Nickel-Catalyzed Hiyama-type Decarboxylative Coupling of Propiolic Acids and Organosilanes

Article abstract of DOI:10.1021/acs.joc.6b00883

A Ni catalytic system was developed for the decarboxylative coupling reaction of alkynyl carboxylic acids with organosilanes. Ni(acac)₂ and 1,10-phenanthroline showed the best result in the presence of CsF and CuF₂ at 120 °C. This system tolerated the presence of alkyl, alkoxy, halogen, nitro, cyano, ketone, and ester functional groups. Moreover, the reaction with but-2-ynedioic acid and organosilane afforded the corresponding symmetrical diarylalkynes.

Full text of DOI:10.1021/acs.joc.6b00883

Subscriber access provided by University of Sussex Library
Note
Nickel-Catalyzed Hiyama-Type Decarboxylative
Coupling of Propiolic Acids and Organosilanes
Gabriel Charles Edwin Raja, Francis Mariaraj Irudayanathan, Han-Sung Kim, Jimin Kim, and Sunwoo Lee
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b00883 • Publication Date (Web): 18 May 2016
Downloaded from http://pubs.acs.org on May 19, 2016
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
The Journal of Organic Chemistry is published by the American Chemical Society.
1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 24
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
NickelꢀCatalyzed HiyamaꢀType Decarboxylative
Coupling of Propiolic Acids and Organosilanes
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Gabriel Charles Edwin Raja,† Francis Mariaraj Irudayanathan,† Han-Sung Kim†, Jimin Kim†*
and Sunwoo Lee†*
†Department of Chemistry, Chonnam National University, Gwangju, 61186, Republic of Korea
Corresponding Author: J. Kim (jiminkim@chonnam.ac.kr), S. Lee (sunwoo@chonnam.ac.kr)
Keywords: nickel, CꢀC coupling, organosilane, Hiyama coupling, decarboxylative coupling,
propiolic acids.
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 2 of 24
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Abstract
A Ni catalytic system was developed for the decarboxylative coupling reaction of alkynyl
carboxylic acids with organosilanes. Ni(acac)2 and 1,10ꢀphenanthroline showed the best result in
the presence of CsF and CuF2 at 120 °C. This system tolerated the presence of alkyl, alkoxy,
halogen, nitro, cyano, ketone, and ester functional groups. Moreover, the reaction with butꢀ2ꢀ
ynedioic acid and organosilane afforded the corresponding symmetrical diarylalkynes.
ACS Paragon Plus Environment

Page 3 of 24
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Efforts have been made to replace precious metals with more abundant and lowꢀcost metals in
transitionꢀmetalꢀcatalyzed reactions.1 Compared to Pd, Ni catalytic systems have been less
developed for coupling reactions even though Ni is less expensive.2 Like other coupling
reactions, Pd has been successfully introduced in the Sonogashira reaction involving the
coupling of aryl halides and terminal alkynes.3 Sonogashira reaction is one of the most important
methods for the preparation of valuable building blocks in pharmaceuticals, natural products, and
polymers.4 As a terminal alkyne surrogate, alkynyl carboxylic acids have received much
attention since we first reported the Pdꢀcatalyzed decarboxylative coupling reaction in 2008.5
Since then, diverse decarboxylative coupling reactions have been reported by our group and
others.6Decarboxylative crossꢀcoupling reactions have been studied not only in the formation of
carbonꢀcarbon bonds, but also in the formation of carbonꢀheteroatom bonds.7 However, only one
example of Ni catalyst was found for the spꢀcarbon decarboxylative coupling reactions(Figure
1a),8 whereas several examples of Niꢀcatalyzed decarboxylative reaction with both sp2 and sp3
carboxylic acids have been reported.9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
In the case of the decarboxylative coupling reaction of alkynyl carboxylic acids, aryl halides
such as iodides, bromides, and chlorides have mostly been used as the coupling partner; benzyl
halides have also been used (Figure 1b).10 The reactions with terminal alkynes or homocoupling
of alkynyl carboxylic acids provided the corresponding diynes.11 Moreover, oxidative
decarboxylative coupling reactions with C–H activated compounds or aryl boronic acids have
also been developed (Figure 1c).12 However, organosilane compounds have never been used as
the coupling partner in decarboxylative coupling reactions with alkynyl carboxylic acids, even
though they have several advantages such as storage and handling because of their good
stability.13 Mostly, they have been used as the coupling substrates in Hiyama coupling
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 4 of 24
1
2
reactions14and recently used in the Niꢀcatalyzed C–H arylation of heteroarenes.15 Moreover, only
a few examples of Sonogashira–Hiyamaꢀtype coupling reactions have been reported; all of them
used Pd as the catalyst.16 To the best of our knowledge, Niꢀcatalyzed reactions have not been
reported (Figure 1d). Herein, we report a Niꢀcatalyzed decarboxylative coupling reaction of
alkynyl carboxylic acids with organosilanes as the coupling partner for the first time (Figure 1e).
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1.Metalꢀcatalyzed sp carbon coupling reactions.
To optimize the reaction conditions, the reaction of phenyl propiolic acid 1a with
triethoxysilylbenzene2a was selected as the model reaction as shown in Table 1. Among the Ni
sources and solvents investigated, Ni(acac)2 and DMSO showed the best result (See Supporting
Information). With 2,2'ꢀbipyridine as the ligand, several oxidants were investigated. Oxygen and
AgF2 afforded the undesired decarboxylativehomocoupled product 4a in high yields (entries 1
and 2). Among the oxidants such as Ag2O, Ag2CO3, Cu(OAc)2, Cu(OTf)2, and CuF2, CuF2
afforded the highest yield of product 3a (entry 7). The use of TBAF and KF instead of CsF did
not give satisfactory results (entries 8 and 9). Alkyl substituted 2,2′ꢀbipyridines afforded lower
ACS Paragon Plus Environment

