A novel and efficient synthesis of bis(benzofuranyl)methanes and 2-benzofuran-1-nitroalkanes catalyzed by Bi(OTf)3

Article abstract of DOI:10.1139/V08-091

Bismuth (III) triflate-catalyzed Friedel-Crafts reactions between benzofuran and aldehydes in different solvents were investigated. Bis(benzofuranyl)methanes were obtained with good yields when acetonitrile was used as solvent, while in the case of nitrom

Full text of DOI:10.1139/V08-091

875
A novel and efficient synthesis of
bis(benzofuranyl)methanes and 2-benzofuran-1-
nitroalkanes catalyzed by Bi(OTf)3
Ren Er Chen, Yan Li Wang, Zhi Wei Chen, and Wei Ke Su
Abstract: Bismuth (III) triflate-catalyzed Friedel–Crafts reactions between benzofuran and aldehydes in different sol-
vents were investigated. Bis(benzofuranyl)methanes were obtained with good yields when acetonitrile was used as sol-
vent, while in the case of nitromethane the multi-component reaction products, 2-benzofuran-1-nitroalkanes, were
formed under similar conditions. A plausible mechanism is given.
Key words: benzofuran, aldehyde, bis(benzofuranyl)methanes, Bi(OTf)3, 2-benzofuran-1-nitroalkane.
Résumé : On a étudié les réactions de Friedel–Crafts catalysées par le triflate de bismuth(III) et effectuées entre le
benzofurane et les aldéhydes dans divers solvants. Avec l’acétonitrile comme solvant, on obtient de bons rendements de
bis(benzofuranyl)méthanes alors que dans le nitrométhane, dans des conditions semblables, il y a formation de 2-benzo-
furane-1-nitroalcanes, des produits qui résultent de réactions entre plusieurs réactifs. On propose un mécanisme plau-
sible.
Mots-clés : benzofurane, aldéhyde, bis(benzofuranyl)méthanes, Bi(OTf)3, 2-benzofurane-1-nitroalcanes.
[Traduit par la Rédaction] Chen et al. 880
Introduction
An effective, convenient, and economic method for the
synthesis of bis(benzofuranyl)methanes was developed. Ad-
ditionally, the first three-component synthetic procedure of
2-benzofuran-1-nitroalkane derivatives are reported here.
The catalyst could be recovered easily after the reactions
and reused without evident loss of activity.
Most natural and synthetic compounds with benzofuran
moieties exhibit broad bioactivities (1, 2) such as antitumor,
antifungal, antivirus activities, 5-lipoxygensase and 5α-
reductase inhibitory activity (3–5). Moreover, they are also
key intermediates for constructing some natural bioactive
quinines (6). Though there are some reports of bis(benzo-
furanyl)methanones (7) and macrocyclic trimer (8), which
were prepared from activated benzofurans, bis(benzo-
furanyl)methanes were only reported in one article (9). In
that article, an environmentally harmful mineral acid was
chosen as catalyst.
Recently, metal triflates have been widely used as Lewis
acids that have low toxicity, low cost, high stability, are easy
to handle and recover from water (10–13). In our ongoing
green chemistry research program, investigating the use of
environmentally friendly reagents, catalysts, and processes
for organic reactions, we wish to study the activities of metal
triflates in catalyzing the Friedel–Crafts alkylation and
multi-component reaction. Herein, we wish to introduce
Bi(OTf)3 as a mild, highly efficient, and environmentally be-
nign catalyst for the preparation of benzofuran derivatives.
Results and discussion
The condensation between benzofuran (2 equiv.) and
benzaldehyde 1a (1 equiv.) in CH3NO2 at refluxing tempera-
ture was used as a model reaction (Scheme 1) for the screen-
ing of a suitable metal triflate catalyst, and the results are
summarized in Table 1. It can be seen that all metal triflates,
with the exception of Mg(OTf)2 and Sr(OTf)2, showed good
catalytic effects. Sc(OTf)3 and Bi(OTf)3 were particularly ef-
fective for this Friedel–Crafts alkylation reaction in short re-
action times (Table 1, entries 1–8). Considering its low cost,
Bi(OTf)3 was chosen as reaction catalyst. The amounts of
metal triflate were also examined in CH3NO2. When Bi(OTf)3
and Sc(OTf)3 were used as catalysts, 1 mol% was enough to
finish the reaction in 1 h. There is no obvious influence on
the yield on increasing the amount of Bi(OTf)3 and Sc(OTf)3
(Table 1, entries 6 and 9).
