B(C6F5)3-Catalyzed Hydroboration of Alkenes with N-Heterocyclic Carbene Boranes via B—H Bond Activation

Article abstract of DOI:10.1002/cjoc.202000489

In this work, a novel mode for the activation of N-heterocyclic carbene boranes (NHC-boranes) was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C₆F₅)₃ in an frustrated Lewis pairs manner. A broad range of alkenes including stilbenes, β-methylstyrenes, styrenes, and alkyl-alkenes were suitable substrates for the B(C₆F₅)₃-catalyzed hydroboration to furnish the desired products in good to high yields. Significantly, excellent regioselectivities were obtained in some cases. Mechanistic studies indicate that the B—H bond cleavage is likely involved in the rate-determining step. In addition, an electrophilic addition of NHC-borenium cation to alkenes and the subsequent formation of carbocation are also postulated. The current work provides a promising method for the activation of stable borane adducts, which might lead to some interesting transformations in the future.

Full text of DOI:10.1002/cjoc.202000489

Chinese Journal
of Chemistry
CJC
中 国 化 学 - An International Journal
Accepted Article
Title: B(C6F5)3-Catalyzed Hydroboration of Alkenes with N-Heterocyclic Carbene
Boranes via B-H Bond Activation
Authors: Qiaotian Wang, Wei Meng, Xiangqing Feng,* and Haifeng Du*
This manuscript has been accepted and appears as an Accepted Article online.
This work may now be cited as: Chin. J. Chem. 2020, 38, 10.1002/cjoc.202000489.
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published online in Early View: http://dx.doi.org/10.1002/cjoc.202000489.
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Chinese Journal
of Chemistry
Frustrated Lewis pairs, B-H bond activation, Hydroboration, Stable
borane adducts, Alkenes
Report
CJC
中
国 化 学 - An International Journal
B(C6F5)3-Catalyzed Hydroboration of Alkenes with N-Heterocyclic
Carbene Boranes via B-H Bond Activation
Qiaotian Wang,a,b Wei Meng,a,b Xiangqing Feng,*,a,b and Haifeng Du*,a,b
a Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy
of Sciences, Beijing, 100190
b University of Chinese Academy of Sciences, Beijing 100049
Cite this paper: Chin. J. Chem. 2019, 37, XXX—XXX. DOI: 10.1002/cjoc.201900XXX
Summary of main observation and conclusion In this work, a novel mode for the activation of N-heterocyclic carbene boranes (NHC-boranes) was
developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C6F5)3 in an FLP manner. A broad range of
alkenes including stilbenes, β-methylstyrenes, styrenes, and alkyl-alkenes were suitable substrates for the B(C6F5)3-catalyzed hydroboration to furnish the
desired products in good to high yields. Significantly, excellent regioselectivities were obtained in some cases. Mechanistic studies indicate that the B-H
bond cleavage is likely involved in the rate-determined step. In addition, an electrophilic addition of NHC-borenium cation to alkenes and the subsequent
formation of carbocation are also postulated. The current work provides a promising method for the activation of stable borane adducts, which might
lead some interesting transformations in the future.
Moreover, Parrain and co-workers disclosed an asymmetric
Background and Originality Content
intramolecular hydroboration with chiral rhodium catalysts.12
Organoboron compounds possess an extremely broad
Despite these advances, exploring new and highly efficient
application in synthetic chemistry, material science, life and health
activation modes for NHC-boranes is still of great interest.
science, and so on.1 The construction of C-B bonds has attracted
considerable attention, and a great advance has been made in this
field.2 Notably, the hydroboration of alkenes represents one of the
most efficient and straightforward approaches for the synthesis of
organoboron compounds.3 Numerous boron reagents have been
well developed for the hydroboration, which can be categorized
into free boranes and borane adducts with weak or strong Lewis
bases. Traditional borane adducts with weak Lewis bases, such as
diethyl ether, tetrahydrofuran and dimethyl sulfide, generally
exhibited a high reactivity for the hydroboration of alkenes due to
the easy release of borane from the complexes. However, the
forming C-B bond is usually labile. A variety of stable borane
complexes have been developed by means of amines, phosphines,
and N-heterocyclic carbenes as Lewis bases.4 The relatively high
stability of borane complexes own and the resulting C-B bonds
after hydroborations make them one class of very attractive boron
reagents.
N-heterocyclic carbene boranes (NHC-boranes) are tetravalent
and neutral borane complexes, which have been widely used as
reactants, reagents, initiators, or catalysts in organic synthesis and
polymer chemistry.5-9 However, they are inert as boron reagents
toward the hydroboration of alkenes due to their difficult
decomplexation. The development of novel activation modes for
NHC-boranes is therefore essential to accomplish the desired
hydroboration. In 2012, Vedjes, Curran, and co-workers reported
the first hydroboration of alkenes 2 with NHC-borane 1 using
Tf2NH as catalyst to furnish dihydroborated products (Scheme
1).10 It is noteworthy that the hydroboration does not occur even
under harsh conditions without catalyst. NHC-borenium cation
was postulated as the reactive species, which were formed by a
H2-release reaction of NHC-borane 1 and Tf2NH (Scheme 1). Later
on, Curran and co-workers employed diiodine as activator to form
covalent boryl iodide species, which was also effective for the
hydroboration of alkenes to afford stable products 3 (Scheme 1).11
Scheme 1 Previous work and our proposal on the hydroboration of alkenes
with NHC-boranes
The chemistry of frustrated Lewis pairs (FLPs) has undergone a
rapid growth in the past decade, which provides a powerful tool
to activate a wide range of chemical bonds in a cooperative
manner.13,14 As our general interest in the FLP catalysis, we have
been devoting our efforts on the activation of H-H, Si-H, and B-H
bonds.15 In 2015, our group reported a B(C6F5)3-catalyzed transfer
hydrogenation of pyridines with ammonia borane.16 The
activation of ammonia borane was supposed to be in an FLP
manner. Later, Shi and co-workers reported a very similar work on
the transfer hydrogenation of some N-heterocylces.17 In 2016,
Ingleson and co-workers described
a
B(C6F5)3-catalyzed
trans-hydroboration of alkynes with NHC-(9-BBN) borane.18 Based
on the previous work, we envisioned that NHC-boranes 1 might be
*E-mail: fxq@iccas.ac.cn; haifengdu@iccas.ac.cn
Chin. J. Chem. 2019, 37, XXX－XXX
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First author et al.
Report
activated by B(C6F5)3 with the assistance of NHC to generate
zwitterion 5, which was likely a reactive species for the
hydroboration of alkenes (Scheme 1). Herein, we wish to report
our efforts on this subject.
these reactions proceeded well to produce the desired boranes
3a-n in 81-98% yields. Both electron-donating and withdrawing
substituents on the phenyl groups were well tolerated for this
hydroboration. When unsymmetrical stilbene 2o was employed
as a substrate, a highly regioselective hydroboration occurred to
give borane 3o as the major product with a ratio of 13/1. The
boron atom preferred to be added at the carbon atom adjacent to
the electron-deficient phenyl moieties.
