Synthesis of naphthalene derivatives through inexpensive BF 3·Et2O-catalyzed annulation reaction of arylacetaldehydes with arylalkynes

Article abstract of DOI:10.1007/s11426-013-4843-7

An inexpensive BF₃·Et₂O-catalyzed annulation reaction of arylacetaldehydes with arylalkynes has been developed. Various substituted phenylacetaldehydes and phenylacetylenes can undergo this reaction, producing corresponding α-aryl su

Full text of DOI:10.1007/s11426-013-4843-7

SCIENCE CHINA
Chemistry
July 2013 Vol.56 No.7: 945–951
doi: 10.1007/s11426-013-4843-7
• ARTICLES •
Synthesis of naphthalene derivatives through inexpensive
BF3·Et2O-catalyzed annulation reaction of
arylacetaldehydes with arylalkynes
XIANG ShiKai1*, HU Hao1, MA Jing1, LI YuanZhuo1, WANG BiQin1*, FENG Chun1,
ZHAO KeQing1, HU Ping1 & CHEN XiaoZhen2
1College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China
2Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China
Received November 11, 2012; accepted December 26, 2012; published online February 21, 2013
An inexpensive BF3·Et2O-catalyzed annulation reaction of arylacetaldehydes with arylalkynes has been developed. Various
substituted phenylacetaldehydes and phenylacetylenes can undergo this reaction, producing corresponding α-aryl substituted
naphthalene derivatives. Use of inexpensive and readily available BF3·Et2O catalyst constitutes the most attractive advantage
of this transformation.
naphthalene derivatives, BF3·Et2O, arylacetaldehydes, arylalkynes, annulation reaction
workers [4] reported a TiCl4-mediated annulation reaction
1 Introduction
of α-aryl-substituted carbonyl compounds with alkynes.
Kabalka’s method greatly improved the yields of naphtha-
lene derivatives, but required the use of quantitative TiCl4
for this transformation. In 2009, the catalytic system of
AuCl3/AgSbF6 was utilized by Balamurugan group to
achieve the similar transformation to synthesize polysubsti-
tuted naphthalene derivatives (Eq. (2)) [5]. This approach is
very effective, however, use of expensive AuCl3/AgSbF6
catalyst limited its broad application.
Inexpensive BF3·Et2O is widely used as a Lewis acid cat-
alyst in organic synthesis [6]. Recently, we developed a
BF3·Et2O/ammonium salt cocatalyzed alkenylation reaction
of indoles with ,-unsaturated ketones [7]. The combina-
tion of inexpensive and readily available BF3·Et2O and an
ammonium salt as the efficient cocatalyst constitutes the
attractive advantage of the reaction. Herein, we wish to re-
port a new annulation reaction of arylacetaldehydes with
arylalkynes catalyzed by inexpensive BF3·Et2O to give
naphthalene derivatives (Eq. (3)).
The naphthalene unit is a ubiquitous skeleton in chemical
and pharmaceutical industries as well as optical and elec-
tronic materials [1]. In the past decades, the development of
some new and efficient methodologies for the synthesis of
polysubstituted naphthalene derivatives has aroused great
interest of organic chemists [2–5]. Among these methodol-
ogies, the acid-catalyzed annulation reaction of -aryl-
substituted carbonyl compounds with alkynes is quite an
efficient approach for the synthesis of naphthalene deriva-
tives. In 2002, Li and co-workers [3] realized a highly regi-
oselective synthesis of polysubstituted naphthalene deriva-
tives through GaCl3-catalyzed annulation reaction of phe-
nylacetaldehydes (and ketones) with alkynes (Eq. (1)). In
spite of the moderate yields and the application of expen-
sive GaCl3 catalyst, this annulation reaction was discovered
by them for the first time. Next year, Kabalka and co-
*Corresponding authors (email: xiangsk@hotmail.com; wangbiqin1964@126.com)
© Science China Press and Springer-Verlag Berlin Heidelberg 2013
chem.scichina.com www.springerlink.com

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Xiang SK, et al. Sci China Chem July (2013) Vol.56 No.7
Different solvents were then screened, indicating DCE as
the best reaction medium (entries 6–11, Table 1). In addi-
tion, the reaction temperature was also critical for this an-
nulation reaction (cf. entries 6, 12 and 13, Table 1). Finally,
the best result of 82% yield was achieved by increasing the
amount of phenylacetylene to 1.2 equivalents (entry 14,
Table 1).
The scope of annulation reaction was expanded to a vari-
ety of substituted phenylacetaldehydes 1 and phenylacety-
lenes 2 (Tables 2 and 3). Phenylacetaldehydes 1 with both
electron-donating groups and electron-withdrawing groups
in the benzene ring smoothly underwent this kind of trans-
formation, generating naphthalene derivatives 3 in moderate
Table 2 Annulation reaction of substituted phenylacetaldehydes (1) with
phenylacetylene (2a) a)
2 Results and discussion
Initially, we investigated the annulation reaction of phe-
nylacetaldehyde 1a and phenylacetylene 2a in the presence
of 5 mol% of FeCl3. Gratifyingly, 58% of 1-phenylnaph-
thalene 3aa was obtained when dichloroethane (DCE) was
used as the solvent (entry 1, Table 1). Although other Lewis
acid catalysts or Brønsted acid catalysts such as FeCl2·4H2O,
AgOTf, and CH3SO3H also promoted this transformation,
their efficiencies were lower than FeCl3 (entries 2–4, Table
1). TsOH hardly led to any desired product (entry 5, Table 1).
Notably, the yield was improved to 74% when BF3·Et2O was
used as a catalyst (entry 6, Table 1).
Table 1 Annulation reaction of phenylacetaldehyde (1a) with phenyla-
cetylene (2a) under different conditions a)
Entry Catalyst (mmol%) Solvent (mL)
T (℃)
80
80
80
80
80
80
80
80
80
80
80
50
rt
Yield (%) b)
1
2
3
FeCl3 (5)
FeCl2·H2O (5)
AgOTf (5)
DCE
DCE
DCE
58
27
27
28
trace
74
42
26
38
4
5
CH3SO3H (5)
TsOH (5)
DCE
DCE
6
7
8
9
10
11
12
13
14d
BF3·Et2O (5)
BF3·Et2O (5)
BF3·Et2O (5)
BF3·Et2O (5)
BF3·Et2O (5)
BF3·Et2O (5)
BF3·Et2O (5)
BF3·Et2O (5)
BF3·Et2O (5)
DCE
PhCl
toluene
MeCN
MeNO2
DMF
DCE
37
ND c)
30
DCE
DCE
ND c)
82
80
a) All the reactions were carried out in the scale of 0.3 mmol 1, 0.36
mmol 2a, 5 mmol% BF3·Et2O in 1.0 mL DCE at 80 °C if without further
note. The yields were isolated yields; b) the reactions were carried out at
90 °C. 10 mmol% BF3·Et2O was used.
a) All the reactions were carried out in the scale of 0.3 mmol 1a, 0.3
mmol 2a, 5 mmol% catalyst in 1.0 mL solvent if without further note; b)
the yields were isolated yields; c) ND = not detected; d) 0.36 mmol 2a was
used.

Xiang SK, et al. Sci China Chem July (2013) Vol.56 No.7
947
Table 3 Annulation reaction of phenylacetaldehydes (1a) with various
phenylacetylenes (2) a)
products in higher yields than the electron-deficient ones
(entries 2–5, Table 3). It is regretful that both (trimethylsi-
lyl)acetylene and internal alkyne can not undergo this
transformation to give the desired product (entries 6 and 7,
Table 3). The internal alkynes failed to undergo the reaction
possibly due to the following two reasons: i) The diphe-
nylacetylene has a weaker nucleophilicity than phenyla-
cetaldehyde; ii) The Lewis acidity of BF3·Et2O is lower
than GaCl3 or AuCl3/AgSbF6. Furthermore, the 1-hexyne 2h
was examined and gave only trace amount of product (entry
8, Table 3).
Two meta-substituted arylacetaldehydes (1g, 1h) was
employed to study the selectivity of the reaction (Eq. (4)).
The results showed that the selectivity is terrible.
To explore the application of such transformations, this
annulation reaction was scaled up to 10 mmol (Eq. (5)).
When 10 mmol of phenylacetaldehyde 1a and phenylacety-
lene 2a were used as substrates, 1.32 g of 1-phenylnaph-
thalene 3aa was obtained with the good yield of 65%. The
result indicated that the catalytic method was very efficient.
A possible mechanism for this catalytic transformation is
illustrated in Scheme 1. Initially, BF3·Et2O coordinates with
the carbonyl oxygen to form the aldehyde-Lewis acid com-
plex A [3, 5, 6]. Electrophilic attack of the carbonyl carbon
in complex A on the arylalkyne 2 takes place to generate
complex B with a vinyl carbocation stabilized by the aryl
group. Intramolecular electrophilic attack of the formed
vinyl carbocation to the aromatic ring followed by elimina-
tion of a proton generates the cyclization product D. Finally,
the complex D can aromatize by dehydration to form the
corresponding naphthalene derivative 3, releasing the cata-
lyst at the completion of catalytic cycle.
a) All the reactions were carried out in the scale of 0.3 mmol 1a, 0.36
mmol 2, 5 mmol% BF3·Et2O in 1.0 mL DCE at 80 °C if without further
note. The yields were isolated yields; b) the reactions were carried out in
PhCl (1 mL) instead of DCE at 110 °C. 20 mmol% BF3·Et2O was used.
to excellent yields 30–82% (entries 1–6, Table 2). It is
noteworthy that electronic effect of the arylacetaldehydes
component had some influence on the reaction, but the reg-
ularity was not obvious (entries 1–6, Table 2). The substit-
uents Cl and Br were compatible under these conditions,
which could be further transformed into other functionali-
ties (entries 5 and 6, Table 2).
In addition, both electron-rich and electron-deficient ar-
ylacetylenes were tolerable as the annulation reaction part-
ners with the yields of 55–82% (entries 1–5, Table 3). No-
tably, the electron-rich arylacetylenes gave the desired
3 Conclusions
In summary, we developed an inexpensive BF3·Et2O-catalyzed
annulation reaction of arylacetaldehydes with arylalkynes.

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Xiang SK, et al. Sci China Chem July (2013) Vol.56 No.7
Typical procedure: phenylacetaldehyde (36.0 mg, 0.3 mmol)
and phenylacetylene (36.7 mg, 0.36 mmol), BF3·Et2O (2.1
mg, 0.015 mmol) and DCE (1 mL) were mixed in a
Schlenck tube. The reaction mixture was stirred for 15 h at
80 °C. The solution was cooled to room temperature and the
solvent was removed under vacuum. The crude product was
purified by column chromatography on silica gel (eluent:
petroleum ether/dichloromethane, v/v = 70:1) to afford 50.2
mg (82%) of 3aa. IR:(KBr) νmax 3056, 2921, 2851 cm1;
1H NMR (400 MHz, CDCl3, ppm)  7.91–7.88 (m, 2H),
7.85–7.82 (m, 1H), 7.48–7.40 (m, 9H); 13C NMR (100 MHz,
CDCl3, ppm)  140.7, 140.2, 133.7, 131.6, 130.0, 128.2,
127.6, 127.2, 126.9, 126.0, 125.7, 125.4; MS (70 eV), m/z
(%): 204.4 (72) [M]+, 203.2 (100).
7-Methyl-1-phenylnaphthalene (3ba)
Scheme 1 Proposed mechanism for this catalytic transformation.
2-p-Tolylacetaldehyde (40.2 mg, 0.3 mmol) and
phenylacetylene (36.7 mg, 0.36 mmol), BF3·Et2O (2.1 mg,
0.015 mmol) and DCE (1 mL) were mixed in a Schlenck
tube. The reaction mixture was stirred for 15 h at 80 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 37.9 mg
(58%) of 3ba. IR(KBr): νmax 3052, 2917, 2855, 2732 cm1;
1H NMR (400 MHz, CDCl3, ppm)  7.79 (d, J = 8.0 Hz,
2H), 7.66 (s, 1H), 7.50–7.45 (m, 4H), 7.44–7.41 (m, 2H),
7.38–7.36 (m, 1H), 7.33–7.30 (m, 1H), 2.42 (s, 3H); 13C
NMR (100 MHz, CDCl3, ppm)  141.0, 139.5, 135.7, 132.0,
131.7, 130.0, 128.2, 128.1, 128.0, 127.4, 127.1, 127.0,
124.8, 124.5, 21.9; MS (70 eV), m/z (%): 218.0 (100) [M]+.
Various substituted phenylacetaldehydes and phenylacety-
lenes can undergo this reaction, providing an alternative ap-
proach for the synthesis of naphthalene derivatives. Use of
inexpensive and readily available BF3·Et2O catalyst consti-
tutes the most attractive advantage of this transformation.
Development of other methodologies for the synthesis of
naphthalene derivatives is ongoing in our laboratory.
4 Experimental
4.1 General experimental section
1
All manipulations were conducted with Schlenk tube. H
NMR spectra were recorded on the Varian 400 MHz WB
spectrometers. Chemical shifts (in ppm) were referenced to
tetramethylsilane ( = 0 ppm) in CDCl3 as an internal
standard. 13C NMR spectra were obtained by the same
NMR spectrometers and were calibrated with CDCl3 ( =
77.00 ppm). Mass spectra were obtained using Electron
Impact (EI) mass spectrometer. Arylacetaldehydes 1b–f
were synthesized according to literature method [8]. Unless
otherwise noted, materials and solvents from commercial
suppliers were used without further purification.
7-Methoxy-1-phenylnaphthalene (3ca)
2-(4-Methoxyphenyl)acetaldehyde (45.0 mg, 0.3 mmol) and
phenylacetylene (36.7 mg, 0.36 mmol), BF3·Et2O (2.1 mg,
0.015 mmol) and DCE (1 mL) were mixed in a Schlenck
tube. The reaction mixture was stirred for 15 h at 80 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 5:1) to afford 42.1 mg
(60%) of 3ca with two isomers in 92:8 ratio. IR(KBr) νmax
4.2 Experimental procedures and characterization of
products
1-Phenylnaphthalene (3aa)
1
3054, 3022, 2956, 2936, 2878, 2831 cm1; H NMR of
major product (400 MHz, CDCl3, ppm)  7.81–7.79 (m, 2H),
7.52–7.46 (m, 4H), 7.43–7.41 (m, 1H), 7.39–7.36 (m, 2H),

Xiang SK, et al. Sci China Chem July (2013) Vol.56 No.7
949
7.23 (s, 1H), 7.16 (d, J = 8.8 Hz, 1H), 3.75 (s, 3H); MS (70
eV), m/z (%): 234.1 (100) [M]+.
0.015 mmol) and DCE (1 mL) were mixed in a Schlenck
tube. The reaction mixture was stirred for 15 h at 80 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 54.0 mg
1-Methoxy-5-phenylnaphthalene (3da)
1
(64%) of 3fa. IR(KBr) νmax 3056, 2922, 2851 cm1; H
NMR (400 MHz, CDCl3, ppm)  8.04 (s, 1H), 7.80 (d, J =
8.0 Hz, 1H), 7.75 (d, J = 8.4 Hz, 1H), 7.57–7.43 (m, 8H);
13C NMR (100 MHz, CDCl3, ppm)  140.0, 139.5, 132.7,
132.2, 129.9, 129.2, 128.5, 128.1, 127.9, 127.53, 127.48,
125.8, 120.4; MS (70 eV), m/z (%): 282.0 (100) [M]+.
2-(2-Methoxyphenyl)acetaldehyde (45.0 mg, 0.3 mmol) and
phenylacetylene (36.7 mg, 0.36 mmol), BF3·Et2O (4.2 mg,
0.03 mmol) and DCE (1 mL) were mixed in a Schlenck tube.
The reaction mixture was stirred for 15 h at 90 °C. The so-
lution was cooled to room temperature and the solvent was
removed under vacuum. The crude product was purified by
column chromatography on silica gel (eluent: petroleum
ether/dichloromethane, v/v = 5:1) to afford 21.1 mg (30%)
of 3da. IR(KBr) νmax 3031, 3006, 2966, 2934, 2853, 2833
1-p-Tolylnaphthalene (3ab)
1
cm1; H NMR (400 MHz, CDCl3, ppm)  8.33–8.29 (m,
1H), 7.53–7.41 (m, 8H), 7.33–7.28 (m, 1H), 6.81 (d, J = 7.2
Hz, 1H), 3.99 (s, 3H); 13C NMR (100 MHz, CDCl3, ppm) 
155.5, 141.1, 139.8, 132.6, 130.1, 128.1, 127.5, 127.1,
125.9, 125.8, 124.7, 121.5, 118.3, 103.6, 55.6; MS (70 eV),
m/z (%): 234.2 (100) [M]+.
Phenylacetaldehyde (36.0 mg, 0.3 mmol) and 1-ethynyl-
4-methylbenzene (41.8 mg, 0.36 mmol), BF3·Et2O (2.1 mg,
0.015 mmol) and DCE (1 mL) were mixed in a Schlenck
tube. The reaction mixture was stirred for 15 h at 80 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 47.7 mg
(73%) of 3ab. IR(KBr) νmax 3037, 2963, 2918, 2857 cm1;
1H NMR (400 MHz, CDCl3):  7.92–7.85 (m, 3H), 7.51–
7.41 (m, 6H), 7.31 (s, 2H), 2.46 (s, 3H); 13C NMR (100
MHz, CDCl3):  140.2, 137.8, 136.9, 133.8, 131.7, 130.0,
129.0, 128.3, 127.4, 126.9, 126.1, 125.9, 125.7, 125.4, 21.3;
MS (70 eV), m/z (%): 218.2 (100) [M]+.
7-Chloro-1-phenylnaphthalene (3ea)
2-(4-Chlorophenyl)acetaldehyde (46.4 mg, 0.3 mmol) and
phenylacetylene (36.7 mg, 0.36 mmol), BF3·Et2O (2.1 mg,
0.015 mmol) and DCE (1 mL) were mixed in a Schlenck
tube. The reaction mixture was stirred for 15 h at 80 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 41.6 mg
1-(4-Tert-butylphenyl)naphthalene (3ac)
1
(58%) of 3ea. IR(KBr) νmax 3056, 2924, 2853 cm1; H
NMR (400 MHz, CDCl3, ppm)  7.87–7.81 (m, 3H), 7.51–
7.44 (m, 8H); 13C NMR (100 MHz, CDCl3, ppm)  140.0,
139.6, 132.3, 132.01, 131.99, 129.93, 129.86, 128.4, 127.9,
127.5, 127.4, 126.7, 125.6, 124.9; MS (70 eV), m/z (%):
238.0 (100) [M]+.
Phenylacetaldehyde (36.0 mg, 0.3 mmol) and 1-tert-butyl-
4-ethynylbenzene (57.0 mg, 0.36 mmol), BF3·Et2O (2.1 mg,
0.015 mmol) and DCE (1 mL) were mixed in a Schlenck
tube. The reaction mixture was stirred for 15 h at 80 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 60.9 mg
(78%) of 3ac. IR(KBr) νmax 3063, 3039, 2958, 2900, 2863
7-Bromo-1-phenylnaphthalene (3fa)
1
cm1; H NMR (400 MHz, CDCl3, ppm)  7.96 (d, J = 8.8
Hz, 1H), 7.90 (d, J = 8.4 Hz, 1H), 7.84 (d, J = 8.0 Hz, 1H),
7.53–7.48 (m, 4H), 7.47–7.40 (m, 4H), 1.41 (s, 9H); 13C
NMR (100 MHz, CDCl3, ppm)  150.1, 140.2, 137.7, 133.8,
2-(4-Bromophenyl)acetaldehyde (59.7 mg, 0.3 mmol) and
phenylacetylene (36.7 mg, 0.36 mmol), BF3·Et2O (2.1 mg,

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Xiang SK, et al. Sci China Chem July (2013) Vol.56 No.7
131.7, 129.7, 128.2, 127.4, 126.9, 126.2, 125.9, 125.7,
125.4, 125.2, 34.6, 31.5; MS (70 eV), m/z (%): 260.0 (100)
[M]+.
2-(3-Chlorophenyl)acetaldehyde (46.4 mg, 0.3 mmol) and
phenylacetylene (36.7 mg, 0.36 mmol), BF3·Et2O (2.1 mg,
0.015 mmol) and DCE (1 mL) were mixed in a Schlenck
tube. The reaction mixture was stirred for 15 h at 80 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 21.4 mg
1-(4-Bromophenyl)naphthalene (3ad)
1
(30%) of 3ga (3ga-1/3ga-2 = 61/39). 3ga-1: H NMR (400
MHz, CDCl3, ppm)  7.867 (d, J = 2.0 Hz, 1H), 7.82 (d, J =
8.8 Hz, 1H), 7.75 (d, J = 8.0 Hz, 1H), 7.55–7.39 (m, 7H),
7.34 (dd, J1 = 9.6 Hz, J2 = 2.0 Hz, 1H); 13C NMR (100 MHz,
CDCl3, ppm)  140.4, 140.2, 134.5, 131.6, 129.93, 129.0,
128.3, 127.8, 127.5, 127.1, 126.8, 126.7, 126.5; MS (70 eV),
Phenylacetaldehyde (36.0 mg, 0.3 mmol) and 1-bromo-4-
ethynylbenzene (65.2 mg, 0.36 mmol), BF3·Et2O (8.2 mg,
0.06 mmol) and PhCl (1 mL) were mixed in a Schlenck tube.
The reaction mixture was stirred for 15 h at 110 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 46.7 mg
(55%) of 3ad. IR(KBr) νmax 3058, 2924 cm1; 1H NMR (400
MHz, CDCl3, ppm)  7.90–7.81 (m, 3H), 7.61–7.58 (m, 2H),
7.49–7.47 (m, 2H), 7.44–7.41 (m, 1H), 7.35–7.33 (m, 3H);
13C NMR (100 MHz, CDCl3, ppm)  139.6, 138.9, 133.7,
131.7, 131.4, 131.3, 128.3, 128.0, 126.8, 126.2, 125.9, 125.6,
125.3, 121.4; MS (70 eV), m/z (%): 282.2 (100) [M]+.
1
m/z (%): 237.7 (100) [M]+. 3ga-2: H NMR (400 MHz,
CDCl3, ppm)  7.88–7.82 (m, 2H), 7.52–7.47 (m, 2H),
7.41–7.32 (m, 7H); 13C NMR (100 MHz, CDCl3, ppm) 
143.5, 139.5, 136.0, 131.4, 131.0, 129.6, 129.4, 128.7,
128.6, 128.2, 127.2, 126.7, 125.6, 125.4; MS (70 eV), m/z
(%): 238.7 (100) [M]+.
6-Methyl-1-phenylnaphthalene (3ha-1) and 1-methyl-8-phen-
ylnaphthalene (3ha-2)
1-(4-Fluorophenyl)naphthalene (3ae)
2-m-Tolylacetaldehyde (40.2 mg, 0.3 mmol) and
phenylacetylene (36.7 mg, 0.36 mmol), BF3·Et2O (2.1 mg,
0.015 mmol) and DCE (1 mL) were mixed in a Schlenck
tube. The reaction mixture was stirred for 15 h at 80 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 28.8 mg
Phenylacetaldehyde (36.0 mg, 0.3 mmol) and 1-ethynyl-4-
fluorobenzene (43.2 mg, 0.36 mmol), BF3·Et2O (8.4 mg,
0.06 mmol) and PhCl (1 mL) were mixed in a Schlenck tube.
The reaction mixture was stirred for 15 h at 110 °C. The
solution was cooled to room temperature and the solvent
was removed under vacuum. The crude product was puri-
fied by column chromatography on silica gel (eluent: petro-
leum ether/dichloromethane, v/v = 70:1) to afford 40.6 mg
(61%) of 3ae. IR(KBr) νmax 3042, 2929, 2850 cm1; 1H NMR
(400 MHz, CDCl3):  7.91–7.84 (m, 3H), 7.52–7.36 (m, 6H),
7.19–7.14 (m, 2H);13C NMR (100 MHz, CDCl3):  162.2 (d,
J = 244.4 Hz), 139.1, 136.63, 136.59, 133.7, 131.6, 131.5,
128.3, 127.8, 127.0, 126.1, 125.8, 125.7, 125.3, 115.3, 115.0;
MS (70 eV), m/z (%): 222.4 (74) [M]+, 221.1 (100).
1
(44%) of 3ha (3ha-1/3ha-2 = 53/47). H NMR (400 MHz,
CDCl3, ppm)  7.66 (s, 1H); MS (70 eV), m/z (%): 218.2
(100) [M]+.
We are grateful for the financial supports from Sichuan Provincial De-
partment of Education (11ZA108), National Natural Science Foundation of
China (21202109 and 21072140), Special Funds of Sichuan Normal Uni-
versity for Sharing the Large Precision Equipments (DJ2012-07,
DJ2011-16) and Sichuan Normal University.
1
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