Intramolecular Catalyst Transfer on a Variety of Functional Groups between Benzene Rings in a Suzuki–Miyaura Coupling Reaction

Article abstract of DOI:10.1002/chem.201902044

Suzuki–Miyaura coupling reaction of BrC₆H₄-X-C₆H₄Br 1 (X=CH₂, CO, N-Bu, O, S, SO, and SO₂) with arylboronic acid 2 was investigated in the presence of tBu₃PPd precatalyst and CsF

Full text of DOI:10.1002/chem.201902044

A Journal of
Accepted Article
Title: Intramolecular Catalyst Transfer on a Variety of Functional
Groups between Benzene Rings in Suzuki-Miyaura Coupling
Reaction
Authors: Tsutomu Yokozawa, Natsumi Harada, Hajime Sugita, and
Yoshihiro Ohta
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201902044
Link to VoR: http://dx.doi.org/10.1002/chem.201902044
Supported by

Chemistry - A European Journal
10.1002/chem.201902044
COMMUNICATION
Intramolecular Catalyst Transfer on a Variety of Functional Groups
between Benzene Rings in Suzuki-Miyaura Coupling Reaction
[
a]
Tsutomu Yokozawa* , Natsumi Harada, Hajime Sugita, Yoshihiro Ohta
Abstract: Suzuki-Miyaura coupling reaction of BrC
6
H
4
-X-C
) with arylboronic acid 2 was
3
PPd precatalyst and CsF/18-
6
H
4
Br 1 (X
(ester)s through intramolecular catalyst transfer on the -electron
face of dibromoarylene. However, the use of monomers with
kinked structures, such as m-phenylene, in this type of
polycondensation selectively affords cyclic aromatic polymers
under unstoichometric conditions using excess diboromo
=
CH
2
, CO, N-Bu, O, S, SO, and SO
2
t
investigated in the presence of Bu
crown-6 as a base to establish whether or not the Pd catalyst can
undergo catalyst transfer on these functional groups. In the reaction
[14]
monomer.
of 1 (X = CH
2 2
, CO, N-Bu, O, and SO ) with 2, aryl-disubstituted product
We investigated catalyst transfer on not only aromatic rings, but
3
(Ar-C -X-C
6
H
4
6
H
4
-Ar) was exclusively obtained, indicating that the Pd
also multiple bonds between benzene rings in Suzuki-Miyaura
t
catalyst undergoes catalyst transfer on these functional groups. On
coupling reaction. We found that Bu
3
PPd moves on a carbon-
carbon double bond (C=C) when alkoxy substituents are attached
at the ortho position of the benzene rings connected to C=C,[
and that intramolecular catalyst transfer takes place on a carbon-
the other hand, the reaction of 1e (X = S) and 1f (X = SO) with 2
15]
6 4 6 4
afforded only aryl-monosubstituted product 4 (Ar-C H -X-C H -Br)
and a mixture of 3 and 4, respectively, indicating that S and SO
carbon triple bond and nitrogen-nitrogen double bond even when
interfere with intramolecular catalyst transfer. Furthermore, we found
[16]
there are no substituents on the benzene rings.
We had
that Suzuki-Miyaura polycondensation of 1 (X = CH
and SO
2
, CO, N-Bu, O,
focused on catalyst transfer on -conjugated systems, and as an
extension of that work, we were next interested in whether or not
the Pd catalyst can undergo intramolecular catalyst transfer on
functional groups located between benzene rings. If this is
possible, CTCP could be extended to the synthesis of well-
defined engineering plastics containing functional groups such as
keto and sulfonyl, as well as ether and sulfide linkages. In this
paper, we describe an investigation of intramolecular catalyst
t
2
) and phenylenediboronic acid 5 in the presence of Bu
3
PPd
precatalyst afforded high-molecular-weight polymer even when
excess 1 was used. The polymers obtained from 1 (X = CH
and O) and 5 turned out to be cyclic.