Results and Discussion
The hydroboration of cis-stilbene 2a with NHC-borane 1 was
initially examined with B(C6F5)3 (10 mol %) in toluene at 60 °C for
12 h (Scheme 2). It was pleased to find that this reaction went
smoothly to afford the desired borane product 3a in 97% yield (1H
NMR yield with 1,3,5-trimethoxybenzene as an internal standard).
Scheme 2 Initial study on the hydroboration of cis-stilbene
Table 1 Optimization of reaction conditions for the hydroboration of
cis-stilbenea.
B(C6F5)3
Conc.
(M)
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
Temp.
(°C)
60
Time
(h)
12
12
12
12
12
6
Yield
(%)b
97
Entry
Solvent
(mol %)
1
2c
3
10
10
5
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
DCM
60
trace
47
60
Scheme 3 B(C6F5)3-catalyzed hydroboration of stilbenes
4
5
80
95
5
1
80
trace
99
6
5
80
7
8d
2.5
5
80
6
trace
trace
39
80
6
9
5
80
6
10
5
n-hexane
cyclohexane
80
6
81
11
5
80
6
60
a
(All reactions were carried out with 2a (0.1 mmol), NHC-borane 1 (0.15
mmol) with B(C6F5)3 (0.01 mmol) in solvent (1.0 mL) unless otherwise
b
noted.)
(It was determined by crude 1H NMR using
c
1,3,5-trimethoxybenzene as an internal standard.) (Borane Lewis acid
generated from pentafluorostyrene and HB(C6F5)2 was used.) (tBu3P (5
d
mol %) was added as Lewis base.)
The reaction condition was next optimized. As shown in Table
1, when
a borane Lewis acid generated in situ from
pentafluorostyrene and Piers’ borane HB(C6F5)2 was employed as
catalyst, no reaction occurred at all (entry 2). Lowering the
loading amount of B(C6F5)3 to 5 mol % resulted in a dramatic drop
of yield (entry 3). Raising the temperature to 80 °C gave a
satisfactory yield (entry 4). Further reducing the amount of
catalyst to 1 mol %, no product was observed (entry 5). With the
reaction concentration of 0.2 M, the reaction time can be
shortened to 6 h (entry 6). Less B(C6F5)3 (2.5 mol %) could not
Scheme 4 B(C6F5)3-catalyzed hydroboration of β-methylstyrenes
β-Methylstyrenes 2p-t were next employed as substrates for
the hydroboration. As shown in Scheme 4, all these reactions
went smoothly to afford products 3p-t in 78-87% yields.
Interestingly, the hydroboration occurred with excellent
regioselectivities and the other isomers were not observed. A
preliminary DFT calculation suggests that compounds 3p-t were
thermodynamic products (see Supporting Information). We then
turned our attention to the hydroboration of styrenes 2u-y
(Scheme 4). Distinct from the aforementioned substrates, a
dihydroboration reaction occurred to give the corresponding
products 3u-y in 73-77% yields. In comparison with the unstable
dihydroborated products obtained in the reported work10, the
obtained dihydroborated products were stable enough and could
t
promote this reaction (entry 7). Additional Lewis base Bu3P (5
mol %) would inhibit the hydroboration completely by trapping
B(C6F5)3 (entry 8). Solvents were found to have an obvious
influence on the reactivity, and toluene proven to be the optimal
one (entries 6 vs 9-11).
Due to the similar reactivity of cis- and trans-isomers, a
variety of stilbenes 2 were subjected as a mixture of cis- and
trans-isomers to the B(C6F5)3-catalyzed hydroboration with NHC
borane 1 under the optimal conditions. As shown in Scheme 3, all
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Running title
Chin. J. Chem.
be isolated through chromatography on silica gel.
Scheme 7 Control experiments on the hydroboration of cis-stilbene
Scheme 5 B(C6F5)3-catalyzed hydroboration of styrenes
In addition, alkyl-alkenes were also investigated for the
hydroboration
reaction.
As
shown
in
Scheme
6,
tetramethylethene (6a) was an effective substrate for this
reaction to afford the desired product 7a in 86% yield. The
hydroboration of cyclic alkenes 6b-d also proceeded well to
furnish products 7b-d in 64-77% yields.
Scheme 8 KIE studies on the hydroboration of cis-stilbene
Kinetic studies were next performed to understand the
hydroboration process. Significant kinetic isotope effects (KIE,
kH/kD = 3.8 and 3.0, respectively) were observed for the
hydroboration of cis-stilbene (2a) with NHC-boranes 1 and 1d
through both parallel and completion reactions (Scheme 8),
suggesting that the B-H bond cleavage is probably involved in the
rate-determining step.20
Scheme 6 B(C6F5)3-catalyzed hydroboration of alkyl olefins
The mixture of B(C6F5)3 and NHC-BH3 (1) (1 equiv.) in 0.5 mL
CD2Cl2 was heated at 80 °C for 6 h, to which one equivalent
amount of cis-stilbene (cis-2a) was added, to our surprise, instead
of the desired hydroboration, an isomerization reaction occurred
rapidly to afford trans-stilbene (trans-2a) (Scheme 7a). A further
1H NMR study was therefore performed by mixing compound 3a
and B(C6F5)3 together in toluene-d8. It was found that a
retrohydroboration reaction happened to afford trans-stilbene
(Scheme 7b). Interestingly, when NHC-borane 1 was introduced
to the mixture, the retrohydroboration process was inhibited
(Scheme 7c). These results indicate that B(C6F5)3 likely promotes
the retrohydroboration reaction and the excess amount of
NHC-borane probably inhibits this process through an interaction
with B(C6F5)3.19
Figure 1 Kinetic studies.
(a) Hammett plot of different stilbenes. (b) Plot of kobs against the
concentration of B(C6F5)3. (c) Plot of kobs against the concentration of
NHC-borane 1. (d) Plot of kobs against the concentration of cis-stilbene
Chin. J. Chem. 2019, 37, XXX－XXX
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First author et al.
Report
(2a).
Experimental
General information
Hammett studies were further carried out, and a negative
All air-sensitive compounds were handled under an
slope (ρ = -1.121) was obtained (Figure 1a). It is indicated that the
electrophilic addition of NHC-borenium cation to alkenes and the
subsequent formation of carbocation are likely involved in the
hydroboration. The plot of kobs against [B(C6F5)3] or [NHC-BH3] was
found to be a straight line as shown in Figures 1b and 1c,
suggesting the hydroboration is first-order kinetics in both
B(C6F5)3 catalyst and NHC-borane. In addition, as shown in Figure
1d, hydroborations with different amounts of cis-stilbene were
found to have similar reaction rates, indicating zero-order kinetics
in substrate 2a. These kinetic results provide an additional
support for the involving of the B-H bond cleavage in the
rate-determined step.
