Highly efficient synthesis of 1,2-disubstituted acetylenes derivatives from the cross-coupling reactions of 1-bromoalkynes with organotitanium reagents

Article abstract of DOI:10.1016/j.tet.2021.132370

A Highly efficient route for the synthesis of 1,2-disubstituted acetylene derivatives has been developed by nickel catalyzed cross-couplings of alkynyl halides with aryl titanium reagents under mild conditions. This has given corresponding cross-coupling products good to excellent isolated yields of up to 92 %. The aryls bearing electron-donating or electron-withdrawing groups in either alkynylhalides or aryltitanium substrates gave cross-coupling products good yields. This process was simple and easily performed, which provides an efficient method for the synthesis of 1,2-disubstituted acetylenes derivatives.

Full text of DOI:10.1016/j.tet.2021.132370

Tetrahedron 96 (2021) 132370
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Highly efficient synthesis of 1,2-disubstituted acetylenes derivatives
from the cross-coupling reactions of 1-bromoalkynes with
organotitanium reagents
,
b
,
, b, c, *
Chuan Wu a c, Qing-Han Li a
a College of Chemistry and Environment, Southwest Minzu University, Chengdu, 610041, PR China
b Key Laboratory of General Chemistry of the National Ethnic Affairs Commission, College of Chemistry and Environment, Southwest Minzu University,
Chengdu, 610041, PR China
c Key Laboratory of pollution Control Chemistry and Environmental Functional materials for Qinghai-Tibet Plateau of the National Ethnic Affairs
Commission, College of Chemistry and Environment, Southwest Minzu University, Chengdu, 610041, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A Highly efficient route for the synthesis of 1,2-disubstituted acetylene derivatives has been developed
by nickel catalyzed cross-couplings of alkynyl halides with aryl titanium reagents under mild conditions.
This has given corresponding cross-coupling products good to excellent isolated yields of up to 92 %. The
aryls bearing electron-donating or electron-withdrawing groups in either alkynylhalides or aryltitanium
substrates gave cross-coupling products good yields. This process was simple and easily performed,
which provides an efficient method for the synthesis of 1,2-disubstituted acetylenes derivatives.
© 2021 Published by Elsevier Ltd.
Received 27 May 2021
Received in revised form
5 July 2021
Accepted 27 July 2021
Available online 2 August 2021
Keywords:
Nickel
Cross-coupling
Aryltitanium reagents
Alkynylhalides
Acetylenes derivatives
1. Introduction
coupling of Grignard reagents or organoalane with alkynyl bro-
mides [7], transition metal (such as Pd, Ni and Cu) catalyzed cross-
The 1,2-disubstituted acetylenic products are important syn-
thetic units in the preparation of potential bioactive compounds
[1], new materials [2], and natural products as well [3]. The syn-
thetic methods of 1,2-disubstituted acetylenic compounds have
been widely concerned by chemists. Since the discovery of Sono-
gashira coupling reaction in 1970s [4], this coupling reaction has
become one of the most effective methods to synthesize the 1,2-
disubstituted acetylenic compounds [5]. Concerning the impor-
tance of this reaction, researchers have directed their efforts to-
wards the development of more efficient or single metal catalyst
systems, milder reaction conditions, and other such objectives
during the past decades [6]. Among these methods, the typical
synthetic protocols for 1,2-disubstituted acetylenic compounds
include transition metal (such as Ni, Cu, Pd) catalyzed cross-
coupling reactions of electrophiles with alkynylmetallic reagents
[8]. Although, these efforts have provided alternative methods for
the synthesis of 1,2-disubstituted acetylenic compounds, these
reactions still suffer from excess bases, co-catalysts, high temper-
ature, relatively long reaction time, or the special reaction medium.
The development of more efficient and atom economical ap-
proaches for the synthesis of 1,2-disubstituted acetylenic com-
pounds remains as desirable work. Aryl halides, especially aryl
iodides and bromides, and alkynes are the preferred coupling
partners in these reactions. Particularly, 1-bromoalkynes, which is
easily synthesized from terminal alkynes, has been widely applied
in cross-coupling reactions [9]. In addition to the above reagents,
organotitanium reagents have been extensively used as nucleo-
philes for organic reactions [10].
Previous studies show that organotitanium reagents are a highly
efficient nucleophiles for cross-coupling reactions with aromatic
halides or benzylic halides [10e,g,i,k,l]. While, the synthesis based
on direct coupling of alkynyl halide with organotitanium reagents
using nickel as catalyst is developed rarely. To continue our efforts
* Corresponding author. College of Chemistry and Environment, Southwest
Minzu University, Chengdu, 610041, PR China.
E-mail addresses: lqhchem@163.com, lqhchem@swun.edu.cn (Q.-H. Li).
https://doi.org/10.1016/j.tet.2021.132370
0040-4020/© 2021 Published by Elsevier Ltd.

C. Wu and Q.-H. Li
Tetrahedron 96 (2021) 132370
a
Table 1
in developing coupling reactions using reactive organometallic
reagents [7c,11], and develop a more efficient and convenient
procedures for the preparation of 1,2-disubstituted acetylenes
compounds, herein, we wish to report a new method for the syn-
thesis of 1,2-disubstituted acetylenes compounds via nickel-
catalyzed cross-couplings between 1-bromoalkynes and organo-
titanium reagents in the presence of NiCl2(PPh3)2 (5 mol%)/DPPE
(15 mol%) and DIPEA as base at 60 ꢀC for 15e30 min. Notably, nickel
is used as the single catalyst to give 1,2-disubstituted acetylenes
compounds in good to excellent isolated yields in this procedure
(Scheme 1).
Effect of the nickel salt, base and ligand on the cross-coupling reaction.
.
Entry
Cat.
Base (1.5 equiv)
Ligand
Yield 3aa (%)b
1
2
3
4
5
6
7
8
Ni(acac)2
e
DPPE
DPPE
DPPE
DPPE
PCy3
32
27
28
38
16
15
21
23
41
32
41
38
49
2. Results and discussion
NiI2(PPh3)2
Ni(dppf)Cl2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
e
e
e
In our initial research, we performed the reaction between 1-(2-
bromoethynyl)-4-methylbenzene
e
(p-MeC6H4C^CBr)(1a,
e
TFP
0.5 mmol) with triisopropoxy(phenyl)titanium (PhTi(OiPr)3) (2a,
0.8 mmol) in the presence of Ni(acac)2 (5 mol%) and 10 mol% DPPE
in THF at 60 ꢀC for 0.5 h. To our delight, 32 % isolated yield of the
desired 1-methyl-4-(2-phenylethynyl)-benzene(3aa) was obtained
(Table 1, entry 1). Then, different nickel salts were examined
(Table 1, entries 2e4). Notably, NiCl2(PPh3)2 gave the best result
among the tested nickel salts (Table 1, entry 4). To further under-
stand the nature of this catalysis, we tested the reaction of 1a with
2a under various conditions and the results are listed in Tables 1
and 2. The effect of various ligands in the generation of 3aa using
NiCl2(PPh3)2 as catalyst is shown in Table 1 (Table 1, entries 5e8). It
was found that the DPPE ligand was the best effective for the
reactivity (38 % isolated yield, Table 1, entry 4). The other phosphine
ligands did not provide satisfactory results (Table 1, entries 5e8). In
the same conditions, bases were subsequently surveyed. The iso-
lated yield of coupling product 3aa was up to 49 % when using
e
DPPB
Xantphos
DPPE
DPPE
DPPE
DPPE
DPPE
e
9
K2CO3
K3PO4
Et3N
tBuOK
DIPEA
10
11
12
13
a
1a/2a/Cat/Ligand ¼ 0.5/0.8/0.025/0.05 mmoL, THF 3 mL.
b
Isolated yield.
