A novel and facile approach for synthesis of 5-amino-7-aryl-6-cyano-4H- pyrano[3,2-b]pyrroles

Article abstract of DOI:10.1007/s12039-012-0262-0

An efficient and iron-catalysed synthesis of 4H-pyrano[3,2-b]pyrrole is reported. The reactions proceed through a one-pot, three component cyclocondensation of 3-hydroxypyrrole, malononitrile and various aldehydes to afford 4H-pyrano[3,2-b]pyrrole derivatives in moderate to good yield using ferric hydrogensulphate, Fe(HSO₄)₃, as the catalyst.

Full text of DOI:10.1007/s12039-012-0262-0

c
J. Chem. Sci. Vol. 124, No. 4, July 2012, pp. 893–899. ꢀ Indian Academy of Sciences.
A novel and facile approach for synthesis
of 5-amino-7-aryl-6-cyano-4H-pyrano[3,2-b]pyrroles
REZA SANDAROOS1,∗ and SAMAN DAMAVANDI2,∗
1Department of Chemistry, Faculty of Science, University of Birjand, Birjand, Iran
2Department of Chemistry, Sarvestan Branch, Islamic Azad University, Sarvestan, Iran
e-mail: R_Sandaroos@yahoo.com; Saman_Damavandi@yahoo.com
MS received 31 August 2011; revised 25 December 2012; accepted 16 January 2012
Abstract. An efficient and iron-catalysed synthesis of 4H-pyrano[3,2-b]pyrrole is reported. The reac-
tions proceed through a one-pot, three component cyclocondensation of 3-hydroxypyrrole, malononitrile
and various aldehydes to afford 4H-pyrano[3,2-b]pyrrole derivatives in moderate to good yield using ferric
hydrogensulphate, Fe(HSO4)3, as the catalyst.
Keywords. Pyranopyrrole; one-pot; catalyst.
1. Introduction
Many efforts have recently been undertaken by the
preparation of various pyran derivatives with the aim
of obtaining more biologically potent heterocyclic sys-
tems.17–22 However, to the best of our knowledge,
synthesis of 5-amino-7-aryl-6-cyano-4H-pyrano[3,2-
b]pyrrole derivatives has never been communicated up
to now. In this study, in continuation of our interest in
MCRs,23,24 the one-pot synthesis of 5-amino-7-aryl-6-
cyano-4H-pyrano[3,2-b]pyrroles by cyclocondensation
reaction of 3-hydroxypyrrole, substituted benzaldehy-
des and malononitrile in the presence of ferric hydro-
gensulphate, Fe(HSO4)3, is described here (figure 1).
In the realm of organic synthesis, it would be desir-
able to perform a series of simple steps in one pot,1,2
which would minimize the chemicals used and waste
produced, as well as the reaction time consumed. As
a result, great attention has been paid to the deve-
lopment of cascade reactions. Multicomponent reac-
tions (MCRs) involving a cascade process with at least
three different substrates to generate complex mole-
cular frameworks have emerged as a powerful syn-
thetic strategy.3,4 Because the combination of three
components to generate new products in a single step
is extremely economical, among the multi-component
reactions.5
It is well-known that pyrans are important core units
in a number of natural products6,7 and photochromic
materials.8 Compounds with pyran ring system have
many pharmacological properties and play important
roles in biochemical process.9 Therefore, preparation of
this heterocyclic nucleus has gained more importance
in organic synthesis.
The 4H-pyran derivatives are of the immense inte-
rests in the area of synthesizing various drugs due to
their pharmacological and biological activities, such as
antimicrobial,10 mutagenicity,11,12 antiproliferative,13
sex pheromone,14 antitumour15 and central nervous sys-
tem activity.16 Therefore, the synthesis of such com-
pounds is an interesting challenge.
2. Experimental
2.1 General
All chemicals were purchased from Merck, Fluka and
Aldrich Chemical Companies. All yields refer to iso-
lated products. The products were characterized by their
spectral data. IR spectra were recorded on a Shimadzu-
IR 470 spectrophotometer. H NMR, 13CNMR and
1
DEPT 13CNMR spectra were recorded on a Bruker
100-MHz spectrometer in chloroform as the solvent
and TMS as internal standard. Elemental analysis (C,
H, N%) was carried out by Perkin-Elmer 2400 series-
II elemental analyzer. Flash column chromatography
was performed with 300 and 400 meshes silica gel
and analytical thin-layer chromatography (TLC) was
performed on pre-coated silica gel plates (60F-254).
