PdII-catalyzed highly selective arylation of allyl esters via C-H functionalization of unreactive arenes with retention of the traditional leaving group

Article abstract of DOI:10.1002/asia.200900558

A highly selective Fujiwara-Moritani oxidative Heck reaction of allyl esters with unreactive arenes via C - H bond activation was developed, in which -H elimination is highly chemo-, regio- and stereoselective. Moreover, even electron-deficient arenes are tolerated in this type of C - H activation. 2010 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim.

Full text of DOI:10.1002/asia.200900558

COMMUNICATION
DOI: 10.1002/asia.200900558
II
À
Pd -Catalyzed Highly Selective Arylation of Allyl Esters via C H
Functionalization of Unreactive Arenes with Retention of the Traditional
Leaving Group
Delin Pan,[a] Miao Yu,*[b] Wei Chen,[c] and Ning Jiao*[a]
Dedicated to the 100th anniversary of the College of Chemistry, Peking University
The Heck reaction[1] has been one of the very useful
tions usually require a catalytic amount of PdII in the pres-
ence of an appropriate oxidant (Scheme 1, path B).[3] De-
spite the wide application of this “oxidative Heck reaction”,
preactivation of the aromatic carbon fragments is also re-
À
metal-catalyzed C C bond-forming processes in organic syn-
thesis during the past several decades.[2] The conventional
Heck reaction is catalyzed by Pd0, and organic halides or tri-
flates are used as electrophiles (Scheme 1, path A). Thus
À
quired. Catalytic functionalization of arenes via C H bond
activation provides
a
potentially economic and clean
method for making many chemicals directly from hydrocar-
bons.[4] Fujiwara et al. developed an efficient coupling of
arenes and activated alkenes through an oxidative palladiu-
m(II)-catalyzed process,[5] which is known as the Fujiwara–
Moritani oxidative Heck reaction (Scheme 1, path C). Since
then, substantial progress has been made to improve the ef-
ficiency and practicality of this reaction,[6] such as the im-
provement of the regioselectivity,[7] and the use of molecular
dioxygen as a reoxidant.[7c,d,8] Recently, highly selective
Heck reaction of allyl esters has attracted a great deal of at-
tention,[9] which is a challenging issue because of the compli-
cated selectivities in this kind of reaction. For example, b-
OAc elimination[10] of intermediate A[11] (Scheme 2, path a)
Scheme 1. Three types of Heck reactions.
prehalogenation of the substrates is required, and the forma-
tion of undesired halide by-products is unavoidable. In addi-
tion to the conventional Heck reaction, the use of organo-
metallic reagents is also an attractive strategy. These reac-
[a] D. Pan, Prof. N. Jiao
State Key Laboratory of Natural and Biomimetic Drugs
School of Pharmaceutical Sciences, Peking University
Xue Yuan Road 38, Beijing 100191 (P.R. China)
Fax : (+86)10-8280-5297
Scheme 2. Complicated selectivities in the Heck reaction of allyl esters.
E-mail: jiaoning@bjmu.edu.cn
would compete with b-H elimination; furthermore, competi-
tive b-H elimination with different hydride atoms gives dif-
ferent products[10a,c] (Scheme 2, paths b,c). Recently, our
group reported ligand-free Pd-catalyzed Heck reactions of
allyl esters with aryl iodides[12a] or organoboronic acids.[12b]
Highly selective control of the b-H elimination was achieved
in these methods. We demonstrate herein a highly selective
[b] Prof. M. Yu
Department of Radiology
Chinese PLA General Hospital, No. 28
Fuxing Road, Beijing 100853 (P.R. China)
E-mail: yum301fsk@163.com
[c] W. Chen
Chinese PLA Postgraduate Medical School, No. 28
Fuxing Road, Beijing 100853 (P.R. China)
1090
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 1090 – 1093

oxidative Heck reaction of allyl esters with unreactive
(Table 1, entry 7). Notably, the regio- and stereoselectivities
were very high in this transformation. Neither b-OAc elimi-
nation product (Scheme 2, path a) nor allylic product via b-
H elimination (Scheme 2, path b) was observed. It was obvi-
ous that AgI is essential to this reaction (see entries 3 and 10
in Table 1), and protic acid also plays an important role in
this transformation (see entries 3 and 9 in Table 1). We also
tested other catalytic systems that reported previously to be
efficient for Fujiwara–Moritani oxidative Heck reaction
(Table 1, entries 13–15); however, none of these catalytic
systems exhibited higher efficiency in this reaction.
