Acid-promoted furan annulation and aromatization: An access to benzo[b]furan derivatives

Article abstract of DOI:10.1016/j.tet.2017.11.049

An unprecedented PTSA-promoted furan annulation and aromatization in one pot has been developed. This process offers a simple and efficient synthetic route for the construction of various highly substituted benzo[b]furan derivatives, which are widely used not only in drug active molecules but also organic semiconductor and organic light-emitting devices. The preliminary mechanism study indicated this transformation proceeded sequentially via furan annulation and aromatization.

Full text of DOI:10.1016/j.tet.2017.11.049

Accepted Manuscript
Acid-promoted furan annulation and aromatization: An access to benzo[b]furan
derivatives
Jun Ao, Yidong Liu, Shiqi Jia, Lu Xue, Dongmei Li, Yu Tan, Wenling Qin, Hailong Yan
PII:
S0040-4020(17)31208-5
10.1016/j.tet.2017.11.049
TET 29129
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 27 September 2017
Revised Date: 14 November 2017
Accepted Date: 17 November 2017
Please cite this article as: Ao J, Liu Y, Jia S, Xue L, Li D, Tan Y, Qin W, Yan H, Acid-promoted furan
annulation and aromatization: An access to benzo[b]furan derivatives, Tetrahedron (2018), doi: 10.1016/
j.tet.2017.11.049.
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ACCEPTED MANUSCRIPT
Graphical Abstract
An unprecedented PTSA-promoted furan annulation and aromatization in one pot has been developed. This process offers a
simple and efficient synthetic route for the construction of various highly substituted benzo[b]furan derivatives, which are
widely used not only in drug active molecules but also organic semiconductor and organic light-emitting devices. The
Acid-Promoted Furan Annulation and
Aromatization: An Access to Benzo[b]furan
Derivatives
Leave this area blank for abstract info.
Jun Aoa, Yidong Liua, Shiqi Jiaa, Lu Xuea, Dongmei Lia, Yu Tana, Wenling Qina* and Hailong Yana*
aChongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical
Sciences, Chongqing University, Chongqing 401331, P. R. China.
preliminary mechanism study indicated this transformation proceeded sequentially via furan annulation and aromatization.

ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Acid-promoted furan annulation and aromatization: an access to benzo[b]furan
derivatives
Jun Aoa, Yidong Liua, Shiqi Jiaa, Lu Xuea, Dongmei Lia, Yu Tana, Wenling Qina* and Hailong Yana*
a Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University,
Chongqing 401331, P. R. China.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
An unprecedented PTSA-promoted furan annulation and aromatization in one pot has been
developed. This process offers a simple and efficient synthetic route for the construction of
various highly substituted benzo[b]furan derivatives, which are widely used not only in drug
active molecules but also organic semiconductor and organic light-emitting devices. The
preliminary mechanism study indicated this transformation proceeded sequentially via furan
annulation and aromatization.
Available online
Keywords:
2017 Elsevier Ltd. All rights reserved
.
Organocatalysis
Benzo[b]furans
Furan annulation
Aromatization
Polycyclic compounds
OH
Me
OH
OMe
OMe
1. Introduction
MeO
OH
In an ongoing program by our research group, it is required to
synthesize α,β-unsaturated 1,4 di-ketone
O
O
MeO
A (Scheme 1).
Vignafuran
HO
Stemofuran E
Theoretically, the required compound A can be easily obtained
via an aldol type reaction between 3,4-dihydronaphthalen-1(2H)-
one and benzil, subsequent dehydration under acidic reaction
conditions.1 However, under these reaction conditions, compound
A was formed in a relatively low yield along with the formation
of an unexpected benzo[b]furan derivative 2b. To the best of our
knowledge, such a reaction of substrate 1b to form highly
substituted benzo[b]furans under acidic conditions has not been
reported. These types of substituted benzo[b]furans are privileged
structures found in numerous natural products and biologically
active compounds,2 such as vignafuran, stemofuran E, fuliginosin
A, and 1,3-dimethoxy-4,6-dimethylnaphthofuran et al. (Figure 1).
As a result, there is considerable interest from the synthetic
organic community to access benzo[b]furan motifs by efficient
methodologies, and indeed, various synthetically viable strategies
O
OH
O
OH
O
OH
O
OHC
1,3-Dimethoxy-4,6-
dimethylnaphthofuran
Fuliginosin A
Figure 1. Representative benzo[b]furan-containing natural
products.
have been devised for the construction of benzo[b]furan and its
derivatives.3 Some of the conceptually distinct synthetic
strategies toward benzo[b]furans are shown in Scheme 2. There
are two common ways for the construction of these bicyclic
motifs. One of the most explored methods for this purpose is the
annulation of the furan ring starting from poly-substituted
benzene derivatives through Lewis acid-catalyzed condensation4
or transition metal-catalyzed oxidative cyclization.5 Another
possible way, for constructing the benzene portion of
benzo[b]furan via benzannulation of furan derivatives has been
recently realized via Ru-catalyzed carbonylative benzannulation
by Tang and co-workers.6 Despite these achievements, the
limitations of the preparation of benzo[b]furan derivatives still
exist. For example, multicomponent catalyst systems,
requirement of high temperature and a large excess of reagents et
al. As inexpensive and metal-free alternatives, organocatalytic
Scheme 1. Unexpected formation of benzo[b]furan motif.
Corresponding author. Wenling Qin; e-mail: wenling.qin@cqu.edu.cn;
Corresponding author. Hailong Yan; e-mail: yhl198151@cqu.edu.cn.

2
Tetrahedron
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Table 2. Substrate scope.a
R2
O
O
R3
R2
OH
O
120 mol% PTSA
R3
R1
R1
CH2Cl2, 40 oC, 24 h
1
2
2b
2c
2d
2e
, R1 = H, 98%
R
R
R
1 = 8-Br, 99%
,
,
,
1 = 8-Cl, 99%
1 = 6-Br, 99%
2f R1 = 7-Br, 99%
O
O
,
9
2g
, R1 = 7-Cl, 99%
8
R1
2h
, R1 = 7-OMe, 45%
2i
2j
2k
,
R1 = 8-OMe, 92%
R1 = 6-OMe, 99%
R1 = 6-OH, 87%
7
6
Scheme 2. Strategies toward benzo[b]furans.
