CAN-catalyzed synthesis of 10-arylpyrano[3,2-b]chromene-4,9-diones under solvent-free conditions

Article abstract of DOI:10.1007/s11164-012-0995-x

A novel and efficient one-pot synthesis of 10-aryl-7,8-dihydropyrano[3,2-b] chromene-4,9(6H,10H)-diones by three-component reaction of aromatic aldehydes, 5-hydroxy-2-methylpyran-4-one, and cyclic 1,3-dicarbonyl compounds in the presence of a catalytic amount of ceric ammonium nitrate under solvent-free conditions is described. The advantages of this method include operational simplicity, short reaction time, recyclable catalyst, and high yields.

Full text of DOI:10.1007/s11164-012-0995-x

Res Chem Intermed
DOI 10.1007/s11164-012-0995-x
CAN-catalyzed synthesis of 10-arylpyrano[3,2-b]
chromene-4,9-diones under solvent-free conditions
•
•
•
•
Yuling Li Xiangxue Meng Gan Cai Baixiang Du
Bo Zhao
Received: 6 November 2012 / Accepted: 19 December 2012
Ó Springer Science+Business Media Dordrecht 2013
Abstract A novel and efficient one-pot synthesis of 10-aryl-7,8-dihydropyr-
ano[3,2-b]chromene-4,9(6H,10H)-diones by three-component reaction of aromatic
aldehydes, 5-hydroxy-2-methylpyran-4-one, and cyclic 1,3-dicarbonyl compounds
in the presence of a catalytic amount of ceric ammonium nitrate under solvent-free
conditions is described. The advantages of this method include operational sim-
plicity, short reaction time, recyclable catalyst, and high yields.
Keywords MCRs Á CAN Á Pyrano[3,2-b]chromene Á Synthesis Á Solvent-free
Introduction
Pyrans and fused pyran derivatives are an important structural groups in many
natural and synthetic compounds with a wide range of biological activity, for
example anticancer [1], anti-tuberculosis [2], anti-HIV [3], calcium channel
antagonist activity [4], anti-fungal agents [5], antimicrobial [6], antiproliferative
[7], antidiabetic [8], anti-inflammatory, and antiviral [9]. Pyranochromenes, also,
are known for their biological properties including antioxidant and cytotoxic
activity [10]. Because of the importance of pyranochromene derivatives, different
synthetic methods have been developed for synthesis of this group of compounds.
Miyazaki et al. [11] prepared tricyclic compounds containing the pyranochromene
skeleton in very good yields from salicylaldehyde dimethyl acetal and unsaturated
alcohols in benzene in the presence of p-toluenesulfonic acid (p-TsOH). Yadav et al.
[12] reported the reaction of glycals, o-hydroxybenzaldehydes, and trimethyl
orthoformate in the presence of a catalytic amount of scandium triflate under mild
Y. Li (&) Á X. Meng Á G. Cai Á B. Du Á B. Zhao
School of Chemistry and Chemical Engineering, Jiangsu Key Laboratory of Green Synthetic
Chemistry for Functional Materials, Jiangsu Normal University, Xuzhou 221116, China
e-mail: Ylli19722@163.com
123

Y. Li et al.
reaction conditions to afford the corresponding cis-annelated pyranochromenes in
good yields with high diastereoselectivity. Reddy et al. [13] reported the synthesis
of dihydropyrano[3,2-b]chromenediones via three-component coupling of kojic
acid, aldehydes, and 1,3-diones, with InCl3 as catalyst, under solvent-free
conditions. Li et al. [14, 15] synthesized dihydropyrano[3,2-b]chromenediones
from kojic acid, aldehydes, and active methylene carbonyl compounds, with alum as
catalyst or FeCl3–SiO2 as solid acid catalyst. However, these methods suffer from
such disadvantages as use of toxic organic solvents, expensive catalysts, and long
reaction times. Development of a synthetic procedure free from these problems yet
environmentally benign, simple, efficient, and cost-effective for the synthesis of
pyranopyranones remains an important task.