∗For correspondence
893

894
Reza Sandaroos and Saman Damavandi
OH
O
NH2
O
Fe(HSO4)3 10 mol%
CH3CN, Reflux
CN
CN
+
+
H
Ar
N
N
H
N
H
Ar
Figure 1. One-pot synthesis of pyranopyrroles.
2.2 General procedure for synthesis of pyranopyrrole (pyran C5), 122.8, 129.1, 127.9, 130.8 (Ar-C), 173.7
derivatives 5a–l
(pyran C2).
A mixture of aldehyde (1 mmol), 3-hydroxypyrrole
(1 mmol), malononitrile (1.1 mmol) and ionic liquid
catalyst (0.1 mmol) in CH3CN (4 mml) was stirred at
50◦C for the appropriate time. The reaction was moni-
tored by TLC and after completion of the reaction; the
catalyst was simply recovered by filtration and washed
by dichloromethane. The residue was concentrated in
vacuo and the crude product was purified by column
chromatography on silica gel.
2.2c 5-Amino-1,7-dihydro-7-p-tolylpyrano[3,2-b]
pyrrole-6-carbonitrile (5c): Anal Calcd. for
C15H13N3O (251.28): C, 71.70; H, 5.21; N, 16.72%.
Found: C, 70.93; H, 5.08; N, 16.14%. IR (KBr, νmax
,
cm−1): 3422 and 3272 (asym. and sym. str. of -NH2),
3419 (NH), 2189 (-CN str.), 1252 (asym. str. of cyclic
1
ArC-O-C ether). H NMR (400 MHz, CDCl3) δH
(ppm): 2.31 (s, 3H, Ar-CH3), 5.60 (s, 1H, pyran H4),
6.18 (d, 1H, pyrrole H3), 6.80 (s, 2H, D2O exch., NH2),
6.89 (d, 1H, pyrrole H2), 6.98–7.07 (m, 4H, Ar-H),
7.38 (s, 1H, pyrrole NH). 13C NMR (250 MHz, CDCl3)
δC (ppm): 24.7 (-CH3), 29.21 (pyran C4, CH), 54.6
(pyran C3), 100.1 (pyran C6), 107.3 (pyrrole C3, CH),
115.7 (pyrrole C1, CH), 126.5 (CN), 131.4 (pyran C5),
128.3, 129.1, 133.6, 137.9 (Ar-C), 169.1 (pyran C2).
2.2a 5-Amino-1,7-dihydro-7-(4-methoxyphenyl)pyrano
[3,2-b]pyrrole-6-carbonitrile (5a): Anal Calcd. for
C15H13N3O2 (267.28): C, 67.40; H, 4.90; N, 15.72%.
Found: C, 66.22; H, 4.78; N, 15.59%. IR (KBr, νmax
,
cm−1): 3411 and 3279 (asym. and sym. str. of -NH2),
3400 (NH), 2160 (-CN str.), 1251 (asym. str. of cyclic
1
ArC-O-C ether). H NMR (400 MHz, CDCl3) δH
2.2d 5-Amino-7-(4-bromophenyl)-1,7-dihydropyrano
[3,2-b]pyrrole-6-carbonitrile (5d): Anal Calcd. for
C14H10BrN3O (316.15): C, 53.19; H, 3.19; N, 13.29%.
Found: C, 52.79; H, 3.14; N, 12.64%. IR (KBr, ν,
cm−1): 3425 and 3269 (asym. and sym. str. of -NH2),
3434 (NH), 2201 (-CN str.), 1242 (asym. str. of cyclic
(ppm): 3.37 (s, 3H, OCH3), 5.43 (s, 1H, pyran H4), 6.11
(d, 1H, pyrrole H3), 6.63 (d, 2H, Ar-H), 6.68 (d, 1H,
pyrrole H2), 6.89 (s, 2H, D2O exch., NH2), 7.05 (d, 2H,
Ar-H), 7.54 (s, 1H, pyrrole NH). 13C NMR (250 MHz,
CDCl3) δC (ppm): 28.6 (pyran C4, CH, CH), 55.23 (O-
CH3, CH3), 59.5 (pyran C3), 101.5 (pyran C6), 104.9
(pyrrole C3, CH), 119.3 (pyrrole, C1, CH), 122.0 (CN),
126.1 (pyran C5), 119.2, 127.4, 130.3, 154.6 (Ar-C),
171.4 (pyran C2).
