Ligand-free Ag(I)-catalyzed carboxylative coupling of terminal alkynes, chloride compounds, and CO2

Article abstract of DOI:10.1016/j.tet.2012.08.053

Simple silver(I) slats were found to be highly efficient and selective catalyst for carboxylative coupling of aryl- or alkyl-substituted terminal alkynes, CO₂, and various allylic, propargylic or benzylic chlorides to exclusively yield function

Full text of DOI:10.1016/j.tet.2012.08.053

Tetrahedron 68 (2012) 9085e9089
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Ligand-free Ag(I)-catalyzed carboxylative coupling of terminal alkynes, chloride
compounds, and CO2
*
*
Xiao Zhang, Wen-Zhen Zhang , Ling-Long Shi, Chuang Zhu, Jiao-Lai Jiang, Xiao-Bing Lu
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 April 2012
Received in revised form 10 August 2012
Accepted 17 August 2012
Available online 24 August 2012
Simple silver(I) slats were found to be highly efficient and selective catalyst for carboxylative coupling of
aryl- or alkyl-substituted terminal alkynes, CO2, and various allylic, propargylic or benzylic chlorides to
exclusively yield functionalized 2-alkynoates. The activity is about 300 times that of the previously re-
ported N-heterocyclic carbene copper(I) catalytic system. The ligand-free silver(I) catalytic system
showed the wide generality of substrates involving both functionalized terminal alkynes and chloride
compounds.
Keywords:
Silver
Ó 2012 Elsevier Ltd. All rights reserved.
Carbon dioxide
Carboxylative coupling
Terminal alkyne
Chloride compounds
1. Introduction
coupling reaction of terminal alkynes, alkyl bromides and CO2 at
100 ꢀC.10 However, this methodology sometimes suffered from the
The utilization of CO2 in the production of high value-added
chemicals has received much attention over the past decade. This
is a consequence of CO2 being an abundant, inexpensive and non-
toxic renewable carbon resource.1 In the present strategies for
homogeneous transformation of CO2, especially in the carboxyla-
tion of various nucleophiles2e7 or relatively CeH bonds8 with CO2
to yield synthetically important carboxylic acids and derivatives,9
relatively high loading of transition-metal catalysts bearing ap-
propriate ligands were frequently used to overcome the limitation
from the thermodynamically and kinetically stable CO2 and maxi-
mize synthetic efficiency. In view of the cost and availability for the
potential applications, the development of simple catalytic systems
for CO2 transformation, which particularly show increased activity
and selectivity at lower catalyst loadings, is thus of paramount
importance.
major formation of direct coupling or dialkyl carbonate by-
products. In 2008, Anastas and co-workers disclosed silver(I)-
catalyzed reaction of phenylacetylene, CO2, and 3-bromo-1-
phenyl-1-propyne, affording arylnaphthalene lactones in poor to
moderate yield.11 (4,7-Diphenyl-1,10-phenanthroline) bis[tris(4-
fluorophenyl)phosphine]ecopper(I) nitrate catalyst developed by
Goossen and co-workers12 and N-heterocyclic carbene copper(I)
catalysts employed by Zhang and co-workers13 were proven to
exhibit promising activity in catalyzing the direct carboxylation of
a wide range of terminal alkynes with CO2 to provide the corre-
sponding propiolic acids in good yield. More recently, Kondo and
co-workers reported a CuI/PEt3 catalyzed carboxylative coupling
reaction of terminal alkynes, CO2, and alkyl bromides or iodides,
providing a variety of functionalized alkyl 2-alkynoates under
ambient conditions.14
Catalytic carboxylation of terminal alkynes with CO2 attracted
considerable interest and is emerging as a powerful tool in the
straightforward synthesis of functionalized propiolic acids and 2-
alkynoates,10e16 which are versatile synthetic intermediates of
natural products and other bioactive compounds.17 Inoue and co-
workers reported copper(I)- or silver(I)-catalyzed carboxylative
In 2010, we developed a novel Cu(I)-catalyzed carboxylative
coupling reaction of terminal alkynes, allylic chlorides, and CO2,15
wherein 10 mol % loading of N-heterocyclic carbene copper(I) cat-
alyst (IPr)CuCl (IPr¼1,3-bis(2,6-diisopropylphenyl)imidazol-2-
ylidene) was turned out to effectively suppress the non-
carboxylative direct coupling reaction (Scheme 1, B).18 A variety of
carboxylative coupling (Scheme 1, A) products, functionalized allylic
2-alkynoates were straightforwardly obtained in good yield with
high selectivity. Recently, we disclosed that only 1 mol % loading of
AgI could efficiently catalyze the direct carboxylation of terminal
alkynes under ligand-free conditions, affording functionalized
* Corresponding authors. Tel.: þ86 411 8498 5257; fax: þ86 411 8498 5256;
e-mail addresses: zhangwz@dlut.edu.cn (W.-Z. Zhang), lxb-1999@163.com (X.-B.
