Synthesis of diarylalkynes by iron/copper co-catalyzed decarboxylative sp-sp2 coupling of alkynyl carboxylic acids and aryl halides

Article abstract of DOI:10.1002/adsc.201100238

The highly effective decarboxylative sp-sp² coupling of alkynylcarboxylic acids with various aryl halides was carried in the presence of low-cost and readily available copper(I) iodide/iron(III) acetylacetonate under ligand-free and palladium-free conditions using low catalyst loadings. This protocol makes such coupling reactions more practical and useful. Copyright

Full text of DOI:10.1002/adsc.201100238

FULL PAPERS
DOI: 10.1002/adsc.201100238
Synthesis of Diarylalkynes by Iron/Copper Co-Catalyzed
2
À
Decarboxylative sp sp Coupling of Alkynyl Carboxylic Acids
and Aryl Halides
Tingyi Li,a Xiaoming Qu,a Yan Zhu,a Peng Sun,a Hailong Yang,a Yuqin Shan,a
Hongxin Zhang,a Defu Liu,a Xiang Zhang,a and Jincheng Maoa,*
a
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials
Science, Soochow University, Suzhou 215123, Peopleꢀs Republic of China
Fax : (+86)-512-6588-0403; e-mail: jcmao@suda.edu.cn
Received: March 31, 2011; Revised: June 23, 2011; Published online: October 10, 2011
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adcs.201100238.
Abstract: The highly effective decarboxylative sp-sp2 makes such coupling reactions more practical and
coupling of alkynylcarboxylic acids with various aryl useful.
halides was carried in the presence of low-cost and
readily available copper(I) iodide/ironACTHNUGRTNEUNG(III) acetyla- Keywords: alkynylcarboxylic acids; aryl iodides; cou-
cetonate under ligand-free and palladium-free condi- pling reaction; decarboxylative reaction; diaryl-
tions using low catalyst loadings. This protocol alkynes
Introduction
and phosphine ligands, including dppf and dppb.[6a,b]
Then, Kim and Lee reported that Pd2A(dba)3 together
CTHUNGTRENNUNG
Palladium-catalyzed cross-couplings are extremely with PPh3 or Xantphos could also catalyze the cou-
useful reactions in the organic synthesis of materials pling in high yield.[6c] More recently, Li found that a
or drugs for modern chemical and medical applica- combination of PdACTHUNRGTNEUNG(OAc)2 and Xphos could catalyze
tions, because they offer a powerful means for the decarboxylative coupling reactions of alkynylcarbox-
construction of new carbon-carbon bonds.[1] The im- ylic acids with a wide range of aryl halides.[6d] Further-
portance of such reactions has been recognized by the more, Song and Lee synthesized symmetrical and un-
award of Nobel Prize in Chemistry 2010 jointly to symmetrical diarylalkynes from propiolic acid using
Richard F. Heck, Ei-ichi Negishi and Akira Suzuki decarboxylative coupling with the PdACHTNUGTRNEG(UN PPh3)2Cl2/dppb
for their contributions in palladium-catalyzed cou- catalytic system.[6e] Although great efforts have been
plings.[2] A recent breakthrough in the field is the de- made on this reaction, the drawbacks of Pd catalyst
velopment of decarboxylative coupling reactions, systems, such as their high cost, toxicity and the po-
since acids and their derivatives are low-cost and tential contamination of the products, limit their mas-
commercially available substrates.[3] In 2006, Gooßen sive applications in some occasions, particularly in the
and co-workers reported an alternative way to pre- pharmaceutical industry, where close monitoring of
pare biaryls by decarboxylative coupling between aryl the metal contamination of the products is required.[7]
halides and carboxylic acids.[4] Since then, there have Therefore, the use of less expensive and less toxic
been other reports of decarboxylative couplings of metal than Pd may be advantageous. Furthermore, in
carboxylic acids or their salts.[5] However, decarboxy- view of the difficulty of working with toxic and mois-
lative couplings of alkynylcarboxylic acids have re- ture-sensitive phosphine ligands, would the develop-
ceived less attention.[6] It is noteworthy that decarbox- ment of ligand-free decarboxylative couplings
ylative coupling between alkynylcarboxylic acids and (Scheme 1) offer additional advantages? As a further
aryl halides could be considered as a category of tra- development of our long-running interest in coupling
ditional Sonogashira coupling reactions. In 2008, Lee reactions,[8] we now report highly effective iron/
and co-workers described the first example of such a copper co-catalyzed ligand-free decarboxylative cou-
decarboxylative coupling in the presence of Pd2ACTHNUTRGEN(UNG dba)3
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Tingyi Li et al.