Table 2
Efffect of the solvent, reaction temperature and the molar ratio of NiCl2(PPh3)2/DPPE
on the cross-coupling reaction.a
t
DIPEA as base. Other bases such as K2CO3, K3PO4, Et3N and BuOK
were less effective than DIPEA (Table 1, entries 9e12).
A brief examination of the influence of solvent on the isolated
yield of the coupling product 3aa revealed that THF was the solvent
of choice. In toluene, hexane, or DMF, the isolated yield of the
coupling product 3aa was very low (Table 2, entries 1e3). Further
studies indicated that the catalyst loading dramatically influenced
the isolated yield of the coupling product 3aa. When the
NiCl2(PPh3)2 loading increases from 5 mol% to 8 mol%, the isolated
yield of the coupling product 3aa is basically unchanged (Table 1,
entry 13, Table 2, entry 5). In contrast, reducing the NiCl2(PPh3)2
loading to 2.5 mol% decreased the isolated yield of the coupling
product 3aa to 35 % (Table 2, entry 4).
The molar ratio of metal and ligand was examined. When the
mol ratio of NiCl2(PPh3)2 and DPPE was altered to 1:1, the isolated
yield of the coupling product 3aa decreased to 32 % (Table 2, entry
6). While the moral ratio of NiCl2(PPh3)2 and DPPE was altered to
1:3, the isolated yield of the coupling product 3aa increased to 54 %
(Table 2, entry 7). When the PhTi(OiPr)3 (2a) loading increases from
0.8 mmol to 1.0 mmol, the isolated yield of the coupling product
3aa was increased (Table 2, entries 7, 9). In contrast, reducing the
PhTi(OiPr)3 (2a) loading to 0.6 mmol decreased the isolated yield of
the coupling product 3aa to 29 % (Table 2, entries 7, 8). It is worth
noting that the isolated yield of the desired coupling product 3aa is
Entry
2a(mmol)
Solvent
Time (h)
Yield 3aa(%)b
1
2
3
4
5
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.6
1.0
1.0
1.0
1.0
1.0
1.0
toluene
hexane
DMF
THF
THF
THF
THF
THF
THF
THF
10
10
10
10
10
10
10
10
10
5
15
11
trace
35
48
32
54
29
57
57
56
56
50
55
c
d
e
6
7
f
8
9
10
11
12
13
14g
THF
THF
THF
THF
1
0.5
0.25
0.5
a
1a/2a/NiCl2(PPh3)2/DPPE ¼ 0.5/0.8/0.025/0.05 mmol, 60 ꢀC.
b
c
d
e
f
Isolated.
1a/2a/NiCl2(PPh3)2/DPPE ¼ 0.5/0.8/0.0125/0.025 mmol, 60 ꢀC.
1a/2a/NiCl2(PPh3)2/DPPE ¼ 0.5/0.8/0.04/0.08 mmol, 60 ꢀC.
NiCl2(PPh3)2/DPPE ¼ 1/1.
NiCl2(PPh3)2/DPPE ¼ 1/3.
g
80 ꢀC.
basically unchanged when the reaction time is shortened from 10 h
to 0.5 h (Table 2, entries 9e12). However, the isolated yield of the
coupling product 3aa were decreased when the reaction time is
shortened from 0.5h to 0.25 h (Table 2, entries 12, 13). Furthermore,
the isolated yield of the coupling product 3aa is basically un-
changed when the reaction temperature increased from 60 ꢀC to
Scheme 1. Nickel-catalyzed cross-coupling reactions of 1-bromoalkyne derivatives
with organotitanium nucleophiles.
2

C. Wu and Q.-H. Li
Tetrahedron 96 (2021) 132370
80 ꢀC (Table 2, entries 12,14). Extensive screening showed that the
optimized coupling conditions were 5 mol% NiCl2(PPh3)2/15 mol%
DPPE, 0.5 mmol 1a, 1.0 mmol 2a in THF at 60 ꢀC for 0.5 h (Table 2,
entry 12).
Table 4
NiCl2(PPh3)2/DPPE-catalyzed cross-coupling reaction of 1-bromoalkynes(1) with
organotitanium reagents(2).a
With the optimized conditions in hand, the scope of this reac-
tion was studied by using various 1-bromoalkynes (1). The triiso-
propoxy(phenyl)titanium (PhTi(OiPr)3) (2a) reacted smoothly with
a series of 1-bromoalkynes 1(aeo) at 60 ꢀC for 15e30 min to give
the corresponding coupling products 3(aaeoa) in moderate to
excellent isolated yields (Table 3, entries 1e15). As listed in Table 3,
the reaction was not significantly affected by the substituents on
the aromatic ring of the 1-bromoalkynes. Both electron-rich
(Table 3, entries 1, 3e6) and electron-deficient substituents
(Table 3, entries 7e13) were tolerated. Notably, methyl, ethyl, butyl,
tbutyl, alkoxyl, bromo, chloro, fluoro and trifluoromethyl groups
posed no challenges under the described reaction conditions.
Especially, a series of coupling products 1,2-disubstituted acety-
lenes (3) with fluoro and trifluoromethyl on aryl rings of 1-
bromoalkynes were synthesized in excellent isolated yields
(Table 4, entries 9e11, 13, 86e92 % yields). Furthermore, even with
sterically hindered 2-(2-bromoethynyl)naphthalene (1o) (Table 3,
entry 15), the coupling reaction underwent smoothly to give good
isolated yield of the coupling product 3oa (Table 3, entry 15, 82 %
yield). Importantly, the reaction also worked well with the 2-(2-
bromoethynyl)thiophene (1n) and gave moderate isolated yield
of the coupling product 3na (Table 3, entry 14, 48 % yield). To our
delight, 4-(bromoethynyl)benzoate can react with phenyltitanium
to obtain isopropoxy 4-(phenylethynyl)benzoate (4pa) with 61 %
isolated yield, this may be formed by the formation of 4-
phenylethynylbenzoate and then exchange with isopropoxy
group in the reaction system(Table 3, entry 16). In contrast, under
the same conditions, 2-(bromoethynyl)pyridine cannot be coupled
with phenyltitanium, this may be due to the coordination between
Entry
1 R1
2 R
Prod. 3
Yield 3(%)b
1
2
3
4
5
6
7
8
9
1a 4-CH3Ph
1b Ph
1c 3-CH3Ph
1d 4-EtPh
1e 4-butylPh
1f 4-tbutylPh
1g 4-ClPh
1h 4-BrPh
1i 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2b 4-FPh
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
2c 4-CH3Ph
3 ab
3bb
3 cb
3 db
3eb
3 fb
3gb
3 hb
3ib
82
80
86
75
83
86
86
81
82
89
87
82
92
59
77
58
58
45
68
66
60
65
62
73
65
60
70
78
41
68
c
c
c
c
10
11
12
13
1j 3-FPh
1k 2-FPh
3jb
3 kb
3lb
c
c
1l 3,5-F2Ph
1m 4-CF3Ph
1n 2-thienyl
1o 2-Naphthalenyl
1a 4-CH3Ph
1b Ph
1c 3-CH3Ph
1d 4-EtPh
1e 4-butylPh
1f 4-tbutylPh
1g 4-ClPh
c
3mc
3 nb
3ob
3ac
3bc
3cc
3dc
3ec
3fc
3gc
3hc
3ic
3jc
3kc
3lc
14
15
16
c
c
17
18
19
20
21
22
23
24
25
c
c
1h 4-BrPh
1i 4-FPh
1j 3-FPh
c
c
c
26
27
28
1k 2-FPh
c
1l 3,5-F2Ph
1m 4-CF3Ph
1n 2-thienyl
1o 2-Naphthalenyl
c
3mc
3nc
3oc
29
30
c
Table 3
a
1/2/NiCl2(PPh3)2/DPPE
¼
0.5/1.0/0.025/0.075 mmoL, 15e30 min, 1.5 equiv
NiCl2(PPh3)2/DPPE-catalyzed cross-coupling reaction of triisopropoxy(phenyl)tita-
DIEPA.
nium (PhTi(OiPr)3) (2a) with various 1-bromoalkynes(1).a
b
Isolated yield.
