Indazolium halides as efficient ligands for Pd-catalyzed Suzuki–Miyaura cross-coupling of aryl bromides with arylboronic acids

Article abstract of DOI:10.1016/j.tetlet.2016.07.009

The indazolium halides containing various N-substituents have been conveniently prepared and applied in the palladium-catalyzed Suzuki–Miyaura cross-coupling reactions of aryl bromides with arylboronic acids at mild reaction conditions. The cross-coupling reaction provides the desired products in good to high yields. The ease of synthesis and the modularity, and the broad range of aryl bromides and arylboronic acids make this type of ligand attractive and promising for transition metal catalysis.

Full text of DOI:10.1016/j.tetlet.2016.07.009

Accepted Manuscript
Indazoliums Halide as Efficient Ligands for Pd-catalyzed Suzuki–Miyaura
Cross-Coupling of Aryl Bromides with Arylboronic Acids
Qian Chen, Zhuqing Mao, Fang Guo, Xiaoshuang Liu
PII:
S0040-4039(16)30830-9
DOI:
http://dx.doi.org/10.1016/j.tetlet.2016.07.009
TETL 47871
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
23 May 2016
29 June 2016
2 July 2016
Please cite this article as: Chen, Q., Mao, Z., Guo, F., Liu, X., Indazoliums Halide as Efficient Ligands for Pd-
catalyzed Suzuki–Miyaura Cross-Coupling of Aryl Bromides with Arylboronic Acids, Tetrahedron Letters (2016),
doi: http://dx.doi.org/10.1016/j.tetlet.2016.07.009
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Indazoliums Halide as Efficient Ligands for
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Qian Chen, Zhuqing Mao, Fang Guo, Xiaoshuang Liu

1
Tetrahedron Letters
Indazoliums Halide as Efficient Ligands for Pd-catalyzed Suzuki–Miyaura Cross-
Coupling of Aryl Bromides with Arylboronic Acids
Qian Chena, Zhuqing Maoa, Fang Guoa , Xiaoshuang Liua
a MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, State Key Laboratory of Urban Water Resource and
Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150080, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
The indazoliums halide containing various N-substituents have been conveniently prepared and
applied in the palladium-catalyzed Suzuki–Miyaura cross-coupling reactions of aryl bromides
with arylboronic acids at mild reaction conditions. The cross-coupling reaction provides the
desired products in good to high yields. The ease of synthesis and the modularity, and the broad
range of aryl bromides and arylboronic acids make this type of ligand attractive and promising
for transition metal catalysis.
Available online
Keywords:
2009 Elsevier Ltd. All rights reserved.
Indazoliums halide
Palladium-catalysis
Suzuki-Miyaura coupling
Aryl bromide
Aryl boronic acids.
10
Biaryls are important structural motifs and have a high status in
the field of fine chemicals, pharmaceuticals and material science.
Cross-coupling of arylmetal reagents with aryl halides is a
and/or N-substituents.
It was believed that NHCs ligands,
whose carbene center is adjacent to only one heteroatom, tend to
be more electron-donating.
1
11, 12
Indazolin-3-ylidenes belong to
fundamentally important process and represents one of the most
straightforward ways to access biaryls in high yields. 2 Among
them, owing to high functional-group tolerance, and the
availability of nontoxic and stable arylboronic acid, palladium-
catalyzed Suzuki–Miyaura cross-coupling reaction of aryl
halides with arylboronic acids under the mild reaction conditions
has been most extensively investigated.3 The exploitation of
phosphorus-based ligands has given us a distinct impression, and
particularly, various sterically bulky and electron-rich tertiary
phosphines ligands are recognized as efficient ligands for the
Suzuki–Miyaura cross-coupling.4 Despite the recent advances in
this field, it will be a lasting topic of great interest in the Suzuki–
Miyaura cross-coupling for the design and application of novel
ligands since tedious synthetic procedures are required for some
tertiary alkyl phosphine ligands which are usually sensitive to
oxygen.
this class of NHCs, and are regarded as “abnormal” NHCs.
