A four-coordinate Cu(I)–N-heterocyclic carbene complex: Synthesis, structure, properties, and application in amination for the synthesis of 1-(2-N-heteroaryl)-1H-pyrazoles

Article abstract of DOI:10.1177/1747519820921819

A new luminescent, cationic, heteroleptic, four-coordinate Cu(I)–N-heterocyclic carbene complex [Cu(Br-Pyim)(POP)](PF₆) is successfully prepared and characterized, where Br-Pyim and POP are 1-(6-bromopyridin-2-yl)imidazole-3-benzyl-2-ylidene an

Full text of DOI:10.1177/1747519820921819

9
research-arti
2cle2020 1819CHL0010.1177/1747519820921819Journal of Chemical ResearchXu et al.
Research Paper
Journal of Chemical Research
–6
1
A four-coordinate Cu(I)–N-heterocyclic
carbene complex: Synthesis, structure,
properties, and application in amination
for the synthesis of 1-(2-N-heteroaryl)-
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1H-pyrazoles
Chen Xu1 , Hong-Mei Li , Zhi-Qiang Wang and Wei-Jun Fu
1
2
2
Abstract
A new luminescent, cationic, heteroleptic, four-coordinate Cu(I)–N-heterocyclic carbene complex [Cu(Br-Pyim)(POP)]
(
PF ) is successfully prepared and characterized, where Br-Pyim and POP are 1-(6-bromopyridin-2-yl)imidazole-3-benzyl-
6
2-ylidene and bis[2-(diphenylphosphino)phenyl]ether, respectively. Its detailed structure is determined by single-crystal
X-ray analysis. It exists as a crystalline powder at room temperature and exhibits bright yellow-green emission. The
use of the Cu(I)–N-heterocyclic carbene complex as a catalyst for amination reactions is also investigated and is found
to be very efficient for the amination of 2-N-heteroaryl chlorides with pyrazoles, giving the desired substituted 1-(2-N-
heteroaryl)-1H-pyrazoles in good yields.
Keywords
amination, copper-catalyzed, Cu(I)–N-heterocyclic carbene complex, N-arylpyrazole
Date received: 19 January 2020; accepted: 6 April 2020
R
R
R'
X
X
N
X
X
N
R'
Cat Cu
Cl
HN
N
N
N
R
R
X = C, N; R = H, CH3
Cat Cu
materials science.10–13 Recently, Thompson’s group reported
Introduction
luminescent Cu(I)−NHC complexes, and these complexes
N-Arylpyrazoles are important intermediates used in the syn-
14,15
exhibited moderate-to-high emission efficiency.
We have
thesis of many agrochemicals, pharmaceuticals, and func-
also reported several cationic, heteroleptic, four-coordinate
1,2
tional materials. The N-arylpyrazole structural unit can be
obtained by several synthetic methods, among which transi-
tion-metal-catalyzed amination of aryl halides is one of the
1School of Environmental and Chemical Engineering, Jiangsu University
of Science and Technology, Zhenjiang, P.R. China
3–5
most direct and powerful. In contrast to expensive cata-
lysts such as palladium and rhodium complexes, low-cost
copper catalysts are attracting considerable attention due to
their potential use in industrial and practical applications.
Many copper/ligand systems have been reported, most of
which utilize CuI as the catalyst and other Cu sources (e.g.
2
College of Chemistry and Chemical Engineering, Luoyang Normal
University, Luoyang, P.R. China
6–9
Corresponding authors:
Chen Xu, School of Environmental and Chemical Engineering, Jiangsu
University of Science and Technology, Zhenjiang Mengxi Road 3,
Cu O, CuCl). However, the copper/ligand catalytic processes Zhenjiang 212003, P.R. China.
2
Email: chenxu@just.edu.cn
have not been well-determined; in particular, the structures
of the Cu(I) pre-catalysts are rarely investigated.
