Copper-catalyzed electrochemical synthesis of alkylidene lactones from carbon dioxide and 1,4-diarylbuta-1,3-diynes

Article abstract of DOI:10.1016/j.tet.2013.02.089

The novel synthesis of alkylidene lactones from carbon dioxide with 1,4-diarylbuta-1,3-diynes via copper-catalyzed electrochemical route is described. The procedure was smoothly performed in an undivided electrochemical cell fitted with Ni cathode and Al anode, containing n-Bu₄NBr-DMF electrolyte with a constant current under 4 MPa pressure of CO₂. The corresponding alkylidene lactones could be obtained in moderate to good yields in the presence of catalyst CuI, while the γ-keto carboxylic acids as main products were obtained without any catalysts. A reaction mechanism was also briefly discussed.

Full text of DOI:10.1016/j.tet.2013.02.089

Tetrahedron 69 (2013) 3135e3140
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Copper-catalyzed electrochemical synthesis of alkylidene lactones
from carbon dioxide and 1,4-diarylbuta-1,3-diynes
,
,
a
a,
Chuan-Hua Li a b, Gao-Qing Yuan a , Chao-Rong Qi , Huan-Feng Jiang
*
*
a School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China
b Department of Chemistry and Life Science, Xiangnan University, Chenzhou 423000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The novel synthesis of alkylidene lactones from carbon dioxide with 1,4-diarylbuta-1,3-diynes via cop-
per-catalyzed electrochemical route is described. The procedure was smoothly performed in an un-
divided electrochemical cell fitted with Ni cathode and Al anode, containing n-Bu4NBreDMF electrolyte
with a constant current under 4 MPa pressure of CO2. The corresponding alkylidene lactones could be
Received 17 November 2012
Received in revised form 13 February 2013
Accepted 26 February 2013
Available online 1 March 2013
obtained in moderate to good yields in the presence of catalyst CuI, while the g-keto carboxylic acids as
main products were obtained without any catalysts. A reaction mechanism was also briefly discussed.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Alkylidene lactones
g-Keto carboxylic acids
Carbon dioxide
1,4-Diarylbuta-1,3-diynes
Transition metal catalysts
1. Introduction
R
O
R
R
R
X
O
O
O
O
O
A number of natural products constituted by alkylidene lac-
tones as structural units have been proved to possess biological
activities, such as antibiotic and cytotoxic properties.1e3 Alkyli-
dene lactones are also useful synthetic intermediates. Their
preparation has long been an important target and continues to
arouse the interest of synthetic chemists. Up to now, various
methods have been developed to prepare alkylidene lactones
(Scheme 1), mainly including the coupling reactions of lactones
with RZnCl or AreB(OH)2 (AreSnBu3),4e6 the BayliseHillman re-
action of 2-carboxybenzaldehyde,7,8 the halolactonization of
alkynoic acids or the halolactonization of alkenoic acids followed
by dehydrohalogenation,9e13 and the transition metal-catalyzed
intramolecular cyclization of alkynoic acids.14e27 Recently, Li and
co-workers reported the Cu(I)-catalyzed intramolecular O-vinyl-
ation of carboxylic acids with alkenyl halides for the synthesis of
alkylidene lactones.28 Although these methods are efficient, it is
still necessary to explore new and convenient route for the syn-
thesis of alkylidene lactones with a simple catalytic system. The
chemical fixation of CO2 into the unsaturated hydrocarbons to-
ward CeC bond formation by transition metals mediated coupling
reactions has received much attention, which closely relates to
X
R
R
R
R
X
R
(Route a)
R
O
OSiR
Br
O
(Route b)
(Route d)
O
R -CHO+
OH
R
R
R
R
O
R
(Route c)
HO
O
R
R
Scheme 1. The previous reported synthetic routes for the synthesis of alkylidene
lactones.
