Synthesis of N-heterocyclic carbene-Pd(II) complexes and their catalytic activity in the Buchwald-Hartwig amination of aryl chlorides

Article abstract of DOI:10.1016/j.tet.2017.11.026

Novel N-heterocyclic carbene-palladium(II) complexes using 2-picolinic acid as the ancillary ligand have been successfully developed under mild conditions. Their catalytic activity in organic synthesis has been initially tested in the Buchwald-Hartwig amination of secondary and primary amines with aryl chlorides. Various substituents on both substrates can be tolerated, giving the desired coupling products in good to almost quantitative yields. The minimum catalyst loading can be 0.01 mol%, implying their potential application toward industrial processes.

Full text of DOI:10.1016/j.tet.2017.11.026

Accepted Manuscript
Synthesis of N-heterocyclic carbene-Pd(II) complexes and their catalytic activity in the
Buchwald-Hartwig amination of aryl chlorides
Zhi-Mao Zhang, Yu-Jue Gao, Jian-Mei Lu
PII:
S0040-4020(17)31174-2
10.1016/j.tet.2017.11.026
TET 29106
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 13 October 2017
Revised Date: 7 November 2017
Accepted Date: 10 November 2017
Please cite this article as: Zhang Z-M, Gao Y-J, Lu J-M, Synthesis of N-heterocyclic carbene-Pd(II)
complexes and their catalytic activity in the Buchwald-Hartwig amination of aryl chlorides, Tetrahedron
(2017), doi: 10.1016/j.tet.2017.11.026.
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ACCEPTED MANUSCRIPT
Graphical Abstract
Synthesis of N-heterocyclic carbene-Pd(II)
complexes and their catalytic activity in the
Buchwald-Hartwig amination of aryl
chlorides
Leave this area blank for abstract info.
Zhi-Mao Zhang, Yu-Jue Gao and Jian-Mei Lu
College of Chemistry and Materials Engineering, Wenzhou University, Chashan University Town, Wenzhou,
Zhejiang Province 325035, People’s Republic of China.
*

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Synthesis of N-heterocyclic carbene-Pd(II) complexes and their catalytic activity in
the Buchwald-Hartwig amination of aryl chlorides
Zhi-Mao Zhang, Yu-Jue Gao and Jian-Mei Lu
College of Chemistry and Materials Engineering, Wenzhou University, Chashan University Town, Wenzhou, Zhejiang Province 325035, People’s Republic of
China.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Novel N-heterocyclic carbene-palladium(II) complexes using 2-picolinic acid as the ancillary
ligand have been successfully developed under mild conditions. Their catalytic activity in
organic synthesis has been initially tested in the Buchwald-Hartwig amination of secondary and
primary amines with aryl chlorides. Various substituents on both substrates can be tolerated,
giving the desired coupling products in good to almost quantitative yields. The minimum
catalyst loading can be 0.01 mol%, implying their potential application toward industrial
processes.
Available online
Keywords:
N-heterocyclic carbene-palladium complex
amines
2009 Elsevier Ltd. All rights reserved
.
aryl chlorides
C-N coupling
synthetic method
1. Introduction
minimum catalyst loading can be 0.005 mol% in some cases.6b
As a part of our continuous work on the development of efficient
NHC-Pd(II) complexes and their application in the C-N coupling
reactions, we found novel NHC-Pd(II) complexes using 2-
picolinic acid as the ancillary ligand. They were also efficient
catalysts in the amination of aryl chlorides under low catalyst
loadings. Herein, we report these results in detail.
Nitrogen-containing compounds widely exist in pesticides,
materials, pharmaceuticals, natural products and other fields.1
Transition metals, especially palladium salts, catalyzed C-N
coupling seem to be one of the most popular strategies to obtain
such compounds.2 Traditionally, tertiary phosphines are
necessary to achieve highly efficient C-N coupling.2,3
Comparably, from its first isolation of free N-heterocyclic
carbene (NHC) by Arduengo’s group in 1991, NHCs have been
interesting ligands in palladium-catalyzed coupling reactions.4
Consequently, to date, some excellent NHC-Pd(II) complexes
have also been developed by different groups to achieve
satisfactory C-N coupling, especially for the more challenging
substrates such as aryl chlorides.5 However, most of them still
have the following shortcomings which may make them difficult
to be ideal candidates in organic synthesis: (1) the NHC skeleton
and/or palladium complexes are difficult to be obtained; (2) toxic
ancillary ligands are necessary; (3) the catalyst loading is usually
too high to be acceptable by industrial chemistry. In order to
overcome these obstacles, during the past years, using IPr
(commercially IPr.HCl as the precursor) as the NHC skeleton, we
have developed some novel NHC-Pd(II) complexes bearing
different ancillary ligands in a one-pot procedure in good to high
yields. In addition, all of them have been proven to be excellent
catalysts toward C-N coupling of primary and secondary amines
with aryl chlorides.6 In these complexes, we found that the
ancillary ligands have some effect on the catalytic activity. For
2. Results and discussion
2.1 Synthesis of NHC-Pd(II) complexes 3.
According to our previously reported methods,6 the reactions
were carried out using commercially available imidazolium salts
1 (X equiv), PdCl2 (0.15 mmol) and picolinic acid 2 (1.0 equiv)
as the substrates, K2CO3 (3.0 equiv) as the base in refluxing THF
(2.0 mL) for 12 h, giving the corresponding NHC-Pd(II)
complexes 3 in good to almost quantitative yields (Table 1). The
relative amounts of imidazolium salts 1 affected the reactions to
some extent. For example, when imidazolium salt 1a (1.1 equiv)
was added, the lowest yield of complex 3a was obtained in 86%
(Table 1, entry 1). Once the amount of 1 increased to 1.3 equiv,
the yield of complex 3a can further increase to 91% (Table 1,
entry 2). Finally, when the amount of 1 was elevated to 1.5 equiv,
the best yield was achieved (Table 1, entry 3). The amount of
K2CO3 also affected the reaction evidently. For instance, when it
was reduced to 2.0 equivalents, the yield dramatically dropped
from 99 to 82% (Table 1, entries 3 vs 4). Under the optimal
conditions, both imidazolium salts 1b and 1c can be also
instance, using iso-quinoline as the ancillary ligand, the
———
Corresponding author. Tel.: +86-577-86689300; fax: +86-577-86689300; e-mail: ljm@wzu.edu.cn

2
Tetrahedron
ACCEPTED MANUSCRIPT
N(2) = 80.3(2), C(7)-Pd(1)-Cl(1) = 91.10(19), O(2)-Pd(1)-Cl(1)
= 176.8(2), N(2)-Pd(1)-Cl(1) = 96.5(2).
transformed to the corresponding complexes 3b and 3c in 94 and
88% yields, respectively (Table 1, entries 5 and 6).