Page 5 of 24
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
yields than 2,2′ꢀbipyridine (entries 10 – 12). When 1,10ꢀphenanthroline derivatives were used as
the ligand, 1,10ꢀphenanthroline provided the desired product 3a in 90% yield (entry 13).
However, methyl or phenylꢀsubstituted 1,10ꢀphenanthroline showed lower yields (entries 14 and
15). In the absence of a ligand, the yield of the product was 30% (entry 16). Phosphine ligands
decreased the yield of 3a (entries 17 and 18). The reaction at 100 °C afforded 3a in 63% yield
(entry 19). The reaction yields were not changed when the reaction was conducted under
nitrogen atmosphere (entry 20).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 1. Optimization of decarboxylative coupling reaction.a
Yield (%)e
Entry
Ligandb
Additive
Oxidant
3a
4a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19c
Bipy
Bipy
Bipy
Bipy
Bipy
Bipy
Bipy
Bipy
Bipy
CsF
CsF
CsF
CsF
CsF
CsF
CsF
TBAF
KF
CsF
CsF
CsF
CsF
CsF
CsF
CsF
CsF
CsF
CsF
O2
AgF2
2
4
6
83
85
28
35
71
15
13
30
15
21
33
45
8
19
18
19
35
34
31
Ag2O
Ag2CO3
Cu(OAc)2
Cu(OTf)2
CuF2
35
13
28
79
15
41
45
12
61
90
47
36
30
8
CuF2
CuF2
CuF2
CuF2
CuF2
CuF2
CuF2
CuF2
CuF2
CuF2
CuF2
CuF2
tBu2bipy
Me2bipy
Me4bipy
Phen
Ph2Phen
Me2Phen
ꢀ
Xantphos
dppf
15
63
Phen
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 6 of 24
1
2
20d
Phen
CsF
CuF2
90
8
3
4
5
6
7
8
9
aReaction conditions: 1a (0.3 mmol), 2a (0.45 mmol), Ni(acac)2 (0.03 mmol), ligand
(0.03 mmol), CsF (0.3 mmol), and CuF2 (0.3 mmol) were stirred in DMSO (1.5 mL) at
120 °C for 12 h. bLigand : Bipy = 2,2′ꢀbipyridine; tBu2bipy = 4,4′ꢀdiꢀtBuꢀ2,2′ꢀbipyridine;
Me2bipy
=
4,4′ꢀdimethylꢀ2,2′ꢀbipyridine; Me4bipy
=
4,4′,5,5′ꢀtetramethylꢀ2,2′ꢀ
bipyridine; Ph2Phen = 4,7ꢀdiphenylꢀ1,10ꢀphenanthroline; Me2Phen = 4,7ꢀdimethylꢀ1,10ꢀ
phenanthroline; Phen = 1,10ꢀphenanthroline; Xantphos = 4,5ꢀbis(diphenylphosphino)ꢀ
9,9ꢀdimethylxanthene; dppf = 1,1′ꢀbis(diphenylphosphino)ꢀferrocene. 100 °C. Under
nitrogen atmosphere. eYield was determined by GC with internal standard.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
c
d
With this optimized reaction conditions in hand, the reactions of diverse alkynyl carboxylic acids
with triethoxysilylbenzene were evaluated. The results are summarized in Scheme 1.
Arylpropiolic acids were prepared by the modified known methods.17As expected, phenyl
propiolic acid afforded 3a in 90% isolated yield. Phenyl propiolic acids bearing methyl groups
provided 3b, 3c, and 3d in good yields. Alkoxyꢀsubstituted phenyl propiolic acids also showed
good yields for 3e, 3f, and 3g. 2ꢀNaphthyl group substituted propiolic acids furnished 3h and 3i
in 85% and 82%yields, respectively. Halo groups also afforded the desired coupling products 3j,
3k, and 3l ingood yields. Biphenylꢀsubstituted 3m was obtained in 77% yield. Phenyl propiolic
acids bearing nitro, cyano, ketone, and ester groups at the para position afforded the
corresponding products 3n, 3o, 3p, and 3q in 57%, 66%, 75%, and 69% yields, respectively. The
reaction of 2ꢀpyridinyl propiolic acid provided 54% yield. Unfortunately, no desired products 3s
and 3t were obtained from the alkylꢀsubstituted propiolic acids such as octynoic acid and
pentynoic acid.
Scheme 1.Decarboxylative coupling of aryl alkynyl carboxylic acids and triethoxysilylbenzene.a
ACS Paragon Plus Environment

Page 7 of 24
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
10 mol% Ni(acac)2
10 mol% 1,10-Phen
+
R
CO2H
(EtO)3Si Ph
2a
+
Ph
R
R
R
CsF (1.0 equiv)
CuF2 (1.0 equiv)
DMSO, 120 oC, 12 h
4b
3
1
9
Me
Me
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Me
Ph
Ph
Ph
3b (78%)
OMe
3a(90%)
3c (79%)
Me
MeO
Me
Ph
Ph
Ph
3e (72%)
3d (71%)
3g (82%)
3f (77%)
O
MeO
O
Ph
Ph
Ph
3i (82%)
3h (85%)
3k (81%)
Cl
F3C
Ph
F
Ph
Ph
3j (82%)
3l (66%)
3o (66%)
O2N
Ph
Ph
Ph
3m (77%)
NC
Ph
3n (57%)
O
O
Ph
Ph
Ph
N
MeO
Me
3r (54%)
3p (75%)
3q (69%)
n-C5H11
3s (0%)
Ph
n-C2H5
3t (0%)
Ph
aReaction condition : 1 (2.0 mmol), 2a (3.0 mmol), Ni(acac)2 (0.2 mmol), 1,10ꢀphenanthroline
(0.2 mmol), CsF (2.0 mmol) and CuF2 (2.0 mmol) were reacted in DMSO (7.0 mL) at 120 oC for
12 h. bLess than 5% yield was formed.
The reaction with other organosilanes were evaluated for this coupling reaction. As shown in
Scheme 2, pꢀtolyl, 4ꢀmethoxylphenyl, 4ꢀchlorophenyl, and 2ꢀthiophenyl silanes were coupled
with aryl alkynyl carboxylic acids, affording the corresponding products in good yields.
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 8 of 24
1
2
3
4
5
6
Scheme 2.Decarboxylative coupling of aryl alkynyl carboxylic acids with triethoxyarylsilanes.a
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Ar1
CO2H
10 mol% Ni(acac)2
10 mol% 1,10-Phen
1
+
Ar1
Ar2
CsF (1.0 equiv)
CuF2 (1.0 equiv)
DMSO, 120 oC, 12 h
Ar2
(EtO)3Si
5
2
O
Me
Me
Me
Me
5b (81%)
5a (78%)
OMe
OMe
Cl
5d (74%)
5f (79%)
5c (86%)
5e (90%)
S
aReaction condition : 1 (2.0 mmol), 2 (3.0 mmol), Ni(acac)2 (0.2 mmol), 1,10ꢀphenanthroline
(0.2 mmol), CsF (2.0 mmol) and CuF2 (2.0 mmol) were reacted in DMSO (7.0 mL) at 120 oC for
12 h.
To extend this methodology to the synthesis of symmetrical diaryl alkynes, 3 equiv of
triethoxylsilyl benzene was reacted with propiolic acid (6a) under the optimized reaction
conditions. Unfortunately, no desired product was obtained as shown in Table 2 (entry 1).
However, the reaction with butꢀ2ꢀynedioic acid (6b) provided diphenyl acetylene in 21% yield
(entry 2). When the amount of CuF2 and CsF was doubled, the desired product was obtained in
42% yield (entry 3). Triethoxy(4ꢀmethylphenyl)silane and triethoxyl(4ꢀchlorophenyl)silane also
ACS Paragon Plus Environment