,
,
2a
, 89%
methods7 for the synthesis of furan derivatives have recently
attracted great interest. Great achievements have been made in
this field through phosphine-mediated reactions.8 However; the
synthetic potential of this strategy is limited to the synthesis of
benzo[b]furan derivatives. Organocatalytic construction of
benzo[b]furan and their derivatives via furan annulation and
aromatization in one pot, to our surprise, has remained elusive
MeO
O
O
Cl
OMe
2l,
2m
90%
CCDC 1554632
Cl
, 93%
Br
F
2. Results and discussion
Table 1. Optimization of the reaction conditions.a
O
O
O
9
9
8
R1
8
R1
F
Br
Cl
7
7
6
6
2n, R1 = H, 99%
2o
2r,
R1 = H, 99%
,
R1 = 8-Br, 99%
2p, R1 = 8-OMe, 92%
2q
2u,
2s,
97%
R1 = 8-OMe, 99%
2t, R1 = 6-OMe, 99%
,
R1 = 6-OMe, 99%
a
Reaction conditions: 1 (0.1 mmol) and PTSA (120 mol%) in CH2Cl2 (1.5
Solvent
(1.5 mL)
CH2Cl2
Yield
(%)b
mL) at 40 °C for 24 h. Isolated yield.
Entry
T(°C)
Acid (mol%)
until now. We report herein our recent studies towards such
process. Moreover, the synthetic process we report herein
proceeds efficiently at mild conditions.
1
2
3
4
5
6
40
40
40
40
40
40
boric acid (120)
NR
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
citric acid (120)
NR
NR
NR
NR
NR
Considering the strategies applicable to our goal as well as
atomic economy and operating simplicity, we prepared
compound 1b as the model substrate to optimize the reaction
conditions. We envisaged that, in an acidic circumstance, 1b
could be dehydrated and then underwent a furan annulation and
aromatization in one pot to form benzo[b]furan. In order to find
the better reaction conditions, as shown in Table 1, firstly, the
effect of organic acid on the reaction outcome was investigated
with an acid loading of 120 mol% in CH2Cl2 (entries 1-8).
Among these tested acids, benzene sulfonic acid and p-
toluenesulfonic acid (PTSA) were found to be the best in term of
yield (Table 1, entries 7 and 8) in this benzo[b]furan formation
reaction. However other organic acids (Table 1, entries 1-6), such
as boric acid, benzoic acid, and cinnamic acid did not work at all
for this transformation. Although the benzene sulfonic acid and
p-toluenesulfonic acid (PTSA) showed the almost similar
performance, considering more facile commercial availability,
PTSA was chosen as the best catalyst for the further condition
optimization. The influence of the loading amount of PTSA
(entries 9-11) was also studied. The yields of 2b were gradually
decreased with the decrease in the dosage of PTSA. When 10
mol% PTSA was used, only a trace amount of product could be
detected. In further experiments, different solvents were
examined (entries 12-15). CH2Cl2 was proved to be the optimal
choice. Polar solvents such as THF was proved to be the much
worse solvent for this reaction (entry 12). Finally, we performed
cinnamic acid (120)
malonic acid (120)
benzoic acid (120)
formic acid (120)
benzene sulfonic acid
7
40
CH2Cl2
95
(120)
8
40
40
40
40
40
40
40
40
25
50
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
THF
PTSA (120)
PTSA (100)
PTSA (50)
PTSA (10)
PTSA (120)
PTSA (120)
PTSA (120)
PTSA (120)
PTSA (120)
PTSA (120)
98
95
43
7
9
10
11
12
13
14
15
16
17
21
73
89
10
7
toluene
CHCl3
CCl4
CH2Cl2
CH2Cl2
86
a Reaction conditions: 1b (0.1 mmol) and acid in the solvent (1.5 mL) for 24
h. b Isolated yield. NR = no reaction.

Table 3. Substrate scope.a
ACCEPTED MANUSCRIPT
R2
R3
O
O
OH
O
R2
120 mol% PTSA
CH2Cl2, 40 oC, 24 h
R1
R1
R3
3
4
F
MeO
O
O
O
O
F
Cl
OMe
4a, 99%
4b, 99%
Br
4c, 99%
4d, 83%
Scheme 3. Synthesis of polycyclic derivatives containing
benzo[b]furan.
F
in the presence of PTSA, the reaction proceeded smoothly to
afford 2,3-disubstituted benzo[b]furan 4a in the unexceptionable
yield under the same conditions. Based on this delighting result,
we subsequently explored the scope of this transformation to
produce a series of benzo[b]furans under this mild reaction
conditions. First, we tested the influence of substitution group of
R2 and R3. As shown in Table 3, di-para-fluoro substituted
substrate was well tolerated to this transformation and gave
product 4b in the excellent yield. When R3 was para-chloro (4c),
the yield of the reaction was still perfect. Next, we evaluated di-
meta- methoxyl substituted substrate, which leads to the product
4d in wonderful yield as well. Finally, we turned our attention to
test the effect of substitution group R1. No matter what the
substitution groups R2 and R3 were, when the substitution group
at C-6 position was methyl group, the corresponding products 4e-
4j were formed smoothly with high yields. However, when the
R1 substitution group at C-6 position was chlorine, as shown in
Table 3, products 4k and 4l were obtained in a slightly lower
yield because the electron withdrawing nature of chlorine might
lead to the electron deficiency in the formed benzo[b]furan ring
system.
Besides the biological potential of benzo[b]furan derivatives,
polycyclic derivatives containing benzo[b]furan were also widely
used in photoelectricity chemistry. After determining the
substrate scope of the reaction, we were interested in extending
this transformation to photoelectricity area. Polycyclic
dithiophenes containing a furan ring has the potential to be used
as an organic semiconductor in organic electronic devices.9 As
shown in Scheme 3, product 2,3-diphenylthieno[2,3-
g]benzofuran 6 has been formed arising from substrate 5 in the
satisfied yield. Furthermore, as shown in Scheme 3, we also
synthesized a fused heterocyclic ring compound 8 under the same
reaction conditions with a slight modification (see Supporting
Information). Compound 8 has showed the promising prospect in
the field of Organic Light-Emitting Devices (OLED).10
O
O
O
O
Cl
Br
F
4e, 99%
4f, 99%
4g, 99%
4h, 92%
MeO
F
Cl
O
O
O
O
F
Cl
Cl
Cl
OMe
4i, 89%
4j, 92%
4k, 70%
4l, 80%
a
Reaction conditions: 3 (0.1 mmol) and PTSA (120 mol%) in CH2Cl2 (1.5
mL) at 40 °C for 24 h. Isolated yield.
the reaction at different temperatures. Both the decrease and the
increase in the reaction temperature affected the yield of the
reaction, and 40 C was demonstrated to be the most suitable
o
reaction temperature.
