Silver-catalyzed one-pot synthesis of benzyl 2-alkynoates under ambient pressure of CO2and ligand-free conditions

Article abstract of DOI:10.1016/j.tet.2016.12.075

The carboxylative coupling of aryl/alkyl terminal alkynes, CO₂and benzyl halides was investigated using silver iodide as the catalyst and Cs₂CO₃as the base in CH₃CN under ligand-free conditions. This reaction protocol shows a wide substrate scope and high functional group tolerance ability for benzyl halides, in which various functionalized benzyl 2-alkynoates were achieved in good yields. This one-pot, ligand-free and CH₃CN mediated reaction proved to be easy to handle and could be facilitated under atmospheric CO₂pressure.

Full text of DOI:10.1016/j.tet.2016.12.075

Accepted Manuscript
Silver-catalyzed one-pot synthesis of benzyl 2-alkynoates under ambient pressure of
CO and ligand-free conditions
2
Fang-Jie Guo, Zhi-Zhi Zhang, Jing-Yun Wang, Jing Sun, Xiang-Chen Fang, Ming-
Dong Zhou
PII:
S0040-4020(16)31381-3
10.1016/j.tet.2016.12.075
TET 28367
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 22 October 2016
Revised Date: 27 December 2016
Accepted Date: 30 December 2016
Please cite this article as: Guo F-J, Zhang Z-Z, Wang J-Y, Sun J, Fang X-C, Zhou M-D, Silver-catalyzed
one-pot synthesis of benzyl 2-alkynoates under ambient pressure of CO and ligand-free conditions,
2
Tetrahedron (2017), doi: 10.1016/j.tet.2016.12.075.
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ACCEPTED MANUSCRIPT
Graphical abstract:
O
X
AgI (2 mol%)
Cs2CO3 (1.5 eq.)
O
R2
R2
CO2
Balloon
+
+
CH3CN, 40 oC, 48 h
R1
R1
X=Br,Cl
Synthesis of benzyl 2-alkynoates via one-pot carboxylative coupling of terminal
alkynes, benzyl halides and CO2 using silver iodide as the catalyst and Cs2CO3 as
the base.

ACCEPTED MANUSCRIPT
Silver-catalyzed one-pot synthesis of benzyl 2-alkynoates under
ambient pressure of CO2 and ligand-free conditions
Fang-Jie Guo,a,c Zhi-Zhi Zhang,b,c Jing-Yun Wang,a Jing Sun,a,* Xiang-Chen Fangb
and Ming-Dong Zhou a,*
a School of Chemistry and Materials Science, Liaoning Shihua University, Dandong
Road 1, Fushun 113001, P. R. China. Tel: +86 24 56863837; Fax: +86 24 56863837;
E-mail: mingdong.zhou@lnpu.edu.cn.
b Fushun Research Institute of Petroleum and Petrochemicals, Sinopec Group, Fushun
113001, China.
c These authors contribute equally to this work.
Abstract: The carboxylative coupling of aryl / alkyl terminal alkynes, CO2 and
benzyl halides was investigated using silver iodide as the catalyst and Cs2CO3 as the
base in CH3CN under ligand-free conditions. This reaction protocol shows a wide
substrate scope and high functional group tolerance ability for benzyl halides, in
which various functionalized benzyl 2-alkynoates were achieved in good yields. This
one-pot, ligand-free and CH3CN mediated reaction proved to be easy to handle and
could be facilitated under atmospheric CO2 pressure.
Keywords: silver catalysis; benzyl 2-alkynoates; carboxylative coupling; carbon
dioxide
1 Introduction
CO2 is one of ideal C1 building blocks for producing fuels, polymers and fine
chemicals [1]. However, CO2 is a thermodynamic stable molecule with very low
reactivity which makes its transformation particularly difficult [2]. Accordingly,
transition metal catalyst usually has to be involved in most reactions [3]. Among
various catalytic transformations, the carboxylation of terminal alkynes with CO2 to
produce propiolic acids or the corresponding 2-alkynote derivatives is regarded as one
of very promising route, whereas copper (I) or silver (I) is commonly used as an
effective catalyst in the presence of a strong base [4]. On the other hand, propiolic
1

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acids and 2-alkynotes are also value-added fine chemicals, which can be used to
produce medicine, synthetic intermediates and other bio-active compounds [5]. Inoue
[6], Lu [3a-3c,4d], Kondo [4e], He [7] and other research groups have make
significant efforts on the three-component carboxylative coupling of terminal alkyne,
halide and CO2 to produce various functionalized alkyl, allylic and benzyl
2-alkynoates. However, when reviewing these reported processes carefully, we found
that most reaction conditions still suffer from some drawbacks. For example, Inoue
and co-workers have firstly described the synthesis of hexyl alkynoates from alkynes,
CO2 and 1-bromohexane using 4 mol% of copper (I) or silver (I) iodide as the catalyst
in the presence of 6 equiv. of K2CO3. However, the reaction has to be performed at
o
100 C and this method could not be applied to the synthesis of allylic or benzyl
2-alkynoates [6]. Lu et al. reported a N-heterocyclic carbene copper (I) complex
((IPr)CuCl) catalyzed carboxylation of terminal alkenes, allylic chlorides and CO2 in
the presence of K2CO3 and DMF, which provides an effective method for the
synthesis of allylic 2-alkynoates. Nevertheless, the reaction has to be carried out at 1.5
MPa with a high catalyst loading (10 mol%) [4d]. Kondo [4e] and He [7] have
respectively described the CuI promoted carboxylation of aryl / alkyl terminal alkynes,
CO2 with alkyl halides using Cs2CO3 as the base. 8 mol% of PEt3 was involved in
Kondo’s process, while the reaction was completed under ligand-free conditions in
He’s process. Notably, in both cases the reactions could be facilitated under ambient
pressure of CO2. Comparing to Cu (I), the application of Ag (I) seems to be more
advantageous since Ag (I) is more stable and the carboxylation can be smoothly
completed with rather low catalyst loading. Lu et al. have successfully developed a
AgI / Cs2CO3 catalyzed carboxylative coupling of aryl / alkyl terminal alkynes, CO2
with various chlorides using only 0.1 mol% of AgI under ligand-free conditions.
Nevertheless, when reducing the reaction pressure from 1.5 to 0.5 MPa, the product
yield was also significantly decreased [3a]. In addition, Zhang et al. disclosed a
poly-NHC-Ag(I) promoted carboxylation of terminal alkyne and CO2, and excellent
product yields could be achieved with merely 0.3 mol% of catalyst [8]. Recently, our
group also reported a 1 mol% NHC-Ag(I) complex catalyzed carboxylation of aryl /
2

