Palladium-catalyzed Mizoroki-Heck-type reaction of aryl trimethoxysilanes

Article abstract of DOI:10.1055/s-0029-1217571

A palladium-catalyzed Mizoroki-Heck-type reaction of aryl trimethoxysilanes with olefins is described. A series of ArSi(OMe)₃ and olefins, including electron-rich and electron-deficient analogues worked well in the procedure, affording the arylation products in moderate to good yields. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0029-1217571

2
198
LETTER
Palladium-Catalyzed Mizoroki–Heck-Type Reaction of
Aryl Trimethoxysilanes
M
Z
izoroki–Heck
h
-Type
R
eact
i
ion of
A
s
ryl Trim
e
h
thoxysilane
i
s
Ye, Fan Chen, Fang Luo, Wenhui Wang, Baoda Lin, Xiaofei Jia, Jiang Cheng*
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325027, P. R. of China
Fax +86(577)88156826; E-mail: jiangcheng@wzu.edu.cn
Received 24 April 2009
a-rhodium carbonyl intermediates in the presence of wa-
Abstract: A palladium-catalyzed Mizoroki–Heck-type reaction
of aryl trimethoxysilanes with olefins is described. A series of
ter.6u
ArSi(OMe) and olefins, including electron-rich and electron-defi- In 1998 and 2001, Mori and co-workers described the pal-
3
cient analogues worked well in the procedure, affording the aryla-
tion products in moderate to good yields.
ladium and rhodium-catalyzed oxidative Mizoroki–Heck-
8
type reaction of aryl silanol. However, only a,b-unsatur-
8a
Key words: palladium-catalyzed, aryltrimethoxysilanes, cross- ated conjugated compounds
or electron-deficient
coupling, Heck reaction, alkenes
8b
alkenes were reported and the procedure was very sensi-
tive to the electronic nature of the carbonyl substrate.8
Moreover, while the synthesis of chlorosilanes, which un-
a
The palladium-catalyzed arylation of olefins, also known derwent hydrolysis to form silanols, was somewhat te-
9
as the Mizoroki–Heck reaction, is one of the most versa- dious, aryl trialkoxysilanes could be readily prepared
tile tools available for C–C bond formation used in organ- from the reaction of ArX and either tetraalkoxysilanes or
1
7b,10
ic synthesis. Over the past few decades, some alternative trialkoxysilanes.
In 2003, Mori reported an iridium-
2
halide surrogates such as diazonium halide salts, tri- catalyzed Mizoroki–Heck reaction of aryl trialkoxy-
3
4
5
11
flates, acid chlorides, and telluronium salts, have been silanes that occurred at 120 °C. Herein, we wish to re-
developed for use in the Mizoroki–Heck reaction. Recent- port a mild, palladium-catalyzed cross-coupling reaction
ly, the transition-metal catalyzed oxidative Mizoroki– of aryl trimethoxysilanes with alkenes, including elec-
Heck reaction of boronic acids with alkenes has drawn tron-deficient, electron-rich, acyclic and cyclic conjugated
considerable attention because boronic acids are compar- alkenes.
6
atively stable, nontoxic, and easily available. Compared
We envisioned that the hydrolysis of the a-palladium car-
with the organoboranes, organosilane reagents, especially
bonyl intermediates would be inhibited in the absence of
aryl trialkoxysilanes, are lower-cost and easily purified by
water. Initially, we investigated the Mizoroki–Heck-type
reaction of phenyl trimethoxysilane (2a) with cyclohex-2-
7
distillation or chromatography. However, much attention
had been paid to transition-metal-catalyzed 1,4-conjugate
addition (CA) of organosilane reagents to a,b-unsaturated
conjugated compounds. The Mizoroki–Heck-type reac-
tion (HT), which occurs as a side reaction of the 1,4-con-
jugated addition and results from b-H elimination of the
a-metal carbonyl intermediates in the aforementioned
reaction, was occasionally observed (Scheme 1).
enone (1a) in the presence of Pd(OAc) (5 mol%), bipy
2
(
10 mol%) and three equivalents of various fluoride
sources in anhydrous DMF (2 mL) at 60 °C (Table 1). The
results suggested that the fluoride source had a dramatic
effect on the yields. Among the fluoride sources screened,
only FeF3 and AgF showed good catalytic activity
(
Table 1, entries 3 and 4). Remarkably, compared with
From both organometallic and synthetic points of view, it other solvents, DMF proved to be the best among the ar-
is important to switch the reactivity of a-metal carbonyl ray of solvents tested (Table 1, entries 4–8). The ligands
intermediates. The reactivity of an organo-palladium spe- were also found to be crucial for this transformation. The
cies is not only determined by the intrinsic nature of pal- phosphines tested, such as tri(2-tolyl)phosphine and
ladium, but can also be tuned by the supporting ligands tris(3,5-dimethylphenyl)phosphine, which are susceptible
and reaction conditions. Zou described the tunability of a to oxidation under air, gave moderate yields (Table 1, en-
competition between b-H elimination versus hydrolysis of tries 13 and 14), whereas the phenanthroline class of
R2
R1
R1
R2 Ar
H
R1
R2
H
hydrolysis
β-H elimination
Ar
O
O
O
Ar
H
M
CA product
M = Rh, Pd, etc.
HT product
Scheme 1 Two plausible pathways for a-metal carbonyl intermediates
SYNLETT 2009, No. 13, pp 2198–2200
x
x
.x
x
.2
0
0
9
Advanced online publication: 16.07.2009
DOI: 10.1055/s-0029-1217571; Art ID: W05909ST
©
Georg Thieme Verlag Stuttgart · New York