fundamental academic and environmental problems together
with industrial applications, making this area of high current in-
terest. In the early year, Hoberg and co-workers successfully
applied zero-valence nickel complex Ni (COD)2 (COD¼1,5-
cyclooctadiene) as the catalyst for the carboxylation of CO2 with
alkynes.29,30 Under the catalysis of zero-valence nickel complex,
pyrones were obtained from alkynes31 (or diynes32) and CO2 (at
a pressure higher than 50 kg cmꢀ2). Dunach and co-workers have
~
employed zero-valence nickel complexes to simultaneously acti-
vate CO2 and 1,3-diynes under electrochemical conditions, which
enables one molecule of CO2 into the unsaturated system and
* Corresponding authors. Tel.: þ86 20 22236518; e-mail addresses: gqyuan@
scut.edu.cn (G.-Q. Yuan), jianghf@scut.edu.cn (H.-F. Jiang).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.02.089

3136
C.-H. Li et al. / Tetrahedron 69 (2013) 3135e3140
Table 1
deactivates the conjugated triple bond toward further CO2 in-
corporation, mainly affording the substituted (E)-2-alkylidene-3-
ynoic acids.33 Only depending on the nature of the cathode ma-
terial, monocarboxylic acid derivatives could be obtained via
electrochemical incorporation of CO2 into terminal alkynes and
Influence of cathode materials on the electrocarboxylation of 1,4-diphenylbuta-1,3-
diyne (1A) with CO2
a
Entry Cathode material Conversionb (%) Yield of 2Ac (%) Ratio of 2A:3A
1d
2d
3
4
5
Pt
Zn
Ag
Cu
11
35
50
69
77
79
9
24
40
62
72
75
82:18
69:31
80:20
90:10
94:6
a,u
-diynes.34 In recent years, we are interested in the fixation of
CO2 into unsaturated hydrocarbons via an electrochemical pro-
cess, and developed an efficient electrochemical route for the
dicarboxylation of arylacetylenes or aryl-substituted alkenes with
CO2 using Ni as the cathode without additional catalysts.35,36 Also,
we investigated the electrocarboxylation of 1,3-dienes with car-
bon dioxide, and successfully obtained the unsaturated 1,6-dioic
acids (particularly 3-hexene-1,6-dioic acid, a precursor of adipic
acid).37
Stainless steel
Ni
6
95:5
a
Electrolytic conditions: room temperature, Al anode, 1,4-diphenylbuta-1,3-
diyne (2 mmol), DMF (35 mL), n-Bu4NBr (2.5 mmol), current density 10 mA cmꢀ2
,
CO2 4 MPa, and electricity (4 F molꢀ1).
b
Conversion was calculated on starting 1,4-diphenylbuta-1,3-diyne.
Isolated yield based on starting 1A.
The carbonate is the main product.
c
d
In the paper, we explored the possibility of electrochemical
synthesis of alkylidene lactones from CO2 with 1,4-diarylbuta-1,3-
diynes. Very interestingly, the alkylidene lactones (3AeG) could
be successfully obtained with CuI as the catalyst under electro-
2A) as the main product in moderate to good yields (Table 1, entries
3e6). In all these experiments, however, the yield of alkylidene
lactone (3-(4-oxo-3-phenyl-4H-oxet-2-yl)-2-phenlylpropanoic ac-
id, 3A) was very low. Only relying on cathode materials, the yield of
3A was not easily improved. Based on the previous inves-
tigations,9e28 transition metals could effectively catalyze intra-
molecular cyclization of alkynoic acids to form alkylidene lactones.
Probably, the yield of alkylidene lactone 3A could be improved via
the catalysis of transition metal salts under electrochemical
conditions.
chemical conditions (Scheme 2), while the g-keto carboxylic acids
(2AeB) as main products were obtained in the absence of any
catalysts (Scheme 3). To our knowledge, this is the first example
of using CO2 and 1,4-diarylbuta-1,3-diynes as the starting mate-
rials to synthesize alkylidene lactones via an electrochemical
route.
2.2. Influence of metal salt catalysts
As we expected, the electrocarboxylation of 1,4-diphenylbuta-
1,3-diyne (1A) with CO2, in the presence of Pd(OAc)2, gave main
product 3A. The similar result was observed in the presence of CuI.
These results showed that the Pd(OAc)2 or CuI could promote the
formation of 3A. With some common metal salts (CuCl2, FeCl2 or
FeCl3) as catalysts, the electrocarboxylation process was further
examined. The experimental results were listed in Table 2. The
different metal salt catalysts led to various experimental results. In
the Pd(OAc)2 catalyst case, the yield of 3A was rather low (35%,
Table 2, entry 1). With CuCl2 and FeCl2 or FeCl3 as catalysts, the
corresponding yields increased apparently (62%, 65%, and 71%, re-
spectively, Table 2, entries 2e4). Especially in the CuI case, the yield
of 3A could reach 78% (Table 2, entry 5). Obviously, the formation of
3A is influenced by the properties of these metal salts and the va-
lence state of the corresponding metal ions. As well known,
Pd(OAc)2 can efficiently catalyze many organic reactions. However,
in the present electrolytic conditions, its catalytic activity is much
lower than that of CuI. The real reason is still unclear for us in the
present stage. This difference may be related to the reducibility of
Pd2þ and CuI on the cathode. According to the standard reduction
Scheme 2. Electrocarboxylation of 1,4-diarylbuta-1,3-diynes with CO2 in the presence
of CuI catalyst.
0.07 mol L-1 n-Bu4NBr-DMF
1)
Ni
Al
Ar
Constant current, 4 MPa, rt
Ar
Ar
Ar
CO2
H O
2)
COOH
3
O
1A-1B
2A-2B
1A: Ar=Ph; 1B: Ar=p-Me-C6H4
Scheme 3. Electrocarboxylation of 1,4-diarylbuta-1,3-diynes with CO2 in the absence
of catalysts.