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reaction proceeded with Vogelꢀs protocol (50% yield;
Table 1, entry 4).[12a] The combination of CuI and
FeACTHNUTRGEN(UGN acac)3 was explored further and it was found that
an excellent yield (96% yield) could be obtained by
working at 1408C (Table 1, entry 5). Under the same
conditions, CuACTHNUTRGNEUNG(acac)2 instead of CuI afforded an obvi-
ously reduced result (only 39% yield) (Table 1,
entry 6). This suggested that the combination of CuI
and FeACTHUNTRGEN(UNG acac)3 could promise high efficiency for this
Scheme 1. Approaches for decarboxylative coupling.
decarboxylative coupling. The control experiments
showed that CuI alone could catalyze such a coupling
plings between alkynylcarboxylic acids and aryl hal- in modest yield (78%) (Table 1, entry 7), whereas
ides with low catalyst loadings.[9]
FeACTHNGUTREN(UNG acac)3 alone afforded only traces of the desired
product (Table 1, entry 8). This tells us that a Cu cata-
lyst together with an Fe catalyst could show clear ac-
celeration in the decarboxylative coupling. Reduced
loadings of the Fe/Cu catalyst led to decreased yields
Results and Discussion
In the past several years, we have developed some ef- (Table 1, entries 9 and 10). To our surprise, a study of
ficient catalysts for the coupling of aryl halides and ratio of amount of Fe and Cu catalyst showed that 2:1
terminal alkynes, including
a Cu catalyst-ligand or 1:2 ratios had a better result than a 1:1 ratio
system[10] and an Fe-Cu system.[11] Here, we wanted to (Table 1, entries 11, 12 vs. entries 9, 10). Thus, we
apply these known catalytic systems to the decarboxy- chose the best ratio as 1: 2 (CuI/Fe) (Table 1,
lative coupling of 4-iodoanisole and phenylpropiolic entry 12). Lower reaction temperatures resulted in de-
acid as a model reaction. The results are listed in creased yields (Table 1, entry 13). Lower loadings of
Table 1. The reaction proceeded in a range of differ- catalyst could still afford the desired product in high
ent conditions: in the presence of 10 mol% of CuI yield (Table 1, entries 14 and 15). Further reduction
and 20 mol% of oxine (8-hydroxyquinoline)[10a] the of catalyst loading gave a poor result (Table 1,
desired product was obtained in 37% yield (Table 1, entry 16). Therefore, we selected the best catalyst
entry 1); with readily available Cu
N
ACHTUNGTNER(NUNG acac)3].
the absence of any ligand 64% yield was obtained
(Table 1, entry 2); using Fe/Cu co-catalysis a 70% celerate the copper-catalyzed decarboxylative cou-
yield was observed (Table 1, entry 3);[11a] finally the pling reaction (the best loading ratio between Fe and
Table 1. Screening of catalytic conditions for the decarboxylative coupling of 4-iodoanisole and phenylpropiolic acid.[a]
Entry
Cat. (mol%)
Base
Solvent
Temperature [oC]
Yield [%][b]
1
2
3
4
5
6
7
8
CuI (10)/oxine (20)
Cs2CO3
K2CO3
K3PO4
Cs2CO3
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
DMF
130
130
130
130
140
140
140
140
140
140
140
140
130
140
140
140
37
64
70
50
96
39
78
<5
92
85
95
96
71
99
97
<5
Cu
CuI (20)/Fe
CuI (10)/Fe(acac)3 (10)
CuI (20)/Fe(acac)3 (20)
Cu(acac)2 (20)/Fe(acac)3 (20)
CuI (20)
Fe(acac)3 (20)
CuI (10)/Fe(acac)3 (10)
CuI (5)/Fe(acac)3 (5)
CuI (10)/Fe(acac)3 (5)
(acac)3 (10)
(acac)3 (10)
(acac)3 (4)
(acac)3 (1)
CuI (0.05)/Fe(acac)3 (0.1)
T
DMSO
DMSO
NMP
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
N
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
9
ACHTUNGTRENNUNG
10
11
12
13
14
15
16
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
CuI (5)/Fe
CuI (5)/Fe
CuI (2)/Fe
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
G
CuI (0.5)/FeCAHTUNGTRENNNUG
AHCTUNGTRENNUNG
[a]
4-Iodoanisole (0.5 mmol), phenylpropiolic acid (0.6 mmol), K3PO4 (1.0 mmol), DMSO (2 mL), 130–1408C, 24 h, under
argon.
