Ni-catalyzed hydroboration and hydrosilylation of olefins with diboron and silylborane

Article abstract of DOI:10.1016/j.tetlet.2018.06.024

Herein we report a Ni-catalyzed formal hydroboration of olefins, which afforded anti-Markovnikov-type alkylboranes with B₂pin₂ and a stoichiometric amount of water. Formal hydrosilylation using air- and moisture-sensitive silylborane

Full text of DOI:10.1016/j.tetlet.2018.06.024

Accepted Manuscript
Ni-Catalyzed hydroboration and hydrosilylation of olefins with diboron and si-
lylborane
Toshiyuki Kamei, Sohshi Nishino, Toyoshi Shimada
PII:
S0040-4039(18)30767-6
https://doi.org/10.1016/j.tetlet.2018.06.024
TETL 50062
DOI:
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
17 March 2018
5 June 2018
8 June 2018
Please cite this article as: Kamei, T., Nishino, S., Shimada, T., Ni-Catalyzed hydroboration and hydrosilylation of
olefins with diboron and silylborane, Tetrahedron Letters (2018), doi: https://doi.org/10.1016/j.tetlet.2018.06.024
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical Abstract
To create your abstract, type over the instructions in the template box below.
Fonts or abstract dimensions should not be changed or altered.
Ni-Catalyzed hydroboration and
hydrosilylation of olefins with diboron and
silylborane
Leave this area blank for abstract info.
Toshiyuki Kamei, Sohshi Nishino, Toyoshi Shimada

1
Tetrahedron Letters
Ni-Catalyzed hydroboration and hydrosilylation of olefins with diboron and
silylborane
Toshiyuki Kamei, Sohshi Nishino, and Toyoshi Shimada
a
Department of Chemical Engineering, National Institute of Technology, Nara College, 22 Yata-cho, Yamatokoriyama, Nara, 639-1080, Japan.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Herein we report a Ni-catalyzed formal hydroboration of olefins, which afforded anti-
Markovnikov-type alkylboranes with B2pin2 and a stoichiometric amount of water. Formal
hydrosilylation using air- and moisture-sensitive silylboranes also proceeded under optimized
conditions. The reaction with trans-stilbene and D2O resulted in 1,2-H migration, which
suggested that the reaction proceeded via -hydride elimination and reinsertion mechanisms.
Available online
2009 Elsevier Ltd. All rights reserved.
Keywords:
Hydroboration
Hydrosilylation
Nickel
-elimination and reinsertion mechanism
bis(pinacolato)diboron
Alkene hydroboration is one of the powerful synthetic tools to
synthesize alkylboranes, which can serve as valuable reagents in
various transformations.1 For example, Suzuki-Miyaura coupling,
a powerful tool to construct carbon-carbon bonds, has been
applied to the synthesis of materials and biologically active
compounds.2
olefins using stoichiometric amount of water as Brønsted acid
under neutral conditions (Scheme 1c).
Our first attempt at Ni-catalyzed formal hydroboration was
performed with trans-stilbene (1a) as the model olefin. In the
presence of Ni(cod)2, 1,2-dicyclohexylphosphinoethane (dcype),
and trifluoroethanol (TFE), hydroboration proceeded to afford
the product 2a in 89% yield (Table 1, entry 1). The Ni catalyst
could not be replaced with other Ni precursors, such as NiCl2 and
NiBr2 (entries 2 and 3). The reaction performed with Ni(acac)2 to
give the product 2a in 40% yield (entry 4) Starting materials
were recovered in the absence of any Ni precursor or ligand
(entries 5 and 6).
In general, hydroboranes HB(OR)2, such as catechol borane
and pinacol borane, have been adopted for catalytic
hydroboration, since the first catalytic hydroboration was
4
reported using Wilkinson’s catalyst.3 On the other hand, B2(pin)2
has emerged as a useful borylating reagent for metal-catalyzed
formal hydroboration with the aid of a Brønsted acid proton
source.5-10 Formal hydroboration should be performed under
basic conditions, although the reaction has been promoted by
many metal catalysts, including those based on Rh,5 Cu,6 Pd,7 Pt,8
and Fe.9 The basic conditions sometimes restricts the substrate
scope of the reaction.
Scheme 1. Ni-Catalyzed hydroboration of olefins with B2pin2
A few examples of Ni-catalyzed hydroboration have been
reported in the past decade. The first example of Ni-catalyzed
hydroboration across activated olefins under basic conditions was
reported by Yorimitsu and Oshima (Scheme 1a).11,12 Recently,
Wang and Ye have reported a base-free hydroboration protocol
using Ni(cod)2/P(t-Bu)3 catalyst in methanol (Scheme 1b).13,14 In
their reaction, a large amount of methanol was required to
accelerate the protonation of the alkylnickel intermediate, which
made the reaction unsuitable for proton-sensitive substrates. To
expand the substrate scope of the reaction, the amount of
Brønsted acid used should be reduced. In this study, we have
Ni-catalyzed formal hydroboration across simple
a—ch—iev—ed
 Corresponding author. e-mail: kamei@chem.nara-k.ac.jp

2
Tetrahedron
The ligands that showed good hydroboration performance
result show the formation of benzylnickel species after
borylnickelation were the key to regioselective hydroboration.
were next investigated. The monodentate ligand, PCy3, improved
the yield of 2a (entry 7). However, electron-rich and bulky
carbene ligands, IMes and IPr, gave poor results (entries 8 and 9).
Bidentate ligands, dppe and 2,2’-bipyridine, also reduced the
efficiency of reaction (entries 10 and 11).
Table 2. Ni-Catalyzed hydroboration of styrenesa
Addition of acetic acid as the proton source could not drive
the reaction due to decomposition of the Ni catalyst under
strongly acidic conditions (entry 12). Weaker proton sources,
such as PhOH, HFIP, IPA, and H2O, gave excellent results
(entries 13–16). We chose H2O as the best proton source because
of its availability and cost-effectiveness. The reaction
temperature could be reduced to 60 ºC to give 2a in 95% yield
(entry 17). However, the reaction did not occur at lower
temperatures, and the starting materials were recovered (entry
18). The reaction could be scaled up under the optimum
conditions, albeit in lower yield (76%).
Table 1. Screening of reaction conditions of hydroboration
entry
1
Ni cat.
Ni(cod)2
NiCl2
ligand
dcype
dcype
dcype
dcype
dcype
–
additive
TFE
TFE
TFE
TFE
TFE
TFE
TFE
TFE
TFE
TFE
TFE
AcOH
PhOH
HFIP
IPA
temp (oC)
80
yield(%)a
89
2
80
0
3
NiBr2
80
0
4
Ni(acac)2
–
80
40
5
80
0
6
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
Ni(cod)2
80
0
7
PCy3b
IMesb
IPrb
80
99
Scheme 2. Hydroboration with 1-decene
8
80
0
9
80
0
10
11
12
13
14
15
16
17
18
dppe
80
0
5
Bipy
80
PCy3b
PCy3b
PCy3b
PCy3b
PCy3b
PCy3b
PCy3b
80
0
Table 3. Ni-catalyzed hydrosilylation of styrenesa
80
99
80
99
80
99
H2O
80
99
H2O
60
99 (95)c
H2O
40
<5
a NMR yield using Me3SiOSiMe3 as internal standard, b using 20 mol% of
ligand, c isolated yield
With the optimum conditions of Ni-catalyzed hydroboration in
hand, the scope of this reaction in terms of alkene substrates was
studied (Table 2). The reaction with cis-stilbene (1a’) gave 2a in
93% yield. The reactions with electron-rich (1c, 1d), electron-
deficient (1e), and sterically hindered (1f) styrene derivatives
should be performed at 100 ºC for full conversion due to their
low reactivities to give the corresponding anti-Markovnikov
adducts in high yields. Other - and -substituted styrenes (1g-
1i) also show high reactivity towards hydroboration to afford the
corresponding products 2g-2i. Since proton sensitive groups were
tolerated under the reaction condition, styrenes 1j and 1k
afforded the corresponding products in good yield.
To show the advantage of the reaction described here, the
scope of borane nucleophiles was expanded using
phenyl(dimethyl)silyl pinacol borate,15 which is a useful but
moisture-sensitive silylating reagent, instead of B2pin2. Treatment
of silylborane with trans-stilbene in the presence of Ni(cod)2,
PCy3, B2pin2, and H2O realized formal hydrosilylation to afford
the alkylsilane 3a in 76% yield as the sole product.16-18 Similar to
hydroboration, 2,4,6-trimethylstyrene 1f was converted to the
corresponding anti-Markovnikov adduct 3f. The reaction with 1-
decene 1j resulted in highly regioselective hydrosilylation to give
Hydroboration with 1-decene (1l) also gave the product in
good yield, albeit as a mixture of regioisomers (Scheme 2). This