Page 9 of 24
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
afforded the corresponding products 7b and 7c in 38% and 45% yields, respectively (entry 5).
Table 2. Synthesis of symmetrical diarylacetylenes.a
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Entry
Ar
CsF, CuF2
Product
Yield(%)
6
1
2
3
4
5
C6H5
C6H5
1 equiv
1 equiv
2 equiv
2 equiv
2 equiv
ꢀ
ꢀ
6a
6b
6b
6b
6b
7a(3a)
7a(3a)
7b
21
42
38
45
C6H5
4ꢀMe C6H4
4ꢀCl C6H4
7c
a2a (6.0 mmol), 6b (2.0 mmol), Ni(acac)2 (0.4mmol), 1,10ꢀPhenanthroline (0.4mmol),
CsF(2.0 or 4.0mmol), and CuF2 (2.0 or 4.0mmol) were reacted in DMSO at 120 °C for 12 h.
To elucidate the reaction mechanism, the standard conditions were investigated by changing the
parameters as shown in Table 3. In the presence of TEMPO, the yield of 3a decreased, and that
of 4a increased (entry 2). Without CuF2, no product was obtained (entry 3). Biphenyl (8), a
homocoupling product of 2a, was obtained in the absence of CsF (entry 4). Without the Ni
catalyst/ligand, the yield of 3a decreased to 30% (entry 5). In the absence of both Ni and CsF, the
yield of 8 increased to 50% (entry 6). When the reaction was conducted in the absence of nickel
showed 41% yield of product (entry 7).
Table 3. Studies of reaction pathway.a
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 10 of 24
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Yield(%)
Entry
Change from standard conditions
3a
90
56
0
4a
8
8
0
1
2
3
4
5
6
7
No change
with TEMPO
no CuF2
30
0
0
0
no CsF
70
30
32
41
10
19
12
13
5
no Ni/Ligand
no Ni/Ligand and CsF
no Ni
0
50
0
aReaction conditions: 1a (0.3 mmol), 2a (0.45mmol), Ni(acac)2 (0.03 mmol), 1,10ꢀ
phenanthroline (0.03 mmol), CsF (0.3 mmol), and CuF2 (0.3 mmol) were stirred in
DMSO (1.5 mL) at 120 °C for 12 h.
Based on these results, we propose the reaction pathway as shown in Figure 2. Arylsilane is
activated by CsF (path a)15 and reacts with Ni(II), providing aryl Ni complex A. Alkynyl
carboxylic acid is converted to alkynyl copper complex B by decarboxylation with Cu. The
transmetalation of aryl Ni complex A and alkynyl copper complex B affords aryl alkynyl Ni
complex C. The reductive elimination of C furnishes the desired product and Ni(0). Ni(II) is
regenerated by oxidation.15 This reaction cycle may involve both radical and ionic processes
because the product yield decreased in the presence of TEMPO. Moreover, both Niꢀcatalyzed
path I and Cuꢀmediated path II are involved, because 3a was obtained in 30% yield even
without Ni. CuF2 is the most important reagent for this coupling reaction. In the presence of CsF,
path a dominates and prevents the homocoupling of aryl silane through path c.
ACS Paragon Plus Environment

Page 11 of 24
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 2.Proposed reaction mechanism.
In summary, an aryl silane was successfully adapted as a coupling partner in the decarboxylative
coupling of an alkynyl carboxylic acid in the presence of Ni catalysis for the first time. This
cross coupling reaction can take advantage of both easy handling and low cost of the Ni(II)
source compared to Pd. In the course of our investigation, catalytic activity highly depends on
the ligand; 1,10ꢀphenanthroline showed the best result. As an oxidant and activator, CuF2 seems
to be crucial for the transformation, while both Ni and CsF can suppress the formation of
byproducts. Under the optimal condition, this catalytic system showed excellent functional group
tolerance towards alkyl, alkoxy, halogen, nitro, cyano, ketone, and ester groups. Interestingly, the
reaction withbutꢀ2ꢀynedioic acid and organosilane afforded the corresponding symmetrical
diarylalkynes. Despite of mechanistic studies, the reaction mechanism has ambiguity and can be
suggested both Niꢀcatalyzed and Cuꢀmediated pathways either through radical or ionic processes.
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 12 of 24
1
2
3
4
General Experimental Procedure
5
6
7
8
Nickel-catalyzed decarboxylative coupling of Aryl alkynyl carboxylic acidwith
triethoxyarylsilane:Aryl alkynyl carboxylic acid (2.0 mmol), 1,10ꢀphenanthroline (36 mg,
0.2mmol), Ni(acac)2 (51 mg, 0.2mmol), CuF2 (203 mg, 2.0mmol), triethoxyarylsilane (3.0mmol),
CsF (304 mg, 2.0mmol) and DMSO (10 mL) were added to the reaction vial. The solution was
stirred at 120oC for 12 h. The resulting mixture was cooled and then filtered using a syringe filter.
Then the mass was quenched with saturated ammonium chloride solution. The mixture was
extracted with Et2O (2 × 15mL), and the combined organic layers were dried over sodium sulfate.
The solvent was removed under reduced pressure, and the resulting crude product was purified
by flash chromatography on silica gel (eluent = hexane).
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1,2-Diphenylethyne (3a)3a
3ꢀPhenylpropiolic acid (1a) (292 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721 mg,
3.0mmol) afforded 1,2ꢀdiphenylethyne (3a) (321 mg, 1.8mmol,90 % yield) as white solid,m.p.
13
60 – 62 °C; 1H NMR (500 MHz, CDCl3) δ 7.61 – 7.44 (m, 4H), 7.43 – 7.30 (m, 6H); C{1H}
NMR (126 MHz, CDCl3) δ 131.6, 128.4, 128.3, 123.3, 89.4; MS (EI) m/z: 178 (M+).
1-Methyl-3-(phenylethynyl)benzene (3b) 3a
3ꢀ(mꢀTolyl)propiolic acid (1b) (320 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721 mg,
3.0mmol) afforded 1ꢀmethylꢀ3ꢀ(phenylethynyl)benzene (3b)(300 mg, 1.56mmol, 78 % yield) as
colorless oil; 1H NMR (500 MHz, CDCl3) δ 7.60 – 7.55 (m, 2H), 7.44 – 7.33 (m, 5H), 7.28 (t, J
= 7.6 Hz, 1H), 7.18 (d, J = 7.6 Hz, 1H), 2.39 (s, 3H); 13C{1H} NMR (126 MHz, CDCl3) δ 138.0,
132.2, 131.6, 129.2, 128.7, 128.4, 128.3, 128.2, 123.4, 123.1, 89.6, 89.1, 21.3; MS (EI) m/z: 192
(M+).
ACS Paragon Plus Environment