Based on all the experimental and mechanistic results, a
plausible catalytic cycle is outlined in Figure 2. In cycle A, Lewis
acid B(C6F5)3 (4) activates NHC-borane 1 through a hydride
abstraction in an FLP manner to form zwitterion 5. An
electrophilic addition of NHC-borenium cation to alkenes occurs
to generate zwitterion 8 composed of carbocation and HB-(C6F5)3.
After the hydride transfer, product 3 is formed, and B(C6F5)3
catalyst is regenerated to complete the catalytic cycle. An
alternative pathway via the direct hydride-transfer from
NHC-borane 1 to zwitterion 8 is also proposed (cycle B), in which
B(C6F5)3 acts as an initiator instead of a catalyst. A control
experiment for the hydroboration of cis-stilbene 2a with
[Ph3C][B(C6F5)4] (5 mol %) gave the desired product in a full
conversion, which provides a support for this pathway.21
atmosphere of argon or in a nitrogen-filled glovebox. 1H NMR, 13
C
NMR, 11B NMR and 19F NMR spectra were recorded on Bruker AV
400 and Bruker AV 500 at ambient temperature with CDCl3,
CD2Cl2 and toluene-d8 as solvent and TMS as internal standard.
Chemical shifts (δ) were given in ppm, referenced to the residual
proton resonance of TMS (0) or to the carbon resonance of the
CDCl3 (77.23). Coupling constants (J) were given in Hertz (Hz). All
solvents were purified by conventional methods, distilled before
use. Commercially available reagents were used without further
purification. All the substrates were synthesized according to
reported method.
General procedure for the hydroboration of stilbenes or alkyl
olefins (Scheme 3 or 6)
To a sealed-tube were added stilbenes 2 or alkyl olefins 6 (0.5
mmol), B(C6F5)3 (0.0128 g, 0.025 mmol), NHC-BH3 (1) (0.0825 g,
0.75 mmol) and dry toluene (2.5 mL) in a nitrogen atmosphere
glovebox. After being sealed, the resulting mixture was stirred at
80 °C for 6 h. The reaction mixture was then cooled to room
temperature, and the solvent was removed under vacuum. The
crude residue was purified by flash chromatography on silica gel
using petroleum ether/ethyl acetate (10/1, v/v) as the fluent to
give the desired products 3a-o and 7.
General procedure for the hydroboration of β-methylstrenes
(Scheme 4)
To a sealed-tube were added β-methylstrenes 2p-t (0.6 mmol),
B(C6F5)3 (0.0128 g, 0.025 mmol), NHC-BH3 (1) (0.0550 g, 0.5 mmol)
and dry toluene (2.5 mL) in a nitrogen atmosphere glovebox.
After being sealed, the resulting mixture was stirred at 80 °C for 6
h. The reaction mixture was cooled to room temperature, and the
solvent was removed under vacuum. The crude residue was
purified by flash chromatography on silica gel using petroleum
ether/ethyl acetate (10/1, v/v) as the fluent to give the desired
products 3p-t.
General procedure for the hydroboration of styrenes (Scheme 5)
To a sealed-tube were added styrenes 2u-y (1.2 mmol),
B(C6F5)3 (0.0128 g, 0.025 mmol), NHC-BH3 (1) (0.0550 g, 0.5 mmol)
and dry toluene (2.5 mL) in a nitrogen atmosphere glovebox.
After being sealed, the resulting mixture was stirred at 80 °C for 6
h. The reaction mixture was cooled to room temperature, and the
solvent was removed under vacuum. The crude residue was
purified by flash chromatography on silica gel using petroleum
ether/ethyl acetate (10/1, v/v) as the fluent to give the desired
products 3u-y.
Figure 2 Plausible catalytic cycle.
Conclusions
A hydroboration of alkenes with stable NHC-borane has been
achieved using B(C6F5)3 as catalyst. A quite wide range of alkenes,
including stilbenes, β-methylstyrenes, styrenes, and alkyl-alkenes,
were all suitable substrates for the hydroboration to furnish the
desired products in 64-98% yields. Notably, excellent
regioselectivities were obtained for the hydroboration of
β-methylstyrenes, and dihydroboration occurred for the styrene
substrates. Mechanistic studies indicate that the activation of
NHC-borane with B(C6F5)3 is likely through a hydride abstraction in
an FLP manner to form the reactive zwitterion species. KIE and
kinetic studies suggest that the B-H cleavage is probably involved
in the rate-determined step, and the electrophilic addition of
borenium cation to alkenes and the formation of carbocation may
be involved in the hydroboration. The current work provides a
novel mode for the activation of stable borane adducts. Further
efforts on the activation of B-H bond and the asymmetric
hydroboration with chiral boron Lewis acids are underway in our
laboratory.
Characterization of products
(1,3-Dimethyl-1H-imidazol-3-ium-2-yl)(1,2-diphenylethyl)dihy
droborate (3a): white solid, 0.1408 g, 96% yield, m.p. 106-109 °C;
1
IR (film): 3020, 2920, 2850, 2286, 1596, 1488 cm-1; H NMR (500
MHz, CDCl3, ppm) δ 7.19-7.08 (m, 4H), 7.05-6.95 (m, 3H),
6.89-6.77 (m, 2H), 6.62 (s, 2H), 3.33 (s, 6H), 3.24-3.04 (m, 2H),
2.30 (s, 1H); 13C NMR (125 MHz, CDCl3, ppm) δ 153.6, 145.5, 128.9,
127.6, 127.5, 126.8, 124.6, 122.5, 119.9, 42.7, 35.5; 11B NMR (160
MHz, CDCl3, ppm) δ -22.6 (t, JB-H = 86.9 Hz); HRMS (ESI) calcd. for
C19H23N2BNa [M+Na]+: 313.1847, Found: 313.1850.
(1,2-Di-p-tolylethyl)(1,3-dimethyl-1H-imidazol-3-ium-2-yl)dihy
droborate (3b): white solid, 0.1493 g, 93% yield, m.p. 81-83 °C; IR
1
(film): 2920, 2286, 1508, 1265, 1065 cm-1; H NMR (500 MHz,
CDCl3, ppm) δ 7.04 (d, J = 7.5 Hz, 2H), 6.92 (d, J = 8.0 Hz, 2H), 6.81
(d, J = 7.5 Hz, 2H), 6.71 (d, J = 8.0 Hz, 2H), 6.62 (s, 2H), 3.34 (s, 6H),
3.17-2.95 (m, 2H), 2.25 (s, 1H), 2.22 (s, 3H), 2.19 (s, 3H); 13C NMR
(125 MHz, CDCl3, ppm) δ 150.4, 142.4, 133.6, 131.3, 128.7, 128.3,
128.1, 126.6, 119.9, 42.3, 35.5, 21.0, 20.9; 11B NMR (160 MHz,
CDCl3, ppm) δ -22.7 (t, JB-H = 86.7 Hz); HRMS (ESI) calcd. for
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Running title
Chin. J. Chem.
