2,2'-diamino-6,6'-dimethylbiphenyl as an efficient ligand in the CuI-catalyzed sonogashira reaction of aryl iodides and bromides with terminal alkynes

Article abstract of DOI:10.1246/bcsj.20100327

2,2'-Diamino-6,6'-dimethylbiphenyl (L1) was found to be a good ligand in the CuI-catalyzed Sonogashira coupling reaction of various aryl iodides and bromides with terminal alkynes. Under suitable conditions, all reactions gave the desired coupling product

Full text of DOI:10.1246/bcsj.20100327

526
Bull. Chem. Soc. Jpn. Vol. 84, No. 5, 526–530 (2011)
© 2011 The Chemical Society of Japan
2,2¤-Diamino-6,6¤-dimethylbiphenyl as an Efficient Ligand
in the CuI-Catalyzed Sonogashira Reaction of Aryl Iodides
and Bromides with Terminal Alkynes
Bin-Bin Wang, Yue-Mei Ye, Jun-Jun Chen, Xia-Xia Zhou, Jian-Mei Lu, and Li-Xiong Shao*
College of Chemistry and Materials Engineering, Wenzhou University, Chashan University Town,
Wenzhou, Zhejiang 325035, P. R. China
Received November 22, 2010; E-mail: Shaolix@wzu.edu.cn
2,2¤-Diamino-6,6¤-dimethylbiphenyl (L1) was found to be a good ligand in the CuI-catalyzed Sonogashira coupling
reaction of various aryl iodides and bromides with terminal alkynes. Under suitable conditions, all reactions gave the
desired coupling products in moderate to excellent yields.
Acetylenic compounds can be found in a number of natural
Thus, the optimal reaction conditions are established as CuI
(10 mol %) as the catalyst, L1 (10 mol %) as the ligand, NaOH
(2.0 equiv) as the base and DMSO (1.0 mL) as the solvent at the
temperature of 115 °C.
products, bioactive molecules, and other functional materials.1
The palladium and copper cocatalyzed reaction of vinyl halides
with terminal alkynes, known as the Sonogashira reaction, is a
powerful and straightforward method for the construction of
arylated internal alkyne compounds.2,3 However, the high costs
of palladium salts, requirement of copper as cocatalyst, and
usually with high oxophilic phosphine compounds as the
ligand, limit the applications of the Pd/Cu catalytic system in
industrial chemistry. Recently, some new catalytic systems
have been developed in order to overcome these drawbacks.4
Since it was reported that aryl halides could couple with
copper(I) acetylides to give aryl acetylenes,5 there has been a
resurgence in the copper salt catalyzed coupling of aryl halides
with terminal alkynes.6 During our investigations using non-
phosphine-based ligands in the transition-metal-catalyzed
coupling reactions for C-C bond formation,7 it was found that
2,2¤-diamino-6,6¤-dimethylbiphenyl (L1) is a good ligand for
the CuI-catalyzed Sonogashira coupling of aryl iodides and
bromides with terminal alkynes. Herein, we wish to report
these results in detail.
With the optimal reaction conditions in hand, we then
investigated the scope of the CuI-L1-catalyzed Sonogashira
reaction of aryl iodides with terminal alkynes and the results
are summarized in Table 2. As can be seen from Table 2, aryl
iodides containing electron-donating groups such as methoxy
and methyl groups (Entries 2-7) as well as electron-with-
drawing groups such as fluorine and chlorine groups (Entries 8
and 9) reacted with terminal acetylenes to provide arylated
alkynes in good to excellent yields. The reaction of phenyl
iodide (1b) with 4-methoxyphenylacetylene (2b) also gave the
coupling product 3a in 96% yield (Table 2, Entry 1). Sterically
hindered ortho-substituted aryl iodides as 2-methoxyphenyl
iodide (1c) and 2-methylphenyl iodide (1d) also provided good
yields by reacting with terminal alkynes under the identical
reaction conditions (Table 2, Entries 3 and 4). It should be
noted that when 1-bromo-2-iodobenzene (1j) was used, only
the iodine group participated in the reaction to afford 3j in 82%
yield under identical reaction conditions (Table 2, Entry 10).
When strongly electron-withdrawing group substituted aryl
iodides as 4-acetylphenyl iodide (1k), 4-methoxycarbonyl-
phenyl iodide (1l), and 4-nitrophenyl iodide (1m) were used as
the substrates, only trace products were observed (Table 2,
Entries 11-13). It should be noted here that almost no expected
reaction occurred under the identical conditions with 2b and
1-cyclohexenyl iodide as the substrates. Maybe alkenyl iodide
is more labile to decompose under the identical reaction
conditions.
