Transition-Metal-Catalyst-Free Cross-Coupling Reaction of Secondary Propargylic Acetates with Alkenyl- and Arylboronic Acids

Article abstract of DOI:10.1002/ejoc.201701450

A cross-coupling reaction between secondary propargylic acetates and alkenylboronic acids proceeded to give 1,4-enynes in good yields without addition of transition metal catalyst and base. This simple protocol was also applicable to arylboronic acids, which gave 3-arylated alkynes in good yields. The observed induction period suggested that the reaction of propargylic acetates and organoboronic acids was affected by the in-situ generated AcOH as a catalyst, which was confirmed by a separate experiment.

Full text of DOI:10.1002/ejoc.201701450

A Journal of
Accepted Article
Title: Transition-Metal-Catalyst-Free Cross-Coupling Reaction of
Secondary Propargylic Acetates with Alkenyl- and Arylboronic
Acids
Authors: Mitsuhiro Ueda, Daiki Nakakoji, Takahiro Morisaki, and
Ilhyong Ryu
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201701450
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10.1002/ejoc.201701450
European Journal of Organic Chemistry
COMMUNICATION
Transition-Metal-Catalyst-Free Cross-Coupling Reaction of
Secondary Propargylic Acetates with Alkenyl- and Arylboronic
Acids
Mitsuhiro Ueda,*[a] Daiki Nakakoji,[a] Takahiro Morisaki,[a] and Ilhyong Ryu[a]
(a) Kabalka's Work (2004)
Abstract: A cross-coupling reaction between secondary propargylic
Ph
Ph
acetates and alkenylboronic acids proceeded to give 1,4-enynes in
good yields without adding transition metal catalyst and base. This
simple protocol was also applicable to arylboronic acids, which gave
3-arylated alkynes in good yields. The observed induction period
suggested that the reaction of propargylic acetates and
organoboronic acids was affected by the in-situ generated AcOH as
a catalyst, which was confirmed by a separate experiment.
Ph
n-BuLi
OH
Ph
Br2B
Ph
Ph
+
Br
Ph Br
(b) Our Previous Work (2013)
Ph
Ph
Ph
Cs2CO3
Cs2CO3
Ph
+
(HO)2B
Br
(OH)2BC6H4-4-OMe
C6H4-4-OMe
(c) Gandon's Work (2015)
Ph
Propargylic alcohol esters, which are easy to synthesize from
terminal acetylenes and aldehydes, serve as useful coupling
partners for organoboronic acids.1 For example, the Pd-
catalyzed propargylation of arylboronic acids2 and vinylboronic
acids3 was reported thus far to give acetylenic products. In
recent times, efforts have been directed to develop transition-
metal-free reactions. Nearly two decades ago, Kabalka and co-
workers reported that the cross-coupling reaction of secondary
propargylic alcohols with alkenylboron dihalides proceeded to
give acetylenic products under catalyst-free conditions (Scheme
1-a).4 In this reaction, a stoichiometric amount of n-BuLi is used
as a base to prepare (halovinyl)(propargyloxy)boron halides
working as a key intermediate. In 2013, we reported the
transition-metal-free cross-coupling reaction of alkenylboronic
acids and arylboronic acids with propargylic bromides in the
presence of Cs2CO3 as a base (Scheme 1-b).5,6 Recently
Gandon and co-workers found that the cross-coupling reaction
of propargylic alcohols with alkenylboronic acids proceeds
efficiently by using Ca(NTf2)2 as a catalyst (Scheme 1-c).7,8,9
Herein, we report that the cross-coupling reaction of propargylic
acetates with alkenylboronic acids proceeds spontaneously to
give 1,4-enynes in good yields (Scheme 1-d). We also report
that, when arylboronic acids are used instead of alkenylboronic
acids, 3-aryl-substituted alkynes are obtained in good yields.
Ph
Ca(NTf2)2
Ph
OH
+
Ph
(HO)2B
Ph
Ph
(d) This Work
Ph
Ph
Ph
no additive
no additive
Ph
OAc
Ph
+
(HO)2B
Ph
Ph
Ph
C6H4-4-OMe
(OH)2BC6H4-4-OMe
Scheme 1. Transition-Metal-Free Cross-Coupling Reaction of Propargylic
Alcohol Derivatives with Alkenyl- and Arylboron Reagents.