Solvents such as DMF, CH3CN, EtOH, and PhMe (Ta-
ble 1, entries 10–13) were also tested. Acetonitrile was
found to give maximum yield followed by nitromethane. Re-
action temperature was also explored in CH3CN. No product
was found at room temperature after 3 h. When the reaction
temperature was increased to reflux, the yield was obviously
improved. In light of this, subsequent studies were carried
out under the following optimized conditions: 1 mol%
Bi(OTf)3 at refluxing temperature in CH3CN. In this reac-
Received 31 January 2008. Accepted 1 May 2008. Published
on the NRC Research Press Web site at canjchem.nrc.ca on
8 July 2008.
R.E. Chen, Y.L. Wang, Z.W. Chen, and W.K. Su.1 Key
Laboratory of Pharmaceutical Engineering (Zhejiang
University of Technology), Ministry of Education, College of
Pharmaceutical Sciences, Zhejiang University of Technology,
Hangzhou 310014, P. R. China.
1Corresponding author (e-mail: suweike@zjut.edu.cn).
Can. J. Chem. 86: 875–880 (2008)
doi:10.1139/V08-091
© 2008 NRC Canada

876
Can. J. Chem. Vol. 86, 2008
Scheme 1.
Table 2. The Friedel–Crafts alkylation of benzofuran with alde-
hydes catalyzed by Bi(OTf)3 in CH3CN.
Entry
R
Compound 2
Yield (%)a
1
2
n-C6H5
2a
2b
77, 76, 75, 75b
4-OH-C6H4
65
63
70
70
80
83
81
87
78
78
3
3-CH3O-4-OH-C6H3 2c
4
4-CH3O-C6H4
4-Cl-C6H4
2e
2f
2g
2h
2i
5
6
3-Cl-C6H4
Table 1. The synthesis of bis(benzofuranyl)methanes under dif-
ferent reaction conditions.
7
3-F-C6H4
8
2-F-6-Cl-C6H3
3-NO2-C6H4
3-OH-C6H4
3-Br-C6H4
Entry Catalyst
Solvent
Loading (mol%) Yield (%)a
9
2j
2k
2l
10
11
1
2
Cu(OTf)2
Zn(OTf)2
Mg(OTf)2
Yb(OTf)3
Sc(OTf)3
Sc(OTf)3
Sr(OTf)2
Bi(OTf)3
Bi(OTf)3
Bi(OTf)3
Bi(OTf)3
Bi(OTf)3
Bi(OTf)3
CH3NO2 10
CH3NO2 10
CH3NO2 10
CH3NO2 10
65
55
0
12
13
H
2m
2n
70
73
3
n-C4H9
4
46
75
76
0
14
15
16
17
2-NO2-C6H4
2o
2p
2q
2r
45
38
0
5
CH3NO2
CH3NO2
1
5
2-OH-C6H4
6
2,4-(CH3O)2-C6H3
2-OCH3-C6H5
7
CH3NO2 10
0
8
CH3NO2
CH3NO2
DMFb
CH3CNb
EtOHb
PhMeb
1
5
1
1
1
1
0
76
77
0
Note: Reaction condition: aldehyde (1 mmol), benzofuran (2 mmol),
and Bi(OTf)3 (1 mol%) in acetonitrile at refluxing temperature.
aIsolated yields based on aldehyde.
9
10
11
12
13
14
bCatalyst was reused three times.
77
65
60
0
Scheme 2.
No catalyst CH3CNb
Note: General conditions: benzofuran (2 equiv.), benzaldehyde
(1 equiv), and catalyst (0.01–0.1 equiv.) at 101 °C; reaction time 1.5 h.
aIsolate yields based on benzaldehyde.
bReaction temperature: refluxing temperature.
lytic activity of Bi(OTf)3 was explored for the multi-
component condensation using 4-hydroxybenzaldehyde as
model substrate. 4-Hydroxybenzaldehyde, benzofuran, and
nitromethane were stirred at room temperature for 4 h at the
molar ratio of 1:1:1 in CH3CN. No product was found, as
monitored by TLC. But when it was heated to refluxing tem-
perature, contrary to our expectation, compound 2 were ob-
tained instead of compound 3. We also carried out the
condensation of 4-hydroxybenzaldehyde, benzofuran, and
nitromethane in CH3NO2. Interestingly, compound 3 was
obtained as major product along with compound 2 as minor
product (Table 3, entry 2). To extend the scope of the metal
triflate-catalyzed method for the synthesis of 2-benzofuran-
1-nitroalkane derivatives, we also tried other aldehydes. The
results are summarized in Table 3. It can be seen that this
condensation was only suitable for the aromatic aldehydes
bearing strong electron-donating groups (Table 3, entries 2–5).
