One-pot, three-component synthesis of pyranocoumarins containing an aroyl group

Article abstract of DOI:10.1515/hc-2014-0099

An expeditious method to prepare pyranocoumarins containing an aroyl group by the three-component reaction of 4-hydroxycoumarin with arylglyoxals and malononitrile is described. The reaction is efficiently catalyzed by Mohr's salt, and the products were o

Full text of DOI:10.1515/hc-2014-0099

Heterocycl. Commun. 2014; 20(5): 285–288
Saeed Khodabakhshi*, Fariba Jafari, Farzaneh Marahel and Mojtaba Baghernejad
One-pot, three-component synthesis of
pyranocoumarins containing an aroyl group
Abstract: An expeditious method to prepare pyranocou- malononitrile in the presence of weakly basic or acidic cata-
marins containing an aroyl group by the three-component lysts [9–13]. To the best of our knowledge, there is no report
reaction of 4-hydroxycoumarin with arylglyoxals and on the synthesis of pyrano[3,2-c]coumarins starting from
malononitrile is described. The reaction is efficiently cata- arylglyoxals in a three-component reaction.
lyzed by Mohr’s salt, and the products were obtained in
In recent years, we have been involved in the syn-
good to excellent yields with high purity. The method is thesis of new heterocycles containing a coumarin moiety
simple, inexpensive, and environmentally friendly.
[14–18]. Herein, we wish to report the synthesis of new
pyrano[3,2-c]coumarins 4 by the one-pot, three-compo-
Keywords: arylglyoxal; catalyst; 4-hydroxycoumarin; nent reaction of 4-hydroxycoumarin (1) with arylglyoxals
malononitrile; Mohr’s salt; pyranocoumarins.
2 and malononitrile (3) in good to excellent yields using
Mohr’s salt as an efficient catalyst. Considering that there
are many reports on the synthesis of pyranocoumarins
employing aromatic aldehydes, in this report, some
arylglyoxals are introduced as potential alternatives to
produce molecules of type 4-containing aroyl groups.
DOI 10.1515/hc-2014-0099
Received June 4, 2014; accepted August 11, 2014; previously pub-
lished online September 19, 2014
Introduction
Results and discussion
Pyran, a well-known heterocyclic system, is a common and On the basis of our previous experience related to the
important moiety of a variety of natural products and medic- synthesis of pyranocoumarins [19], the model reaction
inal agents [1, 2]. Besides, pyrano-fused heterocycles have initially involved the solvent system EtOH/H2O (1:1). After
attracted considerable synthetic interest because of their some optimizations including temperature and catalyst
biological, pharmaceutical, and material properties [3–5]. amounts, it was found that generally good yields of com-
In the last decades, some research groups have focused pound 4a were obtained when the mixture of the three
on pyranocoumarins and their heteroanalogous chemistry starting components with Mohr’s salt (10 mol%) was ini-
because they exhibit a variety of biological properties such tially stirred in EtOH/H2O (1:1) at room temperature and
as antifungal, insecticidal, anticancer, anti-HIV, anti-inflam- then heated under reflux (Scheme 1). During the optimi-
matory, and antibacterial activities [6–8]. Among pyrano- zation of the reaction conditions, it was found that the
coumarins, the pyrano[3,2-c]coumarin compounds are the Mohr’s salt is a more effective catalyst than common bases
most synthetically accessible. Thus far, several methods and acids. Table 1 shows the results obtained with other
have been developed for the preparation of pyrano[3,2-c] attempted catalysts in the synthesis of 4a.
