Sequential Ag-catalyzed carboxylative coupling/Ru-catalyzed cross-metathesis reactions for the synthesis of functionalized 2-alkynoates

Article abstract of DOI:10.1016/S1872-2067(12)60527-0

Sequential reactions can provide efficient access to a variety of important organic compounds that would be otherwise difficult to obtain using conventional methods and readily available starting materials. Based on the importance of 2-alkynoates in organic synthesis, the current research aimed to develop a method for the convenient synthesis of functionalized 2-alkynoates from terminal alkynes, CO₂, terminal alkene-derived bromides, and methyl acrylate using a combination of the carboxylative coupling and cross-metathesis reactions. The initial ligand-free silver-catalyzed carboxylative coupling reactions of a variety of different aryl-substituted terminal alkynes and CO₂ with 5-bromopentene and 6-bromohexene provided a series of 4-pentenyl 2-alkynoates and 5-hexenyl 2-alkynoates, respectively, in good yield. These resulting 2-alkynoates were further transformed into methyl (E)-6-acetylenecarboxy-2-hexenoates and (E)-7-acetylenecarboxy-2-heptenoates in moderate to good yields by their cross-metathesis reactions with methyl acrylate in the presence of the Grubbs-Hoveyda catalyst. All of the new products characterized spectroscopically.

Full text of DOI:10.1016/S1872-2067(12)60527-0

Chinese Journal of Catalysis 34 (2013) 1179–1186
ava i l a b l e a t w w w. s c i e n c ed i r e c t . c o m
j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e /c h n j c
Article
Sequential Ag‐catalyzed carboxylative coupling/Ru‐catalyzed
cross‐metathesis reactions for the synthesis of functionalized
2‐alkynoates
ZHANG Linlin, ZHANG Wenzhen*, SHI Linglong, REN Xiang, LÜ Xiaobing#
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, Liaoning China
A R T I C L E I N F O
A B S T R A C T
Article history:
Sequential reactions can provide efficient access to a variety of important organic compounds that
would be otherwise difficult to obtain using conventional methods and readily available starting
materials. Based on the importance of 2‐alkynoates in organic synthesis, the current research aimed
to develop a method for the convenient synthesis of functionalized 2‐alkynoates from terminal
alkynes, CO2, terminal alkene‐derived bromides, and methyl acrylate using a combination of the
carboxylative coupling and cross‐metathesis reactions. The initial ligand‐free silver‐catalyzed car‐
boxylative coupling reactions of a variety of different aryl‐substituted terminal alkynes and CO2 with
5‐bromopentene and 6‐bromohexene provided a series of 4‐pentenyl 2‐alkynoates and 5‐hexenyl
2‐alkynoates, respectively, in good yield. These resulting 2‐alkynoates were further transformed
into methyl (E)‐6‐acetylenecarboxy‐2‐hexenoates and (E)‐7‐acetylenecarboxy‐2‐heptenoates in
moderate to good yields by their cross‐metathesis reactions with methyl acrylate in the presence of
the Grubbs‐Hoveyda catalyst. All of the new products characterized spectroscopically.
© 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Received 7 December 2012
Accepted 7 January 2013
Published 20 June 2013
Keywords:
Carbon dioxide
Carboxylative coupling
Silver catalyst
Cross‐metathesis
Grubbs‐Hoveyda catalyst
Homogeneous catalysis
Published by Elsevier B.V. All rights reserved.
1. Introduction
forward methods for the synthesis of functionalized propiolic
acids and 2‐alkynoates [23,34]. In 2010, we reported the highly
Methods for the synthesis of high value‐added fine chemi‐
cals using carbon dioxide as a raw material have been the sub‐
ject of increasing levels of attention during the course of the
last two decades, because carbon dioxide is an abundant, inex‐
pensive, and nontoxic renewable C1 feedstock [1–7]. In the
presence of suitable homogeneous transition‐metal catalysts,
carbon dioxide can be efficiently transformed into a variety of
different functionalized carboxylic acids and related derivatives
[8–22]. The copper‐ and silver‐catalyzed direct carboxylation
reactions of terminal alkynes using CO2 as the carboxylative
agent have recently been established as efficient and straight‐
selective synthesis of allylic 2‐alkynoates according to the car‐
boxylative coupling reaction of terminal alkynes, CO2, and al‐
lylic chlorides using a 10 mol% loading of (IPr)CuCl (IPr =
1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) as the cata‐
lyst [28]. In a later publication, we also disclosed a convenient
method for the selective synthesis of functionalized propiolic
acids via the direct carboxylation of terminal alkynes with CO2
under ligand‐free conditions using only a 1 mol% loading of AgI
as the catalyst [30]. More recently, this simple silver‐based
catalytic system has also been used as a catalyst for the highly
efficient and selective carboxylative coupling reaction of a vari‐
*Corresponding author. Tel: +86‐411‐84986257; Fax: +86‐411‐84986256; E‐mail: zhangwz@dlut.edu.cn
# Corresponding author. Tel: +86‐411‐84986255; Fax: +86‐411‐84986256; E‐mail: lxb‐1999@163.com
This work was supported by the National Natural Science Foundation of China (20802007, 21111120073), the Fundamental Research Funds for the
Central Universities (DUT12LK47), and the Scientific Research Fund of Liaoning Provincial Education Department (L2012024).
DOI: 10.1016/S1872‐2067(12)60527‐0 | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 34, No. 6, June 2013

ZHANG Linlin et al. / Chinese Journal of Catalysis 34 (2013) 1179–1186
ety of different terminal alkynes, CO2, and chloride compounds
tilled from CaH2 at 60 °C under reduced pressure and stored
over 4A molecular sieves. NMR spectra (1H NMR, 400 MHz; 13
to yield 2‐alkynoates exclusively. Furthermore, the ligand‐free
silver catalyst system showed significantly enhanced levels of
activity and selectivity at much lower catalyst loadings than the
corresponding copper catalyst system [34].
C
NMR, 100 MHz) were recorded on a Bruker AvanceII 400M
type spectrometer (Bruker). Multiplicity abbreviations: s =
singlet, d = doublet, t = triplet, q = quartet, m = multiplet. High
resolution mass spectra (HRMS) were recorded on a Q‐TOF
mass spectrometer (Micromass, Wythenshawe, UK) equipped
with Z‐spray ionization source. Infrared (IR) spectra were
measured using a Nicolet NEXUS FT‐IR spectrophotometer. The
Over the past two decades, olefin metathesis has become
one of the most powerful and broadly applicable tools for the
construction of carbon‐carbon double bonds in organic synthe‐
sis [35–39]. In contrast, the cross‐metathesis reaction has not
been developed to the same extent because of the lack of effi‐
cient catalysts capable of controlling the chemoselectivity and
stereoselectivity of the reaction [40–44]. Interestingly, howev‐
er, as a convenient method to gain functionalized and higher
olefins from simple alkene precursors, cross‐metathesis has
emerged as a powerful synthetic strategy and played a crucial
role in the total syntheses of many natural products and bio‐
logically active compounds, with the utility of technique being
significantly enhanced by the development of highly active and
selective catalysts [45–50].
second‐generation Grubbs catalyst
5
[57,58] and
Grubbs‐Hoveyda catalyst 6 [59] were synthesized according to
the reported procedures. Carbon dioxide (99.999%), commer‐
cially available terminal alkynes, bromide compounds, silver(I)
salt, methyl acrylate, and other all of the other reagents were
used without further purification.
