Synthesis of internal alkynes by Pd(PPh3)4/TMEDA-catalyzed Kumada cross-coupling of alkynyl halides with grignard reagents

Article abstract of DOI:10.1002/ejoc.201402558

Alkynes serve as prevalent intermediates in the synthesis of natural products and pharmaceuticals. We here described a new and efficient route to internal alkynes by Pd-catalyzed Kumada cross-coupling reactions of alkynyl halides with Grignard reagents. In the presence of Pd(PPh₃)₄ and N ¹,N ¹,N ²,N ²-tetramethylethane-1,2-diamine (TMEDA), a variety of alkynyl halides underwent Kumada coupling with Grignard reagents, giving the corresponding internal alkynes in moderate to good yields. A new Pd-catalyzed Kumada cross-coupling reaction of alkynyl halides with Grignard reagents has been developed. This transformation provides a new, experimentally simple access to internal alkynes in good yields, and it can accommodate a broad range of substrates with excellent functional group tolerance and good levels of selectivity control.

Full text of DOI:10.1002/ejoc.201402558

FULL PAPER
DOI: 10.1002/ejoc.201402558
Synthesis of Internal Alkynes by Pd(PPh3)4/TMEDA-Catalyzed Kumada
Cross-Coupling of Alkynyl Halides with Grignard Reagents
Mao-Mei Zhang,[a,b] Jun Gong,[c] Ren-Jie Song,*[a] and Jin-Heng Li*[a]
Keywords: Synthetic methods / Cross-coupling / Grignard reaction / Palladium / Alkynes
Alkynes serve as prevalent intermediates in the synthesis of
natural products and pharmaceuticals. We here described a
new and efficient route to internal alkynes by Pd-catalyzed
Kumada cross-coupling reactions of alkynyl halides with
Grignard reagents. In the presence of Pd(PPh3)4 and
N1,N1,N2,N2-tetramethylethane-1,2-diamine (TMEDA),
variety of alkynyl halides underwent Kumada coupling with
Grignard reagents, giving the corresponding internal alk-
ynes in moderate to good yields.
a
bromides and Grignard-derived organocuprates. However,
this latter transformation required a stoichiometric amount
of CuCl to generate Grignard-derived organocuprate rea-
gents in situ. As a continuation of our interest in the cross-
coupling of alkynyl halides with organometallic reagents,
we here report an efficient Pd(PPh3)4-catalyzed Kumada
cross-coupling reaction between alkynyl halides and Grig-
nard reagents by using N1,N1,N2,N2-tetramethylethane-1,2-
diamine (TMEDA) as the ligand; this new method is real-
ized by the introduction of aryl or alkyl groups into the
existing carbon–carbon triple bond, and provides a new ac-
cess to internal alkynes through the Kumada cross-coupling
strategy (Scheme 1, b).
Introduction
Alkynes are important building blocks in synthetic chem-
istry and in materials, biological, and medicinal science.[1–3]
Among the reported methods for the preparation of alk-
ynes, the Sonogashira cross-coupling reaction is considered
as a premium tool.[4,5] Despite impressive progress in the
Sonogashira cross-coupling reaction, it still suffers from dif-
ficulties with respect to the introduction of alkyl groups
into the carbon–carbon triple bond for the synthesis of in-
ternal alkyl alkynes. Therefore, the development of a novel
cross-coupling alternative with which to access internal alk-
ynes would be highly desirable.
An efficient alternative to the assembly of internal alk-
ynes is the cross-coupling of alkynyl halides with organo-
metallic reagents; however, transformations reported to
date that use this approach are much less abundant
(Scheme 1, a).[6–10] For example, the group of Liu and Sun[7]
reported Pd-catalyzed Suzuki-type cross-coupling reaction
between arylacetylenic iodides and arylboronic acids to af-
ford diarylacetylenes. Subsequently, the groups of Tang[8]
and Wang[9] have independently described the Suzuki-type
cross-coupling reaction between arylacetylene iodides using
Pd or Cu as the catalyst. Recently, the group of Botta[10]
developed an iron-catalyzed cross-coupling between alkynyl
Scheme 1. Synthesis of internal alkynes.
