Bismuth triflate, Bi(OTf)3, as an efficient and reusable catalyst for synthesis of dihydropyrano[3,2-b]chromenediones

Article abstract of DOI:10.1007/s13738-014-0514-7

Bi(OTf)₃ was found to be an efficient, reusable and high yielding catalyst for the synthesis of dihydropyrano[3,2-b]chromenediones via the three-component reaction of aromatic aldehydes, kojic acid and 1,3-diones. The catalyst could be separate

Full text of DOI:10.1007/s13738-014-0514-7

J IRAN CHEM SOC
DOI 10.1007/s13738-014-0514-7
ORIgINAl PAPER
Bismuth triflate, Bi(OTf)3, as an efficient and reusable catalyst
for synthesis of dihydropyrano[3,2-b]chromenediones
Sara Pourshahrestani · Iraj Mohammadpoor-Baltork ·
Majid Moghadam · Shahram Tangestaninejad ·
Ahmad R. Khosropour · Valiollah Mirkhani
Received: 1 May 2014 / Accepted: 18 July 2014
© Iranian Chemical Society 2014
Abstract Bi(OTf)3 was found to be an efficient, reus-
able and high yielding catalyst for the synthesis of
dihydropyrano[3,2-b]chromenediones via the three-com-
ponent reaction of aromatic aldehydes, kojic acid and
1,3-diones. The catalyst could be separated and recovered
easily, and was reused for several runs without significant
loss of its activity.
variety of biological activities [7–10]. In spite of a broad
range of application of chromene derivatives, little atten-
tion has been paid to the synthesis of dihydropyrano[3,2-
b]chromenediones using kojic acid and only a few reports
are available dealing with the synthesis of these imperative
heterocycles [11–13]. Consequently, the development of
an efficient and convenient synthetic method of chromene
derivatives using a recyclable and environmentally benign
catalyst is highly desirable.
In recent years, multi-component reactions (MCRs)
have attracted a great deal of interest in organic and medici-
nal chemistry due to the construction of biologically active
compounds with significant structural diversity [14–17].
In fact, these reactions have been recognized as efficient,
fast, economically and environmentally favorable processes
over the complicated stepwise methods [18–20]. There-
fore, the synthesis of heterocyclic compounds of biologi-
cal significance via MCRs has been the spotlight of many
researchers.
During the past years, Bi(III) salts have concerned the
attention of synthetic organic chemists as effective catalysts
because of their low toxicity, ease of handling, low cost and
relative insensitivity to air and moisture [21–26]. Among
the Bi(III) salts, Bi(OTf)3 is the most efficient catalyst, and
particularly pretty because it is commercially available or
can be easily prepared from commercially available start-
ing materials [27–39].
Keywords Chromenediones · Kojic acid · Bismuth
triflate · Multi-component reaction · 1,3-Diones
Introduction
Chromenes are an important class of fused oxygenated
heterocycles which have attracted significant attention due
to their pharmacological and therapeutic properties such
as antibacterial [1], anticancer [2], anti-anaphylactic [3],
and anticonvulsant activities [4]. These heterocyclic com-
pounds have been also used as cognitive enhancers as well
as for the treatment of Alzheimer’s, Parkinson’s, and Hun-
tington’s diseases [5, 6]. Recently, kojic acid (a derivative
of 4-pyrone and as a source of OH-acid) has been used as
a useful component for the synthesis of chromenes. The
compounds containing this inexpensive component have
attracted much synthetic interest, owing to their wide
As a part of our continuing efforts in developing efficient
synthetic methodologies for the preparation of fine chemi-
cals [40–44], we report herein a convenient and highly
efficient protocol for the synthesis of dihydropyrano[3,2-
b]chromenediones via a one-pot, three-component reaction
of aldehydes, kojic acid and dimedone or 1,3-cyclohexan-
edione catalyzed by Bi(OTf)3 under solvent-free conditions
(Scheme 1).