coumarins, but the most conventional approach to this
The results illustrate the merit of Mohr’s salt in com-
class of compounds is the three-component condensa- parison with other catalysts in the aspects of yields. No
tion of a 4-hydroxycoumarin, an aromatic aldehyde, and product was obtained in the attempted reactions of entries
1–4 (Table 1). Product 4a was obtained in low yield in the
presence of NH4Cl (entry 5). The scope of this reaction
was studied using a range of arylglyoxals 2. In all cases,
derivatives of type 4 with high purity were obtained. It
was also observed that the process tolerates both elec-
tron-donating and electron-withdrawing substituents
on the aromatic ring. The reactions were completed after
100–150 min, and the products were separated by simple
filtration of the precipitate. There was no evidence of the
*Corresponding author: Saeed Khodabakhshi, Young Researchers
and Elite Club, Gachsaran Branch, Islamic Azad University,
Gachsaran, Iran, e-mail: saeidkhm@yahoo.com
Fariba Jafari: Department of Chemistry, Dezful Branch, Islamic Azad
University, Dezful, Iran
Farzaneh Marahel: Department of Chemistry, Omidiyeh Branch,
Islamic Azad University, Omidiyeh, Iran
Mojtaba Baghernejad: Young Researchers and Elite Club, Gachsaran
Branch, Islamic Azad University, Gachsaran, Iran
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286ꢀ
ꢀS. Khodabakhshi et al.: Synthesis of pyranocoumarins containing an aroyl group
O
O
OH
HO
O
Ar
O
O
OH
O
EtOH/H2O (1:1)
FeSO4 (NH4)2SO4 6H2O
5
Ar
OH
H
OH
CN
CN
H2C
NH2
∆
rt to
O
O
NC
O
O
1
2a-i
3
Ar
a
: Ar = Ph
f: Ar = 3-MeO-C6H4
g: Ar = 4-MeO-C6H4
h: Ar = 1-naphthyl
i: Ar = 2-naphthyl
O
O
b: Ar = 4-Cl-C6H4
4a-i
c
: Ar = 4-Br-C6H4
d: Ar = 3-NO2-C6H4
e: Ar = 4-NO2-C6H4
Scheme 1ꢂSynthesis of pyrano[3,2-c]coumarins.
analyses. For example, the 1H NMR spectrum of 4a exhib-
its two sharp singlets for methine (δꢀ= ꢀ5.42) and NH2 (δꢀ= ꢀ7.69)
protons. The signals at δꢀ= ꢀ7.53–8.16 correspond to aro-
matic protons. The proton decoupled 13C NMR spectrum
of 4a shows 18 distinct resonances in agreement with
the proposed structure. Characteristic signals at δꢀ= ꢀ198.1,
51.9, and 37.1 correspond to ketonic Cꢀ= ꢀO, olefinic carbon,
and carbon joined to nitrile group, respectively [20].
The IR spectrum of 4a shows characteristic bands at
3402–3292 cm-1 (NH2), 2201 cm-1 (CN), 1708 cm-1 (lactonic
Cꢀ= ꢀO), and 1678 cm-1 (ketonic Cꢀ= ꢀO).
Table 1ꢂComparison of Mohr’s salt with other catalysts in the
synthesis of 4a.
Entryꢁ
Catalyst
ꢁ
Yield (%)ꢁ
Time (min)
1ꢃ
2ꢃ
3ꢃ
4ꢃ
5ꢃ
6ꢃ
FeCl3
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
–ꢃ
–ꢃ
240
240
240
240
240
100
AlCl3
p-TSA
Na2CO3
NH4Cl
–ꢃ
–ꢃ
43ꢃ
80ꢃ
Mohr’s salt ꢃ
presumed compound 5 (Scheme 1) that would be derived
The suggested mechanisms for the formation of 4 is
by the reaction of two equivalents of 4-hydroxycoumarin shown in Scheme 2. The reaction is thought to take place
with the arylglyoxal.
in three steps. The initial event involves the generation
The structures of compounds 4 were assigned on of an intermediate aroylmethylene via the condensation
the basis of comprehensive spectroscopic and elemental of the arylglyoxal and malononitrile. In the next step, a
Ar
OH
OH
Ar
H
O
O
O
H
H
H
N
H
OH
OH2
Ar
HO
H
Ar
Ar
H
N
H
H
H
H
H
H
[FeSO4]
O
OH
O
O
H
NH3
NC
NC CN
CN
H
NH3
NC
NC
H
H
N
H
N
H
H
NH2
H
H
H
N
H
NC
H
NC
C
NC
Ar
O
C
O
NH
O
Ar
-H2O
Ar
-NH4
O
H
H
O
O
O
O
H
O
O
O
NH3
4
O
NH3
Scheme 2ꢂA plausible mechanism for the synthesis of 4 using Mohr’s salt.