2. Results and discussion
2.1. Influence of cathode materials
Table 2
a
Influence of metal salt catalysts on the electrocarboxylation of 1A with CO2
Some electrolytic parameters (current density and CO2 pres-
sure) have been investigated in our previous works,35e37 which can
offer some valuable references for the present work. Herein we
focused our attention on the investigation of the cathode materials
and metal salt catalysts. In the absence of metal catalysts, the effect
of cathode materials on the electrocarboxylation of 1,4-diphenyl-
1,3-butadiyne (1A) with CO2 was first investigated, and the results
were shown in Table 1. With Pt or Zn as the cathode, the carbonates
as the main products were obtained (Table 1, entries 1 and 2). The
formation of the carbonates could be explained according to the
literature (2CO2þ2eꢀ/COþCO23ꢀ).38 When Ag, Cu, stainless steel,
or nickel was used as the cathode, the electrocarboxylation affor-
Entry
Catalystb
Conversionc (%)
Yield of 3Ad (%)
Selectivity of 3A (%)
1
2
3
4
5
6
7
Pd(OAc)2
CuCl2
FeCl2
FeCl3
CuI
41
66
70
75
81
72
71
35
62
65
71
78
65
61
85
94
93
95
96
90
92
CuBr
CuCl
a
Electrolytic conditions: room temperature, Al anode and Ni cathode, 1,4-
diphenylbuta-1,3-diyne (2 mmol), DMF (35 mL), n-Bu4NBr (2.5 mmol), current
density 10 mA cmꢀ2, CO2 4 MPa, and electricity (4 F molꢀ1).
b
Metal salt catalyst (0.1 equiv).
Conversion was calculated on starting 1,4-diphenylbuta-1,3-diyne.
Isolated yield based on the starting 1A.
c
d
ded the
g
-keto carboxylic acid (4-oxo-2,5-diphenylpentanoic acid,

C.-H. Li et al. / Tetrahedron 69 (2013) 3135e3140
3137
potentials [Eq(Pd2þ/Pd)¼0.95 V, Eq(CuI/Cu)¼ꢀ0.176 V versus SHE
Table 4
a
(standard hydrogen electrode)],39 Pd2þ ions are much easier re-
duced than CuI on the cathode at the same electrolytic conditions.
The reduction of Pd2þ ions not only consumes electricity but also
decreases the catalytic activity of Pd2þ ions, leading to the low
yield. Compared with CuI, CuBr or CuCl gave less yield (Table 2,
entries 6 and 7), indicating that halogen negative ions (Xꢀ) also
affect the catalytic activity. Besides, it should be mentioned that
a small amount of 2A was still formed together with 3A in the
presence of these catalysts.
Electrocarboxylations of 1,4-diarylbuta-1,3-diynes with CO2
0.07 mol L-1
n-Bu4NBr-DMF
O
Constant current, 4 MPa, rt
CuI
1)
Al
O
Ni
Ar
CO2
Ar
Ar
Ar
H3O
2)
COOH
Entry
1
Ar
Product
Yieldb (%)
O
O
Ph
2.3. Influence of electricity
Ph (1A)
78
Ph
COOH
3A
We further examined the effect of electricity on the electro-
carboxylation of 1A with CO2. Without the passage of current to the
electrochemical cell, 3A could not be formed at all even in the
presence of CuI catalyst. This means that electrochemical activity is
necessary for the transformation. As the electricity passed the cell
increased from 1 to 4 F molꢀ1, the yield of 3A increased rapidly from
21% to 78% (Table 3, entries 1e4). When the electricity increased
from 4 F molꢀ1e5 F molꢀ1, the yield of 3A was almost unchanged
(Table 3, entry 5). So the electricity 4 F molꢀ1 seems to be appro-
priate for the present system.
O
O
2
3
p-MeeC6H4 (1B)
m-MeeC6H4 (1C)
p-MePh
m-MePh
o-MePh
80
65
Ph-p-Me
COOH
3B
O
O
Ph-m-Me
COOH
3C
O
Table 3
O
Influence of electricity on the electrocarboxylation of 1,4-diphenylbuta-1,3-diyne
4
5
6
o-MeeC6H4 (1D)
60
83
62
a
Ph-o-Me
COOH
(1A) with CO2
Entry
Electricity (F molꢀ1
)
Yield of 3Ab (%)
3D
1
2
3
4
5
1
2
3
4
5
21
32
67
78
79
O
Ph-p-(t-Bu)
O
p-(t-Bu)eC6H4 (1E)
p-FeC6H4 (1F)
COOH
p-(t-Bu)Ph
3E
a
O
O
Electrolytic conditions: room temperature, Al anode and Ni cathode, 1,4-
diphenylbuta-1,3-diyne (2 mmol), DMF (35 mL), n-Bu4NBr (2.5 mmol), current
density 10 mA cmꢀ2, CO2 4 MPa, and CuI (0.1 equiv).
O
p-FPh
Ph-p-F
b
Isolated yield based on the starting 1A.