2.1. General procedure for the Ag‐catalyzed carboxylative
coupling of terminal alkynes, CO2, and bromides
Based on the importance of 2‐alkynoates in organic synthe‐
sis [51–55] and the success of olefin metathesis in a recent
study [56], our attentions became focused on the development
of a sequential carboxylative coupling/cross‐metathesis reac‐
tion sequence for the synthesis of functionalized 2‐alkynoates
from CO2, and other simple and readily available starting mate‐
rials. With this goal in mind, it was envisaged that the carboxy‐
lative coupling of terminal alkynes, CO2, and terminal al‐
kene‐derived halides would provide access to terminal al‐
kene‐derived 2‐alkynoates that could then be subjected to the
conditions of the cross‐metathesis reactions with an olefin of
lower reactivity to give functionalized 2‐alkynoates, which
would be otherwise difficult to obtain using conventional
methods (Scheme 1). Herein, we present an efficient and con‐
venient synthetic protocol for the selective synthesis of func‐
tionalized 2‐alkynoates in good yields from terminal alkynes,
CO2, terminal alkene‐derived bromides, and methyl acrylate.
The two‐steps of this synthetic procedure involved the sil‐
ver‐catalyzed carboxylative coupling and ruthenium‐catalyzed
cross‐metathesis reactions.
A 70 ml oven dried autoclave containing a stirrer bar was
charged the AgI (0.5 mg, 0.002 mmol) and Cs2CO3 (978 mg, 3.0
mmol). The autoclave was purged three time with CO2 and the
terminal alkynes 1 (2.0 mmol), bromides 2 (3.0 mmol), and dry
DMF (20 ml) were then added sequentially via a syringe. The
autoclave was then sealed and pressurized to the appropriate
pressure with CO2. The reaction mixture was then stirred at 60
°C for 24 h and the autoclave was cooled to room temperature
and the remaining CO2 slowly vented from the system. The
reaction mixture was diluted with water (30 ml) and extracted
with ethyl acetate (30 ml × 3). The combined organic layers
were washed with water and brine, dried over Na2SO4, and
filtered. The solvent was removed under vacuum. The product
was isolated by column chromatography on silica gel.
All new products prepared by the above procedure were
characterized spectroscopically as shown below.
4‐Pentenyl phenylpropiolate (3a). 69% isolated yield. Oil.
1H NMR (400 MHz, CDCl3): δ 7.61–7.36 (m, 5H, 5CH), 5.82 (ddt,
J = 16.9, 10.2, 6.7 Hz, 1H, CH=CH2), 5.08 (d, J = 16.9 Hz, 1H, trans
CH=CH2), 5.02 (d, J = 10.2 Hz, 1H, cis CH=CH2), 4.25 (t, J = 6.7 Hz,
2H, OCH2), 2.21–2.16 (m, 2H, CHCH2), 1.86–1.79 (m, 2H,
CH2CH2CH2). 13C NMR (100 MHz, CDCl3): δ 154.10 (C‐O), 137.16
(vinyl C), 132.97 (aromatic C), 130.62 (aromatic C), 128.57
(aromatic C), 119.64 (aromatic C), 115.56 (vinyl C), 86.16 (al‐
kynyl C), 80.68 (alkynyl C), 65.42 (OCH2), 29.89 (CH2), 27.60
(CH2). IR (neat, cm–1): 2959, 2223, 1709, 1640, 1490, 1285,
2. Experimental
Unless otherwise statement, all manipulations were per‐
formed using standard Schlenk techniques under a dry argon
or CO2 atmosphere. N,N‐Dimethylformamide (DMF) was dis‐
R
carboxylative coupling
O
+
CO2
X
n
O
n
O
R
R'
O
R'
n
cross-metathesis
R
Scheme 1. Synthesis of functionalized 2‐alkynoates via the sequential carboxylative coupling/cross‐metathesis reactions.

ZHANG Linlin et al. / Chinese Journal of Catalysis 34 (2013) 1179–1186
758, 689. HRMS (ESI, m/z) calcd. for C14H14O2Na [M+Na]+:
237.0891; found: 237.0892.
trans CH=CH2), 5.00 (d, J = 10.2 Hz, 1H, cis CH=CH2), 4.16 (t, J =
6.7 Hz, 2H, OCH2), 2.90 (t, J = 7.6 Hz, 2H, CH2), 2.62 (t, J = 7.6 Hz,
2H, CH2), 2.17–2.12 (m, 2H, CHCH2), 1.81–1.74 (m, 2H,
CH2CH2CH2). 13C NMR (100 MHz, CDCl3): δ 153.76 (C‐O), 139.63
(aromatic C), 137.21 (vinyl C), 128.59 (aromatic C), 128.38
(aromatic C), 126.67 (aromatic C), 115.53 (vinyl C), 88.40 (al‐
kynyl C), 73.74 (alkynyl C), 65.16 (OCH2), 33.85 (CH2), 29.91
(CH2), 27.56 (CH2), 20.88 (CH2). IR (neat, cm–1): 2954, 2237,
1709, 1258, 1070, 750, 699. HRMS (ESI, m/z) calcd. for
C16H18O2Na [M+Na]+: 265.1204; found: 265.1211.
4‐Pentenyl 4‐methylphenylpropiolate (3b). 87% isolated
1
yield. Oil. H NMR (400 MHz, CDCl3): δ 7.49 (d, J = 8.0 Hz, 2H,
2CH), 7.18 (d, J = 8.0 Hz, 2H, 2CH), 5.82 (ddt, J = 16.9, 10.2, 6.7
Hz, 1H, CH=CH2), 5.07 (d, J = 16.9 Hz, 1H, trans CH=CH2), 5.02
(d, J = 10.2 Hz, 1H, cis CH=CH2), 4.24 (t, J = 6.7 Hz, 2H, OCH2),
2.38 (s, 2H, CH3), 2.21–2.16 (m, 2H, CHCH2), 1.86–1.79 (m, 2H,
CH2CH2CH2). 13C NMR (100 MHz, CDCl3): δ 154.25 (C‐O), 141.27
(aromatic C), 137.19 (vinyl C), 132.98 (aromatic C), 129.36
(aromatic C), 116.51 (aromatic C), 115.53 (vinyl C), 86.72 (al‐
kynyl C), 80.33 (alkynyl C), 65.35 (OCH2), 29.90 (CH2), 27.62
(CH2), 21.69 (CH3). IR (neat, cm–1): 2957, 2217, 1708, 1641,
1508, 1290, 817, 748. HRMS (ESI, m/z) calcd. for C15H16O2Na
[M+Na]+: 251.1048; found: 251.1046.