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alkyl terminal alkyne with CO2, and a wide range of aryl or alkyl substituted propiolic
acids could be obtained in good yields under ambient temperature and pressure [9]. In
continue our study on the carboxylation of CO2, we were interested in further
investigating the Ag(I)-catalyzed three-component carboxylative coupling of terminal
alkynes, CO2 and benzyl halide to produce benzyl 2-alkynoates. It has been reported
that the carboxylative coupling using benzyl halide as the substrate often lead to a low
selectivity since the side reaction - formation of dibenzyl carbonate - could not be
avoided, therefore this reaction is so far still rarely reported [6]. In this context, a
convenient approach to preparing benzyl 2-alkynoates via the one-pot carboxylative
coupling of terminal alkynes, benzyl halides and CO2 using AgI as the effective
catalyst and Cs2CO3 as the base under mild condition is developed.
2 Results and discussion
To explore the reactivity, phenylacetylene 1a and 3-cyanobenzyl bromide 2a were
initially chosen as the model substrates to react with CO2 (Table 1). Control
experiment showed that the reaction could not be proceeded without the involvement
of the catalyst or the base (Table 1, entries 1 and 2). Different Ag salts including
AgNO3, AgOAc and AgI were then applied as the catalyst in the presence of 1.5 equiv.
Cs2CO3 in CH3CN at 40 oC. The results showed that AgI was the most active catalyst,
in which 85% of the desired product 3aa could be obtained (Table 1, entries 3-5).
Thus, AgI was used as the catalyst for further studies. Reducing the amount of AgI
from 2 to 0.5 mol%, the yield of 3aa was also reduced (Table 1, entries 5-7).
Nevertheless, the yield was similar to that of 2 mol% while using 5 mol% of AgI
(Table 1, entry 8). As most reported carboxylation reactions [3b, 6, 10], the base
played very important roles on the formation of 2-alkynoates. Despite K2CO3 proved
to be effective, it resulted in much lower yields of products as compared to Cs2CO3
(Table 1, entry 9). Moreover, the reaction could not be promoted when applying other
bases such as Na2CO3, KOH, NaOH, KOtBu and NaOtBu (Table 1, entries 10-14).
Reducing the amount of Cs2CO3 from 1.5 to 1.0 equiv. or increasing to 2.0 equiv., the
product yields were also reduced (Table 1, entries 15-17). The reaction was further
screened by the variation of solvents, and CH3CN proved to be the most efficient
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solvent (Table 1, entries 18-21). Further optimization indicated that lowering or
elevating the reaction temperature only led to the decreased yield of compound 3aa
(Table 1, entries 22-24). Lastly, the reaction was carried out under the conditions in
references 7a and 9, affording 3aa in 40% and 61% yield respectively (Table 1,
entries 25-26). Accordingly, a standard reaction condition A (2 mol % of AgI, 1.5
equiv. of Cs2CO3, 1 atm of CO2 at 40 °C in CH3CN for 48 h) was obtained.
Table 1 Optimization of reaction conditionsa
Entry
1
Catalyst (mol%)
-
Base (equiv.)
Cs2CO3 (1.5)
-
Solvent
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
DMF
Yieldb (%)
0
2
AgI (2)
AgNO3 (2)
AgOAc (2)
AgI (2)
AgI (1)
AgI (0.5)
AgI (5)
AgI (2)
AgI (2)
AgI (2)
AgI (2)
AgI (2)
AgI (2)
AgI (2)
AgI (2)
AgI (2)
AgI (2)
nr
3
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
K2CO3 (1.5)
Na2CO3 (1.5)
KOH (1.5)
31
51
85
74
66
88
40
nr
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
nr
NaOH (1.5)
KOtBu (1.5)
NaOtBu (1.5)
Cs2CO3 (1.0)
Cs2CO3 (1.2)
Cs2CO3 (2.0)
Cs2CO3 (1.5)
nr
nr
nr
75
75
77
73
4