3F COOH
2.4. Electrocarboxylation of the 1,4-diarylbuta-1,3-diynes and
CO2
O
o-FeC6H4 (1G)
7
38
o-FPh
Ph-o-F
COOH
3G
Under the optimized conditions, the electrochemical route is
extended to examine the electrocarboxylation of other 1,4-
diarylbuta-1,3-diynes with CO2. As shown in Table 4, the corre-
sponding alkylidene lactones could be obtained in moderate
to high yields. It should be noted that the substituent groups of
C]C double bond in these products all exist in E-form, indicating
that the transformation has a high stereoselectivity. Moreover,
the property of substituted groups could influence the yield of
the products. For the substrates with the electron-donating
groups, the yield of the target product increased (Table 4, en-
tries 2 and 5). Conversely, the electron-withdrawing group de-
creased the yield of the target product (Table 4, entries 6 and 7).
In addition, under the same conditions, the electrocarboxylation
of (Z,E)-1,4-diphenylbut-1-en-3-yne with CO2 could also afford
a
Electrolytic conditions: room temperature, Al anode and Ni cathode, 1,4-
diarylbuta-1,3-diyne (2 mmol), DMF (35 mL), n-Bu4NBr (2.5 mmol), current den-
sity 10 mA cmꢀ2, CO2 4 MPa, electricity (4 F molꢀ1), and CuI (0.1 equiv).
b
Isolated yield based on the starting substrate.
0.07 mol L-1
n-Bu4NBr-DMF
Ph
O
1)
2)
Constant current, 4 MPa, rt
CuI catalyst
Al
Ni
H O
O
CO2
Ph
Ph
3
Ph
COOH
(yield: 85%)
the corresponding alkylidene lactone in
Scheme 4).
a high yield (85%,
Scheme 4. Electrocarboxylation of (Z,E)-1,4-diphenylbut-1-en-3-yne with CO2 in the
presence of CuI catalyst.
2.5. Reaction mechanism
1,4-addition products of CO2, and the substrate 1,4-diphenylbuta-
The molecular structure of representative product 3G is further
confirmed by X-ray diffraction experiments (Fig. 1), which lay the
foundation for the deduction of the reaction mechanism. From the
view of molecular structures, 3A and 1,6-dioic acids resulted from
the electrocarboxylation of 1,3-dienes with CO237 all belong to the
1,3-diyne (1A) has the similar pep conjugate structure as 1,3-
dienes. Therefore, it is reasonable to believe that the electro-
carboxylation mechanism of 1,4-diphenylbuta-1,3-diyne (1A) with
CO2 to form 3A is similar to that of 1,3-dienes with CO2 to form
1,6-dioic acids.37 Besides, in the present case, CuI catalyst could

3138
C.-H. Li et al. / Tetrahedron 69 (2013) 3135e3140
At the anode:
Al
Al3+
3e
+
At the cathode and in the solution:
.
-
CO2
-
+e
O
1A
.
Ph
Ph
-
-
O
CO2
O
.
O
.
Ph
.
+e
1A
-
Ph
.
CO2
CO2
Ph
Ph
O
O
+e, CO2
O
-
D
E
O
-
O
O
Ph
Ph
O
Ph
Ph
Fig. 1. X-ray structure of product 3G.
CuI
CuI
COO
O
-
speed up the intramolecular cyclization of eCOOꢀ groups to form
3A.
O
CuI
G
-
O
2e/2H+
O
To further explore the electrochemical mechanism, the CV
(cyclic voltammetry) of 1,4-diphenylbuta-1,3-diyne (1A) and CO2
in a 0.07 mol Lꢀ1 n-Bu4NBreDMF solution was examined (as
shown in Fig. 2). At the reduction potential ꢀ2.0 V versus SCE, the
reduction current of 1,4-diphenylbuta-1,3-diyne is very obvious
(Fig. 2b), while the reduction current of CO2 is still zero (Fig. 2a).
The CV results indicate that 1,4-diphenylbuta-1,3-diyne is more
easily reduced than CO2 (0.1 MPa) under the same electrolytic
conditions. On the other hand, the reduction of substrate at the
cathode is closely related to its concentration or pressure. It should
be noted that the present electrochemical process was performed
at 4 MPa of CO2. The concentration of CO2 at 4 MPa dissolved in
DMF solvent is much larger than that of 1,4-diphenylbuta-1,3-
diyne (1A). Thus, the reduction process of carbon dioxide should
be also considered.
O
1)
protonolysis
Ph
Ph
Ph
Ph
2) H+
COOH
Product (3A)
COO
-
H
Scheme 5. The plausible reaction mechanism for 1,4-diphenylbuta-1,3-diyne with
CO2.
3. Experimental
3.1. Chemicals
All 1,3-diynes were synthesized according to the literature.45,46
Tetrabutyl ammonium bromide (n-Bu4NBr) (AR) was dried at 60 ꢁC
under vacuum for 10 h. The investigated metal electrode materials
(99.99%) were all purchased from Alfa Aesar.
