Regio- and stereoselective allylic C-H arylation with electron-deficient arenes by 1,1′-Bi-2-naphthol-palladium cooperation

Article abstract of DOI:10.1021/ol501247b

A palladium-catalyzed allylic C-H arylation reaction with electron-deficient arenes with high regio- and stereoselectivity is reported. This work represents the first successful use of 1,1′-bi-2-naphthol as the ancillary ligand in allylic C-H activation, which is the key factor for chemoselectivity. Furthermore, high selectivity allylic C-H acetoxylation and amination were also successfully achieved under the same catalytic system.

Full text of DOI:10.1021/ol501247b

Letter
pubs.acs.org/OrgLett
Regio- and Stereoselective Allylic C−H Arylation with Electron-
Deficient Arenes by 1,1′-Bi-2-naphthol−Palladium Cooperation
Gang-Wei Wang,† An-Xi Zhou,† Shi-Xia Li,† and Shang-Dong Yang*,†,‡
†State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. China
‡State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of
Sciences, Lanzhou, 730000, P. R. China
S
* Supporting Information
ABSTRACT: A palladium-catalyzed allylic C−H arylation
reaction with electron-deficient arenes with high regio- and
stereoselectivity is reported. This work represents the first
successful use of 1,1′-bi-2-naphthol as the ancillary ligand in
allylic C−H activation, which is the key factor for chemo-
selectivity. Furthermore, high selectivity allylic C−H acetox-
ylation and amination were also successfully achieved under the same catalytic system.
Scheme 1. Approaches for Allylic Arylation with Electron-
Deficient Arenes
llylic C−H bond activation has emerged as a highly
3
Avaluable strategy for sp C−X (X = C, N, O, etc.) coupling
reactions because of its wide variety of substrates and high atom
economy compared with traditional Trost−Tsuji-type reac-
tions.1 The activation has also demonstrated promise as an
excellent example of C−H functionalization2 with high
selectivity, which represents a frontier challenge for synthetic
chemistry. During the past decade, great efforts have been
expended in order to develop high-selectivity allylic C−H
functionalization. Numerous groundbreaking results have been
achieved, including allylic C−H oxygenation,3 alkylation,4 and
amination,5 as well as other types of allylic C−H functionaliza-
tions.6 In particular, palladium-catalyzed allylic C−H activation
has shown great advantages in both the substrates scope and
selectivity. Among these works, ancillary ligands play important
roles in many cases: they favor the formation of π-
allylpalladium intermediate and they also control regioselectiv-
ity and stereoselectivity. As the most successful and effective
ligand, the bis-sulfoxide ligand has shown powerful applicability
in catalytic allylic C−H esterification,3c,d,h,l,n alkylation,4c,e,g
amination,4b,d,f,j Heck addition,7 dehydrogenation,6h and
fluorination.6l Although a few other different ligands such as
sulfoxide derivatives3b,j,o (including DMSO3a,k,5a,6s) and 4,5-
diazafluorenone were also used,3i further investigation into
cheaper and universal ligands to promote palladium-catalyzed
allylic C−H activation with excellent regioselectivity and
stereoselectivity are particularly desirable.
with polyfloroarenes with the hope of avoiding these defects.
To the best of our knowledge, reports of allylic C−H arylation
in high selectivity, either with electron-rich or electron-deficient
arylation reagents, have been rare.6s,7a,12 Herein, we wish to
disclose a novel palladium-catalyzed high selectivity allylic C−H
arylation with a series of electron-deficient arenes. For the first
time, 1,1′-bi-2-naphthol was used as the ancillary ligand for
allylic C−H activation and proved to be the key element for
reaction selectivity (B, Scheme 1). More specifically, allylic C−
H acetoxylation and amination also proceed within the catalytic
system in moderate yield with excellent selectivity. In particular,
the easily accessible 1,1′-bi-2-naphthol and its derivatives will
enrich choices for allylic C−H activation with high selectivity.
To begin our study, we chose allylbenzene 1a and
pentafluorobenzene as model substrates to identify suitable
reaction conditions. In many cases, the ligands usually play an
important role in allylic C−H activation; a series of commonly
In recent years, polyfloroarenes have been shown to exhibit
unique properties for pharmaceutical, material, and electronic
devices.8 The number of reports describing the synthesis of
allylic electron-deficient polyfloroarenes has seen a recent surge.
These researches, however, elegant, nevertheless require
prefunctionalized substrates such as allylic phosphates,9 allylic
carbonate,10 and allylic halides,11 which put limits on the scope
of the substrate and lead to tediously long steps (A, Scheme 1).
Thus, we focus our attention on directly allylic C−H arylation
Received: May 1, 2014
Published: May 12, 2014
© 2014 American Chemical Society
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Letter
used N- and P-ligands for palladium-catalyzed C−H activation
were first evaluated2g,13 in the presence of 10 mol % of
Pd(OAc)2 as catalyst, 1.5 equiv of Ag2CO3 as oxidant, as well as
the base for initial deprotonation of pentafluorobenzene to
afford nucleophilic reagent.14 The results showed that 2,2-
bipyridine (L1), 1,2-diphenylethane-1,2-diamine (L5), and
monoprotected amino acid ligand L9 were totally ineffective
for this transformation (Table 1, entries 1, 5, and 9), and L2,
for the catalytic system (Table 1, entries 14 and 15). We then
examined various additives in order to improve catalytic
efficiency. Indeed, the introduction of basic additives
significantly increased the yield of allylic arylation product,
and the desired product was obtained in 73% yield with
excellent regio- and stereoselectivity in the presence of 50 mol
% of NaOAc. In fact, this yield is relatively high yield compared
to many other allylic C−H activation reactions. As the 1,1′-bi-2-
naphthol could efficiently control regio- and stereoselectivity of
the allylic arylation, we finally concentrated our optimization on
various derivatives of 1,1′-bi-2-naphthol ligands15 with the goal
of increasing the yield of 3a even higher. Although the products
were obtained in excellent yield, the relatively low selectivity
acted to reduce the overall efficiency of L11 (Table 1, entry
22). Compared to 1,1′-bi-2-naphthol (L10), L14 obtained the
products in a slightly lower yield with excellent selectivity
(Table 1, entry 25); L12, L13, and L15 provided relatively
worse results both in yield and selectivity (Table 1, entries 23,
24, and 26). If the 1,1′-bi-2-naphthol was removed from the
reaction system, the regio- and stereoselectivity of the allylic
arylation would be decreased (Table 1, entry 27). Finally, we
fixed on Table 1, entry 21, as the optimal reaction conditions.
In order to demonstrate the generality of this allylic C−H
arylation reaction, the substrate scope was investigated under
optimized conditions (Scheme 2). We first surveyed the
compatibility of the olefin partners. Arylation products were
obtained in moderate to good yields with excellent regio- and
stereoselectivity, regardless of whether an electron-donating
group (CH3, OCH3) or electron-withdrawing group (F, Cl, Br,
CF3, C(O)CH3) was introduced on the aryl moiety. Aryl C−Cl
and aryl C−Br bonds were well tolerated under the catalytic
system, which provided opportunities for further functionaliza-
tion (3d, 3e). Allylpentafluorobenzene could work well with
pentafluorobenzene and obtain the highest yield of desire
product (3i). Besides substituted allylbenzene, aliphatic alkenes,
for example, 1-decene and 4-substituted-1-butene, were also
suitable substrates for this allylic arylation. Indeed, the products
were obtained in synthetically useful yields, although the ratios
of Heck-type isomers were increased, and no branched isomers
were detected (3j, 3k). Allylcyclohexane provided the desired
product in a moderate yield with relatively good selectivity (3l).
Subsequently, a series of electron-deficient arenes were
introduced into the reaction system. Substituted tetrafluor-
obenzenes with different electronic substituents (OCH3, CF3)
were found to be complete substrates and afforded the products
in good yields with excellent selectivity (3p, 3q). 1,2,4,5-
Tetrafluorobenzene and 1,2,3,5-tetrafluorobenzene furnished
the products in moderate yields without Z-allylated or branched
isomers, and only trace amounts of diallylated products were
detected by GC (3n, 3o). 2,3,5,6-Tetrafluoropyridine could
give a relatively high yield of the desired product exclusively
(3r). 1,3,5-Trifluorobenzene and 1,3-difluorobenzene were also
successfully allylated in reasonable yields with good selectivity
(3s, 3t). It is noteworthy that other types of electron-deficient
arenes such as substituted chlorobenzene could also undergo
the allylated reaction and gave products in low yields with
excellent selectivity (3u, 3v). Since these substrates had a
relatively low reactivity and often failed to give the
corresponding product even in the allylic substitution reaction,
this result was truly an exciting breakthrough.
a
Table 1. Reaction Conditions Screening
a
The reaction was carried out with palladium (10 mol %), ligand (20
mol %), oxidant (1.5 equiv), additives (50 mol %), 1a (0.30 mmol),
and 2a (1.20 mmol) in solvent (1.0 mL) at 100 °C for 24 h under
b
argon. For L1−L15 see the Supporting Information. Yield of isolated
c
product. Determined by 1H NMR and 19F NMR spectroscopy.
d
Trace amounts of branch product were detected.
L3, and L8 provided only trace amounts of the desired product
(Table 1, entries 2, 3, and 8). When 1,4-bis(oxazol-2-
yl)benzene (L4) was used as the ligand (Table 1, entry 4),
the desired linear allylated product 3a was obtained in low yield
with poor regioselectivity. Triphenylphosphine (L6) and 2,2′-
bis(diphenylphosphino)-1,1′-binaphthyl (L7) gave the same
results of low yield and relatively poor regioselectivity (Table 1,
entries 7 and 8). However, we were delighted to observe that
1,1′-bi-2-naphthol (L10) had a substantial influence on the
reaction (Table 1,entry 10) and furnished the intermolecular
allylic C−H arylation product 3a in 24% yield with excellent
regio- and stereoselectivity (3a/4a > 97:3 and no branched or
Z-allylated isomers were observed). We subsequently used 1,1′-
bi-2-naphthol as the ligand to further test the solvent, and DME
(1,2-dimethoxyethane) was found to be the best choice (Table
1, entries 11−13). Other effective palladium catalysts such as
PdCl2 and Pd(TFA)2 also were examined and only gave trace
amounts of the desired product (Table 1, entries 16 and 17).
Other screenings of silver sources proved inferior to Ag2CO3
In order to demonstrate the broad applicability of this
catalytic system, we carried out allylic C−H acetoxylation and
amination under standard reaction conditions. Using 4 equiv of
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Letter
a
Scheme 2. Scope of Allylic C−H Arylation
Scheme 3. Allylic C−H Acetoxylation and Amination
Scheme 4. Plausible Mechanism of Allylic C−H Arylation
catalyzed allylic C−H activation, π-allylpalladium complex B is
formed. At the same time, Ag2CO3 works as the base for initial
deprotonation of pentafluorobenzene to afford nucleophilic
reagent, which subsequently reacts with B and generates
complex D. Finally, reductive elimination of D results in
formation of the allylic C−H arylation products and Pd(0)
species, which is oxidized by silver salts to reinitiate the catalytic
cycle.
In conclusion, we have developed a palladium-catalyzed
allylic C−H arylation reaction with a series of electron-deficient
arenes showing good to excellent regio- and stereoselectivity.
This work represents the first successful use of 1,1′-bi-2-
naphthol as the ancillary ligand in allylic C−H activation, and
high selectivity allylic C−H acetoxylation and amination were
also achieved under the catalytic system. Further investigations
of asymmetric allylic alkylation reactions are in progress.
a
The reaction was carried out with Pd(OAc)2 (10 mol %), 1,1′-Bi-2-
naphthol (20 mol %), Ag2CO3 (1.5 equiv), NaOAc (50 mol %), 1 (0.3
mmol) and 2 (1.2 mmol) in DME (1.0 mL) at 100 °C for 24 h under
b
argon. Without a special note, the isomeric ratio (3a/4a) > 97:3. Run
with Pd(OAc)2; 15 mol % and 18% yield of Heck-type product isomer
was formed. A trace amount of diallylated products were detected by
GC. 7% yield of Heck-type product isomer was formed. Reaction
c
d
e
runs at 120 °C for 48 h.
HOAc as the nucleophiles, allylic C−H acetoxylation was
successfully accomplished in a synthetically useful yield with
excellent selectivity. The same result was obtained in allylic C−
H amination reaction (Scheme 3). We believe that after
appropriate optimization of the catalytic system, yields of the
product will be increased accordingly.
Primary mechanistic studies were carried out by stoichio-
metric reaction of a π-allylpalladium complex with pentafluor-
obenzene (Supporting Information). In the presence of
Ag2CO3 and NaOAc, the product was obtained in 37% yield,
and only trace amounts of desired product were formed in the
absence of Ag2CO3. According to these results, we proposed
the mechanism shown in Scheme 4. The catalytic cycle is
initiated by Pd(OAc)2 coordinating with rac-Binol to form the
activated palladium complex A, and then through palladium-
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental details and characterization data for all new
compounds are provided. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: yangshd@lzu.edu.cn.
Notes
The authors declare no competing financial interest.
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Letter
Chem. Soc. 2010, 132, 11978. (i) Shimizu, Y.; Obora, Y.; Ishii, Y. Org.
Lett. 2010, 12, 1372. (j) Jiang, C.; Covell, D. J.; Stepan, A. F.;
Plummer, M. S.; White, M. C. Org. Lett. 2012, 14, 1386.
ACKNOWLEDGMENTS
■
We are grateful for the NSFC (Nos. 21272100) and Program
for New Century Excellent Talents in University (NCET-11-
0215 and lzujbky-2013-k07) financial support.
(6) For other types of allylic C−H functionalization, see: (a) Li, Z.;
Li, C.-J. J. Am. Chem. Soc. 2006, 128, 56. (b) Davies, H. M. L.;
Coleman, M. G.; Ventura, D. L. Org. Lett. 2007, 9, 4971. (c) Lee, J. M.;
Park, E. J.; Cho, S. H.; Chang, S. J. Am. Chem. Soc. 2008, 130, 7824.
(d) Mo, H.; Bao, W. Adv. Synth. Catal. 2009, 351, 2845. (e) Rakshit,
S.; Patureau, F. W.; Glorius, F. J. Am. Chem. Soc. 2010, 132, 9585.
(f) Li, Q.; Yu, Z.-X. J. Am. Chem. Soc. 2010, 132, 4542. (g) Qin, C.;
Jiao, N. J. Am. Chem. Soc. 2010, 132, 15893. (h) Huang, D.; Wang, H.;
Guan, H.; Huang, H.; Shi, Y. Org. Lett. 2011, 13, 1548. (i) Wang, X.;
Ye, Y.; Zhang, S.; Feng, J.; Xu, Y.; Zhang, Y.; Wang, J. J. Am. Chem. Soc.
2011, 133, 16410. (j) Chen, H.; Cai, C.; Liu, X.; Li, X.; Jiang, H. Chem.
REFERENCES
■
(1) (a) Tsuji, J.; Takahashi, H.; Morikawa, M. Tetrahedron Lett. 1965,
6, 4387. (b) Trost, B. M.; Fullerton, T. J. J. Am. Chem. Soc. 1973, 95,
292. (c) Tsuji, J. Transition Metal Reagents and Catalysts: Innovations in
Organic Synthesis; Wiley: New York, 2000; Chapter 4, p 109. (d) Trost,
B. M.; Crawley, M. L. Chem. Rev. 2003, 103, 2921. (e) Helmchen, G.;
Pfaltz, A. Acc. Chem. Res. 2000, 33, 336.
(2) For selected reviews on C−H activation (a) Chen, M. S.; White,
M. C. Science 2007, 318, 783. (b) Chen, X.; Engle, K. M.; Wang, D.-
H.; Yu, J.-Q. Angew. Chem., Int. Ed. 2009, 48, 5094. (c) Li, C.-J. Acc.
Chem. Res. 2009, 42, 335. (d) Mkhalid, I. A. I.; Barnard, J. H.; Marder,
T. B.; Murphy, J. M.; Hartwig, J. F. Chem. Rev. 2010, 110, 890.
(e) Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010, 110, 1147.
Commun. 2011, 47, 12224. (k) Larsson, J. M.; Zhao, T. S. N.; Szabo,
́
K. J. Org. Lett. 2011, 13, 1888. (l) Stang, E. M.; White, M. C. J. Am.
Chem. Soc. 2011, 133, 14892. (m) Xu, J.; Fu, Y.; Luo, D.-F.; Jiang, Y.-
Y.; Xiao, B.; Liu, Z.-J.; Gong, T.-J.; Liu, L. J. Am. Chem. Soc. 2011, 133,
15300. (n) Parsons, A. T.; Buchwald, S. L. Angew. Chem., Int. Ed. 2011,
50, 9120. (o) Shi, E.; Shao, Y.; Chen, S.; Hu, H.; Liu, Z.; Zhang, J.;
Wan, X. Org. Lett. 2012, 14, 3384. (p) Bigi, M. A.; White, M. C. J. Am.
Chem. Soc. 2013, 135, 7831. (q) Braun, M.-G.; Doyle, A. G. J. Am.
Chem. Soc. 2013, 135, 12990. (r) Sekine, M.; Ilies, L.; Nakamura, E.
Org. Lett. 2013, 15, 714. (s) Jiang, H.; Chen, H.; Yang, W.; Wu, W.
Org. Biomol. Chem. 2014, DOI: 10.1039/C4OB00442F.
(f) Wencel-Delord, J.; Droge, T.; Liu, F.; Glorius, F. Chem. Soc. Rev.
̈
2011, 40, 4740. (g) Yeung, C. S.; Dong, V. M. Chem. Rev. 2011, 111,
1215. (h) Cho, S. H.; Kim, J. Y.; Kwak, J.; Chang, S. Chem. Soc. Rev.
2011, 40, 5068. (i) White, M. C. Synlett. 2012, 23, 2746. (j) Girard, S.
A.; Knauber, T.; Li, C.-J. Angew. Chem., Int. Ed. 2013, 53, 74.
(3) For allylic C−H oxygenation, see: (a) Chen, M. S.; White, M. C.
J. Am. Chem. Soc. 2004, 126, 1346. (b) Chen, M. S.; Prabagaran, N.;
Labenz, N. A.; White, M. C. J. Am. Chem. Soc. 2005, 127, 6970.
(c) Delcamp, J. H.; White, M. C. J. Am. Chem. Soc. 2006, 128, 15076.
(d) Fraunhoffer, K. J.; Prabagaran, N.; Sirois, L. E.; White, M. C. J. Am.
Chem. Soc. 2006, 128, 9032. (e) Pilarski, L. T.; Selander, N.; Bose, D.;
(7) (a) Delcamp, J. H.; Brucks, A. P.; White, M. C. J. Am. Chem. Soc.
2008, 130, 11270. (b) Jiang, C.; Covell, D. J.; Stepan, A. F.; Plummer,
M. S.; White, M. C. Org. Lett. 2012, 14, 1386.
(8) Amii, H.; Uneyama, K. Chem. Rev. 2009, 109, 2119.
(9) (a) Yao, T.; Hirano, K.; Satoh, T.; Miura, M. Angew. Chem., Int.
Ed. 2011, 50, 2990. (b) Makida, Y.; Ohmiya, H.; Sawamura, M. Angew.
Chem., Int. Ed. 2012, 51, 4122.
́
Szabo, K. J. Org. Lett. 2009, 11, 5518. (f) Stang, E. M.; White, M. C.
Nature Chem. 2009, 1, 547. (g) Campbell, A. N.; White, P. B.; Guzei,
L. A.; Stahl, S. S. J. Am. Chem. Soc. 2010, 132, 15116. (h) Henderson,
W. H.; Check, C. T.; Proust, N.; Stambuli, J. P. Org. Lett. 2010, 12,
824. (i) Thiery, E.; Aouf, C.; Belloy, J.; Harakat, D.; Bras, L. J.; Muzart,
J. J. Org. Chem. 2010, 75, 1771. (j) Vermeulen, N. A.; Delcamp, J. H.;
White, M. C. J. Am. Chem. Soc. 2010, 132, 11323. (k) Takenaka, K.;
Akita, M.; Tanigaki, Y.; Takizawa, S.; Sasai, H. Org. Lett. 2011, 13,
(10) Fan, S.; Chen, F.; Zhang, X. Angew. Chem., Int. Ed. 2011, 50,
5918.
(11) Yu, Y.-B.; Fan, S.; Zhang, X. Chem.Eur. J. 2012, 18, 14643.
(12) Allylic arylation products as side products: Jung, Y. C.; Mishra,
R. K.; Yoon, C. H.; Jung, K. W. Org. Lett. 2003, 5, 2231.
(13) Engle, K. M.; Yu, J.-Q. J. Org. Chem. 2013, 78, 8927.
(14) (a) Wei, Y.; Kan, J.; Wang, M.; Su, W.; Hong, M. Org. Lett.
2009, 11, 3346. (b) Zhang, X.; Fan, S.; He, C.-Y.; Wan, X.; Min, Q.-Q.;
Yang, J.; Jiang, Z.-X. J. Am. Chem. Soc. 2010, 132, 4506. (c) He, C.-Y.;
Fan, S.; Zhang, X. J. Am. Chem. Soc. 2010, 132, 12850. (d) Li, H.; Liu,
J.; Sun, C.-L.; Li, B.-J.; Shi, Z.-J. Org. Lett. 2011, 13, 276. (e) Chen, F.;
Feng, Z.; He, C.-Y.; Wang, H.-Y; Guo, Y.-L; Zhang, X. Org. Lett. 2012,
14, 1176. (f) Chen, F.; Min, Q.-Q.; Zhang, X. J. Org. Chem. 2012, 77,
2992.
́
3506. (l) Pilarski, L. T.; Janson, P. G.; Szabo, K. J. J. Org. Chem. 2011,
76, 1503. (k) Chen, H.; Jiang, H.; Cai, C.; Dong, J.; Fu, W. Org. Lett.
2011, 13, 992. (l) Gormisky, P. E.; White, M. C. J. Am. Chem. Soc.
2011, 133, 12584. (m) Le, C.; Kunchithapatham, K.; Henderson, W.
H.; Check, C. T.; Stambuli, J. P. Chem.Eur. J. 2013, 19, 11153.
(n) Mann, S. E.; Aliev, A. E.; Tizzard, G. J.; Sheppard, T. D.
Organometallics 2011, 30, 1772. (o) Check, C. T.; Henderson, W. H.;
Wray, B. C.; Eynden, M. J. V.; Stambuli, J. P. J. Am. Chem. Soc. 2011,
133, 18503. (p) Sharma, A.; Hartwig, J. F. J. Am. Chem. Soc. 2013, 135,
17983.
(15) Chen, Y.; Yekta, S.; Yudin, A. K. Chem. Rev. 2003, 103, 3155.
(4) For allylic C−H alkylation, see: (a) Franzen
́
, J.; Backvall, J.-E. J.
̈
Am. Chem. Soc. 2003, 125, 6056. (b) Piera, J.; Narhi, K.; Backvall, J.-E.
̈
̈
Angew. Chem., Int. Ed. 2006, 45, 6911. (c) Lin, S.; Song, C. X.; Cai, G.
X.; Wang, W. H.; Shi, Z.-J. J. Am. Chem. Soc. 2008, 130, 12901.
(d) Persson, A. K.; Backvall, J.-E. Angew. Chem., Int. Ed. 2010, 49,
̈
4624. (e) Young, A. J.; White, M. C. J. Am. Chem. Soc. 2008, 130,
14090. (f) Taber, D. F.; Nelson, D. F. J. Org. Chem. 2010, 76, 1874.
(g) Young, A. J.; White, M. C. Angew. Chem., Int. Ed. 2011, 50, 6824.
(h) Li, L.; Chen, Q.-Y.; Guo, Y. Chem. Commun. 2013, 49, 8764.
(i) Trost, B. M.; Thaisrivongs, D. A.; Donckele, E. J. Angew. Chem., Int.
Ed. 2013, 52, 1523. (j) Chen, G.-H.; Chen, K.; Shi, Z.-J. Chem. Catal.
Chem. 2013, 5, 1289.
(5) For allylic C−H amination, see: (a) Larock, R. C.; Hightower, T.
R.; Hasvold, L. A.; Peterson, K. P. J. Org. Chem. 1996, 61, 3584.
(b) Fraunhoffer, K. J.; White, M. C. J. Am. Chem. Soc. 2007, 129, 7274.
(c) Liu, G.; Yin, G.; Wu, L. Angew. Chem. Int. Ed 2008, 47, 4733.
(d) Reed, S. A.; White, M. C. J. Am. Chem. Soc. 2008, 130, 3316.
(e) Wu, L.; Qiu, S.; Liu, G. Org. Lett. 2009, 11, 2707. (f) Reed, S. A.;
Mazzotti, A. R.; White, M. C. J. Am. Chem. Soc. 2009, 131, 11707.
(g) Nahra, F.; Liron, F.; Prestat, G.; Mealli, C.; Messaoudi, A.; Poli, G.
Chem.- Eur. J. 2009, 15, 11078. (h) Yin, G.; Wu, Y.; Liu, G. J. Am.
3121
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