1
ArC-O-C ether). H NMR (400 MHz, CDCl3) δH
(ppm): 5.40 (s, 1H, pyran H4), 6.11 (d, 1H, pyrrole H3),
6.49 (s, 2H, D2O exch., NH2), 7.06 (d, 2H, Ar-H), 6.70
(d, 1H, pyrrole H2), 7.25 (d, 2H, Ar-H), 7.39 (s, 1H,
pyrrole NH). 13C NMR (250 MHz, CDCl3) δC (ppm):
31.4 (pyran C4, CH), 64.9 (pyran C3), 100.5 (pyran
C6), 109.5 (pyrrole C3, CH), 117.3 (pyrrole, C1, CH),
127.2 (CN), 130.3 (pyran C5), 123.6, 129.4, 130.9,
138.4 (Ar-C), 179.7 (pyran C2).
2.2b 5-Amino-1,7-dihydro-7-phenylpyrano[3,2-b]
pyrrole-6-carbonitrile (5b): Anal Calcd. for
C14H11N3O (237.26): C, 70.87; H, 4.67; N, 17.71%.
Found: C, 68.59; H, 4.62; N, 16.97%. IR (KBr, νmax
,
cm−1): 3405 and 3283 (asym. and sym. str. of -NH2),
3405 (NH), 2157 (-CN str.), 1247 (asym. str. of cyclic 2.2e 5-Amino-7-(2-bromophenyl)-1,7-dihydropyrano
1
ArC-O-C ether). H NMR (400 MHz, CDCl3) δH [3,2-b]pyrrole-6-carbonitrile (5e): Anal Calcd. for
(ppm): 5.51 (s, 1H, pyran H4), 6.25 (d, 1H, pyrrole H3), C14H10BrN3O (316.15): C, 53.19; H, 3.19; N, 13.29%.
6.73 (d, 1H, pyrrole H2), 6.75 (s, 2H, D2O exch., NH2), Found: C, 51.98; H, 3.16; N, 13.14%. IR (KBr, νmax
,
7.09–7.15 (m, 5H, Ar-H), 7.50 (s, 1H, pyrrole NH). 13C cm−1): 3415 and 3298 (asym. and sym. str. of -NH2),
NMR (250 MHz, CDCl3) δC (ppm): 30.6 (pyran C4, 3411 (NH), 2187 (-CN str.), 1257 (asym. str. of cyclic
1
CH), 55.8 (pyran C3), 101.6 (pyran C6), 106.4 (pyrrole ArC-O-C ether). H NMR (400 MHz, CDCl3) δH
C3, CH), 117.9 (pyrrole, C1, CH), 123.5 (CN), 129.7 (ppm): 5.58 (s, 1H, pyran H4), 6.19 (d, 1H, pyrrole H3),

One-pot preparation of 4H-pyrano[3,2-b]pyrrole derivaties
895
6.73 (d, 1H, pyrrole H2), 6.79 (s, 2H, D2O exch., NH2), (250 MHz, CDCl3) δC (ppm): 34.6 (pyran C4, CH),
6.97–7.11 (m, 4H, Ar-H), 7.58 (s, 1H, pyrrole NH). 13C 62.78 (pyran C3), 111.7 (pyran C6), 114.5 (pyrrole C3,
NMR (250 MHz, CDCl3) δC (ppm): 28.3 (pyran C4, CH), 122.4 (pyrrole, C1, CH), 124.8 (CN), 126.5 (CN),
CH), 57.5 (pyran C3), 108.6 (pyran C6), 108.9 (pyrrole 139.4 (pyran C5), 114.8, 129.9, 133.5, 139.5 (Ar-C),
C3, CH), 121.6 (pyrrole, C1, CH), 127.5 (CN), 131.5 176.3 (pyran C2).
(pyran C5), 122.8, 122.4, 128.9, 132.7, 133.0, 141.6
(Ar-C), 179.0 (pyran C2).
2.2i 5-Amino-7-(2-cyanophenyl)-1,7-dihydropyrano
[3,2-b]pyrrole-6-carbonitrile (5i): Anal Calcd. for
2.2f 5-Amino-7-(4-chlorophenyl)-1,7-dihydropyrano C15H10N4O (262.09): C, 68.69; H, 3.84; N, 21.36%.