3.2. Instrumentation
Mass spectral analyzes were done on a Shimadzu QP5050A
spectrometer. 1H NMR and 13C NMR were determined on a Bruker
DRX-400 spectrometer with DMSO-d6 as the solvent in the pres-
ence of Me4Si as an internal standard. FTIR spectra were measured
by a TENSOR27 spectrometer. The electrolytic cell and the param-
eters of the CV experiment are the same as those reported
previously.37
3.3. Formation process of single-crystals for product 3G
The product 3G was added to a vessel containing the mix-
solvent of ethyl acetate and n-hexane (volume ratio was 95:5).
Subsequently, the vessel was sealed and the mix-solvent evapo-
rated slowly. After about three weeks, the single-crystal sample of
3G could be obtained. The single-crystal structure of 3G has shown
that the electrocarboxylation of 1,4-diarylbuta-1,3-diyne with car-
bon dioxide was carried out in a highly selective manner.
Fig. 2. Cyclic voltammograms of a 0.07 mol Lꢀ1 n-Bu4NBreDMF solution (35 mL) at
room temperature with scan rate 50 mV sꢀ1 on a Ni working electrode: (a) only in the
presence of saturated CO2 (0.1 MPa); (b) only addition of 1,4-diphenylbuta-1,3-diyne.
Based on the experimental results and the literature,33e37
a plausible reaction mechanism is outlined in Scheme 5. 1A gets
one electron to generate its radical anion, which reacts with CO2 to
afford D. Also, CO2 is reduced into radical anion, followed by the
reaction with 1A to form the radical anion D. Subsequently, D is
further carboxylated to produce a dicarboxylate anion E. CuI can
activate unsaturated bonds and promote the intramolecular cycli-
3.4. Electrocarboxylation of 1,4-diarylbuta-1,3-diyne with
carbon dioxide
Prior to the electrosynthesis, the electrodes were cleaned and
dried. The electrosynthesis was performed in the high-pressure
electrolytic cell fitted with a nickel sheet cathode (wet surface
area 6 cm2) and an aluminum sheet anode (wet surface area 6 cm2).
In a typical experimental procedure, DMF (35 mL), n-Bu4NBr
(2.5 mmol), substrate (2 mmol), and metal salt catalyst (0.1 equiv of
substrate) were added to the cell. Subsequently CO2 was charged
into the cell at the desired pressure. The reaction mixture was
continuously stirred by a magnetic stirrer at room temperature
zation of eCOOꢀ group to form -alkylidene cyclic carbonates.40e44
a
Similarly, CuI can play the same role in the present system. Under
the catalysis of CuI, E can be converted to G via an intramolecular
cyclization of eCOOꢀ group. Then, G is transformed to H through
protonolysis with the release of CuI catalyst. After H is further re-
duced and acidified, product 3A is obtained.

C.-H. Li et al. / Tetrahedron 69 (2013) 3135e3140
3139
until a certain amount of charges passed through the cell. After the
electrolyte was distilled at reduced pressure, the residue was
acidified with hydrochloric acid (2.0 mol Lꢀ1) and continuously
stirred for 30 min. The acidic solution was then extracted with
diethyl ether (4ꢂ25 mL). The ether phase was washed twice with
distilled water. After evaporation of ether, the obtained crude
product was separated by thin layer chromatography (petroleum
ethereethyl acetate¼1:7, 2 drops of CH3COOH), and re-crystallized
twice with ethyl acetateepetroleum ether, then dried at 60 ꢁC in
a vacuum oven.
18.4 Hz, 1H), 3.38e3.44 (dd, J¼7.2, 18.4 Hz, 1H), 1.25e1.29 (s, 18H).
13C NMR (DMSO-d6, 100 MHz):
174.6, 167.9, 160.7, 150.1, 149.3,
133.9, 131.2, 129.7, 127.5, 125.7, 124.4, 110.9, 43.6, 36.1, 34.2, 31.1,
31.0. HRMS: calcd for C26H30O4 406.2100, found 406.2127.
d
3.4.8. (E)-2-(4-Fluorophenyl)-2-(4-(4-fluorophenyl)-dihydro-5-
oxofuran-2(3H)-ylidene) acetic acid (3F). IR (KBr):
n .
1817, 1698 cmꢀ1
1H NMR (DMSO-d6, 400 MHz):
d
12.7 (s, 1H), 7.17e7.45 (m, 8H),
4.37e4.41 (dd, J¼7.6, 10.4 Hz, 1H), 3.96e4.03 (dd, J¼10.4, 18.8 Hz,
1H), 3.43e3.46 (dd, J¼7.6, 18.8 Hz, 1H). 13C NMR (DMSO-d6,
100 MHz): d 174.5,167.7,162.5,161.4,160.0,136.9,132.2,130.5,128.9,
3.4.1. 4-Oxo-2,5-diphenylpentanoic acid (2A). IR (KBr):
n
1700 cmꢀ1
.