Multicomponent reactions (MCRs), in which multiple reactions are combined in
a one-pot synthetic operation, have been widely used to prepare bioactive
heterocyclic compounds [16]. MCRs with environmentally benign methods have
been one of most important topics of green chemistry. One approach used to reduce
the environmental impact of a reaction is to conduct it under solvent-free conditions
[17]. Advantages of solvent-free reactions include low cost, ease of work-up, and
clean and efficient processes. The solvent-free reaction has became a useful strategy
for formation of heterocycles.
In recent years, cerium ammonium nitrate (CAN) has attracted special attention and
has been extensively used as a useful catalyst in synthetic organic chemistry, because it
is eco-friendly, easy to handle, highly reactive, and economically viable [18]. However,
most examples require stoichiometric quantities of CAN. In continuation of our studies
indevelopingenvironmentallybenignmethodsforsynthesisofheterocycliccompounds
[19–21], here we report on a highly atom-economic synthesis of 10-aryl-pyrano
[3,2-b]chromene-4,9(6H,10H)-diones by one-pot reaction of aromatic aldehydes,
5-hydroxy-2-methylpyran-4-one, and cyclic 1,3-dicarbonyl compounds under solvent-
free conditions at 120 °C requiring CAN at only 10 mol% (Scheme 1). To the best of
our knowledge, this method has not been reported in the literature.
Results and discussion
Initially, we investigated the condensation reaction of 4-chlorobenzaldehyde,
5-hydroxy-2-methylpyran-4-one, and 1,3-cyclohexanedione using 10 mol% of CAN
in different solvents. The results are listed in Table 1. Under these conditions
product 4a was formed in low yields (Table 1, entries 1–3), even after 9 h, whereas
O
Ar
O
O
CAN
120°C
O
O
R
R
O
O
+
OH
+
Ar-CHO
R
solvent-free
O
R
R = H or CH
3
4
1
2
3
Scheme 1 Synthesis of compound 4
123

CAN-catalyzed synthesis
the same reaction under solvent-free conditions provided 52 % 4a in only 0.5 h at
60 °C (Table 1, entry 5).
To further optimize the reaction conditions, we investigated the effect of
temperature on reaction rate and on product yields. The work showed that no
product could be detected at room temperature (Table 1, entry 4) even after 5 h. The
yield of product 4a was improved and the reaction time was shortened as the
temperature was increased from 60 to 120 °C (Table 1, entries 5–7). The yield
reached a plateau when temperature was further increased to 130 °C (Table 1, entry
8). So the most suitable reaction temperature was 120 °C.
We also examined this reaction using different catalysts under solvent-free
conditions; again the results are listed in Table 1. It was found that CAN had better
catalytic activity than p-TSA, FeCl3, ZnCl2, and AlCl3 (Table 1, entries 9–12).
Moreover, we found that yields were obviously affected by the amount of CAN
used. Increasing the quantity of CAN from 2 to 10 mol% increased product yield
from 63 to 95 % (Table 1, entries 14–16). The yield levelled off when 15 mol%
CAN was used in the reaction (Table 1, entry 17). The catalytic activity of recycled
CAN was also examined. CAN was reused four times without apparent loss of
activity (Table 1, entry 16). In addition, no desired product was detected in the
absence of the catalyst (Table 1, entry 13). These results showed that CAN was
essential for the reaction, and the best results were obtained when the reaction was
performed with 10 mol% of CAN under solvent-free conditions at 120 °C.
With these optimized conditions, to investigate the generality of the reaction
we extended our study to different aromatic aldehydes to prepare a series of
Table 1 Optimization of the
reaction conditions for synthesis
of 4a
Entry
Solvent
Catalyst
(mol%)
Temp.