2.2 Buchwald-Hartwig amination of aryl chlorides
Once the structures of complexes 3 were fully characterized,
we chose Buchwald-Hartwig amination of aryl chlorides to
evaluate their catalytic activity. Initial examinations were carried
out using chlorobenzene 4a (0.7 mmol) and morpholine 5a (1.2
equiv) as the substrates, complex 3a (0.1 mol%) as the catalyst,
toluene (1.0 mL) as the solvent in 90 oC for 1 h to screen various
bases (1.3 equiv). Among them, KOtBu gave the best yield
(Table 2, entry 1). Product 6a can also be obtained in moderate
yield (74%) when NaOtBu was added. However, in the presence
of other bases such as Cs2CO3, LiOtBu, LiOH, Li2CO3, NaOH,
Na2CO3, NaHCO3, KOH, K2CO3, KHCO3 and K3PO4, no
reaction occurred. Using KOtBu as the base, a variety of solvents
was also tested. For instance, when THF and dioxane were
chosen as the solvents, high yields of product 6a can also be
achieved (94 and 91%, respectively). When other polar solvents
such as DMSO, DMF and DMAc were used, very low yields
were observed (22, 12 and 24%, respectively). Further studies
were then performed based on the result shown in Table 2, entry
1. For instance, if the catalyst loading was reduced to 0.05 mol%,
the yield drastically lowered to 59% (Table 2, entry 2). To our
pleasure, the yields increased gradually when the time was
prolonged (Table 2, entries 3 and 4), and the best same yield can
be observed when the reaction was carried out for 6 h (Table 2,
entry 4). If the catalyst loading was further reduced to 0.03 mol%,
1
All complexes 3 have been fully confirmed by H and 13C
o
the reaction should take place at 110 or 130 C for 12 h to give
NMR, MS and elemental analysis. To our delight, the yellow
crystals of complex 3a, which are suitable for single crystal
diffraction analysis, were obtained in a mixture of ethyl acetate
and dichloromethane by slow evaporation of the solvents. As
shown in Figure 1, the Pd centre of complex 3a is coordinated by
four different ligands such as one carbene carbon atom, one N
atom and one O atom from picolinic acid, and one Cl atom,
giving a very slightly distorted square-planar geometry. In such
structure, the NHC and the N atom are trans to each other [the
bond angles of C(7)-Pd(1)-N(2) = 172.4(3), O(2)-Pd(1)-Cl(1) =
176.8(2)].
good yields (Table 2, entries 7 and 8). Under the same conditions
shown in Table 1, entry 4, complexes 3b and 3c were also tested,
giving very low yields in both cases (Table 2, entries 9 and 10).
Table 2. Optimization for the complex 3-catalysed reaction of
chlorobenzene 4a with morpholine 5a.
Cl
H
N
NHC-Pd(II) 3 (X mol%)
N
O
+
KOtBu, toluene, Temp
O
5a
6a
Time
4a
Entrya
3 [X]
3a (0.10)
3a
Temp (oC)
Time (h)
Yield (%)b
1
2
90
90
1
1
99
59
87
98
66
76
87
89
7
(0.05)
3
3a (0.05)
3a (0.05)
3a (0.03)
3a (0.03)
3a (0.03)
3a (0.03)
3b (0.05)
3c (0.05)
90
3
4
90
6
5
90
6
6
90
12
12
12
6
7
110
130
90
8
9
10
90
6
7
a Reaction conditions: 4a (0.7 mmol), 5a (0.84 mmol), KOtBu
(0.91 mmol), 3 (X mol%), toluene (1.0 mL). b Isolated yields.
Fig. 1 The molecular structure of complex 3a showing 30%
probability ellipsoids; all hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and bond angles (o): Selected bond
distances (Å) and angles (°): Pd(1)-C(7) = 1.974(6), Pd(1)-O(2) =
2.045(6), Pd(1)-N(2) = 2.071(6), Pd(1)-Cl(1) = 2.212(2); C(7)-
Pd(1)-O(2) = 92.1(2), C(7)-Pd(1)-N(2) = 172.4(3), O(2)-Pd(1)-
Under the conditions shown in Table 2, entry 4, kinds of aryl
chlorides 4 and secondary amines 5 were first applied to test the
scope and limitation of this reaction. The results are illustrated in

3
Table 3. All reactions took place smoothly to give the desired C-
N coupling products in good to high yields. Substituents on the
aryl chlorides 4 did not affect the reactions evidently. Electron-
neutral, -poor, -rich and sterically-hindered substituents on aryl
chlorides were all tolerated. For example, all reactions of 4-
methylphenyl chloride 4d, 3-methoxyphenyl chloride 4e and 3-
fluorophenyl chloride 4f with morpholine 5a gave products 6d-f
in high yields (Table 3, entries 3-5). The heteroaryl chloride such
as 2-chloropyridine 4h was also tolerated to give product 6h in
92% yield within 12 h. Other secondary amines such as
pyrrolidine 5b, piperidine 5c, N-methylaniline 5d and N-
methylbenzylamine 5e are all suitable substrates in the reactions
with various aryl chlorides 4 to give the desired products 6i-u in
good to high yields (Table 3, entries 8-20).
reactions dramatically except for the reaction involving 2-
ACCEPTED MANUSCRIPT
methoxyphenyl chloride 4i, which gave the lowest yield, maybe
partially due to the coordination of the oxygen atom to the
palladium centre (Table 4, entry 15). Among the reactions
examined, the lowest catalyst loading can be 0.01 mol%,
implying their potential application toward industrial processes
(Table 4, entries 2-6 and 16).
Table 4. Complex 3a-catalyzed C-N coupling of aryl chlorides 4
with anilines 7.