2
, N-Bu,
2 2
transfer on CH , CO, N-Bu, O, S, SO, SO by means of Suzuki-
Miyaura coupling reaction of dibromo compound 1, containing
these functional groups, with arylboronic acid 2 in the presence of
Bu PPd, generated from Bu PPd G2 precatalyst and base. If
3 3
intramolecular catalyst transfer takes place on the benzene rings
and these functional groups in 1 after the first substitution with 2,
disubstituted product 3 should be selectively obtained, rather than
monosubstituted product 4 (Scheme 1). We found that the Pd
Many transition metal catalysts have been developed for coupling
reactions. For example, Buchwald has improved the efficiency
t
t
and selectivity of Suzuki-Miyaura coupling reaction by introducing
dialkylbiarylphosphine-ligated Pd catalysts.[1] Furthermore,
development of the ligands of Pd catalysts has made it possible
to conduct C-N[ and C-O coupling reactions. It has recently
2]
[3]
[4]
catalyst underwent intramolecular catalyst transfer on CH
N-Bu, O, SO , and that unstoichiometric polycondensation of
excess 1 containing these functional groups with 1 equivalent of
p-phenylenediboronic acid afforded high-molecular-weight
polymers (Scheme 2). Furthermore, the obtained polymers
containing the CH , N-Bu, O linkages turned out to be cyclic,
showing clear peaks in the matrix-assisted laser
2
, CO,
been found that Pd and Ni catalysts with certain ligands have a
unique propensity for intramolecular catalyst transfer on aromatic
2
[
5]
[6]
rings in polymer chemistry. Thus, Kumada-Tamao, Negishi,
and Suzuki-Miyaura
[
7]
5
coupling polymerizations of AB-type
monomer proceed in a living polymerization manner, in which
regenerated zero-valent catalyst, after coupling reaction between
the propagating end and monomer, moves intramolecularly to the
C-X bond of the monomer connected to the propagating end,
followed by oxidative addition. We called this type of
2
desorption/ionization time-of-flight (MALDI-TOF) mass spectra.
We first conducted Suzuki-Miyaura coupling reaction of 2
equivalent of 1 containing a variety of functional groups X with 1.0
polymerization catalyst-transfer condensation polymerization
(
CTCP).[ Many kinds of well-defined -conjugated polymers
8]
equivalent of 2 in the presence of 5 mol% of Bu PPd G2
t
3
[
9]
have been synthesized by means of CTCP, as well as many
precatalyst and CsF/18-crown-6 as
a base at ambient
[
10]
architectures based on -conjugated polymers.
Recently,
temperature for 3 h (Scheme 1). The product ratio 3/4 was
Stille[ and Murahashi CTCP have also been reported.
11]
[12]
1
determined from the H NMR spectra of the crude products (Table
t
When a Pd catalyst such as Bu
3
PPd, which undergoes
1), and then the products were isolated by column
intramolecular catalyst transfer, is used for conventional Suzuki-
chromatography. When X in 1 was CH (1a), only disubstituted
2
Miyaura polycondensation
arylenediboronic acid (ester) (A
of
+ B
dibromoarylene
polycondensation), high-
and
product 3 was obtained (Table 1, Entry 1). Similar intramolecular
2
2
molecular-weight -conjugated polymers with boronic acid (ester)
ends are obtained, even if excess dibromo monomer is present
under unstochiometric polycondensation conditions.[13] This
polymerization behavior is accounted for by successive reaction
of dibromoarylene with 2 equivalents of arylenediboronic acid
catalyst transfer on disubstituted methylene between thiophenes
has been reported in Kumada-Tamao CTCP of bithienylmethane
monomer.[17] It seems strange that the Pd catalyst underwent
intramolecular transfer on non-conjugated methylene between
the benzene rings, but direct transfer from one benzene ring to
the other might occur, since the two rings face each other.
Incidentally, we have already reported that intramolecular Pd
catalyst transfer did not occur on ethylene between benzene
rings.[15] Similarly, in the case of oxidized carbon (carbonyl group)
[
a]
Prof. T. Yokozawa, N. Harada, H. Sugita, Prof. Y. Ohta
Department of Materials and Life Chemistry, Kanagawa University,
Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan
E-mail: yokozt01@kanagawa-u.ac.jp
in 1, only disubstituted 3 was obtained (Entry 2). Since 4,4’-
dibromobenzophenone 1b has a planar structure and the
carbonyl group is conjugated with two benzene rings, the Pd
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201902044
COMMUNICATION
t
Scheme 1. Suzuki-Miyaura coupling reaction of 1 with 2 in the presence of Bu
transfer on functional groups X in 1.