4‐Pentenyl 2‐nonynoate (3g). 64% isolated yield. Oil. 1H
NMR (400 MHz, CDCl3): δ 5.80 (ddt, J = 16.9, 10.2, 6.7 Hz, 1H,
CH=CH2), 5.04 (d, J = 16.9 Hz, 1H, trans CH=CH2), 5.00 (d, J =
10.2 Hz, 1H, cis CH=CH2), 4.17 (t, J = 6.7 Hz, 2H, OCH2), 2.33 (t, J
= 7.2 Hz, 2H, CH2), 2.17–2.12 (m, 2H, CHCH2), 1.81–1.74 (m, 2H,
CH2CH2CH2), 1.61–1.29 (m, 8H, 4CH2), 0.89 (t, J = 6.5 Hz, 3H,
CH3). 13C NMR (100 MHz, CDCl3): δ 153.93 (C‐O), 137.17 (vinyl
C), 115.43 (vinyl C), 89.60 (alkynyl C), 73.07 (alkynyl C), 65.09
(OCH2), 31.17 (CH2), 29.86 (CH2), 28.48 (CH2), 27.53 (CH2),
27.47 (CH2), 22.42 (CH2), 18.65 (CH2), 13.96 (CH3). IR (neat,
cm–1): 2959, 2236, 1713, 1642, 1258, 1083. HRMS (ESI, m/z)
calcd. for C14H22O2Na [M+Na]+: 245.1517; found: 245.1521.
5‐Hexenyl phenylpropiolate (4a). 75% isolated yield. Oil. 1H
NMR (400 MHz, CDCl3): δ 7.60–7.36 (m, 5H, 5CH), 5.80 (ddt, J =
16.9, 10.2, 6.7 Hz, 1H, CH=CH2), 5.04 (d, J = 16.9 Hz, 1H, trans
CH=CH2), 4.98 (d, J = 10.2 Hz, 1H, cis CH=CH2), 4.25 (t, J = 6.7 Hz,
2H, OCH2), 2.14–2.11 (m, 2H, CHCH2), 1.76–1.72 (m, 2H,
CH2CH2CH2), 1.54–1.50 (m, 2H, CH2). 13C NMR (100 MHz,
CDCl3): δ 154.17 (C‐O), 138.19 (vinyl C), 132.98 (aromatic C),
130.63 (aromatic C), 128.58 (aromatic C), 119.63 (aromatic C),
115.00 (vinyl C), 86.12 (alkynyl C), 80.70 (alkynyl C), 65.99
(OCH2), 33.24 (CH2), 27.88 (CH2), 25.07 (CH2). IR (neat, cm–1):
2936, 2221, 1709, 1640, 1490, 1286, 758, 689. HRMS (ESI,
m/z) calcd. for C15H16O2Na [M+Na]+: 251.1048; found:
251.1045.
5‐Hexenyl 4‐methylphenylpropiolate (4b). 76% isolated
yield. Oil. 1H NMR (400 MHz, CDCl3): δ 7.50 (d, J = 8.0 Hz, 2H,
2CH), 7.19 (d, J = 8.0 Hz, 2H, 2CH), 5.82 (ddt, J = 16.9, 10.2, 6.7
Hz, 1H, CH=CH2), 5.04 (d, J = 16.9 Hz, 1H, trans CH=CH2), 4.99
(d, J = 10.2 Hz, 1H, cis CH=CH2), 4.24 (t, J = 6.7 Hz, 2H, OCH2),
2.39 (s, 2H, CH3), 2.15–2.09 (m, 2H, CHCH2), 1.76–1.71 (m, 2H,
CH2CH2CH2), 1.56–1.50 (m, 2H, CH2). 13C NMR (100 MHz,
CDCl3): δ 154.25 (C‐O), 141.23 (aromatic C), 138.17 (vinyl C),
132.95 (aromatic C), 129.35 (aromatic C), 116.52 (aromatic C),
114.95 (vinyl C), 86.62 (alkynyl C), 80.38 (alkynyl C), 65.85
(OCH2), 33.23 (CH2), 27.90 (CH2), 25.08 (CH2), 21.66 (CH3). IR
(neat, cm–1): 2937, 2218, 1709, 1641, 1509, 1290, 817, 748.
HRMS (ESI, m/z) calcd. for C16H18O2Na [M+Na]+: 265.1204;
found: 265.1211.
4‐Pentenyl 4‐methoxylphenylpropiolate (3c). 91% isolated
1
yield. Oil. H NMR (400 MHz, CDCl3): δ 7.54 (d, J = 8.7 Hz, 2H,
2CH), 6.88 (d, J = 8.7 Hz, 2H, 2CH), 5.82 (ddt, J = 16.9, 10.2, 6.7
Hz, 1H, CH=CH2), 5.07 (d, J = 16.9 Hz, 1H, trans CH=CH2), 5.02
(d, J = 10.2 Hz, 1H, cis CH=CH2), 4.23 (t, J = 6.7 Hz, 2H, OCH2),
3.82 (s, 2H, CH3), 2.20–2.15 (m, 2H, CHCH2), 1.85–1.78 (m, 2H,
CH2CH2CH2). 13C NMR (100 MHz, CDCl3): δ 161.50 (aromatic C),
154.37 (C‐O), 137.22 (vinyl C), 134.92 (aromatic C), 115.52
(vinyl C), 114.28 (aromatic C), 111.36 (aromatic C), 87.02 (al‐
kynyl C), 80.10 (alkynyl C), 65.27 (OCH2), 55.37 (OCH3), 29.91
(CH2), 27.62 (CH2). IR (neat, cm–1): 2959, 2210, 1705, 1605,
1510, 1286, 834, 747. HRMS (ESI, m/z) calcd. for C15H16O3Na
[M+Na]+: 267.0997; found: 267.0993.
4‐Pentenyl 4‐tert‐butylphenylpropiolate (3d). 87% isolated
1
yield. Oil. H NMR (400 MHz, CDCl3): δ 7.54 (d, J = 8.2 Hz, 2H,
2CH), 7.40 (d, J = 8.2 Hz, 2H, 2CH), 5.82 (ddt, J = 16.9, 10.2, 6.7
Hz, 1H, CH=CH2), 5.08 (d, J = 16.9 Hz, 1H, trans CH=CH2), 5.02
(d, J = 10.2 Hz, 1H, cis CH=CH2), 4.25 (t, J = 6.7 Hz, 2H, OCH2),
2.21–2.16 (m, 2H, CHCH2), 1.85–1.79 (m, 2H, CH2CH2CH2), 1.32
(s, 9H, CH3). 13C NMR (100 MHz, CDCl3): δ 154.26 (aromatic C),
154.23 (C‐O), 137.18 (vinyl C), 132.89 (aromatic C), 125.64
(aromatic C), 116.53 (aromatic C), 115.55 (vinyl C), 86.65 (al‐
kynyl C), 80.35 (alkynyl C), 65.32 (OCH2), 35.01 (C(CH3)3),
31.04 (CH3), 29.92 (CH2), 27.61 (CH2). IR (neat, cm–1): 2964,
2220, 1709, 1290, 1200, 1117, 837, 748. HRMS (ESI, m/z)
calcd. for C18H22O2Na [M+Na]+: 293.1517; found: 293.1519.