It is well-known that N-heterocyclic carbenes (NHCs)
have strong σ-donating and modest π-accepting abilities,
8,9
Zhi-Qiang Wang, College of Chemistry and Chemical Engineering,
Luoyang Normal University, Longmeng Road 72, Luoyang 471022,
Henan, P.R. China.
which make them widely used as ligands in catalysis and Email: wzq197811@163.com

2
Journal of Chemical Research 00(0)
Br
Br
Ph
Ph
Ph
Ph
P
P
N
N
Cu
N
Cu
O
N
O
N
N
P
P
-
PF
6
PF -
Ph Ph
Ph Ph
6
Ph
Ph
1
(
POP)
Scheme 1. Synthesis of four-coordinate Cu(I)–NHC complex 1.
Cu(I)−NHC complexes with high emission efficiency and
tunable emission wavelengths by modifying the structure of
16,17
NHC ligands.
In view of these findings and our continu-
ing interest in the synthesis of NHC complexes as well as
18,19
their application in coupling reactions,
we were inter-
ested to investigate whether the obtained Cu(I)–NHC com-
plexes were active for aminations. Thus, we prepared a new
photoluminescence Cu(I)–NHC complex and examined its
catalytic activity in the amination of pyrazoles.
Figure 1. X-ray crystal structure of 1. H atoms, CH COCH ,
3
3
Results and discussion
6−
and PF are omitted for clarity. Selected bond lengths (Å) and
angles (°) are as follows: Cu–N1 2.309(3), Cu–C8 1.964(3),
Cu–P1 2.2566(9), Cu–P2 2.2693(10), and N1–Cu–C8 77.55(13),
C8–Cu–P1 122.89(10), P1–Cu–P2 114.41(3), and P2–Cu–N1
Synthesis and structure
The new four-coordinate Cu(I)–NHC complex 1 was pre-
1
21.96(8).
pared using the method reported by our group (Scheme
1
6,17
1
)
and characterized by elemental analysis, mass spec-
1
31
13
troscopy (MS), and H, P, and C NMR spectroscopy. It emission lifetime were measured to be 26% and 76.0μs,
is very stable to air and moisture in a solid state at room respectively. At a low temperature of 77K, the PL peak of 1
temperature. The nuclear magnetic resonance (NMR) spec- appears at 570nm which is red-shifted by about 16nm
trum of 1 was consistent with the proposed structure, and compared to that acquired at 298K. In addition, the emis-
the signal for the carbene carbon atom was observed at sion lifetime was measured to be 231.3μs at 77K, which
58.7ppm in the 13C NMR spectrum. Furthermore, its increased by a factor of 3 compared to that acquired at
1
detailed structure was confirmed by X-ray diffraction anal- 298K (Figure 2, inset). These results imply that emission of
ysis. Single crystals were obtained through slow evapora- this complex at room temperature is thermally activated
tion of an acetone solution at room temperature. The crystal delayed fluorescence (TADF).
structure of 1 is shown in Figure. 1. The Cu in the complex
is in a typical distorted tetrahedral environment and is
bonded to two P atoms of POP, a C atom, and the N atom of
Amination
the NHC (Br-Pyim) ligand. The imidazolylidene ring and 1-(2-N-Heteroaryl)-1H-pyrazole derivatives as N,N ligands
the pyridine ring of the NHC ligand are nearly coplanar and have found widespread applications in the fields of supramo-
the dihedral angle is 6.4°. The bond lengths of Cu−C, lecular chemistry and crystal engineering. Coupling reac-
Cu−N, and Cu(I)−P are similar to those of reported related tions of N-heteroaryl halides have become one of the most
1
4–17
four-coordinate Cu complexes.
valuable synthetic processes for N-heterocyclic com-
21,22
pounds.
For example, 2-chloro pyridines and 2-chloropy-
rimidines are important coupling partners in these
Absorption and emission
23–25
reactions.
However, the amination of 2-N-heteroaryl hal-
26,27
In CH Cl solution, complex 1 exhibits three absorption ides with pyrazoles has been relatively less reported.
So,
2
2
bands as shown in Figure. 2. The intense high-energy we have investigated the catalytic activity of complex 1 for
absorption bands at 232 and 280nm are ligand-centered the N-arylation of 2-N-heteroaryl chlorides with pyrazoles.