S. Pourshahrestani · I. Mohammadpoor-Baltork (*) ·
M. Moghadam (*) · S. Tangestaninejad · A. R. Khosropour ·
V. Mirkhani
Catalysis Division, Department of Chemistry,
University of Isfahan, 81746-73441 Isfahan, Iran
e-mail: imbaltork@sci.ui.ac.ir
M. Moghadam
e-mail: moghadamm@sci.ui.ac.ir
1 3

J IRAN CHEM SOC
G
O
CHO
O
O
O
O
O
HO
HO
Bi(OTf)3
120 oC, Solvent-free
+
+
R
R
O
OH
G
R
R
O
R = Me, H
4
2
1
3
Scheme 1 Synthesis of dihydropyrano[3,2-b]chromenediones in the presence of Bi(OTf)3 catalyst
Experimental section
(3.18), 243.21 (3.18), 165.43 (5.06), 97.14 (7.18), 55.14
(33.19), 43.30 (71.55).
Melting points were determined with a Stuart Scientific
2-(Hydroxymethyl)-7,7-dimethyl-10-(naphthalen-2-yl)-
7,8-dihydropyrano[3,2-b]chromene-4,9-(6H,10H)-dione
(4j): Mp: 237–239 °C. FT-IR (KBr): νmax = 3,300, 2,955,
SMP2 apparatus. FT-IR spectra were recorded on a Jasco
1
6300D spectrophotometer. H and 13C NMR spectra (400
1
and 100 MHz) were recorded on a Bruker Avance 400 MHz
spectrometer using CDCl3 solvent. Mass spectra were
recorded on a Platform II spectrometer from Micromass; EI
mode at 70 eV.
1,671, 1,639, 1,377, 1,216, 1,195, 1,078, 862 cm−1. H
NMR (400 MHz, CDCl3): δ = 1.06 (s, 3H),1.14 (s, 3H),
1.76 (bs, 1H), 2.25 (AB-q, 2H, J = 16.8 Hz), 2.48 (AB-q,
2H, J = 17.6 Hz), 4.37 (AB-q, 2H, J = 15.6 Hz), 5.08 (s,
1H), 6.53 (s, 1H),7.41 (dd, 1H, J = 8.8, 2.0 Hz), 7.46–7.49
(m, 2H), 7.75–7.82 (m, 3H). 13C NMR (100 MHz, CDCl3):
δ = 27.42, 29.03, 32.30, 38.58, 40.93, 50.42, 60.69, 112.36,
112.43, 125.82, 126.22, 126.40, 127.32, 127.65, 127.94,
128.68, 132.82, 133.32, 137.68, 138.01, 151.56, 163.79,
167.03, 171.21, 196.14. MS: m/z (%): 402.08 ([M]+, 5.15),
384.20 (9.93), 271.78 (6.43), 164.69 (8.82), 127.40 (18.87),
57.05 (91.18), 43.10 (100.00).
general procedure for the synthesis
of dihydropyrano[3,2-b]chromenediones
A mixture of aromatic aldehyde (1 mmol), kojic acid
(1 mmol), 1,3-diones (1 mmol) and Bi(OTf)3 (0.05 mmol)
was stirred at 120 °C for the appropriate time according
to Table 2. The progress of the reaction was monitored
by TlC (eluent: n-hexane–EtOAc, 1:2). After completion
of the reaction, the mixture was cooled to room tempera-
ture, chloroform (10 ml) was added and the catalyst was
separated by simple filtration. The solvent was evapo-
rated and the resulting crude product was purified by
chromatography on silica gel to afford the pure product
(Table 2).
2-(Hydroxymethyl)-7,7-dimethyl-10-(thiophen-2-yl)-
7,8-dihydropyrano[3,2-b]chromene-4,9-(6H,10H)-dione
(4k): Mp: 195–197 °C. FT-IR (KBr): νmax = 3,370, 3,099,
2,955, 1,666, 1,633, 1,376, 1,220, 1,191, 1,073 cm−1
.
1H NMR (400 MHz, CDCl3): δ = 1.13 (s, 3H), 1.15
(s, 3H), 2.14 (bs, 1H), 2.32 (s, 2H), 2.66 (AB-q, 2H,
J = 18.0 Hz),4.48 (AB-q, 2H, J = 16.0 Hz), 5.25 (s, 1H),
6.55 (s, 1H), 6.93 (dd, 1H, J = 4.8, 3.6 Hz), 6.97 (dd, 1H,
J = 3.6, 0.8 Hz), 7.19 (dd, 1H, J = 5.6, 0.8 Hz). 13C NMR
(100 MHz, CDCl3): δ = 27.43, 29.13, 32.21, 33.12, 40.90,
50.40, 60.70, 111.98, 112.42, 125.26, 125.89, 127.12,
137.37, 143.87, 150.40, 164.10, 167.04, 171.12, 196.05.