With the optimized reaction condition in hand, we next turned
our attention to the substrate scope of this transformation. First,
product 2a was successfully formed with good yield from
substrate 1a. Then, the scope of substitution on 3,4-
dihydronaphthalen-1(2H)-one was investigated under the optimal
conditions. Various substituents at different positions on the aryl
rings were well tolerated. When R1 were halogen substituents,
products 2c-2g were formed with high yields and different
positions of halogen substituent did not influence the yield of the
reaction. However, when R1 was shifted to 7-methoxyl group, the
yield decreased dramatically (2h). Surprisingly, when methoxyl
group entered the C-8 or C-6 position, the yields respectively
reached to 92% (2i) and 99% (2j), even with the hydroxyl group,
the yield was still high (2k). Next, we turned our attention to
examine the influence of the electricity nature and the regio
effect of substitution groups R2 and R3. When R3 group was
para-chloro substitution, the reaction also gave the excellent
yield (2l). The structure of 2l was confirmed by X-ray analysis.
When R2 and R3 were meta-methoxyl group, a perfect yield of
the reaction was obtained (2m). When R2 and R3 groups were
para-fluoro substitutions, a series of R1 groups including 8-
bromo (2o), 8-methoxyl (2p), and 6-methoxyl (2q) at different
positions were investigated. All of these products were formed
with excellent yields. This transformation was also enforceable in
the substrates 1r-1u. The nature or position of R1 group on 3,4-
dihydronaphthalen-1(2H)-one had no effect on the yield of the
reaction. The corresponding products (2r-2u) were formed with
excellent yields as well.
Encouraged by these results, we subsequently investigated the
reaction
by
using
6-(1-hydroxy-2-oxo-1,2-
Scheme 4. Mechanism study.
diphenylethyl)cyclohex-2-en-1-one 3a as substrate. Gratifyingly,

4
Tetrahedron
ACCEPTED MANUSCRIPT
4. Experimental section
When monitoring the reaction with thin layer
chromatography (TLC), we found that, at the early stage of the
reaction, two new spotsappeared simultaneously. In the process
of reaction, however, the signals on TLC showed a change in two
different trends. The intermediate spot disappeared in pace with
the increase in final product spot (for details please see
Supplementary data). We envisage that this intermediate may be
the dehydrated product of substrate 1 and can be isolated for
structural identification. As shown in Scheme 4 a, intermediate 9
was isolated and treated under normal reaction conditions.
Subsequently, product 2r was successfully formed in a yield of
99%. Inspirit by this result, we performed a reaction with
catalytic amount (20 mol% ) of acid in the transformation of 9, as
shown in Scheme 4 b, the desired benzo[b]furan derivative was
successfully formed with high yield. This result indicated that our
reaction firstly proceeded via a dehydration process and then
through a cascade furan annulation and aromatization to form
benzo[b]furan derivatives in one pot. Based on the experimental
results and phenomenon, simultaneously inspired by the previous
reports,11 a postulated reaction pathway for this transformation is
depicted in Scheme 5. We assumed that substrate 1b was
converted into intermediate A through dehydration in the
presence of PTSA. Then, intermediate A was protonated by
PTSA, and the protonated B underwent an inner molecular aldol
type reaction to form an acetal D, which was unstable under an
acidic condition and subsequently converted into intermediate E.
Next, intermediate E was then transformed to F through
dehydration. Finally, intermediate F was deprotonated to formed
final product 2b through an aromatization process, meanwhile
the catalytic acid was regenerated, thus close the catalytic cycle.
4.1 General methods
All reagents were obtained from Adamas, Aladin, Accela, or
Acros and used without further purification unless otherwise
noted. The products were purified by column chromatography
1
with Huanghai Silica Gel 50-75 um, ultrapure silica gel. H and
13C NMR spectra were recorded on an Agilent 400MR DD2 (400
MHz) or Agilent 600MR DD2 (600 MHz) spectrometer.
Chemical shifts were reported in parts per million (ppm), and
tetramethylsilane or the residual solvent peak was used as an
1
internal reference. H (tetramethylsilane δ 0.00), 13C (chloroform
δ
77.00). Data are reported as follows: chemical shift,
multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m =
multiplet, br = broad), coupling constants (Hz) and integration.
High resolution mass spectra (HRMS) were performed on Bruker
solarix 7.0T. X-ray crystallography analysis of single crystals
was performed on an Agilent SuperNova-CCD X-Ray
diffractometer. Melting points were measured using SGWX-4A
Microscopic melting point meter and are uncorrected. No melting
points were reported for amorphous solids. All reactions were
carried out under nitrogen atmosphere in oven-dried glassware
with magnetic stirring. Unless otherwise stated, all solvents
employed in the reactions were distilled from appropriate drying
agents prior to use.
4.2 Synthesis of 2-(1-hydroxy-2-oxo-1, 2-diphenylethyl)
cyclohexan-1-ones (1, 3, 5, 7)
A solution of i-Pr2NH (1.3 mL, 9.1 mmol) and n-BuLi (4.9
mL, 1.6 M in hexane) in THF (15 mL) was stirred at 0 ºC for 1.5
h. To this solution was added ketone (5 mmol) in THF (3 mL) at
0 ºC. After stirring for 1 h, Benzil (6.5 mmol) in THF (5 mL) was
added at –78 ºC dropwise via syringe over 0.5 h. After 12 h, the
reaction was quenched with saturated NH4Cl. Products were
extracted with EtOAc. Combined organic layers were washed
with brine, dried over Na2SO4, and concentrated to give a crude
mixture, which was purified by silica gel column
chromatography (eluent: EtOAc / hexane = 1/20) to afford a
white solid. The Characterization data of substrates 1, 3, 5, 7 can
be found in Appendix A. Supplementary data.
4.3 General procedure for the acid-promoted reactions
A flame-dried Schlenk tube equipped with a magnetic stirring
bar, was charged with 1, 3, 5, 7 (0.1 mmol), p-toluenesulfonic
acid (22.8 mg, 0.12 mmol). Dichloromethane (1.5 mL) was
injected into the tube at 40 ºC. After stirring for 24 h, the mixture
was filtered and purified by silica gel chromatography (PE /
EtOAc = 10/1) to afford the product 2, 4, 6, 8.
Scheme 5. Proposed mechanism.