(
3
LC) π-π* transitions. The weaker absorption band at
40nm can be assigned to the charge transfer (CT) transi- coupling reaction of 2-chloro-5-methylpyridine with 1H-
tions, which should include metal-to-ligand charge transfer pyrazole was examined. Using 0.5mol% of 1 in dioxane
Initially, the use of complex 1 as a catalyst for the
(
MLCT) and ligand-to-ligand (LLCT) transitions, accord- at 110°C for 12h provided the desired product 2. The
1
6,17
ing to previous reports.
It does not show luminescence results from this study are summarized in Table 1. After
2
0
t
in organic solutions at room temperature; however, as a screening a variety of bases (entries 1–6), KO Bu was
t
crystalline powder it shows intense yellow-green emission found to give the best result, while NaO Bu gave a moder-
with a photoluminescence (PL) spectrum at 555nm at room ate yield. A survey of solvents indicated that dioxane was
temperature (298K). The absolute PL quantum yield and much better than other solvents such as tetrahydrofuran

Xu et al.
3
Table 2. Aminations of 2-N-heteroaryl chlorides with
a
pyrazoles catalyzed by 1.
R
R
X
N
X
X
N
R'
X
R'
Cat Cu
Cl
HN
N
N
N
R
(b)
R
X = C, N; R = H (a), CH
3
R
N
N
N
N
N
N
R
3
5
, 89%
4a, 92%; 4b, 90%
R
R
N
N
N
N
R
N
N
R
H CO
3
Figure 2. Absorption and photoluminescence (PL) spectra
of 1. The inset is the emission decay behavior of 1 in the solid
state at 298 and 77K.
a, 89%; 5b, 91%
6a, 87%; 6b, 84%
H CO
R
F
3
C
R
3
N
N
Table 1. Optimization of the reaction conditions for the
amination of 2-chloro-5-methylpyridine with 1H-pyrazole.
N
N
R
N
R
N
a
7
a, 85%; 7b, 83%
8a, 91%; 8b, 90%
Cat Cu
R
R
Cl
HN
N
N
N
N
N
2
Cl
F3C
N
N
N
R
N
N
R
N
Entry Base
Solvent Catalyst (mol%)
Yield (%)b
9
a, 96%; 9b, 93%
10a, 93%; 10b, 92%
1
2
3
4
5
6
7
8
9
0
1
2
3
Na CO Dioxane 1 (0.5)
28
42
53
36
75
91
86
49
37
54
2
3
R
N
R
K CO Dioxane 1 (0.5)
N
2
3
KOH
Dioxane 1 (0.5)
Dioxane 1 (0.5)
N
N
K PO
N
N
R
N
N
R
3
4
t
NaO Bu Dioxane 1 (0.5)
11a, 90%; 11b, 87%
12a, 94%; 12b, 91%
t
KO Bu Dioxane 1 (0.5)
a
t
Reaction conditions: 2-N-heteroaryl chloride (1.0mmol), pyrazole
(1.1mmol), 1 (0.5mol%), KO Bu (2.0mmol), dioxane (3mL), 110°C, 12h.
KO Bu Toluene 1 (0.5)
t
t
KO Bu THF
1 (0.5)
1 (0.5)
t
KO Bu DMF
t
1
1
1
1
KO Bu DMSO 1 (0.5)
the coupling of a variety of electronically and structurally
-N-heteroaryl chlorides with pyrazoles catalyzed by com-
t
KO Bu Dioxane CuI (0.5)/Br-HPyimPF (1) 38
6
2
t
KO Bu Dioxane CuI (0.5)/POP (1)
25
72
plex 1 was carried out (Table 2). Products 4a,b were obtained
from 2-chloropyridine in good yields (92% and 90%). For
electron-rich 2-chloropyridine derivatives, the yields of the
coupled products 5 and 6 were 84%–91%. As expected, the
coupling reactions of activated 2-chloropyridine derivatives
gave the products 7–10 in excellent yields (90%–96%).
Finally, we investigated the couplings of 2-chloropyrimi-
dine and 2-chloropyrazine and found them to be efficient
coupling partners in this system giving products 11 and 12
in good yields.
t
KO Bu Dioxane CuI (0.5)/Br-HPyimPF6
(1)/POP (1)
THF: tetrahydrofuran; DMF: dimethylformamide; DMSO: dimethyl
sulfoxide.