When 1,3-diphenylprop-2-yn-1-yl acetate (1a) was treated with
(E)-(4-methoxystyryl)boronic acid (2a) in dioxane at 90 °C for 5 h,
the cross-coupling reaction took place to give the enyne 3a in
18% yield (Table1, entry 1).
Switching the solvent from
dioxane to DMF, toluene, and BTF did not give any products
(entries 2-4). To our delight, the use of 1,2-dichloroethane (1,2-
DCE) as a solvent dramatically improved the yield (78%, entry 5).
The addition of a base such as K2CO3 resulted in no reaction
(entry 6). While benzoate 1b was also applicable to the present
reaction (entry 7), the reaction of the corresponding methyl
carbonate 1c with 2a was sluggish, giving 3a in 11% yield (entry
8). Alkenylboronic acid esters 4a and 4b, and fluoroborate anion
4c did not participate in the present cross-coupling reaction
(Scheme 2).
[a]
Mitsuhiro Ueda,* Daiki Nakakoji, Takahiro Morisaki, and Ilhyong Ryu
Department of Chemistry, Graduate School of Science
Osaka Prefecture University
Sakai, Osaka 599-8531, Japan
E-mail: ueda@c.s.osakafu-u.ac.jp
Table 1. Optimization of the Reaction Conditions.[a]
OMe
Ph
OMe
solvent
Ph
O
R
+
(HO)2B
Ph
O
90 °C, 5 h
Ph
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
1
2a (1.5 equiv)
3a
Entry
1
Solvent
dioxane
R
Yield (%)[b]
Me (1a)
18
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10.1002/ejoc.201701450
European Journal of Organic Chemistry
COMMUNICATION
and 6g (vide infra). Aliphatic alkyne and terminal alkyne,
such as 1-phenylhept-2-yn-1-yl acetate (1f) and 1-
phenylprop-2-yn-1yl acetate (1j), were also examined. The
reaction of 1f and 1j with 5a led to the corresponding
coupling products, 6h and 6i, in good yields. On the other
hand, phenylboronic acid and electron-deficient arylboronic
acids, such as 4-nitrophenylboronic acid, did not participate
in the reaction.
The reaction of some other electron-rich arylboronic acids
5b-5d with 1a proceeded well to give 6j-6l in good yields (78%-
82%). The reaction of 2-methoxy-5-methylphenylboronic acid
(5e) with 1a gave 6m in 78% yield. The reaction of 5-chloro-2-
methoxyphenylboronic acid (5f) gave the corresponding product
6n in moderate yield due to the slow reaction (55%). 2-
Furylboronic acid (5g) tolerated the reaction conditions and
formed the corresponding coupling product 6o in an 80% yield.
2
DMF
Me (1a)
Me (1a)
Me (1a)
Me (1a)
Me (1a)
Ph (1b)
OMe (1c)
0
3
toluene
BTF[c]
0
4
0
5
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
78
0
6[d]
7
73
11
8
[a] Reaction conditions: 1 (0.5 mmol), 2a (0.75 mmol), solvent (0.33 mL), 90
°C, 5 h. [b] Isolated yield of 3a. [c] BTF: Benzotrifluoride. [d] Used K2CO3 (1
equiv).
Table 2. Substrate Scope of Coupling Reaction of Secondary Propargylic
Acetates 1 with Styrylboronic Acid 2.[a]
OMe
OMe
OMe
NMe
R
R
O
B
OAc
Ar1
Ar2
O
O
Ar2
+
O
O
B
(HO)2B
KF3B
O
1,2-DCE
90 °C, 5 h
Ar1
4a
4b
4c
1
2 (1.5 equiv)
3
R
/ Ar1
: Ph / 4-MeO-C H
Ar2
Ar2
: 3-F-C H
6 4
: 4-CF -C H
2g
3 6 4
: 4-MeO-C H
: Ph
: 4-Me-C H
: 4-Cl-C H
1b
2a
2b
2c
2d
2e
2f
6
4
6
4
Scheme 2. No Reactions with Alkenylboronic Esters and Borate Derivatives
2h-2j.
: Ph / 2-MeO-C6H4
: Ph / 3-MeO-C H
: Ph / 1-Naphthyl
1c
1d
1e
1f
6
4
6
4
6
4
: Bu / Ph
: 4-F-C H
6
4
OMe
OMe
OMe
Having the optimal conditions of entry 5 in hand, we next
explored the scope of the coupling reaction of propargylic
acetates with vinylboronic acids 2a (Table 2). The reaction of 1-
(4-methoxyphenyl)-3-phenylprop-2-yn-1-yl acetate (1b) with 2a
gave the corresponding 1,3-enyne 3b in 78% yield (Table 2).