4.4 The Characterization data of products
3. Conclusion
2-phenylnaphtho[1,2-b]furan (2a)
In summary, we developed an efficient organocatalytic
method to access benzo[b]furan derivatives via furan annulation
and aromatization in one pot. According to this metal-free
procedure, a range of highly substituted benzo[b]furan motifs
were synthesized with excellent yields. Notably, we utilized this
method to achieve the preparation of fused ring systems
containing a benzo[b]furan motif which had shown their potential
as photoelectric materials. Based on the experimental results, a
plausible mechanism via furan annulation and aromatization has
been proposed for this transformation. Further detailed
mechanistic studies and applications of this reaction are currently
in progress in our laboratory.
Yellow oil (21.6 mg, yield: 89%). 1H NMR (400 MHz,
CDCl3): δ 8.42 (d, J = 8.3 Hz, 1H), 7.95 (dd, J = 12.0, 8.2 Hz,
3H), 7.68 – 7.59 (m, 3H), 7.49 (q, J = 7.4 Hz, 3H), 7.37 (t, J =
7.8 Hz, 1H), 7.15 (s, 1H). 13C NMR (100 MHz, CDCl3): δ
155.31, 150.30, 131.48, 130.73, 128.80, 128.41, 128.21, 126.32,
125.01, 124.81, 124.65, 123.61, 121.35, 120.01, 119.53, 102.45.
HRMS (ESI): m/z Calcd for [C18H12NaO, M + Na]+: 267.07803,
Found: 267.07792.
2,3-diphenylnaphtho[1,2-b]furan (2b)
White solid (31.4 mg, yield: 98%), m. p. 101–103 ºC. 1H
NMR (400 MHz, CDCl3): δ 8.41 (d, J = 8.1 Hz, 1H), 7.91 (d, J =
8.0 Hz, 1H), 7.73 (d, J = 7.4 Hz, 2H), 7.65 – 7.57 (m, 2H), 7.54
(d, J = 6.7 Hz, 3H), 7.48 (t, J = 7.2 Hz, 3H), 7.44 – 7.38 (m, 1H),

7.37 – 7.24 (m, 3H). 13C NMR (100 MHz, CDCl3): δ 149.98,
(ESI): m/z Calcd for [C25H18NaO2, M + Na]+: 373.12021, Found:
373.11990.
ACCEPTED MANUSCRIPT
149.48, 132.94, 131.72, 130.90, 129.82, 128.97, 128.44, 128.38,
128.04, 127.63, 126.76, 126.36, 125.56, 125.20, 123.58, 121.22,
120.16, 118.79, 118.48. HRMS (ESI): m/z Calcd for
[C24H16NaO, M + Na]+: 343.10959, Found: 343.10934.
8-methoxy-2,3-diphenylnaphtho[1,2-b]furan (2i)
White solid (32.3 mg, yield: 92%), m.p. 145–147 ºC. 1H NMR
(400 MHz, CDCl3): δ 7.81 (d, J = 8.9 Hz, 1H), 7.74 (d, J = 7.4
Hz, 2H), 7.68 (d, J = 1.9 Hz, 1H), 7.60 – 7.52 (m, 3H), 7.48 (t, J
= 7.4 Hz, 2H), 7.44 – 7.37 (m, 2H), 7.37 – 7.25 (m, 3H), 7.14
(dd, J = 8.9, 2.3 Hz, 1H), 4.02 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 158.26, 150.00, 149.13, 132.99, 130.95, 130.04,
129.82, 128.95, 128.44, 128.06, 127.60, 127.00, 126.88, 126.00,
123.34, 122.09, 118.88, 117.56, 115.93, 98.88, 55.53. HRMS
(ESI): m/z Calcd for [C25H18NaO2, M + Na]+: 373.11990, Found:
373.11935.
8-bromo-2,3-diphenylnaphtho[1,2-b]furan (2c)
White solid (39.4 mg, yield: 99%), m.p. 129–131 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.56 (d, J = 1.8 Hz, 1H), 7.79 (d, J = 8.7
Hz, 1H), 7.73 (d, J = 6.7 Hz, 2H), 7.62 – 7.42 (m, 8H), 7.37 –
7.28 (m, 3H). 13C NMR (100 MHz, CDCl3): δ 150.62, 148.28,
132.60, 130.56, 130.06, 129.98, 129.77, 129.03, 128.49, 128.45,
128.30, 127.78, 126.80, 126.48, 123.34, 122.56, 122.14, 120.50,
118.96, 118.72. HRMS (ESI): m/z Calcd for [C24H15BrNaO, M +
Na]+: 421.01985, Found: 421.01963.
6-methoxy-2,3-diphenylnaphtho[1,2-b]furan (2j)
8-chloro-2,3-diphenylnaphtho[1,2-b]furan (2d)
White solid (34.9 mg, yield: 99%), m.p. 155–157 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.09 (d, J = 8.8 Hz, 1H), 8.01 (d, J = 8.3
Hz, 1H), 7.74 (d, J = 7.1 Hz, 2H), 7.60 – 7.45 (m, 6H), 7.42 (t, J
= 7.3 Hz, 1H), 7.36 – 7.22 (m, 3H), 6.87 (d, J = 7.7 Hz, 1H), 4.02
(s, 3H). 13C NMR (100 MHz, CDCl3): δ 156.00, 150.08, 149.48,
132.99, 130.92, 129.84, 128.97, 128.44, 128.05, 127.61, 126.82,
126.69, 126.08, 123.32, 122.18, 118.72, 117.55, 117.49, 112.59,
103.88, 55.56. HRMS (ESI): m/z Calcd for [C25H18NaO2, M +
Na]+: 373.11987, Found: 373.11958.
White solid (35.1 mg, yield: 99%), m.p. 130–132 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.36 (s, 1H), 7.81 (d, J = 8.7 Hz, 1H), 7.71
(d, J = 7.0 Hz, 2H), 7.61 – 7.37 (m, 8H), 7.37 – 7.24 (m, 3H). 13
C
NMR (100 MHz, CDCl3): δ 150.54, 148.43, 132.59, 132.28,
130.55, 129.97, 129.76, 129.02, 128.48, 128.28, 127.76, 126.78,
126.43, 125.92, 123.27, 121.68, 119.30, 118.76, 118.70.HRMS
(ESI): m/z Calcd for [C24H15ClNaO, M + Na]+: 377.07036,
Found: 377.07017.