A possible mechanism for the formation of bis(benzo-
furanyl)methanes and 2-benzofuran-1-nitroalkane derivatives
is proposed in Scheme 3 (paths A and B). When CH3CN
was used as reaction solvent, intermediate [a] was formed,
which was easily attacked by another benzofuran in the pres-
ence of Bi(OTf)3 (14). Furthermore, the aromatic ring-
bearing electron-withdrawing group was more beneficial to
the formation of compound 2, except for 3-hydroxy-
benzaldehyde. To our surprise, when CH3NO2 is utilized as
reaction media there may exist another reaction mechanism
tion, Bi(OTf)3 could be reused three times without obvious
loss of activity (Table 2, entry 1).
To extend the scope of the metal triflate-catalyzed method
for the synthesis of bis(benzofuranyl)methanes, a series of
aldehydes were investigated (Table 2). Both aromatic and
aliphatic aldehydes were applicable to this reaction, except
for 1q and 1r. The results indicated that a spacial steric ef-
fect had an obvious influence on the reaction (Table 2,
entries 14–17). Furthermore, the substituted groups on the
aromatic ring also had evident influence on the reaction. The
aromatic ring-bearing electron-withdrawing groups only re-
quired short times with high yields, excluding the sterically
hindered 2-nitrobenzaldehyde 1o. The m-substituted
benzaldehyde with electron-withdrawing groups were more
beneficial to the reactions (Table 2, entries 6, 7, 9, and 11).
To our surprise, good yield was also obtained when 3-
hydroxybenzaldehyde was used as substrate (Table 2, entry
10). Considering the good reaction activity of aldehydes,
benzophenone, acetone, and cyclohexanone were chosen as
substrates. Trace reactions took place as indicated by TLC.
The formation of 2-benzofuran-1-nitroalkane derivatives
was discovered serendipitiously. During the preparation of
bis(benzofuranyl)methanes in nitromethane, another product
was detected by TLC and identified as compound 3
1
(Scheme 2) by H NMR, 13C NMR, and MS. Thus, the cata-
© 2008 NRC Canada

Chen et al.
877
Table 3. The synthesis of 2-benzofuran-1-nitroalkane derivatives
catalyzed by Bi(OTf)3 in CH3NO2.
the molar ratio of 1:1 at refluxing temperature, catalyzed by
Bi(OTf)3, gave no product. But when this reaction pro-
ceeded in CH3NO2 at refluxing temperature, a henry product
was obtained with high yield. The aromatic ring-bearing
electron-donating groups were apt for the synthesis of the
henry product. This may be explained because the electron-
donating groups are crucial to the stability of intermediate
[b]. We also tried the condensation of benzofuran and the
henry reaction. Only the aromatic ring-bearing strong
electron-donating groups can react easily, which helped us
explain the result in Table 3.
Entry
1
R
Compound
Yield (%)a
0
n-C6H5
3a
2a
3b
38
83
2
3
4
5
6
7
8
4-OH-C6H4
2b
3c
8
80
3-CH3O-4-OH-C6H3
2,4-(CH3O)2-C6H3
4-CH3O-C6H4
3-Cl-C6H4
2c
3d
7
85
2d
3e
0
82
Conclusion
2e
3g
8
0
In summary, we have developed a simple, convenient, and
efficient synthetic protocol for bis(benzofuranyl)methanes
using a catalytic amount of Bi(OTf)3 in CH3CN. Addi-
tionally, Bi(OTf)3 efficiently promotes three-component cou-
pling reactions of aldehyde, benzofuran, and nitromethane.
The simplicity, efficiency, easy work-up, and the need for
only a small amount of Bi(OTf)3 makes it the preferred
procedure for the preparation of different kinds of 2-
benzofuran-1-nitroalkane derivatives. This class of com-
pounds may be used to construct some bioactive compounds.
2g
3j
40
0
3-NO2-C6H5
2j
3k
43
0
3-OH-C6H4
2k
40
0
36
0
9
H
3m
2m
3n
10
n-C4H9
2n
38
Experimental section2
Note: Reaction condition: aldehyde (1 mmol), benzofuran (1 mmol),
and Bi(OTf)3 (1 mol%) in nitromethane at refluxing temperature.
aIsolated yields based on aldehyde.