3
6917. (b) Vogels, C. M.; Westcott, S. A. Curr. Org. Chem. 2005,
the 3j and 3j’ (linear:branched=11:1). In all cases, no
hydroboration product was observed.
9, 687. (c) Huang, S.; Xie, Y.; Wu, S.; Jia, M.; Wang, J.; Xu, W.;
Fang, H. Curr. Org. Synth. 2013, 10, 683. (d) Burgess, K.;
Ohlmeyer, M. J. Chem. Rev. 1991, 91, 1179. (e) Beletskaya, I.;
Pelter, A. Tetrahedron, 1997, 53, 4957.
To obtain mechanistic insights of Ni-catalyzed hydroboration,
D-labeling experiment was performed on 1a by addition of D2O
at 60 ºC to give 2a-D in 84% yield (Scheme 3). Surprisingly,
deuterium atom was introduced at the -position of the boryl
group (92%-D incorporation), and D-scrambling reactions of
other hydrogen atoms were not observed. Since no other proton
sources were added, the two benzylic hydrogen atoms of 2a-D
originated from 1a, implying that 1,2-H migration proceeded via
-hydride elimination and reinsertion. Recently, Xiao and Bin
observed similar 1,2-H atom migration during Ni-catalyzed 1,1-
diboration of alkene derivatives.19
2. (a) Miyaura, N.; Suzuki, A.; Chem. Rev. 1995, 95, 2457. (b)
Hongbo, L.; Johansson Seechurn, C. C. C.; Colacot, T. J.; ACS.
Catal. 2012, 2, 1147.
3. Männig, D.; Nöth, H.; Angew. Chem. Int. Ed. Engl. 1985, 24, 878.
4. Neeve, E. C.; Geier, S. J.; Mkhalid, I. A. I, Westcott, S. A.; Marder,
T. B. Chem. Rev. 2016, 116, 9091
5. (a) Kabalka, G. W.; Das, B. C.; Das, S. Tetrahedron Lett. 2002, 43,
2323. (b) Shiomi, T.; Adachi, T.; Toribatake, K.; Zhou, L.;
Nishiyama, H. Chem. Commun. 2009, 5987.
6. (a) Wang, Z.; He, X.; Zhang, R.; Zhang, G.; Xu, G.; Zhang, Q.;
Xiong, T.; Zhang, Q. Org. Lett. 2017, 19, 3067. (b) Kerchner, H.
A.; Montgomery, J.; Org. Lett. 2016, 18, 5760. (c) Iwamoto, H.;
Kubota, K.; Ito, H. Chem. Commun, 2016, 52, 5916. (d) Hong, S.;
Liu, M.; Zhang, W.; Zeng, Q.; Deng, W.; Tetrahedron Lett. 2015,
56, 2297. (e) Xie, J.-B.; Lin, S.; Luo, J.; Wu, J.; Winn, T. R.; Li, G.
Org. Chem. Front. 2015, 2, 42. (f) He, Z.-T.; Zhao, Y.-S.; Tian, P.;
Wang, C.-C.; Dong, H.-Q.; Lin, G.-Q. Org. Lett. 2014, 16, 1426.
(g) Chen, I.-H.; Yin, L.; Itano, W.; Kanai, M.; Shibasaki, M. J. Am.
Chem. Soc. 2009, 131, 11664. (h) Mun, S.; Lee, J.-E.; Yun, J. Org.
Lett. 2006, 8, 4887. (i) Ito, H.; Yamanaka, H.; Tateiwa, J.; Hosomi,
A. Tetrahedron Lett. 2000, 41, 6821. (j) Sole, C.; Bonet, A.; de
Vries, A. H. M.; de Vries, J. G. Lefort, L.; Gulyás, H.; Fernández,
E. Organometallics, 2012, 31, 7855.