C21H27N2BNa [M+Na]+: 341.2160, Found: 341.2159.
yield, m.p. 121-123 °C; IR (film): 3389, 2920, 2848, 2325, 1325,
1
(1,2-Bis(4-ethylphenyl)ethyl)(1,3-dimethyl-1H-imidazol-3-ium-
2-yl)dihydrobor-ate (3c): white solid, 0.1641 g, 94% yield, m.p.
1109 cm-1; H NMR (400 MHz, CDCl3, ppm) δ 7.38 (d, J = 8.0 Hz,
2H), 7.33-7.14 (m, 4H), 6.90 (d, J = 7.6 Hz, 2H), 6.70 (s, 2H), 3.37 (s,
6H), 3.20 (d, J = 7.6 Hz, 2H), 2.37 (s, 1H); 13C NMR (125 MHz, CDCl3,
ppm) δ 157.8, 148.9, 128.9, 127.1 (q, JC-F = 32.1 Hz), 126.6, 125.0
101-103 °C; IR (film): 2961, 2920, 2289, 1266 cm-1; H NMR (400
1
MHz, CDCl3, ppm) δ 7.09 (d, J = 7.6 Hz, 2H), 6.96 (d, J = 7.6 Hz, 2H),
6.84 (d, J = 7.6 Hz, 2H), 6.73 (d, J = 7.6 Hz, 2H), 6.60 (s, 2H), 3.31 (s, (q, JC-F = 32.0 Hz), 124.8 (q, JC-F = 271.7 Hz), 124.7 (q, JC-F = 272.2
6H), 3.21-2.99 (m, 2H), 2.60-2.40 (m, 4H), 2.27 (s, 1H), 1.23-1.07
(m, 6H); 13C NMR (100 MHz, CDCl3, ppm) δ 150.8, 142.8, 140.1,
138.1, 128.7, 127.1, 126.9, 126.6, 119.9, 42.2, 35.4, 28.4, 28.3,
16.1, 15.7; 11B NMR (160 MHz, CDCl3, ppm) δ -22.7 (t, JB-H = 89.3
Hz); HRMS (ESI) calcd. for C23H31N2BNa [M+Na]+: 369.2473, Found:
369.2473.
(1,2-Bis(4-(tert-butyl)phenyl)ethyl)(1,3-dimethyl-1H-imidazol-
3-ium-2-yl)di-hydroborate (3d): white solid, 0.1897 g, 94% yield,
m.p. 79-82 °C; IR (film): 3449, 2961, 2286, 1477, 1267, 1066 cm-1;
1H NMR (400 MHz, CDCl3, ppm) δ 7.17-7.00 (m, 4H), 6.96 (d, J =
8.0 Hz, 2H), 6.68 (d, J = 8.0 Hz, 2H), 6.42 (s, 2H), 3.15 (s, 6H),
3.13-2.88 (m, 2H), 2.20 (s, 1H), 1.16 (s, 18H); 13C NMR (100 MHz,
CDCl3, ppm) δ 149.8, 145.9, 143.9, 141.5, 127.4, 125.0, 123.4,
123.2, 118.8, 40.7, 34.2, 33.1, 33.0, 30.6, 30.4; 11B NMR (160 MHz,
CDCl3, ppm) δ -22.5 (t, JB-H = 86.2 Hz); HRMS (ESI) calcd. for
C27H38N2B [M-H]-: 401.3134, Found: 401.3126.
Hz), 124.6 (q, JC-F = 3.8 Hz),124.4 (q, JC-F = 3.5 Hz), 120.2, 42.2, 35.5;
19F NMR (377 MHz, CDCl3, ppm) δ -61.7, -62.1; 11B NMR (160 MHz,
CDCl3, ppm) δ -22.6 (t, JB-H = 87.4 Hz); HRMS (ESI) calcd. for
C21H20N2BF6 [M-H]-: 425.1629, Found: 425.1639.
(1,2-Di-m-tolylethyl)(1,3-dimethyl-1H-imidazol-3-ium-2-yl)dih
ydroborate (3j): white solid, 0.1544 g, 96% yield, m.p. 75-77 °C; IR
1
(film): 3021, 2920, 2286, 1601, 1481, 1265 cm-1; H NMR (500
MHz, CDCl3, ppm) δ 6.96-6.85 (m, 3H), 6.84-7.77 (m, 1H), 6.74 (d,
J = 7.5 Hz, 1H), 6.59 (d, J = 7.0 Hz, 1H), 6.57-6-51 (m, 2H), 6.46 (s,
2H), 3.21 (s, 6H), 3.11-2.86 (m, 2H), 2.18 (s, 1H), 2.15 (s, 3H), 2.07
(s, 3H); 13C NMR (125 MHz, CDCl3, ppm) δ 153.7, 145.5, 136.8,
136.5, 129.8, 127.7, 127.5, 127.4, 125.9, 125.4, 123.8, 123.2,
119.9, 42.6, 35.4, 21.5(7), 21.5(5); 11B NMR (128 MHz, CDCl3, ppm)
δ -22.9 (t, JB-H = 86.9 Hz); HRMS (ESI) calcd. for C21H27N2BNa
[M+Na]+: 341.2160, Found: 341.2159.
(1,2-Bis(3-methoxyphenyl)ethyl)(1,3-dimethyl-1H-imidazol-3-i
um-2-yl)dihydro-borate (3k): colorless oil, 0.1669 g, 95% yield, IR
(1,2-Bis(4-methoxyphenyl)ethyl)(1,3-dimethyl-1H-imidazol-3-i
um-2-yl)dihydro-borate (3e): yellow oil, 0.1719 g, 98% yield, IR
1
(film): 2920, 2850, 2288, 1596, 1482, 1264, 748 cm-1; H NMR
1
(film): 3448, 1652, 1264, 1119 cm-1; H NMR (500 MHz, CDCl3,
(500 MHz, CDCl3, ppm) δ 7.01-6.97 (m, 1H), 6.94-6.85 (m, 1H),
6.75 (d, J = 7.5 Hz, 1H), 6.71 (s, 1H), 6.57 (s, 2H), 6.56-6.52 (m, 2H),
6.47-6.34 (m, 3H), 3.65 (s, 3H), 3.63 (s, 3H), 3.32 (s, 6H), 3.17-3.00
(m, 2H), 2.29 (s, 1H); 13C NMR (125 MHz, CDCl3, ppm) δ 159.2,
159.1, 155.4, 147.1, 128.5, 128.2, 121.4, 120.0, 119.6, 114.4,
112.3, 110.2, 108.0, 55.0, 54.9, 42.8, 35.5; 11B NMR (128 MHz,
CDCl3, ppm) δ -22.7 (t, JB-H = 87.2 Hz); HRMS (ESI) calcd. for
C21H27O2N2Na [M+Na]+: 373.2058, Found: 373.2058.
ppm) δ 7.04 (d, J = 8.5 Hz, 2H), 6.73 (d, J = 9.0 Hz, 2H), 6.66 (d, J =
8.5 Hz, 2H), 6.61 (s, 2H), 6.58 (d, J = 8.5 Hz, 2H), 3.68(9) (s, 3H),
3.68(6) (s, 3H), 3.36 (s, 6H), 3.02 (d, J = 7.5 Hz, 2H), 2.19 (s, 1H);
13C NMR (125 MHz, CDCl3, ppm) δ 156.8, 155.5, 145.6, 137.7,
129.6, 127.5, 120.0, 113.0, 112.9, 55.2, 55.1, 42.3, 35.5; 11B NMR
(128 MHz, CDCl3, ppm) δ -22.9 (t, JB-H = 86.5 Hz); HRMS (ESI) calcd.
for C21H27O2N2BNa [M+Na]+: 373.2058, Found: 373.2055.