15 min.
c
nitrogen and titanium(Table 3, entry 17).
We subsequently investigated cross-coupling reactions of
substituted aryltitanium reagents with various 1-bromoalkynes
using 5 mol% NiCl2(PPh3)2 and 15 mol% DPPE conducting in THF
at 60 ꢀC for 15e30 min, and results are summarized in Table 4. A
series of coupling products 1,2-disubstituted acetylenes (3) with
electron-withdrawing or electron-donating groups such as methyl,
ethyl, fluoro, chloro, bromo and trifluoromethyl on aryl rings of 1-
bromoalkynes were synthesized in moderate to good isolated
yields (Table 4, entries 1, 3e13, 16, 18e28). The triisopropoxy(4-
Entry
1
R1
Prod.3
Yield 3 (%)b
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1q
4-CH3Ph
Ph
3-CH3Ph
4-EtPh
4-butylPh
4-tbutylPh
4-ClPh
4-BrPh
4-FPh
3-FPh
2-FPh
3,5-F2Ph
4-CF3Ph
2-thienyl
2-Naphthalenyl
4-CH3OOCPh
2-pyridyl
3aa
3ba
3ca
3da
3ea
3fa
3ga
3ha
3ia
3ja
3ka
3la
3ma
3na
3oa
3pa
3qa
56
57
51
60
71
68
78
68
91
91
92
88
86
48
82
methylphenyl)titanium
(4-CH3C6H4Ti(OiPr)3)
(2c)
reacted
smoothly with various 1-bromoalkynes (1a-1o) at 60 ꢀC for
15e30 min to give the corresponding coupling product 3(ac-oc) in
41e78 % isolated yields (Table 4, entry 16e30). The corresponding
coupling product 3(ab-ob) can be obtained by the reaction of trii-
sopropoxy(4-fluorophenyl)titanium (4-FC6H4Ti(OiPr)3) (2b) with
1-bromoalkyne (1a-1o) at 60 ꢀC for 15e30 min in 59e92 % isolated
yield (Table 4, entries 1e15). The reaction rate of 1-bromoalkynes
with electron withdrawing group (Table 4, entries 7e13, 22e28)
is faster than that of 1-bromoalkynes with electron donating
groups (Table 4, entries 1, 3e6, 16, 18e21). This may be due to the
fact that the oxidative addition reaction of alkyne bromide with
electron withdrawing group and palladium is easier than that of
alkyne bromide with electron donating group. The isolated yield of
c
7
8 c
9 c
c
10
11
12
13
c
c
c
14
15
c
16
17
0(61)d
NR
a
1/2a/NiCl2(PPh3)2/DPPE ¼ 0.5/1.0/0.025/0.075 mmoL, 1.5 equiv DIEPA.
b
c
Isolated yield of 3.
15 min.
d
isopropoxy 4-(phenylethynyl)benzoate (4pa).
3

C. Wu and Q.-H. Li
Tetrahedron 96 (2021) 132370
the coupling product 3 cc was only 45 % when 1-(2-bromoethynyl)-
3-methylbenzene (m-CH3C6H4C^CBr) (1c) reacted with triisopro-
poxy(4-methylphenyl)titanium (4-CH3C6H4Ti(OiPr)3) (2c) at 60 ꢀC
for 30 min. This may be due to the steric hindrance and electron
donating effect of 3-methyl, which makes the oxidative addition of
3-methyl phenylethynyl bromide to palladium difficult. Impor-
tantly, when 2-(bromoethynyl)thiophene (2-thienylC≡CBr) (1n)
was reacted with triisopropoxy(4-fluorophenyl)titanium (4-
FC6H4Ti(OiPr)3) (2b) at 60 ꢀC for 30 min, the corresponding
coupling product 3 nb was obtained in 59 % isolated yield (Table 4,
entry 14). Under the same conditions, 2-(bromoalkynyl)naphtha-
lene (1o) was coupled with triisopropoxy(4-fluorophenyl)tita-
nium(4-FC6H4 Ti(OiPr)3) (2b) for 15 min, the corresponding
coupling product 3ob was obtained in 77 % isolated yield (Table 4,
entry 15). Furthermore, the coupling product 3oc could be obtained
in 68 % isolated yield when coupling of 2-(bromoethynyl)naph-
thalene (1o) with triisopropoxy(4-methylphenyl)titanium (4-
CH3C6H4 Ti(OiPr)3) (2c) (Table 4, entry 30). While, the isolated
yield of the coupling product 3nc was only 41 % when 2-(bro-
moethynyl)thiophene (2-thienylC≡CBr) (1n) reacted with triiso-
propoxy(4-methylphenyl)titanium (4-CH3C6H4 Ti(OiPr)3) (2c) at
60 ꢀC for 30 min (Table 4, entry 29), this may be due to the coor-
dination of sulfur atoms of thiophene with organotitanium
reagents.
layer chromatography (TLC) was performed on silica 60F-254
plates. Flash column chromatography was carried out on silica gel
(300e400 mesh). All reactions were carried out under nitrogen
atmosphere. Chemical reagents and solvents were purchased from
Damas-beta and Aldrich, and were used without further purifica-
tion with the exception of these reagents: THF, Et2O, Hexane and
Toluene were distilled from Sodium under Nitrogen. Purification of
the coupling products was carried out by flash chromatography. All
synthesis and manipulations were carried out under a dry nitrogen
atmosphere. Organotitanium compounds of RTi(OiPr)3(R ¼ Ph (2a),
4-MeC6H4 (2b), or 4-CF3C6H4(2c)) were prepared according to
literature procedures [10d]. Compounds of 1-bromoalkynes 1a-1q
were prepared according to literature procedures [7c,11c].
4.2. General Procedures for the coupling reaction of
alkynylbromides with organotitaniums reagents
Under a dry nitrogen atmosphere, a mixture of NiCl2(PPh3)2
(16.35 mg, 0.025 mmol) and DPPE (29.88 mg, 0.075 mmol) in a
reaction vessel was added an aryltitanium compound (1.0 mmol) in
2 mL THF followed by an addition of alkynylbromides (0.50 mmol).
The resulted solution was stirred at 60 ꢀC for 15e30 min. After
completion the reaction, the mixture was diluted with saturated
ammonium chloride solution (5 mL) and extracted with ethyl ac-
etate (3 ꢁ 15 mL). The combined organic layers were dried over
anhydrous Na2SO4, filtered and evaporated in vacuum. The residue
was subjected to flash column chromatography on silica gel (hex-
ane or ethyl acetate and hexane) to afford the corresponding 1, 2-
disubstituted acetylenes 3.
The reaction was found to be effective in gram-scale synthesis,
which indicated its potential for practical application (Scheme 2).
1,2-bis(4-fluorophenyl)ethyne (3ib) was synthesized in 1.24 g using
this methodology.