3
PPd for investigation of intramolecular catalyst
t
Scheme 2. Unstoichiometric Suzuki-Miyaura polycondensation of excess 1 and 1.0 equivalent of 5 in the presence of Bu
3
PPd.
catalyst should move from one benzene ring to the other through
the conjugated -electron face. Furthermore, the reaction of 1c (X
Table 1. Product ratio of 3/4 in Suzuki-Miyaura coupling
=
N-Bu) and 1d (X = O) with 2 afforded disubstituted 3 (entries 3
t
3
reaction of 1 with 2 in the presence of Bu PPd G2
precatalyst.a
and 4), implying that the lone pairs of N and O did not disturb
intramolecular transfer of the Pd catalyst by coordination. In this
connection, CTCP of 2-amino-6-bromofluorene by Buchwald-
Conv. of
Yield of
3 + 4
Product ratio
Entry
1
X in 1
b
b,c
b
1
3/4
Hartwig amination via intramolecular catalyst transfer on the
amino group was recently reported during our work.[18] In contrast
1
2
3
4
5
6
7
1a
1b
1c
1d
1e
1f
28
22
22
21
48
43
20
25
22
23
21
48
37
22
100/0
100/0
100/0
100/0
0/100
22/78
100/0
to these cases, sulfide 1e (X = S) gave only monosubstituted 4
Entry 5),[19] and sulfoxide 1f (X =SO) also mainly afforded 4
Entry 6). Interestingly, however, the reaction of sulfone 1g (X =
(
(
2
SO ) gave only 3 (Entry 7). These results apparently indicate that
the lone pair of sulfur traps the Pd catalyst, leading to
intermolecular catalyst transfer. The different behavior of N and O
in the second period and S in the third period might be accounted
for by strong interaction between the soft lone pair of sulfur and
soft Pd with a large atomic radius. In order to confirm that sulfide
linkage interferes with intramolecular catalyst transfer, we
conducted the reaction of dibromophenylene
6
with
1g
phenylboronicacid ester 7 in the absence or presence of diphenyl
sulfide (Scheme 3). When the reaction was carried out in the
absence of diphenyl sulfide, only phenyl-disubstituted phenylene
a
Reaction of 2.0 equivalent of 1 and 1.0 equivalent of 2 was
t
carried out with 5 mol% of Bu
presence of CsF (4.0 equivalent) and 18-crown-6 (6.7
equivalent) in THF ([2] = 50.0 mM) and H O (THF/H O =
.0/0.1 (v/v)) at room temperature for 3 h. Determined from
3
PPd G2 precatalyst in the
8
was obtained, indicating that intramolecular catalyst transfer
0
2
2
took place on 6. On the other hand, the reaction of 6 with 7 in the
presence of diphenyl sulfide equimolar to 6 afforded 8 and
monosubstituted 9 in the ratio of 56/44. This indicates that
diphenyl sulfide can trap the Pd catalyst during transfer on the
b
3
1
c
the H NMR spectra. Yield is based on 1.
monomers.[13a]
polycondensation
polycondensation using 1a-d, and 1g, which exhibited
intramolecular catalyst transfer in the reaction with 2 (Table 1),
of
aromatic
Indeed,
benzene ring of 6, resulting in intermolecular catalyst transfer.
t
Since we found that Bu
3
PPd undergoes intramolecular transfer
on several functional groups, we applied this chemistry to Suzuki-
Miyaura unstoichiometric polycondensation of 1.3 equivalent of 1
n
afforded high-molecular-weight polymer (M ≥ 7500) (Table 2,
Entries 1-4, and 7), and the polymer obtained in the initial stage
appeared to have boronic acid moieties at both ends (Figure S12,
S14, S17, and S20), although the polymer formed from 1g and 5
did not show any peaks in the MALDI-TOF mass spectrum. In
contrast to these cases, polycondensation using 1e and 1f, which
induced intermolecular catalyst transfer in the reaction with 2
and 1.0 equivalent of phenylenedibronic acid 5 in the presence of
t
3
Bu PPd G2 precatalyst (Scheme 2, Table 2). Intramolecular
catalyst transfer on 1 is expected to afford high-molecular-weight
polymer with boronic acid moieties at both ends even if excess 1
is used, as in the case of unstoichiometric Suzuki-Miyaura
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201902044
COMMUNICATION
t
Scheme 3. Effect of diphenyl sulfide additive on Suzuki-Miyaura coupling reaction of 6 with 7 in the presence of Bu
3
PPd.