127.6, 114.7, 109.9, 44.0, 36.3. HRMS: calcd for C18H12F2O4 330.0700,
found 330.0741.
1H NMR (DMSO-d6, 400 MHz):
d
12.3 (s, 1H), 7.14e7.37 (m, 10H),
3.87e3.90 (dd, J¼4, 8 Hz, 1H), 3.77 (s, 2H), 3.26e3.33 (dd, J¼12,
20 Hz, 1H), 2.77e2.82 (dd, J¼4, 16 Hz, 1H). 13C NMR (DMSO-d6,
3.4.9. (E)-2-(2-Fluorophenyl)-2-(4-(2-fluorophenyl)-dihydro-5-
100 MHz):
d
206.1,174.0,138.9,134.6,129.6,128.6,128.3,127.7,127.1,
oxofuran-2(3H)-ylidene) acetic acid (3G). IR (KBr):
n 1815,
126.5, 48.6, 45.8, 45.3. HRMS: calcd for C17H16O3 268.1100, found
268.1108.
1697 cmꢀ1. 1H NMR (DMSO-d6, 400 MHz):
d
12.7 (s, 1H), 7.21e7.50
(m, 8H), 4.57e4.61 (dd, J¼7.2, 10.8 Hz, 1H), 4.01e4.08 (dd, J¼10.8,
18.8 Hz, 1H), 3.37e3.41 (dd, J¼7.6, 18.8 Hz, 1H). 13C NMR (DMSO-d6,
3.4.2. 4-Oxo-2,5-di-p-tolylpentanoic acid (2B). IR (KBr):
n
1695 cmꢀ1
.
100 MHz): d 173.7, 167.0, 162.2, 161.2, 158.7, 132.2, 130.8, 130.2,
1H NMR (DMSO-d6, 400 MHz):
d
12.3 (s, 1H), 7.02e7.16 (m, 8H),
129.5, 124.2, 115.8, 104.8, 35.8. HRMS: calcd for C18H12F2O4
330.0700, found 330.0753.
3.80e3.84 (dd, J¼4, 12 Hz, 1H), 3.69 (s, 2H), 3.20e3.27 (dd, J¼12,
20 Hz, 1H), 2.69e2.75 (dd, J¼4, 20 Hz, 1H), 2.24e3.25 (s, 6H). 13C
NMR (DMSO-d6, 100 MHz):
d 206.3, 174.1, 136.2, 135.9, 135.6, 131.5,
4. Conclusion
129.4, 129.1, 128.9, 127.5, 48.3, 45.4, 45.2. 20.6. HRMS: calcd for
C19H20O3 296.1400, found 296.1414.
In conclusion, the electrocarboxylation of 1,4-diarylbuta-1,3-
diynes with CO2 has been investigated with and without cata-
lysts. Some common metal salts (CuCl2, FeCl2 and FeCl3), especially
CuI, could efficiently catalyze the electrocarboxylation to afford
alkylidene lactones (cyclic unsaturated carboxylic acid lactones).
The present work provides an efficient route for the synthesis of
alkylidene lactones and a new insight into the electrocarboxylation
of 1,4-diarylbuta-1,3-diynes with CO2 in the presence and absence
of the catalyst (CuI).
3.4.3. (E)-2-(Dihydro-5-oxo-4-phenylfuran-2(3H)-ylidene)-2-phenyla-
cetic acid (3A). IR (KBr):
400 MHz):
12.68 (s, 1H), 7.27e7.41 (m, 10H), 4.37e4.42 (dd, J¼7.2,
n .
1816, 1696 cmꢀ1 1H NMR (DMSO-d6,
d
10.4 Hz, 1H), 3.96e4.04 (dd, J¼10.4, 18.8 Hz, 1H), 3.40e3.46 (dd,
J¼7.6, 18.8 Hz, 1H). 13C NMR (DMSO-d6, 100 MHz):
d 174.5, 167.8,
160.9, 136.9, 134.2, 130.1, 128.9, 128.0, 127.7, 127.1, 111.0, 44.0, 36.2.
HRMS: calcd for C18H14O4 294.0900, found 294.0900.
3.4.4. (E)-2-(Dihydro-5-oxo-4-p-tolylfuran-2(3H)-ylidene)-2-p-tol-
Acknowledgements
ylacetic acid (3B). IR (KBr):
400 MHz):
n
1807, 1690 cmꢀ1. 1H NMR (DMSO-d6,
d
12.5 (s, 1H), 7.10e7.24 (m, 8H), 4.30e4.34 (dd, J¼7.2,
The authors thank National Natural Science Foundation of China
(Nos. 21172079, 21172076 and 20932002), the National Basic Re-
search Program of China (973 Program) (2010CB732206) and the
Guangdong Natural Science Foundation (10351064101000000),
and the Fundamental Research Funds for the Central Universities
(2011zz007) and the construct program of the key discipline in
Hunan province for financial support.