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ꢂ287
2-Amino-4-(4-bromobenzoyl)-3-cyano-4H,5H-pyrano[3,2-c]
chromene-5-one (4c)ꢀLight yellow crystals; yield 85%; mp 263–
265°C; time 140 min; IR: ν 3316, 3186, 3027, 2871, 2203, 1715, 1673,
1582, 1374, 1057, 620 cm-1; 1H NMR: δ 8.10 (d, 2H, J ꢀ= ꢀ 8.6 Hz), (dd, 1H,
J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 1.6 Hz), 7.85 (d, 2H, J ꢀ= ꢀ 8 Hz), 7.75 (td, 1H, J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ
1.6 Hz), 7.71 (s, 2H), 7.58–7.53 (m, 2H), 5.42 (s, 1H); 13C NMR: 197.5, 159.5,
154.7, 152.1, 134.4, 133.4, 132.0, 131.0, 125.0, 122.1, 116.8, 112.5, 101.6, 51.7,
37.2. Anal. Calcd for C20H11BrN2O4: C, 56.76; H, 2.62; N, 6.62. Found: C,
56.89; H, 2.51; N, 6.58.
Michael-type addition and subsequent intramolecular
heterocyclization give the desired product 4.
Conclusion
Synthesis of new pyrano[3,2-c]coumarins via the three-
component coupling reaction of 4-hydroxycoumarin with
arylglyoxals and malononitrile is described. The advan-
tages of the present method are high yields, short reac-
tion times, excellent chemoselectivity, use of commercial
Mohr’s salt as an extremely efficient catalyst, and ease of
product isolation and purification.
2-Amino-4-(3-nitrobenzoyl)-3-cyano-4H,5H-pyrano[3,2-c]
chromene-5-one (4d)ꢀYellow crystals; yield: 85%; mp 248–250°C;
time 110 min; IR: ν 3415, 3086, 2928, 2197, 1712, 1673, 1609, 1525, 1385,
1
1352, 1063 cm-1; H NMR: δ 8.83 (t, 1H, J ꢀ= ꢀ 1.8 Hz), 8.65 (d, 1 H, J ꢀ= ꢀ
8 Hz), 8.59 (d, 1H),7.97 (d, 1H, J ꢀ= ꢀ 8 Hz), 7.93–7.89 (m, 1H), 7.82–7.77 (m,
3H), 7.59–7.53 (m, 2H), 5.57 (s, 1H) ppm; 13C NMR: δ 197.0, 160.1, 159.5,
154.8, 152.1, 148.1, 136.6, 135.2, 133.5, 130.9, 128.3, 125.1, 123.1, 122.2,
118.5, 116.8, 112.5, 101.3, 51.2, 37.6. Anal. Calcd for C20H11N3O6: C, 61.70;
H, 2.85; N, 10.79. Found: C, 61.88; H, 2.77; N, 10.83.
Experimental
2-Amino-4-(4-nitrobenzoyl)-3-cyano-4H,5H-pyrano[3,2-c]
chromene-5-one (4e)ꢀYellow crystals; yield 85%; mp 273–275°C;
time 105 min; IR: ν 3461, 3336, 2192, 1720, 1681, 1613, 1517, 1383, 1326,
1070, 1064 cm-1; 1H NMR: δ 8.44 (d, 2H, J ꢀ= ꢀ 8 Hz), 8.40 (d, 2H, J ꢀ= ꢀ 8 Hz),
7.90 (dd, 1H, J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 1.4 Hz), 7.79 (td, 3H, J1 ꢀ= ꢀ 8, J2 ꢀ= ꢀ 1.5 Hz),
7.59–7.54 (m, 2H), 5.51 (s, 1H); 13C NMR: δ 197.7, 160.1, 159.5, 154.8, 152.1,
150.4, 140.2, 133.5, 130.4, 125.1, 124.0, 122.2, 116.8, 112.5, 101.3, 51.2, 37.9.
Anal. Calcd for C20H11N3O6: C, 61.70; H, 2.85; N, 10.79. Found: C, 61.79;
H, 2.72; N, 10.71.