1-methyl-4-(phenylethynyl)benzene(3aa) [7c]:Yield: 0.054g
3. Conclusions
(56 %), white solid, m.p. 70e71 ꢀC. 1H NMR (400 MHz,CDCl3)
d
7.53e7.50 (m, 2H), 7.42 (d, J ¼ 8.4 Hz, 2H), 7.35e7.28 (m, 3H), 7.14
We have developed an improved procedure for the nickel-
catalyzed cross-couplings of alkynyl halides with aryl titanium re-
agents under mild conditions and demonstrated that this meth-
odology is a simple and efficient method for the preparation of 1,2-
disubstituted acetylenes. In the presence of NiCl2(PPh3)2 (5 mol
%)/15 mol% DPPE, 1-bromoalkynes reacts smoothly with aryltita-
ninum reagents in THF at 60 ꢀC for 15e30 min to generate the
corresponding cross-coupling products 1,2-disubstituted acety-
lenes in moderate to excellent isolated yields of up to 92 %. This
cross-coupling reaction is compatible with a wide range of func-
tional groups. Moreover, the ready availability of the starting ma-
terials, the mild reaction conditions, and the simplicity of the
operations involved are additional features making the methodol-
ogy could therefore serve as a complementary option in the field of
1,2-disubstituted acetylenes. Notably, no other co-catalysts are
necessary in the present procedure. Further application of these
1,2-disubstituted acetylenes in organic synthesis is in progress.
(d, J ¼ 8.0 Hz, 2H), 2.36 (s, 3H).13C NMR (101 MHz, CDCl3)
d 138.51,
131.65, 129.24, 128.44, 128.20, 123.59, 120.30, 89.69, 88.85, 21.65.
1,2-diphenylethyne(3ba) [7c]: Yield: 0.051g (57 %), yellow solid,
m.p. 61e62 ꢀC. 1H NMR (400 MHz, CDCl3)
d
7.58e7.52 (m, 4H),
131.74, 128.48,
7.37e7.33 (m, 6H).13C NMR (101 MHz, CDCl3)
d
128.39, 123.41, 89.51.
1-methyl-3-(phenylethynyl)benzene(3ca) [7c]: Yield: 0.049g
(51 %), yellow oil. 1H NMR (400 MHz, CDCl3)
d
7.54e7.51 (m, 2H),
7.36e7.29 (m, 5H), 7.23 (t, J ¼ 7.6 Hz, J ¼ 7.6 Hz,1H), 7.14 (d,
1
2
J ¼ 7.6 Hz, 1H), 2.35 (s, 3H).13C NMR (101 MHz, CDCl3)
d 138.14,
132.32, 131.73, 129.30, 128.82, 128.46, 128.38, 128.30,123.51, 123.20,
89.70, 89.17, 21.39.
1-ethyl-4-(phenylethynyl)benzene(3da) [7c]: Yield: 0.062g
(60 %), yellow oil. 1H NMR (400 MHz, CDCl3)
d 7.54e7.51 (m, 2H),
7.46e7.44 (m, 2H), 7.35e7.28 (m, 3H), 7.17 (d, J ¼ 8.0 Hz, 2H), 2.65
(q, J1 ¼ 7.6 Hz, J2 ¼ 15.2 Hz,2H), 1.25e1.21 (m, 3H).13C NMR
(101 MHz, CDCl3)
d 144.80, 131.72, 131.68, 128.43, 128.19, 128.04,
123.63, 120.55, 89.73, 88.85, 28.97, 15.49.
4. Experimental section
1-butyl-4-(phenylethynyl)benzene(3ea) [11c]: Yield: 0.083g
(71 %), yellow oil. 1H NMR (400 MHz, CDCl3)
d 7.53e7.50 (m, 2H),
4.1. General Procedures
7.44 (d, J ¼ 8.0 Hz, 2H), 7.34e7.30 (m, 3H), 7.15 (d, J ¼ 8.0 Hz, 2H),
2.61(t, J 1 ¼7.6 Hz, J 2 ¼ 7.6 Hz, 2H), 1.63e1.55 (m, 2H), 1.39e1.30 (m,
2H), 0.92 (t, J1 ¼ 7.2 Hz, J2 ¼ 7.4 Hz, 3H).13C NMR (101 MHz, CDCl3)
General Procedures: 1H NMR and 13C NMR spectra were recor-
ded on a Varian 400 MHz spectrometer. The chemical shifts are
reported relative to TMS. HRMS were recorded on a Bruker Micro
TOF spectrometer equipped with an ESI ion source. Analytical thin-
d
143.52,131.68,131.64,128.60,128.44,128.18,123.63,120.50, 89.74,
88.85, 35.7, 33.54, 22.46, 14.09.
1-(tert-butyl)-4-(phenylethynyl)benzene(3fa)
[7c]:
Yield:
0.080g (68 %), white solid, m.p. 57e61 ꢀC. 1H NMR (400 MHz, CDCl3)
d
7.53e7.51 (m, 2H), 7.47 (d, J ¼ 8.0 Hz, 2H), 7.37e7.30 (m, 5H), 1.32
(s, 9H).13C NMR (101 MHz, CDCl3)
d
151.64, 131.71, 131.47, 128.43,
128.19, 125.48, 123.65, 120.38, 89.68, 88.87, 34.92, 31.32.
1-chloro-4-(phenylethynyl)benzene(3ga) [7c]: Yield: 0.083g
(78 %), white solid, m.p. 81e83 ꢀC. 1H NMR (400 MHz, CDCl3)
Scheme 2. Preparative scale synthesis of selected compounds.
d
7.54e7.52 (m, 2H), 7.50 (d, J ¼ 8.0 Hz, 2H), 7.35e7.31 (m, 5H).13
C
4

C. Wu and Q.-H. Li
Tetrahedron 96 (2021) 132370
NMR (101 MHz, CDCl3)
128.52, 123.06, 121.91, 90.46, 88.39.
d
134.38, 132.93, 131.73, 128.82, 128.61,
119.69 (d, J ¼ 4.0 Hz), 115.71 (d, J ¼ 22.2 Hz), 89.34, 87.77, 21.62. 19
F
NMR (376 MHz, CDCl3)
d
ꢂ111.23 to ꢂ111.31(m).
1-bromo-4-(phenylethynyl)benzene(3ha) [7c]: Yield: 0.087g
1-fluoro-4-(phenylethynyl)benzene(3bc) [7c]: Yield: 0.078g
(68 %), white solid, m.p. 81e83 ꢀC. 1H NMR (400 MHz, CDCl3)
(80 %), white solid, m.p. 109e111 ꢀC. 1H NMR (400 MHz, CDCl3)
d
7.52e7.50 (m, 2H), 7.45 (d, J ¼ 8.4 Hz, 2H), 7.38e7.32 (m, 5H).13
C
d
7.52e7.48 (m, 4H), 7.36e7.32 (m, 3H), 7.05e7.00 (m, 2H).13C NMR
NMR (101 MHz, CDCl3)
d
133.12, 131.71, 131.70, 128.61, 128.51,
(101 MHz, CDCl3)
d
162.61 (d, J ¼ 250.5 Hz), 133.60 (d, J ¼ 8.1 Hz),
123.01, 122.58, 122.33, 90.63, 88.44.
131.68, 128.48 (d, J ¼ 4.0 Hz), 123.22, 119.50 (d, J ¼ 3.0 Hz), 115.87,
1-fluoro-4-(phenylethynyl)benzene(3ia) [7c]: Yield: 0.089g
115.65, 89.18, 88.43. 19F NMR (376 MHz, CDCl3)
(m).
d
ꢂ110.88e110.94
(91 %), white solid, m.p. 109e111 ꢀC. 1H NMR (400 MHz, CDCl3)
d
7.52e7.48 (m, 4H), 7.36e7.32 (m, 3H), 7.05e7.00 (m, 2H).13C NMR
1-((4-fluorophenyl)ethynyl)-3-methylbenzene(3 cb) [14]: Yield:
(101 MHz, CDCl3)
d
162.61 (d, J ¼ 250.5 Hz), 133.60 (d, J ¼ 8.1 Hz),
0.090g (86 %), white solid, m.p. 65e67 ꢀC. 1H NMR (400 MHz,
131.68, 128.48 (d, J ¼ 4.0 Hz), 123.22, 119.50 (d, J ¼ 3.0 Hz), 115.87,
CDCl3)
d
7.49e7.45 (m, 2H), 7.33e7.30 (m, 2H), 7.20 (t, J1 ¼ 7.6 Hz,
115.65, 89.18, 88.43. 19F NMR (376 MHz, CDCl3)
d
ꢂ110.88
J2 ¼ 7.6 Hz,1H), 7.11 (t, J1 ¼7.2 Hz, J2 ¼ 3.6 Hz,1H), 7.00 (t, J1 ¼8.8 Hz,
to ꢂ110.94 (m).