4‐Pentenyl 4‐trifluoromethylphenylpropiolate (3e). 85%
isolated yield. Oil. 1H NMR (400 MHz, CDCl3): δ 7.70 (d, J = 8.1
Hz, 2H, 2CH), 7.64 (d, J = 8.1 Hz, 2H, 2CH), 5.82 (ddt, J = 16.9,
10.2, 6.7 Hz, 1H, CH=CH2), 5.08 (d, J = 16.9 Hz, 1H, trans
CH=CH2), 5.02 (d, J = 10.2 Hz, 1H, cis CH=CH2), 4.27 (t, J = 6.7 Hz,
2H, OCH2), 2.21–2.16 (m, 2H, CHCH2), 1.87–1.80 (m, 2H,
CH2CH2CH2). 13C NMR (100 MHz, CDCl3): δ 153.78 (C‐O), 137.19
(vinyl C), 133.29 (aromatic C), 132.49 (aromatic C), 132.14
(aromatic C), 125.67 (aromatic C), 123.63 (CF3), 115.78 (vinyl
C), 84.06 (alkynyl C), 82.40 (alkynyl C), 65.87 (OCH2), 30.01
(CH2), 27.70 (CH2). IR (neat, cm–1): 2960, 2232, 1715, 1324,
1288, 1197, 1178, 1132, 1067, 844, 748. HRMS (ESI, m/z)
calcd. for C15H13O2F3Na [M+Na]+: 305.0765; found: 305.0774.
4‐Pentenyl 5‐phenyl‐2‐pentynoate (3f). 65% isolated yield.
Oil. 1H NMR (400 MHz, CDCl3): δ 7.33–7.21 (m, 5H, 5CH), 5.80
(ddt, J = 16.9, 10.2, 6.7 Hz, 1H, CH=CH2), 5.05 (d, J = 16.9 Hz, 1H,
5‐Hexenyl 4‐methoxylphenylpropiolate (4c). 86% isolated
1
yield. Oil. H NMR (400 MHz, CDCl3): δ 7.45 (d, J = 8.7 Hz, 2H,
2CH), 6.79 (d, J = 8.7 Hz, 2H, 2CH), 5.72 (ddt, J = 16.9, 10.2, 6.7
Hz, 1H, CH=CH2), 4.95 (d, J = 16.9 Hz, 1H, trans CH=CH2), 4.89
(d, J = 10.2 Hz, 1H, cis CH=CH2), 4.14 (t, J = 6.7 Hz, 2H, OCH2),
3.74 (s, 2H, CH3), 2.05–1.99 (m, 2H, CHCH2), 1.67–1.60 (m, 2H,
CH2CH2CH2), 1.46–1.38 (m, 2H, CH2). 13C NMR (100 MHz,
CDCl3): δ 161.49 (aromatic C), 154.39 (C‐O), 138.20 (vinyl C),

ZHANG Linlin et al. / Chinese Journal of Catalysis 34 (2013) 1179–1186
134.90 (aromatic C), 114.94 (vinyl C), 114.27 (aromatic C),
(CH2), 18.63 (CH2), 13.96 (CH3). IR (neat, cm–1): 2954, 2236,
1713, 1641, 1250, 1083. HRMS (ESI, m/z) calcd. for C15H24O2Na
[M+Na]+: 259.1674; found: 259.1683.
111.37 (aromatic C), 86.94 (alkynyl C), 80.14 (alkynyl C), 65.78
(OCH2), 55.35 (OCH3), 33.23 (CH2), 27.91 (CH2), 25.08 (CH2). IR
(neat, cm–1): 2937, 2214, 1705, 1604, 1510, 1288, 834, 747.
HRMS (ESI, m/z) calcd. for C16H18O3Na [M+Na]+: 281.1154;
found: 281.1162.
2.2. General procedure for the cross‐metathesis reaction of the
terminal alkene‐derived 2‐alkynoates with methyl acrylate
5‐Hexenyl 4‐tert‐butylphenylpropiolate (4d). 88% isolated
yield. Oil. 1H NMR (400 MHz, CDCl3): δ 7.53 (d, J = 8.5 Hz, 2H,
2CH), 7.39 (d, J = 8.5 Hz, 2H, 2CH), 5.81 (ddt, J = 16.9, 10.2, 6.7
Hz, 1H, CH=CH2), 5.04 (d, J = 16.9 Hz, 1H, trans CH=CH2), 4.98
(d, J = 10.2 Hz, 1H, cis CH=CH2), 4.24 (t, J = 6.6 Hz, 2H, OCH2),
2.14–2.09 (m, 2H, CHCH2), 1.77–1.70 (m, 2H, CH2CH2CH2),
1.56–1.48 (m, 2H, CH2), 1.32 (s, 9H, CH3). 13C NMR (100 MHz,
CDCl3): δ 154.18 (aromatic C), 154.16 (C‐O), 138.11 (vinyl C),
132.85 (aromatic C), 125.60 (aromatic C), 116.58 (aromatic C),
114.97 (vinyl C), 86.49 (alkynyl C), 80.43 (alkynyl C), 65.78
(OCH2), 34.96 (C(CH3)3), 33.24 (CH3), 31.01 (CH2), 27.91 (CH2),
25.08 (CH2). IR (neat, cm–1): 2964, 2220, 1709, 1290, 1201,
1175, 837, 748. HRMS (ESI, m/z) calcd. for C19H24O2Na
[M+Na]+: 307.1674; found: 307.1678.
5‐Hexenyl 4‐trifluoromethylphenylpropiolate (4e). 83%
isolated yield. Oil. 1H NMR (400 MHz, CDCl3): δ 7.70 (d, J = 8.1
Hz, 2H, 2CH), 7.64 (d, J = 8.1 Hz, 2H, 2CH), 5.81 (ddt, J = 16.9,
10.2, 6.7 Hz, 1H, CH=CH2), 5.03 (d, J = 16.9 Hz, 1H, trans
CH=CH2), 4.99 (d, J = 10.2 Hz, 1H, cis CH=CH2), 4.26 (t, J = 6.7 Hz,
2H, OCH2), 2.14–2.09 (m, 2H, CHCH2), 1.78–1.71 (m, 2H,
CH2CH2CH2), 1.56–1.48 (m, 2H, CH2). 13C NMR (100 MHz,
CDCl3): δ 153.68 (C‐O), 138.11 (vinyl C), 133.14 (aromatic C),
132.33 (aromatic C), 132.00 (aromatic C), 125.51 (aromatic C),
123.50 (CF3), 115.02 (vinyl C), 83.87 (alkynyl C), 82.29 (alkynyl
C), 66.27 (OCH2), 33.21 (CH2), 27.85 (CH2), 25.06 (CH2). IR
(neat, cm–1): 2938, 2228, 1716, 1324, 1289, 1197, 1177, 1133,
1068, 844, 748. HRMS (ESI, m/z) calcd. for C16H15O2F3Na
[M+Na]+: 319.0922; found: 319.0926.
5‐Hexenyl 5‐phenyl‐2‐pentynoate (4f). 66% isolated yield.