(1,2-Bis(4-fluorophenyl)ethyl)(1,3-dimethyl-1H-imidazol-3-ium
-2-yl)dihydro-borate (3f): yellow solid, 0.1561 g, 95% yield, m.p.
(1,2-Bis(3-chlorophenyl)ethyl)(1,3-dimethyl-1H-imidazol-3-iu
m-2-yl) dihydro-borate (3l): yellow oil, 0.1675 g, 93% yield, IR
1
1
103-106 °C; IR (film): 2921, 2849, 2286, 1503, 1266 cm-1; H NMR
(film): 3057, 2928, 2850, 2286, 1076 cm-1; H NMR (400 MHz,
(400 MHz, CDCl3, ppm) δ 7.12-6.97 (m, 2H), 6.85-6.67 (m, 6H),
CDCl3, ppm) δ 7.05 (s, 1H), 7.00-6.88 (m, 3H), 6.88-6.81 (m, 1H),
6.76 (d, J = 8.0 Hz, 1H), 6.69 (s, 1H), 6.63 (d, J = 7.6 Hz, 1H), 6.55 (s,
2H), 3.29 (s, 6H), 2.98 (d, J = 7.6 Hz, 2H), 2.18 (s, 1H); 13C NMR
(100 MHz, CDCl3, ppm) δ 155.6, 147.0, 133.4, 133.2, 128.9, 128.8,
128.7, 127.1, 126.7, 125.0, 124.9, 122.7, 120.2, 42.3, 35.5; 11B
NMR (160 MHz, CDCl3, ppm) δ -23.0 (t, JB-H = 87.7 Hz); HRMS (APCI)
calcd. for C19H22N2BCl2 [M+H]+: 359.1248, Found: 359.1249.
(1,2-Bis(3,5-dimethylphenyl)ethyl)(1,3-dimethyl-1H-imidazol-3
-ium-2-yl) dihydroborate (3m): white solid, 0.1705 g, 98% yield,
6.66 (s, 2H), 3.39 (s, 6H), 3.15-2.93 (m, 2H), 2.20 (s, 1H); 13C NMR
(100 MHz, CDCl3, ppm) δ 161.2 (d, JC-F = 118.7 Hz), 158.8 (d, JC-F
=
116.5 Hz), 148.6 (d, JC-F = 2.9 Hz), 140.7, 129.9 (d, JC-F = 7.4 Hz),
127.7 (d, JC-F = 7.1 Hz), 120.1, 114.2 (d, JC-F = 20.6 Hz), 114.0 (d, JC-F
= 20.3 Hz), 42.4, 35.5; 19F NMR (377 MHz, CDCl3, ppm) δ -119.6,
-122.2; 11B NMR (128 MHz, CDCl3, ppm) δ -23.0 (t, JB-H = 86.9 Hz);
HRMS (APCI) calcd. for C19H22N2BF2 [M+H]+: 327.1839, Found:
327.1839.
(1,2-Bis(4-chlorophenyl)ethyl)(1,3-dimethyl-1H-imidazol-3-iu
m-2-yl)dihydro-borate (3g): white solid, 0.1727 g, 96% yield, m.
p.113-115 °C; IR (film): 2920, 2850, 2286, 1488, 1265, 1090 cm-1;
1H NMR (400 MHz, CDCl3, ppm) δ 7.13-7.01 (m, 4H), 6.97 (d, J =
8.4 Hz, 2H), 6.74 (d, J = 8.4 Hz, 2H), 6.67 (s, 2H), 3.39 (s, 6H),
3.17-2.86 (m, 2H), 2.23 (s, 1H); 13C NMR (100 MHz, CDCl3, ppm) δ
151.7, 143.5, 130.2, 130.1, 128.1, 127.8, 127.7, 127.5, 120.1, 42.2,
35.6; 11B NMR (160 MHz, CDCl3, ppm) δ -22.8 (t, JB-H = 88.0 Hz);
HRMS (ESI) calcd. for C19H20N2BCl2 [M-H]-: 357.1102, Found:
357.1099.
1
m.p. 129-131 °C; IR (film): 2914, 2285, 1595, 1479, 1266 cm-1; H
NMR (400 MHz, CDCl3, ppm) δ 6.80 (s, 2H), 6.66 (s, 1H), 6.59 (s,
2H), 6.51 (s, 1H), 6.45 (s, 2H), 3.33 (s, 6H), 3.13-2.88 (m, 2H), 2.24
(s, 1H), 2.20 (s, 6H), 2.13 (s, 6H); 13C NMR (100 MHz, CDCl3, ppm) δ
150.8, 142.8, 140.1, 138.1, 128.7, 127.1, 126.9, 126.6, 119.9, 42.2,
35.4, 28.4, 28.3, 16.1, 15.7; 11B NMR (160 MHz, CDCl3, ppm) δ
-23.0 (t, JB-H = 86.8 Hz); HRMS (ESI) calcd. for C23H31N2BNa
[M+Na]+: 369.2473, Found: 369.2475.
(1,2-Bis(3,5-dimethoxyphenyl)ethyl)(1,3-dimethyl-1H-imidazol
-3-ium-2-yl) dihydroborate (3n): yellow oil, 0.1906 g, 92% yield, IR
1
(1,2-Bis(4-bromophenyl)ethyl)(1,3-dimethyl-1H-imidazol-3-iu
m-2-yl)dihydro-borate (3h): white solid, 0.2157 g, 96% yield, m.p.