The scope of this reaction was then examined, and the re-
sults are summarized in Table 2. Substituted benzenes react-
ed well with allyl acetate (2a) under the optimal conditions,
producing substituted (E)-cinnamyl acetates (E)-3 with high
regio- and stereoselectivities. The reactions of electron-rich
À
arenes via C H bond activation.
In the selective Heck reactions of allyl esters with aryl io-
dides or organoboronic acids that we have developed, AgI
played a significant role to promote b-H elimination, leading
selectively to the retention of traditional leaving groups
such as OAc and OCO2Me. It is well known that AgI can be
used to control the regioselectivity[13a] and the double-bond
position[13b,c] in the arylation of olefins, and also can serve as
an excellent oxidant in the PdII/oxidant agent catalytic
system.[6] Thus, we hypothesized that a selective Fujiwara–
Moritani oxidative Heck reaction of allyl esters with arenes
À
through b-H elimination via C H activation could be realiz-
ed by the use of Ag as an oxidant under proper conditions.
We initially investigated the reaction of benzene (1a) and
allyl acetate (2a) catalyzed by PdACTHNUTRGNENUG(OAc)2 (Table 1). Based
Table 1. Pd
(OAc)2-catalyzed Fujiwara–Moritani oxidative Heck reaction
Table 2. Pd
ACHTUNGRTEN(NNUG OAc)2-Catalyzed Fujiwara–Moritani oxidative Heck reaction
between benzene (1a) and allyl acetate (2a).[a]
of allyl acetate 2a with different arenes 1.[a]
Entry Oxidant (equiv)
Additive (equiv) Yield (E)-3a [%]
1[b]
2
3
4
5
6
7
8
9
Ag2CO3 (0.6)/O2
Ag2CO3 (0.6)/CuACHTUNGTRENNUNG(OAc)2 (2.0) AcOH (16)
trace
0
49
0
33
0
51
39
trace
0
27
0
trace
16
14
Entry
1
T [8C] Yield (E)-3 [%] o/m/p[b]
1
2
3
4
5
6
7
8
benzene (1a)
toluene (1b)
anisole (1c)
80
110
110
110
110
110
110
100
51 (3a)
55 (3b)
62 (3c)
52 (3d)
46 (3e)
34 (3 f)
39 (3g)
37 (3h)
56 (3i)
61 (3j)
49 (3k)
–
Ag2CO3 (0.6)/BQ (2.0)
Ag2CO3 (0.6)/oxone (2.0)
Ag2O (0.6)/BQ (2.0)
AcOH (16)
AcOH (16)
AcOH (16)
23:6:71
45:8:47
34:36:30
15:64:21
15:66:19
18:61:21
m>95%[c]
–
chlorobenzene (1d)
C6H5CO2Me (1e)
C6H5COMe (1 f)
C6H5NO2 (1g)
C6H5CF3 (1h)
1,4-dimethyl benzene (1i) 110
4-methyl anisole (1j)
4-chloro-anisole (1k)
AgNO3 (1.2)/BQ (2.0)
AcOH (16)
Ag2CO3
N
n-C4H9CO2H (16)
n-C9H19CO2H (16)
Ag2CO3 (0.6)/BQ (2.0)
AgOAc (1.2)/BQ (2.0)
K2CO3 (2.0)/BQ (2.0)
10
AcOH (16)
AcOH (16)
AcOH (16)
AcOH (16)
9
10
11
11[c,d] AgOAc (1.2)/BQ (2.0)
[d]
110
110
–
–
12[c,e] AgOAc (1.2)/BQ (2.0)
[e]
13[c,f] Cu
(OAc)2 (2.0)
14[c,g] BQ (0.1)/tBuOOH (1.2)
[a] ArH (1, 50 mmol), allyl acetate (2a, 0.5 mmol), PdACHTUNGTRENNUNG(OAc)2
(0.025 mmol), Ag2CO3 (0.3 mmol), BQ (1.0 mmol), and n-pentanoic acid
15[c,h] tBuOOBz (2.0)
(8.0 mmol), heated under air for 48 h. [b] The ratio of the isomers was
determined by H NMR. [c] The (E)-ortho-3h and (E)-para-3h could not
be obviously assigned. [d] (E)-3-(2’-methoxy-5’-methylphenyl)-2-propen-
1-ol acetate ((E)-3ja)/(E)-3-(5’-methoxy-2’-methylphenyl)-2-propen-1-ol
[a] Benzene (1a, 50 mmol), allyl acetate (2a, 0.5 mmol,) PdACTHNUTRGNEUNG(OAc)2
1
(0.025 mmol), additives, reflux under air for 48 h. [b] The reaction was
carried out under O2 (1 atm). [c] 5.0 mmol of benzene was used. [d] 1, 4-
Dioxane (3 mL) was used as solvent. [e] DCE (3 mL) was used as sol-
vent. [f] The conditions are the same as with reference [7b]. [g] AcOH
(1 mL) and Ac2O (0.3 mL) were used as co-solvent; the conditions are
the same as with reference [14]. [g] 1, 4-Dioxane (1.8 mL), AcOH
(0.6 mL), and DMSO (0.3 mL) were used as co-solvent; the conditions
are the same as with reference [7d].
