Rhodium-catalyzed cascade oxidative annulation leading to substituted naphtho[1,8- bc ]pyrans by sequential cleavage of C(sp2)-H/C(sp 3)-H and C(sp2)-H/O-H Bonds

Article abstract of DOI:10.1021/ja3075242

The cascade oxidative annulation reactions of benzoylacetonitrile with internal alkynes proceed efficiently in the presence of a rhodium catalyst and a copper oxidant to give substituted naphtho[1,8-bc]pyrans by sequential cleavage of C(sp²)-H/C(sp³)-H and C(sp²)-H/O-H bonds. These cascade reactions are highly regioselective with unsymmetrical alkynes. Experiments reveal that the first-step reaction proceeds by sequential cleavage of C(sp²)-H/C(sp³)-H bonds and annulation with alkynes, leading to 1-naphthols as the intermediate products. Subsequently, 1-naphthols react with alkynes by cleavage of C(sp²)-H/O-H bonds, affording the 1:2 coupling products. Moreover, some of the naphtho[1,8-bc]pyran products exhibit intense fluorescence in the solid state.

Full text of DOI:10.1021/ja3075242

Communication
pubs.acs.org/JACS
Rhodium-Catalyzed Cascade Oxidative Annulation Leading
to Substituted Naphtho[1,8-bc]pyrans by Sequential Cleavage
of C(sp2)−H/C(sp3)−H and C(sp2)−H/O−H Bonds
Xing Tan,† Bingxian Liu,† Xiangyu Li,† Bin Li,† Shansheng Xu,† Haibin Song,† and Baiquan Wang*,†,‡
†State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, China
S
* Supporting Information
However, very limited substituted 1-naphthol substrates were
ABSTRACT: The cascade oxidative annulation reactions
of benzoylacetonitrile with internal alkynes proceed effi-
ciently in the presence of a rhodium catalyst and a copper
oxidant to give substituted naphtho[1,8-bc]pyrans by se-
quential cleavage of C(sp2)−H/C(sp3)−H and C(sp2)−
H/O−H bonds. These cascade reactions are highly regio-
selective with unsymmetrical alkynes. Experiments reveal that
the first-step reaction proceeds by sequential cleavage of
C(sp2)−H/C(sp3)−H bonds and annulation with alkynes,
leading to 1-naphthols as the intermediate products. Sub-
sequently, 1-naphthols react with alkynes by cleavage of
C(sp2)−H/O−H bonds, affording the 1:2 coupling products.
Moreover, some of the naphtho[1,8-bc]pyran products exhibit
intense fluorescence in the solid state.
examined in their work. Therefore, it is of great interest to es-
tablish new methods to synthesize substituted naphtho[1,8-bc]-
pyrans from the accessible starting materials. Herein, we provide
a more straightforward approach toward these compounds from
readily available substituted benzoylacetonitriles.
ransition-metal-catalyzed direct C−H bond transforma-
Ttions have attracted significant interest, because these
approaches allow the use of cheaper and more readily available
starting materials.1 In particular, the rhodium-2 and ruthenium3-
catalyzed oxidation couplings of various aromatic substrates with
alkynes have been extensively investigated, leading to diverse
heterocyclic compounds (eqs 1 and 2). Among these examples,
most of them proceed by cleavage of C−H/N−H or C−H/
O−H bonds, followed by annulation with alkynes. Encouraged
by these heterocycle syntheses, we hope to apply this cyclization
methodology to construct six-membered carbocylic skeletons
such as naphthalene derivatives. In our initial attempt, we used
benzoylacetonitrile as a substrate, expecting to synthesize 1-naphthol
product by cleavage of C(sp2)−H/C(sp3)−H bonds. To our
surprise, not the 1:1 but the unexpected 1:2 coupling product,
a naphtho[1,8-bc]pyran derivative, was obtained in good yield
(eq 3).
Substituted naphtho[1,8-bc]pyran moieties are an important
structural unit present in various naturally occurring and syn-
thetic compounds that exhibit a broad range of interesting bio-
logical4 and optoelectronic properties.5 However, only a few
synthetic routes are reported in the literature, and most of them
require a complicated multistep process or inaccessible start-
ing materials.4−6 Recently, groups of Satoh and Miura,2k and
Ackermann3g respectively reported rhodium- and ruthenium-
catalyzed naphtho[1,8-bc]pyran synthesis from a 1-naphthol
substrate via hydroxyl-directed C−H bond activation (eq 2).
By treating benzoylacetonitrile (1a) (0.15 mmol) with
diphenylacetylene (2a) (0.3 mmol) in the presence of catalytic
amounts of [Cp*RhCl2]2 (0.015 mmol) and Cu(OAc)2·H2O
(0.6 mmol) in DMF at 100 °C for 10 h, as described above, the
1:2 coupling product, 2,3,7,8-tetraphenylnaphtho[1,8-bc]pyran-
9-carbonitrile (3aa), was obtained in 59% yield (for detailed
optimization studies, see Table S1 in the Supporting Information
1
(SI)). The structure of 3aa was confirmed by its H and 13C
NMR spectra, mass spectrometry data, and single-crystal X-ray
diffraction analysis. Interestingly, using an equal amount of 1a
and 2a ([1a] = [2a] = 0.3 mmol), the 1:1 coupling product was
still not observed, while the yield of 3aa was increased to 81%.
When using a lower ratio (0.65: 1) of 1a:2a, the yield of 3aa was
similar (82%). Under the optimal reactant ratio, MeCN was also
an effective solvent and gave 3aa in 81% yield. In contrast, using
other solvents (PhMe, tAmOH, dioxane, PhCl) or other oxidants
(Ag2CO3, AgOAc), the yield of 3aa was significantly lower.
Received: August 4, 2012
© XXXX American Chemical Society
A
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The use of AgSbF6, Et3N, or NaOAc as an additive was ineffective
in increasing the yield of 3aa. Moreover, decreasing the loading
of the [Cp*RhCl2]2 resulted in a significantly lower yield.
With the optimal reaction conditions in hand, various
substituted benzoylacetonitriles (1a−m) were treated with
diphenylacetylene 2a and gave corresponding naphtho[1,8-bc]-
pyran derivatives (Table 1). Thus, 4-methyl, 4-phenyl, and 4-tert-
3la-2. Moreover, the effect of changing the nitrile group in 1a
to other substituents was also investigated. Thus, ethyl ben-
zoylacetate (1n) and 2-nitro-1-phenylethanone (1o) reacted
successfully with 2a, although low to moderate yields were
observed (47% for 3na and 23% for 3oa). Unfortunately, under
the current reaction conditions, 1-phenylbutane-1,3-dione (1p)
failed to afford the corresponding cycloadduct, possibly because
of the formation of a β-diketonate−rhodium complex with
[Cp*RhCl2]2.7
In addition to 2a, other symmetrical alkynes (2b−d) were also
tested for the present reaction. Thus, methyl- (2b), methoxy-
(2c), and fluoro- (2d) substituted diphenylacetylenes reacted
with 1a and afforded the corresponding naphtho[1,8-bc]pyrans
3ab−ad in high yields (73−84%). To give evidence for the re-
gioselectivity of this reaction, a few unsymmetrical alkynes were
employed. In this case, four regioisomeric products could be
possible. Surprisingly, 1-phenyl-1-propyne (2e), 1-phenyl-1-butyne
(2f), and propargylic ether (2g) gave the single regioisomeric prod-
ucts 3ae−3ag in moderate to good yields (53−63%). Unfortu-
nately, no selectivity was achieved when 1:1 ratio of different alkynes
were used in this cascade reaction (see the SI).
Table 1. Scope of Rhodium-Catalyzed Cascade Oxidative
a
Annulation with Alkynes
To further demonstrate the efficiency and practicality of this
cascade reaction, a scale-up reaction was performed. Thus, gram-
scale synthesis of 3aa was achieved in 79% yield.
Most of the naphtho[1,8-bc]pyran derivatives 3 obtained
above showed solid-state fluorescence in a range of 490−580 nm
(see the SI). Notably, 3aa was found to exhibit more intense
luminescence (λemis = 535 nm), and the intensity was almost four
times stronger than that of tris(8-quinolinolato)aluminum
(Alq3) in the preliminary estimation.
Moreover, we tested the reactions of ortho-substituted ben-
zoylacetonitriles with 2a. In this case, there is only one C(sp2)−
H bond activation site, so only one step of the oxidative annula-
tion with alkyne could occur. Under similar reaction conditions,
ortho-substituted 1q and 1r or the α-naphthyl derivative 1s re-
acted effectively with 2a, affording substituted 1-naphthols (4qa
and 4ra) and 4-phenanthrenol (4sa) in low to good yields
(27−62%) (Scheme 1). These results indicate that double
Scheme 1. Rhodium-Catalyzed 1:1 Oxidative Annulation with
a
Alkynes
a
b
Isolated yields are given. MeCN was used as solvent.
butyl substituted benzoylacetonitriles 1b−d afforded naphtho-
[1,8-bc]pyrans 3ba−3da in excellent yields (89−91%). Electron-
rich substrate 1e reacted nicely with 2a and gave 3ea in 92%
yield. In the present catalytic reaction, 4-fluoro-, 4-chloro-, and
4-bromobenzoylacetonitriles 1f−h could also be tolerated,
affording 3fa−3ha in good yields (72−77%). In contrast,
electron-withdrawing 4-trifluoromethyl and 4-nitrobenzoylace-
tonitriles 1i and 1j provided 3ia, 3ja in low to moderate yields
(50% for 3ia and 33% for 3ja). Subsequently, the meta-
substituted benzoylacetonitrile scope was also explored,
generating the expected products in moderate to high yields
with modest regioselectivity. Thus, 3-methyl substituted 1k and
β-naphthyl derivative 1m reacted with 2a to give 3ka-1 and
3ma-1 as the major regioisomers, whereas 3-methoxyl sub-
stituted 1l yielded equal amounts of regioisomers 3la-1 and
a
Isolated yields are given.
oxidative insertion of alkynes is a stepwise process, wherein the
1-naphthol acts as an intermediate. Importantly, the reaction offers a
convenient way to synthesize some derivatives of 2-naphthonitrile.
As described above, the Satoh and Miura group has reported the
oxidatve annulation reaction of 1-naphthol with alkyne2k affording
the corresponding naphtho[1,8-bc]pyran product, which supports
our hypothesis that 1-naphthol is an intermediate during the
B
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Journal of the American Chemical Society
Communication
course of these cascade reactions. Therefore, the first-step reaction
should be involving the cleavage of C(sp2)−H/C(sp3)−H bonds.
To the best of our knowledge, no similar transition-metal-catalyzed
oxidative annulation reaction with alkyne by cleavage of C(sp2)−
H/C(sp3)−H bonds has been reported. Very recently, Chen’s group
reported the intermolecular cylization of N-aryl-substituted azole
substrates with alkynes via double C(sp2)−H activation, leading
to aza-fused polycyclic quinolines, using a similar strategy.2b
To gain more insight to the mechanism of these cascade re-
actions, we performed a deuterium competition experiment be-
tween substrate 1a and [D5]-1a (Scheme 2 and SI), and a kinetic
intermediate E, which subsequently undergoes an ortho C−H
bond activation to afford the intermediate D (Path II). Sub-
sequently, the aromatization-driven reductive elimination of C or
D results in 1-naphthol as the first-step product. The mechanism
of the second-step annulation of 1-naphthol with alkyne is
consistent with that reported by Satoh and Miura.2k
When benzoylacetonitrile 1a reacts with unsymmetrical
alkynes (1e−g), single regioisomeric products 3ae−3ag were
obtained. These results reveal that, in the seven-membered
rhodacycle C or D, the phenyl group of the unsymmetrical alkyne
is far away from the phenyl ring of benzoylacetonitrile substrate.
According to the known literatures2 related to regioselective
insertion of an unsymmetrical alkyne to a Rh−C bond (involving
a Rh−C(sp3) bond2m), in the seven-membered rhodacycle the
phenyl group of the alkyne gets close to the Rh-atom and is
far away from the C-atom. So intermediate C is more reasonble
than intermediates D and E, and Path I might be a plausible
mechanism.
Scheme 2. Experiment with Isotopically Labeled Compounds
Recently, the Glorius10 and Cheng11 groups have respectively
developed a rhodium-catalyzed method to synthesize indenols
from aryl ketones (including substituted acetophenones) and
alkynes, via ketone-assisted C−H activation. They proposed a
five-membered rhodacycle intermediate with the O-atom
coordinated to the Rh-atom. In contrast to their five-membered
carbocyclic product synthesis, our results reveal another reaction
path of acetophenones with alkynes via C−H activation and sub-
sequent annulation, affording six-membered carbocyclic prod-
ucts. We envision that the different acidity of the C(sp3)−H
bond at the α-position of acetophenone may be responsible for
the distinct results. The pKa value of 1a in DMSO is 10.2,12 while
that of acetophenone is 24.7.13
In summary, we have developed rhodium-catalyzed cascade
oxidative annulation reactions of benzoylacetonitriles with alkynes,
affording substituted naphtho[1,8-bc]pyrans in good yields. More-
over, these cascade reactions are highly regioselective with unsym-
metrical alkynes. Further experiments revealed that the first-step
reaction proceeds by sequential cleavage of C(sp2)−H/C(sp3)−H
bonds and annulation with an alkyne, leading to 1-naphthols as
the intermediate products. Subsequently, 1-naphthols react with
alkyne by cleavage of C(sp2)−H/O−H bonds, affording the 1:2
coupling products. Some of the naphtho[1,8-bc]pyran products
exhibit intense fluorescence in the solid state, and this cascade
isotope effect (KIE) of kH/kD ≈ 9.0 was observed. In addition,
two parallel independent reactions of 1a and [D5]-1a illustrated a
KIE of kH/kD ≈ 2.8 (see the SI).8 These results indicated that
cleavage of the C−H bond of the phenyl ring was involved in the
rate-determining step.
On the basis of known transition-metal-catalyzed C−H bond
activation/annulation reactions, a possible mechanism is pro-
posed to the present catalytic reaction (Scheme 3). The first
step is likely to be a C(sp3)−H activation process affording a
Rh−C(sp3) intermediate A, owing to the strong acidity of these
C(sp3)−H bonds. Then, a five-membered rhodacycle B is formed
by a subsequent ortho C(sp2)−H activation process (Path I). An
intermolecualr deprotonation process for the C−H activation may
be involved as proposed by the research group of Dixneuf and
Jutand according to the kinetic study.9 Regioselective insertion of
an alkyne into the Rh−C(sp2) or Rh−C(sp3) bond of inter-
mediate B gives the seven-membered rhodacycle C or D, respec-
tively. Alternatively, intermediate A is proposed to give a vinyl
Scheme 3. Proposed Mechanistic Pathway for the Formation of 1-Naphthol Derivatives
C
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Journal of the American Chemical Society
Communication
2008, 130, 16474. (y) Ueura, K.; Satoh, T.; Miura, M. J. Org. Chem.
2007, 72, 5362. (z) Ueura, K.; Satoh, T.; Miura, M. Org. Lett. 2007, 9,
1407.
method may contribute to the design of new molecular materials.
Further applications of this method in the synthesis of other six-
membered carbocyclic ring-containing targets and a detailed
mechanistic investigation are in progress.
(3) For selected examples of ruthenium-catalyzed oxidative
annulations with alkynes via C−H activation, see: (a) Chinnagolla, R.
K.; Jeganmohan, M. Chem. Commun. 2012, 48, 2030. (b) Ackermann,
L.; Wang, L.; Lygin, A. V. Chem. Sci. 2012, 3, 177. (c) Chinnagolla, K. R.;
Jeganmohan, M. Eur. J. Org. Chem. 2012, 417. (d) Ackermann, L.; Lygin,
A. V. Org. Lett. 2012, 14, 764. (e) Ackermann, L.; Pospech, J.; Graczyk,
K.; Rauch, K. Org. Lett. 2012, 14, 930. (f) Chinnagolla, R. K.; Pimparkar,
S.; Jeganmohan, M. Org. Lett. 2012, 14, 3032. (g) Thirunavukkarasu, V.
S.; Donati, M.; Ackermann, L. Org. Lett. 2012, 14, 3416.
(h) Parthasarathy, K.; Senthilkumar, N.; Jayakumar, J.; Cheng, C.-H.
Org. Lett. 2012, 14, 3478. (i) Ackermann, L.; Lygin, A. V.; Hofmann, N.
Angew. Chem., Int. Ed. 2011, 50, 6379. (j) Li, B.; Feng, H.; Xu, S.; Wang,
B. Chem.Eur. J. 2011, 17, 12573. (k) Ackermann, L.; Lygin, A. V.;
Hofmann, N. Org. Lett. 2011, 13, 3278. (l) Ackermann, L.; Fenner, S.
Org. Lett. 2011, 13, 6548.
ASSOCIATED CONTENT
* Supporting Information
■
S
Detailed experimental procedures, characterization of all new
compounds, and X-ray structures of 3aa, 3ka-1, 3la-2, 3ma-1,
3ae, and 3af. This material is available free of charge via the
Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
bqwang@nankai.edu.cn.
■
Notes
(4) For selected papers, see: (a) Shin, D.-Y.; Sim, S. N.; Chae, J.-H.;
Hyun, S.-S.; Seo, S.-Y.; Lee, Y.-S.; Lee, K.-O.; Kim, S.-H.; Lee, Y.-S.;
Jeong, J. M.; Choi, N.-S.; Suh, Y.-G. Bioorg. Med. Chem. Lett. 2004, 14,
4519. (b) Suh, Y.-G.; Shin, D.-Y.; Min, K.-H.; Hyun, S.-S.; Jung, J.-K.;
Seo, S.-Y. Chem. Commun. 2000, 1203. (c) Miki, Y.; Hachiken, H.;
Noguchi, K.; Ohta, M.; Nakano, A.; Takahashi, K.; Takemura, S. Chem.
Pharm. Bull. 1990, 38, 3257. (d) Best., W. M.; Wege, D. Aust. J. Chem.
1986, 39, 647. (e) O’Brien, S.; Smith, D. C. C. J. Chem. Soc. 1963, 2907.
(5) For selected papers, see: (a) Tyson, D. S.; Fabrizio, E. F.; Panzner,
M. J.; Kinder, J. D.; Buisson, J.-P.; Christensen, J. B.; Meador, M. A. J.
Photochem. Photobiol. A 2005, 172, 97. (b) Christensen, J. B. J. Heterocycl.
Chem. 2003, 40, 757. (c) Christensen, J. B.; Johannsen, I.; Bechgaard, K.
J. Org. Chem. 1991, 56, 7055. (d) Christensen, J. B.; Larsen, J.;
Johannsen, I.; Bechgaard, K. Synth. Met. 1991, 41−43, 2311.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the National Natural Science Foundation of China
(Nos. 21072101, 21072097, and 21174068) and the Research
Fund for the Doctoral Program of Higher Education of China
(No. 20110031110009) for financial support.
REFERENCES
■
(1) For selected recent reviews about C−H bond functionalizations,
see: (a) Zhu, C.; Wang, R.; Falck, J. R. Chem.Asian J. 2012, 7, 1502.
(b) Song, G.; Wang, F.; Li, X. Chem. Soc. Rev. 2012, 41, 3651.
(c) Hartwig, J. F. Chem. Soc. Rev. 2011, 40, 1992. (d) Wencel-Delord, J.;
(f) Mortensen, M. B.; Schluter, A.; Sørensen, J.; Christensen, J. B.
̈
Droge, T.; Liu, F.; Glorius, F. Chem. Soc. Rev. 2011, 40, 4740.
̈
Acta Chem. Scand. 1997, 51, 807.
(e) Ackermann, L. Chem. Rev. 2011, 111, 1315. (f) Jazzar, R.; Hitce, J.;
Renaudat, A.; Sofack-Kreutzer, J.; Baudoin, O. Chem.Eur. J. 2010, 16,
2654. (g) Satoh, T.; Miura, M. Chem.Eur. J. 2010, 16, 11212.
(h) Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem. Rev. 2010, 110,
624. (i) Topics in Current Chemistry, C−H Activation; Yu, J.-Q., Shi, Z.-J.,
Eds.; Springer: Berlin, 2010; Vol. 292. (j) Chen, X.; Engle, K. M.; Wang,
D.-H.; Yu, J.-Q. Angew. Chem., Int. Ed. 2009, 48, 5094.
(6) For selected papers, see: (a) Huang, S.; Luo, Y.; Huang, Z.; Wang,
X.; Bu, X.; Liu, P.; Ma, L.; Xie, B.; Liu, Z.; Li, Y.; Chan, A. S. C.; Gu, L.
Syn. Commun. 2006, 36, 2667. (b) Shvartsberg, M. S.; Ivanchikova, I. D.
Tetrahedron Lett. 2000, 41, 771. (c) Miki, Y.; Ohta, M.; Hachiken, H.;
Takemura, S. Synthesis. 1990, 4, 312. (d) Narasimhan, N. S.; Mali, R. S.
Synthesis. 1975, 12, 796.
(7) For a stoichiometric reaction of [Cp*RhCl2]2 with Na(acac)
affording β-diketonate-rhodium complex [Cp*Rh(acac)Cl], see: Rigby,
W.; Lee, H.; Bailey, P. M.; McCleverty, J. A.; Maitlis, P. M. J. Chem. Soc.,
Dalton Trans. 1979, 387.
(8) (a) Wei, Y.; Deb, I.; Yoshikai, N. J. Am. Chem. Soc. 2012, 134, 9098.
(b) Simmons, E. M; Hartwig, J. F. Angew. Chem., Int. Ed. 2012, 51, 3066.
(9) Flegeau, E. F.; Bruneau, C.; Dixneuf, P. H.; Jutand, A. J. Am. Chem.
Soc. 2011, 133, 10161.
(10) Patureau, F. W.; Besset, T.; Kuhl, N.; Glorius, F. J. Am. Chem. Soc.
2011, 133, 2154.
(11) Muralirajan, K.; Parthasarathy, K.; Cheng, C.-H. Angew. Chem.,
Int. Ed. 2011, 50, 4169.
(12) Bordwell, F. G.; Puy, Van der Puy, M.; Vanier, N. R. J. Org. Chem.
1976, 41, 1883.
(13) Mattews, W. S.; Bares, J. E.; Bartmess, J. E.; Bordwell, F. G.;
Cornforth, F. J.; Drucker, G. E.; Margolin, Z.; McCallum, R. J.;
McCollum, G. J.; Vanier, N. R. J. Am. Chem. Soc. 1975, 97, 7006.
(2) For selected examples of rhodium-catalyzed oxidative annulation
with alkynes via C−H acivation, see: (a) Jayakumar, J.; Parthasarathy, K.;
Cheng, C.-H. Angew. Chem., Int. Ed. 2012, 51, 197. (b) Huang, J.; Dong,
L.; Han, B.; Peng, C.; Chen, Y. Chem.Eur. J. 2012, 18, 8896.
(c) Zheng, L.; Ju, J.; Bin, Y.; Hua, R. J. Org. Chem. 2012, 77, 5794.
(d) Zhang, X.; Chen, D.; Zhao, M.; Zhao, J.; Jia, A.; Li, X. Adv. Synth.
Catal. 2011, 353, 719. (e) Wang, Y.-F.; Toh, K. K.; Lee, J.-Y.; Chiba, S.
Angew. Chem., Int. Ed. 2011, 50, 5927. (f) Guimond, N.; Gorelsky, S. I.;
Fagnou, K. J. Am. Chem. Soc. 2011, 133, 6449. (g) Umeda, N.; Hirano,
K.; Satoh, T.; Shibata, N.; Sato, H.; Miura, M. J. Org. Chem. 2011, 76, 13.
(h) Too, P. C.; Chua, S. H.; Wong, S. H.; Chiba, S. J. Org. Chem. 2011,
76, 6159. (i) Song, G.; Gong, X.; Li, X. J. Org. Chem. 2011, 76, 7583.
(j) Wei, X.; Zhao, M.; Du, Z.; Li, X. Org. Lett. 2011, 13, 4636.
(k) Mochida, S.; Shimizu, M.; Hirano, K.; Satoh, T.; Miura, M. Chem.
Asian J. 2010, 5, 847. (l) Guimond, N.; Gouliaras, C.; Fagnou, K. J. Am.
Chem. Soc. 2010, 132, 6908. (m) Rakshit, S.; Patureau, F. W.; Glorius, F.
J. Am. Chem. Soc. 2010, 132, 9585. (n) Hyster, T. K.; Rovis, T. J. Am.
Chem. Soc. 2010, 132, 10565. (o) Stuart, D. R.; Alsabeh, P.; Kuhn, M.;
Fagnou, K. J. Am. Chem. Soc. 2010, 132, 18326. (p) Song, G.; Chen, D.;
Pan, C.; Crabtree, R. H.; Li, X. J. Org. Chem. 2010, 75, 7487.
(q) Morimoto, K.; Hirano, K.; Satoh, T.; Miura, M. Org. Lett. 2010, 12,
2068. (r) Chen, J.; Song, G.; Pan, C.; Li, X. Org. Lett. 2010, 12, 5426.
(s) Su, Y.; Zhao, M.; Han, K.; Song, G.; Li, X. Org. Lett. 2010, 12, 5462.
(t) Too, P.; Wang, Y.-F.; Chiba, S. Org. Lett. 2010, 12, 5688.
(u) Fukutani, T.; Umeda, N.; Hirano, K.; Satoh, T.; Miura, M. Chem.
Commun. 2009, 5141. (v) Mochida, S.; Hirano, K.; Satoh, T.; Miura, M.
J. Org. Chem. 2009, 74, 6295. (w) Umeda, N.; Tsurugi, H.; Satoh, T.;
Miura, M. Angew. Chem., Int. Ed. 2008, 47, 4019. (x) Stuart, D. R.;
Bertrand-Laperle, M.; Burgess, K. M. N.; Fagnou, K. J. Am. Chem. Soc.
D
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