(°C)
Time
(min)
Yield
(%)a
1
EtOH
DMF
MeCN
None
None
None
None
None
None
None
None
None
None
None
None
None
CAN (10)
CAN (10)
CAN (10)
CAN (10)
CAN (10)
CAN (10)
CAN (10)
CAN (10)
p-TSA (10)
ZnCl2 (10)
AlCl3 (10)
FeCl3 (10)
None
Reflux
120
Reflux
r.t.
540
540
540
300
120
60
Trace
32
2
3
Trace
0
4
5
60
52
6
90
72
7
120
130
120
120
120
120
120
120
120
120
30
95
8
30
94
9
30
34
10
11
12
13
14
15
16
30
42
30
45
30
41
120
30
0
Reaction conditions: 1 mmol
4-chlorobenzaldehyde, 1 mmol
5-hydroxy-2-methylpyran-
CAN (2)
63
CAN (5)
30
72
4-one, 1 mmol 1,3-cyclohexanedione
a
Isolated yields
CAN (10)
30
95 (94,
95, 93)b
b
Catalyst was reused four times
after drying
17
None
CAN (15)
120
30
95
123

Y. Li et al.
10-aryl-7,8-dihydropyrano[3,2-b]chromene-4,9(6H,10H)-diones. The results, sum-
marized in Table 2, showed that aromatic aldehydes with electron-withdrawing or
electron-releasing substituents were converted to their corresponding 10-aryl-7,
8-dihydropyrano[3,2-b]chromene-4,9(6H,10H)-dione derivatives in good yields under
the optimum conditions described above. All the products were characterized by
their melting points, 1H NMR, IR, and HRMS. Furthermore, the structure of 4g was
established by an X-ray crystallographic analysis (Fig. 1) [22].
On the basis of the literature [13], we propose a plausible mechanism for
formation of 4 (Scheme 2). In first step, the Knoevenagel condensation between
aromatic aldehyde 1 and cyclic 1,3-dicarbonyl compounds 3 in the presence of a
catalytic amount of CAN gives an intermediate heterodiene 5, benzylidenecyclo-
hexane-1,3-dione. Hetero Diels–Alder reaction of 5-hydroxy-2-methylpyran-4-one
2 with 5 followed by dehydration then furnishes the corresponding products 4a–4t.
Experimental
General
Melting points were determined in open capillaries without further correction. IR
1
spectra were recorded on a Tensor 27 spectrometer in KBr. H NMR spectra were
Table 2 Synthesis of 4 under
solvent-free conditions
Entry
Ar
R
Product
Time
(min)
Yield
(%)a
1
4-ClC6H4
H
4a
4b
4c
4d
4e
4f
30
30
30
35
30
30
30
30
30
30
40
35
35
30
30
30
35
30
30
30
95
90
90
93
92
85
87
91
86
84
82
84
89
91
88
92
84
86
94
88
2
4-BrC6H4
H
3
4-FC6H4
H
4
3-CH3OC6H4
3-FC6H4
H
5
H
6
3,4-Cl2C6H3
2,4-Cl2C6H3
4-CH3C6H4
2,3-Cl2C6H3
3,4-OCH2OC6H3
3-HOC6H4
4-HOC6H4
3-CF3C6H4
2-ClC6H4
H
7
H
4g
4h
4i
8
H
9
H
10
11
12
13
14
15
16
17
18
19
20
H
4j
H
4k
4l
H
H
4m
4n
4o
4p
4q
4r
4s
H
2-BrC6H4
H
4-BrC6H4
CH3
CH3
CH3
CH3
CH3
Reaction conditions: 1 mmol
5-hydroxy-2-methylpyran-
4-HOC6H4
3,4-(CH3)2C6H3
4-ClC6H4
4-one, 1 mmol aromatic aldehyde,
1 mmol cyclic 1,3-dicarbonyl
compound, solvent free, 120 °C
3,4-OCH2OC6H3
4t
a
Isolated yield
123

CAN-catalyzed synthesis
Fig. 1 The crystal structure of 4g
O
Ar
O
O
O
CAN
-H2O
+
+
ArCHO
R
R
R
R
HO
O
O
3
1
5
2
O
Ar
O
Ar
O
O
4+2
R
R
-H2O
O
O
R
R
OH
O
O
4
6
Scheme 2 Mechanism of the reaction
obtained from solution in CDCl3, with Me4Si as internal standard, using a Bruker-
400 spectrometer. HRMS data were obtained by use of a MicroTOF-QII instrument.
