NMR
Diethyl 1,4a-dimethyl-10-oxo-5-phenyl-4a,5-dihydro-
10H-indeno[1,2-b]pyrano[3,4-d]pyrrole-3,4-dicarboxylate
(9c). Yield 0.71 g (75%), pale-yellow powder, mp 196–
198°C. IR spectrum, ν, cm–1: 1746, 1728, 1694, 1587, 1476,
1375. Rf 0.37. 1H NMR spectrum, δ, ppm (J, Hz): 1.14 (3H,
t, 3J = 7.4, CO2CH2CH3); 1.18 (3H, t, 3J = 7.4, CO2CH2CH3);
1.68 (3H, s, 4a-CH3); 2.38 (3H, s, 1-CH3); 4.23 (2H, q,
spectrum, δ, ppm (J, Hz): 1.35 (3H, t, 3J = 7.4, CO2CH2CH3);
2.83 (3H,s, 2-CH3); 3.85 (3H, s, OCH3); 4.26 (2H, q, 3J = 7.4,
3
CO2CH2CH3); 6.95 (2H, d, J = 7.6, H Ar); 7.06 (1H, d,
3
3J = 7.6, H Ar); 7.22 (2H, d, J = 7.6, H Ar); 7.52 (1H, t,
3
3J = 7.6, H Ar); 7.63 (1H, d, J = 7.6, H Ar); 7.75 (1H, t,
3J = 7.6, H Ar). 13C NMR spectrum, δ, ppm: 14.2 (CH3);
15.6 (CH3); 55.6 (OCH3); 61.7 (CO2CH2); 106.6 (C); 113.7
(2C Ar); 116.3 (C); 120.5 (C Ar); 125.3 (2C Ar); 125.8
(C Ar); 127.6 (C Ar); 131.3 (C); 134.5 (C Ar); 139.2 (C);
141.2 (C); 144.3 (C); 147.6 (C); 158.6 (C); 164.3 (C=O);
187.6 (C=O). Mass spectrum, m/z (Irel, %): 361 [M]+ (10),
316 [M–C2H5O]+ (68), 45 [C2H5O]+ (100). Found, %:
C 73.26; H 5.42; N 3.96. C22H19NO4. Calculated, %:
C 73.12; H 5.30; N 3.88.
3
3J = 7.4, CO23CH2CH3); 4.34 (2H, q, J = 7.4, CO2CH2CH3);
3
7.06 (2H, d, J = 7.6, H Ar); 7.12 (1H, t, J = 7.6, H Ar);
3
3
7.34 (2H, t, J = 7.6, H Ar); 7.63 (1H, t, J = 7.8, H Ar);
3
3
7.72 (1H, t, J = 7.8, H Ar); 7.85 (1H, d, J = 7.5, H Ar);
3
7.93 (1H, d, J = 7.8, H Ar). 13C NMR spectrum, δ, ppm:
13.2 (CH3); 13.6 (CH3); 14.3 (CH3); 19.4 (CH3); 61.2
(CH2); 62.4 (CH2); 68.6 (C); 109.2 (C); 114.3 (C); 115.6
(C); 121.3 (C Ar); 124.2 (C Ar); 124.8 (C Ar); 126.3
(2C Ar); 127.2 (C Ar); 128.6 (2C Ar); 130.6 (C); 133.4
(C Ar); 138.4 (C); 141.5 (C); 143.4 (C); 145.2 (C); 153.4
Synthesis of indeno[1,2-b]pyrano[3,4-d]pyrroles 9a–c
(General method). Dialkyl acetylenedicarboxylate 10a,b
1043

Chemistry of Heterocyclic Compounds 2018, 54(11), 1040–1044
Adv. Mater. 2008, 20, 2556. (d) Hagfeldt, A.; Boschloo, G.;
(C); 163.6 (C=O); 167.2 (C=O); 187.6 (C=O). Mass
spectrum, m/z (Irel, %): 471 [M]+ (10), 426 [M–C2H5O]+
(62), 45 [C2H5O]+ (100). Found, %: C 71.45; H 5.47;
N 3.14. C28H25NO6. Calculated, %: C 71.33; H 5.34; N 2.97.
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The authors are grateful to the Islamic Azad University
of Qaemshahr for financial support.
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