(film): 2937, 2316, 1591, 1147 cm-1; H NMR (400 MHz, CDCl3,
ppm) δ 6.63 (s, 2H), 6.35 (s, 2H), 6.14 (s, 1H), 6.04 (s, 2H), 6.01 (s,
1H), 3.66 (s, 6H), 3.62 (s, 6H), 3.39 (s, 6H), 3.16-2.94 (m, 2H), 2.25
(s, 1H). 13C NMR (100 MHz, CDCl3, ppm) δ 160.1, 156.4, 147.8,
1
135-137 °C; IR (film): 3056, 2307, 1485, 1266 cm-1; H NMR (500
MHz, CDCl3, ppm) δ 7.22 (d, J = 8.5 Hz, 2H), 7.11 (d, J = 8.5 Hz, 2H),
6.98 (d, J = 8.5 Hz, 2H), 6.70 (d, J = 8.5 Hz, 2H), 6.68 (s, 2H), 3.39 (s, 120.0, 106.9, 104.8, 97.0, 95.1, 55.0(9), 55.0(7), 43.0, 35.5; 11B
6H), 3.15-2.90 (m, 2H), 2.20 (s, 1H); 13C NMR (125 MHz, CDCl3,
NMR (128 MHz, CDCl3, ppm) δ -22.9 (t, JB-H = 85.5 Hz); HRMS (ESI)
calcd. for C23H31O4N2BNa [M+Na]+: 433.2269, Found: 433.2266.
(1-(3,5-Bis(trifluoromethyl)phenyl)-2-(3,5-dimethoxyphenyl)et
ppm) δ 152.2, 143.9, 130.6, 130.5, 130.4, 128.6, 120.1, 118.4,
115.7, 42.1, 35.6; 11B NMR (160 MHz, CDCl3, ppm) δ -22.8 (t, JB-H
=
88.6 Hz); HRMS (ESI) calcd. for C19H20N2BBr2 [M-H]-: 445.0092,
Found: 445.0101.
hyl)(1,3-dimethyl-1H-imidazol-3-ium-2-yl)dihydroborate
(3o):
colorless oil, 0.2147 g, 88% yield, IR (film): 2955, 2839, 2294, 1595,
1277, 1128 cm-1; 1H NMR (500 MHz, CDCl3, ppm) δ 7.39 (s, 1H),
7.26 (s, 2H), 6.70 (s, 2H), 6.26 (s, 2H), 6.16 (s, 1H), 3.66 (s, 6H),
(1,2-Bis(4-(trifluoromethyl)phenyl)ethyl)(1,3-dimethyl-1H-imi
dazol-3-ium-2-yl)dihydroborate (3i): white solid, 0.1730 g, 81%
Chin. J. Chem. 2019, 37, XXX－XXX
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de

First author et al.
Report
3.42 (s, 6H), 3.14-3.00 (m, 2H), 2.48 (s, 1H); 13C NMR (125 MHz,
6.57 (s, 2H), 3.41 (s, 6H), 2.62-2.45 (m, 1H), 2.27 (s, 3H), 2.19 (s,
3H), 2.15-2.04 (m, 1H), 2.02-1.87 (m, 1H), 1.30 (d, J = 6.8 Hz, 3H),
CDCl3, ppm) δ 159.3, 155.4, 145.5, 129.2 (q, JC-F = 32.9 Hz), 125.7,
122.8 (q, JC-F = 270.9 Hz), 119.3, 115.1 (q, JC-F = 3.8 Hz), 105.7, 96.4, 1.17-0.95 (m, 1H), 0.93-0.66 (m, 1H); 13C NMR (125 MHz, CDCl3,
54.0, 41.5, 34.5; 19F NMR (377 MHz, CDCl3, ppm) δ -62.7; 11B NMR
(128 MHz, CDCl3, ppm) δ -22.5 (t, JB-H = 90.2 Hz); HRMS (ESI) calcd.
for C23H24BF6N2O2 [M-H]-: 485.1841, Found: 485.1826.
ppm) δ 153.1, 145.2, 133.8, 131.2, 128.6, 127.9, 127.8, 125.9,
120.2, 37.4, 36.0, 21.2, 21.0, 20.8; 11B NMR (128 MHz, CDCl3, ppm)
δ -14.3 (d, JB-H = 83.3 Hz); HRMS (ESI) calcd. for C23H31N2BNa
[M+Na]+: 369.2473, Found: 369.2473.
Bis(4-chlorophenethyl)(1,3-dimethyl-1H-imidazol-3-ium-2-yl)h
ydroborate (3w): colorless oil, 0.1405 g, 73% yield, IR (film): 3442,
1636, 1265 cm-1; 1H NMR (400 MHz, CDCl3, ppm) δ 7.13 (d, J = 8.0
Hz, 2H), 7.03 (d, J = 8.4 Hz, 2H), 6.95 (d, J = 8.4 Hz, 2H), 6.70 (d, J =
8.4 Hz, 2H), 6.60 (s, 2H), 3.42 (s, 6H), 2.59-2.44 (m, 1H), 2.20-2.08
(m, 1H), 2.01-1.90 (m, 1H), 1.33-1.23 (m, 3H), 1.15-0.95 (m, 1H),
0.84-0.69 (m, 1H); 13C NMR (100 MHz, CDCl3, ppm) δ 153.9, 145.3,
129.0, 128.2, 126.8, 126.4, 126.2, 119.4, 36.0, 35.0, 19.9; 11B NMR
(128 MHz, CDCl3, ppm) δ -14.4 (d, JB-H = 85.0 Hz); HRMS (ESI) calcd.
for C21H24N2BCl2 [M-H]-: 385.1415, Found: 385.1419.
Bis(4-bromophenethyl)(1,3-dimethyl-1H-imidazol-3-ium-2-yl)
hydroborate (3x): colorless oil, 0.1783 g, 75% yield, IR (film): 3349,
2921, 1645, 1265 cm-1; 1H NMR (400 MHz, CDCl3, ppm) δ 7.28 (d, J
= 8.4 Hz, 2H), 7.09 (d, J = 8.4 Hz, 2H), 6.97 (d, J = 8.0 Hz, 2H), 6.65
(d, J = 8.4 Hz, 2H), 6.57 (s, 2H), 3.40 (s, 6H), 2.59-2.39 (m, 1H),
2.19-2.05 (m, 1H), 2.00-1.87 (m, 1H), 1.37-1.17 (m, 3H), 1.16-0.91
(m, 1H), 0.85-0.64 (m, 1H); 13C NMR (100 MHz, CDCl3, ppm) δ
154.5, 145.8, 129.7, 129.1, 128.7, 126.7, 119.4, 117.0, 114.2, 36.1,
35.0, 19.8; 11B NMR (128 MHz, CDCl3, ppm) δ -14.4 (d, JB-H = 84.7
Hz); HRMS (ESI) calcd. for C21H24N2BBr2 [M-H]-: 473.0405, Found:
473.0402.