General procedure for preparation of 4
A mixture of aromatic aldehyde 1 (1 mmol), 5-hydroxy-2-methylpyran-4-one 2
(1 mmol), cyclic 1,3-dicarbonyl compounds 3 (1 mmol), and CAN (10 mol%) was
stirred at 120 °C under solvent-free conditions for the given time (Table 2). On
completion of the reaction (monitored by TLC), the reaction mixture was cooled to
123

Y. Li et al.
room temperature, and ethyl acetate was added. The mixture was shaken well to
dissolve all organic components, then filtered to remove CAN. The filtrate was
concentrated and purified by silica gel column chromatography to give 4.
Characterization data
10-(4-Chlorophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4a)
White powder, m.p. 213–215 °C; 1H NMR (CDCl3, 400 MHz) d: 1.95–2.12 (m, 2H,
CH2), 2.20 (s, 3H, CH3), 2.32–2.46 (m, 2H, CH2), 2.66–2.87 (m, 2H, CH2), 4.88 (s,
1H, CH), 6.18 (s, 1H, =CH), 7.18–7.29 (m, 4H, ArH); IR (KBr) m: 2954, 2891, 1671,
1655, 1640, 1627, 1600, 1490, 1377, 848 cm-1; HRMS calcd for C19H15ClO4
(M ? Na)?: requires 365.0557, found: 365.0550.
10-(4-Bromophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4b)
White powder, m.p. 236–238 °C; 1H NMR (CDCl3, 400 MHz) d: 1.97–2.13 (m, 2H,
CH2), 2.20 (s, 3H, CH3), 2.32–2.46 (m, 2H, CH2), 2.67–2.87 (m, 2H, CH2), 4.87 (s,
1H, CH), 6.18 (s, 1H, =CH), 7.16 (d, 2H, ArH, J = 8.4 Hz), 7.44 (d, 2H, ArH,
J = 8.4 Hz); IR (KBr) m: 2960, 2923, 2870, 2850, 2850, 1673, 1642, 1629, 1600,
1487, 1375, 816 cm-1; HRMS calcd for C19H15BrO4 (M ? Na)?: requires
409.0051, found: 409.0023.
10-(4-Fluorophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4c)
1
Yellow powder, m.p. 218–220 °C; H NMR (CDCl3, 400 MHz) d: 1.95–2.12 (m,
2H, CH2), 2.20 (s, 3H, CH3), 2.32–2.43 (m, 2H, CH2), 2.67–2.88 (m, 2H, CH2), 4.90
(s, 1H, CH), 6.19 (s, 1H, =CH), 6.88–6.92 (m, 2H, ArH), 6.97–7.02 (m, 1H, ArH),
7.23–7.24 (m, 1H, ArH); IR (KBr) m: 2924, 2852, 1674, 1641, 1628, 1603, 1509,
1383, 848 cm-1; HRMS calcd for C19H15FO4 (M ? H)?: requires 327.1033, found:
327.1026.
10-(3-Methoxyphenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4d)
1
Yellow powder, m.p. 193–194 °C; H NMR (CDCl3, 400 MHz) d: 1.97–2.12 (m,
2H, CH2), 2.20 (s, 3H, CH3), 2.31–2.47 (m, 2H, CH2), 2.67–2.89 (m, 2H, CH2), 3.79
(s, 3H, OCH3), 4.88 (s, 1H, CH), 6.18 (s, 1H, =CH), 6.78 (dd, 1H, ArH,
J1 = 2.0 Hz, J2 = 8.0 Hz), 6.81 (s, 1H, ArH), 6.86 (d, 1H, ArH, J = 8.0 Hz), 7.23
(t, 1H, ArH, J = 8.0 Hz); IR (KBr) m: 3051, 2960, 2924, 2852, 1673, 1657, 1636,
1599, 1491, 1374, 771, 720 cm-1; HRMS calcd for C20H18O5 (M ? Na)?: requires
361.1052, found: 361.1025.
123

CAN-catalyzed synthesis
10-(3-Fluorophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4e)
1
Yellow powder, m.p. 207–209 °C; H NMR (CDCl3, 400 MHz) d: 1.98–2.13 (m,
2H, CH2), 2.20 (s, 3H, CH3), 2.32–2.47 (m, 2H, CH2), 2.67–2.88 (m, 2H, CH2), 4.90
(s, 1H, CH), 6.19 (s, 1H, =CH), 6.93–6.99 (m, 2H, ArH), 7.07 (d, 1H, ArH,
J = 7.6 Hz), 7.29 (d, 1H, ArH, J = 8.0 Hz); IR (KBr) m: 3048, 2960, 2920, 2850,
1673, 1642, 1629, 1604, 1488, 1377, 775, 724 cm-1; HRMS calcd for C19H15FO4
(M ? H)?: requires 327.1033, found: 327.1056.
10-(3,4-Dichlorophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4f)
1
Yellow powder, m.p. 198–200 °C; H NMR (CDCl3, 400 MHz) d: 1.97–2.13 (m,
2H, CH2), 2.21 (s, 3H, CH3), 2.32–2.46 (m, 2H, CH2), 2.68–2.89 (m, 2H, CH2), 4.87
(s, 1H, CH), 6.20 (s, 1H, =CH), 7.14 (dd, 1H, ArH, J1 = 2.0 Hz, J2 = 8.0 Hz), 7.34
(d, 1H, ArH, J = 2.0 Hz), 7.38 (d, 1H, ArH, J = 8.4 Hz); IR (KBr) m: 2960, 2920,
1672, 1656, 1641, 1628, 1371, 877, 821 cm-1; HRMS calcd for C19H14Cl2O4
(M ? Na)?: requires 399.0167, found: 399.0188.
10-(2,4-Dichlorophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4g)
White powder, m.p. 200–201 °C; 1H NMR (CDCl3, 400 MHz) d: 1.96–2.13 (m, 2H,
CH2), 2.19 (s, 3H, CH3), 2.32–2.45 (m, 2H, CH2), 2.69–2.88 (m, 2H, CH2), 5.39 (s,
1H, CH), 6.17 (s, 1H, =CH), 7.14 (d, 1H, ArH, J = 8.4 Hz), 7.19 (dd, 1H, ArH,
J1 = 2.0 Hz, J2 = 8.4 Hz), 7.39 (d, 1H, ArH, J = 2.0 Hz); IR (KBr) m: 3059, 2923,
1651, 1606, 1373, 888 cm-1; HRMS calcd for C19H14Cl2O4 (M ? Na)?: requires
399.0167, found: 399.0149.
10-(4-Methylphenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4h)
1
Yellow powder, m.p. 201–202 °C; H NMR (CDCl3, 400 MHz) d: 1.96–2.12 (m,
2H, CH2), 2.19 (s, 3H, CH3), 2.30 (s, 3H, CH3), 2.34–2.44 (m, 2H, CH2), 2.66–2.87
(m, 2H, CH2), 4.87 (s, 1H, CH), 6.17 (s, 1H, =CH), 7.11 (d, 2H, ArH, J = 7.6 Hz),
7.17 (d, 2H, ArH, J = 8.0 Hz); IR (KBr) m: 3034, 2959, 2917, 1672, 1656, 1641,
1627, 1603, 1513, 1373, 859 cm-1; HRMS calcd for C20H18O4 (M ? Na)?:
requires 345.1103, found: 345.1099.