Results and Discussion
In preliminary studies, we used 10 mol % L1 as the ligand
with 10 mol % CuI as the catalyst in the presence of NaOH (2.0
equiv) for the coupling of 4-methoxyphenyl iodide (1a) with
phenylacetylene (2a) in DMF (1.0 mL) at 115 °C for 24 h, and
the corresponding coupling product 3a was isolated in 85%
yield (Table 1, Entry 1). Using other bases such as KOH,
Na2CO3, NaHCO3, KHCO3, K2CO3, and Cs2CO3 under
identical conditions, 3a was obtained in somewhat lower
yields (Table 1, Entries 2-7). For other copper salts such as
Cu2O, Cu powder, and CuO, all showed inferior results
(Table 1, Entries 8-10). When DMSO was used as the solvent
in place of DMF, the yield of 3a can be further increased to
97% (Table 1, Entry 11). Using other analogous diamines L2-
L6 as the ligand, all reactions showed inferior results (Table 1,
Entries 12-16).
The reaction between 1a (0.75 mmol) and 1-hexyne (2c)
(1.5 mmol) was also carried out under identical conditions
(Scheme 1). It was found that only moderate yield of the
coupling product 3k was obtained.
Though under the optimal conditions for the reactions of aryl
iodides with terminal alkynes aryl bromides showed almost no
reactivity, when the reaction of phenyl bromide (1n) with 2b
Published on the web May 7, 2011; doi:10.1246/bcsj.20100327

B.-B. Wang et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 5 (2011)
527
was carried out at 160 °C in DMSO for 48 h, the coupling
product 3a could be also obtained in 47% yield (Table 3,
Entry 1). Increased amount of both CuI and L1 to 20 mol %, 3a
was isolated in 85% yield (Table 3, Entry 2). Then we
examined a variety of aryl bromides with terminal alkynes in
the presence of 20 mol % CuI and 20 mol % L1 and the results
are summarized in Table 3. As can been seen from Table 3,
aryl bromides containing electron-donating groups such as
methoxy and methyl groups (Entries 4-10) as well as electron-
withdrawing group such as chlorine (Entry 3) reacted with
terminal acetylenes to provide the arylated alkynes in moderate
to good yields. For sterically hindered ortho-substituted 2-
methylphenyl bromide (1r), the corresponding arylated alkyne
3d was obtained in 74% yield (Entry 7). When highly sterically
hindered 2,6-dimethylphenyl bromide (1u) was used as the
substrate, product 3n was obtained only in 44% yield
(Entry 10). It should be noted here that when 4-methoxyphenyl
bromide (1p) was used as the substrate, the corresponding
product 3b was obtained in 86% yield in the presence of
10 mol % CuI and 10 mol % L1 (Entry 4).
Though the real mechanism for this copper-catalyzed
Sonogashira coupling reaction remains unclear at this stage, a
proposed one is shown below,8 where L1 means 2,2¤-diamino-
6,6¤-dimethylbiphenyl. First, CuI will coordinate with L1 to
form intermediate I, which is believed to be the active species
in this catalytic cycle. Then intermediate II will be achieved via
reaction of alkynes 2 with I in the presence of a base.
Subsequently, oxidative addition of aryl iodides 1 to inter-
mediate II will give intermediate III. Finally, products 3 will
be formed via reductive elimination of intermediate III,
releasing active species I to complete the catalytic cycle
(Scheme 2).