Reaction conditions: 2-chloro-5-methylpyridine (1.0mmol), 1H-pyrazole
1.1 mmol), base (2.0mmol), solvent (3mL), 110°C, 12h.
Isolated yield.
a
(
b
(
THF), dimethylformamide (DMF), and dimethyl sulfox-
ide (DMSO) (entries 7–10). Toluene also afforded a good
yield. In addition, CuI/Br-HPyimPF and CuI/POP were
6
poorly active under the same reaction conditions (entries
Conclusion
1
1 and 12). However, CuI/Br-HPyimPF /POP generated
6
the product in a 72% yield, showing a synergistic ligand A new photoluminescent four-coordinate Cu–NHC com-
effect between the NHC and POP ligands in the amination plex has been synthesized and characterized. The complex
2
8–31
(
entry 13).
demonstrates efficient TADF in the solid state at room tem-
Compared with 1H-pyrazole, 3,5-dimethyl-1H-pyrazole perature. In addition, we have developed an efficient
showed no deleterious effect on these reactions. Under the method for the amination of N-heteroaryl chlorides with
optimized reaction conditions, the amination of 3,5-dime- pyrazoles catalyzed by this Cu–NHC complex. This proto-
thyl-1H-pyrazole with 2-chloro-5-methylpyridine gave col provides an efficient access to a variety of substituted
product 3 in a good yield (89%). In subsequent experiments, 1-(2-N-heteroaryl) -1H- pyrazoles.

4
Journal of Chemical Research 00(0)
1
Experimental
5-Methyl-2-(3,5-dimethyl-1H-pyrazol-1-yl)pyridine (3): H
NMR (400MHz, CDCl ): δ 8.26 (s, 1H), 7.70 (d, J=6.8Hz,
H), 7.60 (d, J=6.8Hz, 1H), 5.99 (s, 1H), 2.36 (s, 3H), 2.28
Solvents were dried and freshly distilled prior to use. All (s, 3H), 2.24 (s, 3H). C NMR (100MHz, CDCl ): δ 149.8,
3
Materials and equipment
1
1
3
3
other chemicals were commercially available, expect for 146.1, 139.4, 131.0, 126.9, 112.1, 110.8, 107.6, 29.8, 15.7,
+
1
-(6-bromopyridin-2-yl)-3-benzylimidazolium hexafluoro- 13.8. MS-ESI : m/z=187.1. Anal. Calcd for C H N : C,
1
1
13
3
phosphate (Br-HPyimPF ), which was prepared according 70.6; H, 7.0; N, 22.4. Found: C, 71.0; H, 6.7; N, 22.6%.
6
1
6,17
to the published procedure.
Elemental analyses were
1
determined with a Carlo Erba 1160 Elemental Analyzer. 2-Methoxy-6-(1H-pyrazol-1-yl)pyridine (6a): H NMR
Mass spectra were measured on a LC-MSD-Trap-XCT (400MHz, CDCl ): δ 8.53 (s, 1H), 7.72 (m, 2H), 7.53 (d,
3
1
31
13
instrument. H, P, and C NMR spectra were recorded on J=7.6Hz, 1H), 6.64 (d, J=8.4Hz, 1H), 6.46 (d, J=1.2Hz,
a Bruker DPX-400 spectrometer (400, 162, and 100MHz, 1H), 3.99 (s, 3H). C NMR (100MHz, CDCl ): δ 163.3,
1
3
3
respectively) with tetramethylsilane (TMS) as an internal 149.6, 142.0, 141.1, 127.1, 107.8, 107.4, 103.9, 53.6. MS-
+
standard. The absorption and PL spectra were recorded on ESI : m/z=175.1. Anal. Calcd for C H N O: C, 61.7; H,
9
9
3
a Hitachi U-3010 UV-Vis spectrophotometer and a Hitachi 5.2; N, 24.0. Found: C, 61.9; H, 4.9; N, 24.3%.
F-4500 fluorescence spectrophotometer.
