Divergent Synthesis of Trifluoromethyl Sulfoxides and β-SCF3Carbonyl Compounds by Tandem Trifluoromethylthiolation/Rearrangement of Allylic and Propargylic Alcohols

Article abstract of DOI:10.1021/acs.orglett.0c02875

A selenium-catalyzed trifluoromethylthiolation/[2,3]-sigmatropic rearrangement of tertiary allylic and propargylic alcohols which could provide straightforward and facile access to trifluoromethyl sulfoxides was developed. Various allylic and allenic trifluoromethyl sulfoxides were obtained with moderate to excellent yields. Meanwhile, a Lewis acid mediated trifluoromethylthiolation/1,2-rearrangement to synthesize β-SCF3 carbonyl compounds was also accomplished. These two tandem reactions feature with mild reaction conditions and metal-free. During these two reactions, the chemoselectivity of electrophilic trifluoromethylthiolation was revealed.

Full text of DOI:10.1021/acs.orglett.0c02875

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Letter
Divergent Synthesis of Trifluoromethyl Sulfoxides and β‑SCF3
Carbonyl Compounds by Tandem Trifluoromethylthiolation/
Rearrangement of Allylic and Propargylic Alcohols
Deng Zhu, Tong-Mei Ding, Hui-Yun Luo, Hua Ke, and Zhi-Min Chen*
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ABSTRACT: A selenium-catalyzed trifluoromethylthiolation/[2,3]-sigmatropic rearrangement of tertiary allylic and propargylic
alcohols which could provide straightforward and facile access to trifluoromethyl sulfoxides was developed. Various allylic and allenic
trifluoromethyl sulfoxides were obtained with moderate to excellent yields. Meanwhile, a Lewis acid mediated
trifluoromethylthiolation/1,2-rearrangement to synthesize β-SCF3 carbonyl compounds was also accomplished. These two tandem
reactions feature with mild reaction conditions and metal-free. During these two reactions, the chemoselectivity of electrophilic
trifluoromethylthiolation was revealed.
Molecules containing an α-aryl ketone unit have shown
hen compounds are introduced with fluorine-contain-
Wing groups, they usually exhibit unique chemical, many important biological activities (Scheme 1c) and have
received much attention from synthetic chemists.8 Some
physical, and biological properties, which make them have a
valuable strategies for the synthesis of them have been
shown.9 Among them, electrophilic semipinacol rearrangement
of 1,1-diaryl allylic alcohols which could offer a direct route for
the efficient synthesis of β-functional group α-aryl ketones has
been successfully studied.10,11 However, electrophilic trifluor-
omethylthiolation/semipinacol rearrangement of 1,1-diaryl
allylic alcohols has not been reported although some related
reactions have been discovered.12 Inspired by the successful
development of [2,3]-sigmatropic rearrangement and 1,2-
rearrangement and combined with our research interest,12c,13
we envisioned that the efficient construction of γ,γ-diaryl allyl
trifluoromethyl sulfoxides by tandem trifluoromethylthiola-
tion/[2,3]-sigmatropic rearrangement of 1,1-diaryl allylic
alcohols and trifluoromethylthiolation/1,2-rearrangement of
1,1-diaryl allylic alcohols for the preparation of α-aryl β-SCF3
ketones could proceed under appropriate reaction conditions
(Scheme 1d). The development of a divergent synthesis
strategy is a major goal in modern organic synthesis, which is
wide range of applications in the fields of pharmaceutical
industry and agriculture.1 Among them are S(O)nCF3-
containing molecules (n = 0, 1, 2), which are in different
oxidation states of sulfur atom show good electron-with-
drawing character and exceptional lipophilicity, and these
molecular structures are common in many drugs.2 For
instance, trifluoromethionine is a methionine derivative,
fipronil is a highly active insecticide, and ponazuril is used as
an antiparasitic molecule. On the other hand, compounds
containing 1,1-diaryl skeleton are present in a number of
bioactive natural products and pharmaceuticals (Scheme 1b).3
Accordingly, it is important and necessary to explore modular
routes for the efficient construction of S(O)nCF3-containing
compounds4,5 and organic molecules with 1,1-diaryl motifs,6
and the methods for the synthesis of these two types of
compounds have been widely developed, respectively.
However, to the best of our knowledge, no example for the
construction of γ,γ-diarylallyl trifluoromethyl sulfoxides which
contain both of S(O)CF3 and 1,1-diaryl groups and have
broadly potential values has been documented (Scheme 1d),
although Cahard and Shibata have reported the synthesis of
allylic trifluoromethyl sulfoxides by [2,3]-sigmatropic rear-
rangement.7 Therefore, the development of modular methods
for the formation of γ,γ-diarylallyl trifluoromethyl sulfoxides is
essential and in high demand.
Received: August 30, 2020
https://dx.doi.org/10.1021/acs.orglett.0c02875
© XXXX American Chemical Society
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Scheme 1. Representative Bioactive Molecules and
Synthetic Design
Scheme 2. Substrate Scope of Allylic Alcohols for the
a
Synthesis of γ,γ-Diarylallyl Trifluoromethyl Sulfoxides
still highly desirable and challenging until now. For successful
development of the divergent synthesis strategy, to realize the
chemoselectivity of trifluoromethylthiolation (alkene vs
hydroxy group) would be required. Herein, we report our
preliminary results.
1,1-Diphenyl-2-propen-1-ol (1a) was first chosen as a model
substrate to optimize the reaction conditions of the synthesis
of γ,γ-diarylallyl trifluoromethyl sulfoxides. After careful
screening, this reaction was found to be facile with 1.5 equiv
of N-trifluoromethylthiosaccharin 2a (Shen’s reagent5d) in the
presence of diphenyl selenide (PhSePh, 0.1 equiv) as a catalyst
and triethylanmine (3.0 equiv) in dichloromethane at room
temperature, and the desired product 3a was obtained in 86%
isolated yield (for details, see Table S1). It should be noted
that the yield of 3a was only obtained in 52% using Cahard’s
reaction conditions.7b Having determined the optimal reaction
conditions for the synthesis of γ,γ-diarylallyl trifluoromethyl
sulfoxide, the scope of various allylic alcohols was studied
(Scheme 2). First, a series of substrates with the symmetrical
groups on the aromatic ring were tested, and the
corresponding products were obtained in moderate to good
yields (3b−k). It was found that the reaction had good
tolerance for the electrical properties of the groups (3b−f).
Gratifyingly, substrates with multiple substituents on the
phenyl group are suitable for the reaction system and gave
the desired products with moderate to good yields (3g−i). To
our delight, heteroaromatic and cyclic diphenyl compounds
were well tolerated, producing the corresponding products in
70% and 90% yields, respectively (3j−k). Furthermore,
substrates with unsymmetrical groups R1 and R2 were also
subjected to the transformation. We found that the
corresponding products were obtained with moderate yields
and would have a certain Z/E ratio when groups R1 and R2
were different aryls (3l,m). Substrate with phenyl and ethyl
a
Reaction conditions: unless otherwise noted, the reaction was
conducted with 1 (0.1 mmol), 2a5d (0.15 mmol), PhSePh (0.01
mmol), and Et3N (0.3 mmol) in CH2Cl2 (2 mL) at room temperature
b
under Ar. Isolated yield. The ratio was determined by 19F NMR.
c
The yield was determined by crude 19F NMR using PhCF3 as
d
internal standard. DMAP (0.2 equiv) was added in addition.
groups 1o gave the similar result. It is worth noting that the
single product 3n was obtained with 73% yield using
unsymmetrical allylic alcohol 1n as the substrate and the
B
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relative configuration of 3n was assigned by X-ray crystallog-
raphy. Substrates with the symmetrical alkyl groups were
examined, and the reaction still proceeded smoothly albeit with
lower yields than model substrate (3p,q). In particular,
tetrasubstituted alkene product 3q was rapidly obtained
using 1q as substrate. Finally, three different internal (Z)-
alkene substrates (1r−t) were subjected to this system.
Satisfactorily, the desired 2,3-rearrangement products were
obtained with good yields but poor dr values. It should be
noted that the products 3r−t are easily to convert into the
corresponding 1,3-dienes via elimination under acidic con-
ditions at room temperature (for details, see the SI). To
evaluate the utility of 2,3-rearrangement, a 1 mmol scale of 1a
was conducted. To our satisfaction, product 3a was obtained
with 89% yield.
Tandem trifluoromethylthiolation/[2,3]-sigmatropic rear-
rangement of propargylic alcohols which could provide direct
approach to allenic trifluoromethyl sulfoxides, to the best our
knowledge, has not been reported. In order to further broaden
the scope of this reaction, some propargylic alcohols were also
carried out under the standard reaction conditions. To our
delight, the desired allenic trifluoromethyl sulfoxides were
obtained with moderate to excellent yields (Scheme 3). The
ment and explore divergent synthesis strategy, we turned our
attention to study trifluoromethylthiolation/1,2-rearrangement
of 1,1-diaryl allylic alcohols. To our delight, the desired β-SCF3
carbonyl compound 6a was obtained with 62% yield when
substrate 1a was conducted with 2a in the presence of
triethylamine (Et3N, 10 mol %), N-(tert-butoxycarbonyl)-L-
phenylalanine (Boc-L-PHE, 10 mol %) and trimethylchlor-
osilane (TMSCl, 2.0 equiv) in CH3CN at room temperature
under Ar. It is worth noting that racemic compound 6a was
produced, although optically pure compound Boc-L-PHE was
used (for details, see Table S2). With the optimized conditions
in hand, the scope of 1,2-rearrangement was investigated with
various allylic alcohols (Scheme 4). In general, the desired α-
Scheme 4. Substrate Scope of Allylic Alcohols for the
a
Synthesis of β-SCF3 Carbonyl Compounds
Scheme 3. Substrate Scope of Propargylic Alcohols for the
a
Synthesis of Allenic Trifluoromethyl Sulfoxides
a
Reaction conditions: unless otherwise noted, the reaction was
conducted with 4 (0.1 mmol), 2a (0.15 mmol), PhSePh (0.01 mmol),
and Et3N (0.3 mmol) in CH2Cl2 (2 mL) at room temperature under
a
Ar. Isolated yield. The ratio was determined by 19F NMR.
a
Reaction conditions: unless otherwise noted, the reaction was
conducted with 1 (0.1 mmol), 2a (0.15 mmol), Et3N (0.01 mmol),
use of unsymmetrical propargylic alcohol 4b gave the product
5b with diastereoselectivity ratio (dr = 1:1). Tetrasubstituted
allene products were also rapidly produced using internal
alkyne substrates (5e−i). Among them, because phenyl-
acetylenyl alkyl alcohol 4g could not be fully converted,
product 5g was obtained with only 41% yield.
Because 1,1-diaryl allylic alcohols are sensitive to strong
acidic conditions and the migration ability of aryl group is
relatively worse than the expansion ability of cyclobutanol, it is
not easy to realize trifluoromethylthiolation/1,2-rearrangement
of them. Actually, they are not suitable for the previous
reaction system of allylic cyclobutanols which has been
reported by our group.12c To further investigate 1,2-rearrange-
Boc-L-PHE (0.01 mmol), and TMSCl (0.2 mmol) in CH3CN (2 mL)
b
at rt under Ar. Isolated yield. The ratio was determined by 1H NMR.
c
1 mmol scale under −10 °C.
aryl β-SCF3 carbonyls were obtained with moderate yields. It
was found that this 1,2-rearrangement system was sensitive to
electrical properties of substrates. Electron-deficient substrate
1c can give the product with 48% yield while substrate with 3-
fluoro-4-methoxybenzene produced the product 6h with 35%
yield. It should be noted that the product of the preferential
migration of electron-rich group was observed as the main
product, which indicated that the reaction should be a cationic
C
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rearrangement process (6m).9c To our delight, the methyl
group at different positions of phenyl group did not obviously
affect the yield (6u,v). In addition, secondary alcohol
substrates with 1,1-disubstituted alkene 1w and 1x were also
relevant to this reaction, delivering rearranged products 6w and
6x with 61% and 53% yields, respectively. More importantly,
quaternary carbon centers were readily constructed. Trisub-
stituted alkene substrate 1r was applicable in this rearrange-
ment and single product 6r was afforded with 30% yield. The
relative configuration of 6r was determined by X-ray
crystallography(for details, see the SI). Finally, we also tested
propargylic alcohols, however, no desired 1,2-rearranged
product was produced. Likewise, 1 mmol scale 1,2-rearrange-
ment of 1a was conducted, and 6a was produced with 69%
yield which is a little bit higher than 0.1 mmol scale.
11. The intermediate 11 undergoes anti 1,2-migration and
deprotonation to deliver product 6a (Scheme 5b).
In summary, a tandem trifluoromethylthiolation/[2,3]-
sigmatropic rearrangement of tertiary allylic alcohols and
propargylic alcohols was disclosed, which required using
diphenyl selenide as catalyst to achieve moderate to excellent
yields with these two new substrates. Among them, tandem
trifluoromethylthiolation/[2,3]-sigmatropic rearrangement of
propargylic alcohols was discovered for the first time. These
outcomes may give some new insight of selenium catalysis.
Meanwhile, an electrophilic trifluoromethylthiolation/1,2-
rearrangement of 1,1-diaryl-2-propen-1-ols was also explored.
This result required adding triethylamine and Boc-L-PHE to
overcome 1,1-diaryl-2-propen-1-ol deterioration. A divergent
synthesis strategy was successfully developed by simply
regulating the reaction conditions. These two tandem reactions
provide facile access to trifluoromethyl sulfoxides and β-SCF3
carbonyl compounds. Various trifluoromethyl sulfoxides and β-
SCF3 carbonyl compounds were diversely synthesized with
moderate to excellent yields. The catalytic asymmetric manner
of these two reactions is being studied in our lab.
1
Next, some additional experiments including H and 19F
NMR investigations were performed to further understand
these two rearrangements (for details, see the SI). On the basis
of previous works14 and our experimental outcomes, possible
mechanisms for these two transformations are proposed in
Scheme 5. For [2,3]-sigmatropic rearrangement, according the
ASSOCIATED CONTENT
* Supporting Information
Scheme 5. Proposed Mechanism
■
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The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.0c02875.
Experimental procedures, characterizations and analyt-
ical data of products, and NMR spectra (PDF)
Accession Codes
CCDC 2010808 and 2032082 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
■
Zhi-Min Chen − School of Chemistry and Chemical
Engineering, Shanghai Key Laboratory for Molecular
Engineering of Chiral Drugs and Frontiers Science Center for
Transformative Molecules, Shanghai Jiao Tong University,
Shanghai 200240, P.R. China; orcid.org/0000-0002-6988-
8955; Email: chenzhimin221@sjtu.edu.cn
results of 19F NMR, the species 7 could be first formed and the
more active intermediate 8 could be generated in the presence
of diphenyl selenide. The intermediate 8 fast reacts with
hydroxy group of 1a to form the species 9 with the assistance
of triethylamine. The species 9 undergoes [2,3]-sigmatropic
rearrangement to produce trifluoromethyl sulfoxide 3a
(Scheme 5a). The addition of diphenyl selenide accelerates
the reaction rate. For 1,2- rearrangement, the species 10 is first
generated in the presence of reagent 2a, triethylamine, and
Boc-L-PHE, which subsequently reacts with TMSCl to form
compound CF3SCl. The role of triethylamine and Boc-L-PHE
may activate the e N-SCF3 bond through a hydrogen-bonding
interaction. Additionally, we speculated that triethylamine and
Boc-L-PHE could act as buffer agents because 1,1-diaryl-2-
propen-1-ol is perishable under strong acidic conditions. The
active compound CF3SCl reacts with the alkene moiety of 1a
to give trifluoromethyl-substituted thiiranium ion intermediate
Authors
Deng Zhu − School of Chemistry and Chemical Engineering,
Shanghai Key Laboratory for Molecular Engineering of Chiral
Drugs and Frontiers Science Center for Transformative
Molecules, Shanghai Jiao Tong University, Shanghai 200240,
P.R. China
Tong-Mei Ding − School of Chemistry and Chemical
Engineering, Shanghai Key Laboratory for Molecular
Engineering of Chiral Drugs and Frontiers Science Center for
Transformative Molecules, Shanghai Jiao Tong University,
Shanghai 200240, P.R. China
Hui-Yun Luo − School of Chemistry and Chemical Engineering,
Shanghai Key Laboratory for Molecular Engineering of Chiral
Drugs and Frontiers Science Center for Transformative
Molecules, Shanghai Jiao Tong University, Shanghai 200240,
P.R. China
D
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Letter
2015, 17, 1990−1993. (c) Arimori, S.; Takada, M.; Shibata, N. Dalton
Trans. 2015, 44, 19456−19459.
(8) For antihypertensive agent, see: (a) Astles, P. C.; Brown, T. J.;
Harris, N. V.; Harper, M. F.; McCarthy, C.; Porter, B.; Smith, C.;
Walsh, R. J. A. Eur. J. Med. Chem. 1997, 32, 515−522. For antiviral
agent, see: (b) Yu, J.-Q.; Hang, W.; Duan, W.-J.; Wang, X.; Wang, D.-
J.; Qin, X.-M. Phytochem. Lett. 2014, 10, 230−234.
Hua Ke − Engineering Technology Research Center for
Environmental Protection Materials, Pingxiang University,
Pingxiang, Jiangxi 337055, P.R. China
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.0c02875
(9) (a) Palucki, M.; Buchwald, S. L. J. Am. Chem. Soc. 1997, 119,
11108−11109. (b) Culkin, D. A.; Hartwig, J. F. Acc. Chem. Res. 2003,
36, 234−245. (c) Liu, X.-W.; Xiong, F.; Huang, X.-P.; Xu, L.; Li, P.-F.;
Wu, X.-X. Angew. Chem., Int. Ed. 2013, 52, 6962−6966. (d) Li, W.;
Tan, F.; Hao, X.-Y.; Wang, G.; Tang, Y.; Liu, X.-H.; Lin, L.-L.; Feng,
X.-M. Angew. Chem., Int. Ed. 2015, 54, 1608−1611. (e) Huang, Y.;
Smith, K. B.; Brown, M. K. Angew. Chem., Int. Ed. 2017, 56, 13314−
13318.
(10) For selected recent reviews, see: (a) Song, Z.-L.; Fan, C.-A.; Tu,
Y.-Q. Chem. Rev. 2011, 111, 7523−7556. (b) Wang, B.; Tu, Y.-Q. Acc.
Chem. Res. 2011, 44, 1207−1222. (c) Zhang, X.-M.; Tu, Y.-Q.; Zhang,
F.-M.; Chen, Z.-H.; Wang, S.-H. Chem. Soc. Rev. 2017, 46, 2272−
2305. (d) Wu, H.; Wang, Q.; Zhu, J.-P. Eur. J. Org. Chem. 2019, 2019,
1964−1980.
(11) (a) Chen, Z.-M.; Zhang, Q.-W.; Chen, Z.-H.; Li, H.; Tu, Y.-Q.;
Zhang, F.-M.; Tian, J.-M. J. Am. Chem. Soc. 2011, 133, 8818−8821.
̈ ̈
(b) Muller, C. H.; Wilking, M.; Ruhlmann, A.; Wibbeling, B.;
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the NSFC (Nos. 21702135, 21871178) and the
STCSM (19JC1430100) for financial support. This research
also supported by The Program for Professor of Special
Appointment (Eastern Scholar) at Shanghai Institutions of
Higher Learning. We gratefully thank Prof. Yong-Qiang Tu
(Shanghai Jiao Tong University) for helpful comments on this
manuscript.
REFERENCES
■
(1) (a) Isanbor, C.; O’Hagan, D. J. Fluorine Chem. 2006, 127, 303−
319. (b) O’Hagan, D. Chem. Soc. Rev. 2008, 37, 308−319. (c) Yang,
X.; Wu, T.; Phipps, R. J.; Toste, F. D. Chem. Rev. 2015, 115, 826−870.
(2) For methionine analogue, see: (a) Kajander, E. O.; Kubota, M.;
Carrera, C. J.; Montgomery, J. A.; Carson, D. A. Cancer Res. 1986, 46,
2866−2870. For fipronil, see: (b) Aajoud, A.; Raveton, M.; Azrou-
Isghi, D.; Tissut, M.; Ravanel, P. J. Agric. Food Chem. 2008, 56, 3732−
3737. For ponazuril, see: (c) Lindsay, D. S.; Dubey, J. P.; Kennedy,
T. J. Vet. Parasitol. 2000, 92, 165−169.
Hennecke, U. Synlett 2011, 2043−2047. (c) Li, H.; Zhang, F.-M.; Tu,
Y.-Q.; Zhang, Q.-W.; Chen, Z.-M.; Chen, Z.-H.; Li, J. Chem. Sci. 2011,
2, 1839−1841. (d) Chen, Z.-M.; Yang, B.-M.; Chen, Z.-H.; Zhang,
Q.-W.; Wang, M.; Tu, Y.-Q. Chem. - Eur. J. 2012, 18, 12950−12954.
(12) (a) Honeker, R.; Garza-Sanchez, R. A.; Hopkinson, M. N.;
Glorius, F. Chem. - Eur. J. 2016, 22, 4395−4399. (b) Liu, K.; Jin, Q.;
Chen, S.; Liu, P.-N. RSC Adv. 2017, 7, 1546−1552. (c) Xi, C.-C.;
Chen, Z.-M.; Zhang, S.-Y.; Tu, Y.-Q. Org. Lett. 2018, 20, 4227−4230.
(13) (a) Xie, Y.-Y.; Chen, Z.-M.; Luo, H.-Y.; Shao, H.; Tu, Y.-Q.;
Bao, X.-G.; Cao, R.-F.; Zhang, S.-Y.; Tian, J.-M. Angew. Chem., Int. Ed.
2019, 58, 12491−12496. (b) Luo, H.-Y.; Xie, Y.-Y.; Song, X.-F.;
Dong, J.-W.; Zhu, D.; Chen, Z.-M. Chem. Commun. 2019, 55, 9367−
9370. (c) Luo, H.-Y.; Dong, J.-W.; Xie, Y.-Y.; Song, X.-F.; Zhu, D.;
Ding, T.-M.; Liu, Y.-Y.; Chen, Z.-M. Chem. - Eur. J. 2019, 25, 15411−
15418. (d) Ye, A.-H.; Zhang, Y.; Xie, Y.-Y.; Luo, H.-Y.; Dong, J.-W.;
Liu, X.-D.; Song, X.-F.; Ding, T.-M.; Chen, Z.-M. Org. Lett. 2019, 21,
5106−5110. (e) Song, X.-F.; Ye, A.-H.; Xie, Y.-Y.; Dong, J.-W.; Chen,
C.; Zhang, Y.; Chen, Z.-M. Org. Lett. 2019, 21, 9550−9554. (f) Song,
X.-F.; Ding, T.-M.; Zhu, D.; Huang, J.; Chen, Z.-M. Org. Lett. 2020,
22, 7052−7056.
(3) For pimozide, see: (a) Beninger, R. J.; Hahn, B. L. Science 1983,
220, 1304−1306. For amitriptyline, see: (b) Schiffer, R. B.; Herndon,
R. M.; Rudick, R. A. N. Engl. J. Med. 1985, 312, 1480−1482. For
ospemifene, see: (c) Morello, K. C.; Wurz, G. T.; DeGregorio, M. W.
Clin. Pharmacokinet. 2003, 42, 361−372.
(4) For selected recent reviews, see: (a) Chu, L.; Qing, F.-L. Acc.
Chem. Res. 2014, 47, 1513−1522. (b) Toulgoat, F.; Alazet, S.; Billard,
T. Eur. J. Org. Chem. 2014, 2014, 2415−2428. (c) Shao, X.; Xu, C.;
Lu, L.; Shen, Q.-L. Acc. Chem. Res. 2015, 48, 1227−1236. (d) Zhang,
K.; Xu, X.-H.; Qing, F.-L. Youji Huaxue 2015, 35, 556−569.
(e) Zhang, P.-P.; Lu, L.; Shen, Q.-L. Huaxue Xuebao 2017, 75,
744−769. (f) Ni, C.-F.; Hu, M.-Y.; Hu, J.-B. Chem. Rev. 2015, 115,
765−825. (g) Xu, X.-H.; Matsuzaki, K.; Shibata, N. Chem. Rev. 2015,
115, 731−764. (h) Chachignon, H.; Cahard, D. Chin. J. Chem. 2016,
34, 445−454.
(14) (a) Luo, J.; Zhu, Z.; Liu, Y.; Zhao, X. Org. Lett. 2015, 17,
3620−3623. (b) Luo, J.; Liu, X.; Zhao, X. Synlett 2017, 28, 397−401.
(5) For selected recent examples, see: (a) Ferry, A.; Billard, T.;
́
Langlois, B. R.; Bacque, E. Angew. Chem., Int. Ed. 2009, 48, 8551−
8555. (b) Yang, Y.-D.; Azuma, A.; Tokunaga, E.; Yamasaki, M.; Shiro,
M.; Shibata, N. J. Am. Chem. Soc. 2013, 135, 8782−8785. (c) Liu, J.-
B.; Chu, L.-L.; Qing, F.-L. Org. Lett. 2013, 15, 894−897. (d) Xu, C.-
F.; Ma, B.-Q.; Shen, Q.-L. Angew. Chem., Int. Ed. 2014, 53, 9316−
9320. (e) Wu, H.; Xiao, Z.; Wu, J.; Guo, Y.; Xiao, J.-C.; Liu, C.; Chen,
Q.-Y. Angew. Chem., Int. Ed. 2015, 54, 4070−4074. (f) Xu, C.-F.;
Shen, Q.-L. Org. Lett. 2015, 17, 4561−4563. (g) Liu, X.; An, R.;
Zhang, X.; Luo, J.; Zhao, X.-D. Angew. Chem., Int. Ed. 2016, 55,
5846−5850. (h) Yang, X.-G.; Zheng, K.; Zhang, C. Org. Lett. 2020,
22, 2026−2031.
(6) For selected examples, see: (a) Mahadevan, A.; Fuchs, P. L. J.
Am. Chem. Soc. 1995, 117, 3272−3273. (b) Chu, X.-Q.; Meng, H.;
Xu, X.-P.; Ji, S.-J. Chem. - Eur. J. 2015, 21, 11359−11368. (c) Urkalan,
K. B.; Sigman, M. S. Angew. Chem., Int. Ed. 2009, 48, 3146−3149.
(d) Werner, E. W.; Urkalan, K. B.; Sigman, M. S. Org. Lett. 2010, 12,
2848−2851. (e) Yamamoto, E.; Hilton, M. J.; Orlandi, M.; Saini, V.;
Toste, F. D.; Sigman, M. S. J. Am. Chem. Soc. 2016, 138, 15877−
15880.
(7) (a) Braverman, S.; Pechenick, T.; Zafrani, Y. ARKIVOC 2004,
No. ii, 51−63. (b) Maeno, M.; Shibata, N.; Cahard, D. Org. Lett.
E
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