LETTER
Mizoroki–Heck-Type Reaction of Aryl Trimethoxysilanes
2199
Table 1 Effects of Solvents and Fluoride Source on the Reaction
Table 2 Mizoroki–Heck-Type Reaction of Aryl Trimethoxysilanes
Yielda
with Cyclohex-2-enonea
O
O
O
O
Pd, ligand, F source
solvent
Pd(OAc) , AgF
2
+
PhSi(OMe)3
+
ArSi(OMe)3
1,10-phenanthroline, DMF
Ph
Ar
1
a
3
2
1a
2a
3aa
2
2
2
2
a, Ar = Ph
Entry Ligand
F source
Solvent Yield
2e, Ar = 4-MeOC H4
2f, Ar = 3,5-di-MeC6H3
6
b, Ar = 4-MeC6H4
c, Ar = 3-MeC6H4
d, Ar = 2-MeC6H4
b
(
%)
2
g, Ar = 2-naphthalenyl
1
2
3
4
5
6
7
8
9
0
1
bipy
TBAF·3H O DMF
<5
<5
70
84
<5
<5
2
Entry
ArSi(OMe)3
Product
3aa
Yield (%)b
bipy
KF
DMF
DMF
DMF
THF
1
2
3
4
5
6
2a
2b
2c
2d
2e
2f
90
82
91
22
77
86
70
bipy
FeF3
AgF
AgF
AgF
AgF
AgF
AgF
AgF
AgF
3ab
3ac
bipy
bipy
3ad
3ae
bipy
MeCN
bipy
toluene <5
dioxane <5
3af
bipy
7
2g
3ag
Ph3P
DMF
DMF
DMF
44
90
50
a
Reaction conditions: cyclohex-2-enone (1a; 19 mL, 0.2 mmol),
ArSi(OMe) 2 (0.3 mmol), Pd(OAc) (2.2 mg, 5 mol%), 1,10-phen-
1
1
1,10-phenanthroline
3
2
anthroline (3.6 mg, 10 mol%), AgF (76mg, 0.6 mmol), anhydrous
DMF (2 mL), air, 60 °C.
Isolated yield.
4,7-dimethyl-
1
,10-phenanthroline
b
12
2,9-dimethyl-4,7-diphenyl- AgF
,10-phenanthroline
DMF
87
1
In the next stage, we explored the reaction of a variety of
olefins with PhSi(OMe) as shown in Table 3. Electron-
3
1
1
1
1
3
4
5
6
7
(2-MeC H ) P
AgF
AgF
AgF
AgF
DMF
DMF
DMF
DMF
DMF
34
6
4 3
deficient olefins such as methyl acrylate 3d reacted
smoothly to afford the desired product 3da in high yield.
However, when acrylamide was subjected to the proce-
dure, the yield dramatically decreased to 33%. The elec-
tron-rich olefin 1e also worked well under the standard
reaction conditions and provided (E)-stilbene (3ea) in
(3,5-Me C H ) P
40
2
6
3 3
42
1,10-phenanthroline
1,10-phenanthroline
88c
<5d
1
7
5% yield. Furthermore, styrene and 2-vinylpyridine
a
Reaction conditions: 1a (19 mL, 0.2 mmol), 2a (56 mL, 0.3 mmol),
were good reaction partners and gave 78% and 62% yields
of (E)-stilbene (3ba) and (E)-2-styrylpyridine (3ca), re-
spectively (Table 2, entries 1 and 2). However, the former
compound (E)-2-styrylpyridine failed to undergo the aryl-
ation reaction, presumably due to steric hindrance.
Pd(OAc) (2.2 mg, 5 mol%), ligand (10 mol%), F source (0.6 mmol),
2
anhydrous solvent (2 mL), air, 60 °C.
b
Isolated yield.
Under N2.
Under O2.
c
d
Silver(I) fluoride may play a dual role in the procedure.
One could be to activate the ArSi(OMe) by forming
ligands, which are more stable towards oxidation, provid-
ed high yields (Table 1, entries 10–12). Amongst these,
3
–
[
ArSi(OMe) F] , the other may be to regenerate Pd(II)
3
from Pd(0), which is generated from the HPdX released
1
,10-phenanthroline was found to be the most effective;
using this ligand, the yield of 3aa sharply increased to
0%.
by the b-H elimination of a-metal carbonyl intermediates
(
Scheme 1).
9
In conclusion, we have developed an efficient and mild
method for a Mizoroki–Heck-type reaction of both elec-
tron-rich and electron-deficient olefins by employing
readily prepared aryl trimethoxysilanes. The reaction af-
forded the arylation products in moderate to good yields.
Under our optimized reaction conditions, we explored the
scope of reaction with a range of aryl trimethoxysilanes as
1
2
shown in Table 2. Aryl trimethoxysilane substrates
worked well under the reaction conditions. Electron-rich,
as well as electron-neutral aryl trimethoxysilanes coupled
efficiently with cyclohex-2-enone and good yields were
obtained (Table 2, entries 1 and 5). However, the steric
hindrance affected the efficiency. For example, only a
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett.
2
2% yield of 3ad was isolated.
Synlett 2009, No. 13, 2198–2200 © Thieme Stuttgart · New York