Several indazolin-3-ylidenes were synthesized and their
13
coordination chemistry was investigated.
Accordingly, their
14
reactivity and utility as ligands were also examined.
Even
though the analog of indazolin-3-ylidene, pyrazolin-4-ylidenes,
could be used as mixture ligands with PPh3 or pyridine for
15
palladium-catalyzed Suzuki-Miyaura cross-coupling,
the
efficiency of indazolin-3-ylidene as ligand in palladium-
catalyzed Suzuki-Miyaura cross-coupling has not been reported.
In this regard, it occurs to us that we should examine the
efficiency of indazolium as sole ligand for palladium-catalyzed
Suzuki–Miyaura cross-coupling by fine-tuning of N-substituents
of NHCs.
Here in we report the synthesis of the indazoliums halide with
various N-substituents and their application in palladium
catalyzed Suzuki–Miyaura cross-coupling of aryl bromides with
arylboronic acids.
On another hand, the discovery of stable carbenes, especially
N-heterocyclic carbenes (NHCs), has enriched the chemistry of
The synthesis of the indazoliums halide is shown in Scheme
1.16 Alkylation of indazole 1 was completed by deprotonation
with NaH and subsequently treatment with alkyl halides to give
two regioisomeric products 2 and 2’, which can be readily
purified though column chromatography. Indazoliums halide 3
can be obtained by heating the mixture of 2 or 2’ and alkyl
halides under solvent-free condition and subsequent washing
with hexane for several times. It should note that the modularity
5
6
carbene.
Both of organometallic chemistry
and
7
organocatalysis have greatly benefited from the chemistry of
carbene. In fact, NHCs have been widely utilized as alternatives
to phosphine ligands for transition metal-catalyzed reactions due
to their strong -donating ability resembling phosphines, while
having high stability toward oxygen and moisture.8,9 Further
more, the electronic properties of NHCs can be readily fine-
———
tuned through variation of the backbone of N-heterocycles
 Corresponding author. e-mail: chenqian@hit.edu.cn

2
of indazoliums halide can be fast realized by using this two-steps
procedure.
indazoliums halide (Table 1, entries 1–5). The indazoliums
halide with one aryl group containing electron-donating
substituted group were also good ligands for the present cross-
coupling, affording the desired product in high yields (Table 1,
entries 6 and 8). However, indazolium bromide 3g showed a
decrease in catalytic activity to some extent (entry 7). A
significant decrease in catalytic activity was observed in the
absence of the indazolium salt, which indicated the essential
role of indazolium salt (entry 9). Several palladium sources
were examined. Pd(CF3CO2)2 showed similar catalytic activity,
while moderate yield was observed when Pd(OAc)2 was replaced
by PdCl2 and Pd2(dba)3 to give the coupling products in 65% and
64% yields, respectively (Table 1, entries 10-12).
Scheme 1. Synthesis of indazoliums halide
With indazoliums halide 3a-3h in hand, the Pd-catalyzed
coupling reaction of 1-bromo-4-tert-butylbenzene 4a with o-
tolylboronic acid 5a in toluene at 70 ℃ was examined as the
model reaction to evaluate their efficiency in transition metal
catalysis. It was found that N-substituent of indazoliums halide
has a little influence on the catalytic activity. The indazoliums
halide bearing two alkyl groups showed similar catalytic
activities regardless of the steric hindrance of N-substituent of
Table 1 Optimization of the reaction conditions
Entry a
Yield b (%)
Base
Pd (mol%)
Ligand (mol%)
Solvent
1
2
3
4
5
6
7
8
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(TFA)2 (2)
PdCl2 (2)
Pd2(dba)3(1)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (2)
Pd(OAc)2 (1)
Pd(OAc)2 (0.5)
3a (2.4)
3b (2.4)
3c (2.4)
3d (2.4)
3e (2.4)
3f (2.4)
3g (2.4)
3h (2.4)
-
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (2.4)
3a (1.2)
3a (0.6)
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Dioxane
THF
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K2CO3
Na2CO3
K3PO4
97
90
92
95
96
93
81
92
15
98
64
64
97
33
52
81
67
32
98
97
97
38
75
95
90
70
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23 c
24 d
25 e
26 f
DMF
Toluene/H2O(2:1)
Toluene/H2O(1:1)
H2O
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Et3N
K2CO3
K2CO3
K2CO3
K2CO3
[a] Reaction condition: 1-bromo-4-tert-butylbenzene 4a (0.3 mmol), o-tolylboronic acid 5a (0.45 mmol), Pd (2 mol%),
ligand (2.4 mol%), base (0.45 mmol), solvent (2 mL) at 70 ℃ under N2 atmosphere for 3 hours.