10 Hz, 1H), 3.91e3.99 (dd, J¼10.4, 18.4 Hz, 1H), 3.33e3.41 (dd, J¼7.2,
18.8 Hz, 1H), 2.29 (s, 3H), 2.30 (s, 3H). 13C NMR (DMSO-d6,
100 MHz):
d 174.6, 167.9, 160.6, 136.9, 136.2, 133.9, 131.2, 129.9,
129.4, 128.3, 127.8, 110.9, 43.6, 36.2, 20.8, 20.6. HRMS: calcd for
C20H18O4 322.1200, found 322.1201.
3.4.5. (E)-2-(Dihydro-5-oxo-4-m-tolylfuran-2(3H)-ylidene)-2-p-tol-
ylacetic acid (3C). IR (KBr):
400 MHz):
n
1807, 1691 cmꢀ1. 1H NMR (DMSO-d6,
12.5 (s, 1H), 7.06e7.29 (m, 8H), 4.32e4.43 (dd, J¼7.2,
Supplementary data
d
17.6 Hz, 1H), 3.95e4.02 (dd, J¼10.4, 19.2 Hz, 1H), 3.34e3.44 (dd,
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.tet.2013.02.089.
These data include MOL file and InChiKey of the most important
compounds described in this article.
J¼7.2, 18.8 Hz, 1H), 2.30 (s, 3H), 2.32 (s, 3H). 13C NMR (DMSO-d6,
100 MHz): d 174.6, 167.7, 160.7, 128.7, 128.5, 128.3, 127.7, 127.5, 127.1,
124.9, 127.8, 111.1, 43.8, 36.1, 20.9, 20.9. HRMS: calcd for C20H18O4
322.1200, found 322.1201.
References and notes
3.4.6. (E)-2-(Dihydro-5-oxo-4-o-tolylfuran-2(3H)-ylidene)-2-p-tol-
ylacetic acid (3D). IR (KBr):
400 MHz):
n
1806, 1689 cmꢀ1. 1H NMR (DMSO-d6,
1. Mason, C. P.; Edwards, K. R.; Carlson, R. E.; Pignatello, J.; Gleason, F. K.; Wood, J.
M. Science 1982, 215, 400.
2. Niwa, M.; Iguchi, M.; Yamamura, S. Tetrahedron Lett. 1975, 1539.
3. Niwa, M.; Iguchi, M.; Yamamura, S. Tetrahedron Lett. 1975, 4395.
4. Castulik, J.; Mazal, C. Tetrahedron Lett. 2000, 41, 2741.
5. Bellina, F.; Anselmi, C.; Rossi, R. Tetrahedron Lett. 2002, 43, 2023.
6. Scheiper, B.; Bonnekessel, M.; Krause, H.; Furstner, A. J. Org. Chem. 2004, 69,
3943.
7. Lee, K. Y.; Kim, J. M.; Kim, J. N. Synlett 2003, 357.
8. Haase, C.; Langer, P. Synlett 2005, 453.
d
12.6 (s, 1H), 7.19e7.30 (m, 8H), 4.58e4.63 (dd, J¼6.8,
10.4 Hz, 1H), 4.01e4.09 (dd, J¼10.4, 18.8 Hz, 1H), 3.37e3.40 (dd,
J¼6.8, 18.8 Hz, 1H), 2.33 (s, 3H), 2.17 (s, 3H). 13C NMR (DMSO-d6,
100 MHz):
d 174.7, 167.5, 161.0, 130.7, 129.5, 128.2, 127.7, 127.4, 127,
€
126.5, 125.5, 125.4, 110.3, 41.4, 35.5, 19.4, 19.2. HRMS: calcd for
C20H18O4 322.1200, found 322.1205.
9. Krafft, G. A.; Katzenellenbogen, J. A. J. Am. Chem. Soc. 1981, 103, 5459.
10. Sofia, M. J.; Chakravarty, P. K.; Katzenellenbogen, J. A. J. Org. Chem. 1983, 48,
3318.
3.4.7. (E)-2-(4-tert-Butylphenyl)-2-(4-(4-tert-butylphenyl)-dihydro-
5-oxofuran-2(3H)-ylidene) acetic acid (3E). IR (KBr):
1697 cmꢀ1. 1H NMR (DMSO-d6, 400 MHz):
12.6 (s, 1H), 7.19e7.41
(m, 8H), 4.32e4.36 (dd, J¼7.2, 10 Hz, 1H), 3.92e3.99 (dd, J¼10,
n 1815,
d
11. Gevaza, Y. I.; Staninets, V. I. Chem. Heterocycl. Compd. 1988, 24, 1073.
ꢀ
12. Harmange, J. C.; Figadere, B. Tetrahedron: Asymmetry 1993, 4, 1711.

3140
C.-H. Li et al. / Tetrahedron 69 (2013) 3135e3140
13. Maddess, M. L.; Lautens, M. Synthesis 2004, 1399.
14. Yanagihara, N.; Lambert, C.; Iritani, K.; Utimoto, K.; Nozaki, H. J. Am. Chem. Soc.
1986, 108, 2753.
29. Hoberg, H.; Schaefer, D.; Burkhart, G.; Krueger, C.; Romao, M. J. J. Organomet.
Chem. 1984, 266, 203.
30. Hoberg, H.; Baerhausen, D. J. Organomet. Chem. 1989, 379, C7.
31. Walther, D.; Schoneberg, H.; Dinjus, E.; Sieler, J. J. Organomet. Chem.1987, 334, 377.
32. Tsuda, T.; Morikawa, S.; Sumiya, R.; Saegusa, T. J. Org. Chem. 1988, 53, 3140.
15. Pale, P.; Chuche, J. Tetrahedron Lett. 1987, 51, 6447.
16. Chan, D. M.T.;Marder, T. B.;Milstein,D.; Taylor, N. J. J. Am. Chem. Soc.1987,109, 6385.
17. Arcadi, A.; Cacchi, S.; Marnelli, F. Tetrahedron Lett. 1992, 27, 3915.
18. Bouyssi, D.; Gore, J.; Balme, G. Tetrahedron Lett. 1992, 33, 2811.
19. Dalla, V.; Pale, P. Tetrahedron Lett. 1994, 35, 3525.
20. Rossi, R.; Bellina, F.; Mannina, L. Tetrahedron Lett. 1998, 39, 3017.
21. Elgafi, S.; Field, L. D.; Messerle, B. A. J. Organomet. Chem. 2000, 607, 97.
22. Genin, E.; Toullec, P. Y.; Antoniotti, S.; Brancour, C.; Genet, J. P.; Michelet, V. J.
Am. Chem. Soc. 2006, 128, 3112.
ꢁ
ꢂ
ꢁ
33. Derien, S.; Clinet, J. C.; Dunach, E.; Perichon, J. J. Org. Chem. 1993, 58, 2578.
~
34. Koster, F.; Dinjus, E.; Dunach, E. Eur. J. Org. Chem. 2001, 2507.
35. Yuan, G. Q.; Jiang, H. F.; Lin, C.; Liao, S. J. Electrochim. Acta 2008, 53, 2170.
36. Yuan, G. Q.; Jiang, H. F.; Lin, C. Tetrahedron 2008, 64, 5866.
37. Li, C. H.; Yuan, G. Q.; Ji, X. C.; Wang, X. J.; Ye, J. S.; Jiang, H. F. Electrochim. Acta
2011, 56, 1529.
ꢁ
38. Amatore, C.; Saveant, J. M. J. Am. Chem. Soc. 1981, 103, 5021.
23. Harkat, H.; Weibel, J.-M.; Pale, P. Tetrahedron Lett. 2006, 47, 6273.
24. Marchal, E.; Uriac, P.; Legoin, B.; Toupet, L.; Van de Weghe, P. Tetrahedron 2007,
63, 9979.
39. Lide, D. R. Handbook of Chemistry and Physics; CRC: Boca Raton, 2000.
40. Kosower, E. M.; Sorensen, T. S. J. Org. Chem. 1963, 28, 687.
41. Kim, H. S.; Kim, J. W.; Kwon, S. C.; Shim, S. C.; Kim, T. J. J. Organomet. Chem. 1997,
545e546, 337.
42. Gu, Y.; Shi, F.; Deng, Y. J. Org. Chem. 2004, 69, 391.
43. Jiang, H. F.; Wang, A. Z.; Liu, H. L.; Qi, C. R. Eur. J. Org. Chem. 2008, 2309.
44. Yuan, G. Q.; Zhu, G. J.; Chang, X. Y.; Qi, C. R.; Jiang, H. F. Tetrahedron 2010, 66,
9981.
25. Toullec, P. Y.; Genin, E.; Antoniotti, S.; Genet, J. P.; Michelet, V. Synlett 2008, 707.
26. Rammah, M. M.; Othman, M.; Ciamala, K.; Strohmann, C.; Rammah, M. B. Tet-
rahedron 2008, 64, 3505.
ꢁ
27. Harkat, H.; Dembele, A. Y.; Weibel, J. M.; Blanc, A.; Pale, P. Tetrahedron 2009, 65,
1871.
28. Sun, C. H.; Fang, Y. W.; Li, S.; Zhang, Y.; Zhao, Q. W.; Zhu, S. N.; Li, C. Z. Org. Lett.
2009, 11, 4084.
45. Adimurthy, S.; Malakar, C. C.; Beifuss, U. J. Org. Chem. 2009, 74, 5648.
46. Yin, W. Y.; He, C.; Chen, M.; Zhang, H.; Lei, A. Org. Lett. 2009, 11, 709.