6-bromo-2,3-diphenylnaphtho[1,2-b]furan (2e)
2,3-diphenylnaphtho[1,2-b]furan-6-ol (2k)
White solid (39.6 mg, yield: 99%), m.p. 167–169 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.42 (d, J = 8.2 Hz, 1H), 8.08 (d, J = 8.9
Hz, 1H), 7.80 (d, J = 7.4 Hz, 1H), 7.74 (d, J = 7.4 Hz, 2H), 7.66
(d, J = 8.9 Hz, 1H), 7.59 – 7.41 (m, 6H), 7.39 – 7.29 (m, 3H). 13C
NMR (100 MHz, CDCl3): δ 150.86, 149.23, 132.53, 130.61,
129.99, 129.76, 129.31, 129.06, 128.50, 128.33, 127.81, 126.86,
126.65, 126.26, 123.46, 122.70, 122.36, 119.97, 119.80, 118.66.
HRMS (ESI): m/z Calcd for [C24H15BrNaO, M + Na]+:
421.01985, Found: 421.01962.
White solid (29.2 mg, yield: 87%), m.p. 156–158 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.00 (t, J = 8.0 Hz, 2H), 7.73 (d, J = 7.4
Hz, 2H), 7.55 (d, J = 7.2 Hz, 3H), 7.51 – 7.39 (m, 4H), 7.37 –
7.25 (m, 3H), 6.83 (d, J = 7.5 Hz, 1H), 5.32 (s, 1H). 13C NMR
(100 MHz, CDCl3): δ 151.99, 150.17, 149.47, 132.88, 130.84,
129.82, 128.98, 128.45, 128.10, 127.65, 126.81, 126.62, 126.09,
122.52, 122.05, 118.77, 117.76, 117.06, 113.05, 108.73. HRMS
(ESI): m/z Calcd for [C24H16NaO2, M + Na]+: 359.10425, Found:
359.10381.
7-bromo-2,3-diphenylnaphtho[1,2-b]furan (2f)
3-(4-chlorophenyl)-2-phenylnaphtho[1,2-b]furan (2l)
White solid (39.3 mg, yield: 99%), m.p. 144–146 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.24 (d, J = 8.7 Hz, 1H), 8.05 (s, 1H), 7.67
(dd, J = 19.0, 8.3 Hz, 3H), 7.57 – 7.38 (m, 7H), 7.35 – 7.24 (m,
3H). 13C NMR (100 MHz, CDCl3): δ 150.40, 149.23, 132.74,
132.59, 130.62, 130.47, 129.76, 129.57, 129.02, 128.48, 128.24,
127.76, 126.77, 125.98, 122.62, 121.87, 119.75, 119.59, 118.99,
118.75. HRMS (ESI): m/z Calcd for [C24H15BrNaO, M + Na]+:
421.02009, Found: 421.01984.
White solid (31.9 mg, yield: 90%), m.p. 138–140 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.39 (d, J = 8.1 Hz, 1H), 7.90 (d, J = 8.1
Hz, 1H), 7.75 – 7.56 (m, 4H), 7.55 – 7.38 (m, 6H), 7.37 – 7.25
(m, 3H). 13C NMR (100 MHz, CDCl3): δ 150.19, 149.54, 133.56,
131.74, 131.44, 131.12, 130.59, 129.27, 128.55, 128.40, 128.28,
126.81, 126.47, 125.33, 125.16, 123.78, 121.18, 120.13, 118.08,
117.54. HRMS (ESI): m/z Calcd for [C24H15ClNaO, M + Na]+:
377.07052, Found: 377.07036.
7-chloro-2,3-diphenylnaphtho[1,2-b]furan (2g)
2,3-bis(3-methoxyphenyl)naphtho[1,2-b]furan (2m)
White solid (35 mg, yield: 99%), m.p. 149–151 ºC. 1H NMR
White solid (35.4 mg, yield: 93%), m.p. 89–91 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.41 (d, J = 8.2 Hz, 1H), 7.91 (d, J = 8.1
Hz, 1H), 7.66 – 7.53 (m, 3H), 7.48 (t, J = 7.4 Hz, 1H), 7.38 (dd, J
= 17.1, 8.7 Hz, 2H), 7.31 (s, 1H), 7.25 – 7.18 (m, 1H), 7.16 –
7.06 (m, 2H), 6.96 (d, J = 8.1 Hz, 1H), 6.83 (d, J = 8.0 Hz, 1H),
3.80 (s, 3H), 3.70 (s, 3H). 13C NMR (100 MHz, CDCl3): δ
160.01, 159.48, 149.78, 149.36, 134.24, 132.01, 131.76, 129.99,
129.48, 128.38, 126.37, 125.53, 125.24, 123.63, 122.31, 121.17,
120.16, 119.23, 118.94, 118.49, 115.18, 114.24, 113.46, 111.73,
55.28, 55.09. HRMS (ESI): m/z Calcd for [C26H20NaO3, M +
Na]+: 403.13047, Found: 403.12997.
(400 MHz, CDCl3): δ 8.32 (d, J = 8.8 Hz, 1H), 7.88 (s, 1H), 7.70
(d, J = 6.8 Hz, 2H), 7.59 – 7.38 (m, 8H), 7.36 – 7.26 (m, 3H). 13
C
NMR (100 MHz, CDCl3): δ 150.36, 149.25, 132.64, 132.37,
130.89, 130.65, 129.77, 129.03, 128.48, 128.23, 127.77, 127.26,
127.11, 126.78, 125.89, 122.69, 121.80, 119.81, 119.42, 118.76.
HRMS (ESI): m/z Calcd for [C24H15ClNaO, M + Na]+:
377.07062, Found: 377.07036.
7-methoxy-2,3-diphenylnaphtho[1,2-b]furan (2h)
White solid (15.8 mg, yield: 45%), m.p. 142–144 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.33 (d, J = 8.6 Hz, 1H), 7.72 (d, J = 7.3
Hz, 2H), 7.55 (t, J = 7.4 Hz, 4H), 7.48 (t, J = 7.8 Hz, 2H), 7.45 –
7.39 (m, 1H), 7.36 – 7.25 (m, 5H), 3.95 (s, 3H). 13C NMR (100
MHz, CDCl3): δ 157.36, 149.89, 149.32, 133.13, 133.08, 131.01,
129.81, 128.95, 128.42, 127.86, 127.58, 126.63, 123.99, 122.61,
121.81, 119.12, 118.72, 118.52, 116.41, 107.24, 55.34. HRMS
2,3-bis(4-fluorophenyl)naphtho[1,2-b]furan (2n)
White solid (35.3 mg, yield: 99%), m.p. 114–116 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.38 (d, J = 8.2 Hz, 1H), 7.91 (d, J = 8.1
Hz, 1H), 7.68 – 7.57 (m, 4H), 7.52 – 7.43 (m, 4H), 7.21 – 7.13
(m, 2H), 7.03 (t, J = 8.7 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ

6
Tetrahedron
ACCEPTED MANUSCRIPT
163.74, 163.61, 161.26, 161.15, 149.38, 149.21, 131.72,
White solid (41.7 mg, yield: 99%), m.p. 123–125 ºC. 1H NMR
131.45, 131.37, 128.61, 128.53, 128.42, 126.94, 126.91, 126.50,
125.34, 123.81, 121.12, 120.06, 118.12, 117.46, 116.28, 116.06,
115.75, 115.54. HRMS (ESI): m/z Calcd for [C24H14F2NaO, M +
Na]+: 379.09049, Found: 379.09011.
(400 MHz, CDCl3): δ 8.13 (d, J = 8.8 Hz, 1H), 7.98 (d, J = 8.2
Hz, 1H), 7.61 – 7.35 (m, 5H), 7.32 – 7.15 (m, 5H), 6.84 (d, J =
7.7 Hz, 1H), 3.98 (s, 3H). 13C NMR (100 MHz, CDCl3): δ
155.95, 150.05, 149.64, 134.19, 133.91, 132.24, 132.16, 131.60,
130.24, 130.13, 129.98, 129.93, 129.13, 126.80, 126.51, 124.76,
123.31, 122.32, 119.10, 118.31, 117.42, 112.52, 104.06, 55.53.
HRMS (ESI): m/z Calcd for [C25H16Cl2NaO2, M + Na]+:
441.04213, Found: 441.04196.
8-bromo-2,3-bis(4-fluorophenyl)naphtho[1,2-b]furan (2o)
White solid (43 mg, yield: 99%), m.p. 169–171 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.49 (s, 1H), 7.75 (d, J = 8.6 Hz, 1H), 7.66
– 7.61 (m, 2H), 7.55 (dd, J = 14.9, 8.7 Hz, 2H), 7.48 – 7.42 (m,
3H), 7.18 (t, J = 8.1 Hz, 2H), 7.03 (t, J = 8.2 Hz, 2H). 13C NMR
(100 MHz, CDCl3): δ 163.92, 163.72, 161.44, 161.25, 149.87,
148.22, 131.45, 131.37, 130.10, 130.02, 128.70, 128.62, 128.32,
128.29, 126.63, 126.60, 126.27, 123.58, 122.50, 122.07, 120.66,
118.61, 117.43, 116.36, 116.15, 115.83, 115.62. HRMS (ESI):
m/z Calcd for [C24H13BrF2NaO, M + Na]+: 457.00101, Found:
457.00079.
2,3-bis(4-bromophenyl)naphtho[1,2-b]furan (2u)
White solid (46.3 mg, yield: 97%), m.p. 152–154 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.36 (d, J = 8.2 Hz, 1H), 7.90 (d, J = 8.1
Hz, 1H), 7.65 – 7.56 (m, 4H), 7.55 – 7.40 (m, 6H), 7.35 (d, J =
8.3 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 149.62, 148.99,
132.35, 131.86, 131.76, 131.56, 131.30, 129.44, 128.43, 128.14,
126.57, 125.53, 124.99, 124.00, 122.37, 121.98, 121.09, 120.10,
118.12, 117.99. HRMS (ESI): m/z Calcd for [C24H14Br2NaO, M
+ Na]+: 498.93036, Found: 498.93019.
2,3-bis(4-fluorophenyl)-8-methoxynaphtho[1,2-b]furan (2p)
White solid (35.6 mg, yield: 92%), m.p. 148–150 ºC. 1H NMR
(400 MHz, CDCl3): δ 7.82 (d, J = 8.9 Hz, 1H), 7.71 – 7.62 (m,
3H), 7.58 (d, J = 8.5 Hz, 1H), 7.51 – 7.44 (m, 2H), 7.35 (d, J =
8.5 Hz, 1H), 7.22 – 7.12 (m, 3H), 7.05 (t, J = 8.6 Hz, 2H), 4.02
(s, 3H). 13C NMR (100 MHz, CDCl3): δ 163.80, 163.63, 161.32,
161.17, 158.38, 149.26, 149.06, 131.48, 131.40, 130.09, 128.76,
128.73, 128.68, 127.05, 127.00, 125.80, 123.58, 122.05, 117.68,
117.61, 116.25, 116.04, 115.75, 115.57, 115.53, 55.54. HRMS
(ESI): m/z Calcd for [C25H16F2NaO2, M + Na]+: 409.10106,
Found: 409.10083.
2,3-diphenylbenzofuran (4a)
White solid (26.7 mg, yield: 99%), m.p. 121–123 ºC. 1H NMR
(400 MHz, CDCl3): δ 7.71 – 7.62 (m, 2H), 7.55 (d, J = 8.1 Hz,
1H), 7.53 – 7.43 (m, 5H), 7.43 – 7.37 (m, 1H), 7.32 (dd, J = 14.0,
7.2 Hz, 4H), 7.23 (t, J = 7.5 Hz, 1H). 13C NMR (100 MHz,
CDCl3): δ 153.98, 150.51, 132.84, 130.65, 130.23, 129.75,
128.95, 128.40, 128.33, 127.61, 127.01, 124.66, 122.89, 120.01,
117.49, 111.09. HRMS (ESI): m/z Calcd for [C20H14NaO, M +
Na]+: 293.09369, Found: 293.09328.
2,3-bis(4-fluorophenyl)-6-methoxynaphtho[1,2-b]furan (2q)
2,3-bis(4-fluorophenyl)benzofuran (4b)
1
White solid (38.2 mg, yield: 99%), m.p. 139–141 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.08 (d, J = 8.8 Hz, 1H), 7.96 (d, J = 8.2
Hz, 1H), 7.65 (dd, J = 8.7, 5.4 Hz, 2H), 7.54 – 7.44 (m, 4H), 7.17
(t, J = 8.6 Hz, 2H), 7.03 (t, J = 8.7 Hz, 2H), 6.86 (d, J = 7.7 Hz,
1H), 4.01 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 163.76,
163.61, 161.29, 161.16, 155.99, 149.38, 149.30, 131.47, 131.39,
128.66, 128.58, 126.97, 126.94, 126.84, 125.84, 123.34, 122.09,
117.74, 117.39, 117.16, 116.25, 116.03, 115.72, 115.51, 112.45,
103.96, 55.55. HRMS (ESI): m/z Calcd for [C25H16F2NaO2, M +
Na]+: 409.10128, Found: 409.10106.
White solid (30 mg, yield: 99%), m.p. 96–98 ºC. H NMR
(400 MHz, CDCl3): δ 7.60 (dd, J = 8.5, 5.5 Hz, 2H), 7.53 (d, J =
7.9 Hz, 1H), 7.44 (dd, J = 8.1, 5.4 Hz, 3H), 7.33 (t, J = 7.7 Hz,
1H), 7.23 (d, J = 7.1 Hz, 1H), 7.16 (t, J = 8.5 Hz, 2H), 7.01 (t, J =
8.6 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 163.92, 163.60,
161.44, 161.14, 153.87, 149.77, 131.41, 131.33, 130.03, 128.90,
128.82, 128.55, 128.52, 126.71, 126.67, 124.83, 123.09, 119.77,
116.26, 116.20, 116.05, 115.73, 115.52, 111.13. HRMS (ESI):
m/z Calcd for [C20H12F2NaO, M + Na]+: 329.07484, Found:
329.07469.
2,3-bis(2-chlorophenyl)naphtho[1,2-b]furan (2r)
3-(4-chlorophenyl)-2-phenylbenzofuran (4c)
White solid (38.5 mg, yield: 99%), m.p. 129–131 ºC. 1H NMR
(400 MHz, CDCl3): δ 8.41 (d, J = 8.0 Hz, 1H), 7.95 (d, J = 8.0
Hz, 1H), 7.69 (d, J = 8.6 Hz, 1H), 7.61 (t, J = 7.4 Hz, 1H), 7.56 –
7.41 (m, 5H), 7.34 – 7.22 (m, 5H). 13C NMR (100 MHz, CDCl3):
δ 150.11, 149.59, 134.27, 134.01, 132.29, 132.20, 131.76,
131.63, 130.29, 130.17, 130.02, 129.97, 129.19, 128.36, 126.85,
126.54, 126.45, 125.42, 124.30, 123.51, 121.43, 120.19, 119.30,
119.23. HRMS (ESI): m/z Calcd for [C24H14Cl2NaO, M + Na]+:
411.03139, Found: 411.03112.
White solid (30 mg, yield: 99%), m.p. 102–104 ºC. 1H NMR
(400 MHz, CDCl3): δ 7.63 (dd, J = 7.7, 1.8 Hz, 2H), 7.54 (d, J =
8.2 Hz, 1H), 7.47 – 7.39 (m, 5H), 7.36 – 7.27 (m, 4H), 7.23 (t, J
= 7.0 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 153.98, 150.77,
133.52, 131.35, 131.05, 130.34, 129.83, 129.25, 128.56, 128.51,
127.05, 124.83, 123.05, 119.72, 116.25, 111.19. HRMS (ESI):
m/z Calcd for [C20H13ClNaO, M + Na]+: 327.05471, Found:
327.05453.
2,3-bis(3-methoxyphenyl)benzofuran (4d)
2,3-bis(2-chlorophenyl)-8-methoxynaphtho[1,2-b]furan (2s)
Pale yellow oil (27.4 mg, yield: 83%). 1H NMR (600 MHz,
CDCl3): δ 7.55 (d, J = 8.2 Hz, 1H), 7.50 (d, J = 7.8 Hz, 1H), 7.38
(t, J = 8.1 Hz, 1H), 7.33 (t, J = 7.8 Hz, 1H), 7.27 (d, J = 7.8 Hz,
1H), 7.25 – 7.20 (m, 3H), 7.09 (d, J = 7.5 Hz, 1H), 7.05 (s, 1H),
6.95 (d, J = 8.2 Hz, 1H), 6.84 (d, J = 8.0 Hz, 1H), 3.80 (s, 3H),
3.70 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 159.99, 159.44,
153.84, 150.30, 134.15, 131.74, 130.19, 129.96, 129.42, 124.74,
122.92, 122.24, 120.06, 119.47, 117.63, 115.06, 114.78, 113.47,
111.75, 111.07, 55.26, 55.08. HRMS (ESI): m/z Calcd for
[C22H18NaO3, M + Na]+: 353.11482, Found: 353.11449.
White solid (41.5 mg, yield: 99%), m.p. 203–205 ºC. 1H NMR
(400 MHz, CDCl3): δ 7.84 (d, J = 8.9 Hz, 1H), 7.68 (s, 1H), 7.62
(d, J = 8.5 Hz, 1H), 7.53 – 7.42 (m, 3H), 7.37 (d, J = 8.5 Hz, 1H),
7.34 – 7.22 (m, 5H), 7.19 – 7.14 (m, 1H), 3.99 (s, 3H). 13C NMR
(100 MHz, CDCl3): δ 158.33, 149.72, 149.53, 134.24, 134.05,
132.28, 132.26, 131.62, 130.24, 130.22, 130.00, 129.15, 126.99,
126.82, 126.55, 124.74, 123.24, 122.28, 119.30, 117.78, 116.72,
98.90, 55.54. HRMS (ESI): m/z Calcd for [C25H16Cl2NaO2, M +
Na]+: 441.04196, Found: 441.04163.
2,3-bis(2-chlorophenyl)-6-methoxynaphtho[1,2-b]furan (2t)
6-methyl-2,3-diphenylbenzofuran (4e)

White solid (28.1 mg, yield: 99%), m.p. 89–91 ºC.. 1H NMR
13C NMR (100 MHz, CDCl3): δ 154.01, 151.23, 132.26, 130.41,
130.22, 129.66, 129.06, 128.99, 128.60, 128.47, 127.87, 126.96,
123.65, 120.56, 117.28, 111.63. HRMS (ESI): m/z Calcd for
[C20H13ClNaO, M + Na]+: 327.05485, Found: 327.05471.
ACCEPTED MANUSCRIPT
(400 MHz, CDCl3): δ 7.63 (d, J = 7.4 Hz, 2H), 7.51 – 7.40 (m,
4H), 7.40 – 7.32 (m, 3H), 7.32 – 7.21 (m, 3H), 7.04 (d, J = 7.9
Hz, 1H), 2.48 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 154.39,
149.89, 134.99, 133.03, 130.84, 129.70, 128.89, 128.35, 128.08,
127.79, 127.50, 126.85, 124.30, 119.50, 117.40, 111.30, 21.72.
HRMS (ESI): m/z Calcd for [C21H16NaO, M + Na]+: 307.10934,
Found: 307.10902.
6-chloro-2,3-bis(4-fluorophenyl)benzofuran (4l)
white solid (27.2 mg, yield: 80%), m.p. 117–119 ºC. 1H NMR
(400 MHz, CDCl3): δ 7.61 – 7.52 (m, 3H), 7.45 – 7.38 (m, 2H),
7.34 (dd, J = 8.3, 3.6 Hz, 1H), 7.25 – 7.14 (m, 3H), 7.06 – 6.97
(m, 2H). 13C NMR (100 MHz, CDCl3): δ 164.04, 163.71, 161.55,
161.25, 153.86, 150.45, 131.33, 131.25, 130.57, 128.86, 128.78,
128.75, 127.95, 127.91, 126.25, 126.22, 123.83, 120.29, 116.39,
116.17, 115.97, 115.82, 115.60, 111.66. HRMS (ESI): m/z Calcd
for [C20H11ClF2NaO, M + Na]+: 363.03587, Found: 363.03571.
2,3-bis(4-bromophenyl)-6-methylbenzofuran (4f)
1
White solid (43.6 mg, yield: 99%), m.p. 157–159 ºC.. H
NMR (400 MHz, CDCl3): δ 7.57 (d, J = 6.6 Hz, 2H), 7.49 – 7.38
(m, 4H), 7.36 – 7.25 (m, 4H), 7.06 (d, J = 7.9 Hz, 1H), 2.48 (s,
3H). 13C NMR (100 MHz, CDCl3): δ 154.40, 148.96, 135.60,
132.28, 131.69, 131.20, 129.41, 128.26, 127.19, 124.66, 122.45,
121.82, 119.29, 116.78, 111.41, 21.74. HRMS (ESI): m/z Calcd
for [C21H14Br2NaO, M + Na]+: 462.93036, Found: 462.93019.
2,3-diphenylthieno[2,3-g]benzofuran (6)
white solid (28.4 mg, yield: 87%), m.p. 111–113 ºC. 1H NMR
(400 MHz, CDCl3): δ 7.76 (d, J = 5.5 Hz, 1H), 7.71 (d, J = 8.2
Hz, 3H), 7.54 (d, J = 5.9 Hz, 3H), 7.51 – 7.40 (m, 4H), 7.36 –
7.27 (m, 3H). 13C NMR (100 MHz, CDCl3): δ 149.23, 148.69,
137.87, 133.01, 130.81, 129.83, 128.99, 128.43, 128.06, 127.66,
126.84, 126.82, 125.94, 125.29, 118.96, 118.34, 117.44, 116.69.
HRMS (ESI): m/z Calcd for [C22H14NaOS, M + Na]+: 349.06576,
Found: 349.06546.
2,3-bis(4-fluorophenyl)-6-methylbenzofuran (4g)
1
White solid (31.7 mg, yield: 99%), m.p. 130–132 ºC.. H
NMR (400 MHz, CDCl3): δ 7.58 (dd, J = 8.1, 5.8 Hz, 2H), 7.43
(dd, J = 7.9, 5.8 Hz, 2H), 7.36 – 7.29 (m, 2H), 7.15 (t, J = 8.6 Hz,
2H), 7.07 (d, J = 7.9 Hz, 1H), 7.00 (t, J = 8.6 Hz, 2H), 2.50 (s,
3H). 13C NMR (100 MHz, CDCl3): δ 163.78, 163.54, 161.31,
161.09, 154.29, 149.16, 135.22, 131.35, 131.27, 128.73, 128.65,
127.58, 126.90, 126.87, 124.49, 119.26, 116.20, 116.12, 115.98,
115.67, 115.45, 111.34, 21.72. HRMS (ESI): m/z Calcd for
[C21H14F2NaO, M + Na]+: 343.09049, Found: 343.09015.
6-methyl-2,3-diphenyl-6H-furo[3,2-c]carbazole (8)
brown oil (13.1 mg, yield: 35%). 1H NMR (400 MHz, CDCl3):
δ 8.50 (d, J = 7.7 Hz, 1H), 7.78 (d, J = 7.8 Hz, 2H), 7.60 (d, J =
7.7 Hz, 2H), 7.56 – 7.42 (m, 6H), 7.39 – 7.27 (m, 5H), 3.94 (s,
3H). 13C NMR (100 MHz, CDCl3): δ 148.87, 148.63, 140.41,
140.21, 133.49, 131.29, 129.94, 128.95, 128.41, 127.62, 127.53,
126.52, 125.19, 122.55, 122.51, 120.37, 119.41, 118.26, 117.46,
108.51, 107.61, 104.88, 29.68. HRMS (ESI): m/z Calcd for
[C27H19NNaO, M + Na]+: 396.13589, Found: 396.13578.
3-(4-chlorophenyl)-6-methyl-2-phenylbenzofuran (4h)
1
White solid (29.3 mg, yield: 92%), m.p. 123–125 ºC.. H
NMR (400 MHz, CDCl3): δ 7.64 – 7.58 (m, 2H), 7.42 (d, J = 1.1
Hz, 4H), 7.36 – 7.26 (m, 5H), 7.06 (d, J = 8.0 Hz, 1H), 2.49 (s,
3H). 13C NMR (100 MHz, CDCl3): δ 154.40, 150.16, 135.22,
133.40, 131.55, 131.01, 130.54, 129.20, 128.48, 128.34, 127.40,
126.91, 124.47, 119.22, 116.17, 111.41, 21.72.HRMS (ESI): m/z
Acknowledgments
Calcd for [C21H15ClNaO, M
341.07011.
+
Na]+: 341.07036, Found:
This study was supported by the Fundamental Research Funds
for the Central Universities in China (Grant No: CQDXWL-
2014-Z003), the Scientific Research Foundation of China (Grant
No: 21402016). Graduate Scientific Research and Innovation
Foundation of Chongqing, China (CYS17044, CYB16032).
2,3-bis(3-methoxyphenyl)-6-methylbenzofuran (4i)
Pale yellow oil (30.6 mg, yield: 89%). 1H NMR (600 MHz,
CDCl3): δ 7.37 (dd, J = 10.1, 6.2 Hz, 3H), 7.26 – 7.20 (m, 3H),
7.07 (dd, J = 18.0, 8.8 Hz, 3H), 6.94 (d, J = 8.3 Hz, 1H), 6.82 (d,
J = 8.2 Hz, 1H), 3.80 (s, 3H), 3.70 (s, 3H), 2.50 (s, 3H). 13C
NMR (100 MHz, CDCl3): δ 159.96, 159.42, 154.27, 149.71,
135.10, 134.36, 131.95, 129.91, 129.38, 127.77, 124.34, 122.22,
119.56, 119.33, 117.56, 115.03, 114.55, 113.40, 111.62, 111.29,
55.26, 55.08, 21.72. HRMS (ESI): m/z Calcd for [C23H20NaO3,
M + Na]+: 367.13047, Found: 367.13031.
Appendix A. Supplementary data
Supplementary data related to this article can be found as a
separated file.
References and notes
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