Cl
NH2
H
N
3a
NHC-Pd(II)
(X mol%)
+
KOtBu, toluene
R
R'
7 (R')
7a
R
8
R'
4
7
Entrya 4 (R)
[X] Temp (oC) Time (h) Yield (%)b
1
4b
4b
4b
4b
4b
4b
4b
4b
4b
4b
0.03
0.01
0.01
0.01
0.01
130
110
110
110
110
110
110
130
130
130
130
130
130
130
130
110
110
130
24
3
8a
(2-Me)
(H)
7b (2-Me)
7c
, 95
8b, 96
8c
2
3
12
3
(4-Me)
, 97
7d (2,4-Me2)
7e (2,6-Me2)
4
8d, 98
8e, 91
8f, 96
8g, 91
8h, 91
8i, 90
8j, 93
8k, 95
8l, 99
8m, 89
8n, 95
8o, 79
8p, 97
8q, 94
8r, 88
5
3
6
7f (2,4,6-Me3) 0.01
12
12
24
24
24
24
24
24
24
24
12
6
7g (2,6-iPr2)
7h (2-OMe)
7i (4-OMe)
7j (4-F)
7d
7
0.02
0.02
0.02
0.02
0.03
0.03
0.05
0.03
0.03
0.01
0.02
0.05
8
9
10
11
12
13
14
15
16
17
18
4a (H)
4c (3-Me)
4d (4-Me)
7d
7d
4e (3-OMe) 7d
4i (2-OMe) 7d
4j (2,6-Me2) 7d
4k (2,4,6-Me3)7d
4l (2,6-iPr2)
7d
24
a All reactions were carried out using 4 (0.70 mmol), 7 (0.84 mmol), KOtBu
(0.91 mmol), (X mol%) in toluene (0.5 mL). b Isolated yields.
3
Finally, primary alkyl amines such as benzyl amine 7k and
cyclohexyl amine 7l were also investigated with 2-methylphenyl
chloride 4b under the similar conditions (Scheme 1). Both
reactions performed well enough in 0.01 or 0.03 mol% catalyst
loading, giving products 9a and 9b in 96 and 94% yields,
respectively.
Based on the above successful results on the NHC-Pd(II)
complex 3a-catalyzed C-N coupling of aryl chlorides 4 with
secondary amines 5, anilines 7 were then tested with a variety of
aryl chlorides 4 under the similar conditions. To our delight, all
reactions also performed well enough to give the corresponding
coupled products 8 in good to almost quantitative yields (Table
4). Substituents such as electron-rich, -neutral, -poor and
sterically-hindered ones are all compatible in these
transformations. Special attention was paid on the reactions
involving sterically-hindered substituents on one or both of the
substrates. It seems that these substituents did not affect the
3. Conclusion
In conclusion, a series of novel NHC-Pd(II) complexes using
2-picolinic acid as the ancillary ligand has been developed in a
one-pot procedure under mild conditions. All complexes have

4
Tetrahedron
ACCEPTED MANUSCRIPT
1
been fully characterized by standard methods such as H and 13C
NMR, MS and elemental analysis. Their catalytic activity was
initially tested in the Buchwald-Hartwig amination of various
secondary and primary amines with aryl chlorides, giving good to
almost quantitative yields. The minimum catalyst loading can be
0.01 mol%, and this work will thus enrich the NHC chemistry in
organic synthesis.
2961, 2921, 1729, 1666, 1650, 1597, 1484, 1341, 1328, 1285,
1232, 1159, 1089, 1043, 927, 859, 773, 766, 741, 705 cm-1.
HRMS (ESI) calcd for C27H28ClN3O2PdNa [M+Na]+: 592.0800;
found: 592.0803. Anal. calcd for C27H28ClN3O2Pd.1/2CH3CO2Et:
C, 56.87%; H, 5.27%; N, 6.86%; found: C, 56.81%; H, 5.33%;
N, 6.85%.
4.2.2 General procedure for the complex 3a-catalyzed
Buchwald-Hartwig amination of aryl chlorides. Under a N2
atmosphere, KOtBu (102.1 mg, 1.3 equiv) and a solution of
complex 3a (10-50 µL, 0.01-0.05 mol%, prepared from 4.6 mg of
complex 3a in 1.0 mL dichloromethane) were added into a
Schlenk reaction tube. The tube was sealed and the solvent was
removed under reduced pressure. Then toluene (0.5 mL), amines
(0.84 mmol) and aryl chlorides (0.70 mmol) were successively
added. The mixture was stirred vigorously at the specified
temperature for 3-24 h. Then the solvent was removed under
reduced pressure and the residue was purified by flash column
chromatography (SiO2) to give the corresponding products.
4. Experimental section
4.1 General remarks
NMR spectra were recorded at 500 MHz (for 1H NMR) or 125
MHz (for 13C NMR), respectively. H and 13C NMR spectra
1
recorded in CDCl3 solutions were referenced to TMS (0.00 ppm)
and the residual solvent peak (77.0 ppm), respectively. J-values
are given in Hz. All solvents were dried by standard methods.
The mass analyzer type for the high resolution mass spectra
(HRMS) is quadrupole. All amines were distilled prior to using.
Other commercially obtained reagents were used without further
purification. Flash column chromatography was performed on
silica gel (300-400 mesh).
4.2.2.1 Compound 6a6a: white solid. 1H NMR (500 MHz, CDCl3,
TMS) δ 7.26 (t, J = 7.5 Hz, 2H), 6.90-6.85 (m, 3H), 3.83 (t, J =
4.5 Hz, 4H), 3.12 (t, J = 4.5 Hz, 4H). 13C NMR (125 MHz,
CDCl3) δ 151.2, 129.1, 119.9, 115.6, 66.8, 49.3.
4.2 Experimental procedure
4.2.1 General procedure for the synthesis of NHC-Pd(II)
complexes 3. Under a N2 atmosphere, a mixture of imidazolium
salts 1 (0.225 mmol), PdCl2 (0.15 mmol), K2CO3 (0.45 mmol)
and picolinic acid 2 (0.15 mmol) was stirred in anhydrous THF
(2.0 mL) under reflux for 12 h. Then the solvent was removed
under reduced pressure, and the residue was purified by flash
column chromatography (SiO2) to give complexes 3 as yellow
solids.