2
-Methoxy-6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridine
1
(
6b): H NMR (400MHz, CDCl ): δ 7.66 (t, J=8.0Hz,
3
Synthesis of [Cu(Br-Pyim)(POP)](PF ) 1
6
1H), 7.42 (d, J=7.7Hz, 1H), 6.59 (d, J=8.0Hz, 1H), 5.99
1
3
Under an N atmosphere, Br-HPyimPF (1mmol), copper (s, 1H), 3.93 (s, 3H), 2.69 (s, 3H), 2.29 (s, 3H). C NMR
2
6
powder (1.2mmol), and bis[2-(diphenylphosphino)phenyl] (100MHz, CDCl ): δ 162.8, 151.6, 149.9, 141.3, 140.7,
3
+
ether (POP, 1mmol) were stirred in CH CN (10mL) at 109.1, 107.1, 107.0, 53.9, 15.0, 13.8. MS-ESI : m/z=203.1.
3
7
0 C overnight. After cooling, the resulting mixture was fil- Anal. Calcd for C H N O: C, 65.0; H, 6.5; N, 20.7. Found:
11 13 3
tered, and then the filtrate was collected and evaporated C, 65.3; H, 6.1; N, 20.9%.
under vacuum. The residue was dissolved in dichlorometh-
ane/ethanol, and the product was obtained as yellow crys- 4-Methoxy-2-(3,5-dimethyl-1H-pyrazol-1-yl)pyridine
1
1
tals by slow evaporation of the solvent. Yield: 63%. H (7b): H NMR (400MHz, CDCl ): δ 8.19 (d, J=6.0Hz, 1H),
3
NMR (400MHz, CD CN): δ 7.76–7.85 (m, 2H), 7.61–7.68 7.36 (s, 1H), 6.68 (t, J=5.6Hz, 1H), 5.98 (s, 1H), 3.90 (s, 3H),
3
13
(
(
m, 1H), 7.34–7.49 (m, 16H), 7.09–7.15 (m, 6H), 7.00–7.04 2.61 (s, 3H), 2.29 (s, 3H). C NMR (100MHz, CDCl ): δ
3
m, 6H), 6.85–6.98 (m, 5H), 6.49–6.52 (s, 2H), 4.55 (s, 167.4, 155.4, 149.7, 141.8, 141.1, 109.0, 107.9, 100.3, 55.5,
1
3
+
2
1
1
H). C NMR (100MHz, CD CN): δ 158.7, 151.6, 143.1, 14.6, 13.7. MS-ESI : m/z=203.1. Anal. Calcd for C H N O:
3
11 13
3
41.7, 136.7, 134.6, 133.0, 131.1, 131.2, 129.8, 129.7, C, 65.0; H, 6.5; N, 20.7. Found: C, 65.4; H, 6.2; N, 21.1%.
3
1
29.6, 128.8, 128.0, 125.9, 125.8, 124.0, 118.3, 55.0.
P
+
1
NMR (162MHz, CD CN): δ −9.9 (s), −144.2 (q). MS-ESI : 4-(Trifluoromethyl)-2-(1H-pyrazol-1-yl)pyridine (8a): H
m/z=914.1(M–PF ) .Anal.CalcdforC H BrCuF N OP : NMR (400MHz, CDCl ): δ 8.64 (s, 1H), 8.20 (d, J=8.3Hz,
3
+
6
51 40
6
3
3
3
C, 57.7; H, 3.8; N, 4.0. Found: C, 57.9; H, 3.5; N, 4.2%.
1H), 7.99 (t, J=7.7Hz, 1H), 7.78 (s, 1H), 7.56 (d, J=7.5Hz,
1
3
1
H), 6.51 (d, J=1.3Hz, 1H). C NMR (100MHz, CDCl ):
3
δ 151.7, 148.6 (q, J=36.2Hz), 142.9, 140.2, 127.7 (q,
General procedure for the amination
J=285.6Hz), 117.7 (q, J=2.2Hz), 115.4 (q, J=1.0Hz),
+
In a Schlenk tube, a mixture of the catalyst 1 (0.5mol%), 108.6. MS-ESI : m/z=213.1. Anal. Calcd for C H F N : C,
9
6
3
3
2
-N-heteroaryl chloride (1.0mmol), pyrazole (1.1mmol), 50.7; H, 2.8; N, 19.7. Found: C, 50.9; H, 2.5; N, 19.9%.