Oil. 1H NMR (400 MHz, CDCl3): δ 7.33–7.21 (m, 5H, 5CH), 5.80
(ddt, J = 16.9, 10.2, 6.7 Hz, 1H, CH=CH2), 5.03 (d, J = 16.9 Hz, 1H,
trans CH=CH2), 4.98 (d, J = 10.2 Hz, 1H, cis CH=CH2), 4.16 (t, J =
6.6 Hz, 2H, OCH2), 2.90 (t, J = 7.6 Hz, 2H, CH2), 2.63 (t, J = 7.7 Hz,
2H, CH2), 2.12–2.06 (m, 2H, CHCH2), 1.72–1.65 (m, 2H,
CH2CH2CH2), 1.51–1.44 (m, 2H, CH2). 13C NMR (100 MHz,
CDCl3): δ 153.80 (C‐O), 139.64 (aromatic C), 138.21 (vinyl C),
128.58 (aromatic C), 128.37 (aromatic C), 126.66 (aromatic C),
114.97 (vinyl C), 88.34 (alkynyl C), 73.77 (alkynyl C), 65.71
(OCH2), 33.86 (CH2), 33.24 (CH2), 27.85 (CH2), 25.08 (CH2),
20.88 (CH2). IR (neat, cm–1): 2934, 2236, 1709, 1252, 1070,
750, 699. HRMS (ESI, m/z) calcd. for C17H20O2Na [M+Na]+:
279.1361; found: 279.1372.
5‐Hexenyl 2‐nonynoate (4g). 59% isolated yield. Oil. 1H
NMR (400 MHz, CDCl3): δ 5.81 (ddt, J = 16.9, 10.2, 6.7 Hz, 1H,
CH=CH2), 5.02 (d, J = 16.9 Hz, 1H, trans CH=CH2), 4.97 (d, J =
10.2 Hz, 1H, cis CH=CH2), 4.16 (t, J = 6.7 Hz, 2H, OCH2), 2.33 (t, J
= 7.1 Hz, 2H, CH2), 2.11–2.06 (m, 2H, CHCH2), 1.72–1.30 (m,
12H, 6CH2), 0.89 (t, J = 6.5 Hz, 3H, CH3). 13C NMR (100 MHz,
CDCl3): δ 153.95 (C‐O), 138.15 (vinyl C), 114.87 (vinyl C), 89.50
(alkynyl C), 73.09 (alkynyl C), 65.61 (OCH2), 33.20 (CH2), 31.17
(CH2), 28.48 (CH2), 27.80 (CH2), 27.47 (CH2), 25.02 (CH2), 22.42
To a solution of the terminal alkene‐derived 2‐alkynoates 3
or 4 (0.2 mmol) in toluene (0.1 mol/L) in a Schlenk tube con‐
taining a stirrer bar were added methyl acrylates (50 equiv)
and the Grubbs‐Hoveyda catalyst (5 mol%). The resulting reac‐
tion mixtures were heated under an argon atmosphere at 60 °C
for 12 h. The mixtures were then quickly filtered through silica
and the solvent removed under reduced pressure to give the
crude residues, which were purified by flash column chroma‐
tography on silica gel to provide the cross‐metathesis products
8 or 9.
All new products prepared by the above procedure were
characterized spectroscopically as shown below.
Methyl (E)‐6‐phenylacetylenecarboxy‐2‐hexenoate (8a).
31% isolated yield. Oil. 1H NMR (400 MHz, CDCl3): δ 7.60–7.36
(m, 5H, 5CH), 6.97 (dt, J = 15.6, 6.9 Hz, 1H, CHCH2), 5.89 (d, J =
15.6, 1H, CHCO), 4.26 (t, J = 6.9 Hz, 2H, OCH2), 3.73 (s, 3H,
OCH3), 2.38–2.32 (m, 2H, CHCH2), 1.93–1.86 (m, 2H,
CH2CH2CH2). 13C NMR (100 MHz, CDCl3): δ 166.84 (C‐O), 154.00
(C‐O), 147.51 (alkenyl C), 133.01 (aromatic C), 130.69 (aro‐
matic C), 128.58 (aromatic C), 121.89 (alkenyl C), 119.55 (aro‐
matic C), 86.54 (alkynyl C), 80.47 (alkynyl C), 64.98 (OCH2),
51.47 (OCH3), 28.52 (CH2), 26.91 (CH2). IR (neat, cm–1): 2956,
2924, 2219, 1716, 1660, 1463, 1278, 1261, 1024, 757, 689.
HRMS (ESI, m/z) calcd. for C16H16O4Na [M+Na]+: 295.0946;
found: 295.0935.
Methyl (E)‐6‐(4‐methylphenyl)acetylenecarboxy‐2‐hexen‐
oate (8b). 63% isolated yield. Oil. 1H NMR (400 MHz, CDCl3): δ
7.49 (d, J = 8.0 Hz, 2H, 2CH), 7.19 (d, J = 8.0 Hz, 2H, 2CH), 6.98
(dt, J = 15.7, 6.4 Hz, 1H, CHCH2), 5.89 (d, J = 15.7, 1H, CHCO),
4.25 (t, J = 6.4 Hz, 2H, OCH2), 3.73 (s, 3H, OCH3), 2.39 (s, 3H,
CH3), 2.39–2.33 (m, 2H, CHCH2), 1.93–1.86 (m, 2H, CH2CH2CH2).
13C NMR (100 MHz, CDCl3): δ 167.01 (C‐O), 154.30 (C‐O),
147.74 (alkenyl C), 141.54 (aromatic C), 133.18 (aromatic C),
129.53 (aromatic C), 122.01 (alkenyl C), 116.54 (aromatic C),
87.26 (alkynyl C), 80.29 (alkynyl C), 65.07 (OCH2), 51.68
(OCH3), 29.87 (CH2), 28.70 (CH2), 27.07 (CH3). IR (neat, cm–1):
2950, 2924, 2214, 1709, 1659, 1436, 1382, 1289, 1168, 1034,
817, 747. HRMS (ESI, m/z) calcd. for C17H18O4Na [M+Na]+:
309.1103; found: 309.1102.
Methyl (E)‐6‐(4‐methoxylphenyl)acetylenecarboxy‐2‐hex‐
enoate (8c). 68% isolated yield. Oil. 1H NMR (400 MHz, CDCl3):
δ 7.54 (d, J = 8.9 Hz, 2H, 2CH), 6.97 (dt, J = 15.6, 6.9 Hz, 1H,
CHCH2), 6.89 (d, J = 8.9 Hz, 2H, 2CH), 5.88 (d, J = 15.6, 1H,
CHCO), 4.24 (t, J = 6.9 Hz, 2H, OCH2), 3.84 (s, 3H, OCH3), 3.73 (s,
3H, OCH3), 2.38–2.32 (m, 2H, CHCH2), 1.92–1.85 (m, 2H,
CH2CH2CH2). 13C NMR (100 MHz, CDCl3): δ 167.00 (C‐O), 161.72
(aromatic C), 154.41 (C‐O), 147.76 (alkenyl C), 135.13 (aro‐
matic C), 121.98 (alkenyl C), 114.45 (aromatic C), 111.43 (aro‐
matic C), 87.55 (alkynyl C), 80.09 (alkynyl C), 64.98 (OCH2),
55.56 (OCH3), 51.64 (OCH3), 28.70 (CH2), 27.08 (CH2). IR (neat,

ZHANG Linlin et al. / Chinese Journal of Catalysis 34 (2013) 1179–1186
cm–1) : 2955, 2922, 2212, 1708, 1658, 1604, 1462, 1288, 1165,
1026, 835, 746. HRMS (ESI, m/z) calcd. for C17H18O5Na
[M+Na]+: 325.1052; found: 325.1058.