(1,3-Dimethyl-1H-imidazol-3-ium-2-yl)(1-phenylpropyl)dihydr
oborate (3p): white solid, 0.0995 g, 87% yield, m.p. 81-84 °C; IR
(film): 3448, 2306, 1617, 1266 cm-1; 1H NMR (400 MHz, CDCl3,
ppm) δ 7.03-6.89 (m, 2H), 6.86-6.76 (m, 1H), 6.70 (d, J = 7.6 Hz,
2H), 6.59 (s, 2H), 3.28 (s, 6H), 1.84-1.63 (m, 3H), 0.83 (t, J = 6.8 Hz,
3H); 13C NMR (100 MHz, CDCl3, ppm) δ 154.6, 127.5, 126.7, 122.2,
119.9, 35.4, 29.3, 14.8; 11B NMR (128 MHz, CDCl3, ppm) δ -23.0 (t,
JB-H = 86.5 Hz); HRMS (ESI) calcd. for C14H21N2BNa [M+Na]+:
251.1690, Found: 251.1691.
(1,3-Dimethyl-1H-imidazol-3-ium-2-yl)(1-(p-tolyl)propyl)dihydr
oborate (3q): yellow oil, 0.1005 g, 83% yield, IR (film): 3449, 2951,
2275, 1266 cm-1; 1H NMR (500 MHz, CDCl3, ppm) δ 6.85 (d, J = 7.5
Hz, 2H), 6.68 (d, J = 7.5 Hz, 2H), 6.67 (s, 2H), 3.37 (s, 6H), 2.23 (s,
3H), 1.87-1.67 (m, 3H), 0.89 (t, J = 7.0 Hz, 3H); 13C NMR (125 MHz,
CDCl3, ppm) δ 150.2, 130.2, 127.1, 125.5, 118.8, 34.5, 28.4, 19.8,
13.7; 11B NMR (128 MHz, CDCl3, ppm) δ -23.1 (t, JB-H = 86.1 Hz);
HRMS (ESI) calcd. for C15H23N2BNa [M+Na]+: 265.1847, Found:
265.1845.
(1,3-Dimethyl-1H-imidazol-3-ium-2-yl)(1-(4-methoxyphenyl)pr
opyl)dihydro-borate (3r): yellow oil, 0.1101 g, 85% yield, IR (film):
1
3446, 2275, 1636, 1266 cm-1; H NMR (500 MHz, CDCl3, ppm) δ
6.71 (d, J = 8.5 Hz, 2H), 6.67 (s, 2H), 6.64 (d, J = 8.5 Hz, 2H),
3.85-3.71 (m, 1H), 3.74 (s, 3H), 3.40 (s, 6H), 1.75 (s, 2H), 0.88 (t, J
= 6.5 Hz, 3H); 13C NMR (125 MHz, CDCl3, ppm) δ 154.4, 145.6,
126.3, 118.8, 112.0, 54.3, 34.5, 28.7, 13.7; 11B NMR (128 MHz,
CDCl3, ppm) δ -23.2 (t, JB-H = 86.1 Hz); HRMS (ESI) calcd. for
C15H23ON2BNa [M+Na]+: 281.1796, Found: 281.1795.
(1,3-Dimethyl-1H-imidazol-3-ium-2-yl)bis(3-methylphenethyl)
hydroborate (3y): colorless oil, 0.1258 g, 73% yield, IR (film): 3057,
1
2357, 1265 cm-1; H NMR (500 MHz, CDCl3, ppm) δ 7.12-7.05 (m,
1H), 6.97-6.91 (m, 2H), 6.90-6.84 (m, 2H), 6.66 (d, J = 7.5 Hz, 1H),
6.60 (s, 1H), 6.57 (s, 2H), 6.56 (d, J = 7.5 Hz, 2H), 3.40 (s, 6H),
2.62-2.49 (m, 1H), 2.28 (s, 3H), 2.16 (s, 3H), 2.15-2.06 (m, 1H),
2.00-1.91 (m, 1H), 1.39-1.28 (m, 3H), 1.16-0.97 (m, 1H), 0.87-0.73
(m, 1H); 13C NMR (125 MHz, CDCl3, ppm) δ 155.2, 147.1, 136.2,
135.3, 127.7, 126.8, 126.1, 125.7, 124.3, 123.9, 121.9, 121.8,
119.1, 36.8, 34.9, 20.4, 19.8; 11B NMR (128 MHz, CDCl3, ppm) δ
-14.2 (d, JB-H = 84.6 Hz); HRMS (ESI) calcd. for C23H31N2BNa
[M+Na]+: 369.2473, Found: 369.2469.
(1-(4-Bromophenyl)propyl)(1,3-dimethyl-1H-imidazol-3-ium-2
-yl)dihydroborate (3s): white solid, 0.1329 g, 87% yield, m.p.
1
101-103 °C; IR (film): 3449, 2951, 2342, 1641, 1265 cm-1; H NMR
(500 MHz, CDCl3, ppm) δ 7.15 (d, J = 8.5 Hz, 2H), 6.70 (s, 2H), 6.69
(d, J = 7.0 Hz, 4H), 3.40 (s, 6H), 1.85-1.65 (m, 3H), 0.86 (t, J = 7.0
Hz, 3H); 13C NMR (125 MHz, CDCl3, ppm) δ 152.8, 129.3, 127.5,
119.0, 114.2, 34.5, 28.3, 13.6; 11B NMR (128 MHz, CDCl3, ppm) δ
-23.0 (t, JB-H = 86.9 Hz); HRMS (ESI) calcd. for C14H20BrN2BNa
[M+Na]+: 329.0795, Found: 329.0792.
(1,3-Dimethyl-1H-imidazol-3-ium-2-yl)(2,3-dimethylbutan-2-yl
)dihydroborate (7a): colorless oil, 0.0834 g, 86% yield, IR (film):
1
(1-(4-Iodophenyl)propyl)(1,3-dimethyl-1H-imidazol-3-ium-2-yl
)dihydroborate (3t): yellow solid, 0.1389 g, 78% yield, m.p.
2949, 2849, 2275, 1457, 1323, 1139 cm-1; H NMR (400 MHz,
CDCl3, ppm) δ 6.82 (s, 2H), 3.78 (s, 6H), 0.89 (d, J = 6.8 Hz, 6H),
0.65 (s, 6H); 13C NMR (100 MHz, CDCl3) δ 120.3, 39.8, 36.7, 28.3,
19.0; 11B NMR (160 MHz, CDCl3, ppm) δ -23.8 (t, JB-H = 83.7 Hz);
HRMS (ESI) calcd. for C6H13O3N2BNa [M+Na]+: 195.0922, Found:
195.0920.
1
85-87 °C; IR (film): 3167, 2948, 2855, 2287, 1479, 1109 cm-1; H
NMR (400 MHz, CDCl3, ppm) δ 7.27 (d, J = 8.0 Hz, 2H), 6.63 (s, 2H),
6.51 (d, J = 8.4 Hz, 4H), 3.23 (s, 6H), 1.79-1.57 (m, 3H), 0.78 (t, J =
6.8 Hz, 3H); 13C NMR (125 MHz, CDCl3, ppm) δ 153.6, 135.2, 128.1,
119.0, 84.9, 34.5, 28.2, 13.6; 11B NMR (128 MHz, CDCl3, ppm) δ
-22.9 (t, JB-H = 86.9 Hz); HRMS (ESI) calcd. for C14H19N2BI [M-H]-:
353.0681, Found: 353.0677.