and KO Bu (2.0 mmol) in dioxane (3mL) was evacuated
t
and charged with nitrogen. The reaction mixture was heated 4-(Trifluoromethyl)-2-(3,5-dimethyl-1H-pyrazol-1-yl)pyri-
1
at 110°C for 12h. After being cooled and quenched with dine (8b): H NMR (400MHz, CDCl ): δ 8.56 (d, J=4.4Hz,
3
water, the mixture was extracted with CH Cl . The solvent 1H), 8.20 (s, 1H), 7.33 (d, J=7.8Hz, 1H), 6.03 (s, 1H), 2.68
2
2
1
3
was evaporated and the resulting residue was purified by (s, 3H), 2.32 (s, 3H). C NMR (100MHz, CDCl ): δ 155.6,
flash chromatography on silica gel. The products 4a, b,
a, 5b, 7a, 11a, 11b, and 12a are known com- J=276.4Hz), 115.8 (q, J=1.2Hz), 111.5 (q, J=1.6Hz), 15.0,
pounds and characterized by comparison of their data with 13.7. MS-ESI : m/z=241.1. Anal. Calcd for C H F N : C,
3
3
2
150.9, 148.6, 142.3, 141.2 (q, J=33.6Hz), 129.0, 124.6 (q,
3
3
34
35
36
37
38
5
+
11
10
3
3
those reported in the literature. Other products were charac- 54.8; H, 4.2; N, 17.4. Found: C, 55.1; H, 4.0; N, 17.7%.
1
13
terized by elemental analysis, MS, and H and C NMR.
1
6
-(Trifluoromethyl)-2-(1H-pyrazol-1-yl)pyridine (9a): H
1
5
-Methyl-2-(1H-pyrazol-1-yl)pyridine (2): H NMR (400MHz, NMR (400MHz, CDCl ): δ 8.60 (m, 2H), 8.28 (s, 1H), 7.80
3
1
3
CDCl ): δ 8.52 (d, J = 2.4 Hz, 1H), 8.22 (s, 1H), 7.87 (d, (s, 1H), 7.41 (d, J=4.8Hz, 1H), 6.52 (s, 1H). C NMR
3
J=8.2Hz, 1H), 7.72 (s, 1H), 7.62 (d, J=8.2Hz, 1H), 6.45 (100MHz, CDCl ): δ 151.5, 146.8 (q, J=32.2Hz), 142.8,
3
1
3
(
d, J=1.6Hz, 1H), 2.35 (s, 3H). C NMR (100MHz, 140.5, 127.6, 123.0 (q, J=272.6Hz), 117.6 (q, J=2.6Hz),
CDCl ): δ 149.8, 148.0, 141.8, 139.4, 131.0, 126.9, 112.1, 115.3 (q, J=1.4Hz), 108.4. MS-ESI : m/z=213.1. Anal.
+
3
+
1
07.6, 18.0. MS-ESI : m/z=159.1. Anal. Calcd for C H N : Calcd for C H F N : C, 50.7; H, 2.8; N, 19.7. Found: C,
9
9
3
9
6
3
3
C, 67.9; H, 5.7; N, 26.4. Found: C, 68.2; H, 5.3; N, 26.9%. 50.9; H, 2.3; N, 20.0%.

Xu et al.
5
Table 3. Crystallographic data for complex 1.
(λ=0.71073Å) at ambient temperature. The data were cor-
rected for Lorentz polarization factors as well as for absorp-
tion. The structure was solved by direct methods and
Empirical formula
C H BrCuF N O P
54 46 6 3 2 3
2
Fw
1119.30
refined by full-matrix least-squares methods on F with the
3
9
Crystal system
Space group
a (Å)
Monoclinic
SHELX-97 program. Crystal data, as well as details of
data collection and refinements of 1, are summarized in
Table 3. The Cambridge Crystallographic Data Centre
P2 /c
1
17.9246(4)
b (Å)
c (Å)
α (°)
21.3341(4)
14.7201(3)
90
(CCDC) deposition number is 1583423. These data can be
obtained free of charge from the CCDC via www.ccdc.cam.
ac.uk/datarequest/cif.