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19
20
21
22
23
24
25f
26g
AgI (2)
AgI (2)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.5)
Cs2CO3 (1.2)
Cs2CO3 (1.5)
DMSO
21
0
CH2Cl2
THF
AgI (2)
61
48c
78d
63e
40
61
AgI (2)
CH3CN
CH3CN
CH3CN
DMF
AgI (2)
AgI (2)
CuI(10)
Ag-NHC (1)
CH3CN
a
Reaction conditions: 1a (1.0 mmol), 2a (1.1 mmol), CO2 (99.999%, balloon),
solvent (5 mL), 40 oC, 48 h; b Isolated yields; c rt; d 60 oC; e 80 oC; f ref 7a; g ref 9.
With the standard condition A in hand, we then carefully explored the substrate
scope of this reaction. First, the carboxylation of various alkynes with 3-cyanobenzyl
bromide 2a and CO2 was examined. As shown in Table 2, the reaction can be
proceeded for both aryl and alkyl substituted terminal alkynes, affording 3aa-3ma as
the only isolated products. In the case of using aryl alkynes, the electronic effect of
substituents on the phenyl ring plays important roles on reactivity. Good yields can be
achieved for aryl alkynes bearing electron-donating groups such as CH3, n-Pr, Ph and
OCH3, giving the corresponding products 3ba-3ea in 66-73% of isolated yields.
Fluoro and chloro substituted aryl alkynes also resulted in satisfactory yields of
3fa-3ha. Unfortunately, aryl alkynes bearing electron-withdrawing groups such CN or
NO2 on the phenyl ring only led to moderate yields (3ia, 3ja). The reaction also
resulted in moderate yields (3ka, 3la, 3ma) for aliphatic terminal alkynes. Owing to
the comparatively low activity, the activation of sp C-H bond of aliphatic and
electron-poor aryl terminal alkynes might be more difficult, which may be responsible
for the low product yields. It has also been found that the formation of byproduct
dibenzyl carbonates could not be hindered for the reactions of 3ia-3ma.
5

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Table 2 Substrate scope of terminal alkynesa,b.
O
CN
Cl
O
3ha 65%
a
Reaction conditions: 1 (1.0 mmol), 2a (1.1 mmol), Cs2CO3 (1.5 mmol), CO2
(99.999%, balloon), AgI (0.02 mmol), CH3CN (5 mL), 40 oC, 48 h; b Isolated yields.
Subsequently, the carboxylation of phenylacetylene 1a with various benzyl
bromides or benzyl chlorides was examined under condition A (Table 3). The reaction
proved to be applicable for both benzyl chlorides and benzyl bromides, and no
obvious differences on activity can be observed. Good yields can be achieved for
benzyl bromide or chloride with 1a under standard conditions (3ab). Aryl bromides or
chlorides bearing electron-donating groups such as CH3, t-Bu and OCH3 resulted in
71-85% of 3ac-3ae. Halogen substituted aryl halides led to 62-91% of 3af-3aj. The
reaction is also applicable for aryl halides bearing strong electron-withdrawing CN,
6

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CF3 or NO2 groups, leading to 63-87% of 3ak-3an. For allylic / propargylic halides,
moderate yields of the corresponding products were also afforded (3ao-3ap).
Additionally,
the
reaction
using
the
secondary
benzyl
halide-
(bromomethylene)dibenzene resulted in an inferior yield of 3aq.
Table 3 Substrate scope of benzyl halidesa,b.
O
O
3ao X=Br 47%
a
Reaction conditions: 1a (1.0 mmol), 2 (1.1 mmol), Cs2CO3 (1.5 mmol), CO2
(99.999%, balloon), AgI (0.02 mmol), CH3CN (5 mL), 40 oC, 48 h. b Isolated yields.
In general, this reaction protocol shows a wide substrate scope and high functional
group tolerance ability for benzyl halides. This one-pot, ligand-free and CH3CN
7

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mediated synthetic route is also easy to handle, as the low boiling point CH3CN can
be simply evaporated in vacuo and the isolation of benzyl 2-alkynoates and the ligand
can be avoided. It is noteworthy that an important synthetic intermediate -
2-iodobenzyl 3-phenylpropiolate can be also successfully synthesized in satisfactory
yield using our reaction protocol (3ai). 2-iodobenzyl 3-phenylpropiolate can be used
to synthesis isochromenone, which is a major fragment containing in various natural
products and biologically active compounds (Scheme 1) [11].
Scheme 1 Synthesis of isochromenone
Based on the literature precedents [1e, 3a, 3b, 7b, 9, 12] and experimental
observations, the possible reaction mechanism is proposed as shown in Scheme 2.
Firstly, terminal alkynes 1 coordinates with silver (I) species to form a species A.
Subsequent deprotonation of A by Cs2CO3 leads to the formation of the silver(I)
acetylide B. Then, the insertion of CO2 to C-Ag bond of B gives a silver propiolate
intermediate C. Finally, the coupling of C with benzyl halide 2 affords the desired
product 3, releasing Ag (I) species to fulfill a catalytic cycle.
Scheme 2 The proposed mechanism
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3 Conclusions
In summary, we have successfully developed a simple and easy method for the
synthesis of benzyl 2-alkynoates via one-pot carboxylative coupling of terminal
alkynes, benzyl halides and CO2 using silver iodide as the catalyst and Cs2CO3 as the
base. By using this three-component carboxylative coupling reaction, benzyl
2-alkynoates with various functional groups can be achieved in good yields under
ambient pressure of CO2.
4 Experimental Section
General Information
All manipulations were performed using standard Schlenk techniques under a dry
nitrogen or CO2 atmosphere. All the experiments were performed in flame-dried
Schlenk tubes. NMR spectra were determined on a Bruker Ascend HD 500 (1H NMR,
500 MHz; 13C NMR, 125 MHz) spectrometer using CDCl3 as solvents. IR spectra
were recorded on a Spectrum GX FT-IR spectrometer. HRMS (ESI) determinations
were carried out on a Bruker Daltonics McriOTOF II spectrometer. HRMS (EI) were
measured with a Agilent Technologies 5973N. The cesium carbonate was dried for 12
h in vacuo at 120 °C, and CO2 (99.999%, balloon) was dried by 4Å molecular sieves
prior to use. Silver (I) salts and other reagents of analytic grades were used as
received.
General procedure of Ag (I)-catalyzed carboxylation
In a typical procedure, a 50 mL Schlenk tube was charged with alkyne 1 (1.0
mmol), benzyl halide 2 (1.1 mmol), AgI (0.02 mmol), Cs2CO3 (1.5 mmol) and
anhydrous CH3CN (5 mL). CO2 (99.999%, balloon) were then introduced into the
reaction mixture under stirring. After stirring at 40 ºC for 48 hours, the reaction
mixture was cooled to room temperature, filtered and evaporated in vacuo. The
resulting residue was then purified by column chromatography on silica gel (eluent:
petroleum ether : ethyl acetate = 20:1) to afford the corresponding products 3aa-3aq.
1
3-Cyanobenzyl 3-phenylpropiolate (3aa): White solid (223 mg, 85%); H NMR
(CDCl3, 500 MHz) δ 7.72 (s, 1 H), 7.64 (t, J = 8.0 Hz, 2 H), 7.60-7.56 (m, 2 H),
13
7.52-7.42 (m, 2 H), 7.38 (t, J = 8.0 Hz, 2 H), 5.27 (s, 2 H); C NMR (CDCl3, 125
9