Table 1. Optimization for the Copper-Catalyzed Coupling
Reaction of 1a with 2a
I
[Cu], [L], Base
OMe
+
Solvent, 115 °C
3a
24 h
OMe
1a
2a
NH2
NH2
MeO
NH2
NH2
L3:
L2:
Me
NH2
NH2
MeO
L1:
Me
Table 2. CuI-Catalyzed Sonogashira Coupling of Iodides 1
with Terminal Alkynes 2
NHMe
NMe2
NMe2
NHMe
NHMe
L6:
L5:
L4:
NMe2
I
CuI, L1
+
Entrya)
[Cu]
[L]
Base
Solvent
Yield/%b)
NaOH, DMSO
R2
R1
R2
R1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CuI
CuI
CuI
CuI
CuI
CuI
CuI
Cu2O
Cu
CuO
CuI
CuI
CuI
CuI
CuI
CuI
L1
L1
L1
L1
L1
L1
L1
L1
L1
L1
L1
L2
L3
L4
L5
L6
NaOH
KOH
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
85
64
81
57
79
82
<10
73
48
79
97
43
42
46
34
45
2
115 °C, 24 h
1
3
Entrya)
1 (R1)
1b (H)
2 (R2)
Yield/%b)
Na2CO3
NaHCO3
KHCO3
K2CO3
Cs2CO3
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
1
2
3
4
5
6
7
8
9
10
11
12
13
2b (4-OMe)
3a (96)
3b (98)
3c (80)
3d (88)
3e (98)
3f (99)
3g (90)
3h (86)
3i (74)
3j (82)
trace
1a (4-OMe)
1c (2-OMe)
1d (2-Me)
1e (3,5-Me2)
1f (3-Me)
1g (4-Me)
1h (4-Cl)
2b
2a (H)
2b
2b
2b
2b
2b
2b
2b
DMF
DMF
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
1i (4-F)
1j (2-Br)
1k (4-Ac)
1l (4-CO2Me)
1m (4-NO2)
2b
2a
2b
trace
<5
a) All reactions were carried out using 1a (0.75 mmol) and 2a
(0.90 mmol) in the presence of [Cu] (10 mol %) and [L]
(10 mol %) in the listed base (2.0 equiv) and solvent (1.0 mL)
at 115 °C for 24 h. b) Isolated yields.
a) All reactions were carried out using 1 (0.75 mmol), 2
(0.90 mmol), NaOH (1.5 mmol) in the presence of CuI
(10 mol %) and L1 (10 mol %) in DMSO (1.0 mL) at 115 °C
for 24 h. b) Isolated yields.
I
CuI, L1
MeO
+
NaOH, DMSO
115 °C, 24 h
2c
3k, 50%
OMe
1a
Scheme 1. CuI-catalyzed reaction of 4-methoxyphenyl iodide (1a) with 1-hexyne (2c).

528
Bull. Chem. Soc. Jpn. Vol. 84, No. 5 (2011)
An Efficient Ligand in a CuI-Catalyzed Sonogashira Reaction
Table 3. CuI-Catalyzed Sonogashira Coupling of Bromides
1 with Terminal Alkynes 2
J-values are in Hertz. DMF and DMSO were distilled from
CaH2 under reduced pressure. Commercially obtained reagents
were used without further purification. Flash column chroma-
tography was carried out using Huanghai 300-400 mesh silica
gel at increased pressure.
General Procedure for the CuI-L1-Catalyzed
Sonogashira Reaction of Aryl Iodides with Terminal
Alkynes. If Aryl Iodide is a Liquid: Under N2 atmosphere,
CuI (10 mol %), L1 (10 mol %), NaOH (2.0 equiv), and
degassed DMSO (1.0 mL) were added into a Schlenk reaction
tube, then aryl iodide 1 (0.75 mmol) and terminal alkyne 2
(0.90 mol) were added. The mixture was stirred at 115 °C for
24 h. Then the solvent was diluted with EtOAc, washed with
brine, and dried over anhydrous Na2SO4. The product was
purified by flash column chromatography (SiO2) to give pure
product 3.
If Aryl Iodide is a Solid: Under N2 atmosphere, aryl
iodide 1 (0.75 mol), CuI (10 mol %), L1 (10 mol %), NaOH (2.0
equiv), and degassed DMSO (1.0 mL) were added into a
Schlenk reaction tube, then terminal alkyne 2 (0.90 mol) was
added. The mixture was stirred at 115 °C for 24 h. Then the
solvent was diluted with EtOAc, washed with brine, and dried
over anhydrous Na2SO4. The product was purified by flash
column chromatography (SiO2) to give pure product 3.
General Procedure for the CuI-L1-Catalyzed
Sonogashira Reaction of Aryl Bromides with Terminal
Br
CuI, L1
NaOH, DMSO
160 °C, 48 h
+
R2
R1
R2
R1
3
1
2
Entrya)
1 (R1)
2 (R2)
Yield/%b)
1c)
2
1n (H)
1n (H)
2b (4-OMe)
2b (4-OMe)
2b
2b
2b
2b
2b
2b
3a (47)
3a (85)
3h (74)
3b (86)
3l (72)
3l (91)
3d (74)
3g (86)
3m (60)
3n (44)
3
1o (4-Cl)
1p (4-OMe)
1q (3-OMe)
1q
1r (2-Me)
1s (4-Me)
1t (3-OMe)
1u (2,6-Me2)
4c)
5c)
6
7
8
9
10
2a (H)
2b
a) Otherwise specified, all reactions were carried out using 1
(0.75 mmol), 2 (0.90 mmol), NaOH (1.5 mmol) in the presence
of CuI (20 mol %) and L1 (20 mol %) in DMSO (1.0 mL) at
160 °C for 48 h. b) Isolated yields. c) CuI (10 mol %) and L1
(10 mol %) were used.
CuI
L1
Alkynes.
Under N2 atmosphere, CuI (20 mol %), L1
(20 mol %), NaOH (2.0 equiv), and degassed DMSO (1.0 mL)
were added into a Schlenk reaction tube, then aryl bromide 1
(0.75 mmol) and terminal alkyne 2 (0.90 mol) were added. The
mixture was stirred at 160 °C for 48 h. Then the solvent was
diluted with EtOAc, washed with brine, and dried over
anhydrous Na2SO4. The product was purified by flash column
chromatography (SiO2) to give pure product 3.
R
R'
R
H + NaOH
L1 CuI
3
2
I
NaI + H2O
R
R'
L1 Cu
1
4-(Phenylethynyl)anisole (3a):9 A white solid. H NMR
L1 Cu
R
II
(CDCl3, 300 MHz, TMS): ¤ 3.76 (s, 3H, OCH3), 6.84 (d, J =
9.0 Hz, 2H, Ar), 7.29-7.31 (m, 3H, Ar), 7.44-7.52 (m, 4H, Ar).
13C NMR (CDCl3, 125 MHz, TMS): ¤ 55.3, 88.1, 89.4, 114.0,
115.4, 123.6, 127.9, 128.3, 131.4, 133.0, 159.6.
1,2-Bis(4¤-methoxyphenyl)ethyne (3b):9 A white solid.
1H NMR (CDCl3, 300 MHz, TMS): ¤ 3.82 (s, 3H, OMe), 6.86
(d, J = 8.1 Hz, 2H), 7.45 (d, J = 8.1 Hz, 2H, Ar). 13C NMR
(CDCl3, 125 MHz, TMS): ¤ 55.2, 87.9, 113.9, 115.7, 132.8,
159.3.
2-(Phenylethynyl)anisole (3c):10 A thick-yellow liquid.
1H NMR (CDCl3, 500 MHz, TMS): ¤ 3.89 (s, 3H, OCH3),
6.88-6.94 (m, 2H, Ar), 7.29-7.33 (m, 4H, Ar), 7.50 (dd, J =
7.6, 1.7 Hz, 1H, Ar), 7.56 (dd, J1 = 7.7, 1.5 Hz, 2H, Ar).
13C NMR (CDCl3, 125 MHz, TMS): ¤ 55.9, 85.7, 93.4, 110.7,
112.4, 120.4, 123.5, 128.1, 128.2, 129.7, 131.6, 133.5, 159.9.
4-(2¤-Methylphenylethynyl)anisole (3d):11 A white solid.
1H NMR (CDCl3, 300 MHz, TMS): ¤ 2.50 (s, 3H, CH3), 3.81
(s, 3H, OCH3), 6.87 (dd, J = 6.8, 3.4 Hz, 2H, Ar), 7.14-7.23
(m, 3H, Ar), 7.44-7.48 (m, 3H, Ar). 13C NMR (CDCl3,
125 MHz, TMS): ¤ 20.7, 55.2, 87.0, 93.3, 114.0, 115.6,
123.3, 125.5, 127.9, 129.4, 131.6, 132.9, 139.9, 159.5.
I
III
R'I
1
Scheme 2. Proposed mechanism.
Conclusion
In conclusion, we have found that 2,2¤-diamino-6,6¤-di-
methylbiphenyl (L1), as a non-phosphine, air-stable, and easily
available compound, is an efficient ligand in the CuI-catalyzed
Sonogashira coupling reaction of various aryl iodides and
bromides with terminal alkynes under the appropriate reaction
conditions. Both aryl iodides and bromides react with terminal
alkynes to provide the corresponding coupling products in high
yields. Efforts are underway to disclose other applications of
this ligand in this laboratory.
Experimental
General Remarks. 1H and 13C NMR spectra were recorded
on a Bruker Avance-300 or 500 MHz spectrometer for solution
in CDCl3 with tetramethylsilane (TMS) as an internal standard;
4-(3¤,5¤-Dimethylphenylethynyl)anisole (3e):
A white
solid. Mp: 41-42 °C. 1H NMR (CDCl3, 500 MHz, TMS): ¤
2.28 (s, 6H, CH3), 3.77 (s, 3H, OCH3), 6.84 (d, J = 9.0 Hz, 2H,

B.-B. Wang et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 5 (2011)
529
Ar), 6.92 (s, 1H, Ar), 7.14 (s, 2H, Ar), 7.44 (d, J = 9.0 Hz, 2H,
Ar). 13C NMR (CDCl3, 125 MHz, TMS): ¤ 21.0, 55.1, 88.4,
88.6, 113.9, 115.5, 123.1, 129.1, 129.8, 132.9, 137.8, 159.4.
MS (EI) m/z: 202 (M+, 6), 142 (100), 141 (81), 128 (48), 115
(18), 91 (17). HRMS (EI) Calcd for C17H16O requires
236.1201, Found: 202.0990. IR (neat): ¯ 3037, 2834, 2360
TMS): ¤ 55.3, 89.2, 89.3, 114.9, 116.3, 123.2, 124.2, 124.3,
128.27, 128.32, 129.4, 131.6, 159.4.
4-(2¤,6¤-Dimethylphenylethynyl)anisole (3n):
A white
solid. Mp: 69-70 °C. 1H NMR (CDCl3, 500 MHz, TMS): ¤
2.50 (s, 6H, CH3), 3.83 (s, 3H, OCH3), 6.88 (d, J = 9.0 Hz, 2H,
Ar), 7.05-7.12 (m, 3H, Ar), 7.47 (d, J = 9.0 Hz, 2H, Ar).
13C NMR (CDCl3, 125 MHz, TMS): ¤ 21.1, 55.3, 85.8, 97.8,
114.0, 116.0, 123.3, 126.6, 127.4, 132.8, 140.0, 159.5. MS (EI)
m/z: 202 (M+, 6), 142 (100), 141 (81), 128 (48), 115 (18), 91
(17). HRMS (EI) Calcd for C17H16O requires 236.1201, Found:
202.0990. IR (neat): ¯ 3003, 2956, 2921, 2852, 1603, 1511,
(C≡C), 2342 (C≡C), 1606, 1595, 1508, 1457, 1288, 1266,
¹1
1246, 1173, 1106, 1032, 849, 831, 738, 703 cm
.
4-(3¤-Methylphenylethynyl)anisole (3f):9 A yellow liquid.
1H NMR (CDCl3, 500 MHz, TMS): ¤ 2.33 (s, 3H, CH3), 3.79
(s, 3H, OCH3), 6.86 (d, J = 8.5 Hz, 2H, Ar), 7.11 (d, J =
8.0 Hz, 1H, Ar), 7.21 (t, J = 8.0 Hz, 1H, Ar), 7.31-7.34 (m, 2H,
Ar), 7.46 (d, J = 8.5 Hz, 2H, Ar). 13C NMR (CDCl3, 125 MHz,
TMS): ¤ 21.2, 55.2, 88.2, 89.0, 113.9, 115.4, 123.3, 128.2,
128.5, 128.8, 132.0, 133.0, 137.9, 159.5.
1465, 1441, 1377, 1287, 1246, 1182, 1169, 1106, 1025, 832,
¹1
809, 790, 768, 732 cm
.
Financial support from the National Natural Science
Foundation of China (Nos. 21002072 and 20702013),
the Department of Education of Zhejiang Province
(No. Y200907072), and the start-up fund of Wenzhou Uni-
versity is greatly acknowledged. Xia-Xia Zhou thanks the
Science and Technology Department of Zhejiang Province
(No. 2009R424017) for financial support.
4-(4¤-Methylphenylethynyl)anisole (3g):12 A white solid.
1H NMR (CDCl3, 500 MHz, TMS): ¤ 2.36 (s, 3H, CH3), 3.82
(s, 3H, OCH3), 6.87 (d, J = 8.5 Hz, 2H, Ar), 7.14 (d, J =
8.0 Hz, 2H, Ar), 7.40 (d, J = 8.0 Hz, 2H, Ar), 7.46 (d, J =
8.5 Hz, 2H, Ar). 13C NMR (CDCl3, 125 MHz, TMS): ¤ 21.5,
55.3, 88.2, 88.7, 114.0, 115.6, 120.5, 129.1, 131.3, 133.0,
138.0, 159.5.