β (°)
γ (°)
113.918(3)
90
5145.7(2)
1.068
2280.0
93,565
9476
Declaration of conflicting interests
3
Volume (Å )
Goodness-of-fit (GOF)
F(000)
Reflections collected
Independent reflections
Final R indices [I>2σ(I)]
R indices (all data)
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
article.
Funding
R =0.0536, wR =0.1638
1
2
The author(s) disclosed receipt of the following financial support
for the research, authorship, and/or publication of this article: This
work was supported by the high-level introduction of talent
research start-up foundation of Jiangsu University of Science and
Technology.
R =0.0677, wR =0.1725
1
2
6
-(Trifluoromethyl)-2-(3,5-dimethyl-1H-pyrazol-1-yl)pyri-
1
dine (9b): H NMR (400MHz, CDCl ): δ 8.14 (d,
3
ORCID iD
J=8.4Hz, 1H), 7.93 (t, J=8.2Hz, 1H), 7.49 (d, J=7.6Hz,
1
3
Chen Xu
https://orcid.org/0000-0003-1589-736X
1
H), 6.04 (s, 1H), 2.71 (s, 3H), 2.32 (s, 3H). C NMR
(
1
100MHz, CDCl ): δ 167.4, 155.4, 153.0, 151.8, 150.5,
49.8, 141.8 (q, J=30.8Hz), 122.4 (q, J=268.2Hz), 114.0
3
References
(
q, J=1.8Hz), 109.1 (q, J=1.0Hz), 100.3, 14.6, 13.7. MS-
1. Eicher T, Hauptmann S and Speicher A. The chemistry of
heterocycles. 2nd ed. New York: Wiley-VCH, 2003.
+
ESI : m/z=241.1. Anal. Calcd for C H F N : C, 54.8; H,
4
1
1
10
3
3
2
. Kumar V, Kaur K, Gupta GK, et al. Eur J Med Chem 2013;
9: 735.
.2; N, 17.4. Found: C, 55.0; H, 3.8; N, 17.8%.
6
3
4
5
. Vo GD and Hartwig JF. J Am Chem Soc 2009; 131: 11049.
. Surry DS and Buchwald SL. Chem Sci 2010; 1: 1.
. Han X, Li HM, Xu C, et al. Transition Met Chem 2016; 41:
1
5
(
-Chloro-2-(1H-pyrazol-1-yl)pyridine (10a): H NMR
400MHz, CDCl ): δ 8.53 (s, 1H), 8.37 (s, 1H), 7.96 (d,
J=8.8Hz, 1H), 7.80–7.75 (m, 2H), 6.49 (d, J=1.6Hz, 1H).
C NMR (100MHz, CDCl ): δ 149.9, 146.7, 142.5, 138.5,
29.1, 127.2, 113.4, 108.3. MS-ESI : m/z=179.0. Anal.
3
4
03.
13
3
6. Diao XQ, Xu LT, Zhu W, et al. Org Lett 2011; 13: 6422.
7
+
1
. Antilla JC, Klapars A and Buchwald SL. J Am Chem Soc
Calcd for C H ClN : C, 53.5; H, 3.4; N, 23.4. Found: C,
2002; 124: 11684.
8
6
3
5
3.7; H, 3.0; N, 23.9%.
8. Strieter ER, Blackmond DG and Buchwald SL. J Am Chem
Soc 2005; 127: 4120.
9
. Monnier F and Taillefer M. Organometallics 2007; 26: 65.
5
-Chloro-2-(3,5-dimethyl-1H-pyrazol-1-yl)pyridine
1
10. Scott NM and Nolan SP. N-heterocyclic carbenes in synthe-
sis. Weinheim: Wiley-VCH, 2006.
(10b): H NMR (400MHz, CDCl ): δ 8.36 (s, 1H), 7.86
3
(
d, J=8.8Hz, 1H), 7.75 (d, J=7.2Hz, 1H), 6.01 (s, 1H),
1
1. Velazquez HD and Verpoort F. Chem Soc Rev 2012; 41:
032.
2. Xu C, Wang ZQ, Yuan XE, et al. J Organomet Chem 2015;
77: 1.
13. Li HM, Xu C, Duan LM, et al. Transition Met Chem 2013;
8: 313.
1
3
2
1
1
.63 (s, 3H), 2.30 (s, 3H). C NMR (100MHz, CDCl ): δ
3
7
52.0, 151.2, 146.1, 141.8, 138.0, 128.4, 116.5, 109.5,
1
+
4.7, 13.7. MS-ESI : m/z=207.1. Anal. Calcd for
7
C H ClN : C, 57.8; H, 4.9; N, 20.2. Found: C, 57.6; H,
4
1
0
10
3
.6; N, 20.6%.
3
1
4. Krylova VA, Djurovich PI, Whited MT, et al. Chem Commun
1
2
(
6
-(3,5-Dimethyl-1H-pyrazol-1-yl)pyrazine (12b): H NMR
2010; 46: 6696.
400MHz, CDCl ): δ 9.26 (s, 1H), 8.39 (d, J=3.0Hz, 2H), 15. Leitl MJ, Krylova VA, Djurovich PI, et al. J Am Chem Soc
3
13
2014; 136: 16032.
6. Wang ZQ, Zheng CJ, Wang WZ, et al. Inorg Chem 2016; 55:
.06 (s, 1H), 2.66 (s, 3H), 2.33 (s, 3H). C NMR (100MHz,
CDCl ): δ 151.2, 149.9, 142.5, 141.2, 140.7, 138.4, 110.0,
4.6, 13.8. MS-ESI+: m/z=174.1. Anal. Calcd for C H N :
C, 62.1; H, 5.8; N, 32.2. Found: C, 62.5; H, 5.5; N, 32.6%.
1
3
2
157.
1
9 10 4
1
1
7. Wang ZQ, Sun XJ, Xu C, et al. Front Chem 2019; 7: 422.
8. Xu C, Wang ZQ, Li Z, et al. Organometallics 2012; 31:
7
98.
9. Xu C, Li HM, Xiao ZQ, et al. Dalton Trans 2014; 43:
0235.
1
Crystal structure determination
1
Crystallographic data for complex 1 were collected on an 20. Scaltrito DV, Thompson DW, O’Callaghan JA, et al. Coord
Xcalibur Eos Gemini diffractometer with Mo-Kα radiation
Chem Rev 2000; 208: 243.

6
Journal of Chemical Research 00(0)
2
2
2
2
2
2
1. Alberico D, Scott ME and Lautens M. Chem Rev 2007; 30. Kim M, Shin T, Lee A, et al. Organometallics 2018; 37:
07: 174.
3253.
2. Xiao ZQ, Xu C, Li HM, et al. Transition Met Chem 2015; 31. Xu C, Hao XQ, Li Z, et al. Inorg Chem Commun 2012;
0: 501.
17: 34.
3. Billingsley KL and Buchwald SL. Angew Chem Int Ed 2008; 32. Liu HY, Yu ZT, Yuan YJ, et al. Tetrahedron 2010; 66: 9141.
1
4
4
7: 4695.
4. Xu C, Wang ZQ, Zhang YP, et al. Eur J Inorg Chem 2011;
011: 4878.
33. Liu SW, Zeng XJ and Xu B. Tetrahedron Lett 2016; 57:
3706.
34. Wang ZX and Chai ZY. Eur J Inorg Chem 2007; 2007: 4492.
2
5. Düfert MA, Billingsley KL and Buchwald SL. J Am Chem 35. Hedidi M, Erb W, Bentabed-Ababsa G, et al. Tetrahedron
Soc 2013; 135: 12877.
2016; 72: 6467.
6. Lee HW, Chan ASC and Kwong FY. Tetrahedron Lett 2009; 36. Chevallier F, Halauko YS, Pecceu C, et al. Org Biomol Chem
5
0: 5868.
2011; 9: 4671.
2
2
7. Wang L, Liu N and Dai B. RSC Adv 2015; 5: 82097.
37. Shiseido Company, Ltd. EP2250998 A1, 2010.
8. Nakafuji SY, Kobayashi JJ and Kawashima T. Angew Chem 38. Deng XH, Roessler A, Brdar I, et al. J Org Chem 2011; 7:
Int Ed 2008; 47: 1141.
8262.
2
9. Xu C, Li HM, Wang ZQ, et al. Aust J Chem 2012; 65: 366.
39. Sheldrick GM. Acta Crystallogr A 2008; 64: 112.