Page 13 of 24
The Journal of Organic Chemistry
1
2
1,2-Dimethyl-4-(phenylethynyl)benzene (3c)18
3
4
5
6
7
8
3ꢀ(3,4ꢀDimethylphenyl)propiolic acid (1c) (348 mg, 2.0mmol) and triethoxyphenylsilane (2a)
(721 mg, 3.0mmol) afforded 1,2ꢀdimethylꢀ4ꢀ(phenylethynyl)benzene (3c)(326 mg, 1.58mmol,
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
79 % yield) as white solid,m.p.58 – 61 °C; H NMR (400 MHz, CDCl3) δ 7.55 – 7.50 (m, 2H),
7.38 – 7.31 (m, 4H), 7.29 (d, J = 7.8 Hz, 1H), 7.12 (d, J = 7.7 Hz, 1H), 2.28 (s, 3H), 2.27 (s, 3H);
13C{1H} NMR (101 MHz, CDCl3) δ 137.2, 136.7, 132.7, 131.6, 129.7, 129.1, 128.3, 128.0, 123.6,
120.5, 89.7, 88.5, 19.8, 19.6. MS (EI) m/z: 206 (M+).
2,4-Dimethyl-1-(phenylethynyl)benzene (3d)19
3ꢀ(2,4ꢀDimethylphenyl)propiolic acid (1d) (348 mg, 2.0mmol) and triethoxyphenylsilane (2a)
(721 mg, 3.0mmol) afforded 2,4ꢀdimethylꢀ1ꢀ(phenylethynyl)benzene (3d)(293 mg, 1.42mmol,
1
71 % yield) as pale yellow oil; H NMR (500 MHz, CDCl3) δ 7.59 – 7.55 (m, 2H), 7.44 (d, J =
7.8 Hz, 1H), 7.40 – 7.34 (m, 3H), 7.09 (s, 1H), 7.02 (d, J = 7.8 Hz, 1H), 2.53 (s, 3H), 2.37 (s,
3H); 13C{1H} NMR (126 MHz, CDCl3) δ 140.1, 138.4, 131.8, 131.5, 130.4, 128.4, 128.0, 126.5,
123.8, 120.0, 92.7, 88.6, 21.5, 20.7; MS (EI) m/z: 206 (M+).
1-Methoxy-2-(phenylethynyl)benzene (3e)20
3ꢀ(2ꢀMethoxyphenyl)propiolic acid (1e) (352 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721
mg, 3.0mmol) afforded 1ꢀmethoxyꢀ2ꢀ(phenylethynyl)benzene (3e)(300 mg, 1.44mmol, 72 %
yield) as pale yellow oil; 1H NMR (400 MHz, CDCl3) δ 7.55 (m, 2H), 7.49 (dd, J = 7.6, 1.7 Hz,
1H), 7.35 – 7.22 (m, 4H), 6.91 (td, J = 7.5, 1.0 Hz, 1H), 6.86 (d, J = 8.4 Hz, 1H), 3.86 (s, 3H);
13C{1H} NMR (101 MHz, CDCl3) δ 160.0, 133.6, 131.7, 129.9, 128.3, 128.2, 123.6, 120.7, 112.5,
110.8, 93.5, 85.9, 55.9; MS (EI) m/z: 208 (M+).
1-Methoxy-3-(phenylethynyl)benzene (3f)21
3ꢀ(3ꢀMethoxyphenyl)propiolic acid (1f) (352 mg, 2.0mmol) and triethoxyphenylsilane (2a)
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 14 of 24
1
2
3
4
5
6
7
8
9
(721mg, 3.0mmol) afforded 1ꢀmethoxyꢀ3ꢀ(phenylethynyl)benzene (3f)(321 mg, 1.54mmol, 77 %
yield) as pale yellow oil; 1H NMR (500 MHz, CDCl3) δ 7.58 – 7.53 (m, 2H), 7.39 – 7.33 (m, 3H),
7.29 – 7.24 (m, 1H), 7.16 (m, 1H), 7.09 (m, 1H), 6.91 (qd, J = 8.3, 2.6, 1.0 Hz, 1H), 3.84 (s, 3H);
13C{1H} NMR (126 MHz, CDCl3) δ 159.4, 131.6, 129.4, 128.4, 128.3, 124.3, 124.2, 123.2, 116.4,
114.9, 89.3, 89.2, 55.3; MS (EI) m/z: 208 (M+).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
5-(Phenylethynyl)benzo[d][1,3]dioxole (3g)22
3ꢀ(Benzo[d][1,3]dioxolꢀ5ꢀyl)propiolic acid (1g) (380 mg, 2.0mmol) and triethoxyphenylsilane
(2a) (721 mg, 3.0mmol) afforded 5ꢀ(phenylethynyl)benzo[d][1,3]dioxole (3g)(364 mg,
1
1.64mmol, 82 % yield) as white solid,m.p.100 – 102 °C; H NMR (400 MHz, CDCl3) δ 7.53 –
7.47 (m, 2H), 7.37 – 7.30 (m, 3H), 7.07 (dd, J = 8.0, 1.6 Hz, 1H), 6.98 (d, J = 1.6 Hz, 1H), 6.79
(d, J = 8.0 Hz, 1H), 5.99 (s, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ 147.9, 147.5, 131.5, 128.3,
128.1, 126.3, 123.4, 116.5, 111.5, 108.5, 101.3, 89.3, 87.8; MS (EI) m/z: 222 (M+).
1-(Phenylethynyl)naphthalene (3h)22
3ꢀ(Naphthalenꢀ1ꢀyl)propiolic acid (1h) (392 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721
mg, 3.0mmol) afforded 1ꢀ(phenylethynyl)naphthalene (3h)(388 mg, 1.70mmol, 85 % yield) as
1
pale yellow oil; H NMR (400 MHz, CDCl3) δ 8.64 (d, J = 8.5 Hz, 1H), 7.98 – 7.93 (m, 2H),
7.91 (d, J = 7.1 Hz, 1H), 7.81 (m, 2H), 7.73 (m, 1H), 7.64 (m, 1H), 7.55 (m, 1H), 7.50 (m, 3H);
13C{1H} NMR (101 MHz, CDCl3) δ 133.5, 133.4, 131.9, 130.6, 128.9, 128.6, 128.6, 128.5, 126.9,
126.6, 126.4, 125.5, 123.6, 121.1, 94.6, 87.8; MS (EI) m/z: 228 (M+).
2-Methoxy-6-(phenylethynyl)naphthalene (3i)23
3ꢀ(6ꢀMethoxynaphthalenꢀ2ꢀyl)propiolic acid (1i) (452mg, 2.0mmol) and triethoxyphenylsilane
(2a) (721 mg, 3.0mmol) afforded 2ꢀmethoxyꢀ6ꢀ(phenylethynyl)naphthalene (3i)(424mg,
1.64mmol, 82 % yield) as white solid,m.p.167 – 168 °C; 1H NMR (500 MHz, CDCl3) δ 7.98 (m,
ACS Paragon Plus Environment