4-(4¤-Chlorophenylethynyl)anisole (3h):12 A white solid.
1H NMR (CDCl3, 300 MHz, TMS): ¤ 3.81 (s, 3H, OCH3), 6.87
(d, J = 8.9 Hz, 2H, Ar), 7.30 (d, J = 8.6 Hz, 2H, Ar), 7.42 (d,
J = 8.6 Hz, 2H, Ar), 7.47 (d, J = 8.9 Hz, 2H, Ar). 13C NMR
(CDCl3, 125 MHz, TMS): ¤ 55.3, 87.0, 90.4, 114.1, 115.0,
122.2, 128.6, 132.6, 133.1, 133.9, 159.8.
Supporting Information
1H NMR and 13C NMR spectra of selected compounds. This
material is available free of charge on the web at http://
www.csj.jp/journals/bcsj/.
References
4-(4¤-Fluorophenylethynyl)anisole (3i):13 A white solid.
1H NMR (CDCl3, 500 MHz, TMS): ¤ 3.83 (s, 3H, OCH3), 6.88
(d, J = 8.5 Hz, 2H, Ar), 7.03 (t, J = 8.5 Hz, 2H, Ar), 7.45-7.50
(m, 4H, Ar). 13C NMR (CDCl3, 125 MHz, TMS): ¤ 55.3, 87.0,
1
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89.0, 114.0, 115.2, 115.6 (d, JC-F = 22 Hz), 119.7 (d, JC-F
=
3.5 Hz), 133.0, 133.3 (d, JC-F = 8.1 Hz), 159.7, 162.3 (d,
J
C-F = 247.5 Hz).
4-(2¤-Bromophenylethynyl)anisole (3j):14 A pale-yellow
solid. 1H NMR (CDCl3, 300 MHz, TMS): ¤ 3.82 (s, 3H,
OCH3), 6.87 (d, J = 9.0 Hz, 2H, Ar), 7.14 (td, J = 7.8, 1.8 Hz,
1H, Ar), 7.27 (td, J = 7.8, 1.2 Hz, 1H, Ar), 7.50-7.54 (m, 3H,
Ar), 7.59 (dd, J = 13.0, 1.5 Hz, 1H, Ar). 13C NMR (CDCl3,
125 MHz, TMS): ¤ 55.3, 86.8, 94.0, 114.0, 114.9, 125.4, 125.7,
127.0, 129.0, 132.3, 133.0, 133.1, 159.9.
2
K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett.
1-Hex-1-ynyl-4-methoxybenzene (3k):15
A colorless
1975, 16, 4467.
liquid. 1H NMR (500 MHz, CDCl3): ¤ 7.29 (d, J = 8.5 Hz,
2H), 6.80 (d, J = 8.5 Hz, 2H), 3.79 (s, 3H), 2.38 (t, J = 7.0 Hz,
2H), 1.26-1.6 (m, 7H).
3
For some reviews of Sonogashira reaction, please see: a) K.
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4-(3¤-Methoxyphenylethynyl)anisole (3l):16
A yellow
liquid. 1H NMR (CDCl3, 500 MHz, TMS): ¤ 3.785 (s, 3H,
OCH3), 3.787 (s, 3H, OCH3), 6.86 (d, J = 8.5 Hz, 3H, Ar), 7.04
(dd, J = 2.0, 1.5 Hz, 1H, Ar), 7.10-7.11 (t, J = 1.5 Hz, 1H, Ar),
7.22 (t, J = 8.0 Hz, 1H, Ar), 7.46 (d, J = 8.5 Hz, 2H, Ar).
13C NMR (CDCl3, 125 MHz, TMS): ¤ 55.18, 55.19, 88.0, 89.2,
114.0, 114.6, 115.2, 116.2, 124.0, 124.6, 129.3, 133.0, 159.3,
159.6.
3-(Phenylethynyl)anisole (3m):17
A pale-yellow solid.
1H NMR (CDCl3, 500 MHz, TMS): ¤ 3.81 (s, 3H, OCH3), 6.89
(dd, J = 8.5, 2.5 Hz, 1H, Ar), 7.06 (s, 1H, Ar), 7.13 (d,
J = 7.5 Hz, 1H, Ar), 7.23-7.26 (m, 1H, Ar), 7.32-7.34 (m, 3H,
Ar), 7.53-7.54 (m, 2H, Ar). 13C NMR (CDCl3, 125 MHz,

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