Efficient one-pot synthesis of 2-amino-4H-chromenes catalyzed by ferric hydrogen sulfate and Zr-based catalysts of FI

Article abstract of DOI:10.1080/15533174.2011.591347

Fe(HSO₄)₃ efficiently catalyzes the synthesis of 2-amino-4Hchromenes. The reactions proceed through a one-pot, threecomponent condensation of α- or β-naphthol, aromatic aldehyde derivatives, and malonitrile in the presence of a catal

Full text of DOI:10.1080/15533174.2011.591347

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Efficient One-Pot Synthesis of 2-Amino-4H-
chromenes Catalyzed by Ferric Hydrogen Sulfate and
Zr-Based Catalysts of FI
H. Eshghi a , S. Damavandi a & G. H. Zohuri a
a Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad,
Mashhad, I. R. Iran
Version of record first published: 07 Nov 2011
To cite this article: H. Eshghi, S. Damavandi & G. H. Zohuri (2011): Efficient One-Pot Synthesis of 2-Amino-4H-chromenes
Catalyzed by Ferric Hydrogen Sulfate and Zr-Based Catalysts of FI, Synthesis and Reactivity in Inorganic, Metal-Organic,
and Nano-Metal Chemistry, 41:9, 1067-1073
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:1067–1073, 2011
Copyright ꢀ Taylor & Francis Group, LLC
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ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.591347
Efficient One-Pot Synthesis of 2-Amino-4H-chromenes
Catalyzed by Ferric Hydrogen Sulfate and Zr-Based
Catalysts of FI
H. Eshghi, S. Damavandi, and G. H. Zohuri
Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, I. R. Iran
as piperidine,[9] morpholine,[10] CTACl (cetyltrimethylam-
monium chloride),[11] TEBA (triethylbenzylammonium
chloride),[12] alumina,[13] methanesulfonic acid,[14] and
K2CO3 in water under microwave irradiation[15] have been
reported previously, most of them require long reaction
time as well as high temperatures. In spite of advent of the
recent efficient catalysts such as CAN (ceric ammonium ni-
trate),[16] N,N,dimethylaminoethylbenzyldimethylammonium
chloride,[17] Mg/Al hydrotalcite,[18] and CTABr (cetyltrimethy-
lammonium bromide),[19] which are claimed to be efficient in
synthesis 2-amino-4H-chromene compounds, these catalysts
are either expensive or not applicable to various compounds;
also, in some cases ultrasonic irradiation is needed to achieve
high yields. Therefore, the development of a new method with
better profitability, higher yield, and a simpler and convenient
procedure using an inexpensive catalyst is highly desirable.
In this work, we report the efficient synthesis of 2-amino-
4H-chromene derivatives through a one-pot, three-component
condensation of activated phenols, aromatic aldehydes, and mal-
ononitrile catalyzed by ferric hydrogen sulfate as an efficient,
bifunctional, heterogeneous, inexpensive, and easy-to-prepare
catalyst (Scheme 1). Additionally, to extend the scope and also
to introduce possible useful catalysts for this transformation,
three Zr-based FI catalyst swere applied to the one-pot synthe-
sis of chromene derivatives.
Fe(HSO4)3 efficiently catalyzes the synthesis of 2-amino-4H-
chromenes. The reactions proceed through a one-pot, three-
component condensation of α- or β-naphthol, aromatic aldehyde
derivatives, and malonitrile in the presence of a catalytic amount
of ferric hydrogen sulfate. Also, three-component condensation of
resorcinol, malononitrile, and various aldehydes using the catalyst
gave the corresponding 2-amino-4H-chromenes in good yields. The
catalyst displayed high activity and recyclability without loss of its
catalytic activity. Additionally, three Zr-based FI catalysts were ap-
plied for the one-pot synthesis of chromene derivatives. Although
the chemical yield was not high, it is the first report of using such
catalysts in the field.
Keywords amino-4H-chromenes, ferric hydrogen sulfate, three-
component condensation
INTRODUCTION
Multicomponent coupling reactions (MCRs) are emerging
as useful tools for the carbon–carbon and carbon–heteroatom
bond-forming reactions and for the synthesis of small drug-like
molecules with several degrees of structural diversity.[1] One-
pot multicomponent reactions provide the possibility of directly
synthesizing a complex molecule without needing to isolate the
intermediates, which has aroused researchers to design such re-
actions using different catalysts.[2,3] Benzopyrans have firmly
attracted the researchers’ attention due to their useful biological
and pharmacological properties.[3] The value of 2-amino-4H-
chromene compounds can be realized by their unique phar-
macological activities including antimicrobial,[4] antiviral,[5]
mutagenic,[3] antiproliferative,[6] antitumor,[7] cancer therapy,
and central nervous system activity.[8]
EXPERIMENTAL
Chemicals were either prepared or purchased from Merck,
Fluka, and Aldrich chemical companies. All yields refer
to isolated products. The products were characterized by
comparison of their physical data with those of known samples
or by their spectral data. Infrared (IR) spectra were recorded
Although several protocols for the synthesis of 2-
amino-4H-pyran derivatives using various catalysts such
1
on a Shimadzu-IR 470 spectrophotometer. H-Nuclear mag-
netic resonance (NMR) spectra was recorded on a Bruker
100-MHz spectrometer in chloroform as the solvent with
trimethylsilane (TMS) as internal standard. Ferric hydrogen
sulfate was prepared according to a previously reported
procedure.[20,21]
Received 16 March 2011; accepted 5 April 2011.
Address correspondence to Hossein Eshghi, Department of Chem-
istry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad
91775-1436, I. R. Iran. E-mail: heshghi@ferdowsi.um.ac.ir
1067

1068
H. ESHGHI ET AL.
δH (ppm): 3.50 (s, 3H), 5.40 (s, 1H), 6.75 (s, 2H, NH2),
7.0–7.50 (m, 10H).
CN
OH
Ar
NH2
(Entry 4): IR (KBr) (υmax, cm−1): 3430, 3116, 3045, 2965,
2194, 1709, 1551, 1460, 1375, 1273, 1097, 830, 750. δH
(ppm): 5.30 (s, 1H), 6.80–7.05 (m, 3H), 7.10–7.75 (m,
9H).
O
Fe(HSO4)3
OH
NH2
(Entry 5): IR (KBr) (υmax, cm−1): 3445, 3180, 2196, 1654, 1585,
1555, 1536, 1500, 1386, 1258, 1159, 1013, 805, 770. δH
(ppm): 5.25 (s, 1H), 7.10 (s, 2H, NH2), 7.60–7.80 (m,
3H), 7.90–8.15 (m, 5H).
CN
Ar
O
CN
CN
ArCHO +
+
(Entry 6): IR (KBr) (υmax, cm−1): 3456, 3166, 3091, 2171,
1585, 1572, 1548, 1493, 1372, 1233, 1145, 987, 875.
δH (ppm): 5.15 (s, 1H), 6.65 (s, 2H, NH2), 7.0–7.70 (m,
8H), 7.85 (d, 2H, J = 8 Hz).
Fe(HSO4)3
OH
HO
O
NH2
CN
(Entry 7): IR (KBr) (υmax, cm−1): 3444, 3305, 3192, 2738, 2194,
1617, 1537, 1317, 1258, 1086, 808; δH (ppm): 3.65 (s,
3H), 5.60 (s, 1H), 7.35 (m, 6H), 7.4–7.8 (m, 6H).
(Entry 9): IR (KBr) (υmax, cm−1): 3437, 3057, 3006, 2930, 2195,
1570, 1482, 1375, 1216, 1087, 866. δH (ppm): δH 4.85
(s, 1H), 6.40–7.40 (m, 10H), 9.9 (s, 1H, OH).
(Entry 10): IR (KBr) (υmax, cm−1): 3400, 3108, 2970, 2196,
1713, 1460, 1094, 1020, 736. δH (ppm): δH 4.80 (s, 1H),
6.90–7.10 (m, 2H, NH2), 7.30–7.50 (m, 4H), 7.55–7.95
(m, 3H), 9.75 (bs, 1H, OH).
OH
Ar
Fe(HSO4)3
SCH. 1. Ferric hydrogen sulfate-catalyzed three-component synthesis of 2-
amino-4H-chromenes.
General Procedure for Synthesis of 2-Amino-3-cyano-4-
substituted-4H-benzo[e]chromene Derivatives (1–8) and
2-Amino-3-cyano-7-hydroxy-4-substituted-4H-chromene
(9–12)
(Entry 11): IR (KBr) (υmax, cm−1): 3445, 3133, 2195, 1736,
1660, 1452, 1301, 1117, 958, 752. δH (ppm): δH 4.75 (s,
1H), 7–7.30 (m, 7H), 7.40–7.55 (m, 2H), 9.70 (s, 1H,
OH).
A reaction mixture of 2-naphthol (144 mg, 1.0 mmol),
benzaldehyde (106 mg, 1.0 mmol), malononitrile (61 µL,
1.1 mmol), and Fe(HSO4)3 (0.034 mg, 0.1 mmol) in MeCN
(10 mL) was refluxed for 4.5 h. Thin-layer chromatography
(TLC) showed completion of the reaction. The reaction mix-
ture was filtered to recover the catalyst. The catalyst was further
washed with an additional portion of MeCN (2 × 5 mL). The
combined filtrates were concentrated in vacuo to give Entry 1 as
an amorphous, off-white-colored solid (271 mg). NMR evalua-
tion of this solid shows the obianed compound is almost pure.
Crystallization of this solid from hot EtOH gives pure prod-
uct (256 mg, 86% yield) as colorless needles (melting point
[mp] 278◦C). The recovered Fe(HSO4)3 catalyst could be reused
without further treatment.
RESULTS AND DISCUSSION
Using β-naphthol, malononitrile, and benzaldehyde in a sto-
ichiometric ratio of 1:1.1:1 and 0.1 equivalents ferric hydrogen
sulfate (based on the aldehyde component), a reaction was de-
signed as a model in order to find out the optimum solvent, and
the results are shown in Table 1.
As it can be seen in Table 1, among the various solvents in-
vestigated, CH3CN was found to be the best choice. However,
ethanol, toluene, and benzene afforded satisfying yields. Mod-
erate and poor yields were obtained when the reactions were
carried out in THF and hexane respectively. As can be seen in
Representative spectral data for the selected products are:
(Entry 3): IR (KBr) (υmax, cm−1): 3440, 3325, 2185, 1680, Table 1, the catalyst could be reused without significant loss of
1665, 1595, 1550, 1502, 1365, 1255, 1200, 995, 840. its catalytic activity until at least five times.
TABLE 1
Influence of solvent on Fe(HSO4)3-catalyzed reaction of β-naphthol, malononitrile, and benzaldehyde and reusability study
Solvent
Acetonitril
Dichloroethane
Ethanol
Toluene
Benzene
THF
Hexane
Yielda,b
86
82
78
75
70
∼42
<20
—
Reusabilityc
86d
85e
83f
83g
∼80h
—
aAll the reactions were carried out under reflux condition for 4 h.
bIsolated yields.
cReusability of the recovered catalyst was investigated in CH3CN as the optimum solvent.
d-hReusability of the recovered catalyst in new runs (from run 2 [d] to run 6 [h]).

2-AMINO-4H-CHROMENES CATALYZED BY Fe(HSO4)3
1069
TABLE 2
CN
CN
CN
H
Ar
NH
Ar
Comparison of efficiency between ferric hydrogen sulfate
(FHS) and FeCl3 or NaHSO4
Ar
N
N
Fe(HSO4)3
..
OH
H
O
OH+
FeCl3 (10%) +
NaHSO4 FeCl3
FHS
(10%)
NaHSO4 (30%)
(30%)
(10%)
Catalyst
Yielda,b
Fe(HSO4)3
CN
80
20
52
86
CN
CN
CN
ArCH
ArCHO
CN
aAll the reactions were carried out under reflux condition for 4 h in
Fe(HSO4)3
Ar
NH2
CH3CN.
bIsolated yields.
O
OH
..
SCH. 2. The proposed mechanism.
In order to show what is so special about Fe(HSO4)3 and
also to find out that which part of the catalyst is responsible to
promote the reaction, we studied the reaction in the presence of
catalytic amount of FeCl3 and NaHSO4 at the same conditions. malononitrile, and para-methoxybenzaldehyde and para-N,N-
Comparing of catalytic efficiency of Fe(HSO4)3 (10%) with dimethylbenzaldehyde.
NaHSO4 (10% and 30%) and FeCl3 (10%) or a combination of
The proposed mechanism[19,22] for three-component synthe-
them showed that ferric hydrogen sulfate was acting even better sis of 2-amino-4H-chromene derivatives is shown in Scheme 2.
than a mixed catalyst (Table 2). Furthermore, it was revealed that The aldehyde first condenses with malononitrile to afford
both parts of the catalyst are involved in catalyzing the reaction. α-cyanocinnamonitrile derivatives by Knoevenagel addition.
To generalize the study, several substituted benzaldehydes Naphthol or phenol ortho C-alkylation gives an intermediate
were reacted with malononitrile and α- or β-naphthol in the which cyclizes via nucleophilic attack of O atom on the cyano
multicomponent one-pot reaction to afford substituted 2-amino- moiety following protonation and rearrangement to produce the
4H-chromenes derivatives in high yields. The results are illus- corresponding 2-amino-4H-chromene (Scheme 2).
trated in Table 2. The reactions proceeded easily under reflux
It is noteworthy that in the case of using resorcinol,
condition to afford the corresponding products in high yields us- aromatic aldehydes with electron- donating substituents (para-
ing aromatic aldehydes containing electron-withdrawing groups methoxybenzaldehyde and para-N,N-dimethylbenzaldehyde)
(such as nitro and halide groups) or electron-donating groups didn’t afford the expected corresponding compounds but
(such as methoxy groups). Although no significant differences obtained the α-cyanocinnamonitrile compound. We propose
in terms of yields in such a one-pot three-component reaction that electron-donating substituents on the aromatic ring
has been reported,[14] in the present study it was revealed that increase the electron density of C C double bonds in the
the yield of the reaction of aromatic aldehyde with malonon- intermediate (cyanocinnamonitrile), which may retard the
itrile and α-naphthol is almost better than that of β-naphthol. reaction of the phenol ortho C-alkylation with the electrophilic
As can be seen in Table 2, 4-nitrobenzaldehyde (entry 2) and C C double bond. In addition, we believe that the substituted
4-chlorobenzaldehyde (entry 4) were reacted with malononi- cyanocinnamonitrile intermediate shows low reactivity due to
trile and β-naphthol for 4 h, and they gave isolated yields of the full conjugation resulting in suppression of further reaction
the corresponding compounds 2 (88%) and 4 (85%), while 4- with phenol (Scheme 3).
nitrobenzaldehyde (entry 6) and 4-chlorobenzaldehyde (entry
Recently, we have reported the synthesis of FI-like Zr-based
8) were treated with malononitrile and α-naphthol for 3 h and catalysts and their application in polymerization of ethylene.[23]
the yields of the corresponding compounds are 92% and 94%, Encouraged by the results in the present study and also in
respectively. The results indicate that α-naphthol exhibits higher order to further extend the scope, we intended to use the
reactivity than β-naphthol at the same reaction conditions.
phenoxyimine-based catalysts of bis[1-[(phenylimino)methyl]-
To investigate more aspects of the new synthetic approach to 2-naphtholato]zirconium(IV) dichloride (1), bis[1-[(mesity
substituted 2-amino-4H-chromenes, and to find out the proba- limino)methyl]-2-naphtholato]zirconium(IV) dichloride (2),
ble limitations of the scope, we also studied the one-pot three- and
bis[1-[(2,6-diisopropylphenyl)imino]methyl-2-naphtho
component reaction of aldehyde, malononitrile, and resorcinol lato]zirconium(IV) dichloride (3) for the synthesis of 2-amino-
under similar conditions (Table 3, entries 9–12). The corre- 4H-chromene derivatives. To the best of our knowledge, this
sponding products were obtained in good yields. It should be is the first report of using such catalysts in the field of one-pot
mentioned that the reaction of benzaldehyde, malononitrile, and multicomponenet reactions.
phenol was carried out at the same conditions and no corre-
The catalysts preparation procedure and their characteriza-
sponding product was detected. It is notworthy that no detectable tion have been reported elsewhere.[23] It should be mentioned
chromene was found in the case of reaction between resorcinol, that due to the extreme sensitivity of the catalysts to moisture and

1070
H. ESHGHI ET AL.
TABLE 3
Results of one-pot three-component synthesis of 2-amino-4H-chromenes
Melting point (◦C)
Entry
Naphthol
Aldehyde
Producta
Time (h)
4.5
Yield(%)b
86
Found
Reported
1
β-Naphthol
278
278–280[14]
CN
NH2
CHO
O
O2N
MeO
Cl
2
β-Naphthol
β-Naphthol
β-Naphthol
4
5
4
88
80
85
186
185–186[14]
CHO
CN
NH2
O
NO2
3
4
181
210
182[17]
CN
CHO
NH2
O
OMe
CHO
208[17]
CN
NH2
O
Cl
5
6
α-Naphthol
α-Naphthol
3.5
87
92
210
210–211[18]
NH2
CN
CHO
O
O
3
240–242
239–241[18]
NH2
CHO
CN
CN
NO2
NO2
190–192[18]
NH2
7
α-Naphthol
4
86
188–190
CHO
O
OMe
OMe
(Continued on next page)

2-AMINO-4H-CHROMENES CATALYZED BY Fe(HSO4)3
1071
TABLE 3
Results of one-pot three-component synthesis of 2-amino-4H-chromenes (Continued)
Melting point (◦C)
Entry
8
Naphthol
Aldehyde
Producta
Time (h)
3
Yield(%)b
94
Found
230
Reported
232[18]
NH2
α-Naphthol
CHO
CN
O
Cl
Cl
9
Resorcinol
Resorcinol
HO
HO
O
O
NH2
CN
4
3
83
86
233
163
232–234[15,18]
CHO
10
NH2
CN
161–162[15]
CHO
Cl
Cl
O
11
Resorcinol
HO
NH2
CN
3
87
228
225–227[15]
CHO
Br
Br
O
12
Resorcinol
3.5
82
187
185–187[15]
HO
NH2
CN
CHO
Me
Me
aThe products were identified by 1HNMR and IR spectra.
bIsolated yields.
air, all the chemical reactions were done under an atmosphere the reaction in the presence of a catalytic amount of FI-
of nitrogen in toluene. like catalysts of 1–3 succeeded and the corresponding prod-
The one-pot reaction of aromatic aldehyde, malononi- ucts were isolated in moderate yields. This is the first
trile, and beta-naphthol using the bis-phenoxyimine cata- report of a Mannich reaction via three-component one-
lysts was carried out under the same conditions employed pot reactions in the presence of phenoxyimine Zr-based
for the ferric hydrogen sulfate. As can be seen in Table 4, catalysts.

1072
H. ESHGHI ET AL.
TABLE 4
Results of one-pot, three-component synthesis of 2-amino-4H-chromenes
Catalysts 1–3(left to rioght)
Cl
Cl
Cl
Cl
N
N
Cl
Cl
N
Zr
Zr
Zr
2
O
2
O
2
O
Product/yielda
Product/yield
1/30
5/30
1/30
5/35
1/40
5/45
aYields refer to isolated yield, reaction time = 4 h.
-
N
N
CN
C
..
O
+
O
+
O
-
CN
CN
CN
SCH. 3. Effect of electron-donating substitutions on stability of the cyanocinnamonitrile.
It should be pointed out that the purification procedure and
workup were extremely simple. After completion of the reac-
tion, the heterogeneous catalyst was easily removed through
filtration and the product was obtained after solvent evapo-
ration. The purified products were obtained by crystallization
from ethanol.
5. Bonsignore, L.; Loy, G.; Secci, D.; Calignano, A. Synthesis and pharma-
cological activity of 2-oxo-(2H) 1-benzopyran-3-carboxamide derivatives.
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CONCLUSION
One-pot synthesis of substituted 2-amino-4H-chromene
derivatives has been reported. Fe(HSO4)3 was found to be an ef-
ficient catalyst due to its applicability to the various compounds,
heterogeneity of the catalyst, high reusability, bifunctionality,
reasonable reaction times, and high yields of the products. Three
FI-like catalysts bearing phenoxyimine chelate ligands were ex-
amined and the corresponding products were obtained in mod-
erate yields.
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chromene derivatives containing sulfur-nitrogen heterocycles. Phosphorus
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Kasibhatla, S.; Cai, S.X. J. Med. Chem. 2004, 47, 6299–6304.
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