J2 ¼ 8.8 Hz, 2H), 2.32 (s, 3H).13C NMR (101 MHz, CDCl3)
d162.54 (d,
1-fluoro-3-(phenylethynyl)benzene(3ja) [7c]:Yield: 0.089g
(91 %), yellow solid, m.p. 30e33 ꢀC.1H NMR (400 MHz, CDCl3)
J ¼ 250.5 Hz), 138.15, 133.55 (d, J ¼ 8.1 Hz), 132.24, 129.35, 128.74,
128.38, 123.00, 119.58 (d, J ¼ 3.0 Hz), 115.71 (d, J ¼ 22.2 Hz), 89.37,
d
7.53e7.51 (m, 2H), 7.34e7.27 (m, 5H), 7.23e7.21 (m, 1H),
88.08, 21.33. 19F NMR (376 MHz, CDCl3)
d
ꢂ111.09 (d, J ¼ 11.3 Hz).
7.05e7.00 (m, 1H).13
C
NMR (101 MHz, CDCl3) 162.53 (d,
d
1-ethyl-4-((4-fluorophenyl)ethynyl)benzene(3 db) [7c]: Yield:
J ¼ 247.5 Hz), 131.80, 130.03 (d, J ¼ 9.1 Hz), 128.71, 128.52, 127.61 (d,
J ¼ 3.0 Hz), 125.27 (d, J ¼ 9.1 Hz), 122.91, 118.48 (d, J ¼ 22.2 Hz),
115.70 (d, J ¼ 21.2 Hz), 90.40, 88.24 (d, J ¼ 4.0 Hz). 19F NMR
0.080g (75 %), white solid, m.p. 49e52 ꢀC. 1H NMR (400 MHz,
CDCl3)
7.02e6.98 (m, 2H), 2.66e2.60 (m, 2H), 1.24e1.20 (m, 3H).13C NMR
(101 MHz, CDCl3)
162.48 (d, J ¼ 250.5 Hz), 144.87, 133.50 (d,
d
7.49e7.42 (m, 4H), 7.15 (t, J1 ¼ 6.4 Hz, J2 ¼ 3.2 Hz, 2H),
(376 MHz, CDCl3)
d
ꢂ112.91 to ꢂ112.95 (m).
d
1-fluoro-2-(phenylethynyl)benzene(3ka) [7c]: Yield: 0.090g
J ¼ 8.1 Hz), 131.65, 128.06, 120.36, 119.69, 115.68 (d, J ¼ 22.2 Hz),
(92 %), white solid, m.p. 46e48 ꢀC.1H NMR (400 MHz, CDCl3)
89.40, 87.77, 28.95, 15.45. 19F NMR (376 MHz, CDCl3)
d
ꢂ111.28
d
7.56e7.49 (m, 3H), 7.34e7.26 (m, 4H), 7.12e7.06 (m, 2H).13C NMR
to ꢂ111.33 (m).
(101 MHz, CDCl3)
d
162.74 (d, J ¼ 252.5 Hz),133.55,131.81,130.08 (d,
1-butyl-4-((4-fluorophenyl)ethynyl)benzene(3eb) [15]: Yield:
0.105g (83 %), white solid, m.p. 48e49 ꢀC. 1H NMR (400 MHz, CDCl3)
J ¼ 8.1 Hz), 128.71, 128.48, 124.08 (d, J ¼ 4.0 Hz), 123.02, 115.64 (d,
J ¼ 21.2 Hz), 112.04 (d, J ¼ 15.2 Hz), 94.56, 82.82. 19F NMR (376 MHz,
d
7.50e7.46 (m, 2H), 7.42 (d, J ¼ 8.4 Hz, 2H), 7.14 (d, J ¼ 8.0 Hz, 2H),
CDCl3)
d
ꢂ109.78 to ꢂ109.84 (m).
7.03e6.99 (m, 2H), 2.60 (t, J1 ¼7.6 Hz, J2 ¼ 8.0 Hz, 2H), 1.62e1.55 (m,
1,3-difluoro-5-(phenylethynyl)benzene(3la) [7c]: Yield: 0.094g
2H), 1.39e1.29 (m, 2H), 0.92 (t, J1 ¼ 7.2 Hz, J2 ¼ 7.2 Hz, 3H).13C NMR
(88 %), yellow solid, m.p. 39e41 ꢀC. 1H NMR (400 MHz, CDCl3)
(101 MHz, CDCl3)
d
162.50 (d, J ¼ 250.5 Hz), 143.60, 133.51 (d,
d
7.53e7.50 (m, 2H), 7.35e7.34 (m, 3H), 7.03e7.01 (m, 2H),
J ¼ 8.1 Hz), 131.58, 128.62, 120.33, 119.74 (d, J ¼ 4.0 Hz), 115.70 (d,
6.81e6.75 (m, 1H).13
C
NMR (101 MHz, CDCl3) 162.91 (d,
d
J ¼ 22.2 Hz), 89.41, 87.77, 35.73, 33.52, 22.45, 14.06. 19F NMR
J ¼ 249.5 Hz), 162.77 (d, J ¼ 250.5 Hz), 131.88, 128.82 (d, J ¼ 47.5 Hz),
(376 MHz, CDCl3)
d
ꢂ111.36.
126.13, 122.45, 114.77e114.50 (m), 104.50 (t, J1 ¼ 25.3 Hz,
1-(tert-butyl)-4-((4-fluorophenyl)ethynyl)benzene(3 fb) [16]:
J2 ¼ 25.8 Hz), 91.44, 87.24. 19F NMR (376 MHz, CDCl3)
J ¼ 7.5 Hz).
d
ꢂ109.72 (t,
Yield: 0.108g (86 %), white solid, m.p. 95e98 ꢀC. 1H NMR (400 MHz,
CDCl3)
d 7.49e7.43 (m, 4H), 7.35e7.33 (m, 2H), 7.01e6.97 (m, 2H),
1-(phenylethynyl)-4-(trifluoromethyl)benzene(3ma)
[7c]:
1.30 (s, 9H).13C NMR (101 MHz, CDCl3)
d
162.49 (d, J ¼ 250.5 Hz),
Yield: 0.106g (86 %), white solid, m.p. 103e105 ꢀC. 1H NMR
151.71, 133.54 (d, J ¼ 8.1 Hz), 131.43, 125.50, 120.19, 119.74 (d,
(400 MHz, CDCl3)
(101 MHz, CDCl3)
d
d
7.61e7.53 (m, 6H), 7.34e7.35 (m, 3H).13C NMR
131.91 (d, J ¼ 5.1 Hz), 130.02 (d, J ¼ 32.3 Hz),
J ¼ 3.0 Hz), 115.69 (d, J ¼ 22.2 Hz), 89.35, 87.80, 34.90, 31.29. 19F
NMR (376 MHz, CDCl3)
d
ꢂ111.24 to ꢂ111.29 (m).
128.96, 128.59, 127.26, 125.40(q, J1 ¼ 4.0 Hz, J2 ¼ 7.1 Hz), 122.71,
1-chloro-4-((4-fluorophenyl)ethynyl)benzene(3gb) [17]: Yield:
91.91, 88.12. 19F NMR (376 MHz, CDCl3)
2-(phenylethynyl)thiophene(3na) [7c]: Yield: 0.044g (48 %),
yellow solid, m.p. 49e52 ꢀC. 1H NMR (400 MHz, CDCl3)
7.52e7.50
d
ꢂ62.78.
0.099g (86 %), white solid, m.p. 111e114 ꢀC. 1H NMR (400 MHz,
CDCl3)
d
7.50e7.40 (m, 4H), 7.32e7.28 (m, 2H), 7.05e7.00 (m,
162.71 (d, J ¼ 251.5Hz), 134.45,
d
2H).13C NMR (101 MHz, CDCl3)
d
(m, 2H), 7.35e7.33 (m, 3H), 7.28 (d, J ¼ 4.0 Hz, 2H), 7.00 (t,
133.61 (d, J ¼ 8.4 Hz), 132.86, 128.83, 121.70, 119.13, 115.82 (d,
J1 ¼ 4.8 Hz, J2 ¼ 4.4 Hz, 1H).13C NMR (101 MHz, CDCl3)
d
132.02,
J ¼ 22.2 Hz), 89.36, 88.07. 19F NMR (376 MHz, CDCl3)
d
ꢂ110.45.
131.54, 128.55, 128.50, 127.38, 127.23, 123.44, 123.04, 93.16, 82.74.
1-bromo-4-((4-fluorophenyl)ethynyl)benzene(3 hb) [18]: Yield:
2-(phenylethynyl)naphthalene(3oa) [12]: Yield: 0.093g (82 %),
0.111g (81 %), white solid, m.p. 106e108 ꢀC. 1H NMR (400 MHz,
white solid, m.p. 106e108 ꢀC. 1H NMR (400 MHz, CDCl3)
d
8.04 (s,
CDCl3)
d 7.50e7.45 (m, 4H), 7.36e7.34 (m, 2H), 7.05e7.00 (m,
1H), 7.80e7.77 (m, 3H), 7.58e7.56 (m, 3H), 7.48e7.45 (m, 2H), 7.34
2H).13C NMR (101 MHz, CDCl3)
d
162.71 (d, J ¼ 250.5 Hz), 133.60 (d,
(d, J ¼ 6.8 Hz, 3H).13C NMR (101 MHz, CDCl3)
d
133.14,132.91,131.78,
J ¼ 8.1 Hz), 133.06, 131.75, 122.67, 122.16, 119.13 (d, J ¼ 3.0 Hz),
131.56, 128.54, 128.51, 128.43, 128.13, 127.90, 127.89, 127.78,
127.6,123.41, 120.70, 89.95, 88.89.
115.83 (d, J ¼ 22.2 Hz), 89.55, 88.13. 19F NMR (376 MHz, CDCl3)
d
ꢂ110.38 to ꢂ110.42 (m).
isopropoxy4-(phenylethynyl)benzoate (4pa): Yield: 0.079g
1,2-bis(4-fluorophenyl)ethyne(3ib) [7c]: Yield: 0.088g (82 %),
(61 %), white solid, m.p. 98e100 ꢀC. 1H NMR (400 MHz, CDCl3)
white solid, m.p. 92e94 ꢀC. 1H NMR (400 MHz, CDCl3)
(m, 4H), 7.04e6.99 (m, 4H).13C NMR (101 MHz, CDCl3)
d
7.49e7.46
d
8.03e8.00 (m, 2H), 7.59e7.54 (m, 4H), 7.38e7.35 (m, 3H),
d
162.65 (d,
5.29e5.23 (m, 1H), 1.38 (d, J ¼ 6.4 Hz, 6H). 13C NMR (101 MHz,
J ¼ 250.5 Hz), 133.56 (d, J ¼ 8.1 Hz), 119.33, 115.80 (d, J ¼ 22.2 Hz),
CDCl3)
d
165.70, 131.86, 131.54, 130.38, 129.58, 128.85, 128.56,
88.09. 19F NMR (376 MHz, CDCl3)
d
ꢂ110.76 to ꢂ110.84 (m).
127.88, 122.88, 92.30, 88.87, 68.75, 22.09.
1-fluoro-3-((4-fluorophenyl)ethynyl)benzene(3jb) [7c]: Yield:
1-fluoro-4-(p-tolylethynyl)benzene(3 ab) [13]: Yield: 0.086g
0.095g (89 %), white solid, m.p. 97e99 ꢀC. 1H NMR (400 MHz,
(82 %), white solid, m.p. 90e93 ꢀC. 1H NMR (400 MHz, CDCl3)
CDCl3)
d
7.51e7.47 (m, 2H), 7.28 (s, 2H), 7.20 (d, J ¼ 8.4 Hz, 1H), 7.03
d
7.50e7.46 (m, 2H), 7.40 (d, J ¼ 8.0 Hz, 2H), 7.14 (d, J ¼ 8.0 Hz, 2H),
7.03e6.99 (m, 2H), 2.35 (s, 3H).13C NMR (101 MHz, CDCl3)
162.50
(d, J ¼ 250.5 Hz),138.59,133.51 (d, J ¼ 9.1 Hz),131.56,129.26, 120.12,
(t, J1 ¼8.8 Hz, J2 ¼ 8.6 Hz,3H).13C NMR (101 MHz, CDCl3)
d 162.80 (d,
d
J ¼ 251.5 Hz), 162.52 (d, J ¼ 248.5 Hz), 133.70 (d, J ¼ 8.1 Hz), 130.06
(d, J ¼ 9.1 Hz), 127.55 (d, J ¼ 3.0 Hz), 125.08 (d, J ¼ 9.1 Hz), 119.02 (d,
5

C. Wu and Q.-H. Li
Tetrahedron 96 (2021) 132370
J ¼ 3.0 Hz), 118.43 (d, J ¼ 23.2Hz), 115.81 (q, J1 ¼7.1 Hz, J2 ¼ 21.7 Hz),
(s, 3H), 1.63e1.53 (m, 2H),1.37e1.30 (m, 2H), 0.92 (t, J1 ¼ 7.2 Hz,
89.31, 87.95. 19F NMR (376 MHz, CDCl3)
d-110.32 to ꢂ110.38
J2 ¼ 7.4 Hz, 3H).13C NMR (101 MHz, CDCl3)
d 143.32, 138.28, 131.58,
(m), ꢂ112.85 to ꢂ112.90 (m).
129.21, 128.57, 120.74, 120.58, 89.06, 89.02, 35.74, 33.55, 22.46,
21.64, 14.08. HRMS (ESI) m/z calcd for C19Hþ21 (M þ H)þ 249.16378,
found 249.16393.
1-fluoro-2-((4-fluorophenyl)ethynyl)benzene(3 kb) [7c]: Yield:
0.093g (87 %), white solid, m.p. 108e111 ꢀC. 1H NMR (400 MHz,
CDCl3)
d
7.54e7.47 (m, 3H), 7.31e7.26 (m, 1H), 7.12e7.01 (m, 4H).13
C
1-(tert-butyl)-4-(p-tolylethynyl)benzene(3fc)
0.074g (60 %), white solid, m.p. 115e118 ꢀC. 1H NMR (400 MHz,
CDCl3)
7.46e7.40 (m, 4H), 7.35 (d, J ¼ 8.4 Hz, 2H), 7.14 (d, J ¼ 8.0 Hz,
2H), 2.36 (s, 3H), 1.32 (s, 9H).13C NMR (101 MHz, CDCl3)
151.46,
[21]:
Yield:
NMR (101 MHz, CDCl3)
d
162.80 (d, J ¼ 250.5 Hz), 162.73 (d,
J ¼ 253.5 Hz), 133.65 (t, J1 ¼ 8.1 Hz, J2 ¼ 14.7 Hz), 130.16 (d,
J ¼ 8.1 Hz), 124.10 (d, J ¼ 4.0 Hz), 119.13 (d, J ¼ 3.0 Hz),
115.90e115.55 (q, J1 ¼ 14.1 Hz, J2 ¼ 21.7 Hz), 111.86 (d, J ¼ 15.2 Hz),
d
d
138.29, 131.60, 131.41,129.21, 125.45, 120.60, 89.03, 89.00, 34.92,
31.34, 21.64.
93.43, 82.53. 19F NMR (376 MHz, CDCl3)
d
ꢂ109.91, ꢂ110.41.
1,3-difluoro-5-((4-fluorophenyl)ethynyl)benzene(3lb): Yield:
1-chloro-4-(p-tolylethynyl)benzene(3gc) [7c]: Yield: 0.073g
0.095g (82 %), white solid, m.p. 84e86 ꢀC. 1H NMR (400 MHz,
(65 %), white solid, m.p. 147e151 ꢀC. 1H NMR (400 MHz, CDCl3)
CDCl3)
d
7.50e7.47 (m, 2H), 7.06e6.99 (m, 4H), 6.81e6.75 (m,
d
7.46e7.41 (m, 4H), 7.33e7.29 (m, 2H), 7.16 (d, J ¼ 8.0 Hz, 2H), 2.37
1H).13C NMR (101 MHz, CDCl3)
d163.02 (d, J ¼ 251.5 Hz), 162.79 (d,
(s, 3H).13C NMR (101 MHz, CDCl3)
d
138.80, 134.17, 132.87, 131.62,
J ¼ 250.5 Hz), 133.84 (d, J ¼ 9.1 Hz), 125.94, 118.55, 115.95 (d,
129.30, 128.78, 122.14, 119.98, 90.67, 87.75, 21.67.
J ¼ 22.2 Hz), 114.73e114.47 (m), 104.84e104.34 (m), 90.35, 86.95.
1-bromo-4-(p-tolylethynyl)benzene(3hc) [22]: Yield: 0.083g
Anal. calcd for C14H7F3: C 72.42, H 3.04; found C 72.66, H 3.11. 19
F
(62 %), white solid, m.p. 127e130 ꢀC. 1H NMR (400 MHz, CDCl3)
NMR (376 MHz, CDCl3)
d
ꢂ109.67 (t, J ¼ 7.5 Hz), ꢂ109.74.
d
7.47e7.44 (m, 2H), 7.41 (d, J ¼ 8.0 Hz, 2H), 7.38e7.35 (m, 2H), 7.15
1-fluoro-4-((4-(trifluoromethyl)phenyl)ethynyl)benzene(3 mb)
(d, J ¼ 8.0 Hz, 2H), 2.36 (s, 3H).13C NMR (101 MHz, CDCl3)
d 138.82,
[7c]: Yield: 0.121g (92 %), white solid, m.p. 75e77 ꢀC. 1H NMR
133.08, 131.70, 131.61, 129.30, 122.59, 122.37, 119.95, 90.86, 87.82,
21.67.
(400 MHz, CDCl3)
d
7.59 (s, 4H), 7.53e7.49 (m, 2H), 7.07e7.03 (m,
162.97 (d, J ¼ 251.5 Hz), 133.83 (d,
2H).13C NMR (101 MHz, CDCl3)
d
1-fluoro-4-(p-tolylethynyl)benzene(3ic) [23]: Yield: 0.077g
J ¼ 8.1 Hz),131.89,130.12(d, J ¼ 32.3 Hz),127.09,125.49e125.38 (m),
(73 %), white solid, m.p. 90e93 ꢀC. 1H NMR (400 MHz, CDCl3)
122.73, 118.82 (d, J ¼ 4.0 Hz), 115.93(d, J ¼ 22.2 Hz), 90.81, 87.82. 19
F
d
7.50e7.46 (m, 2H), 7.40 (d, J ¼ 8.0 Hz, 2H), 7.14 (d, J ¼ 8.0 Hz, 2H),
NMR (376 MHz, CDCl3)
d
ꢂ62.84, ꢂ109.90 to ꢂ109.94 (m).
7.03e6.99 (m, 2H), 2.35 (s, 3H).13C NMR (101 MHz, CDCl3)
d
162.50
2-((4-fluorophenyl)ethynyl)thiophene(3 nb) [7c]: Yield: 0.060g
(d, J ¼ 250.5 Hz),138.59, 133.51 (d, J ¼ 9.1 Hz),131.56,129.26,120.12,
119.69 (d, J ¼ 4.0 Hz), 115.71 (d, J ¼ 22.2 Hz), 89.34, 87.77, 21.62.
1-fluoro-3-(p-tolylethynyl)benzene(3jc) [24]: Yield: 0.068g
(65 %), white solid, m.p. 60e63 ꢀC. 1H NMR (400 MHz, CDCl3)
(59 %), white solid, m.p. 73e76 ꢀC. 1H NMR (400 MHz, CDCl3)
d
7.49e7.46 (m, 2H), 7.26 (d, J ¼ 5.2 Hz, 2H), 7.04e6.98 (m, 3H).13
C
NMR (101 MHz, CDCl3)
d
162.69 (d, J ¼ 250.5 Hz), 133.45 (d,
J ¼ 8.1 Hz), 132.05, 127.43, 127.23, 123.24, 119.16 (d, J ¼ 4.0 Hz),
d
7.42e7.33 (m, 2H), 7.27e7.13 (m, 5H), 7.03e6.99 (m, 1H), 2.35 (s,
115.81 (d, J ¼ 22.2 Hz), 92.07, 82.46. 19F NMR (376 MHz, CDCl3)
3H).13C NMR (101 MHz, CDCl3)
d
162.55 (d, J ¼ 247.5 Hz), 138.92,
d
ꢂ110.48 to ꢂ110.52 (m).
131.71, 129.98 (d, J ¼ 9.1 Hz), 129.30, 127.55 (d, J ¼ 3.0 Hz), 125.52 (d,
J ¼ 9.1 Hz), 119.86, 118.42 (d, J ¼ 22.2 Hz), 115.51 (d, J ¼ 21.2 Hz),
90.64, 87.66, 21.67.
2-((4-fluorophenyl)ethynyl)naphthalene(3ob)
[19]:
Yield:
0.095g (77 %), white solid, m.p. 109e110 ꢀC.1H NMR (400 MHz,
CDCl3)
d
8.03 (s, 1H), 7.79e7.76 (m, 3H), 7.56e7.45 (m, 5H), 7.03 (t,
1-fluoro-2-(p-tolylethynyl)benzene(3kc) [25]: Yield: 0.063g
J1 ¼ 8.4 Hz, J1 ¼ 8.6 Hz, 2H).13C NMR (101 MHz,CDCl3)
d162.62 (d,
(60 %), white solid, m.p. 55e57 ꢀC. 1H NMR (400 MHz, CDCl3)
d
J ¼ 250.5 Hz), 133.64 (d, J ¼ 8.1 Hz), 133.02 (d, J ¼ 19.2 Hz), 131.53,
128.42, 128.16, 127.89, 126.76 (d, J ¼ 12.1 Hz), 120.50, 119.49, 115.79
7.53e7.44 (m, 3H), 7.30e7.26 (m, 1H), 7.17e7.06 (m, 4H), 2.36 (s,
3H).13C NMR (101 MHz, CDCl3)
d
162.70 (d, J ¼ 252.5 Hz), 138.90,
(d, J ¼ 22.2 Hz), 89.63, 88.79. 19F NMR (376 MHz, CDCl3)
d
ꢂ110.79.