[3,2-b]pyrrole-6-carbonitrile (5f): Anal Calcd. for Found: C, 68.34; H, 3.23; N, 21.20%. IR (KBr,
C14H10ClN3O (271.7): C, 61.89; H, 3.71; N, 15.47%. νmax, cm−1): 3421 and 3248 (asym. and sym. str. of
Found: C, 61.34; H, 3.69; N, 15.43%. IR (KBr, νmax
,
-NH2), 3416 (NH), 2201 (-CN str.), 2190 (-CN str.),
1
cm−1): 3414 and 3259 (asym. and sym. str. of -NH2), 1250 (asym. str. of cyclic ArC-O-C ether). H NMR
3415 (NH), 2156 (-CN str.), 1256 (asym. str. of cyclic (400 MHz, CDCl3) δH (ppm): 5.59 (s, 1H, pyran H4),
1
ArC-O-C ether). H NMR (400 MHz, CDCl3) δH 6.31 (d, 1H, pyrrole H3), 6.60 (d, 1H, pyrrole H2), 6.81
(ppm): 5.48 (s, 1H, pyran H4), 6.16 (d, 1H, pyrrole H3), (s, 2H, D2O exch., NH2), 7.23–7.39 (m, 4H, Ar-H),
6.42 (s, 2H, D2O exch., NH2), 6.64 (d, 1H, pyrrole H2), 7.43 (s, 1H, pyrrole NH). 13C NMR (250 MHz, CDCl3)
7.06 (d, 2H, Ar-H), 7.21 (d, 2H, Ar-H), 7.29 (s, 1H, δC (ppm): 29.2 (pyran C4, CH), 59.6 (pyran C3), 110.3
pyrrole NH). 13C NMR (250 MHz, CDCl3) δC (ppm): (pyran C6), 110.9 (pyrrole C3, CH), 118.1 (pyrrole,
30.7 (pyran C4, CH), 60.23 (pyran C3), 106.5 (pyran C1, CH), 120.3 (CN), 121.5 (CN), 134.2 (pyran C5),
C6), 108.4 (pyrrole C3, CH), 119.0 (pyrrole, C1, CH), 115.0, 128.2, 130.6, 132.5, 133.9, 141.3 (Ar-C), 174.8
124.8 (CN), 136.1 (pyran C5), 129.5, 129.4, 130.5, (pyran C2).
132.8 (Ar-C), 179.7 (pyran C2).
2.2j 5-Amino-1,7-dihydro-7-(4-nitrophenyl)pyrano[3,
2-b]pyrrole-6-carbonitrile (5j): Anal Calcd. for
C14H10N4O3 (282.25): C, 59.57; H, 3.57; N, 19.85%.
2.2g 5-Amino-7-(2-chlorophenyl)-1,7-dihydropyrano
[3,2-b]pyrrole-6-carbonitrile (5g): Anal Calcd. for
C14H10ClN3O (271.7): C, 61.89; H, 3.71; N, 15.47%.
Found: C, 59.21; H, 3.52; N, 19.66%. IR (KBr, νmax
,
cm−1): 3413 and 3240 (asym. and sym. str. of -NH2),
3414 (NH), 2178 (-CN str.), 1360 and 1548 (asym. and
sym. str. of -NO2), 1249 (asym. str. of cyclic ArC-O-C
ether). 1H NMR (400 MHz, CDCl3) δH (ppm): 5.50 (s,
1H, pyran H4), 6.17 (d, 1H, pyrrole H3), 6.40 (s, 2H,
D2O exch., NH2), 6.57 (d, 1H, pyrrole H2), 7.31 (s, 1H,
pyrrole NH), 7.37 (d, 2H, Ar-H), 8.03 (d, 2H, Ar-H),.
13C NMR (250 MHz, CDCl3) δC (ppm): 30.4 (pyran
C4, CH), 59.70 (pyran C3), 107.8 (pyran C6), 108.2
(pyrrole C3, CH), 120.5 (pyrrole, C1, CH), 124.3 (CN),
136.8 (pyran C5), 121.5, 129.1, 141.6, 145.3 (Ar-C),
177.4 (pyran C2).
