Nickel-catalyzed highly selective hydrovinylation of α-ketals of vinylarenes

Article abstract of DOI:10.1002/adsc.200800158

A nickel-catalyzed hydrovinylation of α-ketal derivatives of vinylarenes has been developed, providing a new method for preparing functional olefins with a quarternary carbon center in high yields and selectivities.

Full text of DOI:10.1002/adsc.200800158

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DOI: 10.1002/adsc.200800158
Nickel-Catalyzed Highly Selective Hydrovinylation of a-Ketals of
Vinylarenes
Qi Zhang,a Shou-Fei Zhu,a Xiang-Chen Qiao,a Li-Xin Wang,a and Qi-Lin Zhoua,*
a
State Key Laboratory and Institute of Elemento-organicChemistry, Nankai University, Tianjin 300071, Peopleꢀs Republic
of China
Fax : (+86)-22-2350-6177; e-mail: qlzhou@nankai.edu.cn
Received: March 15, 2008; Revised: April 22, 2008; Published online: June 13, 2008
Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/.
Abstract: A nickel-catalyzed hydrovinylation of a-
ketal derivatives of vinylarenes has been developed,
providing a new method for preparing functional
olefins with a quarternary carbon center in high
yields and selectivities.
methyl acrylate. In the ruthenium hydride complex-
catalyzed hydrovinylation of a,b-unsaturated ketones
and esters Yi et al.[4] gained the hydrovinylation prod-
ucts with a double bond migration. Palladium[5] and
nickel[6] catalysts with different ligands were also
tested in the hydrovinylation of various functionalized
olefins, however, low conversions or poor selectivities
were generally obtained. As part of an effort to
search for efficient catalysts for the hydrovinylation
of functionalized olefins, herein we report a highly se-
lective nickel-catalyzed hydrovinylation of a-ketal de-
rivatives of vinylarenes.
À
Keywords: C C bond formation; functionalized
olefins; hydrovinylation; nickel
Carbon-carbon bond formation is the essence of or-
ganicsynthesis and provides the foundation for gener-
The hydrovinylation of 2-(1-phenylvinyl)-1,3-dioxo-
lane (1a) was performed in CH2Cl2 at room tempera-
ating complicated organic compounds from simpler ture using a nickel catalyst generated in situ from 2.5
ones. The transition metal-catalyzed hydrovinylation mol% [NiACTHER(UNG allyl)Br]2, 5 mol% ligand, and 6 mol%
reaction (Scheme 1), the addition of a vinyl group and NaBArF.[7] Firstly, the effect of phosphorus ligands
was examined. With the ligand PPh3, a 90% conver-
sion with 75% yield of hydrovinylation product (se-
lectivity) and oligomers[8] were obtained (Table 1,
entry 1). Very high selectivity (98%) was achieved by
using the electron-rich trialkylphosphine ligand PACHTREUNG(n-
Scheme 1.
Bu)3, but the conversion of reaction was low (40%)
(entry 2). The negligible conversion in the reaction
a hydrogen atom across a double bond, is an atom- with the ligand PCy3 indicated that a sterically hin-
economical carbon-carbon bond formation reaction.[1] dered phosphine ligand is unfavourable for the hydro-
Owing to the abundant availability of starting materi- vinylation of 1a (entry 3). Systematicmodification of
als the hydrovinylation reacion has received increas- the ligand PPh3 revealed that the phosphonite L2 was
ing attention in the fine chemical and pharmaceutical the best choice of ligand, affording the hydrovinyla-
industries. In the past decades, several transition tion product in full conversion and 97% selectivity
metal catalysts have been developed for hydrovinyla- (entry 8). Use of two equivalents of ligand L2 or one
tion of unfunctionalized olefins such as vinylarenes, equivalent of a bidentate phosphine ligand such as
a-alkylvinylarenes, strained olefins and 1,3-dienes.[2] dppe[9] impeded the reaction, which showed that the
However, the examples of successful hydrovinylation active catalyst provides only one coordinating site for
of functionalized olefins, which would provide syn- the ligand in the nickel-catalyzed hydrovinylation re-
thetically useful multifunctional compounds, are limit- action.[1] The presence of the additive NaBArF is nec-
ed. In 1965, Alderson and co-workers[3] reported a hy- essary for the current reaction. No conversion was ob-
drovinylation of methyl acrylate catalyzed by rhodium served in the hydrovinylation of 1a without NaBArF.
or ruthenium at high temperature and obtained a
Various a-ketal derivatives of vinylarenes were ex-
mixture of hydrovinylation product and the dimer of amined to extend the substrate scope of the reaction.
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Qi Zhang et al.