Page 15 of 24
The Journal of Organic Chemistry
1
2
3
4
1H), 7.71 (t, J = 8.3 Hz, 2H), 7.60 – 7.53 (m, 3H), 7.40 – 7.31 (m, 3H), 7.17 (dd, J = 8.8, 2.5 Hz,
5
6
13
1H), 7.12 (d, J = 2.6 Hz, 1H); C{1H} NMR (126 MHz, CDCl3) δ 158.3, 134.1, 131.6, 131.3,
7
8
9
129.3, 129.0, 128.5, 128.4, 128.1, 126.8, 123.5, 119.4, 118.2, 105.8, 89.9, 89.0, 55.4; MS (EI)
m/z: 258 (M+).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1-Fluoro-4-(phenylethynyl)benzene (3j)24
3ꢀ(4ꢀFluorophenyl)propiolic acid (1j) (328 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721
mg, 3.0mmol) afforded 1ꢀfluoroꢀ4ꢀ(phenylethynyl)benzene (3j)(322 mg, 1.64mmol, 82 % yield)
as an offꢀwhite solid,m.p.109 – 111 °C; 1H NMR (500 MHz, CDCl3) δ 7.55 (m, 4H), 7.39 – 7.36
(m, 3H), 7.07 (m, 2H); 13C{1H} NMR (126 MHz, CDCl3) δ 162.5 (d, J = 250 Hz), 133.5 (d, J =
8.4 Hz), 131.6, 128.4, 128.4, 123.1, 119.4 (d, J = 3.5 Hz), 115.7 (d, J = 22.1 Hz), 89.1, 88.4;19F
NMR (377 MHz, CDCl3) δ ꢀ110.9; MS (EI) m/z: 196 (M+).
1-(Phenylethynyl)-4-(trifluoromethyl)benzene (3k)25
3ꢀ(4ꢀ(Trifluoromethyl)phenyl)propiolic acid (1k) (428 mg, 2.0mmol) and triethoxyphenylsilane
(2a) (721 mg, 3.0mmol) afforded 1ꢀ(phenylethynyl)ꢀ4ꢀ(trifluoromethyl)benzene (3k)(414 mg,
1.68mmol, 84 % yield) as a white solid,m.p.104 –106 °C; 1H NMR (400 MHz, CDCl3) δ 7.65 –
7.57 (m, 4H), 7.57 – 7.52 (m, 2H), 7.38 – 7.33 (m, 3H); C{1H} NMR (101 MHz, CDCl3) δ
13
130.7, 130.7, 128.9 (q, J = 32.7 Hz), 128.2, 127.8, 127.4, 126.9, 126.1, 124.2 (q, J = 3.7 Hz),
121.5, 90.7, 86.9;19F NMR (377 MHz, CDCl3) δ ꢀ62.8; MS (EI) m/z: 246 (M+).
1-Chloro-3-(phenylethynyl)benzene (3l)10b
3ꢀ(3ꢀChlorophenyl)propiolic acid (1l) (361 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721
mg, 3.0mmol) afforded 1ꢀchloroꢀ3ꢀ(phenylethynyl)benzene (3l)(298 mg, 1.40mmol, 70 % yield)
as pale yellow oil; 1H NMR (400 MHz, CDCl3) δ 7.55 – 7.50 (m, 3H), 7.40 (m, 1H), 7.37 – 7.32
13
(m, 3H), 7.32 – 7.23 (m, 2H); C{1H} NMR (101 MHz, CDCl3) δ 134.2, 131.6, 131.4, 129.7,
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 16 of 24
1
2
129.5, 128.6, 128.5, 128.4, 124.9, 122.7, 90.5, 87.9. MS (EI) m/z: 212 (M+).
4-(Phenylethynyl)-1,1'-biphenyl (3m)26
3
4
5
6
7
8
9
3ꢀ([1,1'ꢀBiphenyl]ꢀ4ꢀyl)propiolic acid (1m) (445 mg, 2.0mmol) and triethoxyphenylsilane (2a)
(721 mg, 3.0mmol) afforded 4ꢀ(phenylethynyl)ꢀ1,1'ꢀbiphenyl (3m)(392 mg, 1.54mmol, 77 %
yield) as a white solid,m.p.163 – 165 °C; 1H NMR (400 MHz, CDCl3) δ 7.66 – 7.53 (m, 8H),
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
13
7.47 (t, J = 7.6 Hz, 2H), 7.41 – 7.33 (m, 4H); C{1H} NMR (101 MHz, CDCl3) δ 140.9, 140.3,
132.0, 131.6, 128.7, 128.4, 128.3, 127.6, 127.0, 123.3, 122.2, 90.1, 89.3. MS (EI) m/z: 254 (M+).
1-Nitro-4-(phenylethynyl)benzene (3n)10a
3ꢀ(4ꢀNitrophenyl)propiolic acid (1n) (382 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721 mg,
3.0mmol) afforded 1ꢀnitroꢀ4ꢀ(phenylethynyl)benzene (3n)(254 mg, 1.14mmol, 57 % yield) as
1
light yellow solid,m.p.115 ꢀ 117 °C; H NMR (500 MHz, CDCl3) δ 8.22 (m, 2H), 7.67 (m, 2H),
7.59 – 7.54 (m, 2H), 7.42 – 7.36 (m, 3H); 13C{1H} NMR (126 MHz, CDCl3) δ 146.9, 132.3,
131.8, 130.3, 129.3, 128.5, 123.6, 122.1, 94.7, 87.5; MS (EI) m/z: 223 (M+).
4-(Phenylethynyl)benzonitrile (3o)22
3ꢀ(4ꢀCyanophenyl)propiolic acid (1o) (342 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721
mg, 3.0mmol) afforded 4ꢀ(phenylethynyl)benzonitrile (3o)(268 mg, 1.32mmol, 66 % yield) as
1
light yellow solid,m.p.103 – 105 °C; H NMR (400 MHz, CDCl3) δ 7.67 – 7.58 (m, 4H), 7.58 –
7.50 (m, 2H), 7.41 – 7.35 (m, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 131.0, 131.0, 130.8,
128.1, 127.5, 127.2, 121.2, 117.5, 110.4, 92.7, 86.7; MS (EI) m/z: 203 (M+).
1-(4-(Phenylethynyl)phenyl)ethanone (3p)25
3ꢀ(4ꢀAcetylphenyl)propiolic acid (1p) (376 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721
mg, 3.0mmol) afforded 1ꢀ(4ꢀ(phenylethynyl)phenyl)ethanone (3p)(330 mg, 1.50mmol, 75 %
yield) as light yellow solid,m.p.96 ꢀ 98 °C;1H NMR (500 MHz, CDCl3) δ 7.94 (d, J = 8.6 Hz,
ACS Paragon Plus Environment

