Transition-Metal-Free Cross-Coupling of Aryl and Heteroaryl Thiols with Arylzinc Reagents

Article abstract of DOI:10.1021/acs.orglett.7b03145

Cross-coupling of (hetero)arylthiols with arylzinc reagents via C-S cleavage was performed under transition-metal-free conditions. The reaction displays a wide scope of substrates and high functional-group tolerance. Electron-rich and -deficient (hetero)arylthiols and arylzinc reagents can be employed in this transformation. Mg²⁺ and Li⁺ ions were demonstrated to facilitate the reaction.

Full text of DOI:10.1021/acs.orglett.7b03145

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX-XXX
Transition-Metal-Free Cross-Coupling of Aryl and Heteroaryl Thiols
with Arylzinc Reagents
Bo Yang† and Zhong-Xia Wang*,†,‡
†CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at Microscale and Department of
Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
‡Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, P. R. China
S
* Supporting Information
ABSTRACT: Cross-coupling of (hetero)arylthiols with arylzinc
reagents via C−S cleavage was performed under transition-metal-
free conditions. The reaction displays a wide scope of substrates and
high functional-group tolerance. Electron-rich and -deficient
(hetero)arylthiols and arylzinc reagents can be employed in this transformation. Mg2+ and Li+ ions were demonstrated to
facilitate the reaction.
ulfur-containing organic molecules exist widely in natural
equiv of MeZnCl, the following reaction with 1.6 equiv of p-
Sproducts, pesticides, and proteins. The study on function- Me2NC6H4ZnCl gave 3a in 93% yield (Table S1 in the SI, entry
6). Reducing 2a loading or lowering reaction temperature led to a
decrease in yield (Table S1 in the SI, entries 7−10). Other
solvents were also tested. The reaction in THF, toluene/iPr2O
(3:1) or toluene/nBu2O (3:1) gave 85%, 90%, and 88% product
yields, respectively. No reaction occurred when DMF or DMSO
was employed as a solvent (Table S1 in the SI, entries 11−15).
Finally, it was demonstrated that the reaction completed
quantitatively when the reaction time was prolonged to 24 h
(Table S1 in the SI, entry 16).
alization of the C−S bond is of significance in modifying the
sulfur-containing molecules and developing synthetic method-
ology based on organosulfur compounds. Transition-metal-
catalyzed C−S bond activation is a main method to achieve the
goal.1−5 However, the sulfur atom can be strongly bound to
transition metals, which poison the catalysts and lead to
deactivation.6 Hence, developing highly effective catalytic
systems or searching for alternative methods is an important
research topic. On the other hand, transition-metal-free reactions
of unreactive substrates are receiving considerable attention
because they are less costly and more environmentally friendly in
comparison with transition-metal-catalyzed ones and can avoid
any transition metal impurities in pharmaceutical products.7
Some examples of transition-metal-free cross-couplings have
been reported. Nucleophiles used in the transformation included
Grignard reagents,8 organozinc reagents,9 organoboron re-
agents,10 and organoaluminum reagents.11 Electrophiles were
mainly organic halides.8−11 Allylic alcohols and aryl cyanides
were also employed as electrophilic partners.9e,10a In view of the
above results and the importance of C−S bond activation, we
initiated a study on transition-metal-free cross-coupling of
arylthiols with arylzinc reagents.
The reaction of benzenethiol (1a) with p-Me2NC6H4ZnCl
(2a) was employed to optimize reaction conditions. Because of
the presence of the acidic proton in benzenethiol, excess
organozinc reagent was used or a strong base was added to
convert benzenethiol to its salt prior to performing the coupling
reaction. When benzenethiol was treated with 2.8 equiv of p-
Me2NC6H4ZnCl in toluene at 120 °C (bath temperature) for 12
h, the expected product, N,N-dimethyl[1,1′-biphenyl]-4-amine
(3a), was obtained in 93% yield (Table S1 in the SI, entry 1).