Chemicals were purchased from Merck and Aldrich chemical com-
panies. Arylglyoxals were synthesized according to our previous
reports [21, 22]. Melting points were measured on an electrothermal
KSB1N apparatus. IR spectra were recorded by a JASCO FT-IR-680
1
plus spectrometer using KBr pellets. H NMR and 13C NMR spectra
were recorded on an FT-NMR Bruker Avance spectrometer at 300 and
75 MHz, respectively, in DMSO-d6. TLC was performed on TLC-grade
silica gel-G/UV 254-nm plates.
2-Amino-4-(3-methoxybenzoyl)-3-cyano-4H,5H-pyrano[3,2-c]
chromene-5-one (4f)ꢀLight yellow crystals; yield 90%; mp 268–
270°C; time 100 min; IR: ν ꢀ= ꢀ 3477, 3344, 3072, 2934, 2196, 1721, 1674,
1577, 1386, 1065 cm-1; 1H NMR: δ 7.90 (dd, 1H, J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 2 Hz), 7.78
(td, 2H, J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 2 Hz), 7.70 (s, 2H), 7.62 (t, 1H, J ꢀ= ꢀ 2 Hz), 7.57–7.52
General procedure for the synthesis of compounds 4
To a 25-mL round-bottomed flask, 4-hydroxycoumarin (1.0 mmol),
arylglyoxal (1.2 mmol), malononitrile (1.2 mmol), EtOH/H2O (1:1,
10 mL), and Mohr’ salt (0.1 mmol) were added. The mixture was stirred
at room temperature for 30 min, then vigorously stirred and heated
under reflux for the period indicated below. The progress of the reac-
tion was monitored by TLC. Upon completion, the reaction system
was cooled to room temperature, and the precipitate was filtered. The
pure product was obtained afer crystallization from EtOH/THF (3:1).
(m, 3H), 7.32 (dd, 1H, J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 2 Hz), 5.40 (s, 1H), 3.87 (s, 3H); 13
C
NMR: δ 197.7, 160.0, 159.6, 159.4, 154.7, 152.1, 136.6, 133.3, 130.0, 125.0,
122.1, 121.6, 120.2, 118.5, 116.8, 113.5, 112.6, 101.9, 55.3, 52.0, 37.4. Anal.
Calcd for C21H14N2O5: C, 67.38; H, 3.77; N, 7.48. Found: C, 67.48; H, 3.70;
N, 7.56.
2-Amino-4-(4-methoxybenzoyl)-3-cyano-4H,5H-pyrano[3,2-c]
chromene-5-one (4g)ꢀLight yellow crystals; yield 80%; mp 266–
268°C; time 130 min; IR: ν ꢀ= ꢀ 3426, 3320, 2926, 2200, 1714, 1673, 1597,
1383, 1062 cm-1; 1H NMR: δ 8.15 (d, 2H, J ꢀ= ꢀ 9 Hz), 7.89 (dd, 1H, J1 ꢀ= ꢀ 8 Hz,
J2 ꢀ= ꢀ 1.4 Hz), 7.80–7.74 (td, 1H, J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 1.6 Hz), 7.65 (s, 2H), 7.56 (d,
1H, J ꢀ= ꢀ 9 Hz), 7.53 (d, 1H, J ꢀ= ꢀ 9 Hz), 7.14 (d, 2H, J ꢀ= ꢀ 9.0 Hz), 5.36 (s, 1H),
3.90 (s, 3H); 13C NMR: δ 196.2, 163.9, 160.0, 159.5, 154.6, 152.0, 133.2,
131.6, 128.1, 124.9, 122.1, 118.6, 116.7, 114.1, 112.6, 102.1, 55.6, 52.2, 36.7.
Anal. Calcd for C21H14N2O5: C, 67.38; H, 3.77; N, 7.48. Found: C, 67.40;
H, 3.73; N, 7.40.
2-Amino-4-benzoyl-3-cyano-4H,5H-pyrano[3,2-c]chromene-
5-one (4a)ꢀLight yellow crystals; yield 80%; mp 272–274°C; time
1
100 min; IR: ν 3402, 3292, 2201, 1708, 1678, 1606, 1373, 1064 cm-1; H
NMR: δ 8.16 (s, 2H, J ꢀ= ꢀ 8 Hz), 7.90 (dd, 1H, J1 ꢀ= ꢀ 8, J2 ꢀ= ꢀ 1.6 Hz), 7.79 (dd,
1H, J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 1.6 Hz), 7.69 (s, 2H), 7.62 (t, 2H, J ꢀ= ꢀ 8 Hz), 7.57–7.53 (m,
2H), 5.42 (s, 1H); 13C NMR: δ 198.1, 160.0, 159.5, 154.7, 152.1, 135.3, 134.1,
133.3, 129.1, 128.8, 125.0, 122.1, 118.5, 116.8, 112.5, 101.9, 51.9, 37.1. Anal.