Page 17 of 24
The Journal of Organic Chemistry
1
2
13
2H), 7.61 (d, J = 8.6 Hz, 2H), 7.55 (m, 2H), 7.39 – 7.34 (m, 3H), 2.61 (s, 3H); C{1H} NMR
(126 MHz, CDCl3) δ 197.3, 136.2, 131.7, 131.7, 128.8, 128.5, 128.3, 128.2, 122.6, 92.7, 88.6,
26.6; MS (EI) m/z: 220 (M+).
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Methyl 4-(phenylethynyl)benzoate (3q)22
3ꢀ(4ꢀ(Methoxycarbonyl)phenyl)propiolic acid (1q) (408 mg, 2.0mmol) and triethoxyphenylsilane
(2a) (721 mg, 3.0mmol) afforded methyl 4ꢀ(phenylethynyl)benzoate (3q)(326 mg, 1.38mmol,
1
69 % yield) as light yellow solid,m.p.118 – 120 °C; H NMR (400 MHz, CDCl3) δ 8.02 (d, J =
8.5 Hz, 2H), 7.59 (d, J = 8.5 Hz, 2H), 7.55 (m, 2H), 7.39 – 7.34 (m, 3H), 3.93 (s, 3H); C{1H}
13
NMR (101 MHz, CDCl3) δ 166.6, 131.8, 131.5, 129.5, 129.5, 128.8, 128.5, 128.0, 122.7, 92.4,
88.6, 52.3; MS (EI) m/z: 236 (M+).
3-(Phenylethynyl)pyridine (3r)22
3ꢀ(Pyridinꢀ3ꢀyl)propiolic acid (1r) (294 mg, 2.0mmol) and triethoxyphenylsilane (2a) (721 mg,
3.0mmol) afforded 3ꢀ(phenylethynyl)pyridine (3r)(194 mg, 1.08mmol, 54 % yield) as light
1
yellow oil; H NMR (500 MHz, CDCl3) δ 8.73 (dd, J = 2.1, 0.9 Hz, 1H), 8.47 (dd, J = 4.9, 1.7
Hz, 1H), 7.70 (ddd, J = 7.9, 4.9, 1.75 Hz, 1H), 7.49 (m, 2H), 7.30 – 7.25 (m, 3H), 7.15 (ddd, J =
7.9, 4.9, 0.9 Hz, 1H); 13C{1H} NMR (126 MHz, CDCl3) δ 152.2, 148.5, 138.3, 131.7, 128.8,
128.4, 122.9, 122.5, 120.4, 92.7, 86.0; MS (EI) m/z:179 (M+).
1-Methyl-4-(phenylethynyl)benzene (5a)22
3ꢀPhenylpropiolic acid (1a) (292 mg, 2.0mmol) and triethoxy(pꢀtolyl)silane(2b) (763 mg,
3.0mmol) afforded 1ꢀmethylꢀ4ꢀ(phenylethynyl)benzene (5a)(300 mg, 1.56mmol, 78 % yield) as
light yellow solid,m.p.67 ꢀ 69 °C;1H NMR (500 MHz, CDCl3) δ 7.53 (m, 2H), 7.44 (d, J = 8.3
Hz, 2H), 7.37 – 7.31 (m, 3H), 7.16 (d, J = 7.8 Hz, 2H), 2.38 (s, 3H); C{1H} NMR (126 MHz,
13
CDCl3) δ 138.4, 131.5, 131.5, 129.1, 128.3, 128.1, 123.5, 120.2, 89.6, 88.7, 21.5; MS (EI)
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 18 of 24
1
2
m/z:192 (M+).
3
4
5
6
1-(4-(p-Tolylethynyl)phenyl)ethanone (5b)27
7
8
9
3ꢀ(4ꢀAcetylphenyl)propiolic acid (1p) (376 mg, 2.0mmol) and triethoxy(pꢀtolyl)silane (2b) (763
mg, 3.0mmol) afforded 1ꢀ(4ꢀ(pꢀtolylethynyl)phenyl)ethanone (5b)(380 mg, 1.62mmol, 81 %
yield) as light yellow solid,m.p.124 ꢀ 126 °C; 1H NMR (400 MHz, CDCl3) δ 7.91 (d, J = 8.5 Hz,
2H), 7.57 (d, J = 8.4 Hz, 2H), 7.43 (d, J = 8.1 Hz, 2H), 7.16 (d, J = 7.9 Hz, 2H), 2.58 (s, 3H),
2.36 (s, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 197.3, 139.1, 135.9, 131.6, 131.6, 129.2, 128.4,
128.2, 119.5, 93.0, 88.1, 26.6, 21.5; MS (EI) m/z: 234 (M+).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1-Methoxy-4-(phenylethynyl)benzene (5c)22
3ꢀPhenylpropiolic acid (1a) (292 mg, 2.0mmol) and triethoxy(4ꢀmethoxyphenyl)silane(2c) (811
mg, 3.0mmol) afforded 1ꢀmethoxyꢀ4ꢀ(phenylethynyl)benzene (5c)(358 mg, 1.72mmol, 86 %
yield) as light yellow solid,m.p.58 – 60 °C; 1H NMR (500 MHz, CDCl3) δ 7.55 (m, 2H), 7.51 (m,
2H), 7.39 – 7.32 (m, 3H), 6.90 (m, 2H), 3.83 (s, 3H); 13C{1H} NMR (126 MHz, CDCl3) δ 159.6,
133.1, 131.5, 128.4, 127.9, 123.6, 115.4, 114.0, 89.4, 88.1, 55.3; MS (EI) m/z: 208 (M+).
1-Methoxy-4-(p-tolylethynyl)benzene (5d)22
3ꢀ(pꢀTolyl)propiolic acid (1s) (320 mg, 2.0mmol) and triethoxy(4ꢀmethoxyphenyl)silane(2c)
(811 mg, 3.0mmol) afforded 1ꢀmethoxyꢀ4ꢀ(pꢀtolylethynyl)benzene (5d)(329 mg, 1.48mmol,
74 %yield) as light yellow solid,m.p.119 – 121 °C; 1H NMR (400 MHz, CDCl3) δ 7.49 (d, J =
8.9 Hz, 2H), 7.44 (d, J = 8.1 Hz, 2H), 7.17 (d, J = 7.9 Hz, 2H), 6.89 (d, J = 8.9 Hz, 2H), 3.83 (s,
3H), 2.38 (s, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 159.5, 137.9, 132.9, 131.3, 129.1, 120.5,
115.6, 113.9, 88.7, 88.2, 55.2, 21.5; MS (EI) m/z: 222 (M+).
1-Chloro-4-(phenylethynyl)benzene (5e)27
3ꢀPhenylpropiolic acid (1a) (292 mg, 2.0mmol) and (4ꢀchlorophenyl)triethoxysilane(2d) (824mg,
ACS Paragon Plus Environment