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MHz) δ 153.47, 136.52, 133.03, 132.52, 132.09, 131.70, 130.90, 129.50, 128.60,
119.17, 118.33, 112.87, 87.52, 79.98, 66.04; IR (cm-1) (KBr) 2226, 1710, 1486, 1445,
1288; HRMS (ESI, m/z) calcd. for C17H12NO2 [M+H]+: 262.0863, found: 262.0869.
1
3-Cyanobenzyl 3-(p-tolyl)propiolate (3ba): White solid (202 mg, 73%); H NMR
(CDCl3, 500 MHz) δ 7.73 (s, 1 H), 7.65 (d, J = 8.0 Hz, 2 H), 7.54-7.46 (m, 3 H), 7.19
(d, J = 7.5 Hz, 2 H), 5.27 (s, 2 H), 2.38 (s, 3 H); 13C NMR (CDCl3, 125 MHz) δ
153.74, 141.68, 136.65, 133.11, 132.56, 132.12, 131.75, 129.51, 129.42, 116.10,
112.93, 88.20, 79.71, 66.01, 21.73; IR (cm-1) (KBr) 2226, 2213, 1710, 754, 685;
HRMS (ESI, m/z) calcd. for C18H14NO2 [M+H]+: 276.1019, found: 276.1036.
3-Cyanobenzyl 3-(4-propylphenyl)propiolate (3ca): Yellow solid (200 mg, 66%);
1H NMR (CDCl3, 500 MHz) δ 7.72 (s, 1 H), 7.63 (t, J = 9.0 Hz, 2 H), 7.52-7.46 (m, 3
H), 7.18 (d, J = 8.0 Hz, 2 H), 5.27 (s, 2 H), 2.60 (t, J = 7.5 Hz, 2 H), 1.67-1.59 (m, 2
13
H), 0.94-0.91 (t, J = 7.5 Hz, 3 H); C NMR (CDCl3, 125 MHz) δ 153.48, 146.22,
136.56, 132.96, 132.41, 131.93, 131.56, 129.39, 128.69, 118.23, 116.18, 112.74,
88.02, 79.65, 65.86, 37.90, 23.97, 13.55; IR (cm-1) (KBr) 2228, 1711, 1605, 1485,
1290; HRMS (ESI, m/z) calcd. for C20H18NO2 [M+H]+: 304.1332, found: 304.1338.
3-Cyanobenzyl 3-([1,1'-biphenyl]-4-yl)propiolate (3da): Yellow solid (243 mg,
72%); 1H NMR (CDCl3, 500 MHz) δ 7.75 (s, 1 H), 7.69-7.63 (m, 4 H), 7.63-7.57 (m,
4 H), 7.52 (t, J = 7.5 Hz, 1 H), 7.46 (t, J = 7.5 Hz, 2 H), 7.39 (t, J = 7.5 Hz, 1 H), 5.29
(s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 153.55, 143.75, 139.68, 136.58, 133.60,
132.56, 132.14, 131.76, 129.53, 128.97, 128.22, 127.28, 127.12, 118.37, 117.90,
112.95, 87.66, 80.60, 66.09; IR (cm-1) (KBr) 2214, 1708, 1601, 1477, 1283; HRMS
(ESI, m/z) calcd. for C23H16NO2 [M+H]+: 338.1176, found: 338.1183.
3-Cyanobenzyl 3-(4-methoxyphenyl)propiolate (3ea): White solid (198 mg, 68%);
1H NMR (CDCl3, 500 MHz) δ 7.72 (s, 1 H), 7.66-7.62 (m, 2 H), 7.54 (d, J = 9.0 Hz, 2
H), 7.50 (t, J = 7.5 Hz, 1 H), 6.89 (d, J = 9.0 Hz, 2 H), 5.26 (s, 2 H), 3.83 (s, 3 H); 13C
NMR (CDCl3, 125 MHz) δ 161.70, 153.68, 136.69, 135.01, 132.47, 131.99, 131.64,
129.44, 118.33, 114.30, 112.82, 110.89, 88.46, 79.51, 65.85, 55.34; IR (cm-1) (KBr)
2222, 1706, 1607, 1510, 1292, 1251; HRMS (ESI, m/z) calcd. for C18H14NO3 [M+H]+:
292.0968, found: 292.0978.
10