OMe
OMe
OMe
3b: 78%
3c: 70%
3d: 73%
The
phenylprop-2-yn-1-yl acetate (1c) and 1-(3-methoxyphenyl)-3-
phenylprop-2-yn-1-yl acetate (1d) showed comparable
regio-isomeric
substrates,
1-(2-methoxyphenyl)-3-
OMe
Me
a
reactivity with 1b (3c: 70%, 3d: 73%). 1-(Naphthalen-1-yl)-3-
phenylprop-2-yn-1-yl acetate (1e) reacted with 2a to give 3e in
80% yield. The reaction of (E)-alkenylboronic acids 2b-2f with 1a
proceeded well to give 3f-3j in good yields (74%-82%). The
reaction of (E)-2-[4-(trifluoromethyl)phenyl]vinylboronic acid (2g)
with 1a was sluggish and gave a 39% yield of 3k. An alkyl-
substituted acetylene, such as 1-phenylhept-2-yn-1-yl acetate
(1f), was also applicable albeit in a modest yield (3l: 58%).10
Since the catalyst-free cross-coupling of secondary
propargylic derivatives with arylboronic acids is yet to be
reported, we then examined arylboronic acids under similar
conditions, which also proved to work well (Table 3).11 For
example, the reaction of 1a with 5a proceeded to give (3-(4-
methoxyphenyl)prop-1-yne-1,3-diyl)dibenzene (6a) in good
yield (81%). In the reaction with 5a, propargylic acetates 1b
having an electron-rich phenyl group showed a comparable
reactivity with 1a (6b: 78%). On the other hand, the reaction
of propargylic acetate 1c having a 2- methoxyphenyl group
was sluggish and gave the corresponding product 6c in
moderate yield (47%). Propargylic acetate 1d, which has a
3-methoxyphenyl group, also served well as a coupling
partner. Indeed, the reaction of 1d with 5a gave the desired
coupling product 6d in 68% yield. Propargylic acetate 1i
reacted with 5a to give 6e in an 82% yield. In the cases of
propargylic acetates 1g and 1h having an electron-deficient
phenyl group, the addition of 10 mol % of AcOH was
required to obtain good yields of the coupling products 6f
3g: 82%
3e: 80%
3f: 77%
Cl
F
F
3j: 76%
3h: 74%
3i: 80%
Bu
CF3
3k: 39%
3l: 58%b
[a] Reaction conditions: 1 (0.5 mmol), 2 (0.75 mmol), 1,2-dichloroethane (0.33
mL), 90 °C, 5 h. [b] Reaction time: 24 h.
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10.1002/ejoc.201701450
European Journal of Organic Chemistry
COMMUNICATION
and 6a. These results suggest the intermediacy of propargylic
cations in the present coupling reaction (Scheme 4). The fact
that an aromatic substituent at the propargylic position was
indispensable is rationalized by the formation of the cation
intermediates.
Table 3. Substrate Scope of Coupling Reaction of Secondary Propargylic
Acetates 1 with Arylboronic Acid 5.[a]
R
R
OAc
Ar1
Ar2
Ar1
Ar2B(OH)2
+
1,2-DCE
90 °C, 5 h
1
5 (1.5 equiv)
6
R
/ Ar1
: Ph / Ph
Ar2
OMe
: 4-MeO-C H
: 4-MeS-C H
: 3,4-(MeO) -C H
2 6 3
: 3,4-(CH O )-C H
: 2-MeO-5-Me-C H
: 2-MeO-5-Cl-C6H3
: 2-furanyl
1a
1b
1c
1d
1f
1g
1h
1i
5a
5b
5c
5d
5e
5f
6
4
OMe
additive
: Ph / 4-MeO-C H
: Ph / 2-MeO-C H
: Ph / 3-MeO-C H
: Bu / Ph
: Ph / 4-Cl-C H
: Ph / 4-CF -C H
: Ph / 2-Naphthyl
: H / Ph
6
4
4
4
6
4
OAc
+
6
1,2-DCE
90 °C, 24 h
(HO)2B
6
2 2 6 3
6
3
6
4
5g
3
6
4
Cl
Cl
1g
2a (1.5 equiv)
3m
1j
no additive:
AcOH (10 mol %):
no reaction
68% yield
OMe
OMe
OMe
Scheme 3. Reaction of Propargylic Acetate Having 4-Chlorophenyl Moiety 1g
with 2a.
OMe
OMe
Ph
6a: 81%
6b: 78%
6c: 47%
OMe
OAc
Ph
+
+
(HO)2B
2b (1.5 equiv)
OMe
OMe
OMe
1,2-DCE
90 °C, 5 h
1a
(1.5 equiv)
OMe
Ph
Ph
+
OMe
Cl
Ph
3g
Ph
6a
6d: 68%
6e: 82%
6f: 76%b,c
OMe
OMe
:
:
2
1
Bu
H
GC ratio
Yield (%)
OMe
57
28
Scheme 4. Control Experiment.
CF3
6g: 75%b,c
6h: 61%c
6i: 61%c
Consequently, a mechanism involving the propargylic cation is
proposed (Scheme 5). As the first step, 1a would react with 2b
to give the ion-pair A of propargylic cation and alkenylborate
anion. This process was affected by the in-situ generated AcOH.
The propargylic cation in ion-pair A would then react with the
alkenylborate anion or 2b to give the zwitterionic intermediate B.
Finally, the desired product 3g was obtained by deboration.
SMe
OMe
OMe
O
O
6j: 80%
6k: 82%
6l: 78%
MeO
MeO
O
Me
Cl
in-situ generated
AcOH
Ph
Ph
AcO
HO
Ph
Ph
OAc
B
+
B
6m: 78%c
6n: 55%c
6o: 80%
OH
HO
OH
Ph
Ph
AcOH
1a
2b
A
[a] Reaction conditions: 1 (0.5 mmol), 2 (0.75 mmol), 1,2-dichloroethane (0.33
mL), 90 °C, 5 h. [b] 10 mol % of AcOH was added. [c] Reaction time: 24 h.
Ph
Ph
B(OH)2OAc
Ph
Ph
Ph
Ph
(HO)2BOAc
3g
B
To get some insights into the mechanism of the present
catalyst-free reaction, we carried out a time course study of the
reaction of 2b with 1a and found that there is an induction period
of the order of a few hours, and the addition of AcOH
dramatically shortened the period. Since the reaction of
propargylic acetate, having the 4-chlorophenyl moiety 1g, with
2a did not proceed, we tested the addition of AcOH. Thus, when
10 mol % of AcOH was added in the reaction of 1g with 2a, the
desired product 3m was obtained in 68% yield (Scheme 3).12
These results rigorously suggest that the reaction of propargylic
acetates and organoboronic acids would be initiated by in-situ
generated AcOH.13,14 We then examined the cross-over
experiment of 2b and anisole, which gave a 2 : 1 mixture of 3g
Scheme 5. Plausible Mechanism.
In summary, we have developed a simple protocol for
cross-coupling reaction of propargylic acetates with
alkenylboronic acids leading to 1,3-enynes, which does not
use a transition metal catalyst and a base. The protocol has
also been successfully extended to the reaction of
propargylic acetates with arylboronic acids, which gave 3-
aryl-substituted alkynes in good yields. Further studies
regarding the detailed reaction mechanism and the
application of using 2 and 6, such as the synthesis of
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10.1002/ejoc.201701450
European Journal of Organic Chemistry
COMMUNICATION
functional molecules bearing π-conjugated skeletons,15 are
[10] We also examined the reaction of 1-penten-1-ylboronic acid with 1a.
As the result, the corresponding cross-coupling product was not
obtained.
currently in progress.
[11] For Lewis acid- or Brønsted acid-catalyzed coupling reactions of
propargylic alcohols with aromatic compounds, see: (a) Y.
Nishibayashi, M. Yoshikawa, Y. Inada, M. Hidai and S. Uemura, J. Am.
Chem. Soc., 2002, 124, 11846; (b) Y. Nishibayashi, Y. Inada, M.
Yoshikawa, M. Hidai and S. Uemura, Angew. Chem., Int. Ed., 2003,
42, 1495; (c) J. J. Kennedy-Smith, L. A. Young and F. D. Toste, Org.
Lett., 2004, 6, 1325; (d) E. Bustelo, P. H. Dixneuf, Adv. Synth. Catal.,
2005, 347, 393; (e) C. Fischmeister, L. Toupet and P. H. Dixneuf, New
J. Chem., 2005, 29, 765; (f) Z.-P. Zhan, Y.-Y. Cui and H.-J. Liu,
Tetrahedron Lett., 2006, 47, 9143; (g) Z.-P. Zhan, J.-L. Yu, H.-J. Liu,
Y.-Y. Cui, R.-F. Yang, W.-Z. Yang and J.-P. Li, J. Org. Chem., 2006,
71, 8298; (h) Z.-P. Zhan and H.-J. Liu, Synlett, 2006, 2278; (i) E.
Bustelo and P. H. Dixneuf, Adv. Synth. Catal., 2007, 349, 933; (j) Y.
Yamamoto and K. Itonaga, Chem. Eur. J., 2008, 14, 10705; (k) P.
Srihari, J. S. S. Reddy, S. S. Mandal, K. Satyanarayana and J. S.
Yadav, Synthesis, 2008, 1853; (l) M. Yoshimatsu, T. Otani, S.
Matsuda, T. Yamamoto and A. Sawa, Org. Lett., 2008, 10, 4251; (m)
M. Zhang, H. Yang, Y. Cheng, Y. Zhu and C. Zhu, Tetrahedron Lett.,
2010, 51, 1176; (n) G. Aridoss, V. D. Sarca, J. F. Ponder Jr, J. Crowe
and K. K. Laali, Org. Biomol. Chem., 2011, 9, 2518; (o) M. Gohain, C.
Marais and B. C. B. Bezuidenhoudt, Tetrahedron Lett., 2012, 53,
1048; (p) Y. Masuyama, M. Hayashi and N. Suzuki, Eur. J. Org.
Chem., 2013, 2914; (q) S.-S. Weng, K.-Y. Hsieh and Z.-J. Zeng,
Tetrahedron, 2015, 71, 2549; (r) S. Jang, A. Y. Kim, W. S. Seo and K.
H. Park, Nanoscale Res. Lett., 2015, 10, 1.
Experimental Section
A magnetic stirring bar, styrylboronic acids (2a, 133.5 mg, 0.75 mmol),
propargylic acetates (1a, 125.1 mg, 0.50 mmol), 1,2-dichloroethane (0.33
mL) were placed in a screw capped test tube. The test tube was purged
with argon and sealed. The mixture was stirred at 90 °C for 5 h. After the
reaction, solvent was removed under reduced pressure. The residue was
purified by chromatography on silica-gel (hexane/ethyl acetate = 20/1) to
give 3a (126.2 mg, 78%).
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific
Research from the MEXT and the JSPS (26105752 for MU;
26248031 for IR).
Keywords: Transition-Metal-Catalyst-Free • Cross-Coupling •
Secondary Propargylic Acetates • Alkenylboronic acid •
Arylboronic acid
[12] We also examined the reaction of 4a-4c with 1a in the presence of 10
mol
% AcOH. As the results, the corresponding cross-coupling
[1] (a) Modern Acetylene Chemistry; P. J. Stang, F. Diederich, Eds.; VCH:
Weinheim, Germany, 1995; (b) F. Alonso, I. P. Beletskaya and M. Yus,
Chem. Rev., 2004, 104, 3079; (c) Acetylene Chemistry: Chemistry,
Biology and Material Science; F. Diederich, P. J. Stang and R. R.
Tykwinski, Eds.; Wiley-VCH, Weinheim, 2005; (d) B. Godoi, R. F.
Schumacher and G. Zeni, Chem. Rev., 2011, 111, 2937.
products were not obtained.
[13] It is known that electron-deficient arylboronic acids reacts with
carboxylic acids to give the acyloxyboronic acids. However, we were
unable to detect acyloxyboronic acid in the reaction of 2b with 1 equiv
of AcOH: (a) K. Ishihara, S. Ohara and H. Yamamoto, J. Org. Chem.,
1996, 61, 4196; (b) R. M. Al-Zoubi, O. Marion, D. G. Hall, Angew.
Chem., Int. Ed., 2008, 47, 2876.
[14] NMR studies: 1H NMR (400 MHz, DMSO-d6): 2e only; δ 6.05 (d, J =
18.4 Hz, 1H, -CH=CH-B), 7.14-7.26 (m, 3H, -Ph-F + -CH=CH-B), 7.52
(dd, JHH = 8.8 Hz, JHF = 5.6 Hz, 2H, -Ph-F), 7.79 (s, 2H, -B(OH)2); 2e +
AcOH (1 equiv); δ 6.06 (d, J = 18.0 Hz, 1H, -CH=CH-B), 7.18 (dd, JHH
= JHF = 8.8 Hz, 2H, -Ph-F), 7.24 (d, J = 18.4 Hz, 1H, -CH=CH-B), 7.52
(dd, JHH = 8.8 Hz, JHF = 5.6 Hz, 2H, -Ph-F), 7.79 (broad s, 2H, -B(OH)2).
11B NMR (128 MHz, DMSO-d6): 2e only; δ 27.5; 2e + AcOH (1 equiv);
δ 27.4.
[2] (a) M. Yoshida, T. Gotou and M. Ihara, Tetrahedron Lett., 2004, 45,
5573; (b) M. J. Ardolino and J. P. Morken, J. Am. Chem. Soc., 2012,
134, 8770; (c) M. J. Ardolino, M. S. Eno and J. P. Morken, Adv. Synth.
Catal., 2013, 355, 3413.
[3] Y.-B. Yu, G.-Z. He and X. Zhang, Angew. Chem., Int. Ed., 2014, 53,
10457. In this paper, the Pd-catalyzed propargylation of 1- or 2-
phenylvinylboronic
acids
with
(3-bromo-3,3-difluoroprop-1-yn-
1yl)triisopropylsilane have been reported.
[4] G. W. Kabalka, Z. Wu and Y. Ju, Org. Lett., 2004, 6, 3929.
[5] M. Ueda, K. Nishimura and I. Ryu, Synlett, 2013, 24, 1683.
[6] For examples of transition-metal-free cross-coupling reaction of
arylboronic acids; Allylic halides or Allylic alcohols as coupling partner:
(a) M. Ueda, K. Nishimura, R. Kashima and I. Ryu, Synlett, 2012, 23,
1085; (b) A. Scrivanti, V. Beghetto, M. Bertoldini and U. Matteoli, Eur.
J. Org. Chem., 2012, 264; (c) X.-D. Li, L.-J. Xie, D.-L. Kong, L. Liu and
L. Cheng, Tetrahedron 2016, 72, 1873; Benzylic halides as coupling
partner: (d) M. Ueda, D. Nakakoji, Y. Kuwahara, K. Nishimura and I.
Ryu, Tetrahedron Lett., 2016, 57, 4142; (e) C. Li, Y. Zhang, Q. Sun, T.
Gu, H. Peng and W. Tang, J. Am. Chem. Soc., 2016, 138, 10774; (f)
G. Wu, S. Xu, Y. Deng, C. Wu, X. Zhao, W. Ji and Y. Zhang,
Tetrahedron, 2016, 72, 8022.
1H NMR (400 MHz, DMSO-d6): AcOH only; δ 1.903 (s, 3H), 11.9
(broad s (10.6-13.0 ppm), 1H); AcOH + 2e (1 equiv); δ 1.904 (s, 3H),
12.0 (broad s (11.5-12.3 ppm), 1H). These results might suggest the
interaction of 2e and AcOH (pKa 4.76/H2O). In biochemistry, it is
known that
a protonated imidazole (pKa 6.95/H2O) as an acid
coordinates to hydroxyl group of alkylboronic acid: E. Tsilikounas, C. A.
Kettner and W. W. Bachovchin, Biochemistry, 1992, 31, 12839.
[15] T. Sato, T. Onuma, I. Nakamura, M. Terada, Org. Lett., 2011, 13,
4992.
[7] D. Lebœuf, M. Presset, B. Michelet, C. Bour, S. Bezzenine-Lafollée
and V. Gandon, Chem. Eur. J., 2015, 21, 11001.
[8] For Lewis acid-catalyzed cross-couplings reaction of propargylic
alcohols with alkenylsilanes, see: (a) Y. Nishimoto, M. Kajioka, T.
Saito, M. Yasuda and A. Baba, Chem. Commun., 2008, 6396; (b) V. J.
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10.1002/ejoc.201701450
European Journal of Organic Chemistry
COMMUNICATION
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COMMUNICATION
A
cross-coupling reaction between
Mitsuhiro Ueda,* Daiki Nakakoji,
secondary propargylic acetates and
alkenylboronic acids proceeded to
give 1,4-enynes in good yields without
adding transition metal catalyst and
base. This simple protocol was also
applicable to arylboronic acids, which
gave 3-arylated alkynes in good
yields.
Takahiro Morisaki, and Ilhyong Ryu
Page No. – Page No.
Transition-Metal-Catalyst-Free Cross-
Coupling Reaction of Secondary
Propargylic Acetates with Alkenyl-
and Arylboronic Acids
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