Found: C, 61.23; H, 3.66; N, 15.18%. IR (KBr, νmax
,
cm−1): 3458 and 3256 (asym. and sym. str. of -NH2),
3397 (NH), 2167 (-CN str.), 1248 (asym. str. of cyclic
1
ArC-O-C ether). H NMR (400 MHz, CDCl3) δH
(ppm): 5.51 (s, 1H, pyran H4), 6.28 (d, 1H, pyrrole H3),
6.64 (d, 1H, pyrrole H2), 6.84 (s, 2H, D2O exch., NH2),
7.09–7.19 (m, 4H, Ar-H), 7.43 (s, 1H, pyrrole NH). 13C
NMR (250 MHz, CDCl3) δC (ppm): 26.2 (pyran C4,
CH), 55.6 (pyran C3), 113.9 (pyran C6), 114.2 (pyrrole
C3, CH), 118.6 (pyrrole, C1, CH), 129.1 (CN), 137.2
(pyran C5), 125.4, 127.3, 128.9, 132.7, 133.0, 139.6
(Ar-C), 173.7 (pyran C2).
2.2k 5-Amino-1,7-dihydro-7-(2-nitrophenyl)pyrano[3,
2-b]pyrrole-6-carbonitrile (5k): Anal Calcd. for
C14H10N4O3 (282.2): C, 59.57; H, 3.57; N, 19.85%.
2.2h 5-Amino-7-(4-cyanophenyl)-1,7-dihydropyrano
[3,2-b]pyrrole-6-carbonitrile (5h): Anal Calcd. for
C15H10N4O (262.09): C, 68.69; H, 3.84; N, 21.36%.
Found: C, 67.84; H, 3.75; N, 20.90%. IR (KBr,
νmax, cm−1): 3401 and 3248 (asym. and sym. str. of
-NH2), 3418 (NH), 2210 (-CN str.), 2181 (-CN str.),
Found: C, 59.03; H, 3.48; N, 19.57%. IR (KBr, νmax
,
cm−1): 3410 and 3195 (asym. and sym. str. of -NH2),
3365 (NH), 2167 (-CN str.), 1381 and 1547 (asym.
and sym. str. of -NO2), 1253 (asym. str. of cyclic ArC-
1
1257 (asym. str. of cyclic ArC-O-C ether). H NMR
1
O-C ether). H NMR (400 MHz, CDCl3) δH (ppm):
(400 MHz, CDCl3) δH (ppm): 5.51 (s, 1H, pyran H4),
6.10 (d, 1H, pyrrole H3), 6.48 (s, 2H, D2O exch.,
NH2), 6.60 (d, 1H, pyrrole H2), 7.24 (s, 1H, pyrrole
NH), 7.26 (d, 2H, Ar-H), 7.38 (d, 2H, Ar-H). 13C NMR
5.51 (s, 1H, pyran H4), 6.28 (d, 1H, pyrrole H3), 6.48
(d, 1H, pyrrole H2), 6.86 (s, 2H, D2O exch., NH2),
7.33–7.39 (m, 2H, Ar-H), 7.44 (s, 1H, pyrrole NH),

896
Reza Sandaroos and Saman Damavandi
Table 1. Effect of solvents on the synthesis of pyrano[3,2-b]pyrrole derivatives.a
Entry
Solvent
Time (h)
Yield (%)b
1
2
3
4
5
Benzene
CH3CN
MeOH
EtOH
8
6
7
7
5
40
86
30
38
63
Toluene
aReaction conditions: 1.0 equiv. of 3-hydroxypyrrole, 1.0 equiv. of benzaldehyde, 1.1
equiv. of malonoitrile, 10 mol% of Fe(HSO4)3, 4 mL of CH3CN and at reflux condition.
bIsolated yields
7.56 (dd, 1H, Ar-H), 8.01 (d, 1H, Ar-H). 13C NMR C3, CH), 121.2 (pyrrole, C1, CH), 121.9 (CN), 137.7
(250 MHz, CDCl3) δC (ppm): 26.0 (pyran C4, CH), (pyran C5), 122.0, 128.4, 133.5, 134.9, 136.0, 148.8
54.3 (pyran C3), 110.9 (pyran C6), 112.2 (pyrrole (Ar-C), 177.0 (pyran C2).
O
O
S
O
Fe
CN
CN
CN
CN
Fe(HSO4)3
H
O
3
Ar
O
Ar
H
Fe(HSO4)3
Ar
HN
O
HN
Step 1
H
Step 2
O
O
HN
intermediate A
OH
(2a-k)
(1a-k)
Step 3
Ar
Ar
Ar
H
CN
C
CN
NH
CN
HN
Step 5 HN
Step 4
O
S
HN
NH2
N
OH
Fe
O
O
O
O
3
O
H
(3a-k)
(4a-k)
(5a-k)
Compnd
Ar
a
b
c
d
e
f
g
h
i
4-OMe-C6H4
C6H6
4-Me-C6H4
4-Br-C6H4
2-Br-C6H4
4-Cl-C6H4
2-Cl-C6H4
4-CN-C6H4
2-CN-C6H4
4-NO2-C6H4
2-NO2-C6H4
2-Furyl
j
k
l
Figure 2. Proposed mechanism for one-pot, three-component synthesis of pyrano[3,2-
b]pyrrole derivatives catalysed by [pmim] HSO4 SiO2
.