[a] State Key Laboratory of Chemo/Biosensing and Chemometrics,
College of Chemistry and Chemical Engineering, Hunan
University,
Changsha 410082, China
Results and Discussion
E-mail: srj0731@hnu.edu.cn;
jhli@hnu.edu.cn
http://cc.hnu.cn/
As shown in Table 1, the reaction of (iodoethynyl)benz-
ene (1a) with PhMgBr (2a) was carried out to establish the
optimal reaction conditions. To our delight, treatment of 1a
with 2a, Pd(PPh3)4, and TMEDA (L1) in tetrahydrofuran
(THF) afforded the desired 1,2-diphenylethyne (3) in 81%
yield (entry 1). Encouraged by the results, a number of
other Pd catalysts, including PdCl2(MeCN)2, Pd(OAc)2,
[b] Department of Pharmacy, Changde Vocational Technical
College,
Changde 415000, China
[c] Department of Agriculture and Forestry Engineering, Changde
Vocational Technical College,
Changde 415000, China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201402558.
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FULL PAPER
and PdCl2, were tested; however, the results showed that (2d), were employed to react with 1a, Pd(PPh3)4 and L1
these conditions were less effective than with Pd(PPh3)4 (en- (entries 1–3). The results demonstrated that both aryl and
try 1 vs. entries 2–4). Whereas 60% yield of 3 was obtained alkyl Grignard reagents were suitable substrates for the re-
when PdCl2(MeCN)2 was used as catalyst (entry 2), a rela- action, giving products 4–6. For example, 2b smoothly
tively low yield of product 3 was observed when Pd(OAc)2 underwent the reaction, giving the desired alkyne 4 in 78%
or PdCl2 were used as catalysts (32 and 25% yields, respec- yield (entry 1). The reaction of 2c with substrate 1a also
tively; entries 3 and 4). However, the absence of palladium afforded the internal alkynes 5 in good yield (entry 2). Grat-
catalysts resulted in no detectable product 3 (entry 5). ifyingly, the optimal conditions were compatible with 2d,
Screening revealed that the amount of Pd(PPh3)4 affected giving the corresponding product 6 in moderate yield (en-
the reaction: whereas identical results to those obtained try 3). Subsequently, the reactions of various alkynyl hal-
with 5 mol-% Pd(PPh3)4 were achieved by increased loading ides, including alkynyl iodides 1b–n, alkynyl bromides 1o–
of Pd(PPh3)4 (10 mol-%; entry 6), only 51% yield was iso- q, and alkynyl chloride 1r, were examined under the optimal
lated at 2 mol-% Pd(PPh3)4 (entry 7). Subsequently, the ef- conditions (entries 4–23). The results indicated that several
fect of ligands was examined. Without ligand, only a low substituents, including Me, MeO, Br, Cl, CN, and CO2Me
yield was isolated (entry 8). Although three other ligands, groups, on the aromatic ring at the terminal alkyne were
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (L2), 1,4-diazabi- well tolerated (entries 4–14). Notably, the nature of the sub-
cyclo[2.2.2]octane (DABCO) (L3) and PCy3 (L4), could im- stituents including position and electronic properties affec-
prove the reaction, they were less effective than TMEDA ted the reaction, and the reactivity order of the substituents
(L1) (entry 1 vs. entries 9–11). Among the reaction tem- was: para Ͼ meta or ortho and electron-donating Ͼ elec-
peratures examined, it turned out that the reaction at 70 °C tron-withdrawing. Whereas substrate 1c, with a p-MeO
gave the best results (entry 1 vs. entries 12 and 13). We group, was treated with 2a or 2c in the presence of Pd(PPh3)4
found that three other solvents, including dimethyl sulfox- and L1, providing the corresponding alkynes 5 and 7 in
ide (DMSO), toluene, and MeCN, also effected the reac- 87 and 85% yield, respectively (entries 5 and 6), substrate
tion, but they were inferior to THF (entry 1 vs. entries 14– 1e, with a m-MeO group, reacted with 2a to give the desired
16).
product 10 in 69% yield (entry 9). Substrates 1b and 1d,
with a p-Me or an o-Me group, furnished products 4 and 9
in 80 and 75% yields, respectively (entries 4 and 8). Al-
though substrate 1h, with an electron-withdrawing CN
group, reacted successfully with aryl or alkyl Grignard rea-
gents 2a or 2d, the yields of the corresponding internal alk-
ynes 13 and 14 were lowered to moderate (entries 12 and
13). Similar results were observed for substrate 1i, having a
p-CO2Me group and an o-Me group (entry 14). Import-
antly, halogen functional groups, Cl and Br, were compati-
ble with the optimal conditions, thereby facilitating ad-
ditional modifications at the halogenated positions (en-
tries 10 and 11). Furthermore, 1-(iodoethynyl)naphthalene
(1j) reacted with 2a to deliver product 16 in 75% yield
(entry 15). We were pleased to find that heteroaryl alkynyl
iodide 1k was viable for the reaction, providing 2-[(4-meth-
oxyphenyl)ethynyl]thiophene (17) in high yield (entry 16).
Although the reactivity of aliphatic iodoalkynes 1l and 1m
was lowered, both delivered the desired products 18 and 19
in moderate yields (entries 17 and 18). It is noted that a
SiMe3 group could be tolerated under the optimal condi-
tions (entry 19).
Table 1. Screening optimal conditions.[a]
Entry [Pd] [mol-%]
L [mol-%] Solvent Isolated yield [%]
1
2
3
4
5
6
7
8
Pd(PPh3)4 (5)
PdCl2(MeCN)2 (5)
Pd(OAc)2 (5)
PdCl2 (5)
L1 (10)
L1 (10)
L1 (10)
L1 (10)
L1 (10)
L1 (20)
L1 (4)
–
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
81
60
32
25
0
80
51
23
57
75
60
73
64
60
38
42
–
Pd(PPh3)4 (10)
Pd(PPh3)4 (2)
Pd(PPh3)4 (5)
Pd(PPh3)4 (5)
Pd(PPh3)4 (5)
Pd(PPh3)4 (5)
Pd(PPh3)4 (5)
Pd(PPh3)4 (5)
Pd(PPh3)4 (5)
Pd(PPh3)4 (5)
Pd(PPh3)4 (5)
9
L2 (10)
L3 (10)
L4 (10)
L1 (10)
L1 (10)
10
11
12[b]
13[c]
14
15
16
Interestingly, the scope of this Kumada cross-coupling
transformation was applicable to alkynyl bromides 1o–q
and alkynyl chloride 1r (entries 20–23). Several alkynyl
bromides 1o–q even having Me and MeO groups on the
aromatic ring at the terminal alkyne, were compatible with
the optimal conditions, although their reactivity was lower
than those of alkynyl iodides (entries 20–22). For example,
L1 (10) DMSO
L1 (10)
L1 (10)
toluene
MeCN
[a] Reaction conditions: 1a (0.3 mmol), 2a (0.36 mmol), [Pd], L and
solvent (2 mL) at 70 °C for 12 h under argon atmosphere. [b] Reac-
tion performed at 90 °C. [c] Reaction performed at 60 °C.
With the optimal conditions in hand, the scope of the p-MeO-substituted substrate 1q underwent the reaction
Kumada cross-coupling reaction was investigated with a with 2a, Pd(PPh3)4 and L1 smoothly, giving the desired
wide range of alkynyl halides (1) and Grignard reagents (2) product 5 in 75% yield (entry 22). It should be noted that
(Table 2). Initially, a number of Grignard reagents, such as moderate yield was still achieved when (chloroethynyl)benz-
4-MeC6H4MgBr (2b), 4-MeOC6H4MgBr (2c) and MeMgBr ene (1r) was used to react with 2a (entry 23).
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Eur. J. Org. Chem. 2014, 6769–6773

Synthesis of Internal Alkynes by Kumada Cross-Coupling
Table 2. Pd/L1-catalyzed Kumada cross-coupling of alkynyl halide
1 with Grignard reagents 2.[a]
On the basis of the present results and on previous re-
ports,[1,6–10] we proposed a reaction mechanism that is out-
lined in Scheme 2. Initially, insertion of the electron-rich
Pd0 complex A into the alkynyl C–X bond of the alkynyl
halide affords an alkynyl-PdII intermediate B. Subsequent
transmetalation with the Grignard reagent forms intermedi-
ate C, then isomerization of intermediate C leads to cis ori-
ented intermediate D. Finally, reductive elimination of in-
termediate D releases the cross-coupled product and regen-
erates the active Pd0 species A.
Scheme 2. Plausible mechanism.
Conclusions
We have developed a new protocol for the synthesis of
internal alkynes by palladium-catalyzed Kumada cross-cou-
pling reaction of alkynyl halides with Grignard reagents by
using TMEDA (L1) as the ligand. This novel method can
be applicable to a wide range of alkynyl halides and Grig-
nard reagents (aryl and alkyl Grignard reagents), and pro-
vides a mild and general access to internal alkynes with
excellent functional group tolerance.
Experimental Section
General Methods: All the materials and solvents were purchased
from commercial suppliers and used without additional purifica-
tion. IR measurements were performed with a FTIR Shimadzu
DR-8000 spectrometer fitted with a Pike Technologies MIRacle
Single Reflection ATR adapter. 1H and 13C NMR spectra were
recorded with a Bruker DRX-500 spectrometer (1H at 500 MHz
and 13C at 125 MHz) or with a Bruker DRX-400 spectrometer (1H
at 400 MHz and 13C at 100 MHz). NMR spectroscopic data were
obtained in CDCl3 unless otherwise noted. High-resolution mass
spectra were recorded with a Bruker microTOF-QII (ESI) spec-
trometer. Preparative thin-layer chromatography was performed on
silica gel plates with PF254 indicator. Flash column chromatog-
raphy was performed with silica gel 60N unless otherwise noted.
Palladium-Catalyzed Kumada Reactions of Alkynyl Halides with
Grignard Reagents. General Procedure: To a Schlenk tube were
added alkynyl halide 1 (0.3 mmol), Grignard reagent 2 (0.36 mol),
Pd(PPh3)4 (5 mol-%), TMEDA (10 mol-%), and THF (2 mL) at
room temperature under an argon atmosphere. The tube was then
stirred at 70 °C for the indicated time until complete consumption
of starting material was observed (reaction monitored by TLC and
GC–MS analysis). Upon completion of the reaction, the mixture
[a] Reaction conditions: 1 (0.3 mmol), 2 (0.36 mmol), Pd(PPh3)4,
TMEDA (10 mol-%), THF (2 mL), 70 °C, 12 h under argon atmo-
sphere. [b] Isolated yield.
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was diluted in diethyl ether, and washed with brine. The aqueous
phase was extracted with diethyl ether and the combined organic
extracts were dried with Na2SO4 and concentrated in vacuo. The
resulting residue was purified by silica gel column chromatography
(hexane/ethyl acetate) to afford the product. Melting points are un-
corrected.
1,2-Diphenylethyne (3):[8c] White solid; m.p. 59.0–61.5 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.54 (d, J = 5.6 Hz, 4 H), 7.34 (s, 6 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 131.6, 128.3, 128.2, 123.2,
89.3 ppm. MS (EI, 70 eV): m/z (%) = 178 (100) [M+].
1-Methyl-4-(phenylethynyl)benzene (4):[8c] White solid; m.p. 70.1–
72.2 °C. 1H NMR (500 MHz, CDCl3): δ = 7.53–7.51 (m, 2 H), 7.42
(d, J = 8.0 Hz, 2 H), 7.35–7.31 (m, 3 H), 7.15 (d, J = 8.0 Hz, 2 H),
2.37 (s, 3 H) ppm. 13C NMR (125 MHz, CDCl3): δ = 138.4, 131.5,
131.5, 129.1, 128.3, 128.1, 123.5, 120.2, 89.6, 88.7, 21.5 ppm. MS
(EI, 70 eV): m/z (%) = 192 (100) [M+].
1-Methoxy-4-(phenylethynyl)benzene (5):[8c] White solid; m.p. 57.0–
59.2 °C. 1H NMR (400 MHz, CDCl3): δ = 7.52–7.46 (m, 4 H), 7.32
(d, J = 6.0 Hz, 3 H), 6.88 (d, J = 7.6 Hz, 2 H), 3.82 (s, 3 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 159.5, 133.0, 131.4, 128.3, 127.9,
123.5, 115.3, 113.9, 89.3, 88.0, 55.3 ppm. MS (EI, 70 eV): m/z (%)
= 208 (100) [M+].
= 8.0 Hz, 2 H), 7.34–7.30 (m, 5 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 134.2, 132.8, 131.5, 128.6, 128.4 (2 C), 122.8, 121.7,
90.3, 88.2 ppm. MS (EI, 70 eV): m/z (%) = 214 (33) [M+ + 2], 212
(100) [M+].
4-(Phenylethynyl)benzonitrile (13):[11b] White solid; m.p. 108.4–
1
110.6 °C. H NMR (400 MHz, CDCl3): δ = 7.44 (d, J = 10.0 Hz,
6 H), 7.26 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 131.8,
131.6 (2 C), 129.0, 128.3, 127.9, 122.0, 118.3, 111.2, 93.6, 87.6 ppm.
MS (EI, 70 eV): m/z (%) = 203 (100) [M+].
4-(Prop-1-ynyl)benzonitrile (14):[11a] Colorless oil. 1H NMR
(400 MHz, CDCl3): δ = 7.57 (d, J = 8.4 Hz, 2 H), 7.45 (d, J =
8.4 Hz, 2 H), 2.08 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 132.0, 131.9, 129.1, 118.6, 110.8, 91.1, 78.6, 4.5 ppm.
Methyl 3-Methyl-4-(phenylethynyl)benzoate (15): White solid; m.p.
119.4–121.1 °C. 1H NMR (400 MHz, CDCl3): δ = 7.88 (s, 1 H),
7.80 (t, J = 7.6 Hz, 1 H), 7.52–7.49 (m, 3 H), 7.31 (d, J = 2.8 Hz,
3 H), 3.87 (s, 3 H), 2.51 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 166.5, 140.0, 131.5, 131.4, 130.2, 129.2, 128.5, 128.2,
127.6, 126.5, 122.8, 96.1, 87.5, 51.9, 20.5 ppm. MS (EI, 70 eV): m/z
(%) = 250 (100) [M+]. HRMS (ESI): m/z calcd. for C17H15O2 [M
+ H]+ 251.1067; found 251.1061.
1-(Phenylethynyl)naphthalene (16):[12] Light-yellow oil. 1H NMR
(400 MHz, CDCl3): δ = 8.45 (d, J = 8.4 Hz, 1 H), 7.82–7.30 (m, 3
H), 7.64–7.61 (m, 2 H), 7.59–7.54 (m, 1 H), 7.50–7.46 (m, 1 H),
7.42–7.38 (m, 1 H), 7.37–7.30 (m, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 133.2 (2 C), 131.6, 130.3, 128.7, 128.4, 128.3 (2 C),
126.7, 126.4, 126.2, 125.2, 123.4, 120.9, 94.3, 87.5 ppm. MS (EI,
70 eV): m/z (%) = 228 (100) [M+].
Prop-1-ynyl-benzene (6):[11a] Colorless oil. 1H NMR (400 MHz,
CDCl3): δ = 7.40–7.37 (m, 2 H), 7.30–7.23 (m, 3 H), 2.04 (s, 3
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 131.4, 128.2, 127.5,
124.0, 85.8, 79.7, 4.3 ppm. MS (EI, 70 eV): m/z (%) = 117 (7) [M+
+ 1], 116 (77) [M+], 115 (100), 89 (12).
1,2-Bis(4-methoxyphenyl)ethyne (7):[12] White solid; m.p. 143.1–
1
144.9 °C. H NMR (400 MHz, CDCl3): δ = 7.45 (d, J = 7.2 Hz, 4
2-[(4-Methoxyphenyl)ethynyl]thiophene (17):[12] Colorless oil. 1H
NMR (400 MHz, CDCl3): δ = 7.44 (d, J = 10.8 Hz, 2 H), 7.24 (t,
J = 2.4 Hz, 2 H), 6.99 (t, J = 4.4 Hz, 1 H), 6.86 (d, J = 8.8 Hz, 2
H), 3.80 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 159.7,
132.9, 131.4, 127.0, 126.8, 123.7, 114.9, 114.0, 93.0, 81.2, 55.2 ppm.
MS (EI, 70 eV): m/z (%) = 184 (100) [M+].
H), 6.87 (d, J = 7.2 Hz, 4 H), 3.82 (s, 6 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 159.3, 132.8, 115.7, 113.9, 87.9, 55.3 ppm.
MS (EI, 70 eV): m/z (%) = 238 (100) [M+].
1-Methoxy-4-(prop-1-ynyl)benzene (8):[11a] Colorless oil. 1H NMR
(400 MHz, CDCl3): δ = 7.32 (d, J = 9.2 Hz, 2 H), 6.81 (d, J =
9.6 Hz, 2 H), 3.77 (s, 3 H), 2.02 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 159.0, 132.7, 116.1, 113.8, 84.1, 79.4, 55.2, 4.2 ppm.
MS (EI, 70 eV): m/z (%) = 147 (19) [M+ + 1], 146 (100) [M+], 131
(47), 103 (75).
1-Methyl-2-(phenylethynyl)benzene (9):[8c] Colorless oil. 1H NMR
(500 MHz, CDCl3): δ = 7.53 (d, J = 7.5 Hz, 2 H), 7.50 (d, J =
7.5 Hz, 1 H), 7.35–7.32 (m, 3 H), 7.22 (d, J = 4.0 Hz, 2 H), 7.22–
7.14 (m, 1 H), 2.52 (s, 3 H) ppm. 13C NMR (125 MHz, CDCl3): δ
= 140.2, 132.5, 131.8, 131.5, 129.4, 128.4, 128.3, 128.1, 125.6, 123.6,
123.0, 93.4, 88.3, 20.7 ppm. MS (EI, 70 eV): m/z (%) = 192 (100)
[M+].
1-Methoxy-3-(phenylethynyl)benzene (10):[12] White solid; m.p.
79.1–79.9 °C. 1H NMR (400 MHz, CDCl3): δ = 7.53–7.49 (m, 2
H), 7.31–7.25 (m, 3 H), 7.20 (t, J = 8.0 Hz, 1 H), 7.12 (d, J =
7.6 Hz, 1 H), 7.06 (s, 1 H), 6.85–6.83 (m, 1 H), 3.72 (s, 3 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 159.3, 131.5, 129.3, 128.2 (2
C), 124.1, 124.0, 123.1, 116.3, 114.8, 89.3, 89.2, 55.0 ppm. MS (EI,
70 eV): m/z (%) = 208 (100) [M+].
Oct-1-ynylbenzene (18):[8c] Colorless oil. 1H NMR (500 MHz,
CDCl3): δ = 7.39–7.38 (m, 2 H), 7.27–7.25 (m, 3 H), 2.43 (t, J =
3.5 Hz, 5 H), 2.27–2.24 (m, 2 H), 1.73–1.69 (m, 6 H) ppm. 13C
NMR (125 MHz, CDCl3): δ = 131.5, 128.2, 127.5, 123.9, 94.2, 84.1,
27.7 (2 C), 27.6 (2 C), 20.4, 18.9 ppm. MS (EI, 70 eV): m/z (%) =
186 (100) [M+].
1-(Dec-1-ynyl)-4-methoxybenzene (19):[12] Colorless oil. 1H NMR
(400 MHz, CDCl3): δ = 7.31 (d, J = 8.8 Hz, 2 H), 6.79 (d, J =
8.8 Hz, 2 H), 3.76 (s, 3 H), 2.37 (t, J = 7.2 Hz, 2 H), 1.62–1.54 (m,
2 H), 1.45–1.40 (m, 2 H), 1.32–1.22 (m, 8 H), 0.88 (t, J = 6.8 Hz,
3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 158.8, 132.7, 116.2,
113.6, 88.6, 80.1, 55.0, 31.7, 29.1, 29.0, 28.8 (2 C), 22.5, 19.3,
14.0 ppm.
Trimethyl(phenylethynyl)silane (20):[11c] Colorless oil. 1H NMR
(400 MHz, CDCl3): δ = 7.28 (d, J = 3.2 Hz, 2 H), 7.10 (s, 3 H),
0.07 (s, 9 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 131.9, 128.4,
128.2, 123.0, 105.1, 94.0, 0 ppm. MS (EI, 70 eV): m/z (%) = 174
(100).
1-Bromo-4-(phenylethynyl)benzene (11):[9] White solid; m.p. 78.0–
Supporting Information (see footnote on the first page of this arti-
1
79.6 °C. H NMR (400 MHz, CDCl3): δ = 7.52 (s, 2 H), 7.47 (d, J
1
cle): H and 13C NMR spectra for internal alkyne products.
= 8.0 Hz, 2 H), 7.39–7.34 (m, 5 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 133.0, 131.6, 131.5, 128.5, 128.4, 122.8, 122.4, 122.2,
90.5, 88.3 ppm. MS (EI, 70 eV): m/z (%) = 258 (100) [M+ + 2], 256
(100) [M+].
Acknowledgments
1-Chloro-4-(phenylethynyl)benzene (12):[9] White solid; m.p. 80.1–
81.9 °C. H NMR (400 MHz, CDCl3): δ = 7.52 (s, 2 H), 7.44 (d, J
The authors thank the China Postdoctoral Science Foundation
(grant number 2012M511716), Hunan Provincial Innovation Foun-
1
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Eur. J. Org. Chem. 2014, 6769–6773

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dation for Postgraduate and Scientific Research Fund of Hunan
Provincial Education Department (grant number 13C012), Hunan
Provincial Natural Science Foundation of China (grant number
13JJ2018), Specialized Research Fund for the Doctoral Program of
Higher Education (grant number 20120161110041), and National
Natural Science Foundation of China (NSFC) (grant number
21172060) for financial support. R.-J. S. also thanks the Funda-
mental Research Funds for the Central Universities.
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Received: May 9, 2014
Published Online: September12, 2014
Eur. J. Org. Chem. 2014, 6769–6773
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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