[b]
Isolated yield (based on 4-iodoanisole).
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2
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Synthesis of Diarylalkynes by Iron/Copper Co-Catalyzed Decarboxylative sp sp Coupling
Cu catalyst is 2:1), we wondered about the relation-
ship between the catalyst (Cu catalyst or Fe/Cu cata-
lyst) and the catalytic effect. The range of catalyst
loading was from 0.05 mmol to 20 mmol. The blank
experiment showed that under such conditions none
of desired product was obtained in the presence of
Fe
1408C, with any catalyst loading, a combination of
CuI with Fe(acac)3 showed better catalytic efficiency
ACHTUNGTRENNUNG(acac)3 alone. From Figure 1 it can be seen that at
ACHTUNGTRENNUNG
than CuI alone.
Figure 2. Effect of reaction temperature on the coupling of
phenylpropiolic acid and 4-iosoanisole in the presence of
CuI (0.5 mol%) and Fe
under argon.
ACHTUNGERTN(NUNG acac)3 (1 mol%), 60–1408C, 24 h,
hindrance was not apparent (Table 2, entry 2). Decar-
boxylative coupling of 1-iodonaphthalene and phenyl-
propiolic acid also afforded the desired product in
good yield (95%) (Table 2, entry 9). However, 4-nitro-
iodobenzene as the substrate gave a poor result even
when using a higher loading of catalyst (Table 2,
entry 10). The tested aliphatic alkynoic acids gave
moderate yields of the desired products (Table 2, en-
tries 11 and 12). With regard to the more challenging
aryl bromides, the couplings were conducted with
higher catalyst loadings. The decarboxylative coupling
of 3-bromothiophene and phenylpropiolic acid afford-
Figure 1. Effect of copper loading on the coupling of phenyl-
propiolic acid and 4-iosoanisole in the absence of FeACTHNUTRGNEUNG(acac)3
*
( ) and in the presence of Fe
(acac)3 (2 equiv referred to
&
CuI) ( ), 1408C, 24 h, under argon.
In addition, the effect of reaction temperature on ed only traces of the product (Table 2, entry 19).
the coupling of phenylpropiolic acid and 4-iosoanisole However, in general, moderate to good yields of the
in the presence of CuI (0.5 mol%) and Fe
ACHTUNGTERN(NGNU acac)3 corresponding products were obtained (66–93%)
(1 mol%) was investigated as shown in Figure 2. With (Table 2, entries 13–20).
the enhancement of reaction temperature, the isolat-
In order to extend the application of our methodol-
ed yield of the desired product was improved. When ogy, the coupling of 1,3-diiodobenzene and phenyl-
working at 1408C, we got a satisfactory result.
propiolic acid was carried out using a low loading cat-
To explore the substrate scope, we examined a alyst. An almost quantitative yield of the desired
range of aryl halides in the decarboxylative coupling product was obtained as shown in Scheme 2.
of alkynoic acids under the optimized conditions
To further highlight the synthetic utility of our new
(Table 2). It was observed that electronic variation of protocol, the decarboxylative coupling of 4-iodoani-
the substituents at para-position of the aryl iodide did sole and phenylpropiolic acid was scaled-up to a gram
not significantly affect the reaction efficiency scale. The desired product was obtained in 95% yield
(Table 2, entries 1–8). In addition, the effect of steric (1.49 g) as shown in the Experimental Section.
Scheme 2. Coupling of 1,3-diiodobenzene and phenylpropiolic acid using CuI (0.5 mol%) and FeACTHNURGTNEUNG(acac)3 (1 mol%).
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Table 2. Scope of Fe/Cu co-catalyzed decarboxylative coupling of various aryl halides and alkynoic acids.[a]
Yield [%][b]
97
ꢀ
Entry
1
ArX
R’C CCOOH
Time [h]
24
2
3
24
24
99
91
4
5
6
7
8
24
24
24
24
24
98
96
99
82
90
9
24
95
10[c]
11[c]
12[c]
48
48
48
45
61
51
13[c]
48
71
14[d]
15[d]
48
48
67
79
16[d]
17[d]
48
48
75
66
18[d]
48
93
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2
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Synthesis of Diarylalkynes by Iron/Copper Co-Catalyzed Decarboxylative sp sp Coupling
Table 2. (Continued)
Yield [%][b]
trace
ꢀ
Entry
ArX
R’C CCOOH
Time [h]
19[d]
48
48
20[d]
77
[a]
Aryl halide (0.5 mmol), alkynoic acid (0.6 mmol), CuI (0.5 mol%), Fe
(2 mL), 1408C, 24–48 h, under argon.
Isolated yield based on aryl halide (average of two runs).
ACHTNUGRTEN(NUGN acac)3 (1 mol%), K3PO4 (1.0 mmol), DMSO
[b]
[c]
[d]
CuI (5 mol%) and Fe
ACHTUNGTRENNUNG
CuI (10 mol%) and FeAHCTUNGTRENNUNG
Concerned by reports of contamination with residu- CuI/Pd catalyst system afforded the desired product
al transition metals in coupling reactions, especially in 22–36% yields (Table 3, entry 5).
residual palladium species,[13] we also investigated
Based on the results in hand, we suspect that CuI is
whether a catalytic amount of Pd could influence the the active catalyst and iron is playing a role for regen-
reaction. Thus, the related results are listed in Table 3. erating the active copper catalyst.[14] Thus, control ex-
Firstly, the decarboxylative coupling between 4-iodo- periments were performed in the absence of iron.
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
lent result (Table 3, entry 1). In comparison, a slightly uct of phenylacetylene was obtained. Then, the reac-
reduced yield of desired product was obtained using tions were carried out using some oxidants, such as
Fe/Cu catalyst of a lower, reagent grade [Fe
99% and CuI: 98%] (Table 3, entry 2). Indeed, combi- the desired product in 72% yield, while t-BuOOH re-
nation of Fe(acac)3 with CuI plays a crucial role in sulted in no product (For the details, please see
ACHTNUGRTNE(NUNG acac)3: H2O2 and t-BuOOH. To our surprise, H2O2 afforded
ACHTUNGTRENNUNG
the success of the transformation. As expected, the Table S1 in the Supporting Information). It is suggest-
reaction could not occur in the absence of catalyst ed that iron may play the role as co-catalyst.
(Table 3, entry 3). Pd species, such as Pd
PdCl2, gave poor results (Table 3, entries 4–7), even in
combination with CuI and Fe
ACHTUNGRTEN(NUNG OAc)2 or
(acac)3, although the Conclusions
In summary, we have developed an efficient protocol
for the decarboxylative coupling between various aryl
halides with alkynoic acids, affording the desired com-
pounds in moderate to excellent yields. To the best of
our knowledge, this study represents the first example
of Fe/Cu co-catalyzed couplings in the absence of pal-
ladium and any ligand. Although the actual catalytic
species remains unknown till now, the catalytic reac-
tions developed here may be both of practical and
fundamental interest. Work is ongoing to apply our
methodology to the synthesis of some biologically
active molecules as well as a detailed mechanistic
analysis of the catalytic system.
Table 3. Decarboxylative coupling of phenylpropiolic acid
and 4-iodoanisole in the presence of Pd, Cu or Fe catalyst-
s.[a]
Entry CuI Fe
G
Yield [%][b]
1[c]
2[d]
3
4
5
+
+
À
À
+
À
+
+
+
À
À
À
+
+
À
99
97
trace
À
À
PdCl2, Pd
PdCl2, Pd
PdCl2, Pd
PdCl2, Pd
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
6
7
[a]
General conditions: 4-Iodoanisole (0.5 mmol), phenylpro-
piolic acid (0.6 mmol), CuI (0.5 mol%), Fe(acac)3
AHCTUNGTRENNUNG
(1 mol%), Pd cat. (1 mol%), K3PO4 (1.0 mmol), DMSO
(2 mL), 1408C, 24 h, under argon; “+”stands for “in the
presence”; “À” stands for “in the absence”.
Isolated yield based on 4-iosoanisole (average of two
runs).
Experimental Section
[b]
[c]
[d]
General Experimental Methods
Fe
were employed.
Fe(acac)3 (99%) and CuI (98%) from Acros were em-
ployed.
(acac)3 (>99.9%) and CuI (99.999%) from Aldrich
All reactions were carried out under an argon atmosphere.
Solvents were dried and degassed by standard methods and
all aryl halides were purchased from known corporations.
Alkynoic acids, iron salts and copper salts were purchased
ACHTUNGTRENNUNG
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1H NMR
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from known corporations. Flash column chromatography
was performed using silica gel (300–400 mesh). Analytical
thin-layer chromatography was performed using glass plates
pre-coated with 200–300 mesh silica gel impregnated with a
fluorescent indicator (254 nm). NMR spectra were recorded
1-Chloro-4-(2-phenylethynyl)benzene:
(400 MHz, CDCl3): d=7.54–7.52 (m, 2H, ArH), 7.46 (d, J=
8.4 Hz, 2H, ArH), 7.36–7.34 (m, 4H, ArH), 7.32 (s, 1H,
ArH); 13C NMR (100 MHz, CDCl3): d=135.9 (C), 134.5
(CH), 133.3 (CH), 130.3 (CH), 130.1 (CH), 130.0 (CH),
124.6 (C), 123.4 (C), 91.9 (C), 89.9 (C); HR-MS (ESI+):
m/z=212.0396, calcd. for [C14H9Cl]+: 212.0393.
in CDCl3 on
a Varian Inova-400 NMR spectrometer
(400 MHz) with TMS as an internal reference. Products
were characterized by comparison of 1H NMR, 13C NMR
and TOF-MS data in the literature values.
1-Methoxy-3-(2-phenylethynyl)benzene:
1H NMR
(400 MHz, CDCl3): d=7.55–7.52 (m, 2H, ArH), 7.37–7.34
(m, 3H, ArH), 7.27–7.23 (m, 1H, ArH), 7.13 (d, J=7.6 Hz,
2H, ArH), 7.06 (s, 1H, ArH), 6.91–9.88 (m, 1H, ArH), 3.82
(s, 3H, CH3); 13C NMR (100 MHz, CDCl3): d=161.0 (C),
133.3 (CH), 131.1 (CH), 130.0 (CH), 130.0 (CH), 125.9
(CH), 125.8 (C), 124.8 (CH), 117.9 (C), 116.6 (CH), 90.9
(C), 90.8 (C), 56.9 (CH); HR-MS (ESI+): m/z=208.0884,
calcd. for [C15H12O]+: 208.0888.
General Procedure for Fe/Cu Co-Catalyzed
Decarboxylative Coupling Reaction of Aryl Halides
and Alkynoic Acids
A
mixture of aryl halide (0.5 mmol), alkynoic acid
(0.6 mmol), CuI (0.5 mol%), Fe(acac)3 (1 mol%), K3PO4
AHCTUNGTRENNUNG
(2.0 equiv.), and DMSO (2 mL) in a Schlenk tube was
stirred under argon atmosphere at 1408C for the desired
time until complete consumption of starting material as
monitored by TLC. After the mixture was poured into
ether, then washed with water, extracted with ethyl acetate,
dried by anhydrous MgSO4, then filtered and evaporated
under vacuum, the residue was purified by flash column
chromatography (petroleum ether or petroleum ether/ethyl
acetate) to afford the corresponding coupling products. See
the Supporting Information for full details.
1-Fluoro-4-(2-phenylethynyl)benzene:
1H NMR
(400 MHz, CDCl3): d=7.53–7.50 (m, 4H, ArH), 7.36–7.34
(m, 3H, ArH), 7.07–7.03 (m, 2H, ArH); 13C NMR
(100 MHz, CDCl3): d=165.4 (d, J=249.5 Hz, C), 135.2 (d,
J=8.3 Hz, CH), 133.2 (CH), 130.0 (d, J=3.7 Hz, CH), 124.7
(C), 121.0 (d, J=3.4 Hz, CH), 117.4 (C), 117.2 (C), 90.7 (C),
89.2 (C); HR-MS (ESI+): m/z=196.0690, calcd. for
[C14H9F]+:196.0688.
