Facile synthesis of substituted alkynes by nano-palladium catalyzed oxidative cross-coupling reaction of arylboronic acids with terminal alkynes

Article abstract of DOI:10.1016/j.jorganchem.2010.12.038

The oxidative cross-coupling of terminal alkynes with arylboronic acids catalyzed by the porous palladium nanospheres was developed. In the presence of silver oxide, triphenylphosphine and cesium carbonate, the reaction provided the corresponding arylalkynes with good to excellent yields. There were also other obvious advantages such as broad applicability, high selectivity, simple experimental operation as well as the convenient preparation, high efficiency and reusability of catalyst. The possible mechanism of this transition-metal nanoparticles catalyzed oxidative cross-coupling reaction of two nucleophiles was proposed.

Full text of DOI:10.1016/j.jorganchem.2010.12.038

Journal of Organometallic Chemistry 696 (2011) 1570e1573
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Facile synthesis of substituted alkynes by nano-palladium catalyzed oxidative
cross-coupling reaction of arylboronic acids with terminal alkynes
*
*
Xiaopeng Nie, Suli Liu, Yan Zong, Peipei Sun , Jianchun Bao
Jiangsu Key Laboratory of Biofunctional Materials, College of Chemistry and Materials Science, Nanjing Normal University, 122 Ninghai Road, Nanjing 210097, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The oxidative cross-coupling of terminal alkynes with arylboronic acids catalyzed by the porous palla-
dium nanospheres was developed. In the presence of silver oxide, triphenylphosphine and cesium
carbonate, the reaction provided the corresponding arylalkynes with good to excellent yields. There were
also other obvious advantages such as broad applicability, high selectivity, simple experimental opera-
tion as well as the convenient preparation, high efficiency and reusability of catalyst. The possible
mechanism of this transition-metal nanoparticles catalyzed oxidative cross-coupling reaction of two
nucleophiles was proposed.
Received 26 October 2010
Received in revised form
19 December 2010
Accepted 27 December 2010
Keywords:
Porous palladium nanospheres
Catalysis
Ó 2011 Elsevier B.V. All rights reserved.
Oxidative cross-coupling
Arylalkynes
1. Introduction
additives [18,19]. However, dimerized byproducts of the reactants
were always generated. Moreover, the reaction times of either
Arylalkynes are important precursors for natural products,
pharmaceuticals, and molecular organic materials [1e6]. Among
many widely used methods for the synthesis of arylalkynes, the
palladium-catalyzed sp2esp coupling reaction between aryl halides
and terminal alkynes with or without the presence of a copper(I)
cocatalyst, which is well known as Sonogashira reaction, has
become the most important one [7e14]. Although an impressive
variety of modifications have been reported for this reaction, some
drawbacks still remained. For example, it does not work well for
electron-deficient alkynes in many reported methods, and excess
alkynes were generally required due to the oxidative dimerization
reaction of alkynes. An umpolung complement to Sonogashira
procedure has been reported using thioalkynes and boronic acids
under non-basic condition [15]. However, thioalkynes have to be
prepared separately. In 2003, Zou et al. [16] reported a new
procedure for constructing arylalkynes through cross-coupling of
terminal alkynes with arylboronic acids catalyzed by a Pd(dppf)
Cl2eAg2O system. A cyclopalladated ferrocenylimine/Ag2O catalytic
system was also reported by Wu et al. [17]. In these palladium-
catalyzed cross-couplings, toxic, complicated and expensive
ligands should be used. This reaction was also carried out using
copper catalyst in the presence of 1e3 equiv of Ag(I) salts or other
palladium or copper catalyzed coupling reactions were generally
very long and the yields were not always very satisfactory [20].
Thus the development of green and effective catalytic system for
this cross-coupling reaction is urgent.
Transition-metal nanoparticles have attracted a great deal of
attention in recent years. There has been growing interest in the
applications of transition-metal nanoparticles in organic reactions
especially the formation of carbonecarbon bonds in the last decade
due to their large surface area and catalytic activities [21e25]. In
our previous works [26e28], bimetallic hollow palladiumecobalt
nanoparticles have been prepared and successfully used to catalyze
Sonogashira reaction in aqueous media; cobalt hollow nanospheres
were also prepared by a wet chemical method and used to catalyze
the Heck reaction and Sonogashira reaction with good results. In
our recent work, porous palladium nanospheres were prepared
using a simple solution phase approach and used to catalyze the
cycloisomerization of N, N-diallylamide or N, N-diallylsulfonamide
with very high regioselectivities and yields [29]. It was showed that
these nanoparticles might have some special catalytic function that
was different from the generally used Pd-complexes. For enlarging
the application of these nanoparticles as green and highly effective
catalyst in organic synthesis, we used the palladium nanoparticles
in oxidative cross-coupling reaction of two nucleophiles and
studied the reaction of terminal alkynes with arylboronic acids
catalyzed by the porous palladium nanospheres (Scheme 1).
* Corresponding authors. Tel./fax: þ86 (25) 83598280.
E-mail address: sunpeipei@njnu.edu.cn (P. Sun).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.12.038

X. Nie et al. / Journal of Organometallic Chemistry 696 (2011) 1570e1573
1571
Table 2
Nano Pd
The oxidative cross-coupling of terminal alkynes with arylboronic acids using
porous palladium nanospheres.
ArB(OH)2
Ar
R
+
R
Scheme 1. Nano-palladium catalyzed oxidative cross-coupling reaction of terminal
alkynes with arylboronic acids.
Entry
Ar
R
Time (h)
Yield (%)a
1
C6H5
C6H5
3
6
3
3
3
4
7
2
3
3
8
3
3
3
5
3
3
3
3
95
96
91
94
92
93
89
81
84
90
92
79
97
95
90
91
93
83
87
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
C6H5
C6H5
C6H5
C6H5
n-Bu
COOEt
CH2OPh
CH2OCH2Ph
Ph
2. Results and discussion
p-MeOC6H4
p-MeOC6H4
p-MeOC6H4
p-MeOC6H4
m-MeOC6H4
m-MeOC6H4
m-MeOC6H4
m-MeOC6H4
m-MeOC6H4
p-BrC6H4
p-BrC6H4
p-OHCC6H4
p-OHCC6H4
p-OHCC6H4
The preparation of nano-palladium was described in our pre-
vious report [29]. It was determined that the particles are of porous
spherical shape and the average diameter is about 40 nm mainly
rangingfrom 30 to 50nm. For investigating the reaction conditionsof
these nanospheres catalyzed oxidative cross-coupling reaction, the
coupling of phenylacetylene and phenylboronic acid was chosen as
a model reaction. The results of the coupling reaction are summa-
rized in Table 1.
n-Bu
CH2OPh
CH2OCH2Ph
Ph
n-Bu
COOEt
CH2OPh
CH2OCH2Ph
n-Bu
CH2OPh
n-Bu
The reactionwas carried out under a nitrogen atmosphere. While
it proceeded under air, the yield reduced slightly (Entry 4). The
experiment indicated that 1 mol% of catalyst was sufficient to
catalyze the reaction. At a temperature of 35 ꢀC, the reaction took
place smoothly. Among the solvents applied (N, N-dimethylforma-
mide (DMF), toluene and dichloromethane), dichloromethane gave
the highest yield (Entries 4, 8 and 9). As a general ligand, triphe-
nylphosphine was essential to the reaction. Without it, the yield of
the product was very low (Entry 4). As the oxidant, silver compound
played a key role in the successful cross-coupling reactions between
two nucleophiles. Among several silver compounds such as Ag2O,
AgNO3, and AgBF4, Ag2O was proved to be most effective (Entries
4e7). The appropriate quantity of Ag2O in this reaction was 1 equiv.
As the descriptions in almost all relevant reports, a basic environ-
ment was also important for this cross-coupling reaction. As general
bases, Na2CO3, K2CO3, NaOAc and Cs2CO3 were tested. The results
showed that Cs2CO3 was the most effective among the tested bases
and the yield of the product was sharply increased to 95% (Entries
1e4). We also found that Pd(OAc)2 catalyzed cross-coupling of
phenylacetylene with phenylboronic acid at the same reaction
condition gave a moderate yield of 68%. Compared with this general
palladium(II) catalyst, the palladium nanoparticles used in the
present work showed more catalytic activity.
CH2OPh
CH2OCH2Ph
a
Isolated yields.
With all substrates we employed, the reaction could finish in
a period of less than 8 h with good to excellent yields. No obvious
differences were observed between the reactions of arylboro-
nic acids with electron-withdrawing and with electron-donating
groups. This means that the reactionwas relatively insensitive to the
electronic characteristics of the substituents on arylboronic acids.
Either aromatic or aliphatic terminal alkynes could react with
arylboronic acid smoothly and give the corresponding coupling
products with high yields. A noticeable advantage of this reaction is
that for electron-deficient alkyne such as ethyl propiolate, it still
gave good yields (Entries 3, 12). The reaction was effective to both
electron-rich and electron-deficient alkynes. Another outstanding
feature with this method was its high selectivity. The active func-
tional groups such as carbonyl and ester groups on the substrates
were still remained and no side products were found (Entries 3, 12,
17e19). And also, the homo-coupling byproducts of neither terminal
alkynes nor arylboronic acids were detected by GC analysis. It was
interesting that with the substrate carried both bromo- and boronic
acid groups (Entries 15, 16), instead of the traditional Sonogashira
coupling, the boronic acid group was substituted and the bromo
group remained in this mild reaction condition.
Under the selected reaction conditions, the nano-palladium
catalyzed oxidative cross-couplings of a series of arylboronic acids
with terminal alkynes were studied. The results are listed in Table 2.
We also studied the recyclability of the nano-Pd catalyst. The
catalyst could be separated from the reaction mixture by centrifu-
gation. In the third use, the yield of the product reduced by 10%
compared to the first use of the catalyst, but the yield reduced 50%
Table 1
The optimization of the reaction conditionsa.
Ar Pd Ln
R
R
Ag
Entry
Additive
Base
Solvent
Yield (%)b
1
2
3
4
5
6
7
8
9
Ag2O
Ag2O
Ag2O
Ag2O
0
AgNO3
AgBF4
Ag2O
Ag2O
K2CO3
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
DMF
72
20
5
Na2CO3
NaOAc
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
ArB(OH)2
Ag +
95 (33c) (85d)
trace
31
79
68
20
Ar Pd
Ln
R
PdLn(II)
Ag2O
Pd + L
toluene
a
Reaction conditions: 1 mmol phenylboronic acid, 1.2 mmol phenylacetylene,
1 mol% nano-Pd, 10 mol% triphenylphosphine, 1.0 equiv additive, 2.0 equiv base in
2 mL dry CH2Cl2 at 35 ꢀC under nitrogen for 3 h.
R
Ar
b
Isolated yields.
Without PPh3.
Under air.
c
Scheme 2. The possible mechanism for nano-palladium catalyzed oxidative cross-
d
coupling reaction.

1572
X. Nie et al. / Journal of Organometallic Chemistry 696 (2011) 1570e1573
for the fourth use, which indicated that the catalyst can be used at
least for three times. In these recycles, the silver metal generated
from the reaction had not obvious effect on the reaction.
Ethyl 3-phenylpropiolate: 1H NMR (400 MHz, CDCl3):
(t, J ¼ 6.8 Hz, 3H), 4.26 (q, J ¼ 6.8 Hz, 2H), 7.32e7.35 (m, 2H),
d 1.30
7.39e7.43 (m, 1H), 7.54 (d, J ¼ 7.2 Hz, 2H). IR (KBr):
n 3020, 2185,
As shown in Scheme 2, a reaction mechanism for the palladium-
catalyzed cross-coupling reaction of arylboronic acids with
terminal alkynes was proposed on the basis of the mechanism of
previous reports and our results. First, the palladium(II), which was
generated by a oxidation of palladium(0) by silver oxide, reacted
with arylboronic acids forming arylpalladium(II) intermediate. This
intermediate then reacted with alkynylsilver to afford alkynylar-
ylpalladium(II) intermediate. Reductive elimination of this inter-
mediate followed to form desired product and palladium(0). The
palladium(0) species were then oxidized to regenerate palladium
(II) by the silver(I) species to close the catalytic cycle.
1699, 1584, 1479, 1180, 1053 cmꢂ1. MS: m/z (%) 175 (15, Mþ þ 1), 129
(100), 102 (96), 75 (13).
1-(3-Phenylprop-2-ynyloxy)benzene: 1H NMR (400 MHz, CDCl3):
d
4.95 (s, 2H), 7.03e7.08 (m, 3H), 7.30e7.37 (m, 5H), 7.46 (d,
J ¼ 5.6 Hz, 2H). IR (neat):
n
3021, 2134, 1512, 1150 cmꢂ1. MS: m/z (%)
208 (14, Mþ), 115 (100), 105 (21), 89 (19), 65 (16).
1-((3-Phenylprop-2-ynyloxy)methyl)benzene: 1H NMR (400 MHz,
CDCl3):
d 4.45 (s, 2H), 4.73 (s, 2H), 7.36e7.45 (m, 10H). IR (neat): n
3023, 2154, 1590, 1089 cmꢂ1. MS: m/z (%) 222 (5, Mþ), 221 (8), 193
(41), 115 (100), 91 (47), 77 (28), 65 (18).
1-Methoxy-4-(2-phenylethynyl)benzene: 1H NMR (400 MHz,
CDCl3):
d
3.86 (s, 3H), 6.91 (d, J ¼ 8.5 Hz, 2H), 7.33e7.39 (m, 3H),
3. Conclusion
7.50e7.56 (m, 4H). IR (KBr): n
3021, 1602, 1521, 1108 cmꢂ1. MS: m/z
(%) 208 (100, Mþ), 193 (38), 165 (27).
In summary, we have successfully prepared porous palladium
nanospheres and used these nanoparticles in the synthesis of ary-
lalkynes by the oxidative cross-coupling of terminal alkynes with
arylboronic acids. This reaction gave the desired products with high
yields and selectivity, as well as the broad applicability. Further
advantages with this method are the convenient preparation, high
efficiency and reusability of the catalyst. It will have a broad pros-
pect in the synthesis of arylalkynes. The application of this new
catalyst in organic synthesis will be further expanded. This work is
under way in our laboratory.
1-(Hex-1-ynyl)-4-methoxybenzene: 1H NMR (400 MHz, CDCl3):
d
0.89 (t, J ¼ 6.8 Hz, 3H), 1.34e1.41 (m, 2H), 1.43e1.55 (m, 2H), 2.32
(t, J ¼ 6.8 Hz, 2H), 3.73 (s), 6.74 (d, J ¼ 8.4 Hz, 2H), 7.24 (d, J ¼ 8.4 Hz,
2H). IR (neat):
3012, 2957, 2134, 1596, 1493, 1120, 1027 cmꢂ1. MS:
m/z (%) 188 (100, Mþ), 173 (43), 159 (60), 145 (80), 102 (31).
1-Methoxy-4-(3-phenoxyprop-1-ynyl)benzene:
1H
(400 MHz, CDCl3):
3.83 (s, 3H), 4.94 (s, 2H), 6.86 (d, J ¼ 8.0 Hz, 2H),
7.01e7.08 (m, 3H), 7.33e7.37 (m, 2H), 7.41 (d, J ¼ 8.0 Hz, 2H). IR
n
NMR
d
(KBr): n
3042, 2919, 2153, 1598, 1506, 1239, 1124 cmꢂ1. MS: m/z (%)
238 (8, Mþ), 145 (100), 102 (15).
1-(3-(Benzyloxy)prop-1-ynyl)-4-methoxybenzene:
1H
NMR
4. Experimental
(400 MHz, CDCl3): d 3.85 (s, 2H), 4.43 (s, 2H), 4.71 (s, 2H),6.88 (d,
J ¼ 8.5 Hz, 2H), 7.33e7.46 (m, 7H). IR (KBr):
n 3056, 2130, 1593, 1527,
4.1. General
1124, 1029 cmꢂ1. MS: m/z (%) 252 (13, Mþ), 224 (47), 145 (51), 131
(78), 103 (100), 91 (42), 77 (37).
The reagents used in the experiments were bought from Aldrich
and the Shanghai Chemical Reagent Company. The preparation and
characterizing of the catalyst were described in our previous report
[29]. 1H NMR spectra were determined on a Bruker AV 400 spec-
trometer (400 MHz) with TMS as the internal standard. FTIR spectra
were obtained with a Nexus 670 spectrometer. MS spectra were
determined on a Varian 3800 GC-MS apparatus. Elemental analysis
was performed on a PerkineElmer 240C elemental analyzer.
1-methoxy-3-(2-phenyethynyl)benzene: 1H NMR (400 MHz,
CDCl3):
d 3.84 (s, 1H), 6.90e6.92 (m, 1H), 7.08 (s, 1H), 7.15 (d,
J ¼ 8.0 Hz, 1H), 7.25e7.29 (m, 3H), 7.35e7.37 (m, 1H), 7.54e7.57 (m,
2H). IR (KBr):
Mþ).
n
3018, 1605, 1522, 1103 cmꢂ1. MS: m/z (%) 208 (100,
1-(Hex-1-ynyl)-3-methoxybenzene: 1H NMR (400 MHz, CDCl3):
0.98 (t, J ¼ 7.2 Hz, 3H), 1.47e1.54 (m, 2H), 1.59e1.64 (m, 2H), 2.44
d
(t, J ¼ 7.0 Hz, 2H), 3.82 (s, 3H), 6.85 (d, J ¼ 6.4 Hz, 1H), 6.96 (s, 1H),
7.02 (d, J ¼ 7.5 Hz, 1H), 7.20e7.24 (m, 1H). IR (neat):
n 3021, 2990,
4.2. General procedure of Pd nanoparticles catalyzed oxidative
cross-coupling reaction
2914, 2212, 1546, 1407, 1102 cmꢂ1. MS: m/z (%) 188 (100, Mþ), 173
(73), 159 (85), 115 (62), 102 (49), 91 (26).
Ethyl 3-(3-methoxyphenyl)propiolate: 1H NMR (400 MHz, CDCl3):
To 2 mL of CH2Cl2 were added 1 mmol of arylboronic acid and
1.2 mmol of terminal alkyne, then 0.01 mmol of palladium nano-
particles (1 mol%), 0.1 mmol of PPh3 (10 mol%), 1 mmol of Ag2O and
2 mmol of Cs2CO3 were added in turn. The mixture was heated at
35 ꢀC with stirring under a nitrogen atmosphere for the appropriate
time (see Table 2, monitored by TLC or GC) till reaction was
completed, then centrifuged. The solution was separated and the
precipitate was washed with ether (5 mL ꢁ 3). The solutions were
combined and washed with water, dried over anhydrous Na2SO4
and purified by column chromatography on silica gel with hex-
aneeethyl acetate (10:1) as eluent to yield the product. The
precipitate was further washed sufficiently with methanol and
ether, then dried, and the palladium nanoparticles were recovered.
d
1.39 (t, J ¼ 7.1 Hz, 3H), 3.84 (s, 3H), 4.33 (q, J ¼ 7.1 Hz, 2H),
7.01e7.04 (m, 1H), 7.13 (s, 1H), 7.21 (d, J ¼ 7.6 Hz, 1H), 7.32 (d,
J ¼ 8.0 Hz, 1H). IR (KBr):
n .
3029, 2135, 1729, 1574, 1503, 1106 cmꢂ1
MS: m/z (%) 204 (44, Mþ), 159 (60), 132 (100), 116 (17), 102 (13), 88
(10).
Methoxy-3-(3-phenoxyprop-1-ynyl)benzene: 1H NMR (400 MHz,
CDCl3):
d
3.81 (s, 3H), 4.94 (s, 2H), 6.90 (d, J ¼ 8.0 Hz, 1H), 6.99e7.07
(m, 5H), 7.23 (d, J ¼ 8.0 Hz, 1H), 7.33e7.36 (m, 2H). IR (neat):
n 3011,
2943, 2136, 1568, 1501, 1200, 1029 cmꢂ1. MS: m/z (%) 238 (37, Mþ),
145 (100), 102 (32). Anal. Calcd. for C16H14O2: C 80.65, H 5.92;
found: C 80.48, H 6.01.
1-(3-(Benzyloxy)prop-1-ynyl)-3-methoxybenzene:
(400 MHz, CDCl3): 3.83 (s, 3H), 4.44 (s, 2H), 4.72 (s, 2H), 6.93 (d,
J ¼ 7.2 Hz,1H), 7.04 (s,1H), 7.11 (d, J ¼ 6.8 Hz,1H), 7.25e7.43 (m, 6H).
1H
NMR
d
Diphenylethyne: 1H NMR (400 MHz, CDCl3):
7.56 (d, J ¼ 8.0 Hz, 4H). IR (KBr):
3025, 1618, 1547 cmꢂ1. MS: m/z
(%) 178 (100, Mþ), 152 (14), 76 (9).
Hex-1-ynyl-benzene: 1H NMR (400 MHz, CDCl3):
(t, J ¼ 6.9 Hz, 3H), 1.47e1.62 (m, 4H), 2.41 (t, J ¼ 6.9 Hz, 2H),
d 7.35e7.41 (m, 6H),
n
IR (neat): n
3026, 2984, 2135, 1623, 1600, 1209, 1021 cmꢂ1. MS: m/z
(%) 252 (6, Mþ), 251 (8), 224 (57), 103 (100), 91 (60). Anal. Calcd. for
C17H16O2: C 80.93, H 6.39; found: C 80.78, H 6.25.
d
0.95
1-Bromo-4-(hex-1-ynyl)benzene: 1H NMR (400 MHz, CDCl3):
7.28e7.32 (m, 3H), 7.42 (d, J ¼ 8.0 Hz, 2H). IR (neat):
n
3025, 2988,
d
0.88 (t, J ¼ 7.4 Hz, 3H), 1.41e1.45 (m, 2H), 1.48e1.53 (m, 2H), 2.32
(t, J ¼ 7.5 Hz, 2H), 7.17 (d, J ¼ 8.4 Hz, 2H), 7.34 (d, J ¼ 8.4 Hz, 2H). IR
(neat):
3025, 2983, 2131, 1624, 1526, 785 cmꢂ1. MS: m/z (%) 237
2225, 1620, 1526 cmꢂ1. MS: m/z (%) 158 (11, Mþ), 143 (84), 129 (74),
115 (100), 102 (14), 89 (18), 63 (16).
n

X. Nie et al. / Journal of Organometallic Chemistry 696 (2011) 1570e1573
1573
(8, Mþ), 236 (18), 238 (15),195 (71),157 (68),142 (100),129 (82),114
(47).
1-(3-(4-Bromophenyl)prop-2-ynyloxy)benzene:
(400 MHz, CDCl3): 4.93 (s, 2H), 7.02e7.06 (m, 3H), 7.31e7.43 (m,
References
1H
NMR
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d
4H), 7.47 (d, J ¼ 8.3 Hz, 2H). IR (KBr):
n 3021, 2144, 1502, 1249, 1120,
778 cmꢂ1. MS: m/z (%) 287 (5, Mþ), 207 (52), 195 (100), 114 (40).
Anal. Calcd. for C15H11BrO: C 62.74, H 3.86; found: C 62.88, H 3.77.
4-(Hex-1-ynyl)benzaldehyde: 1H NMR (400 MHz, CDCl3):
d 0.98
(t, J ¼ 7.3 Hz, 3H), 1.48e1.54 (m, 2H), 1.62e1.65 (m, 2H), 2.47 (t,
J ¼ 7.0 Hz, 2H), 7.55 (d, J ¼ 8.0 Hz, 2H), 7.82 (d, J ¼ 8.0 Hz, 2H), 10.00
[7] L. Cassar, J. Organomet. Chem. 93 (1975) 253.
(s, 1H). IR (neat):
n
3016, 2978, 2125, 1688, 1526 cmꢂ1. MS: m/z (%)
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186 (8, Mþ), 187 (53), 171 (82), 157 (68), 129 (100).
4-(3-Phenoxyprop-1-ynyl)benzaldehyde: 1H NMR (400 MHz,
CDCl3):
d
4.97 (s, 2H), 7.03e7.07 (m, 3H), 7.36 (t, J ¼ 8.0 Hz, 2H), 7.61
(d, J ¼ 8.0 Hz, 2H), 7.85 (d, J ¼ 8.0 Hz, 2H), 10.03 (s, 1H). IR (KBr):
n
3049, 2134, 1694, 1549, 1125 cmꢂ1. MS: m/z (%) 236 (11, Mþ), 208
(19), 143 (100), 115 (98). Anal. Calcd. for C16H12O2: C 81.34, H 5.12;
found: C 81.18, H 5.05.
4-(3-(Benzyloxy)prop-1-ynyl)benzaldehyde: 1H NMR (400 MHz,
CDCl3):
d 4.46 (s, 2H), 4.71 (s, 2H), 7.35e7.44 (m, 5H), 7.63 (d,
J ¼ 8.0 Hz, 2H), 7.86 (d, J ¼ 8.0 Hz, 2H), 10.03 (s, 1H). IR (KBr):
n
3021,
[18] C.D. Pan, F. Luo, W.H. Wang, Z.S. Ye, J. Cheng, Tetrahedron Lett. 50 (2009)
5044.
2120, 1705, 1561, 1105 cmꢂ1. MS: m/z (%) 250 (5, Mþ), 249 (13), 221
(64), 193 (30), 143 (62), 105 (42), 91 (100), 77 (34). Anal. Calcd. for
C17H14O2: C 81.58, H 5.64; found: C 81.77, H 5.52.
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This work was supported by the National Natural Science
Foundations of China (Project 20972068, 20772057, 20871070) and
the Leading Academic Discipline Program, 211 Project for Nanjing
Normal University (the 3rd phase).