1
4.2.2.2 Compound 6b6a: colorless liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.16 (t, J = 7.5 Hz, 2H), 7.01-6.97 (m, 2H), 3.83
(t, J = 4.5 Hz, 4H), 2.89 (t, J = 4.5 Hz, 4H), 2.30 (s, 3H). 13C
NMR (125 MHz, CDCl3) δ 151.2, 132.5, 131.1, 126.6, 123.3,
118.9, 67.4, 52.2, 17.8.
1
4.2.2.3 Compound 6c6a: colorless liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.15 (t, J = 8.0 Hz, 1H), 6.72-6.69 (m, 3H), 3.82
o
(t, J = 4.5 Hz, 4H), 3.11 (t, J = 4.5 Hz, 4H), 2.31 (s, 3H). 13
C
4.2.1.1 Compound 3a: yellow solid. m.p. 248 C (decomposed).
1H NMR (500 MHz, CDCl3, TMS) δ 8.55 (d, J = 5.5 Hz, 1H),
7.83-7.77 (m, 2H), 7.49 (t, J = 7.5 Hz, 2H), 7.34 (d, J = 7.5 Hz,
4H), 7.31-7.28 (m, 1H), 7.17 (s, 2H), 2.95 (hept, J = 7.0 Hz, 4H),
1.42 (d, J = 7.0 Hz, 12H), 1.14 (d, J = 7.0 Hz, 12H). 13C NMR
(125 MHz, CDCl3) δ 172.7, 157.4, 151.3, 146.8, 146.5, 139.1,
134.5, 130.4, 126.6, 126.2, 125.1, 124.0, 28.6, 26.2, 22.9. IR
(neat) ν 2964, 1668, 1600, 1458, 1408, 1337, 1291, 1047, 944,
800, 771, 755, 713 cm-1. HRMS (ESI) calcd for C33H41ClN3O2Pd
[M+H]+: 654.1920; found: 654.1917. Anal. calcd for
C33H40ClN3O2Pd: C, 60.47%; H, 6.18%; N, 6.44%; found: C,
60.62%; H, 6.11%; N, 6.31%.
NMR (125 MHz, CDCl3) δ 151.3, 138.7, 128.9, 120.8, 116.4,
112.8, 66.8, 49.4, 21.6.
4.2.2.4 Compound 6d6a: white solid. 1H NMR (500 MHz, CDCl3,
TMS) δ 7.07 (d, J = 8.0 Hz, 2H), 6.81 (d, J = 8.0 Hz, 2H), 3.82 (t,
J = 4.5 Hz, 4H), 3.07 (t, J = 4.5 Hz, 4H), 2.26 (s, 3H). 13C NMR
(125 MHz, CDCl3) δ 149.1, 129.6, 129.3, 115.9, 66.8, 49.8, 20.3.
1
4.2.2.5 Compound 6e6a: colorless liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.16 (d, J = 8.0 Hz, 1H), 6.51 (d, J = 8.5 Hz,
1H), 6.44-6.42 (m, 2H), 3.82 (t, J = 4.5 Hz, 4H), 3.77 (s, 3H),
3.12 (t, J = 4.5 Hz, 4H). 13C NMR (125 MHz, CDCl3) δ 160.6,
152.6, 129.7, 108.3, 104.6, 102.1, 66.7, 55.0, 49.2.
o
4.2.1.2 Compound 3b: yellow solid. m.p. 182 C (decomposed).
1
4.2.2.6 Compound 6f6a: colorless liquid. H NMR (500 MHz,
1H NMR (500 MHz, CDCl3, TMS) δ 8.53 (d, J = 4.5 Hz, 1H),
7.86-7.79 (m, 2H), 7.33-7.30 (m, 3H), 7.25-7.22 (m, 4H), 7.18-
7.17 (m, 2H), 2.34 (s, 12H). 13C NMR (125 MHz, CDCl3) δ
172.9, 155.2, 151.0, 146.5, 139.3, 137.2, 136.7, 129.6, 128.6,
126.7, 126.2, 124.0, 18.3. IR (neat) ν 3160, 3087, 2915, 1668,
CDCl3, TMS) δ 7.18 (dd, J = 15.0, 8.0 Hz, 1H), 6.654 (dd, J =
8.0, 2.0 Hz, 1H), 6.58-6.52 (m, 2H), 3.82 (t, J = 4.5 Hz, 4H), 3.12
(t, J = 4.5 Hz, 4H). 13C NMR (125 MHz, CDCl3) δ 163.8 (d, JC-F
= 241.875 Hz), 152.9 (d, JC-F = 9.625 Hz), 130.1 (d, JC-F = 9.875
Hz), 110. 7 (d, JC-F = 2.375 Hz), 106.0 (d, JC-F = 21.25 Hz), 102.3
(d, JC-F = 25.0 Hz), 66.6, 48.7.
1478, 1330, 1288, 1229, 1158, 1046, 942, 848, 778, 758, 709 cm-
1
.
HRMS (ESI) calcd for C25H24ClN3O2PdNa [M+Na]+:
1
4.2.2.7 Compound 6g6a: colorless liquid. H NMR (500 MHz,
564.0487; found: 564.0496. Anal. calcd for C25H24ClN3O2Pd: C,
55.57%; H, 4.48%; N, 7.78%; found: C, 55.51%; H, 4.55%; N,
7.69%.
CDCl3, TMS) δ 6.97 (t, J = 9.5 Hz, 2H), 6.86 (dd, J = 9.5, 5.5
Hz, 2H), 3.85 (t, J = 4.5 Hz, 4H), 3.07 (t, J = 4.5 Hz, 4H). 13C
NMR (125 MHz, CDCl3) δ 157.3 (d, JC-F = 237.625 Hz), 147.9
(d, JC-F = 2.0 Hz), 117.4 (d, JC-F = 7.5 Hz), 115.5 (d, JC-F = 22.0
Hz), 66.9, 50.3.
o
4.2.1.3 Compound 3c: yellow solid. m.p. 260 C (decomposed).
1H NMR (500 MHz, CDCl3, TMS) δ 8.53 (d, J = 5.5 Hz, 1H),
7.85 (d, J = 7.5 Hz, 1H), 7.80 (t, J = 7.5 Hz, 1H), 7.30 (t, J = 6.5
Hz, 1H), 7.13 (s, 2H), 7.02 (s, 4H), 2.33 (s, 6H), 2.28 (s, 12H).
13C NMR (125 MHz, CDCl3) δ 172.9, 155.0, 150.9, 146.4, 139.3,
139.2, 134.7, 129.2, 126.7, 126.1, 124.1, 21.1, 18.2. IR (neat) ν
1
4.2.2.8 Compound 6h6a: pale yellow liquid. H NMR (500 MHz,
CDCl3, TMS) δ 8.20 (d, J = 3.0 Hz, 1H), 7.49 (td, J = 8.5, 1.5

5
Hz, 1H), 6.67-6.62 (m, 2H), 3.81 (t, J = 4.5 Hz, 4H), 3.49 (t, J =
3H), 2.28 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 149.9, 139.1,
ACCEPTED MANUSCRIPT
4.5 Hz, 4H). 13C NMR (125 MHz, CDCl3) δ 159.5, 147.9, 137.3,
138.7, 129.0, 128.5, 126.8, 117.6, 113.1, 109.7, 56.6, 38.3, 21.9.
4.2.2.19 Compound 6s6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.27 (t, J = 7.5 Hz, 2H), 7.20-7.19 (m, 3H), 7.09
(t, J = 8.0 Hz, 1H), 6.35 (d, J = 8.0 Hz, 1H), 6.29-6.26 (m, 2H),
4.48 (s, 2H), 3.71 (s, 3H), 2.96 (s, 3H). 13C NMR (125 MHz,
CDCl3) δ 160.7, 151.1, 138.9, 129.7, 128.4, 126.8, 126.6, 105.5,
101.3, 98.9, 56.5, 54.9, 38.4.
113.6, 106.8, 66.6, 45.5.
4.2.2.9 Compound 6i6a: pale yellow liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.11 (t, J = 8.0 Hz, 1H), 6.23 (dd, J = 8.0, 2.0
Hz, 1H), 6.19 (dd, J = 8.0, 2.0 Hz, 1H), 6.10 (t, J = 2.0 Hz, 1H),
3.78 (s, 3H), 3.25 (quintet, J = 4.5 Hz, 4H), 1.97 (quintet, J = 4.5
Hz, 4H). 13C NMR (125 MHz, CDCl3) δ 160.7, 149.3, 129.7,
104.9, 100.5, 97.9, 55.0, 47.6, 25.4.
1
1
4.2.2.20 Compound 6t: pale yellow liquid. H NMR (500 MHz,
4.2.2.10 Compound 6j6b: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.23 (t, J = 8.0 Hz, 2H), 6.93 (d, J = 8.0 Hz, 2H),
6.80 (t, J = 8.0 Hz, 1H), 3.14 (t, J = 5.5 Hz, 4H), 1.69 (quintet, J
= 5.5 Hz, 4H), 1.56 (quintet, J = 5.5 Hz, 2H). 13C NMR (125
MHz, CDCl3) δ 152.2, 128.9, 119.1, 116.5, 50.6, 25.8, 24.3.
CDCl3, TMS) δ 7.25 (t, J = 7.0 Hz, 2H), 7.18 (d, J = 7.0 Hz, 1H),
7.14 (d, J = 7.5 Hz, 2H), 7.05 (dd, J = 15.0, 7.5 Hz, 1H), 6.43 (d,
J = 8.5 Hz, 1H), 6.39-6.33 (m, 2H). 4.42 (s, 2H), 2.91 (s, 3H). 13C
NMR (125 MHz, CDCl3) δ 164.1 (d, JC-F = 240.375 Hz), 151.4
(d, JC-F = 10.625 Hz), 138.3, 130.1 (d, JC-F = 10.25 Hz), 128.6,
4.2.2.11 Compound 6k6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.12 (t, J = 7.5 Hz, 1H), 6.75-6.73 (m, 2H), 6.64
(d, J = 7.5 Hz, 1H), 3.12 (t, J = 5.5 Hz, 4H), 2.30 (s, 3H), 1.69
(quintet, J = 5.5 Hz, 4H), 1.55 (quintet, J = 5.5 Hz, 2H). 13C
NMR (125 MHz, CDCl3) δ 152.3, 138.5, 128.8, 120.1, 117.4,
113.6, 50.7, 25.9, 24.3, 21.7.
127.0, 126.6, 107.8, 102.8 (d, JC-F = 21.5 Hz), 99.2 (d, JC-F
=
25.875 Hz), 56.3, 38.5. IR (neat) ν 2895, 2399, 1620, 1573, 1501,
1451, 1372, 1351, 1232, 1159, 1010, 955, 822, 754, 732, 693,
680 cm-1. HRMS (ESI) calcd for C14H15FN [M+H]+: 216.1183;
found: 216.1184.
1
4.2.2.21 Compound 6u: pale yellow liquid. H NMR (500 MHz,
1
4.2.2.12 Compound 6l6a: colorless liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.28 (t, J = 7.0 Hz, 2H), 7.22-7.18 (m, 3H), 6.88
(t, J = 8.5 Hz, 2H), 6.65-6.64 (m, 2H), 4.42 (s, 2H), 2.91 (s, 3H).
13C NMR (125 MHz, CDCl3) δ 155.5 (d, JC-F = 233.75 Hz),
CDCl3, TMS) δ 7.13 (t, J = 8.0 Hz, 1H), 6.54 (dd, J = 8.0, 2.0
Hz, 1H), 6.47 (t, J = 2.0 Hz, 1H), 6.36 (dd, J = 8.0, 2.0 Hz, 1H),
3.76 (s, 3H), 3.13 (t, J = 5.0 Hz, 4H), 1.68 (quintet, J = 5.5 Hz,
4H), 1.55 (quintet, J = 5.5 Hz, 2H). 13C NMR (125MHz, CDCl3)
δ 160.5, 153.5, 129.5, 109.2, 103.9, 102.7, 55.0, 50.4, 25.7, 24.3.
146.5, 138.8, 128.5, 126.9 (d, JC-F = 11.625 Hz), 115.4 (d, JC-F
=
21.875 Hz), 113.7 (d, JC-F = 7.25 Hz), 57.5, 39.0. IR (neat) ν
2882, 2815, 1603, 1514, 1448, 1368, 1351, 1225, 1113, 945, 811,
751, 733, 708, 693 cm-1. HRMS (ESI) calcd for C14H15FN
[M+H]+: 216.1183; found: 216.1189.