1-(2-Phenylethynyl)naphthalene: 1H NMR (400 MHz,
CDCl3): d=8.45 (d, J=8.0 Hz, 1H, ArH), 7.88–7.76 (m, 3H,
ArH), 7.67–7.59 (m, 3H, ArH), 7.56–7.54 (m, 2H, ArH),
7.48–7.39 (m, 3H, ArH); 13C NMR (100 MHz, CDCl3): d=
134.9 (C), 134.8 (C), 133.3 (C), 132.0 (CH), 130.4 (CH),
130.1 (CH), 130.1 (CH), 130.0 (CH), 128.5 (CH), 128.1
(CH), 127.9 (CH), 127.0 (CH), 125.0 (CH), 122.5 (C), 95.9
(C), 89.2 (C); HR-MS (ESI+): m/z=228.0938, calcd. for
[C18H12]+: 228.0939.
Procedure for Fe/Cu Co-Catalyzed Decarboxylative
Coupling Reaction of 4-Iodoanisole and
Phenylpropiolic Acid on a Gram Scale
A mixture of 4-iodoanisole (7.5 mmol), phenylpropiolic acid
(9.0 mmol), CuI (0.5 mol%), FeACHTNUTRGEN(UNG acac)3 (1 mol%), K3PO4
(15.0 mmol), and DMSO (30 mL) in a Schlenk tube was
stirred under an argon atmosphere at 1408C for 38 h. After
the mixture was poured into ether, it was washed with
water, extracted with ethyl acetate, dried by anhydrous
MgSO4, then filtered and evaporated under vacuum. The
residue was purified by flash column chromatography (pe-
troleum ether or petroleum ether/ethyl acetate) to afford
the corresponding coupling product; yield: 1.49 g (95%).
1-Bromo-4-(2-phenylethynyl)benzene:
1H NMR
(400 MHz, CDCl3): d=7.52–7.47 (m, 4H, ArH), 7.40–7.35
(m, 5H, ArH); 13C NMR (100 MHz, CDCl3): d=137.7 (C),
134.6 (CH), 133.2 (CH), 130.1 (CH), 130.0 (CH), 124.5
(CH), 124.1 (C), 123.8 (C), 92.1 (C), 89.9 (C); HR-MS
(ESI+): m/z=255.9886, calcd. for [C14H9Br]+: 255.9888.
1-[2-(2-Methoxyphenyl)ethynyl]benzene:
1H NMR
(400 MHz, CDCl3): d=7.67–7.64 (m, 2H, ArH), 7.59 (d, J=
7.6 Hz, 1H, ArH), 7.42–7.39 (m, 4H, ArH), 7.04–6.97 (m,
2H, ArH), 3.99 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3):
d=161.5 (C), 135.2 (CH), 133.3 (CH), 131.4 (CH), 129.9
(CH), 129.8 (CH), 125.2 (CH), 122.1 (C), 114.0 (C), 112.3
(CH), 95.1 (C), 87.4 (C), 57.5 (CH); HR-MS (ESI+): m/z=
208.1000, calcd. for [C15H12O]+: 208.0888.
1-[2-(4-Methoxyphenyl)ethynyl]benzene:
1H NMR
(400 MHz, CDCl3): d=7.52–7.50 (m, 2H, ArH), 7.47 (d, J=
8.8 Hz, 2H, ArH), 7.36–7.32 (m, 3H, ArH), 6.88 (d, J=
8.8 Hz, 2H, ArH), 3.83 (s, 3H, CH3); 13C NMR (100 MHz,
CDCl3): d=161.2 (C), 134.7 (CH), 133.1 (CH), 130.0 (CH),
129.6 (C), 125.2 (CH), 117.0 (C), 115.6 (CH), 91.0 (C), 89.7
(C), 56.9 (CH); HR-MS (ESI+): m/z=208.0896, calcd. for
[C15H12O]+: 208.0888.