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Table 1. Ni-catalyzed hydrovinylation with different li-
A
Table 2. Ni-catalyzed hydrovinylation of a-ketal derivatives
gands.[a]
of vinylarenes.[a]
Entry Substrate
Products Yield
Select.
[%][b] [%][c]
1
2
3
4
5
6
7
8
R=Ph 1a
2a
2b
2c
2d
2e
2f
2g
2h
2i
94
92
83
89
97
96
95
92
82
76
93
88
83
96
95
97
R=4-MeC6H4 1b
R=4-MeOC6H4 1c
R=4-ClC6H4 1d
R=4-BrC6H4 1e
R=4-FC6H4 1f
R=4-PhC6H4 1g
R=3-MeOC6H4 1h
R=3-ClC6H4 1i
R=3-BrC6H4 1j
82
Entry Ligand
Time [h][b] Conv. [%][b] Select. [%][b]
91[d]
88
1
2
3
4
5
6
7
8
PPh3
(nBu)3
PCy3
4
4
4
2
2
2
2
2
90
40
<5
96
99
100
91
100
75
98
-
94
93
78
97
97
87
PA
9
88[d]
91
10
11
12
2j
PPh
PPh
(OPh)
R=3,4-diMeC6H3 1k 2k
R=2-naphthyl 1l 2l
83
87
PA
L1
L2
[a]
The reaction conditions were the same as those in
Table 1, entry 8. All reactions were completed within 3 h
unless otherwise noted. For details of operation and anal-
ysis, see Supporting Information.
Isolated yield.
Determined by GC (HP-5 column).
[a]
Reaction
conditions:
[Ni]
(0.04 mmol),
ligand
(0.04 mmol), NaBArF (0.048 mmol), 1a (0.8 mmol), eth-
ylene (1 atm), CH2Cl2 (5 mL).
Determined by GC with HP-5 column.
[b]
[c]
[d]
[b]
Contains oligomers.
All 2-(1-arylvinyl)-1,3-dioxolane substrates with sub-
stituents at the para- or meta-position of phenyl ring the asymmetrichydrovinylation of substrate 1a cata-
gave satisfactory results under the standard conditions lyzed by [Ni(allyl)Br]2/A(Sa,R,R)-SIPHOS-PE/NaBArF,
A
CHTREUNG
(Table 2, entries 1–12). The presence of an electron- the product 2a was isolated in a yield of 75%, but
withdrawing group in the substrate slightly reduced with only 24% ee (Scheme 3). The a-ketals of styr-
the selectivity of the hydrovinylation reaction, with enes are sterically similar to a-isopropylstyrene,
the 2-[1-(4-fluorophenyl)vinyl]-1,3-dioxolane (1f) which affords high enantioselectivity (99% ee) in the
being the least selective substrate (entry 6). When the hydrovinylation reaction under similar conditions.
phenyl ring of substrate contained two strong elec- The low enantioselectivity of the a-ketal of styrene is
tron-withdrawing groups at the 3,5-positions, no con- possibly due to the weak coordination of the oxygen
version of substrate was observed. Replacement of atom of the substrate to the metal of catalyst.
the phenyl group of 1a with 2-phenylethyl led to for-
The double bond and ketal group existing in the hy-
mation of the double bond-migration compound as a drovinylation products provide a good opportunity
major product (date not shown). The olefins with a for further functional group transformations. As an
1,3-propanediol ketal 1m and a dimethanol ketal 1n example, compound 2a was converted easily to the
were less active compared to the substrate 1a. The homoallylicalochol
3 by deprotection[10] and reduc-
methyl allyl ether 1o was also examined in this reac- tion.[11] The alcohol 3 was oxidized successively with
tion, and 30% of the double bond-migration product ozone and hydrogen peroxide to a-methyltropicacid
was obtained along with the desired hydrovinylation (4), a key intermediate for the synthesis of antispas-
product 2o (Scheme 2). However, vinylarenes with modics (Scheme 4).[12]
other functional groups such as a-formylstyrene, a-
In summary, an efficient nickel-catalyzed hydrovi-
acetamidostyrene and a-pyrrolidinylmethylstyrene nylation of a-ketal derivatives of vinylarenes was de-
were inert to this reaction under identical conditions. veloped. This reaction provides a practically useful
The asymmetricversion of this reaction was tested
and atom-economic method for the construction of
by using a spirophosphoramidite ligand (Sa,R,R)- multifunctional compounds with a quaternary carbon
SIPHOS-PE, which was highly enantioselective in the center. Further studies including the hydrovinylation
asymmetrichydrovinylation of a-alkylstyrene.[2g] In of other functionalized olefins are in progress.
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Nickel-Catalyzed Highly Selective Hydrovinylation of a-Ketals of Vinylarenes
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Scheme 2.