Page 19 of 24
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
3.0mmol) afforded 1ꢀchloroꢀ4ꢀ(phenylethynyl)benzene (5e)(383 mg, 1.80mmol, 90 % yield) as
light yellow solid,m.p.78 – 80 °C; 1H NMR (500 MHz, CDCl3) δ 7.64 (m, 2H), 7.54 (m, 2H),
7.45 – 7.41 (m, 3H), 7.41 – 7.37 (m, 2H); 13C{1H} NMR (126 MHz, CDCl3) δ 134.4, 132.9,
131.7, 128.8, 128.6, 128.5, 123.1, 121.9, 90.6, 88.5; MS (EI) m/z: 212 (M+).
2-(Phenylethynyl)thiophene (5f)22
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3ꢀPhenylpropiolic acid (1a) (292 mg, 2.0mmol) and triethoxy(thiophenꢀ2ꢀyl)silane (2e) (691 mg,
3.0mmol) afforded 2ꢀ(phenylethynyl)thiophene (5f)(291 mg, 1.58mmol, 79 % yield) as colorless
oil; 1H NMR (400 MHz, CDCl3) δ 7.5 (m, 2H), 7.38 – 7.32 (m, 3H), 7.29 (m, 2H), 7.02 (m, 1H);
13C{1H} NMR (101 MHz, CDCl3) δ 131.9, 131.4, 128.5, 128.4, 127.3, 127.1, 123.3, 122.9, 93.0,
82.6; MS (EI) m/z: 184 (M+).
Symmetrical Diarlalkynes from Silanes
Nickel-catalyzed
decarboxylative
coupling
of
But-2-ynedioic
acid(6b)with
triethoxyarylsilane: Butꢀ2ꢀynedioic acid (6b)(228 mg, 2.0mmol), 1,10ꢀphenanthroline (72 mg,
0.4mmol), Ni(acac)2 (103 mg, 0.4mmol), CuF2 (406 mg, 4.0mmol), triethoxyarylsilane
(6.0mmol), CsF (608 mg, 4.0mmol) and DMSO (10 mL) were added to the reaction vial, The
solution was stirred at 120oC for 12 h. The resulting mixture was cooled and then filtered using a
syringe filter. Then the mass was quenched with saturated ammonium chloride solution. The
mixture was extracted with Et2O (2 × 15mL), and the combined organic layers were dried over
sodium sulfate. The solvent was removed under reduced pressure, and the resulting crude
product was purified by flash chromatography on silica gel (eluent = hexane).
1,2-Di-p-tolylethyne (7b)10b
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 20 of 24
1
2
3
4
5
6
7
8
9
Butꢀ2ꢀynedioic acid (6b)(228 mg, 2.0mmol) and triethoxy(pꢀtolyl)silane(2a) (1526 mg,
6.0mmol) afforded 1,2ꢀdiꢀpꢀtolylethyne (7b)(157 mg, 0.76mmol, 38 % yield) as white
solid,m.p.139 – 141 °C; 1H NMR (400 MHz, CDCl3) δ 7.43 (d, J = 8.1 Hz, 4H), 7.16 (d, J = 7.9
Hz, 4H), 2.38 (s, 6H); 13C{1H} NMR (101 MHz, CDCl3) δ 138.2, 131.5, 129.1, 120.4, 88.9,
21.5; MS (EI) m/z: 206 (M+).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1,2-Bis(4-chlorophenyl)ethyne (7c)28
Butꢀ2ꢀynedioic acid (6b) (228 mg, 2.0mmol) and (4ꢀchlorophenyl)triethoxysilane(2a) (1649 mg,
6.0mmol) afforded 1,2ꢀbis(4ꢀchlorophenyl)ethyne (7c)(222 mg, 0.9mmol, 45 % yield) as white
solid,m.p.170 – 172 °C; 1H NMR (400 MHz, CDCl3) δ 7.45 (d, J = 8.6 Hz, 4H), 7.33 (d, J = 8.7
Hz, 4H); 13C{1H} NMR (101 MHz, CDCl3) δ 134.5, 132.8, 128.7, 121.4, 89.2; MS (EI) m/z: 246
(M+).
Author Information
Corresponding Author
Eꢀmail : jiminkim@chonnam.ac.kr(J. Kim); sunwoo@chonnam.ac.kr (S. Lee).
Notes
The authors declare no competing financial interest.
Acknowledgements
This research was supported by the National Research Foundation of Korea (NRF) grant funded
by the Korea government (NRFꢀ2015R1A4A1041036, NRFꢀ2014R1A2A1A11050018, NRFꢀ
2012M3A7B4049655). The spectral data were obtained from the Korea Basic Science Institute,
ACS Paragon Plus Environment