General method
All reagents are commercially available. Bismuth(III)
triflate was prepared from triphenylbismuth and triflic acid
(15). Melting points were measured on a digital melting
Scheme 3.
1
point apparatus WR-1B and were uncorrected. H NMR and
13C NMR spectra were recorded on a Varian 400 MHz or
Bruker Anance III (500 MHz) instrument using CDCl3 as
the solvent, and chemical shifts were expressed in parts per
million (ppm) using TMS as an internal standard. Mass
spectra were measured with a Trace Finnigan DSQ. High-
resolution mass spectral (HRMS) analyses were measured
on an Agilent 6210 TOF LC/MS using APCI and EI
(electrospray ionization) techniques. IR measurements were
carried out with a Nicolet Aviatar-370 instrument. Elemental
analysis was performed on a VarioEL-III instrument. All
spectral data of the products were identical to authentic sam-
ples.
General procedure for the preparation of
bis(benzofuranyl)methanes
A
mixture of benzofuran (2 mmol), benzaldehyde
(1 mmol), and Bi(OTf)3 (0.01 mmol) in CH3CN (1 mL) was
heated at refluxing temperature for 1 h. Then water was
added, and the mixture was extracted with ethyl acetate (3 ×
10 mL). The combined organic phases were dried over
Na2SO4 and concentrated under reduced pressure. The crude
product was purified by flash chromatography (silica gel,
petroleum ether / methylene chloride v/v 16:1) to afford the
adduct. The aqueous layer was washed by ethyl acetate and
concentrated in vacuo to give white crystals [Bi(OTf)3],
(path B). Compound 3 was synthesized via two possible
processes. Intermediate [b] was attacked by benzofuran to
obtain the Michael adduct 3. Intermediate [c] suffered a
nucleophilic attack by benzofuran to give compound 3. We
predicted the mechanism by performing the following reac-
tions. The condensation of 1 and nitromethane in CH3CN at
2 Supplementary data for this article are available on the journal Web site (canjchem.nrc.ca) or may be purchased from the Depository of Un-
published Data, Document Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0R6, Canada. DUD 3773. For more in-
formation on obtaining material refer to cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml.
© 2008 NRC Canada

878
Can. J. Chem. Vol. 86, 2008
which was finally heated at 180 °C for 48 h in vacuo to af-
ford Bi(OTf)3 as a colorless crystal.
247 (48). HRMS (APCI) calcd. for (M – 1) C24H18O4:
369.1127; found: 369.1130.
3c
General procedure for the preparation of 2-benzofuran-
1-nitroalkane derivatives
Yellow crystal, mp 83.5–84.2 °C. IR (KBr, cm–1) νmax
:
1
3410, 3130, 1610, 1400, 1253, 746. H NMR (400 MHz,
CDCl3) δ: 7.49 (d, J = 8.4 Hz, 1H, ArH), 7.42 (d, J =
8.0 Hz, 1H, ArH), 7.27–7.18 (m, 2H, ArH), 6.90–6.82 (m,
3H, ArH), 6.49 (s, 1H, furan-H), 5.68 (s, 1H, OH), 5.13–
5.08 (m, 1H, CHNO2), 4.97 (t, J = 7.8 Hz, 1H, CH), 4.88–
4.83 (m, 1H, CHNO2), 3.85 (s, 3H, OCH3). 13C NMR
(100 MHz, CDCl3, ppm) δ: 155.2, 154.9, 146.8, 145.6,
127.9, 127.8, 124.3, 123.0, 122.7, 120.9, 120.8, 114.9,
111.1, 104.3, 77.8, 55.9, 43.6. MS (EI) m/z (%): 313 (14),
266 (100). C17H15NO5: calcd. C 65.17, H 4.83, N 4.47;
found C 65.21, H 4.85, N 4.47.
Bi(OTf)3 (0.01 mmol) was added to a solution of
benzofuran (1 mmol), 4-hydroxybenzaldehyde (1 mmol) in
2 mL of nitromethane. The reaction mixture was stirred at
101 °C for 2 h and then cooled to room temperature. Water
(10 mL) was added and the mixture was extracted with ethyl
acetate (3 × 10 mL). The combined organic phases were
dried over Na2SO4, evaporated, and the crude product was
purified by flash chromatography (silica gel, petroleum ether /
ethyl acetate v/v 4:1) to afford the corresponding products.
The aqueous layer was washed by ethyl acetate and concen-
trated in vacuo to give white crystals [Bi(OTf)3], which was
finally heated at 180 °C for 48 h in vacuo to afford Bi(OTf)3
as a colorless crystal.