[b] Isolated yield.
[c] At room temperature for 12 hours.
[d] In the presence of air and used reagents without special treatment.
[e]. 1 mol % Pd(OAc)2 and 1.2 mol % 3a were used for 12 hours.
[f]. In 2 mmol scale, 0.5 mol % Pd(OAc)2 and 0.6 mol % 3a were used for 24 hours.

3
Effects of solvents were examined. Both of toluene and
dioxane proved to be suitable, while DMF and THF led to
moderate results (entries 13–15). It should be note that a
water/organic biphasic solvent system is also suitable for the
present cross-coupling using 3a as ligand. The model cross-
coupling reaction was carried out in toluene/H2O (2/1 and 1/1),
affording the product in 81% and 67% yields, respectively
(entries 16–17). However, pure water showed a sharp decrease in
catalytic activity (entry 18). Considering the convenience of
being free of workup, we prefer to use toluene as solvent.
Investigations into the influence of bases suggested that all of
Cs2CO3, K2CO3, Na2CO3, and K3PO4 are suitable base for the
present cross-coupling reaction beside of Et3N (Table 1, entries
19-22). Although the reaction can be carried out at room
temperature, the desired product can be obtained in 75% yield,
and 20% of 4a was recovered (Table 1, entry 22). It should be
noted that the present catalyst system is robust towards air and
moisture. The cross-coupling reaction in the presence of air and
using reagents and solvent without special treatment occurred
smoothly to give the desired product in high yield (entry 24).
Good yield was observed using 1 mol % catalyst but required
prolonged reaction time, and the reaction could not be finished in
Table 2
24 hours when the amount of the catalyst was further reduced
to 0.5 mol % (Table 1, entries 25 and 26). For the convenience,
we choose the condition of entry 24 as optimal condition.
To determine the scope of this transformation, we
investigated the influence of varying arylboronic acids in the
Suzuki–Miyaura cross-coupling with 2 mol% of the catalyst
using 1-bromo-4-tert-butylbenzene 4a as substrate (Table 2).
The phenylboronic acid was easily converted to give the desired
products in high yield (entry 1). The arylboronic acids bearing
alkyl group(s) at the 4- or 3, 5-position could be easily converted
to give the desired products in excellent yields (entries 2-4). The
arylboronic acids bearing 4-methoxy and 3-methoxy substituents,
the aryl groups of which have electron-donating groups gave the
corresponding product 6 in 96% and 97% yields, respectively
(entries
5 and 6). 4-Chlorophenyl bearing an electron-
withdrawing substituent also gave 6ah in excellent yield (99%)
(entry 7). The coupling of 4a with 2-naphthylboronic acid and 1-
naphthylboronic acid gave the corresponding product 6 in 92%
and 75 % yields, respectively (entries 8 and 9).
The scope of palladium-catalyzed Suzuki-Miyaura cross-coupling.