4.2.2.13 Compound 6m6b: pale yellow liquid. H NMR (500
1
MHz, CDCl3, TMS) δ 8.16 (d, J = 3.5 Hz, 1H), 7.41 (t, J = 8.5
Hz, 1H), 6.61 (d, J = 8.5 Hz, 1H), 6.53 (t, J = 5.5 Hz, 1H), 3.50
(s, 4H), 1.62 (s, 6H). 13C NMR (125 MHz, CDCl3) δ 159.6,
147.8, 137.1, 112.2, 106.9, 46.1, 25.4, 24.6.
4.2.2.14 Compound 6n6b: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.25 (t, J = 8.0 Hz, 4H), 7.01 (d, J = 8.0 Hz, 4H),
6.94 (t, J = 7.0 Hz, 2H), 3.29 (s, 3H). 13C NMR (125 MHz,
CDCl3) δ 149.0, 129.1, 121.2, 120.4, 40.1.
4.2.2.15 Compound 6o6b: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.25 (t, J = 7.5 Hz, 2H), 7.15 (t, J = 7.5 Hz, 1H),
6.99 (d, J = 8.0 Hz, 2H), 6.92 (t, J = 7.5 Hz, 1H), 6.85-6.82 (m,
2H), 6.78 (d, J = 7.5 Hz, 1H), 3.28 (s, 3H), 2.29 (s, 3H). 13C
NMR (125 MHz, CDCl3) δ 149.1, 149.0, 138.9, 129.1, 129.0,
122.3, 121.4, 120.9, 120.1, 117.9, 40.2, 21.5.
4.2.2.16 Compound 6p6b: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.27 (t, J = 8.0 Hz, 2H), 7.14 (t, J = 8.0 Hz, 1H),
7.05 (d, J = 8.0 Hz, 2H), 6.97 (t, J = 8.0 Hz, 1H), 6.57 (dd, J =
8.0, 2.0 Hz, 1H), 6.53 (t, J = 2.0 Hz, 1H), 6.47 (dd, J = 8.0, 2.0
Hz, 1H), 3.73 (s, 3H), 3.28 (s, 3H). 13C NMR (125 MHz, CDCl3)
δ 160.5, 150.4, 148.9, 129.7, 129.2, 121.9, 121.6, 112.2, 105.9,
105.6, 55.1, 40.2.
1
4.2.2.22 Compound 8a6a: colorless liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.21 (t, J = 7.5 Hz, 3H), 7.16 (d, J = 7.5 Hz, 1H),
7.10 (t, J = 7.5 Hz, 1H), 6.91-6.85 (m, 4H), 5.30 (s, 1H), 2.20 (s,
3H). 13C NMR (125 MHz, CDCl3) δ 144.0, 141.2, 130.9, 129.2,
128.4, 126.7, 122.0, 120.3, 119.0, 117.3, 17.8.
4.2.2.23 Compound 8b6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.16 (d, J = 7.5 Hz, 2H), 7.08 (t, J = 7.5 Hz, 2H),
6.96 (d, J = 7.5 Hz, 2H), 6.87 (t, J = 7.5 Hz, 2H), 5.10 (s, 1H),
2.23 (s, 6H). 13C NMR (125 MHz, CDCl3) δ 142.0, 130.8, 127.5,
126.7, 121.3, 118.3, 17.7.
4.2.2.24 Compound 8c6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.13 (d, J = 8.0 Hz, 2H), 7.07 (t, J = 7.5 Hz, 1H),
7.03 (d, J = 8.0 Hz, 2H), 6.87-6.83 (m, 3H), 5.22 (s, 1H), 2.27 (s,
3H), 2.20 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 142.0, 141.1,
130.8, 130.3, 129.7, 127.1, 126.7, 121.1, 118.5, 117.5, 20.5, 17.7.
4.2.2.25 Compound 8d6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.13 (d, J = 7.5 Hz, 1H), 7.04 (t, J = 7.5 Hz, 1H),
7.00 (s, 1H), 6.92 (s, 2H), 6.81 (d, J = 7.5 Hz, 2H), 5.01 (s, 1H),
2.27 (s, 3H), 2.23 (s, 3H), 2.18 (s, 3H). 13C NMR (125 MHz,
CDCl3) δ 142.9, 138.9, 131.7, 131.5, 130.6, 129.2, 127.2, 126.7,
125.9, 120.5, 120.2, 116.4, 20.6, 17.7, 17.6.
4.2.2.26 Compound 8e6a: white solid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.12-7.05 (m, 4H), 6.95 (t, J = 7.5 Hz, 1H), 6.69
(t, J = 7.5 Hz, 1H), 6.14 (d, J = 8.0 Hz, 1H), 4.91 (s, 1H), 2.32 (s,
3H), 2.17 (s, 6H). 13C NMR (125 MHz, CDCl3) δ 144.1, 138.8,
135.5, 130.2, 128.5, 126.9, 125.5, 122.4, 118.1, 111.8, 18.2, 17.6.
4.2.2.27 Compound 8f6a: white solid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.09 (d, J = 7.5 Hz, 1H), 6.95-6.93 (m, 3H), 6.66
(t, J = 7.5 Hz, 1H), 6.12 (d, J = 7.5 Hz, 1H), 4.82 (s, 1H), 2.29 (s,
4.2.2.17 Compound 6q6b: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.27 (t, J = 7.5 Hz, 2H), 7.20-7.17 (m, 5H), 6.73-
6.67 (m, 3H), 4.48 (s, 2H), 2.96 (s, 3H). 13C NMR (125 MHz,
CDCl3) δ 149.7, 139.0, 129.1, 128.5, 126.8, 126.7, 116.5, 112.4,
56.6, 38.4.
4.2.2.18 Compound 6r6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.28 (t, J = 7.0 Hz, 2H), 7.21 (d, J = 7.0 Hz, 3H),
7.08 (t, J = 8.0 Hz, 1H), 6.57-6.52 (m, 3H), 4.48 (s, 2H), 2.95 (s,

6
Tetrahedron
ACCEPTED MANUSCRIPT
1
6H), 2.13 (s, 6H). 13C NMR (125 MHz, CDCl3) δ 144.5, 136.0,
135.6, 135.1, 130.2, 129.2, 126.9, 122.0, 117.7, 111.4, 20.8, 18.0,
17.5.
4.2.2.35 Compound 8n: pale yellow liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.12-7.06 (m, 2H), 7.00 (s, 1H), 6.93 (d, J = 8.0
Hz, 1H), 6.41-6.37 (m, 3H), 5.26 (s, 1H), 3.71 (s, 3H), 2.27 (s,
3H), 2.18 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 160.8, 146.6,
137.9, 132.6, 131.6, 130.3, 129.9, 127.2, 121.7, 108.8, 104.8,
101.8, 55.1, 20.7, 17.8. IR (neat) ν 3371, 3007, 2915, 2829, 1905,
1597, 1491, 1461, 1434, 1305, 1262, 1152, 1033, 816, 756, 688
cm-1. HRMS (ESI) calcd for C15H18NO [M+H]+: 228.1383;
found: 228.1385.
4.2.2.28 Compound 8g6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.28 (t, J = 7.5 Hz, 1H), 7.22 (d, J = 7.5 Hz, 2H),
7.11 (d, J = 7.5 Hz, 1H), 6.93 (t, J = 7.5 Hz, 1H), 6.65 (t, J = 7.5
Hz, 1H), 6.11 (d, J = 7.5 Hz, 1H), 4.89 (s, 1H), 3.11 (hept, J =
6.5 Hz, 2H), 2.33 (s, 3H), 1.17 (d, J = 6.5 Hz, 6H), 1.11 (d, J =
6.5 Hz, 6H). 13C NMR (125 MHz, CDCl3) δ 147.2, 146.0, 135.7,
130.1, 127.0, 126.9, 123.8, 121.2, 117.5, 111.5, 28.2, 24.7, 23.0,
17.6.
4.2.2.29 Compound 8h6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.30 (d, J = 8.0 Hz, 1H), 7.19 (d, J = 7.5 Hz,
1H), 7.13 (t, J = 7.5 Hz, 1H), 7.02 (d, J = 7.5 Hz, 1H), 6.93 (t, J =
7.5 Hz, 1H), 6.87-6.80 (m, 3H), 5.86 (s, 1H), 3.87 (s, 3H), 2.26
(s, 3H). 13C NMR (125 MHz, CDCl3) δ 148.0, 140.8, 133.9,
130.8, 129.3, 126.6, 122.1, 120.8, 119.6, 119.3, 114.4, 110.4,
55.6, 17.8.
4.2.2.30 Compound 8i6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.13 (d, J = 7.5 Hz, 1H), 7.06 (t, J = 7.5 Hz, 1H),
6.99 (d, J = 8.0 Hz, 3H), 6.84 (d, J = 8.0 Hz, 2H), 6.80 (t, J = 7.5
Hz, 1H), 5.19 (s, 1H), 3.77 (s, 3H), 2.23 (s, 3H). 13C NMR (125
MHz, CDCl3) δ 155.1, 143.3, 136.4, 130.7, 126.7, 125.4, 122.0,
120.0, 115.4, 114.7, 55.5, 17.7.
4.2.2.31 Compound 8j6a: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.15 (d, J = 7.5 Hz, 1H), 7.10-7.05 (m, 2H),
6.94-6.86 (m, 5H), 5.22 (s, 1H), 2.21 (s, 3H). 13C NMR (125
MHz, CDCl3) δ 157.8 (d, JC-F = 237.875 Hz), 142.0, 139.8, 130.9,
127.3, 126.8, 121.5, 120.0 (d, JC-F = 7.625 Hz), 117.4, 115.8 (d,
JC-F = 22.375 Hz), 17.7.
1
4.2.2.36 Compound 8o: pale yellow liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.16 (d, J = 8.0 Hz, 1H), 7.01 (s, 1H), 6.94 (d, J
= 8.0 Hz, 1H), 6.85 (d, J = 8.0 Hz, 1H), 6.82 (d, J = 8.0 Hz, 1H),
6.79 (t, J = 7.5 Hz, 1H), 6.74 (t, J = 7.5 Hz, 1H), 5.77 (s, 1H),
3.84 (s, 3H), 2.27 (s, 3H), 2.20 (s, 3H). 13C NMR (125 MHz,
CDCl3) δ 147.6, 137.9, 134.9, 132.3, 131.5, 130.5, 127.1, 121.4,
120.9, 118.5, 113.4, 110.2, 55.5, 20.6, 17.7. IR (neat) ν 3418,
2921, 2829, 1600, 1517, 1454, 1338, 1292, 1235, 1172, 1116,
1027, 806, 776, 736 cm-1. HRMS (ESI) calcd for C15H18NO
[M+H]+: 228.1383; found: 228.1389.
4.2.2.37 Compound 8p6b: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.10 (d, J = 7.0 Hz, 2H), 7.04 (t, J = 7.0 Hz, 1H),
6.95 (s, 1H), 6.76 (d, J = 8.0 Hz, 1H), 6.07 (d, J = 8.0 Hz, 1H),
4.81 (s, 1H), 2.29 (s, 3H), 2.22 (s, 3H), 2.16 (s, 6H). 13C NMR
(125 MHz, CDCl3) δ 141.7, 139.2, 135.1, 131.1, 128.5, 127.4,
127.2, 125.1, 122.8, 112.2, 20.4, 18.2, 17.5.
4.2.2.38 Compound 8q6b: white solid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.19 (s, 1H), 6.90 (s, 2H), 6.73 (d, J = 8.0 Hz,
1H), 6.04 (d, J = 8.0 Hz, 1H), 4.70 (s, 1H), 2.27 (s, 3H), 2.26 (s,
3H), 2.20 (s, 3H), 2.11 (s, 6H). 13C NMR (125 MHz, CDCl3) δ
142.1, 136.4, 135.2, 134.7, 131.0, 129.1, 127.2, 126.9, 122.3,
111.7, 20.8, 20.3, 18.0, 17.5.
1
4.2.2.32 Compound 8k7: yellow liquid. H NMR (500 MHz,
1
4.2.2.39 Compound 8r: pale yellow liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.21-7.16 (m, 2H), 7.11 (d, J = 8.0 Hz, 1H), 7.01
(s, 1H), 6.94 (d, J = 8.0 Hz, 1H), 6.84-6.80 (m, 3H), 5.24 (s, 1H),
2.28 (s, 3H), 2.19 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 145.0,
138.2, 132.3, 131.6, 129.9, 129.2, 127.2, 120.9, 119.6, 116.2,
20.7, 17.8.
CDCl3, TMS) δ 7.25 (t, J = 8.0 Hz, 1H), 7.20 (d, J = 8.0 Hz, 2H),
6.94 (s, 1H), 6.74 (d, J = 8.0 Hz, 1H), 6.03 (d, J = 8.0 Hz, 1H),
4.79 (s, 1H), 3.10 (hept, J = 6.5 Hz, 2H), 2.30 (s, 3H), 2.21 (s,
3H), 1.14 (d, J = 6.5 Hz, 12H). 13C NMR (125 MHz, CDCl3) δ
147.0, 143.7, 136.2, 131.0, 127.3, 126.8, 126.6, 123.7, 121.4,
111.7, 28.2, 24.7, 23.0, 20.3, 17.5. IR (neat) ν 3418, 2961, 2921,
2855, 2359, 1620, 1583, 1510, 1457, 1437, 1328, 1295, 1269,
1053, 871, 811, 788, 741 cm-1. HRMS (ESI) calcd for C20H28N
[M+H]+: 282.2216; found: 282.2233.
4.2.2.40 Compound 9a6b: white solid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.38-7.32 (m, 4H), 7.26 (t, J = 7.0 Hz, 1H), 7.10-
7.05 (m, 2H), 6.66 (t, J = 7.0 Hz, 1H), 6.60 (d, J = 8.0 Hz, 1H),
4.35 (s, 2H), 3.83 (s, 1H), 2.25 (s, 3H). 13C NMR (125 MHz,
CDCl3) δ 146.0, 139.5, 130.0, 128.6, 127.5, 127.2, 127.1, 121.9,
117.2, 110.0, 48.3, 17.5.
1
4.2.2.33 Compound 8l: pale yellow liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.11-7.06 (m, 2H), 7.00 (s, 1H), 6.94 (d, J = 8.0
Hz, 1H), 6.64 (d, J = 8.0 Hz, 3H), 5.19 (s, 1H), 2.28 (s, 3H), 2.26
(s, 3H), 2.18 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 144.9,
139.0, 138.3, 132.1, 131.6, 129.8, 129.0, 127.2, 120.9, 120.5,
116.9, 113.4, 21.4, 20.7, 17.7. IR (neat) ν 3371, 3021, 2915,
2855, 2365, 2346, 1603, 1590, 1504, 1491, 1312, 1159, 1113,
1033, 993, 944, 871, 814, 804, 768, 688 cm-1. HRMS (ESI) calcd
for C15H18N [M+H]+: 212.1434; found: 212.1437.
4.2.2.34 Compound 8m: pale yellow liquid. 1H NMR (500 MHz,
CDCl3, TMS) δ 7.06 (d, J = 8.0 Hz, 1H), 7.02 (d, J = 8.0 Hz,
2H), 6.99 (s, 1H), 6.92 (d, J = 8.0 Hz, 1H), 6.79 (d, J = 8.0 Hz,
2H), 5.16 (s, 1H), 2.270 (s, 3H), 2.265 (s, 3H), 2.19 (s, 3H). 13C
NMR (125 MHz, CDCl3) δ 142.2, 139.1, 131.5, 131.4, 129.7,
129.4, 128.7, 127.2, 119.5, 117.3, 20.6, 20.5, 17.7. IR (neat) ν
3385, 3021, 2921, 2855, 1607, 1507, 1298, 1119, 872, 806, 708
cm-1. HRMS (ESI) calcd for C15H18N [M+H]+: 212.1434; found:
212.1434.
1
4.2.2.41 Compound 9b6a: colorless liquid. H NMR (500 MHz,
CDCl3, TMS) δ 7.08 (t, J = 8.0 Hz, 1H), 7.02 (d, J = 7.0 Hz, 1H),
6.62-6.58 (m, 2H), 3.32-3.26 (m, 1H), 2.09-2.05 (m, 5H), 1.77-
1.73 (m, 2H), 1.66-1.62 (m, 1H), 1.42-1.33 (m, 2H), 1.28-1.14
(m, 3H). 13C NMR (125 MHz, CDCl3) δ 145.2, 130.2, 127.0,
121.5, 116.2, 110.2, 51.4, 33.6, 26.0, 25.0, 17.4.
Acknowledgments

7
Financial support from the National Natural Science
Foundation of China (No. 21471115) is greatly appreciated.
ACCEPTED MANUSCRIPT
References and notes
1. (a) Suwanprasop, S.; Nhujak, T.; Roengsumran, S.; Petsom, A.
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A. J. Tetrahedron 1999, 55, 11399-11428. (e) Industrial Organic
Chemistry, ed. Weissermel, K.; Arpe, H. J.; Wiley-VCH,
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2. For some recent selected reviews, please see: (a) Bhunia, S.;
Pawar, G. G.; Kumar, S. V.; Jiang, Y.; Ma, D. Angew. Chem. Int.
Ed. 2017, DOI: 10.1002/anie.201701690. (b) Ruiz-Castillo, P.;
Buchwald, S. L. Chem. Rev. 2016, 116, 12564-12649. (c) Bariwal,
J.; Van der Eycken, E. Chem. Soc. Rev. 2013, 42, 9283-9303. (d)
Lundgren, R. J.; Stradiotto, M. Chem. Eur. J. 2012, 18, 9758-9769.
(e) Surry, D. S.; Buchwald, S. L. Angew. Chem. Int. Ed. 2008, 47,
6338-6361. (f) Hartwig, J. F. Acc. Chem. Res. 2008, 41, 1534-
1544.
3. (a) Wong, S. M.; Yuen, O. Y.; Choy, P. Y.; Kwong, F. Y. Coord.
Chem. Rev. 2015, 293-294, 158-186. (b) Gildner, P. G.; Colacot, T.
J. Organometallics 2015, 34, 5497-5508.
4. For selected reviews on the NHC-metal complexes catalyzed
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