Scheme 3. D-Labeling experiment
Scheme 4. Plausible reaction pathway
7. Lillo, V, Geier, M. J.; Westcott, S. A.; Fernández, Org. Biomol.
Chem. 2009, 7, 4674.
8. (a) Abu Ali, H.; Goldberg, I.; Srebnik, M. Organometallics, 2001,
20, 3962. (b) Bell, N. J.; Cox, A. J.; Cameron, N. R.; Evans, S. O.;
Marder, T. B.; Dulin, M. A.; Elsevier, C. J.; Baucherel, X.; Tulloch,
A. A. D.; Tooze, R. P. Chem. Commun. 2004, 1854. (c) Lauson, Y.
G.; Lesley, M. J. G.; Norman, N. C.; Rice, C. R.; Marder, T. B.
Chem. Commun. 1997, 2051.
9. (a) Liu, Y.; Zhou, Y.; Wang, H.; Qu, J. RSC Adv. 2015, 5, 73705.
(b) Bonet, A.; Sole, C.; Gulyás, H.; Fernández, E. Chem. – Asian J.
2011. 6, 1011.
10. Transitionmetal-free hydroboration. (a) Lee, K.-S.; Zhugralin, A. R.
Hoveyda, A. H.; J. Am. Chem. Soc. 2009, 131, 7253. (b) Yang, K.;
Song, Q.; Green Chem. 2016, 18, 932. (c) Wu, H.; Garcia, J. M.
Haeffner F.; Radomkit, S.; Zhugralin, A. R.; Hoveyda, A. H. J. Am.
Chem. Soc. 2015, 137, 10585. (d) Wu, H.; Radomkit, S.; O’Brien, J.
M.; Hoveyda, A. H.; J. Am. Chem. Soc. 2012, 134, 8277. (e)
Rodomkit, S.; Hoveyda, A. H. Angew. Chem., Int. Ed., 2014, 53,
3387.
11. (a) Hirano, K.; Yorimitsu, H.; Oshima, K.; Org. Lett. 2007, 9, 5031.
(b) ref. 7
12. Other example of metal-catalyzed formal hydroboration under
neutral or acidic condition: (a) Smith, J. R.; Collins, B. S. L.;
Hesse, M. J. Graham, M. A. Myers, E. L. Aggarwal, V. K. J. Am.
Chem. Soc. 2017, 139, 9148. (b) Huang, J.; Yan, W.; Tan, C.; Wu,
W.; Jiang, H. Chem. Commun. 2018, 54, 1770. (c) Hu, N.; Zhao,
G.; Zhang, Y.; Liu, X.; Li, G.; Tang, W. J. Am. Chem. Soc. 2015,
137, 6746.
13. Li, J.-F.; Wei, Z.-Z.; Wang, Y.-Q.; Ye, M.; Green Chem. 2017, 19,
4498.
14. Brown reported Ni-catalyzed hydroboration in his mechanistic
study. Logan, K. M.; Sardini, S. R.; White, S. D.; Brown, M. K. J.
Am. Chem. Soc. 2018, 140, 159.
Our proposed mechanisms are shown in Scheme 5, based on
the experiments conducted in this study and in Xiao and Bin’s
study. Oxidative addition of B2pin2 to nickel generated a boryl
nickel species, which underwent olefin insertion into the B–Ni
bond, following -hydride elimination from the alkyl nickel
species. Reinsertion of alkenylborane into the H–Ni bond
produced an -boryl nickel species, which was protonated with
water to afford the product.20,21
In conclusion, we developed
a
Ni-catalyzed formal
15. Oestreich, M.; Hartmann, E. Mewald, M. Chem. Rev. 2013, 113,
402.