Lu).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.08.053

9086
X. Zhang et al. / Tetrahedron 68 (2012) 9085e9089
propiolic acids in high yield.16 With this success in hand, we envi-
sioned whether the simple silver(I) catalytic system could also serve
as highly active and selective catalyst for the above-mentioned
carboxylative coupling reaction. Herein, we report highly selective
and efficient carboxylative coupling of terminal alkynes, various
chloride compounds, and CO2 catalyzed by low loading of simple
silver(I) salt under ligand-free conditions to exclusively afford
functionalized 2-alkynoates.19
(1 mol % of AgI as catalyst and Cs2CO3 as base) gave 84% yield of
carboxylative coupling product cinnamyl phenylpropiolate (3a)
(Table 1, entry 2). Notably, the decreased loading (0.1 mol %) of AgI
catalyst led to the increased yield, which could be comparable to the
result from 10 mol % of (IPr)CuCl catalytic system (Table 1, entries 1
and 3). Furthermore, simple kinetic studies of the two catalyst sys-
tems by monitoring the reaction with LC revealed that the activity of
AgI/Cs2CO3 catalyst system was about 300 times that of our pre-
viously reported (IPr)CuCl/K2CO3 system (Fig. 1). Importantly, no
direct coupling by-product was detected even in complete conver-
sion and only carboxylative coupling product was formed exclu-
sively. Those results imply that the insertion of CO2 into silver(I)
acetylide species proceeds significantly faster than that of CO2 to the
sp-hybridized carbonecopper(IPr) bond (Scheme 1).
Scheme 1. Carboxylative coupling (A) and direct coupling (B) of terminal alkynes and
halides.
2. Results and discussion
The activity of the Ag(I)-based catalyst was initially tested by the
carboxylative coupling reaction of phenylacetylene (1a), cinnamyl
chloride (2a), and CO2 (Table 1). It was delightedly found that the
catalytic system used in the previous direct carboxylation reaction
Table 1
Ag(I)-catalyzed carboxylative coupling of phenylacetylene, cinnamyl chloride, and
a
CO2
Fig. 1. Plot of yield versus time for the carboxylative coupling reaction catalyzed by
(IPr)CuCl and AgI. Yields were determined by LC.
The control experiment showed that extremely low yield of 3awas
obtained in the absence of AgI or Cs2CO3, testifying the vital roles of
catalyst and base in this catalytic system (Table 1, entries 5 and 6).
Using K2CO3 as base gave moderate yield (Table 1, entry 7), while
KOtBu was proven to be unsuitable base to the reaction (Table 1, entry
8). Other simple silver(I) salts were alsotested as catalyst and the silver
counter-ions had an evident effect on their catalytic activities (Table 1,
entries 9e16). The superior catalytic activity of AgI could be pre-
sumably ascribed to its good solubility in DMF. AgBF4 was more effi-
cient in catalyzing this reaction (Table 1, entry 15). Because of the
highly hygroscopic nature of AgBF4, AgI was still used in our sub-
sequent investigations.
When the reaction was conducted under 0.5 MPa of CO2, de-
creased yield of carboxylative coupling product was obtained, al-
though the direct coupling by-product was also not observed (Table
1, entry 19). No carboxylative coupling product was formed in the
absence of CO2, which clearly demonstrated that the CO2 unit in 3a
came from gaseous CO2 rather than the base (Table 1, entry 20),
similar to the previously reported (IPr)CuCl system.
Even the carboxylative coupling reaction could be smoothly
carried out using very low loading of catalyst, the AgI still could be
recycled in this catalytic system. No obvious decrease in catalytic
efficiency was observed for AgI catalyst after four times recycle (see
Supplementary data).
Under the optimized reaction condition, the kinetics of the car-
boxylative coupling reaction of phenylacetylene, cinnamyl chloride,
and CO2 was also studied. The dependence of the initial rate on
phenylacetylene, cinnamyl chloride concentration, and CO2 pressure
was evaluated, respectively, by monitoring the formation of product
Entry
1c
2
3
4
5
6
7
8
Cat. (mol %)
Base
Yieldb (%)
(IPr)CuCl (10)
AgI (1)
AgI (0.1)
AgI (0.05)
d
K2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
d
91
84
91
70
11
4
74
16
81
80
83
86
77
88
94
77
84
78
80
d
AgI (0.1)
AgI (0.1)
AgI (0.1)
K2CO3
KOtBu
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
9
AgF (0.1)
AgCl (0.1)
AgBr (0.1)
AgOAc (0.1)
AgNO3 (0.1)
Ag2CO3 (0.1)
AgBF4 (0.1)
AgPF6 (0.1)
AgI (0.1)
10
11
12
13
14
15
16
17d
18e
19f
20g
AgI (0.1)
AgI (0.1)
AgI (0.1)
a
Reaction condition: 1a (2 mmol), 2a (3 mmol), base (3 mmol), 20 mL of DMF,
1.5 MPa, 24 h, 60 ꢀC.
b
Isolated yield.
See Ref. 15.
50 ꢀC.
16 h.
0.5 MPa.
In the absence of CO2.
c
d
e
f
g

X. Zhang et al. / Tetrahedron 68 (2012) 9085e9089
9087
Table 3
using LC (see Supplementary data). The rate exhibited a saturation
rate dependence on the cinnamyl chloride concentration and CO2
pressure, and first-order dependence on phenylacetylene concen-
tration, which might suggest that deprotonation of terminal alkyne
to form silver(I) acetylide is the rate limiting step (Scheme 1, a).
Once it was established that low loading of AgI and Cs2CO3 as
base was highly selective and efficient catalytic system for the
carboxylative coupling of phenylacetylene, cinnamyl chloride, and
CO2, the functional group compatibility was then investigated un-
der the optimized condition. As shown in Table 2, a wide range of
aryl- and alkyl-substituted terminal alkynes successfully un-
derwent the carboxylative coupling reaction with cinnamyl chlo-
ride and CO2 to afford the corresponding cinnamyl 2-alkynoates
exclusively in the presence of 0.1 mol % loading of AgI. Various
functional groups including aryl-OMe, -F, -Cl, -Br, -CF3, cyclopro-
pane, and cyclopentane were tolerated (Table 2, entries 4e9, 14,
and 15). The chloride group in 5-chloro-1-pentyne proved to be
inert toward this catalytic system at 60 ꢀC (Table 2, entry 12).
Ag(I)-catalyzed carboxylative coupling of phenylacetylene, chloride compounds,
and CO2
a
Entry
R
Yieldb (%)
1
2
3
4
5
6
7
8
Vinyl
Isocrotyl
47 (4b)
90 (4c)
83 (4d)
87 (4e)
80 (4f)
60 (4g)
85 (4h)
79 (4i)
70 (4j)
80 (4k)
77 (4l)
77 (4m)
75 (4n)
78 (4o)
84 (4p)
79 (4q)
76 (4r)
25 (4s)
77 (4s)
Isopropenyl
2-Chlorovinyl
Heptynyl
Phenylethynyl
Ph
2-MeC6H4
4-MeOC6H4
4-FC6H4
9
10
11
12
13
14
15
16
17
18
19c
2-FC6H4
4-BrC6H4
Table 2
4-NO2C6H4
2-NO2C6H4
4-(CH2]CH)C6H4
Ethoxycarbonyl
(Diethylamino)carbonyl
n-Pentyl
Ag(I)-catalyzed carboxylative coupling of terminal alkynes, cinnamyl chloride, and
a
CO2
n-Pentyl
a
Reaction condition: 1a (2 mmol), 2 (3 mmol), Cs2CO3 (3 mmol), 20 mL of DMF,
1.5 MPa, 24 h, 60 ꢀC.
b
Isolated yield.
100 ꢀC.
c
Entry
R
Yieldb (%)
1
2
3
4
5
6
7
8
Ph
91 (3a)
91 (3b)
92 (3c)
85 (3d)
83 (3e)
82 (3f)
74 (3g)
80 (3h)
89 (3i)
74 (3j)
86 (3k)
77 (3l)
81 (3m)
71 (3n)
75 (3o)
60 (3p)
4-MeC6H4
4-tBuC6H4
4-MeOC6H4
4-(n-C5H11)C6H4
4-FC6H4
2-ClC6H4
4-BrC6H4
4-CF3C6H4
n-Hexyl
n-Octyl
3-Chloropropyl
2-Phenylethyl
Cyclopropyl
Cyclopentyl
Cyclohexylmethyl
aryl- or alkyl-substituted terminal alkynes, CO2, and various allylic,
propargylic or benzylic chlorides to exclusively afford functional-
ized 2-alkynoates in good yield. Compared with the previously
reported N-heterocyclic carbene copper(I) catalytic system, the
ligand-free silver(I) catalytic system shows greatly enhanced ac-
tivity and selectivity at much lower catalyst loading.
9
10
11
12
13
14
15
16
4. Experimental section
4.1. General information
Unless otherwise statement, all manipulations were performed
using standard Schlenk techniques under a dry nitrogen or CO2 at-
mosphere. DMF was distilled from CaH2 at 60 ꢀC under reduced
a
Reaction condition: 1 (2 mmol), 2a (3 mmol), Cs2CO3 (3 mmol), 20 mL of DMF,
1.5 MPa, 24 h, 60 ꢀC.
b
Isolated yield.
ꢀ
pressure and stored over 4 A molecular sieves. NMR spectra were
recorded on a Bruker AvanceII 400M type (1H NMR, 400 MHz; 13C
NMR, 100 MHz) spectrometer. Multiplicity abbreviations: s¼singlet,
d¼doublet, t¼triplet, q¼quartet, m¼multiplet. High-resolution
mass spectra (HRMS) were recorded on a Q-TOF mass spectrometry
(Micromass, Wythenshawe, UK) equipped with Z-spray ionization
source. Infrared spectra (IR) were measured using a Nicolet NEXUS
FT-IR spectrophotometer. Carbon dioxide (99.999%), commercially
available terminal alkynes, chloride compounds, silver(I) salt, and
other all reagents were used without further purification.
Furthermore, the low loading of silver(I) catalytic system also
showed broad substrate scope for chloride compounds (Table 3).
Besides cinnamyl chloride, alkyl-substituted allylic chlorides,
propargylic chlorides proved applicable for the carboxylative cou-
pling reaction (Table 3, entries 1e6). A series of benzylic chlorides
bearing methyl, methoxyl, fluorine, bromine, nitryl, and vinyl
substituents could also serve as reactive carboxylative coupling
partners (Table 3, entries 7e15).
a-Chloro carbonyl compounds
were also found to be suitable substrates (Table 3, entries 16 and
17). When n-hexyl chloride was used as a carboxylative partner,
only 25% yield of carboxylative coupling product n-hexyl phenyl-
propiolate (4s) was obtained (Table 3, entry 18). When the same
reaction was conducted at elevated temperature (100 ꢀC), the yield
of 4s increased to 77% (Table 3, entry 19).
4.2. Representative experimental procedure for carboxylative
coupling reaction
Taking the carboxylative coupling of 4-methylphenylacetylene,
cinnamyl chloride (2a), and CO2 as example: A 70 mL oven dried au-
3. Conclusion
toclave containing a stir bar was charged with AgI (0.5 mg,
0.002 mmol) and Cs2CO3 (978 mg, 3.0 mmol). 4-Methylpheny
lacetylene (232 mg, 2.0 mmol), cinnamyl chloride (458 mg,
3.0 mmol), and 20 mL dry DMF were added with syringe, respectively,
In summary, we have successfully developed a simple ligand-
free silver(I) catalytic system for the carboxylative coupling of

9088
X. Zhang et al. / Tetrahedron 68 (2012) 9085e9089
after purging the autoclave with CO2 three times. The sealed autoclave
was pressurized to appropriate pressure with CO2. The reaction mix-
ture was stirred at 60 ꢀC for 24 h, then the autoclave was cooled to
room temperature and the remaining CO2 was vented slowly. The
reaction mixture was diluted with water (30 mL) and extracted with
ethyl acetate (3ꢁ30 mL). The combined organic layers were washed
with water and brine, dried over Na2SO4, and filtered. The solvent was
removed under vacuum. The product (E)-cinnamyl 4-methylphenyl
propiolate (3b) (502 mg, 1.82 mmol, 91% yield) was isolated by col-
umn chromatography on silica gel (ethyl acetate/petroleum ether:
1:25).
(100 MHz, CDCl3):
d
¼154.0, 134.9, 133.0, 130.8, 128.8, 128.7, 128.6,
119.5, 86.8, 80.6, 67.8. IR (cmꢂ1) (neat) 2220, 1708. HRMS (ESI, m/z)
calcd for C16H12O2Na [MþNa]þ: 259.0735, found: 259.0727.
4.3.8. 4-Methoxybenzyl phenylpropiolate (4j). 1H NMR (400 MHz,
CDCl3):
d
¼7.54 (2H, d, J¼7.6 Hz), 7.43e7.32 (5H, m), 6.80 (2H, d,
J¼8.0 Hz), 5.19 (2H, s), 3.79 (3H, s). 13C NMR (100 MHz, CDCl3):
d
¼160.0, 154.0, 133.0, 130.7, 130.6, 128.6, 127.1, 119.6, 114.1, 86.5,
80.7, 67.6, 55.3. IR (cmꢂ1) (neat) 2218, 1709. HRMS (ESI, m/z) calcd
for C17H14O3Na [MþNa]þ: 289.0841, found: 289.0836.
4.3.9. 4-Fluorobenzyl phenylpropiolate (4k). 1H NMR (400 MHz,
4.3. Characterization of new compounds
CD3OD):
CD3OD):
d
¼7.57e7.04 (9H, m), 5.22 (2H, s). 13C NMR (100 MHz,
d
¼164.2, 161.7, 153.9, 133.1, 130.9, 130.8, 128.7, 119.5, 115.8,
4.3.1. Cinnamyl 4-pentylphenylpropiolate (3e). 1H NMR (400 MHz,
115.6, 87.0, 80.5. IR (cmꢂ1) (neat) 2221, 1710. HRMS (ESI, m/z) calcd
CDCl3):
d
¼7.52 (2H, d, J¼8.0 Hz), 7.42 (2H, d, J¼8.0 Hz), 7.32 (2H, t,
for C16H11FO2Na [MþNa]þ: 277.0641, found: 277.0649.
J¼8.0 Hz), 7.28 (1H, t, J¼8.0 Hz), 7.18 (2H, d, J¼8.0 Hz), 6.73 (1H, d,
J¼16.0 Hz), 6.35 (1H, dt, J¼16.0, 8.0 Hz), 4.89 (2H, d, J¼8.0 Hz), 2.62
4.3.10. 2-Fluorobenzyl phenylpropiolate (4l). 1H NMR (400 MHz,
(2H, t, J¼7.6 Hz),1.61 (2H, m), 1.32 (4H, m), 0.89 (3H, t, J¼6.8 Hz). 13
C
CDCl3):
NMR (100 MHz, CDCl3):
d
¼7.56 (2H, d, J¼7.7 Hz), 7.46e7.06 (7H, m), 5.32 (2H, s). 13
C
NMR (100 MHz, CDCl3):
d
¼154.1, 146.5, 136.1, 135.3, 133.2, 128.8,
d¼162.4, 159.9, 153.8, 133.1, 130.9, 128.7,
128.7, 128.4, 126.8, 122.3, 116.7, 87.4, 80.3, 66.6, 36.1, 31.5, 30.9, 22.6,
124.4,119.5,115.8,115.6, 87.0, 80.4, 61.6. IR (cmꢂ1) (neat) 2220,1710.
HRMS (ESI, m/z) calcd for C16H11FO2Na [MþNa]þ: 277.0641, found:
277.0643.
14.1. IR (cmꢂ1) (neat) 2217, 1708. HRMS (ESI, m/z) calcd for
C
23H24O2Na [MþNa]þ: 355.1674, found: 355.1684.
4.3.2. Cinnamyl 2-chlorophenylpropiolate (3g). 1H NMR (400 MHz,
4.3.11. 4-Nitrobenzyl phenylpropiolate (4n). 1H NMR (400 MHz,
CDCl3):
d
¼7.61 (1H, d, J¼8.0 Hz), 7.45e7.27 (8H, m), 6.74 (1H, d,
CDCl3):
d
¼8.22 (2H, d, J¼8.8 Hz), 7.58e7.34 (7H, m), 5.32 (2H, s). 13
C
J¼16.0 Hz), 6.35 (1H, dt, J¼16.0, 8.0 Hz), 4.92 (2H, d, J¼4.0 Hz). 13
C
NMR (100 MHz, CDCl3):
d
¼153.5, 147.9, 142.1, 133.1, 131.0, 128.7,
NMR (100 MHz, CDCl3):
d
¼153.7, 137.5, 136.1, 135.6, 134.9, 131.8,
128.6, 124, 119.2, 87.8, 80.0, 66.0. IR (cmꢂ1) (neat) 2219, 1709. HRMS
(ESI, m/z) calcd for C16H11NO4Na [MþNa]þ: 304.0586, found:
304.0588.
129.8, 128.8, 128.4, 126.9, 126.8, 122.2, 120.0, 84.9, 82.9, 66.9. IR
(cmꢂ1) (neat) 2224, 1707. HRMS (ESI, m/z) calcd for C18H13O2NaCl
[MþNa]þ: 319.0502, found: 319.0510.
4.3.12. 2-Nitrobenzyl phenylpropiolate (4o). 1H NMR (400 MHz,
4.3.3. Cinnamyl 4-bromophenylpropiolate (3h). 1H NMR (400 MHz,
CDCl3):
NMR (100 MHz, CDCl3):
d
¼8.16 (1H, d, J¼8.0 Hz), 7.71e7.39 (8H, m), 5.69 (2H, s). 13
C
CDCl3):
d
¼7.51e7.26 (9H, m), 6.71 (1H, d, J¼15.6 Hz), 6.32 (1H, dt,
d
¼153.4, 147.3, 134.1, 133.2, 131.4, 131.0,
J¼16.0, 6.4 Hz), 4.88 (2H, d, J¼6.8 Hz). 13C NMR (100 MHz, CDCl3):
129.1, 128.7, 125.3, 119.3, 87.6, 80.1, 64.2. IR (cmꢂ1) (neat) 2223,1715.
HRMS (ESI, m/z) calcd for C16H11NO4Na [MþNa]þ: 304.0586, found:
304.0596.
d
¼153.7, 136.0, 135.6, 134.4, 132.1, 128.8, 126.9, 122.1, 118.6, 85.5,
81.6, 66.8. IR (cmꢂ1) (neat) 2213, 1693. HRMS (ESI, m/z) calcd for
C
18H13O2NaBr [MþNa]þ: 362.9997, found: 362.9998.
4.3.13. 4-Vinylbenzyl phenylpropiolate (4p). 1H NMR (400 MHz,
4.3.4. Cinnamyl hept-2-ynoate (3k). 1H NMR (400 MHz, CDCl3):
CDCl3):
d
¼7.57e7.32 (9H, m), 6.67 (1H, dd, J¼17.6, 10.8 Hz), 5.76
d
¼7.36e7.23 (5H, m), 6.65 (1H, d, J¼16.0 Hz), 6.26 (1H, dt, J¼16.0,
(1H, d, J¼17.6 Hz), 5.26 (1H, d, J¼10.8 Hz), 5.23 (2H, s). 13C NMR
8.0 Hz), 4.78 (2H, d, J¼4.0 Hz), 2.30 (2H, t, J¼8.0 Hz), 1.59e1.51 (2H,
(100 MHz, CDCl3):
d¼153.9, 138.0, 136.3, 134.4, 133.1, 130.8, 129.0,
m), 1.38e1.25 (10H, m), 0.85 (3H, t, J¼8.0 Hz). 13C NMR (100 MHz,
128.6, 126.5, 119.5, 114.6, 86.8, 80.6, 67.5. IR (cmꢂ1) (neat) 2219,
1708. HRMS (ESI, m/z) calcd for C18H14O2Na [MþNa]þ: 285.0891,
found: 285.0881.
CDCl3):
d
¼153.8, 136.0, 135.1, 128.8, 128.4, 126.7, 122.2, 90.1, 73.0,
66.2, 31.8, 29.1, 29.0, 28.9, 27.5, 22.6, 18.7, 14.1. IR (cmꢂ1) (neat)
2234, 1712. HRMS (ESI, m/z) calcd for C20H26O2Na [MþNa]þ:
321.1831, found: 321.1839.
4.3.14. n-Hexyl phenylpropiolate (4s). 1H NMR (400 MHz, CDCl3):
d
¼7.59e7.36 (5H, m), 4.23 (2H, t, J¼6.8 Hz), 1.73e1.69 (2H, m),
4.3.5. Cinnamyl 5-phenyl-2-pentynoate (3m). 1H NMR (400 MHz,
1.34e1.31 (6H, m), 0.90 (3H, t, J¼7.0 Hz). 13C NMR (100 MHz, CDCl3):
CDCl3):
d
¼7.37e7.17 (10H, m), 6.65 (1H, d, J¼16.0 Hz), 6.26 (1H, dt,
d
¼154.2, 132.9, 130.6, 128.5, 119.7, 86.0, 80.8, 66.2, 31.4, 28.4, 25.5,
J¼16.0, 8.0 Hz), 4.78 (2H, d, J¼4.0 Hz), 2.86 (2H, t, J¼8.0 Hz), 2.59
22.5, 14.0. IR (cmꢂ1) (neat) 2221, 1710. HRMS (ESI, m/z) calcd for
(2H, t, J¼8.0 Hz). 13C NMR (100 MHz, CDCl3):
d¼153.5, 139.6, 136.1,
C
15H18O2Na [MþNa]þ: 253.1204, found: 253.1203.
135.1, 128.7, 128.6, 128.4, 128.3, 126.8, 126.7, 122.2, 89.0, 73.6, 66.3
33.9, 20.9. IR (cmꢂ1) (neat) 2233, 1708. HRMS (ESI, m/z) calcd for
Acknowledgements
C
20H18O2Na [MþNa]þ: 313.1204, found: 313.1205.
We thank the National Natural Science Foundation of China
(21172026, U1162101), the National Basic Research Program of
China (973 Program: 2009CB825300) and the Fundamental Re-
search Funds for the Central Universities (DUT12LK47) for financial
support.
4.3.6. Cinnamyl
3-cyclopentyl-2-propynoate
(3o). 1H
NMR
(400 MHz, CDCl3):
d
¼7.38e7.25 (5H, m), 6.66 (1H, d, J¼16.0 Hz),
6.28 (1H, dt, J¼16.0, 8.0 Hz), 4.79 (2H, d, J¼8.0 Hz), 2.81e2.74 (1H,
m), 2.00e1.59 (8H, m). 13C NMR (100 MHz, CDCl3):
d¼154.0, 136.2,
135.3, 128.7, 128.3, 126.8, 122.4, 94.2, 72.7, 66.4, 33.2, 29.9, 25.4. IR
(cmꢂ1) (neat) 2228, 1708. HRMS (ESI, m/z) calcd for C17H18O2Na
[MþNa]þ: 277.1204, found: 277.1202.
Supplementary data
Reuse of AgI catalyst, kinetic studies, and copies of NMR spectra.
Supplementary data associated with this article can be found in the
online version, at http://dx.doi.org/10.1016/j.tet.2012.08.053.
4.3.7. Benzyl phenylpropiolate (4h). 1H NMR (400 MHz, CDCl3):
d
¼7.54 (2H, d, J¼7.2 Hz), 7.41e7.31 (8H, m), 5.24 (2H, s). 13C NMR

X. Zhang et al. / Tetrahedron 68 (2012) 9085e9089
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