1,3-Bis(2-phenylethynyl)benzene: 1H NMR (400 MHz,
CDCl3): d=7.72 (s, 1H, ArH), 7.55–7.53 (m, 4H, ArH), 7.49
(d, J=7.6 Hz, 2H, ArH), 7.39–7.32 (m, 7H, ArH); 13C NMR
(100 MHz, CDCl3): d=136.2 (CH), 133.3 (CH), 132.9 (CH),
130.1 (CH), 130.1 (CH), 130.1(CH), 125.2 (C), 124.6 (C),
91.6 (C), 90.2 (C); HR-MS (ESI+): m/z=278.1096, calcd. for
[C22H14]+: 278.1096.
1,2-Diphenylethyne: 1H NMR (400 MHz, CDCl3): d=
7.59–7.48 (m, 4H, ArH), 7.39–7.29 (m, 6H, ArH); 13C NMR
(100 MHz, CDCl3): d=133.3 (CH), 130.0 (CH), 129.9 (CH),
124.9 (C), 91.0 (C); HR-MS (ESI+): m/z=178.0791, calcd.
for [C14H10]+: 178.0783.
1-Methyl-4-(2-phenylethynyl)benzene:
1H NMR
1-Nitro-4-(2-phenylethynyl)benzene: 1H NMR (400 MHz,
CDCl3): d=8.24 (d, J=8.8 Hz, 2H, ArH), 7.69 (d, J=
7.6 Hz, 2H, ArH), 7.60–7.57 (m, 2H, ArH), 7.42–7.41 (m,
3H, ArH); 13C NMR (100 MHz, CDCl3): d=148.6 (C),
133.9 (CH), 133.5 (CH), 131.9 (CH), 130.9 (CH), 130.2
(CH), 125.3 (C), 123.7 (C), 96.3 (C), 89.2 (C); HR-MS
(ESI+): m/z=223.0635, calcd. for [C14H9NO2]+: 223.0633.
(400 MHz, CDCl3): d=7.54–7.52 (m, 2H, ArH), 7.43 (d, J=
8.0 Hz, 2H, ArH), 7.37–7.33 (m, 3H, ArH), 7.16 (d, J=
8.0 Hz, 2H, ArH), 2.37 (s, 3H, CH3); 13C NMR (100 MHz,
CDCl3): d=140.0 (C), 133.2 (CH), 133.1 (CH), 130.8 (CH),
130.0 (CH), 129.7 (CH), 125.1 (C), 121.8 (C), 91.2 (C), 90.4
(C), 23.2 (CH); HR-MS (ESI+): m/z=192.0926, calcd. for
[C15H12]+: 192.0939.
2736
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Adv. Synth. Catal. 2011, 353, 2731 – 2738

2
À
Synthesis of Diarylalkynes by Iron/Copper Co-Catalyzed Decarboxylative sp sp Coupling
1-Chloro-4-(hept-1-ynyl)benzene: 1H NMR (400 MHz,
CDCl3): d=7.31 (d, J=8.0 Hz, 2H), 7.24 (d, J=8.0 Hz, 2H),
Acknowledgements
2.38 (t, J=7.2 Hz, 2H), 1.56–1.63 (m, 2H), 1.34–1.44 (m,
4H), 0.92 (t, J=7.2 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d=134.4 (CH), 131.5 (CH), 130.1 (CH), 121.7 (CH), 93.2
(C), 81.1 (C), 32.8 (CH2), 30.0 (CH2), 23.9 (CH2), 21.0
(CH2), 15.6 (CH3); HR-MS (ESI+): m/z=206.0864, calcd.
for [C13H15Cl]+: 206.0862.
We are grateful to the grants from Natural Science Founda-
tion of China (20802046), International S&T Cooperation
Program of Jiangsu Province (BZ2010048), the Priority Aca-
demic Program Development of Jiangshu Higher Education
Institutions and the Key Laboratory of Organic Synthesis of
Jiangsu Province for financial support.