hydroboration of olefins with B2pin2 and water. The addition of
stoichiometric amount of water as the proton source under
neutral conditions enabled the use of other organoborane
nucleophiles. Ni-catalyzed formal hydrosilylation was achieved
using air- and moisture-sensitive PhMe2SiBpin instead of B2pin2.
D-Labeling experiment indicated that the reaction proceeded via
-hydride elimination and reinsertion pathways. Further
investigation to improve the catalyst activity in terms of the
regioselectivity of less-hindered olefins and application of this
methodology is currently in progress.
16. Rh-catalyzed silyl conjugate addition (a) Walter, C.; Auer, G.;
Oestreich, M. Angew. Chem., Int. Ed. 2006, 45, 5675. (b) Walter,
C.; Oestreich, M. Angew. Chem., Int. Ed. 2008, 47, 3818. (c)
Hartmann, E.; Oestreich, M. Org. Lett. 2012, 14, 2406.
17. Cu-catalyzed silyl conjugate addition (a) Calderone, J. A.; Santos,
W. L. Org. Lett. 2012, 14, 2090. (b) Lee, K.-S. Hoveyda, A. H. J.
Am. Chem. Soc. 2010, 132, 2898. (c) Welle, A.; Petrignet, J.;
Tinant, B.; Wouters, J.; Riant, O. Chem.; –Eur. J. 2010, 16, 10980.
(c) Ibrahem, I.; Santoro, S.; Himo, F.; Córdova, A. Adv. Synth.
Catal. 2011, 353, 245. (d) Kitanosono, T.; Zhu, L.; Liu, C.; Xu, P.;
Kobayashi, S. J. Am. Chem. Soc. 2015, 137, 15422. (e) Pace, V.;
Rae, J. P. Proctor, D. J. Org. Lett. 2014, 16, 476.
References and notes
18. Metal-free silyl conjugate addition (a) O’Brien, J. M.; Hoveyda, A.
H. J. Am. Chem. Soc. 2011, 133, 7712. (b) ref. 10c
1. Selected review on metal-catalyzed hydroboration, see: (a) Evans,
19. Lei, L.; Tianjun, G.; Xi, L.; Bin, X.; Yao, F. Nat. Commun. 2017, 8,
345.
D. A.; Fu, G. C.; Hoveyda, A. H. J. Am. Chem. Soc. 1988, 110,

4
Tetrahedron
20. When the reaction were performed in shorter period (for 12 h),
Supplementary Material
the mixture of reactants and product was obtained.
21. Ni-PCy3 with HBpin for hydroboration of styrene derivatives:
Touney, E. E.; Hoveln, R. V.; Buttke, C. T.; Freidberg, M. D.;
Guzei, I. A.; Schomaker, J. M. Organometallics, 2016, 35, 3436.
Detailed experimental procedures and spectral data (PDF)

5
Highlights

Ni-Catalyzed formal hydroboration with
B2pin2 in the presence of H2O as proton source
Ni-Catalyzed formal hydroboration with
PhMe2SiBpin in the presence of H2O as proton
source



These reactions were applicable to aryl- and
alkyl olefins.
The reaction proceeded via -hydride
elimination/reinsertion pathway determined by
D-labeling experiment.