(3.0 mL) were added into a Schlenk tube equipped with a
stirring bar. The mixture was stirred at room temperature
for 1 min and transferred to another Schlenk tube contain-
ing NaBArF (48 mmol) and CH2Cl2 (2.0 mL). After stirring
for 5 min. The inert atmosphere in the Schlenk tube was re-
placed by ethylene three times and the a-ketal derivative of
the vinylarene was introduced. The reaction mixture was
stirred at room temperature for an appropriate time (moni-
tored by GC). After the reaction had gone to completion,
the selectivity for the product was determined by GC (HP-5
column). The reaction mixture was concentrated under re-
duced pressure, and the residue was chromatographed on
silica gel column to give the pure product. The analytical
data of the products are listed in the Supporting Informa-
tion.
Scheme 3.
Acknowledgements
We thank the National Natural Science Foundation of China
(20532010, 20721062, 20702025), the Major Basic Research
Development Program (Grant No. 2006CB806106), the
“111” project (B06005) of the Ministry of Education of
China for financial support.
Scheme 4.
References
Experimental Section
[1] For reviews, see: a) P. W. Jolly, G. Wilke, in: Applied
Homogeneous Catalysis with Organometallic Com-
pounds, Vol. 2, (Eds.: B. Cornils, W. A. Herrmann),
Wiley-VCH, New York, 1996, pp 1024–1048; b) L. J.
Goossen, Angew. Chem. 2002, 114, 3929–3932; Angew.
Chem. Int. Ed. 2002, 41, 3775–3778; c) T. V. RajanBa-
bu, Chem. Rev. 2003, 103, 2845–2860.
General Procedure for Catalytic Hydrovinylation of
a-Ketal Derivatives of Vinylarenes
Under a nitrogen atmosphere, [NiCAHTRE(UGN allyl)Br]2 (20 mmol), the
phosphorus ligand (40 mmol) and fresh distilled CH2Cl2
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Qi Zhang et al.
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[2] For recent representative examples, see: a) H. Park,
T. V. RajanBabu, J. Am. Chem. Soc. 2002, 124, 734–
735; b) G. Franciꢂ, F. Faraone, W. Leitner, J. Am.
Chem. Soc. 2002, 124, 736–737; c) Z. J. He, C. S. Yi,
W. A. Donaldson, Org. Lett. 2003, 5, 1567–1569; d) R.
Kumareswaran, M. Nandi, T. V. RajanBabu, Org. Lett.
2003, 5, 4345–4348; e) A. Zhang, T. V. RajanBabu,
Org. Lett. 2004, 6, 1515–1517; f) A. Zhang, T. V. Rajan-
Babu, J. Am. Chem. Soc. 2006, 128, 54–55; g) W. J. Shi,
Q. Zhang, J. H. Xie, S. F. Zhu, G. H. Hou, Q. L. Zhou,
J. Am. Chem. Soc. 2006, 128, 2780–2781; h) A. Zhang,
T. V. RajanBabu, J. Am. Chem. Soc. 2006, 128, 5620–
5621; i) M. M. P. Grutters, C. Mꢃller, D. Vogt, J. Am.
Chem. Soc. 2006, 128, 7414–7415.
[5] a) M. G. Barlow, M. J. Bryant, R. N. Haszeldine, A. G.
Mackie, J. Organomet. Chem. 1970, 21, 215–226; b) A.
Grabulosa, G. Muller, J. I. Ordinas, A. Mezzetti, M. ꢄ.
Maestro, M. Font-Bardia, X. Solans, Organometallics
2005, 24, 4961–4973.
[6] G. Muller, J. I. Ordinas, J. Mol. Catal. A: Chem. 1997,
125, 97–108.
[7] BArFÀ =tetrakis
ACHTRE[UNG 3,5-bis(trifluoromethyl)phenyl]borate.
[8] Oligomers=the oligomerization products of substrate
with more than one ethylene molecule.
[9] dppe=1,2-bis(diphenylphosphino)ethane.
[10] S. Poulain, N. Noiret, L. Fauconnot, C. Nugier-Chauvin,
H. Patin, Tetrahedron 1999, 55, 3595–3604.
[11] T. Kametani, K. Kawamura, M. Tsubuki, T. Honda,
Chem. Pharm. Bull. 1985, 33, 4821–4828.
[12] M. C. Lu, L. B. Shih, H. S. Jae, J. E. Gearien, E. B.
Thompson, J. Med. Chem. 1987, 30, 424–427.
[3] T. Alderson, E. L. Jenner, Jr. R. V. Lindsey, J. Am.
Chem. Soc. 1965, 87, 5638–5645.
[4] C. S. Yi, Z. J. He, D. W. Lee, Organometallics 2001, 20,
802–804.
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