1-(Trifluoromethyl)-3-(2-phenylethynyl)benzene:
1H NMR (400 MHz, CDCl3): d=7.80 (s, 1H, ArH), 7.70 (d,
J=7.6 Hz, 1H, ArH), 7.59–7.54 (m, 3H, ArH), 7.48 (t, J=
8.0 Hz, 1H, ArH), 7.37 (t, J=3.2 Hz, 3H, ArH); 13C NMR
(100 MHz, CDCl3): d=136.2 (C), 134.1 (CH), 133.3 (CH),
130.4 (q, J=186 Hz), 130.1 (C), 130.0 (C), 129.9 (CH), 126.7
(CH), 126.4 (q, J=44 Hz), 125.9 (CH), 124.2 (CH), 92.5 (C),
89.4 (C); HR-MS (ESI+): m/z=246.0653, calcd. for
[C15H9F]+: 246.0656.
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2-(2-Phenylethynyl)pyridine: H NMR (400 MHz, CDCl3):
d=8.78 (s, 1H), 8.55 (d, J=4.8 Hz, 1H), 7.83–7.81 (m, 1H),
7.58–7.54 (m, 2H), 7.38–7.37 (m, 3H), 7.31–7.28 (m, 1H);
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138.0 (CH), 133.7 (CH), 130.7 (CH), 130.0 (CH), 128.8
(CH), 124.4 (CH), 123.8 (C), 91.2 (C), 90.0 (C); HR-MS
(ESI+): m/z=179.0731, calcd. for [C13H9N]+: 179.0735.
1
3-(2-Phenylethynyl)pyridine: H NMR (400 MHz, CDCl3):
d=8.78 (s, 1H), 8.55 (d, J=4.0 Hz, 1H), 7.83–7.80 (m, 1H),
7.57–7.55 (m, 2H), 7.38–7.37 (m, 3H), 7.30–7.28 (m, 1H);
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138.7 (CH), 132.0 (CH), 129.0 (CH), 128.7 (CH), 123.3
(CH), 122.7 (CH), 120.7 (C), 92.9 (C), 86.1 (C); HR-MS
(ESI+): m/z=179.0735, calcd. for [C13H9N]+: 179.0735.
2-Methyl-5-(2-phenylethynyl)pyridine:
1H NMR
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(400 MHz, CDCl3): d=8.66 (s, 1H), 7.70 (d, J=8.0 Hz, 1H),
7.55–7.53 (m, 2H), 7.37–7.35 (m, 3H), 7.16–7.14 (m, 1H),
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4-(2-Phenylethynyl)benzonitrile: 1H NMR (400 MHz,
CDCl3): d=7.55–7.53 (m, 4H, ArH), 7.39–7.33 (m, 5H,
ArH); 13C NMR (100 MHz, CDCl3): d=133.7 (C), 133.6
(CH), 130.8 (CH), 130.1 (CH), 129.8 (CH), 123.8 (CH),
120.2 (C), 113.1 (C), 95.4 (C), 89.4 (C); HR-MS (ESI+): m/
z=203.0738, calcd. for [C15H9N]+: 203.0735.
1-[3-(2-Phenylethynyl)phenyl]ethanone:
1H NMR
(400 MHz, CDCl3): d=8.17 (s, 1H, ArH), 7.97 (d, J=
8.0 Hz, 1H, ArH), 7.77 (d, J=8.0 Hz, 1H, ArH), 7.63–7.61
(m, 2H, ArH), 7.53–7.51 (m, 1H, ArH), 7.43–7.41 (m, 3H,
ArH), 2.68 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3): d=
199.0 (C), 138.8 (C), 137.4 (CH), 133.3 (CH), 133.2 (CH),
130.4 (CH), 130.3 (CH), 130.1 (CH), 129.5 (C), 125.5 (C),
124.4 (CH), 92.0 (C), 90.0 (C), 28.3 (CH); HR-MS (ESI+):
m/z=220.0887, calcd. for [C16H12O]+: 220.0888.
1-Methoxy-4-(prop-1-ynyl)benzene: 1H NMR (400 MHz,
CDCl3): d=7.39 (d, J=8.8 Hz, 2H), 6.88 (d, J=8.8 Hz, 2H),
3.86 (s, 3H), 2.10 (s, 3H); 13C NMR (100 MHz, CDCl3): d=
159.2 (C), 133.0 (C), 116.3 (CH), 114.0 (CH), 84.3 (C), 79.6
(C), 55.4 (CH3), 31.1 (CH3); HR-MS (ESI+): m/z=146.0734,
calcd. for [C10H10O]+: 146.0732.
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Adv. Synth. Catal. 2011, 353, 2731 – 2738