MS: m/z (%): 358.04 ([M]+, 5.35), 340.05 (5.92), 83.19
(33.88), 57.23 (76.64), 55.21 (100.00).
Characterization data of some representative compounds
10-(3,4-Dimethoxyphenyl)-2-(hydroxymethyl)-7,7-dime-
thyl-7,8-dihydropyrano[3,2-b]chromene-4,9-(6H,10H)-
dione (4h): Mp: 182–184 °C. FT-IR (KBr): νmax = 3,385,
2,959, 1,671, 1,636, 1,613, 1,444, 1,372, 1,213, 1,189,
1,076 cm−1
.
1H NMR (400 MHz, CDCl3): δ = 1.08
2-(Hydroxymethyl-10-phenyl-7,8-dihydropyrano[3,2-
b]chromene-4,9-(6H,10H)-dione (4l): Mp: 182–184 °C.
FT-IR (KBr): νmax = 3,418, 2,927, 1,671, 1,632, 1,377,
1,220, 1,077, 703, 640 cm−1. 1H NMR (400 MHz, CDCl3):
δ = 2.06–2.11 (m, 2H), 2.25 (bs, 1H), 2.34–2.49 (m, 2H),
2.72–2.90 (m, 2H), 4.43 (AB-q, 2H, J = 15.6 Hz), 4.97
(s, 1H), 6.61 (s, 1H), 7.24 (m, 5H). 13C NMR (100 MHz,
CDCl3): δ = 20.24, 27.37, 36.58, 38.35, 60.79, 112.17,
113.52, 127.85, 128.09, 128.88, 137.40, 140.39, 152.37,
(s, 3H),1.14 (s, 3H), 1.54 (bs, 1H), 2.27 (AB-q, 2H,
J = 16.8 Hz), 2.66 (AB-q, 2H, J = 18.0 Hz), 3.85 (s, 3H),
3.86 (s, 3H), 4.42 (AB-q, 2H, J = 15.6 Hz), 4.85 (s, 1H),
6.52 (s, 1H), 6.80 (s, 3H). 13C NMR (100 MHz, CDCl3):
δ = 27.26, 29.16, 32.23, 37.93, 40.89, 50.42, 55.87, 55.95,
60.67, 111.31, 112.19, 112.43, 120.28, 133.17, 137.41,
148.54, 149.09, 151.80, 163.72, 167.42, 171.33, 196.30.
MS: m/z (%): 412.15 ([M]+, 4.58), 303.41 (2.80), 274.00
1 3

J IRAN CHEM SOC
165.50, 167.93, 196.17. MS: m/z (%): 324.05 ([M]+, 3.28),
247.10 (4.31), 128.17 (4.87), 97.22 (10.13), 77.18 (100.00),
55.21 (89.24).
Table 1 Optimization of the conditions for the synthesis of 4b
Entry Catalyst (mol %)
Temp (oC) Time (min) Yield (%)a
1
No catalyst
120
120
120
120
120
120
20
20
20
20
20
20
20
20
20
20
20
10
55
35
30
45
60
91
80
91
45
60
78
2-(Hydroxymethyl)-10-(3-nitrophenyl)-7,8-
dihydroxypyrano[3,2-b]chromene-4,9-(6H,10H)-dione
(4m): Mp: 210–212 °C. FT-IR (KBr): νmax = 3,352, 3,060,
2,944, 1,671, 1,626, 1,595, 1,528, 1,441, 1,378, 1,349,
1,223, 1,062 cm−1. 1H NMR (400 MHz, CDCl3): δ = 2.01–
2.19 (m, 2H), 2.36–2.48 (m, 2H), 2.63 (t, 1H, J = 6 Hz),
2.73–2.95 (m, 2H), 4.38 (dd, 1H, J = 15.6, 5.6 Hz), 4.45
(dd, 1H, J = 18.0, 6.0 Hz), 5.08 (s, 1H), 6.54 (s, 1H), 7.50–
7.55 (m, 1H), 7.65–7.68 (m, 1H), 8.12–8.15 (m, 2H). 13C
NMR (100 MHz, CDCl3): δ = 20.21, 27.39, 36.47, 38.24,
60.68, 112.53, 112.70, 122.95, 123.07, 129.79, 134.32,
142.49, 148.58, 149.93, 166.29, 166.88, 170.98, 196.16.
MS: m/z (%): 369.08 ([M]+, 65.49), 351.07 (50.20), 323.08
(56.86), 247.06 (86.67), 152.08 (58.04), 77.05 (90.98),
54.85 (100.00).
2
H3PW12O40 (5)
ZnCl2 (5)
3
4
ZrOCl2·8H2O (5)
BiCl3 (5)
5
6
Bi(NO3)3·5H2O (5) 120
7
Bi(OTf)3 (5)
Bi(OTf)3 (4)
Bi(OTf)3 (6)
Bi(OTf)3 (5)
Bi(OTf)3 (5)
Bi(OTf)3 (5)
120
120
120
80
8
9
10
11
12
100
110
a
Isolated yield
10-(4-Chlorophenyl)-2-(hydroxymethyl-7,8-
dihydropyrano[3,2-b]chromene-4,9-(6H,10H)-dione (4n):
Mp: 183–185 °C. FT-IR (KBr): νmax = 3,525, 3,085, 2,949,
38.20, 40.41, 49.84, 60.11, 111.24, 111.88, 127.32, 128.40,
135.31, 137.30, 146.54, 149.99, 163.73, 166.68, 170.49,
191.15, 195.54.
1
1,669, 1,636, 1,602, 1,488, 1,215, 1,174, 864 cm−1. H
NMR (400 MHz, CDCl3): δ = 1.59 (bs, 1H), 1.91–2.05
(m, 2H), 2.23–2.38 (m, 2H), 2.60–2.80 (m, 2H), 4.31
(AB-q, 2H, J = 15.6 Hz), 4.82 (s, 1H), 6.43 (s, 1H), 7.13
(d, 2H, J = 8.4 Hz), 7.20 (d, 2H, J = 6.8 Hz). 13C NMR
(100 MHz, CDCl3): δ = 19.72, 26.83, 36.03, 37.27, 60.12,
111.83, 112.69, 128.51, 128.94, 133.21, 137.04, 138.51,
150.60, 165.25, 166.89, 170.65, 195.80. MS: m/z (%):
358.26 ([M]+, 12.20), 322.60 (13.78), 247.16 (18.17),
110.72 (100.00), 54.89 (95.12).
Results and discussion
To optimize the reaction conditions, the reaction of
4-chlorobenzaldehyde, kojic acid and dimedone was first
examined in the absence of the catalyst at 120 °C under
solvent-free conditions and the product was obtained in
only 10 % yield after 120 min (Table 1, entry 1). Then,
the catalytic activity of some protic and lewis acid cata-
lysts such as H3PW12O40, ZnCl2, ZrOCl2·8H2O, BiCl3,
Bi(NO3)3·5H2O, and Bi(OTf)3 (5 mol %) (Table 1, entries
2–7) was investigated and the results showed that Bi(OTf)3
is the most effective catalyst for the synthesis of desired
dihydropyrano[3,2-b]chromenedione 4b (Table 1, entry
7). The effect of amount of the catalyst on the yield of
the product was subsequently examined using 4–6 mol %
of Bi(OTf)3 (Table 1, entries 7–9) and it was found that
5 mol % of the catalyst is optimal to carry out the reaction
efficiently (Table 1, entry 7). The effect of temperature on
this transformation was also studied, and the results dem-
onstrated that 120 °C is the optimum temperature (Table 1,
entries 7, 10–12). Thus, the best yield was achieved on
employing 5 mol % of Bi(OTf)3 at 120 °C under solvent-
free conditions.
2-(Hydroxymethyl)-10-(4-methoxyphenyl)-7,8-
dihydropyrano[3,2-b]chromene-4,9-(6H,10H)-dione (4o):
Mp: 180–182 °C. FT-IR (KBr): νmax = 3,299, 2,896, 1,671,
1
1,637, 1,602, 1,439, 1,367, 1,203, 1,069, 834 cm−1. H
NMR (400 MHz, CDCl3): δ = 1.73 (bs, 1H), 1.97–2.13 (m,
2H), 2.31–2.45 (m, 2H), 2.67–2.88 (m, 2H), 3.80 (s, 3H),
4.41 (AB-q, 2H, J = 16.0 Hz), 4.87 (s, 1H), 6.51 (s, 1H),
6.83 (d, 2H, J = 8.8 Hz), 7.18 (d, 2H, J = 8.4 Hz). 13C
NMR (100 MHz, CDCl3): δ = 20.26, 27.32, 36.60, 37.41,
55.27, 60.65, 112.18, 113.67, 114.19, 129.10, 132.75,
137.37, 151.96, 159.07, 165.45, 167.45, 171.32, 196.46.
MS: m/z (%): 354.64 ([M]+, 13.43), 335.01 (27.84), 307.16
(27.84), 246.68 (100.00), 127.04 (20.98), 76.98 (56.08),
55.03 (59.61).
4-(2-(Hydroxymethyl)-7,7-dimethyl-4,9-dioxo-
4,6,7,8,9,10-hexahydropyrano[3,2-b]chromen-10-yl)
To substantiate the synthetic scope and the generality
of the present protocol, a variety of aldehydes were used
in this reaction and the results are shown in Table 2. Aro-
matic aldehydes carrying either electron donating or elec-
tron withdrawing groups reacted efficiently with kojic acid
and dimedone, affording high yields of the corresponding
dihydropyrano[3,2-b]chromenediones (Table 2, entries 1–10).
1
benzaldehyde(4p): Mp: 218–220 °C. H NMR (400 MHz,
CDCl3): δ = 0.97 (s, 3H), 1.06 (s, 3H), 2.18 (AB-q, 2H,
J = 16.0 Hz), 2.57 (AB-q, 2H, J = 15.6 Hz), 4.32 (AB-
q, 2H, J = 16.0 Hz), 4.92 (s, 1H), 6.45 (s, 1H), 7.39 (d,
2H, J = 8.0 Hz), 7.76 (d, 2H, J = 8.0 Hz), 9.90 (s, 1H).
13C NMR (100 MHz, CDCl3): δ = 26.95, 28.45, 31.82,
1 3

J IRAN CHEM SOC
Table 2 Synthesis of
dihydropyrano[3,2-
b]chromenediones catalyzed
by Bi(OTf)3 under solvent-free
conditions
Entry Aldehyde
Diketone
Product
Time (min) Yield (%)a
Mp/oC (Lit)
O
O
O
O
187-189
(186-188 [11])
O
O
1
20
90
H
HO
O
4a
Cl
O
203-205
(205-206 [12])
O
O
O
H
2
20
91
O
HO
Cl
O
4b
O
Cl
O
Cl
O
O
O
Cl
168-170
(166-167 [12])
H
3
20
94
O
HO
Cl
O
4c
O
O
Cl
O
O
Cl
O
214-216
(216-217 [12])
O
4
5
H
20
20
90
95
HO
O
4d
O
NO2
O
O
O
O
213-215
(212-213 [13])
NO2
H
O
O
HO
O
4e
NO2
O
O
O
227-229
(229-230 [13])
O
H
6
20
92
O
O
HO
NO2
O
4f
CH3
O
O
O
214-216
(214-215 [12])
O
H
7
8
9
25
88
O
HO
CH3
O
4g
O
OCH3
OCH3
O
O
O
O
OCH3
H
182-184
25
30
90
87
O
O
OCH3
HO
O
4h
OMe
O
O
O
177-179
(178-179 [12])
H
O
O
OCH3
HO
O
4i
O
O
O
O
O
H
10
45
85
237-239
O
HO
O
4j
O
1 3

J IRAN CHEM SOC
Table 2 continued
Entry Aldehyde
Diketone
Product
Time (min) Yield (%)a
Mp/oC (Lit)
195-197
S
O
O
O
O
S
O
O
11
40
20
20
92
90
94
HO
HO
HO
H
O
4k
O
O
O
O
182-184
210-212
O
12
13
H
H
O
4l
O
NO2
O
O
O
O
NO2
O
O
O
4m
Cl
O
O
O
O
H
14
20
92
183-185
180-182
O
HO
Cl
O
4n
O
OCH3
O
O
O
H
O
15
30
85
O
O
OCH3
HO
O
4o
a
Isolated yield
CHO
O
CHO
CHO
O
O
O
HO
Bi(OTf)3 (0.05 mmol)
Solvent-free, 120 oC
50 min
O
O
HO
OH
O
O
4p
1 mmol
2 mmol
1 mmol
1 mmol
1 mmol
2 mmol
85%
87%
Scheme 2 Selective synthesis of mono-dihydropyrano[3,2-b]chromenedione by the reaction of terephthalaldehyde with kojic acid and dime-
done catalyzed by Bi(OTf)3
Acid-sensitive aldehyde such as thiophene-2-carbalde-
hyde also displayed good reactivity and gave the desired
product in 92 % yield (Table 2, entry 11). Furthermore,
the present methodology has been used successfully with
cyclohexane-1,3-dione in place of dimedone, provided
the corresponding dihydropyrano[3,2-b]chromenediones
in high yields under the same conditions (Table 2, entries
12–15).
It is interesting to note that excellent selectivity was
observed in the reaction of terephthalaldehyde with kojic
acid and dimedone, the results of which are shown in
Scheme 2. As it is seen, only one formyl group partici-
pated and the corresponding mono-dihydropyrano[3,2-
b]chromenedione 4p was obtained in high yield with
excellent selectivity. It is also noteworthy that no bis-
dihydropyrano[3,2-b]chromenedione was observed even
1 3

J IRAN CHEM SOC
Table 3 Comparison of the results obtained by Bi(OTf)3 with some of those reported by other reagents
Entry
Product
Catalyst (mmol)
Time (min)
Yield (%)
TOF (h−1
)
Cl
1
2
3
CeCl3·7H2O/SiO2 (0.05 mmol) [12]
KAl(SO4)2·12H2O (0.1 mmol) [13]
Bi(OTf)3 (0.05 mmol)
40
50
20
90
91
94
27.0
10.9
56.4
O
Cl
O
HO
O
4c
O
NO2
O
4
5
6
CeCl3·7H2O/SiO2 (0.05 mmol) [12]
KAl(SO4)2·12H2O (0.1 mmol) [13]
Bi(OTf)3 (0.05 mmol)
30
45
20
96
95
95
38.4
12.7
57.0
O
O
HO
O
4e
OMe
7
InCl3 (0.1 mmol) [11]
95
45
70
30
85
88
87
87
5.4
23.5
7.5
8
CeCl3·7H2O/SiO2 (0.05 mmol) [12]
KAl(SO4)2·12H2O (0.1 mmol) [13]
Bi(OTf)3 (0.05 mmol)
9
O
10
34.8
O
O
HO
O
4i
O
O
Bi(OTf)3
O
R
R
R
O
R
HO
Ar
H
3
6
5
Bi(OTf)3
ArCHO
1
O
Bi(OTf)3
Ar
R
R
O
7
Ar
O
O
O
O
HO
HO
R
Ar
O
H
OH
R
O
O
4
O
HO
R
R
2
O
OH
O
8
Bi(OTf)3
Scheme 3 Plausible mechanism for the Bi(OTf)3-catalyzed synthesis of dihydropyrano[3,2-b]chromenediones
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J IRAN CHEM SOC
Table 4 Recycling results of Bi(OTf)
3 catalyst
component reaction of aromatic aldehydes, kojic acid and
1,3-diones catalyzed by Bi(OTf)3 under solvent-free con-
ditions. High yields, short reaction times, simple experi-
mental procedure, high atom-economy, and the use of eco-
friendly and recyclable catalyst are the important features
of this new method in the synthesis of these important het-
erocyclic compounds.
Run
Cycle
Yield (%)a
1
2
3
4
5
0
1
2
3
4
91
90
89
86
82
Acknowledgments The authors are grateful to the Research Coun-
cil of the University of Isfahan for financial support of this work.
Reaction conditions: 4-chlorobenzaldehyde (1 mmol), kojic acid
(1 mmol), dimedone (1 mmol), Bi(OTf)3, (0.05 mmol) at 120 °C for
20 min
a
Isolated yield
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