10-(2,3-Dichlorophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4i)
1
Yellow powder, m.p. 226–227 °C; H NMR (CDCl3, 400 MHz) d: 1.96–2.13 (m,
2H, CH2), 2.20 (s, 3H, CH3), 2.34–2.45 (m, 2H, CH2), 2.69–2.90 (m, 2H, CH2), 5.50
(s, 1H, CH), 6.17 (s, 1H, =CH), 7.11–7.18 (m, 2H, ArH), 7.37 (dd, 1H, ArH,
123

Y. Li et al.
J1 = 1.6 Hz, J2 = 7.6 Hz); IR (KBr) m: 3079, 2960, 2921, 2850, 1679, 1643, 1630,
1602, 1452, 1375, 772, 734 cm-1; HRMS calcd for C19H14Cl2O4 (M ? Na)?:
requires 399.0167, found: 399.0157.
10-(3,4-Methylenedioxyphenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4j)
Yellow powder, m.p. 210–212 °C; 1H NMR (CDCl3, 400 MHz) d: 1.98–2.12
(m, 2H, CH2), 2.21 (s, 3H, CH3), 2.31–2.46 (m, 2H, CH2), 2.69–2.90 (m, 2H,
CH2), 4.82 (s, 1H, CH), 5.93 (s, 2H, CH2), 6.18 (s, 1H, =CH), 6.74 (s, 3H,
ArH); IR (KBr) m: 2960, 2886, 1673, 1651, 1636, 1609, 1500, 1380, 790, 815,
886 cm-1; HRMS calcd for C20H16O6 (M ? H)?: requires 353.1025, found:
353.1030.
10-(3-Hydroxyphenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4k)
1
Yellow powder, m.p. 213–215 °C; H NMR (CDCl3, 400 MHz) d: 1.96–2.09 (m,
2H, CH2), 2.21 (s, 3H, CH3), 2.30–2.46 (m, 2H, CH2), 2.63–2.81 (m, 2H, CH2), 4.86
(s, 1H, CH), 6.07 (s, 1H, OH), 6.19 (s, 1H, =CH), 6.73 (dd, 1H, ArH, J1 = 2.4 Hz,
J2 = 8.0 Hz), 6.76 (s, 1H, ArH), 6.84 (d, 1H, ArH, J = 8.0 Hz), 7.17 (t, 1H, ArH,
J = 8.0 Hz); IR (KBr) m: 3193, 2947, 2920, 1670, 1633, 1620, 1603, 1488, 1380,
798, 727 cm-1; HRMS calcd for C19H16O5 (M ? Na)?: requires 347.0895, found:
347.0875.
10-(4-Hydroxyphenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4l)
1
Yellow powder, m.p. 207–209 °C; H NMR (CDCl3, 400 MHz) d: 1.98–2.11 (m,
2H, CH2), 2.20 (s, 3H, CH3), 2.30–2.46 (m, 2H, CH2), 2.66–2.85 (m, 2H, CH2), 4.84
(s, 1H, CH), 5.52 (s, 1H, OH), 6.18 (s, 1H, =CH), 6.75 (d, 2H, ArH, J = 8.4 Hz),
7.13 (d, 2H, ArH, J = 8.4 Hz); IR (KBr) m: 3234, 2960, 2923, 2852, 1673, 1658,
1634, 1611, 1592, 1515, 1377, 830 cm-1; HRMS calcd for C19H16O5 (M ? Na)?:
requires 347.0895, found: 347.0889.