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1
3-Cyanobenzyl 3-(4-fluorophenyl)propiolate (3fa): White solid (210 mg, 75%); H
NMR (CDCl3, 500 MHz) δ 7.73 (s, 1 H), 7.67-7.64 (m, 2 H), 7.62-7.57 (m, 2 H), 7.52
(t, J = 7.5 Hz, 1 H), 7.11-7.06 (m, 2 H), 5.28 (s, 2 H); 13C NMR (CDCl3, 125 MHz) δ
163.97 (d, J = 252.0 Hz), 153.27, 136.43, 135.31 (d, J = 9.12 Hz,) 132.48, 132.07,
131.65, 129.46, 118.28, 116.13 (d, J = 22.5 Hz), 115.26 (d, J = 3.62 Hz), 112.84,
86.40, 79.89 (d, J = 1.75 Hz), 66.04; IR (cm-1) (KBr) 2222, 1706, 1601, 1506, 1460,
1381, 1280; HRMS (ESI, m/z) calcd. for C17H11FNO2 [M+H]+: 280.0768, found:
280.0775.
3-Cyanobenzyl 3-(3-fluorophenyl)propiolate (3ga): White solid (196 mg, 70%); 1H
NMR (CDCl3, 500 MHz) δ 7.73 (s, 1 H), 7.67-7.65 (m, 2 H), 7.53 (t, J = 8.0 Hz, 1 H),
13
7.40-7.33 (m, 2 H), 7.29-7.25 (m, 1 H), 7.20-7.14 (m, 1 H), 5.29 (s, 1 H); C NMR
(CDCl3, 125 MHz) δ 162.10 (d, J=247.3 Hz), 153.09, 136.36, 132.50, 132.10, 131.68,
130.35 (d, J=8.1 Hz) 129.49, 128.87 (d, J = 3.6 Hz). 120.94 (d, J = 9.0 Hz), 119.62 (d,
J = 9.0 Hz), 118.44, 118.26 (d, J = 3.6 Hz), 112.87, 85.59 (d, J = 3.6 Hz), 80.42, 66.15;
IR (cm-1) (KBr) 2225, 1706, 1582, 1431, 1311, 1216; HRMS (ESI, m/z) calcd. for
C17H11FNO2 [M+H]+: 280.0768, found: 280.0769.
3-Cyanobenzyl 3-(4-chlorophenyl)propiolate (3ha): Yellow solid (193 mg, 65%);
1H NMR (CDCl3, 500 MHz) δ 7.73 (s, 1 H), 7.65 (d, J = 7.5 Hz, 2 H), 7.54-7.50 (m, 3
13
H), 7.37 (d, J = 8.5 Hz, 2 H), 5.28 (s, 2 H); C NMR (CDCl3, 125 MHz) δ 153.26,
137.36, 136.43, 134.22, 132.52, 132.14, 131.72, 129.52, 129.10, 118.29, 117.66,
113.94, 86.17, 80.78, 66.15; IR (cm-1) (KBr) 2222, 1699, 1587, 1479, 1379, 1298;
HRMS (ESI, m/z) calcd. for C17H11ClNO2 [M+H]+: 296.0473, found: 296.0481.
3-Cyanobenzyl 3-(4-cyanophenyl)propiolate (3ia): Yellow solid (130 mg, 45%); 1H
NMR (CDCl3, 500 MHz) δ 7.73 (s, 1 H), 7.69 (s, 4 H), 7.66 (t, J = 7.5 Hz, 2 H), 7.53
13
(t, J = 7.5 Hz, 1 H), 5.30 (s, 2 H); C NMR (CDCl3, 125 MHz) δ 152.82, 136.19,
133.34, 132.56, 132.26, 132.25, 131.77, 129.59, 124.01, 118.26, 117.71, 114.30,
113.02, 84.47, 82.89, 66.42; IR (cm-1) (KBr) 2226, 1705, 1498, 1405, 1375, 1292;
HRMS (ESI, m/z) calcd. for C18H11N2O2 [M+H]+: 287.0815, found: 287.0812.
1
3-Cyanobenzyl 3-(4-nitrophenyl)propiolate (3ja): Yellow solid (102 mg, 33%); H
NMR (CDCl3, 500 MHz) δ 8.27 (d, J = 8.5 Hz, 2 H), 7.78-7.74 (m, 3 H), 7.67 (t, J =
11