acetate
((E)-3jb)=87:13.
[e] (E)-3-(2’-chloro-5’-methoxyphenyl)-2-
propen-1-ol acetate ((E)-3ka)/(E)-3-(5’-chloro-2’-methoxyphenyl)-2-
propen-1-ol acetate ((E)-3kb)=91:9.
arenes gave higher yields (Table 2, entries 2,3,9,10). To our
delight, even benzenes with electron-withdrawing groups,
such as Cl, CO2Me, COMe, NO2, and CF3, proceeded
smoothly to give the expected products (Table 2, entries 4–
8). Compared with the previous olefination of arenes, which
are usually limited to election-rich arenes,[7,15] this method
could serve as a useful supplement. Bis-substituted benzenes
also reacted well with allyl acetate (2a) to give the desired
products in moderate yields (Table 2, entries 9–11). It is ob-
served that benzenes bearing electron-withdrawing groups
were mainly functionalized at the meta position, while ben-
zenes bearing electron-donating groups mainly at the ortho
and para position, which suggests that the reaction initiates
via electrophilic aromatic palladation.[3f,g]
on our previous studies, Ag2CO3 (0.6 equiv) was used in
these reactions, and AcOH (16 equiv) was employed be-
cause acid could work as a proton shuttle and assist this
transformation.[14] Only a trace amount of the expected
product (E)-3a was formed when molecular dioxygen was
used as a co-oxidant (Table 1, entry 1).
Then we examined the efficiencies of other co-oxidants
(Table 1, entries 2–4). 1,4-benzoquinone (BQ) proved the
best giving (E)-3a in 49% yield (Table 1, entry 3). Use of
other AgI salts gave lower yields (Table 1, entries 5,6). Fur-
ther investigation indicated that (E)-3a was formed in the
highest yield when n-pentanoic acid was used as the additive
Chem. Asian J. 2010, 5, 1090 – 1093
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
1091

M. Yu, N. Jiao et al.
COMMUNICATION
A variety of substituted allyl esters 2 were investigated as
substrates (Table 3). Certain allyl acetates substituted at the
a- and b-positions are all tolerated in this transformation,
activation. Further study on the synthetic applications of
this process is ongoing in our laboratory.
Experimental Section
Table 3. Pd
ACHTUNGTRENNUNG(OAc)2-catalyzed Fujiwara–Moritani oxidative Heck reaction
of arenes 1 with different allyl esters 2.[a]
Typical procedure: To a mixture of PdACHTUNRGTNEUNG(OAc)2 (5.6 mg, 0.025 mmol) and
Ag2CO3 (83 mg, 0.3 mmol), BQ (120 mg, 1.0 mmol), and benzene 1a
(3.9 g, 50 mmol) were added allyl acetate 2a (50 mg, 0.5 mmol) and n-
pentanoic acid (0.82 g, 8.0 mmol) subsequently. The resulting mixture
was heated at reflux for 48 h. After evaporation, the residue was carefully
purified by flash chromatography on silica gel (eluent: petroleumether/
ether=10:1) to afford 45 mg (51%) of (E)-3a; liquid; 1H NMR (CDCl3,
300 MHz): d=7.20–7.43 (m, 5H), 6.66 (d, J=15.6 Hz, 1H), 6.29 (dt, J=
15.6, 6.3 Hz, 1H), 4.73 (d, J=6.3 Hz, 2H), 2.11 ppm (s, 3H); 13C NMR
(CDCl3, 75.4 MHz): d=170.83, 136.15, 134.18, 128.58, 128.04, 126.57,
123.11, 65.05, 20.98 ppm; MS (70 eV): m/z (%): 176.2 (17) [M+], 43
Entry
1
R1
R2
R3
2
Yield (E)-3 [%]
1
2
3
benzene (1a)
benzene (1a)
benzene (1a)
benzene (1a)
C6H5CHO (1l)
H
H
H
H
Ph
Me
Et
C5H11
H
Me
Me
Me
OMe
Me
2b
2c
2d
2e
2 f
59 ((E)-3l)
48 ((E)-3m)
56 ((E)-3n)
51 ((E)-3o)
43 ((E)-3p)
4
(100); IR (neat): n˜ =1739, 1653, 1236, 1027 cmÀ1
.
5[b]
H
[a] ArH (1, 50 mmol), allyl acetate (2a, 0.5 mmol), PdACTHNUTRGNEUNG(OAc)2
(0.025 mmol), Ag2CO3 (0.3 mmol), BQ (1.0 mmol), and n-pentanoic acid
(8.0 mmol), reflux under air for 48 h. [b] The reaction was conducted at
1108C, and the product was obtained as an isomeric mixture (o/m/p=
1
23:57:20, determined by H NMR).
Acknowledgements
Financial support from Peking University, National Science Foundation
of China (Nos. 20702002, 20872003), and National Basic Research Pro-
gram of China (973 Program) (Grant No. 2009CB825300) are greatly ap-
preciated.
giving aryl-substituted (E)-allyl acetates in moderate yield.
We were pleased to find that even allyl methyl carbonate
(2e) reacted well with benzene under the optimal conditions
(Table 3, entry 4). The regio- and stereoselectivities were
also very high in these cases.
A plausible mechanism is proposed in Scheme 3. As re-
ported previously,[5–7,12,16] the coordination between O and
Pd atoms can help to interpret the selectivities observed in
Keywords: allylic compounds · heck reaction · palladium ·
regioselectivity · silver
[1] a) H. A. Dieck, R. F. Heck, J. Am. Chem. Soc. 1974, 96, 1133;
b) R. F. Heck, J. P. Nolley, Jr., J. Org. Chem. 1972, 37, 2320; c) R. F.
Heck, J. Am. Chem. Soc. 1968, 90, 5518.
[2] For leading reviews on the Heck reaction, see: a) P. J. Guiry, D.
Kiely, Curr. Org. Chem. 2004, 8, 781; b) M. Shibasaki, E. M. Vogl, T.
Ohshima, Adv. Synth. Catal. 2004, 346, 1533; c) A. B. Dounay, L. E.
Overman, Chem. Rev. 2003, 103, 2945; d) I. P. Beletskaya, A. V.
Cheprakov, Chem. Rev. 2000, 100, 3009; e) C. Amatore, A. Jutand,
Acc. Chem. Res. 2000, 33, 314; f) A. De Meijere, F. E. Meyer,
Angew. Chem. 1994, 106, 2473; Angew. Chem. Int. Ed. Engl. 1994,
33, 2379; g) G. D. Daves, Jr., A. Hallberg, Chem. Rev. 1989, 89,
1433.
Scheme 3. Proposed mechanism of the selective Heck reaction of allyl
acetate with arene.
[3] For some recent examples of oxidative Heck reactions, see: a) D.-C.
Xiong, L.-H. Zhang, X.-S. Ye, Org. Lett. 2009, 11, 1709; b) V. S. Thir-
unavukkarasu, K. Parthasarathy, C.-H. Cheng, Angew. Chem. 2008,
120, 9604; Angew. Chem. Int. Ed. 2008, 47, 9462; c) J. D. Crowley,
K. D. Hꢁnni, A.-L. Lee, D. A. Leigh, J. Am. Chem. Soc. 2007, 129,
12092; d) J. Lindh, P.-A. Enquist, ꢂ. Pilotti, P. Nilsson, M. Larhed, J.
Org. Chem. 2007, 72, 7957; e) K. S. Yoo, C. P. Park, C. H. Yoon, S.
Sakaguchi, J. O’Neill, K. W. , Org. Lett. 2007, 9, 3933; f) K. S. Yoo,
S. H. Yoon, K. W. Jung, J. Am. Chem. Soc. 2006, 128, 16384; g) A.
Inoue, H. Shinokubo, K. Oshima, J. Am. Chem. Soc. 2003, 125,
1484.
these reactions. The s-aryl-PdII complex (II) from electro-
philic substitution of arene undergoes highly regioselective
insertion owing to this coordination (III, Scheme 3). Subse-
quently, Ha finally regio- and stereoselectively reached the
syn relationship with Pd for b-H elimination leading to (E)-
3. Pd catalyst was then reoxidized by BQ and/or Ag+ to ful-
fill the catalytic cycle.
À
[4] For some reviews on C H activation chemistry, see: a) Y. Zhou, J.
Zhao, L. Liu, Angew. Chem. 2009, 121, 7262; Angew. Chem. Int. Ed.
2009, 48, 7126; b) X. Chen, K. M. Engle, D.-H. Wang, J.-Q. Yu,
Angew. Chem. 2009, 121, 5196; Angew. Chem. Int. Ed. 2009, 48,
5094; c) M. Brookhart, M. L. H. Green, G. Parkin, Proc. Natl. Acad.
Sci. USA 2007, 104, 6908; d) R. G. Bergman, Nature 2007, 446, 391;
e) S. S. Stahl, J. A. Labinger, J. E. Bercaw, Angew. Chem. 1998, 110,
2298; Angew. Chem. Int. Ed. 1998, 37, 2180; f) A. E. Shilov, G. B.
Shul’pin, Chem. Rev. 1997, 97, 2879; g) R. H. Crabtree, Chem. Rev.
1985, 85, 245.
In conclusion, we have developed a PdACTHNUTRGENUG(N OAc)2-catalyzed
highly selective Fujiwara–Moritani oxidative Heck reaction
À
of allyl esters with unreactive arenes via C H bond activa-
tion. b-H elimination is highly chemo-, regio-, and stereose-
lectively controlled, leading to the retention of traditional
leaving groups such as OAc and OCO2Me. Moreover, even
À
electron-deficient arenes are tolerated in this kind of C H
1092
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Chem. Asian J. 2010, 5, 1090 – 1093

II
À
Pd -Catalyzed Highly Selective Arylation of Allyl Esters via C H Functionalization
[5] a) C. Jia, D. Piao, J. Oyamada, W. Lu, T. Kitamura, Y. Fujiwara, Sci-
ence 2000, 287, 1992; b) C. Jia, W. Lu, T. Kitamura, Y. Fujiwara,
Org. Lett. 1999, 1, 2097; c) Y. Fujiwara, I. Moritani, S. Danno, R.
Asano, S. Teranishi, J. Am. Chem. Soc. 1969, 91, 7166; d) I. Morita-
ni, Y. Fujiwara, Tetrahedron Lett. 1967, 8, 1119.
[11] a) M. Lautens, E. Tayama, C. Herse, J. Am. Chem. Soc. 2005, 127,
72; b) B. Mariampillai, C. Herse, M. Lautens, Org. Lett. 2005, 7,
4745; c) H. Ohmiya, Y. Makida, T. Tanaka, M. Sawamura, J. Am.
Chem. Soc. 2008, 130, 17276; d) D. Bouyssi, V. Gerusz, G. Blame,
Eur. J. Org. Chem. 2002, 2445; e) J. Ramnauth, O. Poulin, S. Rakhit,
S. P. Maddaford, Org. Lett. 2001, 3, 2013; f) Y. Uozumi, H. Danjo, T.
Hayashi, J. Org. Chem. 1999, 64, 3384; g) J. Y. Legros, J. C. Flaud,
Tetrahedron Lett. 1990, 31, 7453; h) N. Miyaura, K. Yamada, S. A.
Suginome, J. Am. Chem. Soc. 1985, 107, 972.
[6] For a recent review, see: E. M. Beccalli, G. Broggini, M. Martinelli,
S. Sottocornola, Chem. Rev. 2007, 107, 5318.
[7] a) Y.-H. Zhang, B.-F. Shi, J.-Q. Yu, J. Am. Chem. Soc. 2009, 131,
5072; b) G. Cai, Y. Fu, Y. Li, X. Wan, Z. Shi, J. Am. Chem. Soc.
2007, 129, 7666; c) J.-R. Wang, C.-T. Yang, L. Liu, Q.-X. Guo, Tetra-
hedron Lett. 2007, 48, 5449; d) E. M. Beck, N. P. Grimster, R.
Hatley, M. J. Gaunt, J. Am. Chem. Soc. 2006, 128, 2528; e) N. P.
Grimster, C. Gauntlett, C. R. A. Godfrey, M. J. Gaunt, Angew.
Chem. 2005, 117, 3185; Angew. Chem. Int. Ed. 2005, 44, 3125; f) E.
Capito, J. M. Brown, A. Ricci, Chem. Commun. 2005, 1854; g) G. T.
[12] a) D. Pan, A. Chen, Y. Su, W. Zhou, S. Li, W. Jia, J. Xiao, Q. Liu, L.
Zhang, N. Jiao, Angew. Chem. 2008, 120, 4807; Angew. Chem. Int.
Ed. 2008, 47, 4729; b) Y. Su, N. Jiao, Org. Lett. 2009, 11, 2980.
[13] a) W. Cabri, I. Candiani, A. Bedeschi, S. Penco, J. Org. Chem. 1992,
57, 1481; b) A. Madin, L. E. Overman, Tetrahedron Lett. 1992, 33,
4859; c) K. Karabelas, C. Westerlund, A. Hallberg, J. Org. Chem.
1985, 50, 3896.
ˇ
Lee, X. Jiang, K. Prasad, O. Repie, T. J. Blacklock, Adv. Synth.
Catal. 2005, 347, 1921; h) M. Boele, G. van Strijdonck, A. de Vries,
P. Kamer, J. de Vries, P. van Leeuwen, J. Am. Chem. Soc. 2002, 124,
1586.
[14] a) C. Jia, T. Kitamura, Y. Fujiwara, Acc. Chem. Res. 2001, 34, 633;
b) A. M. Echavarren, B. Gꢃmez-Lor, J. J. Gonzꢄlez, ꢅ. de Frutos,
Synlett 2003, 0585; c) M. Lafrance, K. Fagnou, J. Am. Chem. Soc.
2006, 128, 16496; d) N. Lebrasseur, I. Larrosa, J. Am. Chem. Soc.
2008, 130, 2926–2927; e) B. Liꢆgault, D. Lapointe, L. Caron, A.
Vlassova, K. Fagnou, J. Org. Chem. 2009, 74, 1826.
[15] a) J. Wu, X. Cui, L. Chen, G. Jiang, Y. Wu, J. Am. Chem. Soc. 2009,
131, 13888; b) S. H. Cho, S. J. Hwang, S. Chang, J. Am. Chem. Soc.
2008, 130, 9254.
[16] a) J. H. Delcamp, A. P. Brucks, M. C. White, J. Am. Chem. Soc.
2008, 130, 11270; b) S. K. Kang, H. W. Lee, S. B. Jang, T. H. Kim,
S. J. Pyun, J. Org. Chem. 1996, 61, 2604; c) E. Bernocchi, S. Cacchi,
P. G. Ciattini, E. Morera, G. Ortar, Tetrahedron Lett. 1992, 33, 3073.
[8] a) T. Yamada, S. Sakaguchi, Y. Ishii, J. Org. Chem. 2005, 70, 5471;
b) M. Tani; S. Sakaguchi, Y. Ishii, J. Org. Chem. 2004, 69, 1221; S.
Sakaguchi, Y. Ishii, J. Org. Chem. 2004, 69, 1221; c) T. Yokota, M.
Tani, S. Sakaguchi, Y. Ishii, J. Am. Chem. Soc. 2003, 125, 1476;
d) M. Dams, D. E. de Vos, S. Celen, P. A. Jacobs, Angew. Chem.
2003, 115, 3636; Angew. Chem. Int. Ed. 2003, 42, 3512.
[9] a) J. Ruan, X. Li, O. Saidi, J. Xiao, J. Am. Chem. Soc. 2008, 130,
2424; b) J. H. Delcamp, M. C. White, J. Am. Chem. Soc. 2006, 128,
15076.
[10] a) X. Lu, Top. Catal. 2005, 35, 73; b) Q. Zhang, X. Lu, J. Am. Chem.
Soc. 2000, 122, 7604; c) G. Zhu, X. Lu, Organometallics 1995, 14,
4899; d) J. C.-Y. Cheng, G. D. Daves. Jr, Organometallics 1986, 5,
1753.
Received: October 14, 2009
Published online: February 8, 2010
Chem. Asian J. 2010, 5, 1090 – 1093
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
1093