133.52, 131.72, 129.81 (d, J ¼ 8.1 Hz), 129.26, 124.05 (d, J ¼ 4.0 Hz),
119.96, 115.62 (d, J ¼ 21.2 Hz), 112.17, 94.77, 82.17, 21.65.
1,2-di-p-tolylethyne(3ac) [7c]: Yield: 0.060g (58 %), white solid,
m.p. 132e135 ꢀC. 1H NMR (400 MHz, CDCl3)
d
7.41 (d, J ¼ 8.0 Hz,
1,3-difluoro-5-(p-tolylethynyl)benzene(3lc) [26]: Yield: 0.080g
4H), 7.13 (d, J ¼ 7.6 Hz, 4H), 2.35 (s, 6H).13C NMR (101 MHz, CDCl3)
(70 %), yellow solid, m.p. 68e70 ꢀC.1H NMR (400 MHz, CDCl3)
d
7.40
(d, J ¼ 8.0 Hz, 2H), 7.15e6.99 (m, 4H), 6.78e6.73 (m, 1H), 2.35 (s,
3H).13C NMR (101 MHz, CDCl3)
d
138.29, 131.56, 129.21, 120.51, 89.01, 21.62.
1-methyl-4-(phenylethynyl)benzene(3bc) [7c]: Yield: 0.056g
d
162.89 (d, J ¼ 250.5 Hz), 162.76 (d,
(58 %), white solid, m.p. 70e71 ꢀC. 1H NMR (400 MHz,CDCl3)
J ¼ 249.5 Hz), 139.30, 131.77, 129.34, 126.36, 119.37, 114.53(q,
J1 ¼7.1 Hz, J2 ¼ 15.2 Hz), 110.10, 104.27 (t, J1 ¼ 25.3 Hz, J1 ¼ 25.8 Hz),
91.72, 86.68, 21.64.
d
7.53e7.50 (m, 2H), 7.42 (d, J ¼ 8.4 Hz, 2H), 7.35e7.28 (m, 3H), 7.14
(d, J ¼ 8.0 Hz, 2H), 2.36 (s, 3H).13C NMR (101 MHz, CDCl3)
d 138.51,
131.65, 129.24, 128.44, 128.20, 123.59, 120.30, 89.69, 88.85, 21.65.
1-methyl-4-((4-(trifluoromethyl)phenyl)ethynyl)benzene
1-methyl-3-(p-tolylethynyl)benzene(3 cc) [20]: Yield: 0.046g
(3mc) [27]: Yield: 0.101g (78 %), white solid, m.p. 140e143 ꢀC. 1H
(45 %), white solid, m.p. 71e73 ꢀC. 1H NMR (400 MHz, CDCl3)
d
7.34
NMR (400 MHz, CDCl3)
d
7.52e7.47 (m, 4H), 7.35 (d, J ¼ 8.0 Hz, 2H),
139.22,
(d, J ¼ 8.0 Hz, 2H), 7.27e7.24 (m, 2H), 7.14 (t, J1 ¼ 7.6 Hz,
7.08e7.06 (m, 2H), 2.27 (s, 3H).13C NMR (101 MHz, CDCl3)
d
J2 ¼ 7.6 Hz,1H), 7.06 (t, J1 ¼8.0 Hz, J2 ¼ 7.8 Hz, 3H), 2.27 (d, J ¼ 6.4 Hz,
131.82 (d, J ¼ 6.1 Hz), 130.00, 129.67, 129.36, 127.49, 125.37 (d,
6H).13C NMR (101 MHz, CDCl3)
d 138.41, 138.10, 132.26, 131.61,
J ¼ 3.0 Hz), 122.78, 119.63, 92.18, 87.55, 21.66.
129.23, 129.11, 128.75, 128.34, 123.40, 120.42, 89.35, 89.03, 21.64,
21.38.
2-(p-tolylethynyl)thiophene(3nc) [7c]: Yield: 0.041g (41 %),
yellow solid, m.p. 59e63 ꢀC. 1H NMR (400 MHz, CDCl3)
d 7.33 (d,
1-ethyl-4-(p-tolylethynyl)benzene(3dc) [18]: Yield: 0.075g
J ¼ 8.0 Hz, 2H), 7.19e7.16 (m, 2H), 7.07 (d, J ¼ 8.0 Hz, 2H), 6.93e6.90
(68 %), white solid, m.p. 58e60 ꢀC. 1H NMR (400 MHz, CDCl3)
d
7.42
(m, 1H), 2.29 (d, J ¼ 9.2 Hz, 3H).13C NMR (101 MHz, CDCl3)
d 138.73,
(t, J1 ¼ 9.6 Hz, J2 ¼ 9.0 Hz, 4H), 7.14 (t, J1 ¼ 10.4 Hz, J2 ¼ 9.2 Hz, 4H),
131.77, 131.45, 129.56, 129.27, 127.18, 127.13, 126.93, 123.70, 119.96,
93.36, 82.06, 21.67.
2.67e2.61 (m, 2H), 2.34 (s, 3H), 1.23 (t, J1 ¼ 7.6 Hz, J2 ¼ 7.6 Hz,
3H).13C NMR (101 MHz, CDCl3)
d
144.60, 138.28, 131.66, 131.58,
2-(p-tolylethynyl)naphthalene(3oc) [28]: Yield: 0.082g (68 %),
129.21, 128.01, 120.78, 120.57, 89.05, 89.01, 28.97, 21.63, 15.48.
white solid, m.p. 130e133 ꢀC. 1H NMR (400 MHz, CDCl3)
d 8.03 (s,
1-butyl-4-(p-tolylethynyl)benzene(3ec): Yield: 0.082g (66 %),
1H), 7.81e7.77 (m, 3H), 7.58e7.55 (m, 1H), 7.47 (d, J ¼ 8.0 Hz, 4H),
white solid, m.p. 30e31 ꢀC. 1H NMR (400 MHz, CDCl3)
d7.44e7.40
7.16 (d, J ¼ 8.0 Hz, 2H), 2.36 (s, 3H).13C NMR (101 MHz, CDCl3)
(m, 4H), 7.15e7.12 (m, 4H), 2.60 (t, J1 ¼ 8.0 Hz, J2 ¼ 7.8 Hz, 2H), 2.35
d
138.58, 133.17, 132.85, 131.68, 131.41, 129.29, 128.58, 128.09,
6

C. Wu and Q.-H. Li
Tetrahedron 96 (2021) 132370
(k) X.-M. Ren, S.-N. Kong, Q.-D. Shu, M.-H. Shu, Chin. J. Chem. 34 (2016) 373;
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X.-D. Shi, Angew. Chem. Int. Ed. 54 (2015) 8772;
(o) C.W.D. Gallop, M.-T. Chen, O. Navarro, Org. Lett. 16 (2014) 3724;
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(q) L.-M. Tan, Z.-Y. Sem, W.-Y. Chong, X.-Q. Liu, Hendra, W.L. Kwan, C.L.K. Lee,
Org. Lett. 15 (2013) 65;
127.88, 126.68, 127.63, 120.92, 120.33, 90.09, 89.29, 21.67.
Declaration of competing interest
There are no conflicts to declare.
Acknowledgments
(r) H. Hu, F. Yang, Y.-J. Wu, J. Org. Chem. 78 (2013) 10506;
(s) G.-Y. Jin, X.-X. Zhang, S. Cao, Org. Lett. 15 (2013) 3114;
The authors are grateful to the the graduate student innovation
funds of Southwest Minzu University (No. CX2021SZ07), and the
Sichuan Provincial Department of science and technology support
program (No. 2015NZ0033)for financial support.
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(y) C. Torborg, J. Huang, T. Schulz, B. Schaffner, A. Zapf, A. Spannenberg,
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Appendix A. Supplementary data
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Supplementary data to this article can be found online at
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