Methyl (E)‐7‐(4‐methoxylphenyl)acetylenecarboxy‐2‐hep‐
tenoate (9c). 56% isolated yield. Oil. 1H NMR (400 MHz, CDCl3):
δ 7.55 (d, J = 8.8 Hz, 2H, 2CH), 6.97 (dt, J = 15.6, 7.0 Hz, 1H,
CHCH2), 6.89 (d, J = 8.8 Hz, 2H, 2CH), 5.86 (d, J = 15.6, 1H,
CHCO), 4.23 (t, J = 7.0 Hz, 2H, OCH2), 3.84 (s, 3H, OCH3), 3.73 (s,
3H, OCH3), 2.30–2.25 (m, 2H, CHCH2), 1.78–1.56 (m, 4H, CH2).
13C NMR (100 MHz, CDCl3): δ 167.16 (C‐O), 161.68 (aromatic
C), 154.53 (C‐O), 148.78 (alkenyl C), 135.12 (aromatic C),
121.61 (alkenyl C), 114.44 (aromatic C), 111.49 (aromatic C),
87.38 (alkynyl C), 80.17 (alkynyl C), 65.60 (OCH2), 55.56
(OCH3), 51.62 (OCH3), 31.82 (CH2), 28.10 (CH2), 24.53 (CH2). IR
(neat, cm–1): 2924, 2850, 2212, 1705, 1657, 1604, 1510, 1460,
1286, 1163, 1029, 835, 747. HRMS (ESI, m/z) calcd. for
C18H20O5Na [M+Na]+: 339.1208; found: 339.1216.
Methyl (E)‐7‐(4‐tert‐butylphenyl)acetylenecarboxy‐2‐hep‐
tenoate (9d). 77% isolated yield. Oil. 1H NMR (400 MHz, CDCl3):
δ 7.58 (d, J = 8.7 Hz, 2H, 2CH), 7.39 (d, J = 8.7 Hz, 2H, 2CH), 6.97
(dt, J = 15.6, 6.4 Hz, 1H, CHCH2), 5.86 (d, J = 15.6, 1H, CHCO),
4.24 (t, J = 6.4 Hz, 2H, OCH2), 3.73 (s, 3H, OCH3), 2.30–2.24 (m,
2H, CHCH2), 1.77–1.72 (m, 2H, CH2CH2CH2), 1.63–1.56 (m, 2H,
CH2) 1.32 (s, 9H, CH3). 13C NMR (100 MHz, CDCl3): δ 167.08
(C‐O), 154.47 (C‐O), 154.37 (aromatic C), 148.70 (alkenyl C),
133.02 (aromatic C), 125.75 (aromatic C), 121.60 (alkenyl C),
116.58 (aromatic C), 87.02 (alkynyl C), 80.33 (alkynyl C), 65.64
(OCH2), 51.55 (OCH3), 35.17 (C(CH3)3), 31.77 (CH2), 31.16
(CH3), 28.05 (CH2), 24.50 (CH2). IR (neat, cm–1): 2962, 2216,
1716, 1660, 1436, 1290, 1201, 1170, 1034, 838, 747. HRMS
(ESI, m/z) calcd. for C21H26O4Na [M+Na]+: 365.1729; found:
365.1717.
Methyl (E)‐7‐(4‐trifluoromethyl)acetylenecarboxy‐2‐hep‐
tenoate (9e). 44% isolated yield. Oil. 1H NMR (400 MHz, CDCl3):
δ 7.71 (d, J = 8.2 Hz, 2H, 2CH), 7.65 (d, J = 8.2 Hz, 2H, 2CH), 6.97
(dt, J = 15.5, 7.0 Hz, 1H, CHCH2), 5.86 (d, J = 15.5, 1H, CHCO),
4.26 (t, J = 7.0 Hz, 2H, OCH2), 3.73 (s, 3H, OCH3), 2.31–2.25 (m,
2H, CHCH2), 1.78–1.59 (m, 2H, 2CH2). 13C NMR (100 MHz,
CDCl3): δ 166.98 (C‐O), 153.62 (C‐O), 148.49 (alkenyl C), 133.17
(aromatic C), 132.38 (aromatic C), 132.06 (aromatic C), 125.53
(aromatic C), 123.43 (CF3), 121.54 (alkenyl C), 84.10 (alkynyl
C), 82.15 (alkynyl C), 65.90 (OCH2), 51.47 (OCH3), 31.62 (CH2).
29.71 (CH2), 27.88 (CH2). IR (neat, cm–1): 2951, 2228, 1717,
1658, 1324, 1288, 1174, 1067, 845, 748. HRMS (ESI, m/z)
calcd. for C18H17O4NaF3 [M+Na]+: 377.0977; found: 377.0972.
Methyl (E)‐6‐(4‐tert‐butylphenyl)acetylenecarboxy‐2‐hex‐
enoate (8d). 89% isolated yield. Oil. 1H NMR (400 MHz, CDCl3):
δ 7.53 (d, J = 8.2 Hz, 2H, 2CH), 7.40 (d, J = 8.2 Hz, 2H, 2CH), 6.97
(dt, J = 15.7, 6.4 Hz, 1H, CHCH2), 5.89 (d, J = 15.7, 1H, CHCO),
4.25 (t, J = 6.4 Hz, 2H, OCH2), 3.73 (s, 3H, OCH3), 2.38–2.33 (m,
2H, CHCH2), 1.93–1.86 (m, 2H, CH2CH2CH2), 1.32 (s, 9H, CH3).
13C NMR (100 MHz, CDCl3): δ 166.97 (C‐O), 154.54 (C‐O),
154.29 (aromatic C), 147.70 (alkenyl C), 133.04 (aromatic C),
125.77 (aromatic C), 121.98 (alkenyl C), 116.52 (aromatic C),
87.21 (alkynyl C), 80.23 (alkynyl C), 65.03 (OCH2), 51.59
(OCH3), 35.19 (C(CH3)3), 31.17 (CH3), 28.67 (CH2), 27.04 (CH2).
IR (neat, cm–1): 2960, 2219, 1716, 1658, 1436, 1290, 1201,
1171, 1040, 838, 748. HRMS (ESI, m/z) calcd. for C20H24O4Na
[M+Na]+: 351.1572; found: 351.1581.
Methyl (E)‐6‐(4‐trifluoromethyl)acetylenecarboxy‐2‐hex‐
enoate (8e). 49% isolated yield. Oil. 1H NMR (400 MHz, CDCl3):
δ 7.70 (d, J = 7.7 Hz, 2H, 2CH), 7.65 (d, J = 7.7 Hz, 2H, 2CH), 6.97
(dt, J = 15.5, 6.9 Hz, 1H, CHCH2), 5.89 (d, J = 15.5, 1H, CHCO),
4.27 (t, J = 6.9 Hz, 2H, OCH2), 3.73 (s, 3H, OCH3), 2.38–2.32 (m,
2H, CHCH2), 1.93–1.88 (m, 2H, CH2CH2CH2). 13C NMR (100 MHz,
CDCl3): δ 166.98 (C‐O), 153.67 (C‐O), 147.56 (alkenyl C), 133.34
(aromatic C), 132.59 (aromatic C), 132.26 (aromatic C), 125.70
(aromatic C), 123.52 (CF3), 122.10 (alkenyl C), 84.42 (alkynyl
C), 82.19 (alkynyl C), 65.43 (OCH2), 51.67 (OCH3), 28.66 (CH2),
27.01 (CH2). IR (neat, cm–1): 2953, 2927, 2230, 1716, 1660,
1324, 1287, 1172, 1067, 845, 747. HRMS (ESI, m/z) calcd. for
C17H15O4NaF3 [M+Na]+: 363.0820; found: 363.0814.
Methyl (E)‐7‐phenylacetylenecarboxy‐2‐heptenoate (9a).
30% isolated yield. Oil. 1H NMR (400 MHz, CDCl3): δ 7.61–7.36
(m, 5H, 5CH), 6.97 (dt, J = 15.6, 7.0 Hz, 1H, CHCH2), 5.86 (d, J =
15.6, 1H, CHCO), 4.24 (t, J = 6.9 Hz, 2H, OCH2), 3.73 (s, 3H,
OCH3), 2.30–2.24 (m, 2H, CHCH2), 1.79–1.56 (m, 4H, 2CH2). 13
C
NMR (100 MHz, CDCl3): δ 166.98 (C‐O), 154.10 (C‐O), 148.53
(alkenyl C), 133.00 (aromatic C), 130.65 (aromatic C), 128.57
(aromatic C), 121.51 (alkenyl C), 119.61 (aromatic C), 86.36
(alkynyl C), 80.57 (alkynyl C), 65.59 (OCH2), 51.43 (OCH3),
31.63 (CH2), 27.92 (CH2), 24.37 (CH2). IR (neat, cm–1): 2958,
2924, 2201, 1722, 1701, 1660, 1460, 1259, 1024, 800, 745.
HRMS (ESI, m/z) calcd. for C17H18O4Na [M+Na]+: 309.1103;
found: 309.1091.
Methyl
(E)‐7‐(4‐methylphenyl)acetylenecarboxy‐2‐hep‐
3. Results and discussion
tenoate (9b). 49% isolated yield. Oil. 1H NMR (400 MHz, CDCl3):
δ 7.49 (d, J = 7.9 Hz, 2H, 2CH), 7.18 (d, J = 7.9 Hz, 2H, 2CH), 6.97
(dt, J = 15.7, 6.4 Hz, 1H, CHCH2), 5.86 (d, J = 15.7, 1H, CHCO),
4.24 (t, J = 6.4 Hz, 2H, OCH2), 3.73 (s, 3H, OCH3), 2.38 (s, 3H,
CH3), 2.30–2.24 (m, 2H, CHCH2), 1.78–1.56 (m, 4H, 2CH2). 13C
NMR (100 MHz, CDCl3): δ 167.15 (C‐O), 154.40 (C‐O), 148.76
(alkenyl C), 141.48 (aromatic C), 133.16 (aromatic C), 129.51
(aromatic C), 121.61 (alkenyl C), 116.58 (aromatic C), 87.07
(alkynyl C), 80.38 (alkynyl C), 65.68 (OCH2), 51.63 (OCH3),
31.81 (CH2), 29.86 (CH2), 28.08 (CH2), 24.52 (CH3). IR (neat,
cm–1): 2957, 2925, 2217, 1708, 1658, 1435, 1382, 1290, 1169,
1038, 817, 747. HRMS (ESI, m/z) calcd. for C18H20O4Na
[M+Na]+: 323.1259; found: 323.1247.
Sequential reactions can offer efficient methods for the syn‐
thesis of a variety of different important organic compounds
that would be otherwise difficult to prepare using conventional
methods. Our recent studies on the carboxylative coupling [34]
and olefin metathesis [56] reactions provided a platform for the
synthesis of functionalized 2‐alkynoates from CO2, and other
simple and readily available starting materials via the combina‐
tion of these two reactions. Considering the high reaction effi‐
ciency of the carboxylative coupling reaction and the use of the
relatively costly Grubbs‐Hoveyda catalyst in the cross‐metath‐
esis reaction, the carboxylative coupling reaction was con‐
ducted prior to the cross‐metathesis reaction.

ZHANG Linlin et al. / Chinese Journal of Catalysis 34 (2013) 1179–1186
Table 1
Ag‐catalyzed carboxylative coupling of terminal alkynes, CO2, and bromides.
O
Br
+
+
CO2
R
O
n
n
R
1
2
3, 4
Entry
1
2
3
4
5
6
7
8
R
Ph
n
1
1
1
1
1
1
1
2
2
2
2
2
2
2
Product
3a
3b
3c
3d
3e
3f
3g
4a
4b
4c
4d
4e
Isolated yield (%)
69
87
91
87
85
65
64
75
76
86
88
83
66
59
4‐MeC6H4
4‐MeOC6H4
4‐tBuC6H4
4‐CF3C6H4
PhCH2CH2
n‐hexyl
Ph
9
4‐MeC6H4
4‐MeOC6H4
4‐tBuC6H4
4‐CF3C6H4
PhCH2CH2
n‐hexyl
10
11
12
13
14
4f
4g
Reaction conditions: 2.0 mmol terminal alkyne 1, 3.0 mmol bromide 2, 3.0 mmol Cs2CO3, 0.002 mmol AgI, 2.0 MPa CO2, 20 ml DMF, 60 °C, 24 h.
3.1. Ag‐catalyzed carboxylative coupling of terminal alkynes,
CO2, and bromides
reactivity. Generally, the Grubbs‐Hoveyda catalyst 6 [59] shows
higher catalytic activity towards cross‐metathesis reactions
than the second‐generation Grubbs catalyst 5 [57,58] (Scheme
2). With this in mind, catalyst 6 was used in our experimental
investigations. As shown in Table 2, in the presence of a 5
mol% loading of catalyst 6, the aryl‐substituted 4‐pentenyl
(3a–3e) and 5‐hexenyl (4a–4e) propiolates underwent
cross‐metathesis reactions with an excess of methyl acrylate in
toluene at 60 °C to give the desired aryl‐substituted methyl
In the present study, the silver(I) catalytic system consisted
of 0.1 mol% of AgI and 1.5 equivalents of Cs2CO3, which was
used as base. This catalytic system was used for the carboxyla‐
tive coupling of terminal alkynes, CO2 and terminal al‐
kene‐derived bromides (5‐bromopentene or 6‐bromohexene)
under 2.0 MPa CO2 pressure at 60 °C in DMF over a period of 24
h. As shown in Table 1, a series of 4‐pentenyl 2‐alkynoates (3)
and 5‐hexenyl 2‐alkynoates (4) were obtained in moderate to
good yields via the carboxylative coupling reaction of various
terminal alkynes and CO2 with 5‐bromopentene or
6‐bromohexene, respectively. Similarly, the carboxylative reac‐
tion proceeded in a highly selective manner and no direct cou‐
pling by‐products were detected even in the cases of complete
conversion. Phenylacetylenes bearing both electron‐donating
and electron‐withdrawing substituents on the ring were suc‐
cessfully converted to the corresponding carboxylative prod‐
ucts in good yields (Table 1, entries 1–5 and 8–12). Compared
with the aryl‐substituted terminal alkynes, the al‐
kyl‐substituted terminal alkynes gave relatively low yields (Ta‐
ble 1, entries 6, 7, 13, and 14). This difference was attributed to
the higher stability of the aryl‐substituted silver(I) acetylide
relative to the alkyl‐substituted silver(I) acetylide intermediate
which is generally thought to be initially formed according to
the possible mechanism of the carboxylative coupling of the
terminal alkyne, CO2, and halide [34].