t
(Table 1), resulted in the formation of low-molecular-weight
In conclusion, we have demonstrated that Bu
3
PPd undergoes
polymer (Entries and 6), probably through normal
5
intramolecular catalyst transfer not only on aromatic rings, but
unstoichiometric polycondensation, in which the polymer ends are
capped with excess monomers.
also through CH
2
, CO, N-R, O, SO
2
located between benzene
t
rings in the Bu
3
PPd-catalyzed Suzuki-Miyaura coupling reaction
It should be noted that the MALDI-TOF mass spectra of the final
products from 1a, c, and d with 5 showed a single series of peaks
due to cyclic polymers (Figure S11, S16, and S19); unfortunately
we could not obtain spectra from the final products of the
reactions of 1b and g with 5. Formation of cyclic polymer in
polycondensation is not unusual under stoichiometric conditions,
whereas unstoichiometric polycondensation generally affords
linear telechelic polymer with the same monomer units at both
ends, irrespective of normal or abnormal reaction.[20] However, we
of dibromo compounds 1 having these functional groups with
arylboronic acid 2. On the other hand, the presence of S and SO
in 1 induced intermolecular catalyst transfer, implying that the soft
lone pair on sulfur traps the soft Pd catalyst during intramolecular
catalyst transfer. Taking advantage of these findings, we
conducted unstoichiometric Suzuki-Miyaura polycondensation of
2 2
1.3 equivalent of 1 bearing CH , CO, N-R, O, and SO groups with
1.0 equivalent of p-phenylenediboroinic acid 5 in the presence of
t
Bu
3
PPd G2 precatalyst, obtaining high-molecular-weight polymer
7500-24900 in spite of the use of excess 1. Furthermore,
the obtained polymers containing CH , N-R, and O linkages
have
found
that
unstoichiometric
Suzuki-Miyaura
with M
n
polycondensation of excess dibromoarylene and 1.0 equivalent of
2
t
arylenediboronic acid (ester) catalyzed by Bu
3
PPd selectively
turned out to be cyclic, based on MALDI-TOF analysis.
Intramolecular catalyst transfer on functional groups should make
it possible to conduct CTCP of AB-type monomers containing
these functional groups, providing access to well-defined
engineering plastics, as well as to block copolymers consisting of
engineering plastics and -conjugated polymers. Further studies
are in progress along this line.
affords cyclic polymer when at least one of the two monomers has
a kinked structure, such as in the case of m-phenylene.[
14]
t
Production of cyclic polymers in similar Bu
3
PPd-catalyzed
polycondensation of 1a, c, and d with 5, which has a p-phenylene
structure, implies that 1a, c, and d act as monomers with kinked
3
structure due to the presence of the sp X groups (CH
O).
2
, N-Bu, and
Table 2. Unstoichiometric Suzuki-Miyaura polycondensation
t
a
of 1 and 5 in the presence of Bu
3
PPd G2 precatalyst.
Acknowledgements
b
M
w n
/M b
Entry
1
M
n
This study was supported by the MEXT-Supported Program for
the Strategic Research Foundation at Private Universities (No.
S1311032), 2013-2018, and by a Grant in Aid (No. 15H03819) for
Scientific Research from the Japan Society for the Promotion of
Science (JSPS).
1
2
3
4
5
6
7
1a
1b
1c
1d
1e
10400
24900
15500
20500
2400
4.37
3.91
5.14
2.69
1.46
1.42
4.14
Keywords: catalyst transfer • Suzuki-Miyaura coupling reaction •
Pd catalyst • unstoichiometric polycondensation • cyclic polymer
[
[
1]
2]
R. Martin, S. L. Buchwald, Acc. Chem. Res. 2008, 41, 1461-1473.
P. Ruiz-Castillo, S. L. Buchwald, Chem. Rev. 2016, 116, 12564-
12649.
1
f
2960
[3]
M. C. Willis, Angew. Chem. Int. Ed. 2007, 46, 3402-3404.
B. Schlummer, U. Scholz, Adv. Synth. Catal. 2004, 346, 1599-1626.
A. Yokoyama, R. Miyakoshi, T. Yokozawa, Macromolecules 2004,
37, 1169-1171.
[
[
4]
5]
1g
7500
[
6]
E. E. Sheina, J. S. Liu, M. C. Iovu, D. W. Laird, R. D. McCullough,
Macromolecules 2004, 37, 3526-3528.
a
Polymerization of 1.3 equivalent of 1 and 1.0 equivalent of 5
t
[7]
8]
[9]
A. Yokoyama, H. Suzuki, Y. Kubota, K. Ohuchi, H. Higashimura, T.
Yokozawa, J. Am. Chem. Soc. 2007, 129, 7236-7237.