Benzenethiol was treated with 1.2 equiv of MeMgCl, LiMe, or
NaH or 0.6 equiv of Me2Zn at first and then reacted with 1.6
equiv of p-Me2NC6H4ZnCl to afford 3a in lower yields (Table S1
in the SI, entries 2−5). When benzenethiol was treated with 1.2
It has been reported that Mg2+ and Li+ ions often play
important roles in the Negishi cross-coupling reaction.12 In the
current study, we also examined Mg2+ and Li+ ion effects. In the
process of optimizing the reaction conditions p-Me2NC6H4ZnCl
was prepared by reaction of p-Me2NC6H4MgBr with an
equimolar amount of ZnCl2 in the presence of 2 equiv of LiCl.
In the absence of a LiCl additive, the reaction gave 43% product
yield (Table S2 in the SI, entry 1). LiCl additive (1 equiv) led to
88% product yield (Table S2 in the SI, entry 2), being a little
lower than that using 2 equiv of LiCl. LiCl additive (3 equiv) did
not further improve the yield compared with that using 2 equiv of
LiCl additive (Table S2 in the SI, entry 3). In the absence of Mg2+
ion, the reaction of p-Me2NC6H4ZnCl (prepared from p-
Me2NC6H4Li and ZnCl2) with benzenethiol resulted in 3a in
60% yield (Table S2 in the SI, entry 4). p-Me2NC6H4ZnCl
prepared from the reaction of p-Me2NC6H4Li and ZnCl2 in the
presence of MgCl2 showed the same reactivity as those prepared
from p-Me2NC6H4MgBr and ZnCl2 in the presence of LiCl
(Table S2 in the SI, entries 5 and 6). In this reaction, Mg2+ and
Li+ ions may play multiple roles. On the one hand, action of
ArZnX with MgX2 can form ionic zincates which have higher
reactivity than ArZnX.9b,13 The existence of LiX increases the
solubility of the zinc reagents by forming a trimetallic adduct and
Received: October 10, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.7b03145
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
produces reactive zincates.14 The higher reactivity of the zincates
was also supported by the 13C NMR spectral study of p-
MeC6H4ZnCl with various proportions of LiCl and MgCl2 (see
the SI).15 On the other hand, coordination of the sulfur atom of
benzenethiolate salt to the Mg2+ and Li+ ions activates the C−S
bond. Combination of the sulfur anion with the metal ions also
increases its leaving propensity.
ICP-MS analysis of the reaction mixture (Table S1 in the SI,
entry 16) showed the existence of transition-metal impurities
(Mn, 28.0 ppm; Fe, 19.0 ppm; Co, 1.9 ppm; Ni, 5.2 ppm; Cu, 2.7
ppm; Ru, Rh, and Pd < 0.05 ppm). To rule out the possibility of
transition-metal catalysis, we carried out the reaction using highly
pure Mg (99.99%, Aladdin Industrial Corp.), ZnCl2 (99.999%,
Alfa Aesar), and LiCl (99.995%, Alfa Aesar) under the same
conditions as shown in entry 16, Table S1 in the SI. The coupling
product 3a was obtained in 99% yield. ICP-MS analysis of the
reaction mixture derived from the highly pure reagents showed
that no transition-metal impurities were detected at the level of 1
ppb (the detection limit).
zinc reagent can increase product yield to some extent (77%).
Both naphthalene-1-thiol and naphthalene-2-thiol were also
highly reactive. They showed similar reactivity to benzenethiol
and led to excellent coupling yields (3e, 3f). A series of
benzenethiols with electron-withdrawing groups on the phenyl
rings including p-F, p-Cl, p-Br, m-CF3, p-CF3, p-CN, p-COPh, p-
CO2Et, and p-CONEt2 groups were also demonstrated to react
with 2a under standard conditions, giving the corresponding
coupling products (3g−o) in 30−91% yields. Among the
halogen-substituted benzenethiols, 4-fluorobenzenethiol re-
sulted in excellent coupling yield (85%), while 4-bromobenze-
nethiol gave relatively low coupling yield (36%). The low yield of
the latter was due to the existence of side reactions. 1,4-(p-
Me2NC6H4)2C6H4 as a main byproduct was detected by GC−
MS in the reaction of 4-bromobenzenethiol with 2a. It was
reported that the transition-metal-free reaction of arylzinc
reagents with aryl iodides was a radical process.9a In our reaction
of 4-bromobenzenethiol, both the radical process and transition-
metal-catalyzed process were ruled out by adding a radical trap (2
equiv of 1,1-diphenylethene) and employing highly pure metal
reagents (see the SI), respectively. Reaction of 3-
(trifluoromethyl)benzenethiol with 2a afforded the desired
product 3j in excellent yield (91%). Reaction of p-CF3C6H4SH
under the same conditions gave markedly lower product yield
(3k, 57%), and unidentified byproducts were observed from
TLC. Reaction of p-NCC6H4SH and p-PhC(O)C6H4SH with 2a
resulted in the desired products (3l, 3m) in relatively low yields
and unidentified byproducts. Respective reaction of p-
EtO2CC6H4SH and p-Et2NC(O)C6H4SH with 2a under stand-
ard conditions gave desired product (3n, 3o) in moderate yield.
Higher 2a loading (up to 2.5 equiv) increased the product yield.
Coordination of the CN or carbonyl group to Zn2+, Mg2+, or Li+
ions in these compounds may affect the reactivity of the thiolates
or arylzinc reagents. Heteroarylthiols including benzo[d]-
oxazole-2-thiol, benzo[d]thiazole-2-thiol, pyridine-2-thiol, 4,6-
dimethylpyrimidine-2-thiol, and 1-phenyl-1H-tetrazole-5-thiol
were also demonstrated to be suitable substrates in this
transformation. Reaction of benzo[d]thiazole-2-thiol required
higher 2a loading to achieve optimal product yield (3q).
Reaction of the other heteroarylthiols proceeded smoothly under
the standard conditions and gave good to excellent product
yields (3p and 3r−t).
Next, we examined substrate scope of the reaction under the
optimized conditions. Reaction of various (hetero)arylthiols with
p-Me2NC6H4ZnCl (2a) was first tested. Thus, (hetero)arylthiols
were treated with MeZnCl at room temperature for 30 min, and
then the resultant thioates were reacted with p-Me2NC6H4ZnCl
in toluene at 120 °C for 24 h. As shown in Scheme 1, a broad
Scheme 1. Cross-Coupling of (Hetero)arylthiols with p-
a
Me2NC6H4ZnCl
The scope of nucleophilic substrates was examined by the
reaction with 4,6-dimethylpyrimidine-2-thiol (Scheme 2). We
noticed that in the reaction with 4,6-dimethylpyrimidine-2-thiol
1.8 equiv of arylzinc reagent was necessary to achieve optimal
yields. Reaction of both p-MeC6H4ZnCl and o-MeC6H4ZnCl
gave the desired products in excellent yields. However, reaction
of 2,4,6-Me3C6H2ZnCl gave only 23% product yield (4c). This is
ascribed to the steric hindrance of 2,4,6-Me3C6H2ZnCl.
Increasing the zinc reagent loading to 2 equiv and prolonging
the reaction time to 48 h resulted in 38% product yield. Other
electron-rich arylzinc reagents including (4-methoxyphenyl)zinc
chloride, benzo[d][1,3]dioxol-5-ylzinc chloride, and (4-
(methylthio)phenyl)zinc chloride showed good reactivity, and
they led to desired products in good to excellent yields (4d−f).
Naphthalen-1-ylzinc chloride exhibited lower reactivity than
naphthalen-2-ylzinc chloride, probably due to the larger steric
hindrance of the former. Increasing the naphthalen-1-ylzinc
chloride loading can improve the product yield. Reaction of
electron-poor arylzinc reagents such as p-CF3C6HZnCl and p-
FC6H4ZnCl also gave excellent product yields (4i, 4j). This may
result from high reactivity of 4,6-dimethylpyrimidine-2-thiol.
a
The reactions were carried out using 0.5 mmol (hetero)arylthiols and
1.6 equiv of 2a according to the conditions indicated by the above
equation. p-Me2NC6H4ZnCl and MeZnCl were prepared from the
corresponding Grignard reagents and ZnCl2 in the presence of 2 equiv
of LiCl. 2.0 equiv of 2a was used. Bath temperature was 140 °C. 1.8
equiv of 2a was used. 2.5 equiv of 2a was used.
b
c
d
e
range of (hetero)arylthiols was demonstrated to be suitable for
the coupling. Both 2-methylbenzenethiol and 4-methylbenzene-
thiol exhibited reactivity similar to that of benzenethiol. Their
reaction with 2a formed the corresponding coupling products
(3b, 3c) in almost quantitative yields. The steric hindrance of o-
methyl group in 2-methylbenzenethiol did not affect the reaction
result. 4-Methoxybenzenethiol showed lower reaction activity
than benzenethiol. Its reaction with 2a gave 3d in 67% yield.
Enhancing reaction temperature and increasing loading of the
B
DOI: 10.1021/acs.orglett.7b03145
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Letter
excellent yields (5a, 5b), while reaction of electron-poor arylzinc
reagents, p-FC6H4ZnCl and p-CF3C6H4ZnCl, with benzenethiol,
4-methylbenzenethiol, or 4-methoxybenzenethiol generated
corresponding products in markedly lower yields (5c−h). This
is ascribed to weak nucleophilicity of the electron-poor arylzinc
reagents. Finally, reaction of naphthalene-2-thiol with thiophene-
2-ylzinc chloride was carried out, affording 2-(naphthalen-2-
yl)thiophene in 79% yield.
Scheme 2. Cross-Coupling of 4,6-Dimethylpyrimidine-2-thiol
with Organozinc Reagents
a
Preliminary experiments to evaluate the plausible reaction
mechanism were carried out. The reaction of PhSH with p-
Me2NC6H4ZnCl was not affected by 1,1-diphenylethene or (1-
cyclopropylvinyl)benzene additive. When 2.0 equiv of 1,1-
diphenylethene or (1-cyclopropylvinyl)benzene was added to
the reaction system, the reaction gave the coupling product in
98% yield in each case. The recovery of 1,1-diphenylethene and
(1-cyclopropylvinyl)benzene was 98% and 97%, respectively.
Single-electron-donor lithium di-tert-butylbiphenyl (LiDBB)
was reported to lead to a significant increase in the product
yield for reaction of aryl or alkenyl halides with aryl Grignard
reagents or arylzinc reagents.8b,d,9a However, the same effect was
not observed in the reaction of PhSH with p-Me2NC6H4ZnCl or
p-MeOC6H4SH with p-CF3C6H4ZnCl (see the SI). The above
experimental facts exclude a free-radical electron-transfer
mechanism. On the other hand, the reaction of substituted
benzenethiols with arylzinc reagents did not generate
regioisomers, which rules out the aryne pathway.16 Furthermore,
two intermolecular competition experiments were performed.
When p-Me2NC6H4ZnCl and p-CF3C6H4ZnCl in 1:1 molar ratio
reacted with 1 equiv of PhSZnCl, a mixture of p-Me2NC6H4Ph
and p-CF3C6H4Ph was obtained in a ∼2:1 ratio. This result
demonstrated that the reaction was facilitated by a stronger
nucleophilic reagent. When a mixture of p-FC6H4SZnCl and p-
MeOC6H4SZnCl in 1:1 molar ratio was treated with 1.0 equiv of
p-Me2NC6H4ZnCl, 4′-fluoro-N,N-dimethylbiphenyl-4-amine
and 4′-methoxy-N,N-dimethylbiphenyl-4-amine were obtained
in a 1.46:1 ratio. This result showed that an electron-poor
arylthiol was more reactive than an electron-rich one. These
experimental facts support a nucleophilic aromatic substitution
mechanism via an addition−elimination pathway.17 However, a
nucleophilic aromatic substitution mechanism normally requires
the presence of activating groups on the aromatic rings of the
electrophilic substrates.18 In our reaction, unactivated arylthiols
also showed good reactivity. This may result from an interaction
of the metal ions with the π-cloud of aromatic ring which
decreases the electron density of the aromatic ring. The
theoretical calculation results proved the presence of cation−π
interaction between metal cations (Li+, Na+, K+, Be2+, Mg2+, and
Ca2+) and different π-systems such as para-substituted (F, Cl,
OH, SH, CH3, and NH2) benzene derivatives.19 Each 1H NMR
spectrum of PhSLi, PhSMgCl, and PhSZnCl·MgCl2·2LiCl
showed an obvious downfield shift of the aromatic proton
signals compared with those of PhSH (see the SI). The
deshielding effect corresponds to a decrease of the electron
density of the aromatic rings. Meanwhile, the metal ions also
promote the reaction via (1) their complexation with the sulfur
anion, which activates the C−S bond and (2) forms ionic
zincates, which increases the nucleophilicity of the reagent. The
low yields of the reaction of the electron-deficient arylthiols such
as p-NCC6H4SH, p-PhC(O)C6H4SH, p-EtO2CC6H4SH, and p-
Et2NC(O)C6H4SH are ascribed to (1) the existence of side
reactions and (2) the coordination of CN or carbonyl groups to
Zn2+, Mg2+, or Li+ ions, which reduces the amount of the metal
ions used to interact with the sulfur anion or the aromatic ring.
a
The reactions were carried out using 0.5 mmol of 4,6-dimethylpyr-
imidine-2-thiol and 1.8 equiv of (hetero)arylzinc reagents according to
the conditions indicated by the above equation. Unless otherwise
specified, the zinc reagents were prepared from corresponding
Grignard reagents and ZnCl2 in the presence of 2 equiv of LiCl.
b
c
1.6 equiv of zinc reagent was used. 2.0 equiv of zinc reagent was
d
e
used. Reaction time was 48 h. The zinc reagents were prepared from
furan-2-yllithium or thiophene-2-yllithium and 1.0 equiv of ZnCl2 in
the presence of 1.0 equiv of LiCl and 1.0 equiv of MgCl2.
Heteroarylzinc reagents, furan-2-ylzinc chloride, and thiophene-
2-ylzinc chloride also reacted smoothly with 4,6-dimethylpyr-
imidine-2-thiol to form the corresponding biheteroaryls in 87%
and 78% yields, respectively (4k, 4l).
Reaction of benzenethiol and electron-rich arylthiols with
various arylzinc reagents, especially electron-poor arylzinc
reagents, was also tested (Scheme 3). p-MeOC6H4ZnCl and
benzo[d][1,3]dioxol-5-ylzinc chloride were proven to effectively
couple with benzenethiol to afford the desired products in
Scheme 3. Cross-Coupling of Benzenethiol and Electron-Rich
Arylthiols with Organozinc Reagents
a
a
The reactions were carried out using 0.5 mmol of thiol and 1.8 equiv
of zinc reagents according to the conditions indicated by the above
equation. Unless otherwise specified, the zinc reagents were prepared
from Grignard reagents and ZnCl2 in the presence of 2 equiv of LiCl.
b
c
NMR yield. Thiophene-2-ylzinc chloride was prepared from
thiophene-2-yllithium and 1.0 equiv of ZnCl2 in the presence of 1.0
equiv of LiCl and 1.0 equiv of MgCl2.
C
DOI: 10.1021/acs.orglett.7b03145
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
(4) (a) Sugahara, T.; Murakami, K.; Yorimitsu, H.; Osuka, A. Angew.
Chem., Int. Ed. 2014, 53, 9329. (b) Ram, V. J.; Agarwal, N. Tetrahedron
Lett. 2001, 42, 7127.
That higher loading of the zinc reagents resulted in higher
product yields supported this assumption (Scheme 1, 3n and
3o). In addition, the aqueous-phase residue obtained after
extraction of the reaction mixture with organic solvent can react
with HgCl2 to form a black-brown precipitate, which proved
formation of S2− in the reaction.
́
(5) (a) Hooper, J. F.; Chaplin, A. B.; Gonzalez-Rodríguez, C.;
Thompson, A. L.; Weller, A. S.; Willis, M. C. J. Am. Chem. Soc. 2012, 134,
2906. (b) Arambasic, M.; Hooper, J. F.; Willis, M. C. Org. Lett. 2013, 15,
5162.
In summary, we developed a transition-metal-free coupling
reaction of (hetero)arylthiols with arylzinc reagents to form
bi(hetero)aryls. The reaction exhibited wide substrate scope and
good compatibility of functional groups. Electron-rich and -poor
aryl or heteroaryl thiols can be converted. Various arylzinc
reagents, including electron-rich and electron-poor reagents, can
be employed as the coupling partners. Preliminary mechanistic
studies suggest a nucleophilic aromatic substitution pathway, and
Mg2+ and Li+ ions play important roles in the process of reaction.
This study provides an example of S2− as a leaving group in an
aromatic system and an effective methodology for the synthesis
of bi(hetero)aryls including pharmaceutical molecules without
transition-metal impurities.
(6) Murray, S. G.; Hartley, F. R. Chem. Rev. 1981, 81, 365.
(7) (a) Sun, C.-L.; Shi, Z.-J. Chem. Rev. 2014, 114, 9219. (b) Pichette
Drapeau, M.; Fabre, I.; Grimaud, L.; Ciofini, I.; Ollevier, T.; Taillefer, M.
Angew. Chem., Int. Ed. 2015, 54, 10587.
(8) (a) Han, X.-P.; Zhang, Y.-H.; Wu, J. J. Am. Chem. Soc. 2010, 132,
4104. (b) Shirakawa, E.; Hayashi, Y.; Itoh, K.; Watabe, R.; Uchiyama, N.;
Konagaya, W.; Masui, S.; Hayashi, T. Angew. Chem., Int. Ed. 2012, 51,
218. (c) Shirakawa, E.; Watabe, R.; Murakami, T.; Hayashi, T. Chem.
Commun. 2013, 49, 5219. (d) Uchiyama, N.; Shirakawa, E.; Hayashi, T.
Chem. Commun. 2013, 49, 364.
(9) (a) Shirakawa, E.; Tamakuni, F.; Kusano, E.; Uchiyama, N.;
Konagaya, W.; Watabe, R.; Hayashi, T. Angew. Chem., Int. Ed. 2014, 53,
521. (b) Dunsford, J. J.; Clark, E. R.; Ingleson, M. J. Angew. Chem., Int.
Ed. 2015, 54, 5688. (c) Ellwart, M.; Makarov, I. S.; Achrainer, F.; Zipse,
H.; Knochel, P. Angew. Chem., Int. Ed. 2016, 55, 10502. (d) Minami, H.;
Wang, X.; Wang, C.; Uchiyama, M. Eur. J. Org. Chem. 2013, 7891.
(e) Quinio, P.; Roman, D. S.; Leon, T.; William, S.; Karaghiosoff, K.;
Knochel, P. Org. Lett. 2015, 17, 4396.
ASSOCIATED CONTENT
■
S
* Supporting Information
(10) (a) Kabalka, G. W.; Yao, M.-L.; Borella, S.; Wu, Z. Chem.
Commun. 2005, 2492. (b) Scrivanti, A.; Beghetto, V.; Bertoldini, M.;
Matteoli, U. Eur. J. Org. Chem. 2012, 264.
(11) Minami, H.; Saito, T.; Wang, C.; Uchiyama, M. Angew. Chem., Int.
Ed. 2015, 54, 4665.
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.orglett.7b03145.
Experimental procedures, spectral data, and NMR spectra
(PDF)
(12) (a) Wu, D.; Tao, J.-L.; Wang, Z.-X. Org. Chem. Front. 2015, 2, 265.
(b) Yang, X.; Wang, Z.-X. Organometallics 2014, 33, 5863. (c) Zhu, F.;
Wang, Z.-X. J. Org. Chem. 2014, 79, 4285. (d) Ohashi, M.; Doi, R.;
Ogoshi, S. Chem. - Eur. J. 2014, 20, 2040. (e) Polet, D.; Rathgeb, X.;
Falciola, C. A.; Langlois, J.-B.; El Hajjaji, S.; Alexakis, A. Chem. - Eur. J.
2009, 15, 1205. (f) Otsuka, S.; Fujino, D.; Murakami, K.; Yorimitsu, H.;
Osuka, A. Chem. - Eur. J. 2014, 20, 13146.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: zxwang@ustc.edu.cn.
ORCID
́
(13) (a) Hevia, E.; Chua, J. Z.; García-Alvarez, P.; Kennedy, A. R.;
Zhong-Xia Wang: 0000-0001-8126-8778
Notes
McCall, M. D. Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 5294. (b) Jin, L.;
Liu, C.; Liu, J.; Hu, F.; Lan, Y.; Batsanov, A. S.; Howard, J. A. K.; Marder,
T. B.; Lei, A. J. Am. Chem. Soc. 2009, 131, 16656.
The authors declare no competing financial interest.
́
(14) (a) Armstrong, D. R.; Clegg, W.; García-Alvarez, P.; Kennedy, A.
R.; McCall, M. D.; Russo, L.; Hevia, E. Chem. - Eur. J. 2011, 17, 8333.
(b) Hatano, M.; Ito, O.; Suzuki, S.; Ishihara, K. J. Org. Chem. 2010, 75,
5008. (c) McCann, L. C.; Organ, M. G. Angew. Chem., Int. Ed. 2014, 53,
4386.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (Grant No. 21172208) and the National
Basic Research Program of China (Grant No. 2015CB856600).
́ ́
(15) (a) Hernan-Gomez, A.; Herd, E.; Uzelac, M.; Cadenbach, T.;
Kennedy, A. R.; Borilovic, I.; Aromí, G.; Hevia, E. Organometallics 2015,
34, 2614. (b) Procter, R. J.; Dunsford, J. J.; Rushworth, P. J.; Hulcoop, D.
G.; Layfield, R. A.; Ingleson, M. J. Chem. - Eur. J. 2017, DOI: 10.1002/
chem.201704170.
REFERENCES
■
(1) (a) Dubbaka, S. R.; Vogel, P. Angew. Chem., Int. Ed. 2005, 44, 7674.
(16) Hassan, J.; Sev
Rev. 2002, 102, 1359.
́
ignon, M.; Gozzi, C.; Schulz, E.; Lemaire, M. Chem.
(b) Prokopcova,
́
H.; Kappe, C. O. Angew. Chem., Int. Ed. 2009, 48, 2276.
(c) Wang, L.-D.; He, W.; Yu, Z.-K. Chem. Soc. Rev. 2013, 42, 599.
(d) Pan, F.; Shi, Z.-J. ACS Catal. 2014, 4, 280. (e) Modha, S. G.; Mehta,
V. P.; van der Eycken, E. V. Chem. Soc. Rev. 2013, 42, 5042.
(2) (a) Okamura, H.; Miura, M.; Takei, H. Tetrahedron Lett. 1979, 20,
43. (b) Takei, H.; Miura, M.; Sugimura, H.; Okamura, H. Chem. Lett.
1979, 8, 1447. (c) Wenkert, E.; Ferreira, T. W.; Michelotti, E. L. J. Chem.
Soc., Chem. Commun. 1979, 637.
(17) (a) Bunnett, J. F.; Zahler, R. E. Chem. Rev. 1951, 49, 273.
(b) Buncel, E.; Dust, J. M.; Terrier, F. Chem. Rev. 1995, 95, 2261.
(18) Smith, M. B. March’s Advanced Organic Chemistry: Reactions,
Mechanisms, and Structure, 7th ed.; John Wiley & Sons: Hoboken, 2013;
pp 373−379.
(19) Khanmohammadi, A.; Raissi, H.; Mollania, F.; Hokmabadi, L.
Struct. Chem. 2014, 25, 1327.
(3) (a) Ookubo, Y.; Wakamiya, A.; Yorimitsu, H.; Osuka, A. Chem. -
Eur. J. 2012, 18, 12690. (b) Otsuka, S.; Fujino, D.; Murakami, K.;
Yorimitsu, H.; Osuka, A. Chem. - Eur. J. 2014, 20, 13146. (c) Pan, F.;
Wang, H.; Shen, P.-X.; Zhao, J.; Shi, Z.-J. Chem. Sci. 2013, 4, 1573.
(d) Liu, J.-X.; Liu, Y.-J.; Du, W.-T.; Dong, Y.; Liu, J.; Wang, M. J. Org.
Chem. 2013, 78, 7293. (e) Eberhart, A. J.; Imbriglio, J. E.; Procter, D. J.
Org. Lett. 2011, 13, 5882. (f) Quan, Z.-J.; Lv, Y.; Jing, F.-Q.; Jia, X.-D.;
Huo, C.-D.; Wang, X.-C. Adv. Synth. Catal. 2014, 356, 325. (g) Hooper,
J. F.; Young, R. D.; Pernik, I.; Weller, A. S.; Willis, M. C. Chem. Sci. 2013,
4, 1568.
D
DOI: 10.1021/acs.orglett.7b03145
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