(E)‐6‐acetylenecarboxy‐2‐hexenoates
(8a–8e)
and
(E)‐7‐acetylenecarboxy‐2‐heptenoates (9a–9e), respectively, in
moderate to good yields (Table 2, entries 1–4, 6, and 9–13). No
intermolecular or intramolecular enyne metathesis products
were detected, because the electron‐deficient internal alkyne
moiety in the alkene‐derived 2‐alkynoates cannot undergo the
enyne metathesis reaction with the electron‐deficient olefin
substrate methyl acrylate in the presence of a Grubbs‐type
catalyst. The second‐generation Grubbs catalyst 5 showed no
catalytic activity towards the cross‐metathesis reaction be‐
tween the alkene‐derived 2‐alkynoates and methyl acrylate
(Table 2, entry 5). Compared with aryl‐substituted 4‐pentenyl
propiolates 3a–3e, the aryl‐substituted 5‐hexenyl propiolates
4a–4e gave relatively low yields of the cross‐metathesis prod‐
ucts. According to the well‐defined olefin metathesis mecha‐
nism, the Grubbs‐Hoveyda catalyst 6 initially reacted with the
alkene‐derived 2‐alkynoates to form a new ruthenium alkyli‐
3.2. Cross‐metathesis reactions of the terminal alkene‐derived
2‐alkynoates with methyl acrylate
With a variety of different alkene‐derived 2‐alkynoates in
hand, we proceeded to investigate our interest in the synthesis
of functionalized 2‐alkynoates via the cross‐metathesis reac‐
tion of the alkene‐derived 2‐alkynoates with an olefin of lower
Scheme 2. The second‐generation Grubbs catalyst 5 and Grubbs‐
Hoveyda catalyst 6.

ZHANG Linlin et al. / Chinese Journal of Catalysis 34 (2013) 1179–1186
Table 2
Cross‐metathesis reaction of terminal alkene‐derived 2‐alkynoates with methyl acrylate.
O
O
+
O
COOMe
n
O
COOMe
n
R
R
8, 9
3, 4
7
3 or 4
Entry
Product
Isolated yield (%)
R
Ph
n
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
1
2
3
4
5a
6
7
8
9
10
11
12
13
14
15
3a
3b
3c
3d
3d
3e
3f
3g
4a
4b
4c
4d
4e
4f
8a
8b
8c
8d
8d
8e
8f
8g
9a
9b
9c
9d
9e
9f
31
63
68
89
<1c
49
<1c
<1c
30
49
56
77
44
<1b
<1b
4‐MeC6H4
4‐MeOC6H4
4‐tBuC6H4
4‐tBuC6H4
4‐CF3C6H4
PhCH2CH2
n‐hexyl
Ph
4‐MeC6H4
4‐MeOC6H4
4‐tBuC6H4
4‐CF3C6H4
PhCH2CH2
n‐hexyl
4g
9g
Reaction conditions: 0.2 mmol 2‐alkynoates 3 or 4, 10 mmol methyl acrylate 7, 0.01 mmol Grubbs‐Hoveyda catalyst 6, 2 ml toluene, 60 °C, 12 h. a 0.01
mmol 5 as catalyst. b Yield was determined by 1H NMR.
dene complex as a catalytically active intermediate. The occur‐
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likely because their chelate intermediates showed higher levels
of stability and their catalytic activities were inhibited. Al‐
kyl‐substituted 4‐pentenyl (3f and 3g) and 5‐hexenyl (4f and
4g) propiolates failed to undergo the cross‐metathesis reac‐
tions with methyl acrylate even at elevated temperatures, with
higher catalyst loadings and with prolonged reaction times,
which might be attributed to the preponderantly competitive
coordination of the alkyne moiety in alkyl‐substituted propio‐
late substrates to the ruthenium center (Table 2, entries 7, 8,
14, and 15). Other cross‐metathesis partners such as acrolein,
acrylonitrile and t‐butyl acrylate gave the corresponding
cross‐metathesis products in very low yields (< 5%).
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4. Conclusions
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14314
A silver‐catalyzed carboxylative coupling reaction was suc‐
cessfully developed for the coupling of a variety of different
aryl‐substituted
terminal
alkynes
and
CO2
with
5‐bromopentene or 6‐bromohexene to give a series of
4‐pentenyl 2‐alkynoates or 5‐hexenyl 2‐alkynoates in good
yields. The resulting 2‐alkynoates were further transformed
into
methyl
(E)‐6‐acetylenecarboxy‐2‐hexenoates
or
(E)‐7‐acetylenecarboxy‐2‐heptenoates in moderate to good
yields via their cross‐metathesis reaction with methyl acrylate
in the presence of the Grubbs‐Hoveyda catalyst. This carboxy‐
lative coupling/cross‐metathesis reaction sequence offers an
efficient and convenient method for the synthesis of function‐
alized 2‐alkynoates from CO2, and other simple and readily
available starting materials.
[23] Manjolinho F, Arndt M, Goossen K, Goossen L J. ACS Catal, 2012, 2:
2014
[24] Fukue Y, Oi S, Inoue Y. J Chem Soc Chem Commun, 1994, 2091

ZHANG Linlin et al. / Chinese Journal of Catalysis 34 (2013) 1179–1186
Graphical Abstract
Chin. J. Catal., 2013, 34: 1179–1186 doi: 10.1016/S1872‐2067(12)60527‐0
Sequential Ag‐catalyzed carboxylative coupling/Ru‐catalyzed
cross‐metathesis reactions for the synthesis of functionalized
2‐alkynoates
carboxylative coupling
R
+
CO2
X
n
ZHANG Linlin, ZHANG Wenzhen*, SHI Linglong, REN Xiang,
LÜ Xiaobing*
O
O
Dalian University of Technology
n
R
O
An efficient and convenient method has been developed for the syn‐
thesis of functionalized 2‐alkynoates in good yield from terminal
alkynes, CO2, terminal alkene‐derived bromides, and methyl acrylate
via the combination of silver‐catalyzed carboxylative coupling and
ruthenium‐catalyzed cross‐metathesis reactions.
R'
O
R'
n
cross-metathesis
R
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