Lewis acid-catalyzed c-h functionalization for synthesis of isoindolinones and isoindolines

Article abstract of DOI:10.1002/adsc.201000556

The Lewis acid-catalyzed C-H functionalization of 2-substituted azaarenes with N-sulfonylaldimines has been developed, which provides a rapid and efficient approach for synthesis of heterocycle-containing isoindolinones and isoindolines. Copyright

Full text of DOI:10.1002/adsc.201000556

COMMUNICATIONS
DOI: 10.1002/adsc.201000556
À
Lewis Acid-Catalyzed C H Functionalization for Synthesis of
Isoindolinones and Isoindolines
Bo Qian,a Shengmei Guo,a Chungu Xia,a and Hanmin Huanga,*
a
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese
Academy of Sciences, Lanzhou 730000, Peopleꢀs Republic of China
Fax : (+86)-931-496-8129; e-mail: hmhuang@licp.cas.cn
Received: July 14, 2010; Revised: September 13, 2010; Published online: December 7, 2010
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201000556.
À
Abstract: The Lewis acid-catalyzed C H function-
alization of 2-substituted azaarenes with N-sulfonyl-
ditional steps which lengthen the procedures. Another
intelligent approach reported by Hiyama and Li in-
volved the use of a catalytic amount of a Lewis acid
as activator for enhancing the acidity of C2-H.[6] In-
trigued by these elegant works and our recent efforts
on the Pd-catalyzed benzylic addition of 2-methyl-
ACHTUNGTRENNUNGaldimines has been developed, which provides a
rapid and efficient approach for synthesis of hetero-
cycle-containing isoindolinones and isoindolines.
Keywords: C H functionalization; isoindolines; iso-
indolinones; Lewis acids; tandem reactions
azaarenes to aldimines,[7] we envisaged that Lewis
ACHTUNGTRENNUNG
À
acids could also enhance the Brønsted acidity of the
À
benzylic C H bond of 2-substituted azaarenes and
À
the enhanced acidity of the benzylic C H in complex
À
A would favor C H cleavage that is facilitated by the
endogenous basic counteranion of the Lewis acid or
Since the pyridine unit is an extremely important the basic electrophile (external base) to generate the
pharmacophore that can be found in many natural metal enamide B.[8] The in situ formed active metal
and synthetic bioactive compounds,[1] numerous meth- enamide species B would react with some appropriate
À
odologies have been developed to access substituted electrophiles to afford the C H functionalized prod-
pyridine derivatives.[2] One of the most expedient syn- uct 1 (Scheme 1). Herein, we report an efficient
thetic strategies towards functionalized pyridines has Lewis acid-catalyzed[9] C H functionalization of 2-
been developed through the direct C H functionali- substituted azaarenes with imines under neutral con-
À
À
zation of the pyridine core.[3,4] However, this ap- ditions. Notably, in a one-pot manipulation, nitrogen
proach is problematic owing to the p-electron-defi- heterocycle-containing isoindolinones and isoindo-
À
cient nature of the pyridine ring which generally re- lines could also be obtained in high yields via C H
sults in lower activity. One way to circumvent this functionalization-triggered tandem reactions.
problem is through introducing a “nitrogen atom-acti-
To test this possibility, and based on our previous
vation” group into the pyridine core to enhance the work on the palladium-catalyzed benzylic addition of
acidity of C2-H; this methodology has been exploited 2-substituted azaarenes to aldimines for the synthesis
by Fagnou, Hiyama, Chang, Charette and others who of heterocycle-containing amines,[7] we attempted the
used pyridine N-oxide and N-iminopyridinium ylides reaction of 2,6-lutidine 2a with tosylimine 3a in the
as alternative substrates.[5] While significant success presence of Lewis acids to provide the addition prod-
had been achieved, the apparent need for the activa- uct 1aa. To our delight, when the reaction mixture
tion group in all these catalytic reactions requires ad- was treated with 10 mol% of AlCl3, the benzylic addi-
À
Scheme 1. Lewis acid-catalyzed C H functionalization.
Adv. Synth. Catal. 2010, 352, 3195 – 3200
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3195

Bo Qian et al.
COMMUNICATIONS
tion reaction indeed proceeded readily at 1208C in tral groups on the phenyl ring (Table 2, entries 1–9).
1,4-dioxane to give the desired product in satisfactory Besides the substituted phenyl N-sulfonylaldimines,
yield (Table 1, entry 1, 62% yield). Encouraged by the naphthyl N-sulfonylaldimine also gave the desired
Table 2. Substrate scope of N-sulfonylaldimines.[a]
Table 1. Optimized reaction conditions.[a]
Yield [%][b]
Entry Cat. (mol%)
Solvent
T [oC] Yield [%][b]
Entry
Ar
R
Product
1
2
3
4
5
6
7
8
AlCl3 (10)
FeCl3 (10)
ZnCl2 (10)
NiBr2 (10)
dioxane
dioxane
dioxane
dioxane
120
120
120
120
120
120
120
120
120
120
120
120
62
69
58
28
40
33
67
78
75
49
60
58
64
80
58
71
50
1
2
3
4
5
6
7
8
C6H5
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ns
Ns
Ns
Ns
1aa
1ab
1ac
1ad
1ae
1af
1ag
1ah
1ai
1aj
1ak
1al
1am
1an
1ao
1ap
1aq
80
85
84
93
82
91
94
98
99
84
80
43
49
94
85
93
72
4-ClC6H4
2-ClC6H4
3-ClC6H4
4-BrC6H4
2-BrC6H4
3-BrC6H4
2,4-Cl2C6H3
2,6-Cl2C6H3
1-naphthyl
2-furyl
4-MeC6H4
4-MeOC6H4
4-MeC6H4
2-BrC6H4
4-MeOC6H4
(E)-PhCH=CH
Zn
Cu(OTf)2 (10) dioxane
AgOTf (10)
Sc(OTf)3 (10)
ACHTUNGTRENNUNG(OTf)2 (10) dioxane
ACHTUNGTRENNUNG
dioxane
dioxane
ACHTUNGTRENNUNG
9
BF3·Et2O (20) dioxane
9
10
11
12
13
14
15
16
17
Sc
Sc
Sc
Sc
Sc
Sc
Sc
Sc
N
THF
MTBE
DME
10
11
12
13
14
15
16
17
mesitylene 120
PhCF3
PhCF3
PhCF3
PhCF3
120
80
120
120
[a]
[a]
Reaction conditions: 2,6-lutidine 2a (0.75 mmol), imine
3a (0.3 mmol), solvent (1.5 mL), 24 h.
Isolated yield.
Reaction conditions: 2,6-lutidine 2a (0.75 mmol), imine 3
(0.3 mmol), Sc
ACHTUNGRTEN(NUNG OTf)3 (0.03 mmol), solvent (1.5 mL),
[b]
1208C, 24 h.
Isolated yield.
[b]
this initial result, we subsequently evaluated
a
number of commonly used Lewis acids. As outlined product in high yield (Table 2, entry 10). Furthermore,
in Table 1, this transformation was successful with a a heteroaromatic aldehyde-derived imine also gave a
broad range of metal salts with diverse Lewis acidity good yield (Table 2, entry 11). In case of substrates
including FeCl3, ZnCl2, NiBr2, Cu
ACHTUNGRTEN(NUNG OTf)2, AgOTf and containing an electron-donating group on the phenyl
Sc(OTf)3. Importantly, moderate to good activities ring, the desired amines were formed in less than
ACHTUNGTRENNUNG
were observed in all metal-mediated cases (Table 1, 50% yield under the same conditions. The lower reac-
entries 1–8). It is noteworthy that the inexpensive tivity of these substrates can be addressed by the in-
non-metal Lewis acid BF3·Et2O also gave a high yield troduction of electron-withdrawing groups on the N-
for this transformation (Table 1, entry 9, 75% yield). protecting group. Thus, when the p-nitrobenzenesul-
The superior catalytic efficiency exhibited by fonyl (Ns) group, instead of the tosyl group, was used
ScACHTUNGTRENNUNG(OTf)3 prompted us to select this metal salt for fur- as the N-protecting group, 2,6-lutidine 2a could be
ther exploration. Among the solvents examined, ben- smoothly added to the corresponding imines to afford
zotrifluoride gave the highest yield (Table 1, 1 in high yields (Table 2, entries 14–16). An alkenyl
entry 14). The temperature was found to influence the aldimine was compatible under this procedure, and
reactivity, for example, lowering the temperature to the nucleophilic addition product was isolated in good
808C caused the yield to decrease to 58%. The cata- yield (Table 2, entry 17). Disappointingly, aliphatic to-
lyst loading could be decreased to 1 mol% and still sylimines were unreactive here.
provided good yields, although 10 mol% was chosen
for improved results.
The scope of this transformation was further ex-
panded to a variety of 2-substituted azaarenes. To our
The scope of the process with various N-sulfonyl al- delight, we found this transformation to be very gen-
dimines was studied under the optimized conditions. eral for a wide range of 2-substituted azaarenes, and
The transformation proceeds very efficiently with a provided an easy access to a series of heterocycle-con-
wide range of N-tosylaldimines 3 bearing ortho-, taining amines. Yields for these heterocycle-contain-
meta-, and para-electron-withdrawing or electron-neu- ing amines ranged from moderate to excellent (42–
3196
asc.wiley-vch.de
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 3195 – 3200

À
Lewis Acid-Catalyzed C H Functionalization for Synthesis of Isoindolinones and Isoindolines
Table 3. Substrate scope of azaarenes.[a]
[a]
Reaction conditions: azaarene 2 (0.75 mmol), imine 3a (0.3 mmol), ScACTHNUTRGNEUNG(OTf)3 (0.03 mmol),
solvent (1.5 mL), 1208C, 24 h. isolated yield.
[b]
[c]
[d]
[e]
In dioxane.
In PhCF3.
In THF.
1
The dr was determined by H NMR.
95%), and featured pyridine, quinoline and quinoxa- es at a significantly faster rate than the methyl sp3 site
line rings. Compared to 2,6-lutidine, the reactions of (see Supporting Information). This result suggests
2-picoline and 2,4-lutidine gave 1ba and 1da in rela- that the thermodynamically more favored intermedi-
2
À
tively lower yields, but no sp C H functionalization ate D should be generated more quickly than inter-
À
was observed. This could be reasoned due to the mediate C in the C H cleavage step. The exclusive
higher relative acidity of these benzylic protons as formation of 1ja could be important for the rationali-
well as the kinetic preference for the formation of an zation that the nucleophilic addition step is most
enamide intermediate involving the benzylic carbon likely to be rate-limiting in this Lewis acid-catalyzed
during the course of the reaction (Scheme 1). Further- protocol, and thus, it is reasonable to anticipate that
more, 2-ethylquinoline was found to undergo selective the more sterically crowded intermediate F should
functionalization at the benzylic position in good react much more slowly than the less hindered inter-
yield.
mediate E and so 1j’a was obtained as the minor re-
When 2-benzyl-6-methylpyridine 2j with two kinds gioisomer (Scheme 2).
À
of benzylic C H sites was reacted with 3a, the
To further investigate the potential utility of this
1H NMR spectrum of the crude mixture indicated the chemistry, we investigated its use in the rapid prepa-
preferential formation of 1ja along with a small ration of 3-substituted isoindolinones which represent
amount of 1j’a in a ratio of approximately 2:1 an interesting structure found in many useful biologi-
(Table 3). Intriguingly, the regioselectivity is in sharp cally active compounds.[10] A tandem benzylic C H
contrast to our previous results achieved with palladi- addition and amidination proceeds to give the desired
À
um as a catalyst, where 1j’a was obtained as the isoindolinones 5 in high yields when methyl 2-[(tosyl-
major product.[7] To rationalize this observation, both
ACHTUNGTRENiNGNU mine)methyl]benzoate 4 was used under the standard
intermolecular (kH/kD =1.7) and intramolecular (kH/ conditions. As illustrated by several representative ex-
kD =1.5) kinetic isotope effects experiments were con- amples in Table 4, the scope of this transformation is
ducted under the standard conditions (see Supporting broad, different 2-substituted azaarenes can be used
Information). The KIE data shown here are much to allow the synthesis of heterocycle-containing isoin-
less extensive than those obtained in the case of the dolinones in a one-pot fashion with good to excellent
Pd-catalyzed protocol.[7] The deuterium exchange of yields, including those bearing pyridine, quinoline and
2j by treatment with Sc
ACHTUNGTREN(NGNU OTf)3 in D2O reveals that the quinoxaline rings (5a–h, 25–95% yields).
benzyl sp3 site adjacent to the phenyl group exchang-
Adv. Synth. Catal. 2010, 352, 3195 – 3200
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
3197

Bo Qian et al.
COMMUNICATIONS
Scheme 2. Mechanistic rationalization for the regioselectivity of 1ja and 1j’a.
Another tandem reaction involving the benzylic yield with a single diastereomer. A wide range of 2-
À
C H functionalization of 2-substituted azaarenes has substituted azaarenes were subjected to the conditions
been established from the reaction of 2-substituted similar to those of the benzylic addition reactions.
azaarenes with bifunctional substrate 6 containing an The 1,3-disubstituted N- tosylisoindolines were ob-
imine and Michael acceptor groups. This tandem reac- tained in 44–77% yields with high diastereoselectivi-
À
tion was triggered by the Lewis acid-catalyzed C H ties (Table 5). NMR and X-ray crystallographic analy-
functionalization and followed by an intramolecular ses of isoindolines 7 established the relative stereo-
aza-Michael addition to furnish the product 7 in high chemistry (Figure 1),[11] which indicated that the intra-
Table 4. Tandem reaction for synthesis of isoindolinones.[a]
[a]
Reaction conditions: 1 (0.75 mmol), imine 4 (0.3 mmol), ScACTHNURGTNEUNG(OTf)3 (0.03 mmol), solvent
(1.5 mL), 1208C, 24 h, isolated yield.
In PhCF3.
In THF.
[b]
[c]
[d]
[e]
In dioxane.
The dr value was determined by H NMR.
1
3198
asc.wiley-vch.de
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 3195 – 3200

À
Lewis Acid-Catalyzed C H Functionalization for Synthesis of Isoindolinones and Isoindolines
Table 5. Tandem reaction for synthesis of isoindolines.[a]
[a]
Reaction conditions: 2 (0.75 mmol), imine 6 (0.3 mmol), ScACTHNURGTNEUNG(OTf)3 (0.03 mmol), solvent
(1.5 mL), 1208C, 24 h, isolated yield, dr >20:1 and only one diastereoisomer was observed.
In PhCF3.
In THF.
[b]
[c]
[d]
In CPME.
molecular aza-Michael addition was cis-selective with
the 5-exo-trig cyclization. Notably, the substituted iso- monly used Lewis acids, such as AlCl3, FeCl3,
indoline with a carboxyl group is a privileged struc- BF3·Et2O and Sc(OTf)3, as versatile catalysts for the
In summary, we have successfully identified com-
AHCTUNGTRENNUNG
ture in many biologically active compounds and natu- benzylic addition of 2-substituted azaarenes to N-sul-
ral products.[12] In this manner, this protocol provides fonylaldimines to afford heterocycle-containing
À
a potentially rapid and modular access to a variety of amines via C H bond activation. This protocol pro-
heterocycle-containing isoindoline structural motifs vides a reliable and rapid approach for the synthesis
with different azaarenes, which are highly desirable in of isoindolinones and isoindolines that are of tremen-
À
medicinal chemistry.
dous importance in medicinal chemistry via the C H
bond functionalization-triggered tandem reactions.
This chemistry provides a mechanistically novel and
synthetically useful transformation of azaarenes to
important medicinal heterocycles.
Experimental Section
Typical Procedure for the Benzylic Addition of 2-
Substituted Azaarenes to Imines
Under argon, ScACTHNUTRGNEUNG(OTf)3 (14.8 mg, 10 mol%), 2,6-lutidine 2a
(0.75 mmol, 80.3 mg), imine 3a (0.3 mmol, 77.7 mg), and dry
PhCF3 (1.5 mL) were added to a screw-cap vial. The mixture
was kept stirring at 1208C and monitored by TLC, after
24 h, the solvent was evaporated under reduced pressure
and the residue was purified by flash column chromatogra-
phy on a silica gel to give the desired product 1aa as a white
1
solid; yield: 88 mg (80%). H NMR (400 MHz, CDCl3): d=
2.29 (s, 3H), 2.52 (s, 3H), 2.92 (m, 2H), 4.56 (t, J=6.4 Hz,
1H), 6.66 (d, J=7.6 Hz, 1H), 6.93 (d, J=7.6 Hz, 1H), 7.01
Figure 1. X-ray crystal structure of the isoindoline 7a.
Adv. Synth. Catal. 2010, 352, 3195 – 3200
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
3199

Bo Qian et al.
COMMUNICATIONS
(d, J=8.0 Hz, 2H), 7.11–7.18 (m, 5H), 7.30 (t, J=7.6 Hz,
1H), 7.42 (d, J=8.4 Hz, 2H), 7.49 (br, 1H); 13C NMR
(100 MHz, CDCl3): d=21.2, 24.2, 43.6, 57.8, 120.7, 121.2,
126.5, 126.7, 126.9, 127.9, 128.9, 136.9, 137.2, 141.0, 142.3,
156.6, 157.4; HR-MS (ESI): m/z=367.1479, calcd. for
C21H22N2O2S [M+1]: 367.1475.
J. Am. Chem. Soc. 2009, 131, 13888; i) A. Larivꢂe, J. J.
Mousseau, A. B. Charette, J. Am. Chem. Soc. 2008,
130, 52; j) J. J. Mousseau, A. Larivꢂe, A. B. Charette,
Org. Lett. 2008, 10, 1641; k) J. J. Mousseau, J. A. Bull,
A. B. Charette, Angew. Chem. Int. Ed. 2010, 49, 1115;
l) G. Deng, K. Ueda, S. Yanagisawa, K. Itami, C.-J. Li,
Chem. Eur. J. 2009, 15, 333; m) M. Tobisu, I. Hyodo, N.
Chatani, J. Am. Chem. Soc. 2009, 131, 12070.
[6] a) Y. Nakao, K. S. Kanyiva, T. Hiyama, J. Am. Chem.
Soc. 2008, 130, 2448; b) G. Deng, C.-J. Li, Org. Lett.
2009, 11, 1171.
Acknowledgements
Financial support provided by the National Natural Science
Foundation of China (20802085, 20625308), and Chinese
Academy of Sciences is gratefully acknowledged.
[7] B. Qian, S. Guo, J. Shao, Q. Zhu, L, Yang, C. Xia, H.
Huang, J. Am. Chem. Soc. 2010, 132, 3650.
[8] Similar metal enamides have been reported, see: a) U.
Pieper, D. Stalke, Organometallics 1993, 12, 1201;
b) W.-P. Leung, H. K. Lee, L.-H. Weng, B. S. Luo, Z.-Y.
Zhou, T. C. W. Mak, Organometallics 1996, 15, 1785;
c) P. C. Andrews, D. R. Armstrong, C. L. Raston, B. A.
Roberts, B. W. Skelton, A. H. White, J. Chem. Soc.
Dalton Trans. 2001, 996; d) D. Thomas, W. Baumann,
A. Spannenberg, R. Kempe, U. Rosenthal, Organome-
tallics 1998, 17, 2096; e) T. Niwa, H. Yorimitsu, K.
Oshima, Angew. Chem. Int. Ed. 2007, 46, 2643.
References
[1] a) M. C. Bagley, C. Glover, E. A. Merritt, Synlett 2007,
2459; b) G. D. Henry, Tetrahedron 2004, 60, 6043;
c) J. P. Michael, Nat. Prod. Rep. 2005, 22, 627.
[2] For reviews, see: a) I. Nakamura, Y. Yamamoto, Chem.
Rev. 2004, 104, 2127; b) G. Zeni, R. C. Larock, Chem.
Rev. 2006, 106, 4644.
À
[9] For selected Lewis acid catalyzed direct C H function-
À
alization, see: a) M. Tobisu, N. Chatani, Angew. Chem.
Int. Ed. 2006, 45, 1683; b) S. J. Pastine, K. M. McQuaid,
D. Sames, J. Am. Chem. Soc. 2005, 127, 12180; c) S. J.
Pastine, D. Sames, Org. Lett. 2005, 7, 5429; d) K. M.
McQuaid, D. Sames, J. Am. Chem. Soc. 2009, 131, 402;
e) P. A. Vadola, D. Sames, J. Am. Chem. Soc. 2009, 131,
16525; f) K. M. McQuaid, J. Z. Long, D. Sames, Org.
Lett. 2009, 11, 2792; g) T. Tsuchimoto, Y. Ozawa, R.
Negoro, E. Shirakawa, Y. Kawakami, Angew. Chem.
Int. Ed. 2004, 43, 4231.
[3] For reviews on C H activation, see: a) V. Ritleng, C.
Sirlin, M. Pfeffer, Chem. Rev. 2002, 102, 1731; b) F. Ka-
kiuchi, N. Chatani, Adv. Synth. Catal. 2003, 345, 1077;
c) A. R. Dick, M. S. Sanford, Tetrahedron 2006, 62,
2439; d) J.-Q. Yu, R. Giri, X. Chen, Org. Biomol.
Chem. 2006, 4, 4041; e) D. Alberico, M. E. Scott, M.
Lautens, Chem. Rev. 2007, 107, 174; f) B.-J. Li, S. Yang,
Z.-J. Shi, Synlett 2008, 949; g) X. Chen, K. M. Engle,
D.-H. Wang, J.-Q. Yu, Angew. Chem. Int. Ed. 2009, 48,
5094; h) C.-L. Sun, B.-J. Li, Z.-J. Shi, Chem. Commun.
2010, 677.
[10] a) E. J. Cornish, G. E. Lee, W. R. Wragg, Nature 1963,
197, 1296; b) T. L. Gilchrist, Heterocyclic Chemistry,
Addison Wesley: Essex, England, 1997, Vol. 3; c) E.
Valencia, A. J. Freyer, M. Shamma, V. Fajardo, Tetrahe-
dron Lett. 1984, 25, 599; d) B. Protevin, C. Tordjman, P.
Pastoureau, J. Bonnet, G. De Nanteuil, J. Med. Chem.
2000, 43, 4582; e) T. L. Stuk, B. K. Assink, R. C. Bates,
D. T. Erdman, V. Fedij, S. M. Jennings, J. A. Lassig,
R. J. Smith, T. L. Smith, Org. Process Res. Dev. 2003, 7,
851; f) E. R. Bonfield, C.-J. Li, Adv. Synth. Catal. 2008,
350, 370; g) Q. Zhu, H. Huang, D. Shi, Z. Shen, C. Xia,
Org. Lett. 2009, 11, 4536; h) S. Guo, Y. Xie, X. Hu, C.
Xia, H. Huang, Angew. Chem. Int. Ed. 2010, 49, 2728.
[11] CCDC 776540 contains the supplementary crystallo-
graphic data for the compound 7a. These data can be
obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
[12] a) Q. Shi, P. L. Ornstein, K. Briner, T. I. Richardson,
M. B. Arnold, R. T. Backer, J. L. Buckmaster, E. J.
Canada, C. W. Doecke, L. W. Hertel, N. Honigschmidt,
H. M. Hsiung, S. Husain, S. L. Kuklish, M. J. Martinelli,
J. T. Mullaney, T. P. OꢀBrien, M. R. Reinhard, R. Roth-
haar, J. Shah, Z. Wu, C. Xue, J. M. Zgombick, M. J.
Fisher, Bioorg. Med. Chem. Lett. 2006, 16, 2341; b) K.
Briner, C. W. Doecke, V. Mancuso, M. J. Martinelli,
T. I. Richardson, R. R. Rothhaar, Q. Shi, C. Xie, U.S.
Patent 2004/82590, 2004.
À
[4] For selected examples on the C H functionalization of
pyridine, see: a) E. J. Moore, W. R. Pretzer, T. J.
OꢀConnell, J. Harris, L. LaBounty, L. Chou, S. S.
Grimmer, J. Am. Chem. Soc. 1992, 114, 5888; b) M.
Murakami, S. Hori, J. Am. Chem. Soc. 2003, 125, 4720;
c) F. Kakiuchi, K. Tsuchiya, M. Matsumoto, E. Mizush-
ima, N. Chatani, J. Am. Chem. Soc. 2004, 126, 12792;
d) K. Godula, B. Sezen, D. Sames, J. Am. Chem. Soc.
2005, 127, 3648; e) D. Kalyani, N. R. Deprez, L. V.
Desai, M. S. Sanford, J. Am. Chem. Soc. 2005, 127,
7330; f) J. C. Lewis, R. G. Bergman, J. A. Ellman, J.
Am. Chem. Soc. 2007, 129, 5332; g) A. M. Berman,
J. C. Lewis, R. G. Bergman, J. A. Ellman, J. Am. Chem.
Soc. 2008, 130, 14926; h) M. Wasa, B. T. Worrel, J.-Q.
Yu, Angew. Chem. Int. Ed. 2010, 49, 1275.
[5] For selected examples, see: a) L.-C. Campeau, S. Rous-
seaux, K. Fagnou, J. Am. Chem. Soc. 2005, 127, 18020;
b) J.-P. Leclerc, K. Fagnou, Angew. Chem. Int. Ed.
2006, 45, 7781; c) L.-C. Campeau, M. Bertrand-Laperle,
J.-P. Leclerc, E. Villemure, S. Gorelsky, K. Fagnou, J.
Am. Chem. Soc. 2008, 130, 3266; d) L.-C. Campeau,
D. J. Shipper, K. Fagnou, J. Am. Chem. Soc. 2008, 130,
3276; e) D. J. Schipper, L.-C. Campeau, K. Fagnou, Tet-
rahedron 2009, 65, 3155; f) K. S. Kanyiva, Y. Nakao, T.
Hiyama, Angew. Chem. Int. Ed. 2007, 46, 8872; g) S. H.
Cho, S. J. Hwang, S. Chang, J. Am. Chem. Soc. 2008,
130, 9254; h) J. Wu, X. Cui, L. Chen, G. Jiang, Y. Wu,
3200
asc.wiley-vch.de
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 3195 – 3200