Calcd for C20H12N2O4: C, 69.76; H, 3.51; N, 8.14. Found: C, 69.55; H, 3.41;
N, 8.09.
2-Amino-4-(4-chlorobenzoyl)-3-cyano-4H,5H-pyrano[3,2-c] 2-Amino-4-(1-naphthoyl)-3-cyano-4H,5H-pyrano[3,2-c]
chromene-5-one (4b)ꢀLight yellow crystals; yield 90%; mp 263– chromene-5-one (4h)ꢀYellow crystals; yield 90%; mp 271–273°C;
265°C; time 120 min; IR: ν 3319, 3186, 3027, 2871, 2205, 1713, 1673, time 100 min; IR: ν 3477, 3327, 3050, 2923, 2191, 1727.91, 1674.87,
1587, 1375, 1058, 759 cm-1; H NMR: δ 8.20 (d, 2H, J ꢀ= ꢀ 8 Hz), 7.89 (dd, 1573.63, 1381.75, 1177 cm-1; H NMR: δ 8.37 (m, 2H), 8.24 (d, 1H, J ꢀ= ꢀ
1H, J1 ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 1.4 Hz), 7.81–7.69 (m, 5H), 7.57–7.52 (m, 2H), 5.43 (s, 8 Hz), 8.09–8.05 (m, 1H), 7.92 (dd, 1H, J ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 1.8 Hz), 7.80 (td,
1H); 13C NMR: δ 197.2, 160.0, 159.5, 154.7, 152.1, 139.2, 134.1, 133.3, 130.9, 1H, J ꢀ= ꢀ 8 Hz, J2 ꢀ= ꢀ 1.6 Hz), 7.75–7.70 (m, 3H), 7.66–7.54 (m, 4H), 5.43
129.0, 125.0, 122.1, 118.4, 116.8, 112.5, 101.6, 51.7, 37.2. Anal. Calcd for (s, 1H); 13C NMR: δ 200.3, 160.2, 159.6, 154.6, 152.2, 134.2, 133.4, 133.3,
C20H11ClN2O4: C, 63.42; H, 2.93; N, 7.40. Found: C, 63.61; H, 2.99; N, 7.35. 133.2, 129.8, 129.0, 128.5, 128.0, 126.5, 125.1, 125.0, 124.7, 122.2, 118.3,
1
1
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116.8, 112.6, 101.7, 51.4, 38.6. Anal. Calcd for C24H14N2O4: C, 73.09; H,
3.58; N, 7.10. Found: C, 73.13; H, 3.55; N, 7.01.
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2-Amino-4-(2-naphthoyl)-3-cyano-4H,5H-pyrano[3,2-c]
chromene-5-one (4i)ꢀYellow crystals; yield 95%; mp 278–280°C;
time 100 min; IR: ν 3428, 3321, 2938, 2199, 1714, 1674, 1631, 1597, 1569, [10] Barraja, P.; Spano, V.; Patrizia, D.; Carbone, A.; Cirrincione, G.;
1
1382, 1172 cm-1; H NMR: δ 8.44 (s, 1H), 7.97 (d, 1H, J ꢀ= ꢀ 8 Hz), 7.83 (d,
1H, J ꢀ= ꢀ 8 Hz), 7.74 (t, 1H, J ꢀ= ꢀ 8 Hz), 7.62–7.52 (m, 3H), 7.48 (d, 1H, J ꢀ= ꢀ 8
Hz), 7.44 (t, 1H, J ꢀ= ꢀ 8 Hz), 7.39 (s, 2H), 7.33 (d, 1H, J ꢀ= ꢀ 7 Hz), 5.47 (s, 1H);
13C NMR: δ 199.6, 159.5, 157.8, 153.8, 152.0, 133.2, 132.9, 130.9, 128.4,
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