Cyclohexyl(1,3-dimethyl-1H-imidazol-3-ium-2-yl)dihydroborat
e (7b): colorless oil, 0.0738 g, 77% yield, IR (film): 3160, 3111,
1
2909, 2243, 1479 cm-1; H NMR (500 MHz, CDCl3, ppm) δ 6.80 (s,
(1,3-Dimethyl-1H-imidazol-3-ium-2-yl)diphenethylhydroborat
e (3u): colorless oil, 0.1177 g, 74% yield, IR (film): 3402, 2329,
2H), 3.77 (s, 6H), 1.84-0.93 (m, 12H), 0.53 (s, 1H); 13C NMR (100
MHz, CDCl3, ppm) δ 120.0, 36.2, 36.1, 29.1, 27.7; 11B NMR (128
MHz, CDCl3, ppm) δ -24.1 (t, JB-H = 83.2 Hz); HRMS (ESI) calcd. for
C11H21N2BNa [M+Na]+: 215.1690, Found: 215.1690.
1
1645, 1266 cm-1; H NMR (400 MHz, CDCl3, ppm) δ 7.22-7.15 (m,
2H), 7.15-7.01 (m, 2H), 7.09-7.02 (m, 1H), 7.02-6.94 (m, 2H),
6.88-6.81 (m, 1H), 6.77 (d, J = 7.6 Hz, 2H), 6.55 (s, 2H), 3.39 (s, 6H),
2.68-2.50 (m, 1H), 2.23-2.06 (m, 1H), 2.06-1.92 (m, 1H), 1.41-1.28
(m, 3H), 1.20-0.97 (m, 1H), 0.93-0.73 (m, 1H); 13C NMR (100 MHz,
Cycloheptyl(1,3-dimethyl-1H-imidazol-3-ium-2-yl)dihydrobora
te (7c): yellow solid, 0.0663 g, 64% yield, m. p. 63-66 °C; IR (film):
1
3462, 2906, 2253, 1264 cm-1; H NMR (500 MHz, CDCl3, ppm) δ
CDCl3, ppm) δ 156.4, 148.1, 127.9(3), 127.9(0), 127.3, 125.9, 124.5, 6.74 (s, 2H), 3.70 (s, 6H), 1.67-0.97 (m, 14H), 0.63 (s, 1H); 13C NMR
122.2, 120.3, 37.9, 36.0, 20.9; 11B NMR (128 MHz, CDCl3, ppm) δ
-14.2 (d, JB-H = 84.4 Hz); HRMS (ESI) calcd. for C21H27N2BNa
[M+Na]+: 341.2160, Found: 341.2161 .
(125 MHz, CDCl3, ppm) δ 120.0, 37.4, 36.1, 29.6, 28.8; 11B NMR
(160 MHz, CDCl3, ppm) δ -23.8 (t, JB-H = 83.6 Hz); HRMS (ESI) calcd.
for C12H23N2BNa [M+Na]+: 229.1847, Found: 229.1848.
(1,3-Dimethyl-1H-imidazol-3-ium-2-yl)bis(4-methylphenethyl)
Cycloctyl(1,3-dimethyl-1H-imidazol-3-ium-2-yl)dihydroborate
hydroborate (3v): colorless oil, 0.1336 g, 77% yield, IR (film): 3374, (7d): white solid, 0.0818 g, 74% yield, m.p. 48-51 °C; IR (film):
2920, 2850, 1645 cm-1; 1H NMR (400 MHz, CDCl3, ppm) δ
7.09-6.96 (m, 4H), 6.80 (d, J = 8.0 Hz, 2H), 6.67 (d, J = 7.6 Hz, 2H),
2920, 2275, 1752, 1266, 1086 cm-1; 1H NMR (400 MHz, CDCl3, ppm)
δ 6.73 (s, 2H), 3.70 (s, 6H), 1.81-1.07 (m, 16H), 0.72 (s, 1H); 13C
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Chin. J. Chem. 2019, 37, XXX－XXX

Running title
Chin. J. Chem.
NMR (100 MHz, CDCl3, ppm) δ 120.0, 36.1, 34.8, 28.0, 27.7, 26.9;
11B NMR (160 MHz, CDCl3, ppm) δ -23.7 (t, JB-H = 83.7 Hz); HRMS
(ESI) calcd. for C13H24N2B [M-H]-: 219.2038, Found: 219.2032.
Chem. Soc. 2019, 141, 12355-12361; (d) Prokofjevs, A.; Kampf, J. W.;
Solovyev, A.; Curran, D. P.; Vedejs, E. Weakly Stabilized Primary
Borenium Cations and Their Dicationic Dimers. J. Am. Chem. Soc.
2013, 135, 15686–15689; (e) Radcliffe, J. E.; Fasano, V.; Adams, R. W.;
You, P.; Ingleson, M. J. Reductive α-Borylation of α,β-Unsaturated
Esters Using NHC–BH3 Activated by I2 as a Metal-Free Route to
α-Boryl Esters. Chem. Sci. 2019, 10, 1434–1441; (f) Shimoi, M.;
Watanabe, T.; Maeda, K.; Curran, D. P.; Taniguchi, T. Radical
trans-Hydroboration of Alkynes with N-Heterocyclic Carbene
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Dong, J.; Liu, X.; Gao, L.; Zhao, Y.; Xie, J.; Li, S.; Zhu, C.
Photoredox-Controlled β-Regioselective Radical Hydroboration of
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Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2018xxxxx.
Acknowledgement
We are grateful for the financial support from the National
Natural Science Foundation of China (21871269 and 21521002).
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(The following will be filled in by the editorial staff)
Manuscript received: XXXX, 2019
Manuscript revised: XXXX, 2019
Manuscript accepted: XXXX, 2019
Accepted manuscript online: XXXX, 2019
Version of record online: XXXX, 2019
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Entry for the Table of Contents
Page No.
B(C6F5)3-Catalyzed Hydroboration of Alkenes
with N-Heterocyclic Carbene Boranes Via B-H
Bond Activation
Qiaotian Wang; Wei Meng; Xiangqing Feng*;
Haifeng Du*
B(C6F5)3-catalyzed hydroboration of alkenes with N-heterocyclic carbene boranes (NHC-boranes)
was successfully realized by the activation of NHC-boranes in an FLP manner for generating the
highly reactive zwitterion species to furnish the desired organoboron products in good to high
yields.
a Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of
Molecular Recognition and Function, Institute of Chemistry, Chinese
Academy of Sciences, Beijing, 100190
E-mail: fxq@iccas.ac.cn; haifengdu@iccas.ac.cn
b University of Chinese Academy of Sciences, Beijing 100049
Chin. J. Chem. 2018, template
© 2018 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim