Application of zwitterionic phosphapalladacycles in aqueous phase Suzuki-Miyaura coupling

Article abstract of DOI:10.1080/10426507.2018.1543301

The catalytic application of novel six-membered zwitterionic palladacycles with formal negative charge on the metal center and positive charge on the ancillary ligand is reported in the aqueous phase Suzuki-Miyaura coupling. The novel catalysts provide excellent activities with high functional group tolerance in the carbon-carbon bond forming reaction yielding substituted biaryls in high yields.

Full text of DOI:10.1080/10426507.2018.1543301

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: http://www.tandfonline.com/loi/gpss20
Application of zwitterionic phosphapalladacycles
in aqueous phase Suzuki-Miyaura coupling
László Szi-Ferenc, Zsófia Császár, Attila Bényei, József Bakos & Gergely
Farkas
To cite this article: László Szi-Ferenc, Zsófia Császár, Attila Bényei, József Bakos &
Gergely Farkas (2018): Application of zwitterionic phosphapalladacycles in aqueous phase
Suzuki-Miyaura coupling, Phosphorus, Sulfur, and Silicon and the Related Elements, DOI:
10.1080/10426507.2018.1543301
To link to this article: https://doi.org/10.1080/10426507.2018.1543301
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PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
https://doi.org/10.1080/10426507.2018.1543301
Application of zwitterionic phosphapalladacycles in aqueous phase Suzuki-
Miyaura coupling
a
a
b
a
a
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ꢀ
ꢀ
ꢀ ꢀ
ꢀ
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Laszlo Szi-Ferenc , Zsofia Csaszar , Attila Benyei , Jozsef Bakos , and Gergely Farkas
a
b
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Department of Organic Chemistry, University of Pannonia, Veszprem, Hungary; Department of Pharmaceutical Chemistry, University of
Debrecen, Debrecen, Hungary
ABSTRACT
ARTICLE HISTORY
Received 30 September 2018
Accepted 27 October 2018
The catalytic application of novel six-membered zwitterionic palladacycles with formal negative
charge on the metal center and positive charge on the ancillary ligand is reported in the aqueous
phase Suzuki-Miyaura coupling. The novel catalysts provide excellent activities with high functional
group tolerance in the carbon-carbon bond forming reaction yielding substituted biaryls in
high yields.
KEYWORDS
Suzuki-Miyaura coupling;
aqueous-phase; zwitterionic;
palladacycle
GRAPHICAL ABSTRACT
1. Results and discussion
Table 1. Application of zwitterionic complexes 1a–e in aqueous phase SM-
coupling of phenyl-boronic acid with aryl- and aralkyl-halides.
Recently, we have reported on the synthesis of a new type of
zwitterionic phosphapalladacycles with reversed polarity, i.e.
with formal negative charge on the metal center and positive
charge on the ancillary ligand (Scheme 1).[1] These type of
metallacycles may have unique catalytic features as they are
able to accelerate oxidative addition owing to the electron
rich metalate moiety. In order to prove this assumption we
have applied palladacycles 1a–e in the aqueous phase
Suzuki-Miyaura (SM) coupling of phenylboronic acid and
several aryl halides.
Reaction
time [h]
Isolated
yield [%]
Entry
Complex
Halogenide
Base
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1a
4-MeO-C6H4Br
K3PO4
1
72
65
67
58
68
86
75
4
61
82
96
82
87
99
92
99
99
91
90
50
4-MeO-C6H4Br
KOH
K2CO3
K3PO4
1
1a
1a
4-MeO-C6H4Cl
4-MeO-C6H4I
C6H5Br
4-MeO-C6H4Br
4-Me-C6H4Br
4-tBu-C6H4Br
4-OHC-C6H4Br
4-F3C-C6H4Br
1-Br-naphthalene
2-Cl-C6H4Br
24
0.5
24
9
10
11
12
13
14
15
16
17
18
19
20
K3PO4
The catalytic experiments were performed in a 1:1 mix-
ture of water and ethanol in the presence of 0.4% catalyst at
4-Cl-C6H4Br
1,3,5-Br3-benzene
benzyl-bromide
Reaction conditions: phenylboronic acid: 0.6 mmol; halogenide: 0.5 mmol; com-
plex: 0.002 mmol; base: 1 mmol; solvent: 4 mL of EtOH/H2O 1:1, tempera-
ture: RT.
room temperature. According to the data shown in Table 1,
the best activity could be obtained by complex 1a (entries
1–5) when 4-bromoanisole was used as the halogenide.
Scheme 1. Zwitterionic phosphapalladacycles synthesized by the CH-activation
of chiral P,N-ligands.
ꢀ
ꢀ
Department of Organic Chemistry, University of Pannonia, Egyetem u. 10, Veszprem H-
CONTACT Jozsef Bakos
bakos@almos.uni-pannon.hu
8200, Hungary.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gpss.
Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/10426507.2018.1543301.
ß 2018 Taylor & Francis Group, LLC

2
L. SZI-FERENC ET AL.
In the next set of experiments the role of the base metal ensure high activity and functional group tolerance in
(entries 6 and 7) and the structure of the aryl halides room temperature SM-coupling reactions using aqueous
(entries 8–20) were investigated in a mixture of green sol-
vents. Although the highest yields could be obtained by the
use of KOH as the strongest base applied, (entry 6) the
environmentally more benign K3PO4 was used in the next
experiments. It has been shown that the zwitterionic palla-
reaction media. Moreover, the catalysts may have applied in
asymmetric SM-reactions as they can be synthesized in an
optically pure form.
dates are active and selective catalysts for the SM reactions References
of aryl-bromides and iodides. Additionally, benzyl-bromide
[1] Szi-Ferenc, L.; Csꢀaszꢀar, Z.; Lendvay, G.; Bꢀenyei, A.; Balogh, S.;
could be transformed to diphenyl-methane in 50% yield
(entry 20). Based on our results, it is clearly demonstrated
that complexes 1a–e with formal negative charge on the
ꢀ ꢀ
Nanasi, B.; Farkas, G.; Bakos, J. Synthesis of Zwitterionic
Phosphapalladacycles: Unusual Reactivity Pattern of Six-
Membered P,N-Chelates. Organometallics 2018, 37, 2203–2206.