10-(3-Trifluoromethylphenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4m)
White powder, m.p. 211–213 °C; 1H NMR (CDCl3, 400 MHz) d: 1.98–2.13 (m, 2H,
CH2), 2.20 (s, 3H, CH3), 2.32–2.47 (m, 2H, CH2), 2.69–2.90 (m, 2H, CH2), 4.98 (s,
1H, CH), 6.19 (s, 1H, =CH), 7.39–7.53 (m, 4H, ArH); IR (KBr) m: 3080, 2963, 2926,
1668, 1646,1632, 1375, 794, 699 cm-1; HRMS calcd for C20H15F3O4 (M ? Na)?:
requires 399.0820, found: 399.0794.
123

CAN-catalyzed synthesis
10-(2-Chlorophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4n)
1
Yellow powder, m.p. 234–236 °C; H NMR (CDCl3, 400 MHz) d: 1.98–2.13 (m,
2H, CH2), 2.19 (s, 3H, CH3), 2.31–2.44 (m, 2H, CH2), 2.69–2.90 (m, 2H, CH2), 5.45
(s, 1H, CH), 6.17 (s, 1H, =CH), 7.16–7.21 (m, 3H, ArH), 7.37 (d, 1H, ArH,
J = 8.0 Hz); IR (KBr) m: 3061, 2952, 2924, 1678, 1664, 1642, 1628, 1606, 1374,
745 cm-1; HRMS calcd for C19H15ClO4 (M ? Na)?: requires 365.0557, found:
365.0535.
10-(2-Bromophenyl)-7,8-dihydro-2-methylpyrano[3,2-b]chromene-4,9(6H,10H)-
dione (4o)
1
Yellow powder, m.p. 238–240 °C; H NMR (CDCl3, 400 MHz) d: 1.98–2.13 (m,
2H, CH2), 2.19 (s, 3H, CH3), 2.31–2.43 (m, 2H, CH2), 2.70–2.90 (m, 2H, CH2), 5.48
(s, 1H, CH), 6.17 (s, 1H, =CH), 7.08–7.16 (m, 2H, ArH), 7.24 (d, 1H, ArH,
J = 7.6 Hz), 7.57 (d, 1H, ArH, J = 8.0 Hz); IR (KBr) m: 3057, 2959, 2925, 2873,
1675, 1642, 1629, 1600, 1488, 1373, 765 cm-1; HRMS calcd for C19H15BrO4
(M ? Na)?: requires 409.0051, found: 409.0037.
10-(4-Bromophenyl)-7,8-dihydro-2,7,7-trimethylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4p)
White powder, m.p. 213–214 °C; 1H NMR (CDCl3, 400 MHz) d: 1.03 (s, 3H, CH3),
1.11 (s, 3H, CH3), 2.19 (s, 3H, CH3), 2.23–2.28 (m, 2H, CH2), 2.58–2.70 (m, 2H,
CH2), 4.84 (s, 1H, CH), 6.18 (s, 1H, =CH), 7.15 (d, 2H, ArH, J = 8.4 Hz), 7.43 (d,
2H, ArH, J = 8.4 Hz); IR (KBr) m: 3056, 2959, 2923, 2873, 1675, 1642, 1629,
1602, 1488, 1372, 845 cm-1; HRMS calcd for C21H19BrO4 (M ? Na)?: requires
437.0364, found: 437.0346.
10-(4-Hydroxyphenyl)-7,8-dihydro-2,7,7-trimethylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4q)
1
Yellow powder, m.p. 298–300 °C; H NMR (CDCl3, 400 MHz) d: 1.04 (s, 3H,
CH3), 1.11 (s, 3H, CH3), 2.19 (s, 3H, CH3), 2.18–2.29 (m, 2H, CH2), 2.57–2.69 (m,
2H, CH2), 4.81 (s, 1H, CH), 5.78 (s, 1H, OH), 6.18 (s, 1H, =CH), 6.72 (d, 2H, ArH,
J = 8.4 Hz), 7.11 (d. 2H, ArH, J = 8.4 Hz); IR (KBr) m: 3649, 3170, 3023, 2950,
2924, 1672, 1635, 1622, 1591, 1513, 1382, 843 cm-1; HRMS calcd for C21H20O5
(M ? Na)?: requires 375.1208, found: 375.1216.