2
200
Z. Ye et al.
LETTER
Table 3 Mizoroki–Heck-Type Reaction of Phenyl Trimethoxy-
(6) (a) Dieck, H. A.; Heck, R. F. J. Org. Chem. 1975, 40, 1083.
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silane with Olefinsa
85. (c) Du, X.; Suguro, M.; Hirabayashi, K.; Mori, A. Org.
Pd(OAc)2, AgF
Lett. 2001, 3, 3313. (d) Crowley, J. D.; Hänni, K. D.; Lee,
A.-L.; Leigh, D. A. J. Am. Chem. Soc. 2007, 129, 12092.
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M. J. Org. Chem. 2007, 72, 7957. (f) Yoo, K. S.; Park,
C. P.; Yoon, C. H.; Sakaguchi, S.; O’Neill, J.; Jung, K. W.
Org. Lett. 2007, 9, 3933. (g) Yoo, K. S.; Yoon, C. H.;
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Nilsson, P.; Larhed, M. Green Chem. 2006, 8, 338.
R
+
Si(OMe)3
1
,10-phenanthroline
R
DMF
1
2a
3
1
1
1
1
b, R = Ph
c, R = 2-py
1f, R = CONH2
d, R = COOMe
e, R = OCOMe
1g, (E)-2-styrylpyridine
Entry
Olefin
Product
Yield (%)b
(
i) Farrington, E. J.; Barnard, C. F. J.; Rowsell, E.; Brown,
1
2
3
4
5
1b
1c
1d
1e
1f
3ba
3ca
3da
3ea
3fa
78
62
92
75
33
<5
J. M. Adv. Synth. Catal. 2005, 347, 185. (j) Akiyama, K.;
Wakabayashi, K.; Mikami, K. Adv. Synth. Catal. 2005, 347,
1
Chem. Commun. 2004, 218. (l) Andappan, M. M. S.;
Nilsson, P.; von Schenck, H.; Larhed, M. J. Org. Chem.
569. (k) Andappan, M. M. S.; Nilsson, P.; Larhed, M.
2
004, 69, 5212. (m) Lautens, M.; Mancuso, J.; Grover, H.
Synthesis 2004, 2006. (n) Kabalka, G. W.; Guchhait, S. K.;
Naravane, A. Tetrahedron Lett. 2004, 45, 4685.
(
o) Andappan, M. M. S.; Nilsson, P.; Larhed, M. Mol.
6
1g
3ga
Diversity 2003, 7, 97. (p) Jung, Y. C.; Mishra, R. K.; Yoon,
C. H.; Jung, K. W. Org. Lett. 2003, 5, 2231. (q) Lin, P.-S.;
Jeganmohan, M.; Cheng, C.-H. Chem. Asian J. 2007, 2,
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(s) Trivedi, R.; Roy, S.; Roy, M.; Sreedhar, B.; Kantam, M.
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Dalton Trans. 2007, 28, 3055. (v) Yoo, K. S.; Yoon, C. H.;
Jung, K. W. J. Am. Chem. Soc. 2006, 128, 16384.
a
Reaction conditions: olefin 1 (0.2 mmol), PhSi(OMe) (56 mL, 0.3
3
mmol), Pd(OAc) (2.2 mg, 5 mol%), 1,10-phenanthroline (3.6 mg, 10
2
mol%), AgF (76 mg, 0.6 mmol), anhydrous DMF (2 mL), air, 60 °C.
b
Isolated yield.
Acknowledgment
We thank the National Natural Science Foundation of China (No.
2
(
(
(
7) (a) Mitchell, T. N. In Metal-Catalyzed Cross-Coupling
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M.; DeShong, P. J. Org. Chem. 2004, 69, 8305.
8) For oxidative Mizoroki–Heck-type reactions of aryl silanol,
see: (a) Mori, A.; Danda, Y.; Fujii, T.; Hirabayashi, K.;
Osakada, K. J. Am. Chem. Soc. 2001, 123, 10774.
0504023) and Major Technology Program of Zhejiang Province
2008C11062-1) for financial support.
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2
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