Entry a
ArB(OH)2
Product
Yield b (%)
ArBr
1
2
3
4
5
6
7
8
9
6ab
6ac
6ad
6ae
6af
6ag
6ah
6ai
92
94
96
95
97
96
98
92
75
5b: Ar = Ph
5c: Ar = 4-MeC6H4
5d: Ar = 4-t-BuC6H4
5e: Ar = 3,5-Me2C6H3
5f: Ar = 4-MeOC6H4
5g: Ar = 3-MeOC6H4
5h: Ar = 4-ClC6H4
5i: Ar = 2-Naph
6aj
5j: Ar = 1-Naph
6ba
6bb
6bc
6bd = 6af
6be
6bf
6bg
6bh
98
94
87
86
96
92
79
78
5a: Ar = 2-MeC6H4
5b: Ar = Ph
10
11
12
13
14
15
16
17
5c: Ar = 4-MeC6H4
5d: Ar = 4-t-BuC6H4
5e: Ar = 3,5-Me2C6H3
5f: Ar = 4-MeOC6H4
5g: Ar = 3-MeOC6H4
5h: Ar = 4-ClC6H4
6ca
6cf = 6bh
6ch
91
78
91
5a: Ar = 2-MeC6H4
5f: Ar = 4-MeOC6H4
5h: Ar = 4-ClC6H4
18
19
20
5b: Ar = Ph
5f: Ar = 4-MeOC6H4
5h: Ar = 4-ClC6H4
21
22
23
6db
6df
6dh
81
80
78
5b: Ar = Ph
5b: Ar = Ph
5b: Ar = Ph
5b: Ar = Ph
24
25
26
27
6eb
6fb
85
91
6gb
6hb
92
trace

4
[a] Reaction condition: ArBr 4 (0.3 mmol), arylboronic acid 5 (0.45 mmol), Pd (2 mol%), ligand 3a (2.4 mol%), K CO (0.45 mmol),
2
3
toluene (2 mL) at 70 ℃ in the presence of air and used reagents without special treatment for 3 hours.
[b] Isolated yield.
[c] 2 equiv. 5f was used.
Angew. Chem. Int. Ed.1998, 37, 3387-3388.
Further investigations shown that the broad substrate of the
Suzuki–Miyaura cross-coupling was observed (Table 2). Various
aryl bromides and aryl boronic acids could be applied in this
transformation. 4-Bromoanisole containing electron-donating
group on the aromatic was smoothly coupled with substituted
arylboronic acids to afford the biaryl products in good to
excellent yields (entries 10-17). The aryl bromides having
electron-withdrawing groups, for example, 1-bromo-4-
chlorobenzene, methyl 4-bromobenzoate, 2-bromobenzonitrile,
were efficiently coupled with substituted arylboronic acids,
giving good to high yields (entries 18–24). 2-bromonaphthalene
could smoothly react with phenylboronic acid, giving the desired
products in good yield (entry 25). Heteroaryl bromide containing
5. (a) Bourissou, D.; Guerret, O.; Gabbaϊ, F. P.; Bertrand, G. Chem. Rev. 2000,
100, 39-92; (b) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1290-1309;
(c) César, V.; Bellemin-Laponnaz, S.; Gade, L. H. Chem. Soc. Rev. 2004, 33,
619-636; (d) M. N. Hopkinson, C.Richter, M. Schedler, F. Glorius, Nature
2014, 510, 485-496.
6. (a) Díez-González, S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109, 3612-
3676; (b) Fortman, G. C.; Nolan, S. P. Chem. Soc. Rev. 2011, 40, 5151-5169.
7. Enders, D.; Niemeier, O.; Henseler, A. Chem. Rev. 2007,107, 5606-5655.
8. For selected examples of NHCs as ligand for Suzuki-Miyaura coupling, see: (a)
Sellmann, D.; Prechtel, W.; Knoch, F.; Moll, M. Organometallics 1992, 11,
2346-2348; (b) Gstöttmayr, C. W. K. Böhm, V. P. W.; Herdweck, E.; Grosche,
M.; Herrmann, W. A. Angew. Chem. Int. Ed. 2002, 41, 1363-1365; (c) César,
V.; Bellemin-Laponnaz, S.; Gade, L. H. Organometallics 2002, 21, 5204-5208;
(d) Altenhoff, G.; Goddard, R.; Lehmann, C. W.; Glorius, F. Angew. Chem., Int.