One-pot preparation of 4H-pyrano[3,2-b]pyrrole derivaties
897
Table 2. One-pot, three-component synthesis of 5-amino-7-aryl-6-cyano-4H-
pyrano[3,2-b]pyrroles.a
Entry
Aldehyde
Productb
Time (h)
Yield (%)c
O
NH2
OMe
N
H
N
1
7
73
O
O
O
NH2
N
H
2
3
6
6
86
82
N
O
O
NH2
N
H
N
O
O
NH2
Br
N
H
N
4
5
5
6
84
80
O
Br
O
NH2
N
H
Br
O
N
Br
O
NH2
Cl
N
H
N
6
7
5
5
87
80
O
Cl
O
NH2
N
H
Cl
O
N
Cl

898
Reza Sandaroos and Saman Damavandi
Table 2. (continued).
Entry
Aldehyde
Productb
Time (h)
Yield (%)c
O
NH2
CN
N
H
N
8
6
68
O
CN
O
NH2
N
H
9
6.5
65
75
CN
O
N
CN
O
NH2
NO2
N
H
N
10
7
O
NO2
O
NH2
N
H
11
12
8
8
70
55
NO2
O
N
NO2
O
NH2
N
O
O
N
H
O
aReaction conditions: 1.0 equiv. of 3-hydroxypyrrole, 1.0 equiv. of aldehyde, 1.0 equiv.
of malonoitrile, 10 mol% of Fe(HSO4)3, 4 mL of CH3CN as solvent and at 50◦C.
bThe products were identified by 1HNMR, 13C NMR and EA analysis.
cIsolated yields
2.2l 5-Amino-7-(furan-2-yl)-1,7-dihydropyrano[3,2-
6.19 (m, 2H, pyrrole H3 and furan H4), 6.59 (d, 1H,
b]pyrrole-6-carbonitrile (5l): Anal Calcd. for pyrrole H2), 6.78 (s, 2H, D2O exch., NH2), 7.24 (d, 1H,
C12H9N3O2 (227.22 gr/mole): C, 63.43; H, 3.99; N, furan H2), 7.40 (s, 1H, pyrrole NH). 13C NMR (250 MHz,
18.49%. Found: C, 63.04; H, 3.86; N, 18.34%. IR CDCl3) δC (ppm): 29.4 (pyran C4, CH), 56.4 (pyran
(KBr, ν, cm−1): 3418 and 3234 (asym. and sym. str. of C3), 106.9 (pyran C6), 107.0 (furan C3), 110.3 (pyrrole
-NH2), 3419 (NH), 2166(-CN str.), 1252 (asym. str. of C3, CH), 110.8 (furan C4, CH), 119.5 (pyrrole, C1,
cyclic ArC-O-C ether). 1H NMR (400 MHz, CDCl3) δH CH), 116.4 (CN), 141.9 (furan C2, CH), 143.2 (pyran
(ppm): 5.47 (s, 1H, pyran H4), 5.87 (dd, 1H, furan H3), C5), 150.9 (furan C1, CH), 167.4 (pyran C2).

One-pot preparation of 4H-pyrano[3,2-b]pyrrole derivaties
899
3. Results and discussions
4. Conclusion
A mixture of benzaldehyde, 3-hydroxypyrrole and malo- A novel and effective approach for the synthesis of
nonitrile with stoichiometic ratio of 1.0:1.0:1.1 and substituted pyrano[3,2-b]indole-3-carbonitrile deriva-
10% mol of ferric hydrogensulphate was chosen as the tives by one-pot, three-component reactions of 3-
model reaction to check the feasibility of this synthe- hydroxyindole, aromatic aldehydes and malononitrile
sis. The reaction was carried out in CH3CN at reflux in the presence of ferric hydrogensulphate was reported.
condition. The corresponding pyrano[3,2-b]pyrrole was
obtained in good yield. Encouraged by the results, to
References
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