10-(3,4-Dimethylphenyl)-7,8-dihydro-2,7,7-trimethylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4r)
1
Yellow powder, m.p. 185–186 °C; H NMR (CDCl3, 400 MHz) d: 1.05 (s, 3H,
CH3), 1.11 (s, 3H, CH3), 2.14–2.24 (m, 11H, CH2 ? 3 9 CH3), 2.58–2.71 (m, 2H,
CH2), 4.80 (s, 1H, CH), 6.16 (s, 1H, =CH), 6.95–7.07 (m, 3H, ArH); IR (KBr) m:
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Y. Li et al.
3069, 2956, 2923, 1674, 1658, 1633 1602, 1502, 1374, 881, 828, 670, 652 cm-1
HRMS calcd for C23H24O4 (M ? Na)?: requires 387.1572, found: 387.1600.
;
10-(4-Chlorophenyl)-7,8-dihydro-2,7,7-trimethylpyrano[3,2-b]chromene-
4,9(6H,10H)-dione (4s)
1
Yellow powder, m.p. 203–205 °C; H NMR (CDCl3, 400 MHz) d: 1.04 (s, 3H,
CH3), 1.11 (s, 3H, CH3), 2.19 (s, 3H, CH3), 2.23–2.29 (m, 2H, CH2), 2.58–2.70 (m,
2H, CH2), 4.86 (s, 1H, CH), 6.18 (s, 1H, =CH), 7.21 (d, 2H, ArH, J = 8.0 Hz), 7.28
(d, 2H, ArH, J = 8.4 Hz); IR (KBr) m: 3058, 2960, 2924, 2874, 1678, 1644, 1630,
1603, 1491, 1373, 847 cm-1; HRMS calcd for C21H19ClO4 (M ? Na)?: requires
393.0870, found: 393.0900.
10-(3,4-Methylenedioxyphenyl)-7,8-dihydro-2,7,7-trimethylpyrano[3,2-
b]chromene-4,9(6H,10H)-dione (4t)
1
Yellow powder, m.p. 236–237 °C; H NMR (CDCl3, 400 MHz) d: 1.06 (s, 3H,
CH3), 1.10 (s, 3H, CH3), 2.20 (s, 3H, CH3), 2.20–2.24 (m, 2H, CH2), 2.57–2.70 (m,
2H, CH2), 4.78 (s, 1H, CH), 5.92 (s, 2H, CH2), 6.17 (s, 1H, =CH), 6.72–6.74 (m, 3H,
ArH); IR (KBr) m: 2961, 2932, 1680, 1665, 1635, 1600, 1503, 1378, 854, 824, 797,
659 cm-1; HRMS calcd for C22H20O6 (M ? Na)?: requires 403.1158, found:
403.1180.
Conclusion
In conclusion, we have efficiently synthesized 10-aryl-7,8-dihydropyrano[3,
2-b]chromene-4,9(6H,10H)-diones via CAN-catalyzed three-component reactions
under solvent-free conditions. Low cost, operational simplicity, higher yields
(82–95 %), ready availability of catalyst, an environmentally benign procedure, and
recyclable catalyst make this methodology a useful contribution to existing
procedures available for synthesis of dihydropyrano[3,2-b]chromene-4,9(6H,10H)-
dione derivatives.
Acknowledgments We are grateful to the National Natural Science Foundation of China (no.
21104064, 21172188), the Natural Science Foundation of Xuzhou Normal University (10XLR03,
11XLR13) and the Priority Academic Program Development of Jiangsu Higher Education Institutions for
financial support.
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