Ed. 2003, 42, 3690-3693; (e) Lebel, H.; Janes, M. K.; Charette, A. B.; Nolan, S.
P. J. Am. Chem. Soc. 2004, 126, 5046-5047; (f) Wang, A.-E.; Zhong, J.; Xie, J.-
H.; Li, K.; Zhou, Q.-L. Adv. Synth. Catal. 2004, 346, 595–598; (g) Zeng, F.;
Yu, A. J. Org. Chem. 2006, 71, 5274-5281; (h) Kuriyama,M.; Shimazawa,R.;
Shirai, R. Tetrahedron 2007, 63, 9393-9400; (i) Zhong, R.; Wang, Y.-N.; Guo,
X.-Q.; Hou, X.-F. J. Organomet. Chem. 2011, 696, 1703-1707; (j) Mao,
P.;Yang, L.;Xiao, Y.;Yuan, J.;Liu, X.;Song, M. J. Organomet. Chem. 2012,
705, 39-46; (k) Chen, X.;Ke, H.;Chen, Y.;Guan, C.;Zou, G. J. Org. Chem.
2012, 77, 7572-7578.
9. For selected examples of NHCs as ligand for Heck reaction, see: (a) Yang, C.;
Lee, H. M.; Nolan, S. P. Org. Lett. 2001, 3, 1511-1514; (b) Tsoureas, N.;
Danopoulos, A. A.; Tulloch, A. A. D.; Light, M. E. Organometallics 2003, 22,
4750-4758; (c) Wang, R.; Twamley, B.; Shreeve, J. M. J. Org. Chem. 2006, 71,
426-429;
10. Nelson, D. J.; Nolan, S. P. Chem. Soc. Rev. 2013, 42, 6723-6753.
11. For reviews, see: (a) Schuster, O.; Yang, L.; Raubenheimer, H. G.; Albrecht, M.
Chem. Rev., 2009, 109, 3445-3478; (b) Soleilhavoup, M.; Bertrand, G. Acc.
Chem. Res. 2015, 48, 256-266.
12. For selected examples: (a) Lavallo, V.; Canac, Y.; Präsang, C.; Donnadieu, B.;
Bertrand, G. Angew. Chem. Int. Ed. 2005, 44, 5705-5709; (b) Jazzar, R.;
Dewhurst, R. D.; Bourg, J. B.; Donnadieu, B.; Canac, Y.; Bertrand, G. Angew.
Chem. Int. Ed. 2007, 46, 2899-2902; (c) Rao, B.; Tang, H.; Zeng, X.; Liu, L.;
Melaimi, M.; Bertrand, G. Angew. Chem. Int. Ed. 2015, 54, 14915-14919.
13. (a) Jothibasu, R.; Huynh, H. V. Chem. Commun. 2010, 46, 2986-2988; (b)
Sivaram, H.; Jothibasu, R.; Huynh, H. V. Organometallics 2012, 31, 31, 1195-
1203.
14. (a) Han, Y.; Yuan, D.; Teng, Q.; Huynh, H. V. Organometallics 2011, 30,
1224-1230; (b) Zhou, Y.; Liu, Q.; Lv, W.; Pang, Q.; Ben, R.; Qian, Y.; Zhao, J.
Organometallics 2013, 32, 32, 3753−3759; (c) Bernhammer, J. C.; Chong, N.;
Jothibasu, R.; Zhou, B.; Huynh, H. V. Organometallics 2014, 33, 3607-3617; (d)
Bernhammer, J. C.; Singh, H.; Huynh, H. V. Organometallics 2014, 33, 4295-
4301.
a coordinating atom, 2-bromopyridine led to 92% yield (entry
17
26).
Unfortunately, the coupling of 4-chlorobenzophenone
with phenylboronic acid gave trace of product (entry 27).
However, because the C-OMe and C-Cl bonds (Table 3, entries
10-20) can be readily cleaved by nickel catalysis, and therefore
provides the opportunity for further cross-coupling reactions
with different functionalities. 18
In summary, the indazoliums halide bearing various N-
substituents were prepared and their application in palladium
catalyzed Suzuki–Miyaura cross-coupling reactions of aryl
bromides with arylboronic acids was investigated. The cross-
coupling products of a broad range of aryl bromides with various
arylboronic acids could be obtained in good to high yields. This
initial investigation revealed that the indazoliums halide could be
used as a class of promising and sole ligands for Suzuki–
Miyaura cross-coupling reactions. The ease of synthesis and the
modularity make this type of ligand attractive and promising for
transition metal catalysis. Chiral indazoliums halide and further
application to other transition metal-catalyzed transformations
are currently under investigation.
Acknowledgments
We are grateful for the financial support of SKLUWRE
(No.2014TS04), “the Fundamental Research Funds for the
Central Universities” (Grant No. HIT. IBRSEM.A.201404), the
Natural Science Foundation of China (NSFC No. 20902015).
15. (a) Han, Y.; Huynh, H. V.; Tan, G. K. Organometallics 2007, 26, 6581-6585; (b)
Han, Y.; Lee, L. J.; Huynh, H. V. Organometallics 2009, 28, 2778-2786.
16. See the ESI for details. N-aryl indazole can be prepared according the reported
procedure. For 2-aryl-2H-indazole 2’ was prepared according the reported
procedure: J. I. G. Cadogan, R. K. Mackie. Org. Syn. 1973, Coll. Vol. 5, 941.
For 1-aryl-1H-indazole 2 was prepared according the reported procedure:
Phillips, D. P.; Zhu, X.-F.; Lau, T. L.; He, X.; Yang, K.; Liu, H. Tetrahedron Lett.
2009, 50, 7293-7296.
Supplementary data
Supplementary data related to this article can be found at
References and notes
17. Billingsley, K. L.; Anderson, K. W.; Buchwald, S. L. Angew. Chem. Int. Ed.
2006, 45, 3484-3488
18. Amii, H.; Uneyama, K. Chem. Rev. 2010, 110, 2119-2183, and reference
therein.
1. (a) Hassan, J.; Sévignon, M.; Gozzi, C.; Schulz, E.; Lemaire, M. Chem. Rev.
2002, 102, 1359-1470; (b) Torborg, C.; Beller, M. Adv. Synth. Catal. 2009, 351,
3027-3043.
2. (a) Metal-Catalyzed Cross-Coupling Reactions, Vol. 2 (Eds.: Meijere, A. De.;
Diederich, F.), Wiley-VCH, Weinheim, 2004; (b) Magano, J.; Dunetz, J. R.
Chem. Rev. 2011, 111, 2177-2250.
3. (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457-2483; (b) Miyaura, N.
Top. Curr. Chem. 2002, 219, 11-59; (c) Molander, G. A.; Canturk, B. Angew.
Chem. Int. Ed. 2009, 48, 9240-9261.
Click here to remove instruction text...
4. For example: (a) Walker, S. D.; Barder, T. E.; Martinelli, J. R.; Buchwald, S. L.
Angew. Chem. Int. Ed. 2004, 43, 1871-1876; (b) Zapf, A.; Ehrentraut, A.; Beller,
M. Angew. Chem. Int. Ed. 2000, 39, 4153-4155; (c) Littke, A. F.; Fu, G. C.

5
Highlights:
Indazoliums halide bearing various N-substituents were readily synthesized.
The indazoliums halide can be used as sole ligand for Pd-catalyzed Suzuki coupling.
The coupling products were obtained at mild reaction conditions in high yields.
A broad range of substrate scope was observed.