3d
Viscous oil. IR (neat, cm–1) νmax: 3130, 2925, 2851, 1613,
1
1554, 1377, 1254, 752. H NMR (400 MHz, CDCl3) δ: 7.49
2a
Viscous oil. IR (neat, cm–1) νmax: 3133, 1637, 1400, 1253,
(d, J = 8.0 Hz, 1H, ArH), 7.42 (d, J = 8.0 Hz, 1H, ArH),
7.27–7.18 (m, 2H, ArH), 7.05 (d, J = 8.8 Hz, 1H, ArH), 6.53
(s, 1H, ArH), 6.49 (s, 1H, furan-H), 6.43 (d, J = 8.0 Hz, 1H,
ArH), 5.42–5.38 (m, 1H, CHNO2), 5.01 (t, J = 7.6 Hz, 1H,
CH), 4.93–4.88 (m, 1H, CHNO2), 3.84 (s, 3H, OCH3), 3.78
(s, 3H, OCH3). 13C NMR (125 MHz, CDCl3, ppm) δ: 160.8,
157.8, 155.4, 154.8, 129.6, 128.2, 124.0, 122.8, 120.8,
116.8, 111.1, 104.6, 104.2, 99.0, 77.3, 55.6, 55.4, 37.6. MS
(EI) m/z (%): 327 (10), 280 (74), 265 (100), 131 (50).
C18H17NO5: calcd. C 66.05, H 5.23, N 4.28; found C 66.10,
H 5.26, N 4.28.
1
748. H NMR (400 MHz, CDCl3) δ: 7.49–7.16 (m, 13H,
ArH), 6.46 (s, 2 H, furan-H), 5.70 (s, 1H, CH). 13C NMR
(100 MHz, CDCl3, ppm) δ: 155.1, 154.3, 138.1, 128.8,
127.7, 127.5, 124.5, 124.1, 123.9, 120.9, 111.3, 105.2, 45.9.
MS (EI) m/z (%): 324 (100), 247 (64). HRMS (EI) calcd. for
C23H16O2: 324.1150; found: 324.1151.
2b
Viscous oil. IR (neat, cm–1) νmax: 3412, 3132, 1614, 1400,
1
1252, 748. H NMR (500 MHz, CDCl3) δ: 7.48 (d, J =
8.0 Hz, 2H, ArH), 7.42 (d, J = 7.5 Hz, 2H, ArH), 7.27–7.17
(m, 6H, ArH), 6.81 (d, J = 7.5 Hz, 2H, ArH), 6.45 (s, 2H,
furan-H), 5.64 (s, 1H, CH), 5.42 (s, 1H, OH). 13C NMR
(125 MHz, CDCl3, ppm) δ: 157.1, 155.3, 155.1, 130.1,
129.9, 128.4, 124.0, 122.8, 120.8, 115.6, 111.2, 105.0, 45.1.
MS (EI) m/z (%): 340 (100), 247 (35). HRMS (APCI) calcd.
for (M – 1) C23H16O3: 339.1021; found: 339.1016.
2e
White crystal. mp 106.9– 107.1 °C. IR (KBr, cm–1) νmax
:
1
3128, 1632, 1400, 1250, 752. H NMR (500 MHz, CDCl3)
δ: 7.48 (d, J = 7.5 Hz, 2H, ArH), 7.47–7.13 (m, 8H, ArH),
6.88 (t, J = 7.5 Hz, 2H, ArH), 6.45 (s, 2H, furan-H), 5.65 (s,
1H, CH), 3.78 (s, 3H, OCH3). 13C NMR (125 MHz, CDCl3,
ppm) δ: 159.2, 157.3, 155.2, 130.3, 129.8, 128.5, 124.1,
122.9, 121.0, 114.3, 111.4, 105.2, 55.3, 45.3. MS (EI) m/z
(%): 354 (100), 247 (20). C24H18O3: calcd. C 81.34, H 5.12;
found C 81.40, H 5.16.
3b
Light yellow crystal, mp 92.8–94.6 °C. IR (KBr, cm–1)
1
ν
max: 3410, 3171, 1614, 1551, 1337, 1210, 749. H NMR
(400 MHz, CDCl3) δ: 7.49 (d, J = 8.0 Hz, 1H, ArH), 7.43
(d, J = 8.4 Hz, 1H, ArH), 7.28–7.18 (m, 4H, ArH), 6.82 (d,
J = 8.8 Hz, 2H, ArH), 6.48 (s, 1H, furan-H), 5.15–5.10 (m,
1H, CHNO2), 5.00 (t, J = 7.6 Hz, 1H, CH), 4.89–4.83 (m,
1H, CHNO2), 1.58 (s, 1H, OH). 13C NMR (100 MHz,
CDCl3, ppm) δ: 155.5, 155.1, 154.9, 129.3, 128.2, 127.9,
124.3, 123.0, 120.9, 116.0, 111.1, 104.3, 77.8, 43.1. MS (EI)
m/z (%): 283 (5), 236 (100). C16H13NO4: calcd. C 67.84, H
4.63, N 4.94; found C 67.89, H 4.70, N 4.94.
3e
Viscous oil. IR (neat, cm–1) νmax: 3130, 2920, 2850, 1615,
1
1550, 1345, 748. H NMR (400 MHz, CDCl3) δ: 7.49 (d,
J = 7.2 Hz, 1H, ArH), 7.43 (d, J = 8.0 Hz, 1H, ArH), 7.31–
7.19 (m, 4H, ArH), 6.90 (d, J = 8.8 Hz, 2H, ArH), 6.48 (s,
1H, furan-H), 5.16–5.11 (m, 1H, CHNO2), 5.01 (t, J =
7.6 Hz, 1H, CH), 4.89–4.84 (m, 1H, CHNO2), 3.80 (s, 3H,
OCH3). 13C NMR (100 MHz, CDCl3, ppm) δ: 155.2, 155.1,
154.7, 129.0, 128.2, 127.9, 124.3, 123.1, 120.8, 115.8,
111.1, 104.3, 77.6, 54.7, 43.1. MS (EI) m/z (%): 297 (15),
250 (100). C17H15NO4: calcd. C 68.68, H 5.09, N 4.71;
found C 68.64, H 5.15, N 4.72.
2c
Viscous oil. IR (neat, cm–1) νmax: 3416, 3132, 1617, 1400,
1
1253, 747. H NMR (500 MHz, CDCl3) δ: 7.49 (d, J =
7.5 Hz, 2H, ArH), 7.42 (d, J = 8.0 Hz, 2H, ArH), 7.28–7.20
(m, 4H, ArH), 6.92–6.87 (m, 3H, ArH), 6.47 (s, 2H, furan-
H), 5.63 (s, 1H, CH), 5.60 (s, 1H, OH), 3.84 (s, 3H, OCH3).
13C NMR (125 MHz, CDCl3, ppm) δ: 157.0, 155.1, 146.7,
145.2, 129.9, 128.3, 124.4, 124.0, 122.8, 121.6, 120.8,
114.6, 111.2, 105.0, 56.0, 45.6. MS (EI) m/z (%): 370 (100),
2f
Viscous oil. IR (neat, cm–1) νmax: 3124, 1637, 1402, 1253,
1
747. H NMR (400 MHz, CDCl3) δ: 7.50–7.21 (m, 12H,
ArH), 6.47 (s, 2H, furan-H), 5.67 (s, 1H, CH). 13C NMR
(100 MHz, CDCl3, ppm) δ: 155.0, 143.6, 136.6, 133.6,
© 2008 NRC Canada

Chen et al.
879
130.0, 129.0, 128.2, 124.2, 122.9, 120.9, 111.3, 105.4, 45.3.
MS (EI) m/z (%): 360 (33), 358 (100), 247 (47).
C23H15ClO2: calcd. C 76.99, H 4.21; found C 76.94, H 4.26.
2l
Viscous oil. IR (neat, cm–1)νmax: 3120, 1615, 1525, 1400,
1
1347, 1250, 745. H NMR (400 MHz, CDCl3) δ: 7.54–7.50
(m, 3H, ArH), 7.46–7.43 (m, 3H, ArH), 7.32 (s, 1H, ArH),
7.28–7.19 (m, 5H, ArH), 6.50 (s, 2H, furan-H), 5.67 (s, 1H,
CH). 13C NMR (100 MHz, CDCl3, ppm) δ: 155.8, 155.1,
140.3, 131.6, 130.9, 130.3, 128.2, 127.3, 124.2, 122.9,
122.8, 120.9, 111.3, 105.4, 45.5. MS (EI) m/z (%): 404 (26),
402 (26), 248 (46), 247 (100). C23H15BrO2: calcd. C 68.50,
H 3.75; found C 68.48, H 3.78.
2g
Viscous oil. IR (neat, cm–1) νmax: 3125, 1632, 1400, 1252,
1
756. H NMR (400 MHz, CDCl3) δ: 7.51 (t, J = 7.0 Hz, 2H,
ArH), 7.43 (t, J = 8.0 Hz, 2H, ArH), 7.37 (s, 1H, ArH),
7.30– 7.23 (m, 5H, ArH), 7.21–7.19 (m, 2H, ArH), 6.50 (s,
2H, furan-H), 5.68 (s, 1H, CH). 13C NMR (100 MHz,
CDCl3, ppm) δ: 155.8, 155.1, 140.0, 134.6, 130.0, 128.8,
128.2, 127.9, 126.9, 124.2, 122.9, 120.9, 111.3, 105.4, 45.5.
MS (EI) m/z (%): 360 (34), 358 (100), 247 (100).
C23H15ClO2: calcd. C 76.99, H 4.21; found C 76.94, H 4.25.
2m
Melting point 70.1–71.2 °C. (lit. value (16) 73–74 °C). IR
(KBr, cm–1) νmax: 3120, 2930, 1600, 1252, 750. H NMR
1
(400 MHz, CDCl3) δ: 7.50–7.18 (m, 8H, ArH), 6.57 (s, 2H,
furan-H), 4.29 (s, 2H, CH2). 13C NMR (100 MHz, CDCl3,
ppm) δ: 154.9, 153.7, 128.6, 123.8, 122.7, 120.6, 111.0,
104.1, 28.4. MS (EI) m/z (%): 248 (100), 247 (80).
2h
Viscous oil. IR (neat, cm–1) νmax: 3123, 1614, 1590, 1400,
1
1253, 748. H NMR (400 MHz, CDCl3) δ: 7.52–7.50 (m,
2H, ArH), 7.44 (d, J = 7.5 Mz, 2H, ArH), 7.35–7.16 (m, 6H,
ArH), 7.12–7.08 (m, 1H, ArH), 7.04–7.02 (m, 1H, ArH),
6.50 (s, 2H, furan-H), 5.71 (s, 1H, CH). 13C NMR
(100 MHz, CDCl3, ppm) δ: 163.0 (J = 250 Hz), 155.9,
155.1, 143.6, 130.3, 130.2, 128.2, 124.3, 122.9, 120.9, 115.7
(J = 22.5 Hz), 114.7 (J = 21.0 Hz), 111.2, 105.3, 45.5. MS
(EI) m/z (%): 342 (98), 247 (100). C23H15FO2: calcd. C
80.69, H 4.42; found C 80.62, H 4.48.
2n
Viscous oil. IR (neat, cm–1) νmax: 3127, 2956, 2928, 2860,
1
1617, 1453, 1400, 1252, 747. H NMR (500 MHz, CDCl3)
δ: 7.57–7.17 (m, 8H, ArH), 6.56 (s, 2H, furan-H), 4.30 (t,
J = 8.0 Hz, 1H), 2.23–2.18 (m, 2H, CH2), 1.39–1.36 (m, 4H,
2 CH2), 0.89 (t, J = 7.0 Hz, 3H, CH3). 13C NMR (125 MHz,
CDCl3, ppm) δ: 157.9, 154.7, 128.6, 123.6, 122.6, 120.6,
111.1, 103.2, 39.8, 32.1, 22.5, 22.4, 13.9. MS (EI) m/z (%):
304 (15), 247 (100). HRMS (EI) calcd. for:
C21H20O2 304.1463; found: 304.1466.
2i
Viscous oil. IR (neat, cm–1) νmax: 3117, 1636, 1400, 1249,
1
745. H NMR (400 MHz, CDCl3) δ: 7.50–7.10 (m, 11H,
ArH), 6.61 (s, 2H, furan-H), 6.34 (s, 1H, CH). 13C NMR
(100 MHz, CDCl3, ppm) δ: 162.0 (J = 250.0 Hz), 154.8,
154.3, 135.4, 129.7, 129.6, 128.4, 125.9, 124.0, 122.8,
120.8, 115.2 (J = 23.7 Hz), 111.2, 104.9, 39.3. MS (EI) m/z
(%): 378 (33), 376 (100), 247 (76). C23H14ClFO2: calcd. C
73.31, H 3.74; found C 73.28, H 3.78.
2o
Viscous oil. IR (neat, cm–1) νmax: 3128, 1617, 1400, 1347,
1
1252, 748. H NMR (500 MHz, CDCl3) δ: 8.06 (d, J =
7.0 Hz, 1H, ArH), 7.59 (t, J = 7.5 Hz, 1H, ArH), 7.53–7.47
(m, 4H, ArH), 7.43 (t, J = 8.0 Hz, 2H, ArH), 7.31–7.27 (m,
2H, ArH), 7.23–7.20 (m, 2H, ArH), 6.63 (s, 1H, ArH), 6.54
(s, 2H, furan-H). 13C NMR (125 MHz, CDCl3, ppm) δ:
155.1, 154.8, 148.5, 133.4, 132.7, 131.3, 128.7, 128.1,
125.3, 124.3, 123.0, 121.1, 111.3, 105.6, 40.8. MS (EI) m/z
(%): 369 (100), 247 (60). C23H15NO4: calcd. C 74.79, H
4.09, N 3.79; found C 74.82, H 4.11, N 3.79.
2j
Viscous oil. IR (neat, cm–1) νmax: 3120, 1616, 1529, 1400,
1
1348, 1252, 747. H NMR (400 MHz, CDCl3) δ: 8.29 (s,
1H, ArH), 8.18 (d, J = 7.2 Hz, 1H, ArH), 7.73 (d, J =
8.8 Hz, 1H, ArH), 7.53 (d, J = 7.6 Hz, 3H, ArH), 7.44 (d,
J = 7.6 Hz, 2H, ArH), 7.29–7.21 (m, 4H, ArH), 6.56 (s, 2H,
furan-H), 5.81 (s, 1H, CH). 13C NMR (100 MHz, CDCl3,
ppm) δ: 155.1, 154.9, 148.5, 140.2, 134.7, 129.7, 128.0,
124.5, 123.7, 123.1, 122.8, 121.1, 111.3, 105.7, 45.5. MS
(EI) m/z (%): 369 (100), 247 (63). C23H15NO4: calcd. C
74.79, H 4.09, N 3.79; found C 74.75, H 4.12, N 3.75.
2p
Viscous oil. IR (neat, cm–1) νmax: 3413, 3130, 1617, 1400,
1
1252, 748. H NMR (500 MHz, CDCl3) δ: 7.49 (d, J =
7.0 Hz, 2H, ArH), 7.43 (t, J = 8.0 Hz, 2H, ArH), 7.26–7.18
(m, 6H, ArH), 6.93 (t, J = 7.5 Hz, 1H, ArH), 6.83 (d, J =
7.0 Hz, 1H, ArH), 6.50 (s, 2H, furan-H), 6.09 (s, 1H, ArH),
5.08 (s, 1H, OH). 13C NMR (125 MHz, CDCl3, ppm) δ:
156.2, 155.1, 153.2, 129.9, 129.0, 128.3, 124.6, 124.0,
122.8, 121.3, 120.8, 116.1, 111.2, 105.2, 39.6. MS (EI) m/z
(%): 340 (100), 247 (45). C23H16O3: calcd. C 81.16, H 4.74;
found C 81.13, H 4.79.
2k
Viscous oil. IR (neat, cm–1) νmax: 3415, 3128, 1630, 1400,
1
1250, 753. H NMR (500 MHz, CDCl3) δ: 7.49 (d, J =
7.5 Hz, 2H, ArH), 7.42 (d, J = 8.0 Hz, 2H, ArH), 7.29–7.17
(m, 5H, ArH), 6.93 (d, J = 7.5 Hz, 1H, ArH), 6.83 (s, 1H,
ArH), 6.82–6.75 (m, 1H, ArH), 6.48 (s, 2H, furan-H), 5.65
(s, 1H, CH), 5.17 (s, 1H, OH). 13C NMR (125 MHz, CDCl3,
ppm) δ: 156.5, 155.9, 155.1, 139.8, 130.0, 128.3, 124.1,
122.8, 121.1, 120.9, 115.6, 114.7, 111.3, 105.2, 45.7. MS
(EI) m/z (%): 340 (100), 247 (40). C23H16O3: calcd. C 81.16,
H 4.74; found C 81.12, H 4.80.
Acknowledgement
We are grateful to the National Natural Science Founda-
tion of China (No. 20676123) for financial support.
© 2008 NRC Canada

880
Can. J. Chem. Vol. 86, 2008
9. A. Bianco, M. Guiso, R.A. Mazzei, and G. Nano. Gazz. Chim.
Ital. 127, 37 (1997).
10. W.K. Su, J.X. Chen, H.Y. Wu, and C. Jin. J. Org. Chem. 72,
4524 (2007).
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