R. Miyakoshi, A. Yokoyama, T. Yokozawa, J. Am. Chem. Soc. 2005,
127, 17542-17547.
a) T. Yokozawa, Y. Ohta, in Semiconducting Polymers: Controlled
Synthesis and Microstructure, The Royal Society of Chemistry,
was carried out with Bu
of CsF (4.0 equivalent) and 18-crown-6 (8.0 equivalent) in
THF ([5] = 16.6 mM) and H O (THF/H O = 3.0/0.1) at room
temperature for 24 h. Estimated by GPC based on
polystyrene standards (eluent: CHCl ).
3
PPd G2 precatalyst in the presence
[
0
2
2
b
3
2017, pp. 1-37; b) T. Yokozawa, Y. Ohta, Chem. Rev. 2016, 116,
1950-1968.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201902044
COMMUNICATION
[
10]
Y. Geng, A. Sui, in Semiconducting Polymers: Controlled Synthesis
and Microstructure, The Royal Society of Chemistry, 2017, pp. 85-
[15]
[16]
[17]
M. Nojima, Y. Ohta, T. Yokozawa, J. Am. Chem. Soc. 2015, 137,
5682-5685.
T. Kamigawara, H. Sugita, K. Mikami, Y. Ohta, T. Yokozawa,
Catalysts 2017, 7, 195.
S. Wu, Y. Sun, L. Huang, J. Wang, Y. Zhou, Y. Geng, F. Wang,
Macromolecules 2010, 43, 4438-4440.
R. Grisorio, G. P. Suranna, Polym. Chem. 2019, 10, 1947-1955.
It was confirmed that the reaction of 4e with 2 proceeded much
slower than the reaction of 1e with 2 in the reaction of 1e with 2
equivalent of 2 (Supporting Information 4-10, Table S3).
H. R. Kricheldorf, M. G. Zolotukhin, J. Cárdenas, Macromol. Rapid
Commun. 2012, 33, 1814-1832.
1
20.
a) S. Kang, R. J. Ono, C. W. Bielawski, J. Am. Chem. Soc. 2013,
35, 4984-4987; b) Y. Qiu, J. Mohin, C.-H. Tsai, S. Tristram-Nagle,
[
11]
1
R. R. Gil, T. Kowalewski, K. J. T. Noonan, Macromol. Rapid
Commun. 2015, 36, 840-844.
K. Fuji, S. Tamba, K. Shono, A. Sugie, A. Mori, J. Am. Chem. Soc.
[18]
[19]
[
[
12]
13]
2013, 135, 12208-12211.
a) M. Nojima, K. Kosaka, M. Kato, Y. Ohta, T. Yokozawa, Macromol.
Rapid Commun. 2016, 37, 79-85; b) K. Kosaka, K. Nanjyo, Y. Ohta,
T. Yokozawa, Chem. Lett. 2018, 47, 1040-1043.
[20]
[
14]
a) H. Sugita, M. Nojima, Y. Ohta, T. Yokozawa, Chem. Commun.
2017, 53, 396-399; b) H. Sugita, M. Nojima, Y. Ohta, T. Yokozawa,
Polym. Chem. 2019, 10, 1182-1185.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201902044
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
Layout 1:
COMMUNICATION
tBu
catalyst transfer not only on aromatic
rings, but also through CH , CO, N-R,
PPd undergoes intramolecular
Tsutomu Yokozawa*, Natsumi Harada,
Hajime Sugita, Yoshihiro Ohta
3
2
O, SO
rings in the Bu
2
located between benzene
Page No. – Page No.
t
3
PPd-catalyzed Suzuki-
Intramolecular Catalyst Transfer on a
Variety of Functional Groups between
Benzene Rings in Suzuki-Miyaura
Coupling Reaction
Miyaura coupling reaction of dibromo
compounds having these functional
groups with arylboronic acid. On the
other hand, the presence of S and SO
in the dibromides induced
intermolecular catalyst transfer.
Layout 2:
COMMUNICATION
Author(s), Corresponding Author(s)*
((Insert TOC Graphic here))
Page No. – Page No.
Title
Text for Table of Contents
This article is protected by copyright. All rights reserved.