ACCEPTED MANUSCRIPT
13
7.5 Hz, 2 H), 7.54 (t, J = 7.5 Hz, 1 H), 5.31 (s, 2 H); C NMR (CDCl3, 125 MHz) δ
152.74, 148.63, 136.12, 133.77, 132.59, 132.28, 131.78, 129.59, 125.82, 123.76,
118.26, 112.99, 84.06, 83.37, 66.48; IR (cm-1) (KBr) 2229, 1709, 1514, 1403,
1344,1291; HRMS (ESI, m/z) calcd. for C17H11N2O4Na [M+H]+: 307.0713, found:
307.0707.
3-Cyanobenzyl 3-cyclopropylpropiolate (3ka): Yellow oil (113 mg, 50%); 1H NMR
(CDCl3, 500 MHz) δ 7.68 (s, 1 H), 7.64-7.58 (m, 2 H), 7.49 (t, J = 7.5 Hz, 1 H), 5.19
(s, 2 H), 1.43-1.36 (m, 1 H), 1.00-0.91 (m, 4 H); 13C NMR (CDCl3, 125 MHz) δ
153.10, 136.69, 132.38, 131.92, 131.55, 129.39, 118.31, 112.77, 94.75, 67.86, 65.63,
9.26, -0.67; IR (cm-1) (neat) 2223, 1699, 1451, 1370, 1265; HRMS (ESI, m/z) calcd.
for C14H12NO2 [M+H]+: 226.0863, found: 226.0876.
1
3-Cyanobenzyl non-2-ynoate (3la): Yellow oil (100 mg, 38%); H NMR (CDCl3,
500 MHz) δ 7.69 (s, 1 H), 7.62 (t, J = 7.5 Hz, 2 H), 7.50 (t, J = 7.5 Hz, 1 H), 5.20 (s, 2
H), 2.35 (t, J = 7.5 Hz, 2 H), 1.62-1.54 (m, 2 H), 1.44-1.36 (m, 2 H), 1.34-1.24 (m, 4
H), 0.89 (t, J = 7.5 Hz, 3 H); 13C NMR (CDCl3, 125 MHz) δ 153.13, 136.61, 132.36,
131.89, 131.51, 129.36, 118.26, 112.72, 91.06, 72.42 65.67, 31.01, 28.35, 27.26,
22.28, 18.56, 13.85; IR (cm-1) (neat) 2230, 1715, 1455, 1380, 1240; HRMS (ESI, m/z)
calcd. for C17H19NO2 [M+H]+: 270.1489, found:270.1490.
1
3-Cyanobenzyl 4-methylpent-2-ynoate (3ma): Yellow oil (90 mg, 40%); H NMR
(CDCl3, 500 MHz) δ 7.69 (s, 1 H), 7.63 (t, J = 7.5 Hz, 2 H), 7.50 (t, J = 8.0 Hz, 1 H),
13
5.21 (s, 2 H), 2.76-2.66 (m, 1 H), 1.24 (d, J = 7.0 Hz, 6 H); C NMR (CDCl3, 125
MHz) δ 153.20, 136.56, 132.38, 131.86, 131.50, 129.33, 118.22, 112.64, 95.38, 71.62,
65.64, 21.47, 20.32; IR (cm-1) (neat) 2229, 1706, 1468, 1373, 1259; HRMS (EI, m/z)
calcd. for C17H19NO2 [M]+: 227.0946, found: 227.0950.
Benzyl 3-phenylpropiolate (3ab)[3a]: Yellow solid (185 mg, 78%); 1H NMR (CDCl3,
500 MHz) δ 7.55-7.53 (m, 2 H), 7.42-7.30 (m, 8 H), 7.42-7.31 (m, 8 H), 5.24 (s, 2 H).
1
4-Methylbenzyl 3-phenylpropiolate (3ac): Yellow solid (164 mg, 71%); H NMR
(CDCl3, 500 MHz) δ 7.56-7.52 (m, 1 H), 7.44-7.40 (m, 1 H), 7.36-7.28 (m, 4 H), 7.18
(d, J = 8.0 Hz, 2 H), 5.21 (s, 2 H), 2.35 (s, 3 H); 13C NMR (CDCl3, 125 MHz) δ
153.86, 138.46, 132.91, 131.86, 130.58, 129.27, 128.73, 128.48, 119.50, 86.48, 80.52,
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67.60, 21.15; IR (cm-1) (KBr) 2215, 1702, 1488, 1445, 1376, 1280; HRMS (ESI, m/z)
calcd. for C17H14O2 [M+H]+: 251.1067, found: 251.1078.
1
4-(tert-Butyl)benzyl 3-phenylpropiolate (3ad): Yellow solid (247 mg, 85%); H
NMR (CDCl3, 500 MHz) δ 7.58-7.54 (m, 2 H), 7.46-7.40 (m, 3 H), 7.38-7.32 (m, 4
H), 5.23 (s, 2 H), 1.32 (s, 9 H); 13C NMR (CDCl3, 125 MHz) δ 153.94, 151.75,
132.97, 131.86, 130.61, 128.61, 128.53, 125.59, 119.56, 86.53, 80.55, 67.59, 34.60,
31.25; IR (cm-1) (KBr) 2212, 1705, 1485, 1368, 1283; HRMS (ESI, m/z) calcd. for
C20H20O2 [M+H]+: 293.1536, found: 293.1543.
1
4-Methoxybenzyl 3-phenylpropiolate (3ae) [3a]: Yellow solid (230 mg, 80%); H
NMR (CDCl3, 500 MHz) δ 7.56-7.52 (m, 2 H), 7.44-7.38 (m, 1 H), 7.36-7.30 (m, 4
H), 6.90 (d, J = 8.0 Hz, 2 H), 5.19 (s, 2 H), 3.79 (s, 3 H).
1
4-Fluorobenzyl 3-phenylpropiolate (3af) [3a]: Yellow solid (181 mg, 71%); H
NMR (CDCl3, 500 MHz) δ 7.58-7.54 (m, 2 H), 7.46-7.32 (m, 5 H), 7.07 (t, J = 8.5 Hz,
2 H), 5.22 (s, 2 H).
1
4-Chlorobenzyl 3-phenylpropiolate (3ag): Yellow solid (190 mg, 70%); H NMR
(CDCl3, 500 MHz) δ 7.56-7.52 (m, 2 H), 7.44-7.38 (m, 1 H), 7.36-7.22 (m, 6 H), 5.20
(s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 153.57, 134.40, 133.34, 132.89, 130.67,
129.85, 128.72, 128.48, 119.26, 86.87, 80.26, 66.64; IR (cm-1) (KBr) 2217, 1698,
1595, 1488, 1459, 1439, 1405, 1367, 1284; HRMS (ESI, m/z) calcd. for C16H11ClO2
[M+H]+: 271.0520, found: 271.0527.
1
4-Bromobenzyl 3-phenylpropiolate (3ah) [4d]: Yellow solid (237 mg, 75%); H
NMR (CDCl3, 500 MHz) δ 7.59 (s, 1 H), 7.57 (d, J = 7.5 Hz, 1 H), 7.53-7.51 (m, 2 H),
7.45 (t, J = 7.5 Hz, 1 H), 7.37 (t, J = 8.0 Hz, 2 H), 7.29 (d, J = 8.5 Hz, 2 H), 5.21 (s, 2
H).
2-Iodobenzyl 3-phenylpropiolate (3ai): Yellow oil (330 mg, 91%); 1H NMR (CDCl3,
500 MHz) δ 7.84-7.78 (m, 1 H), 7.56-7.50 (m, 2 H), 7.44-7.37 (m, 2 H), 7.36-7.28 (m,
3 H), 7.10-6.96 (m, 1 H), 5.25 (s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 153.54, 139.54,
137.37, 133.03, 130.72, 130.11, 129.65, 129.36, 128.54, 128.42, 119.43, 87.04, 80.29,
71.30; IR (cm-1) (neat) 2218, 1709, 1590, 1565, 1374, 1280; HRMS (EI, m/z) calcd.
for C16H11BrIO2 [M]+: 361.9804, found: 361.9808.
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1
2,6-Dichlorobenzyl 3-phenylpropiolate (3aj) [13]: Yellow solid (239 mg, 78%); H
NMR(CDCl3, 500 MHz) δ 7.58-7.54 (m, 2 H), 7.46-7.40 (m, 1 H), 7.38-7.32 (m, 4 H),
7.26 (t, J = 7.5 Hz, 1 H), 5.54 (s, 2 H).
1
2-Cyanobenzyl 3-phenylpropiolate (3ak): White solid (165 mg, 63%); H NMR
(CDCl3, 500 MHz) δ 7.71 (d, J = 8.0 Hz, 1 H), 7.68-7.56 (m, 4 H), 7.50-7.43 (m, 2 H),
7.38 (t, J = 7.5 Hz, 2 H), 5.45 (s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 153.36, 138.25,
133.05, 130.84, 129.58, 129.05, 128.56, 119.24, 116.75, 112.41, 87.56, 79.94, 64.82;
IR (cm-1) (KBr) 2221, 1718, 1491, 1454, 1368, 1281; HRMS (ESI, m/z) calcd. for
C17H11NO2 [M+H]+: 262.0863, found: 262.0878.
1
4-Cyanobenzyl 3-phenylpropiolate (3al): Yellow solid (225 mg, 86%); H NMR
(CDCl3, 500 MHz) δ 7.69 (d, J = 8.0 Hz, 2 H), 7.61-7.57 (m, 2 H), 7.53 (d, J = 8.5 Hz,
13
2 H), 7.50-7.44 (m, 1 H), 7.37 (t, J = 8.0 Hz, 2 H), 5.31 (s, 2 H); C NMR (CDCl3,
125 MHz) δ 153.49, 140.18, 133.06, 132.46, 130.94, 128.63, 128.57, 119.20, 118.44,
112.36, 87.58, 79.99, 66.25; IR (cm-1) (KBr) 2228, 1702, 1488, 1377, 1284; HRMS
(ESI, m/z) calcd. for C17H11NO2 [M+H]+: 262.0863, found: 262.0875.
4-(Trifluoromethyl)benzyl 3-phenylpropiolate (3am) [13]: Yellow solid (240 mg,
1
78%); H NMR (CDCl3, 500 MHz) δ 7.65 (d, J = 8.5 Hz, 2 H), 7.59-7.56 (m, 2 H),
7.53 (d, J = 8.0 Hz, 2 H), 7.47-7.42 (m, 1 H), 7.37 (t, J = 7.5 Hz, 2 H), 5.30 (s, 2 H).
4-Nitrobenzyl 3-phenylpropiolate (3an) [3a]: Yellow solid (246 mg, 87%); 1H NMR
(CDCl3, 500 MHz) δ 8.26-8.22 (m, 2 H), 7.62-7.56 (m, 4 H), 7.49-7.44 (m, 1 H), 7.39
(t, J = 7.5 Hz, 2 H), 5.35 (s, 2 H).
1
Cinnamyl 3-phenylpropiolate (3ao) [4d]: White solid (103 mg, 47%); H NMR
(CDCl3, 500 MHz) δ 7.59-7.54 (m, 2 H), 7.45-7.22 (m, 8 H), 6.70 (d, J = 16.0 Hz, 1
H), 6.31 (dt, J = 16.0, 6.5 Hz, 1 H), 4.87 (dd, J = 6.5, 1.5 Hz, 2 H).
1
But-2-yn-1-yl 3-phenylpropiolate (3ap) [4d]: Yellow solid (85 mg, 42%); H NMR
(CDCl3, 500 MHz) δ 7.59-7.55 (m, 2 H), 7.48-7.42 (m, 1H), 7.39-7.34 (m, 2 H), 4.79
(q, J = 7.5 Hz, 2 H), 1.87 (t, J = 7.5 Hz, 3 H).
1
Benzhydryl 3-phenylpropiolate (3aq) [14]: White solid (22 mg, 8%); H NMR
(CDCl3, 500 MHz) δ 7.62-7.56 (m, 2 H), 7.46-7.28 (m, 13 H), 7.01 (s, 1 H).
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Acknowledgements
M.D.Z thanks the National Science Foundation of China (21101085), Natural
Science Foundation of Liaoning Province (2015020196), Fushun Science &
Technology Program (FSKJHT 201423), Liaoning Excellent Talents Program in
University (LJQ2012031), and Research Project Fund of Liaoning Provincial
Department of Education (L2016022) for the financial supports.
References
[1] (a) Cokoja, M.; Bruckmeier, C.; Rieger, B.; Herrmann, W. A.; Kühn, F. E. Angew. Chem., Int.
Ed. 2011, 50, 8510–8537; (b) He, M.; Sun, Y.; Han, B. Angew. Chem., Int. Ed., 2013, 52, 9620–
9633; (c) Hu, Y. H. Washington, DC: American Chemical Society, 2010. (d) Yu, B.; Diao, Z.-F.;
Guo, C.-X.; He, L.-N. J. CO2 Utilization, 2013, 1, 60–68; (e) Manjolinho, F.; Arndt, M.; Gooßen,
K.; Gooßen, L. J. ACS Catal. 2012, 2, 2014–2021.
[2] Sakakura, T.; Choi, J.-C.; Yasuda, H. Chem. Rev. 2007, 107, 2365–2387.
[3] (a) Zhang, X.; Zhang, W.-Z; Shi, L.-L.; Zhu, C.; Jiang, J.-L.; Lu, X.-B. Tetrahedron, 2012, 68,
9085–9089; (b) Zhang, X.; Zhang, W.-Z.; Ren, X.; Zhang, L.-L.; Lu, X.-B. Org. Lett., 2011, 13,
2402–2405; (c) Liu, C.; Luo, Y.; Zhang, W.; Qu, J.; Lu, X. Organometallics, 2014, 33, 2984–2989;
(d) Cokoja, M.; Bruckmeier, C.; Rieger, B.; Herrmann, W. A.; Kühn, F. E. Angew. Chem. Int. Ed,
2011, 50: 8510-8537; (e) Boogaerts, I. I. F.; Nolan, S. P. C. J. Am. Chem. Soc. 2010, 132(26):
8858-8859.
[4] (a) Gooßen, L. J.; Rodríguez, N.; Manjolinho, F.; Lange, P. P. Adv. Synth. Catal., 2010, 352,
2913–2917; (b) Pan, C.; Luo, F.; Wang, W.; Ye, Z.; Cheng, J. Tetrahedron Lett., 2009, 50(35):
5044-5046.; (c) Yu, D.; Zhang, Y. Proc. Natl. Acad. Sci. U. S. A., 2010, 107, 20184–20189; (d)
Zhang, W. Z.; Li, W.-J.; Zhang, X.; Zhou, H.; Lu, X.-B. Org. Lett., 2010, 12, 4748–4751; (e)
Inamoto, K.; Asano, N.; Kobayashi, K.; Yonemoto, M.; Kondo, Y. Org. Biomol. Chem., 2012, 10,
1514–1516.
[5] (a) Ma, S.; Lu, X.. J. Org. Chem., 1993, 58(5): 1245-1250; (b) Otera, J.; Nishikido, J.; John
Wiley & Sons, 2009; (c) Rayabarapu, D. K.; Tunge, J. A. J. Am. Chem. Soc., 2005, 127(39):
13510-13511; (d) Yin, G.; Liu, G. Angew. Chem., Int. Ed., 2008, 47(29): 5442-5445; (e) Luo, T.;
Schreiber, S. L. J. Am. Chem. Soc., 2009, 131(15): 5667-5674.; (f) Tsujihara, T.; Takenaka, K.;
Onitsuka, K.; Hatanaka, M.; Sasai, H. J. Am. Chem. Soc., 2009, 131(10): 3452-3453.
15

ACCEPTED MANUSCRIPT
[6] Fukue, Y.; Oi, S.; Inoue, Y. J. Chem. Soc., Chem. Commun., 1994 (18): 2091-2091.
[7] (a) Yu, B.; Diao, Z. F.; Guo, C. X.; Zhong, C. L.; He, L. N.; Zhao, Y. N.; Wang, J. Q. Green
Chem., 2013, 15(9): 2401-2407. (b) Guo, C. X.; Yu, B.; Xie, J. N.; He, L. N. Green Chem., 2015,
17(1): 474-479. (c) Yu, B.; Xie, J. N.; Zhong, C. L.; Li, W.; He, L. N. ACS Catal., 2015, 5(7):
3940-3944. (d) Xie, J. N.; Yu, B.; Zhou, Z. H.; Fu, H. C.; Wang, N.; He, L. N. Tetrahedron Lett.,
2015, 56(50): 7059-7062.
[8] Yu, D.; Tan, M. X.; Zhang, Y. Adv. Synth. Catal, 2012, 354(6): 969-974.
[9] Li, S.; Sun, J.; Zhang, Z.; Xie, R.; Fang, X.; Zhou, M. Dalton Trans., 2016, 45, 10577-10584.
[10] Chen, G; Fu, C; Ma, S. Org. Lett., 2009, 11(13): 2900-2903.
[11] Parthasarathy K.; Han H.; Prakash C.; Cheng C-H. Chem. Commun., 2012, 48(52):
6580-6582.
[12] Arndt, M.; Risto, E.; Krause, T.; Gooßen, L. J. Chem. Cat. Chem., 2012, 4(4): 484-487.
[13] Mao, J.; Yang, X.; Yan, H.; He, Y.; Li, Y.; Zhao, J. Catal. Lett., 2016, 146(5): 886-892.
[14] Cao Q.; Hughes N. L.; Muldoon M. J. Chem. A Eur. J., 2016, 22(34): 11982-11985.
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