Page 21 of 24
The Journal of Organic Chemistry
1
2
3
4
Gwangju branch.
5
6
7
8
9
Supporting Information
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The Supporting Information is available free of charge on the ACS Publications website at DOI:
1
The screening data of nickel source and solvent. Copies of H and 13C{1H} NMR spectra of
products.
REFERENCES
(1) (a) Chen, F.; Wang, T.; Jiao, N.Chem. Rev. 2014, 114, 8613−8661. (b) Gosmini,C.; Be´gouin,
J. M.; Moncomble, A. Chem. Commun.2008, 3221–3233. (c) Sherry, B. D.; Fürstner, A. Acc.
Chem. Res. 2008,41,1500–1511.
(2) (a) Weires, N. A.; Baker, E. L.; Garg, N. K. Nat. Chem.2016, 8, 75–79. (b) Ackerman, L. K.
G.; Lovell, M. M.; Weix, D. J. Nature 2015, 524, 454–457. (c) Borzenko, A.; Loria, N. L. R.;
MacQueen, P. M.; Lavoie, C. M.; McDonald, R.; Stradiotto, M. Angew. Chem. Int. Ed. 2015, 54,
3773–3777. (d) Green, R. A.; Hartwig, J. F. Angew. Chem. Int. Ed. 2015, 54, 3768–3772. (e)
Kim, H.; Lee,C. Org. Lett. 2011, 13, 2050–2053.
(3) (a) Gallop, C. W. D.; Chen, M. T.; Navarro, O. Org. Lett. 2014, 16, 3724–3727. (b) Severin,
R., Reimer, J.; Doye, S. J. Org. Chem. 2010, 75, 3518–3521
(4) (a) Schilz, M.; Plenio, H. J. Org. Chem. 2012, 77, 2798–2807. (b) Magano, J.; Dunetz, J.ꢀR.
Chem. Rev. 2011, 111, 2177–2250. (c) Chinchilla, R.; Nájera, C. Chem. Soc. Rev. 2011, 40,
5084–5121.
(5) Moon, J.; Jeong, M.; Nam, H.; Ju, J.; Moon, J. H.; Jung, H. M.; Lee,S. Org. Lett. 2008, 10,
945–948.
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 22 of 24
1
2
3
4
5
6
7
8
9
(6) (a) Rong, G.; Mao, J.; Yan, H.; Zheng, Y.; Zhang, G. J. Org. Chem. 2015, 80, 7652–7657. (b)
Lv, W. X.; Zeng, Y. F.; Zhang, S. S.; Li, Q.; Wang, H. Org. Lett. 2015, 17, 2972–2975. (c)
Park, K.; Lee, S. RSC Adv. 2013, 3, 14165–14182. (d) Kim, H.; Lee, P. H. Adv. Synth. Catal.
2009, 351, 2827−2832. (e) Li, X.; Yang, F.; Wu, Y. RSC Adv. 2014, 4, 13738−13741. (f) Li, S.;
Li, X.; Yang, F.; Wu, F. Org. Chem. Front. 2015, 2, 1076–1079.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(7) (a) Singh, R.; Allam, B. K.; Singh, N.; Kumari, K.; Singh, S. K.; Singh, K. N. Org. Lett.
2015, 17, 2656–2659. (b) Li, X.; Yang, F.; Wu, Y.; Wu, Y. Org. Lett. 2014, 16, 992–995.
(8). Choe, J.; Yang, J.; Park, K.; Palani, T.; Lee, S. Tetrahedron Lett. 2012, 53, 6908–6912.
(9) (a) Sardzinski, L. W.; Wertjes, W. C.; Schnaith, A. M.; Kalyani, D. Org. Lett. 2015, 17, 1256–
1259. (b) Yang, K.; Wang, P.; Zhang, C.; Kadi, A. A.; Fun, H.ꢀK.; Zhang, Y.; Lu, H. Eur. J. Org.
Chem. 2014, 7586–7589.
(10) (a) Li, X.; Yang, F.; Wu, Y. J. Org. Chem.2013, 78, 4543–4550. (b) Park, K.; Bae, G.; Moon,
J.; Choe, J.; Song, K. H.; Lee, S. J. Org. Chem. 2010, 75, 6244–6251.
(11) (a) Kim, Y.; Park, A.; Park, K.; Lee, S. Tetrahedron Lett. 2011, 52, 1766–1769. (b) Li, Y.ꢀN.;
Wang, J.ꢀL.; He, L.ꢀN. Tetrahedron Lett. 2011, 52, 3485–3488.
(12) (a) Feng, C.; Loh, T.ꢀP. Chem. Commun. 2010, 46, 4779–4781. (b) Yu, C.ꢀM.; Kweon, J. H.;
Ho, P.ꢀS.; Kang, S.ꢀC.; Lee, G. Y. Synlett 2005, 17, 2631–2634.
(13) (a) Denmark, S. E.; Ober, M. H. Aldrichimica Acta2003, 36, 75–85. (b) Denmark, S. E.;
Sweis, R. F. Acc. Chem. Res. 2002, 35, 835–846.
(14) (a) Sore, H. F.; Galloway, W. R. J. D.; Spring, D. R. Chem. Soc. Rev. 2012, 41, 1845–1866.
(b) Nakao, Y.; Hiyama, T. Chem. Soc. Rev. 2011, 40, 4893–4901. (c) Kim, J.; Ok, J.; Kim, S.;
Choi, W.; Lee, P. H. Org. Lett. 2014, 16, 4602−4605.
(15) Hachiya, H.; Hirano, K.; Satoh, T.; Miura, M. Angew. Chem. Int. Ed. 2010, 49, 2202–2205.
ACS Paragon Plus Environment

Page 23 of 24
The Journal of Organic Chemistry
1
2
3
4
5
6
(16) (a) Tang, J.; Guo, C. J. Chem. Res. 2014, 38, 123–127. (b) Ye,Z.; Liu, M.; Lin, B.; Wu, H.;
Ding, J.; Cheng, J. Tetrahedron Lett. 2009, 50,530–532.
7
8
9
(17) We prepared aryl propiolic acids according to known methods. (a) Park, K.; You, J.ꢀM.;
Jeon, S.; Lee, S. Eur. J. Org. Chem. 2013, 1973–1978. (b) Park, K.; Palani, T.; Pyo, A.; Lee,S.
Teterahedron Lett. 2012, 53, 733–737. In addition, we developed the modified method which
does not require column chromatography purification step. (c) Lim, J.; Choi, J.; Kim, H.ꢀS.;
Kim, I. S.; Nam, K. C.; Kim, J.; Lee, S. J. Org. Chem. 2016, 81, 303–308.
(18) Xie, C.; Liu, L.; Zhang, Y.; Xu, P. Org. Lett. 2008, 10, 2393–2396.
(19) Fabrizi, G.; Goggiamani, A.; Sferrazza, A.; Cacchi, S. Angew. Chem. Int. Ed. 2010, 49,
4067–4070.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(20) Gay, R. M.; Manarin, F.; Schneider, C. C.; Barancelli, D. A.; Costa, M. D.; Zeni,G. J. Org.
Chem. 2010, 75, 5701–5706.
(21) Buchwald, S. L.; Anderson, K. W. PCT Int. Appl. 2006, WO 2006074315 A2.
(22) Hu, H.; Yang, F.; Wu, Y. J. Org. Chem. 2013, 78, 10506–10511.
(23) Gising, J.; Nilsson, M. T.; Odell, L. R.; Yahiaoui, S.; Lindh, M.; Iyer, H.; Sinha, A. M.;
Srinivasa, B. R.; Larhed, M.; Mowbray, S. L.; Karlén,A. J. Med. Chem. 2012, 55, 2894–2898.
(24) Wang, L.; Li, P. Synth. Commun. 2003, 33, 3679–3685.
(25) Ohtaka, A.; Teratani, T.; Fujii, R.; Ikeshita, K.; Kawashima, T.; Tatsumi, K.; Shimomura, O.;
Nomura, R. J. Org. Chem. 2011, 76, 4052–4060.
(26) Chow, H.ꢀF.; Wan, C.ꢀW.; Low, K.ꢀH.; Yeung, Y.ꢀY. J. Org. Chem. 2001, 66, 1910–1913.
(27) Gholap, A. R.; Venkatesan, K.; Pasricha, R.; Daniel, T.; Lahoti, R. J.; Srinivasan, K. V. J.
Org. Chem. 2005, 70, 4869–4872.
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 24 of 24
1
2
3
4
(28) Mio, M. J.; Kopel, L. C.; Braun, J. B.; Gadzikwa, T. L.; Hull, K. L.; Brisbois, R. G.;
5
6
Markworth, C. J.; Grieco, P. A. Org. Lett.2002, 4, 3199–3202.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment