Weak, bidentate chelating group assisted cross-coupling of C(sp3)-H bonds in aliphatic acid derivatives with aryltrifluoroborates

Article abstract of DOI:10.1039/c8cc07481j

A protocol of Pd(ii)-catalyzed, weak bidentate directing group assisted β-C(sp³)-H activation/cross-coupling with organoboron reagents has been achieved, affording arylation of aliphatic acid derivatives that contain α-hydrogen atoms in moderate to good yields. The potential of this method for an asymmetric β-C(sp³)-H arylation via desymmetrization was also presented.

Full text of DOI:10.1039/c8cc07481j

ChemComm
View Article Online
View Journal | View Issue
COMMUNICATION
Weak, bidentate chelating group assisted
cross-coupling of C(sp3)–H bonds in aliphatic
acid derivatives with aryltrifluoroborates†
Cite this: Chem. Commun., 2018,
54, 12766
Received 14th September 2018,
Accepted 19th October 2018
ab
Zhihua Cai,ab Shangda Li,a Yuzhen Gao,a Lei Fua and Gang Li
*
DOI: 10.1039/c8cc07481j
rsc.li/chemcomm
A protocol of Pd(II)-catalyzed, weak bidentate directing group
assisted b-C(sp3)–H activation/cross-coupling with organoboron
reagents has been achieved, affording arylation of aliphatic acid
derivatives that contain a-hydrogen atoms in moderate to good
yields. The potential of this method for an asymmetric b-C(sp3)–H
arylation via desymmetrization was also presented.
In the past two decades, despite a range of success in transition-
metal-catalyzed C(sp2)–H bond functionalizations with organo-
metallic reagents,1–3 considerable limitations still exist in this type
of reaction at C(sp3)–H bonds.2d,f,4–7 In the arylation and alkylation
of b-C(sp3)–H bonds of aliphatic acids or their derivatives with
organometallic reagents such as organoboron, organosilicon and
organozinc reagents, the substrates are mostly restricted to those
without a-hydrogen atoms, i.e. those possessing quaternary
Scheme 1 Pd(II)-Catalyzed C(sp3)–H cross-coupling of aliphatic acid
derivatives containing a-H atoms with organometallic reagents.
centers at the a-position.2f,4,5 The only exception is the protocol homocoupling of the organometallic reagents can outpace the
of Pd(II)-catalyzed cross-coupling of C(sp3)–H bonds in aliphatic C–H cleavage step.
amides containing a-hydrogen atoms by using arylsilanes as the
To overcome the challenging substrate scope limitation and
coupling partners via a Pd(II)/Pd(0) catalytic cycle (Scheme 1a).6 To encouraged by the pioneering works on Pd(II)-catalyzed cross-
date, no report has been disclosed on transition-metal-catalyzed coupling of C(sp3)–H bonds in aliphatic acids or their derivatives
cross-coupling of b-C(sp3)–H bonds in aliphatic acids or their with organoboron reagents,2f,4 we envisioned to develop a weak,
derivatives that contain a-hydrogen atoms with other organo- bidentate directing group, which might be capable of increasing
metallic reagents such as organoboron reagents.1c–e,8 The funda- the rate of C–H cleavage of aliphatic acid derivatives without the
mental explanation of this incompatibility can be that the Thorpe–Ingold effect and facilitating the transmetallation in the
resulting metallacycle (e.g. palladacycle) after the C–H activation catalytic cycle due to its weak coordination (Scheme 1b).9 Herein
can undergo b-hydride elimination with the a-hydrogen atom, we report a cross-coupling of C(sp3)–H bonds in aliphatic acid
which out-competes the desired transmetallation step.1a Another derivatives bearing a-hydrogen atoms with aryltrifluoroborates
reason might be that the rate of C–H cleavage of the substrates through a Pd(II)/Pd(0) catalytic cycle. Importantly, this method
containing a-hydrogen atoms is slower than those without also holds the potential to produce enantioenriched aliphatic
a-hydrogen atoms due to a favourable Thorpe–Ingold effect in acid derivatives.10
the latter substrates. And due to the slower rate, metal-mediated
To start our study on developing a suitable weak and bidentate
directing group,9 we engineered amide 1a from isobutyric acid and
examined its reaction with potassium 4-methylphenyltrifluoroborate
2a (Table 1). After extensive reaction condition screening,
the reaction was found to proceed to afford the mono- and
di-arylated products in 31% combined yield in the presence of
10 mol% of Pd(OAc)2, 20 mol% of N-Ac-Ile-OH, 2.0 equivalents
of Ag2CO3, 10 mol% of 1,4-benzoquinone and 1.5 equivalents of
a State Key Laboratory of Structural Chemistry, Center for Excellence in Molecular
Synthesis, Fujian Institute of Research on the Structure of Matter, Fuzhou,
Fujian 350002, China. E-mail: gangli@fjirsm.ac.cn
b University of Chinese Academy of Science, Beijing, 100049, China
† Electronic supplementary information (ESI) available: Experimental procedures
and data for new compounds. See DOI: 10.1039/c8cc07481j
12766 | Chem. Commun., 2018, 54, 12766--12769
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Communication
ChemComm
Table 1 Directing group optimizationa
Table 2 Optimization of reaction conditionsa
Entry
Ligand
Base (equiv.)
Additive
Yield (%) (3amono/3adi)b
1
L1
L1
L1
L1
L1
L1
—
L1
L1
L1
L1
L1
L2
L3
L4
L5
L6
L7
L8
L8
Cs2CO3 (0.5)
Cs2CO3 (0.5)
Cs2CO3 (0.5)
Cs2CO3 (0.5)
Cs2CO3 (0.5)
Cs2CO3 (0.5)
Cs2CO3 (0.5)
Cs2CO3 (0.5)
Cs2CO3 (0.5)
Cs2CO3 (0.5)
K2CO3 (0.5)
K2CO3 (2.0)
K2CO3 (2.0)
K2CO3 (2.0)
K2CO3 (2.0)
K2CO3 (2.0)
K2CO3 (2.0)
K2CO3 (2.0)
K2CO3 (2.0)
K2CO3 (2.0)
BQ-1
BQ-1
BQ-1
BQ-2
BQ-3
—
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
BQ-1
48 (3.8 : 1)
49 (3.5 : 1)
47 (4.2 : 1)
43 (5.1 : 1)
4 (1 : 0)
5 (1 : 0)
4 (1 : 0)
54 (3.5 : 1)
51 (4.1 : 1)
35 (6 : 1)
44 (4.5 : 1)
58 (2.6 : 1)
39 (3.9 : 1)
59 (2.5 : 1)
55 (2.7 : 1)
42 (4.2 : 1)
52 (3.3 : 1)
54 (2.8 : 1)
61 (2.2 : 1)
65 (2.1 : 1)
2c
3c,d
4
5
6
7
8e
9 f
10g
11e
12e
13e
14e
15e
16e
17e
18e
19e
20c,e,h
a
Reaction conditions: 1 (0.1 mmol), 2a (0.2 mmol), Pd(OAc)2 (0.01 mmol),
N-Ac-Ile-OH (0.02 mmol), Ag2CO3 (0.2 mmol), Cs2CO3 (0.15 mmol), 1,4-BQ
(0.01 mmol), t-AmylOH (1 mL, 0.1 M), 12 h, 100 1C. The yield was
1
b
determined by H NMR using CH2Br2 as the internal standard. 120 1C.
c
d
Cs2CO3 (0.5 equiv.), t-AmylOH (0.2 M). Mono’ was the product of
arylation of ortho-C(sp2)–H bond. 1,4-BQ: 1,4-benzoquinone.
a
Reaction conditions: 1a (0.1 mmol), 2a (0.2 mmol), Pd(OAc)2
Cs2CO3 in t-AmylOH at 100 1C for 12 h. Notably, the directing
group in 1b without a fluoro-substituent also led to comparable (0.01 mmol), t-AmylOH (1 mL, 0.1 M), 12 h, 100 1C. The yield was
yields of products, and no arylation was detected on the
aromatic ring of 1b. This result implied that the ortho-fluoro
group of 1a might weaken the coordinating ability of the directing
group by reducing the electronic density of the coordinating
atoms, rather than acting as a blocking group to avoid arylation
of the aromatic ring. Subsequently, extensive fine tuning of the
(0.01 mmol), ligand (0.02 mmol), Ag2CO3 (0.2 mmol), base, additive
b
c
determined by 1H NMR using CH2Br2 as the internal standard. 24 h.
d
After 12 h, a second batch of 2a (0.2 mmol) and Ag2CO3 (0.2 mmol)
e
was added, and the reaction was continued for another 12 h. 0.2 M.
f
g
h
0.4 M. 0.05 M. 28% of 1a was recovered. BQ-1 = 1,4-benzoquinone
(1,4-BQ); BQ-2 = 2-methylcyclohexa-2,5-diene-1,4-dione; BQ-3 = 2,3,5,6-
tetramethylcyclohexa-2,5-diene-1,4-dione.
directing groups (1c–1h) was carried out in order to examine in batches had no positive effect (entry 3). Other benzoquinone
the influence of electronic properties and steric hindrance derivatives were also examined but led to no better results
on the reactivity of the substrates (see also the ESI† for the (entries 4 and 5). It was also proved both the 1,4-BQ and the
evaluation of more substrates, including hydroxamic acids and ligand were essential for the reaction (entries 6 and 7). The
Weinreb amide). Ultimately, substrate 1a proved to be the best concentration of the reaction was also important (entries 8–10).
one with the highest reactivity. Directing groups with even And a higher reaction concentration (0.2 M) could further
weaker bidentate coordination (1i and 1j) were then tested, increase the yield to 54%. Other bases such as K2CO3 were also
leading to no or lower yield of the desired products, evaluated and the best choice was 2.0 equivalents of K2CO3
which implied that bidentate coordination was important in (entries 11 and 12). Other ligands, including N-mono protected
promoting the reaction. It should be noted that the yield was amino acid (L2–L5) ligands and acetyl-protected aminomethyl
also increased with substrate 1a using 0.5 equivalent of Cs2CO3. oxazoline (L6–L8) ligands, were also investigated,7i,10a,e and L8 was
Finally, arylation of the C(sp2)–H bond on the aromatic ring of found to be the optimal ligand for this reaction (entries 13–19).
the directing group occurred if the directing group was mono- Finally, the best combined yield was achieved with L8 in 24 hours,
dentate (1k), which further proved the existence of bidentate together with the recovery of 28% of 1a (entry 20). Extensive efforts
coordination in the directing group of 1a.
were also made to fully convert the substrate to the desired
With the model substrate 1a in hand, extensive reaction products, but all of these efforts, including extending the reaction
condition optimization was conducted to obtain the optimal time, failed (see the ESI† for more screening tests).
result (Table 2). Firstly, the yield increased to 48% when
With the optimal reaction conditions in hand, a series
reducing the loading of Cs2CO3 to 0.5 equivalent (entry 1). Only of potassium aryltrifluoroborates were used in the reaction
a slight increase in the yield was obtained when extending the (Table 3). Methyl and other alkyl substituents on the phenyl
reaction time to 24 hours (entry 2). More 2a and Ag2CO3 added ring of the organoboron reagents were well tolerated to afford
This journal is ©The Royal Society of Chemistry 2018
Chem. Commun., 2018, 54, 12766--12769 | 12767

View Article Online
ChemComm
Communication
the desired products (3a–3g). Subsequently, simple phenyltri-
fluoroborate (3h) and several electron-rich (3i–3k) as well
as electron-poor (3l and 3m) aryltrifluoroborates were also
compatible with this method to afford moderate yields of
the desired products. Other aliphatic acid amides were then
evaluated with reagent 2a under the standard conditions.
Notably, the reaction with a simple propionamide could still
afford the desired product (3n) in a shorter reaction time, albeit
in a modest yield. Amides with an ethyl or n-propyl group at the
a-position were also capable of producing the desired arylated
products (3o and 3p). However, much to our surprise, only
very low yield was obtained with the amide prepared from
pivalic acid, which contains no a-hydrogen atom. It is worth
mentioning that the amide derived from L-(+)-lactic acid was
also compatible with this protocol utilizing ligand L3 to generate
the desired product 3q, albeit in a lower yield. The process
could also be successfully extended to amides containing a
benzyl or trifluoroethyl group at the a-position (3r and 3s). It
should be noted that efforts to convert the unreacted substrates
to the desired products were not successful. However, most of
the unreacted substrates could be recovered, although minor
decomposition of these substrates also occurred. Finally, the
directing group could be readily removed to afford 2-methyl-3-
phenylpropanoic acid 4 in 87% yield, and the auxiliary 5 was
Scheme 2 Removal of the directing auxiliary.
recycled in 86% yield via treatment with 3hmono in 40%
aqueous HBr solution at 80 1C for 24 h (Scheme 2). Products
with functional groups could also be hydrolyzed under the
above conditions (3imono, 3lmono, and 3mmono), although the
methoxyl group was converted into a hydroxyl group under
the acidic conditions (3imono).
Since substrate 1a possesses a prochiral center, we were parti-
cularly interested in obtaining a hint of developing an asymmetric
b-C(sp3)–H arylation via desymmetrization (Scheme 3).10
With the chiral ligand L8 that had been used for asymmetric
b-C(sp3)–H arylation with aryl iodide,10e we were pleased to find
a promising enantiomeric ratio (er) of 73 : 27. This important
observation paved the way for our subsequent investigation
into this desymmetrization reaction.
A plausible catalytic cycle was proposed for this b-C(sp3)–H
arylation (Scheme 4). Initially, intermediate A is generated
from 1a via C(sp3)–H bond activation assisted by the bidentate
auxiliary with one of the coordination sites being the lone
electron pair of the oxygen atom of the N,N-dimethylbenz-
amide group. Subsequently, transmetallation of the aryltrifluoro-
borate reagents with intermediate A gives intermediate B which
undergoes reductive elimination to release the cross-coupling
product and Pd(0). The Pd(0) species is re-oxidized to regenerate
the active Pd(II) species to re-enter the catalytic cycle.
Table 3 Scope of the cross-coupling of C(sp3)–H bonds of aliphatic acids
with aryltrifluoroboratesa
In summary, we developed a Pd(II)-catalyzed cross-coupling
of C(sp3)–H bonds in aliphatic acid derivatives that contain
Scheme 3 Asymmetric b-C(sp3)–H arylation via desymmetrization.
a
Reaction conditions:
1 (0.1 mmol), 2 (0.2 mmol), Pd(OAc)2
(0.01 mmol), L8 (0.02 mmol), Ag2CO3 (0.2 mmol), K2CO3 (0.2 mmol),
BQ-1 (0.01 mmol), t-AmylOH (0.5 mL), 24 h, 100 1C; isolated yield.
12 h. L3 was used instead of L8.
b
c
Scheme 4 Tentative catalytic cycle.
12768 | Chem. Commun., 2018, 54, 12766--12769
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Communication
ChemComm
(g) J. Hubrich, T. Himmler, L. Rodefeld and L. Ackermann, Adv.
Synth. Catal., 2015, 357, 474; (h) H. Wang, S. Yu, Z. Qi and X. Li, Org.
Lett., 2015, 17, 2812; (i) S. Zhao, B. Liu, B.-B. Zhan, W.-D. Zhang and
B.-F. Shi, Org. Lett., 2016, 18, 4586; ( j) B. Liu, Z.-Z. Zhang, X. Li and
B.-F. Shi, Org. Chem. Front., 2016, 3, 897; (k) H.-W. Wang, P.-P. Cui,
Y. Lu, W.-Y. Sun and J.-Q. Yu, J. Org. Chem., 2016, 81, 3416;
(l) X. Zhu, J.-H. Su, C. Du, Z.-L. Wang, C.-J. Ren, J.-L. Niu and
M.-P. Song, Org. Lett., 2017, 19, 596.
4 (a) D.-H. Wang, M. Wasa, R. Giri and J.-Q. Yu, J. Am. Chem. Soc.,
2008, 130, 7190; (b) M. Wasa, K. M. Engle, D. W. Lin, E. J. Yoo and
J.-Q. Yu, J. Am. Chem. Soc., 2011, 133, 19598; (c) K.-J. Xiao, D. W. Lin,
M. Miura, R.-Y. Zhu, W. Gong, M. Wasa and J.-Q. Yu, J. Am. Chem.
Soc., 2014, 136, 8138.
5 (a) R. Shang, L. Ilies, A. Matsumoto and E. Nakamura, J. Am. Chem.
Soc., 2013, 135, 6030; (b) Q. Gu, H. H. Al Mamari, K. Graczyk,
E. Diers and L. Ackermann, Angew. Chem., Int. Ed., 2014, 53, 3868;
(c) R. Shang, L. Ilies and E. Nakamura, J. Am. Chem. Soc., 2015,
137, 7660; (d) L. Ilies, Y. Itabashi, R. Shang and E. Nakamura, ACS
Catal., 2016, 7, 89.
a-hydrogen atoms with aryltrifluoroborates, which was assisted
by a novel weak bidentate directing group. An asymmetric
b-C(sp3)–H arylation via desymmetrization was also presented
by the use of a chiral ligand, offering a promising technique
for producing enantioenriched molecules. This asymmetric
version of the method is under investigation in our laboratory
and will be reported in due course.
We thank the NSFC (Grant No. 21702206), the Natural Science
Foundation of Fujian Province (2017J06007 and 2017J05038), and
the Strategic Priority Research Program of the Chinese Academy of
Sciences (Grant No. XDB20000000) for financial support. Y. Gao
also thanks the National Postdoctoral Program for Innovative
Talents (BX201700244) and the China Postdoctoral Science
Foundation (2017M622087).
6 J. He, R. Takise, H. Fu and J.-Q. Yu, J. Am. Chem. Soc., 2015, 137, 4618.
7 (a) T. E. Barder, S. D. Walker, J. R. Martinelli and S. L. Buchwald,
J. Am. Chem. Soc., 2005, 127, 4685; (b) S. J. Pastine, D. V. Gribkov and
D. Sames, J. Am. Chem. Soc., 2006, 128, 14220; (c) K. S. Chan,
M. Wasa, L. Chu, B. N. Laforteza, M. Miura and J.-Q. Yu, Nat. Chem.,
2014, 6, 146; (d) C. He and M. J. Gaunt, Angew. Chem., Int. Ed., 2015,
54, 15840; (e) X. Wang, D.-G. Yu and F. Glorius, Angew. Chem., Int. Ed.,
2015, 54, 10280; ( f ) J. E. Spangler, Y. Kobayashi, P. Verma,
D.-H. Wang and J.-Q. Yu, J. Am. Chem. Soc., 2015, 137, 11876;
(g) P. Jain, P. Verma, G. Xia and J.-Q. Yu, Nat. Chem., 2016, 9, 140;
(h) Q. Shao, J. He, Q.-F. Wu and J.-Q. Yu, ACS Catal., 2017, 7, 7777;
(i) Q. Shao, Q.-F. Wu, J. He and J.-Q. Yu, J. Am. Chem. Soc., 2018,
140, 5322; ( j) M. Bauer, W. Wang, M. M. Lorion, C. Dong and
L. Ackermann, Angew. Chem., Int. Ed., 2018, 57, 203.
Conflicts of interest
There are no conflicts to declare.
Notes and references
1 (a) M. Wasa, K. M. Engle and J.-Q. Yu, Isr. J. Chem., 2010, 50, 605;
(b) C.-L. Sun, B.-J. Li and Z.-J. Shi, Chem. Commun., 2010, 46, 677;
(c) G. Rouquet and N. Chatani, Angew. Chem., Int. Ed., 2013,
52, 11726; (d) J. He, M. Wasa, K. S. L. Chan, Q. Shao and J.-Q. Yu,
Chem. Rev., 2016, 117, 8754; (e) Z. Chen, B. Wang, J. Zhang, W. Yu,
Z. Liu and Y. Zhang, Org. Chem. Front., 2015, 2, 1107.
8 For examples of arylation of b-C(sp3)–H bonds in aliphatic acids or
their derivatives that contain a-hydrogen atoms with arylhalides:
(a) O. Daugulis, J. Roane and L. D. Tran, Acc. Chem. Res., 2015,
48, 1053; (b) V. G. Zaitsev, D. Shabashov and O. Daugulis, J. Am.
Chem. Soc., 2005, 127, 13154; (c) D. Shabashov and O. Daugulis,
J. Am. Chem. Soc., 2010, 132, 3965; (d) Q. Zhang, K. Chen, W. Rao,
Y. Zhang, F.-J. Chen and B.-F. Shi, Angew. Chem., Int. Ed., 2013,
52, 13588; (e) B. Wang, W. A. Nack, G. He, S.-Y. Zhang and G. Chen,
Chem. Sci., 2014, 5, 3952; ( f ) J. Kim, M. Sim, N. Kim and S. Hong,
Chem. Sci., 2015, 6, 3611; (g) S. Jerhaoui, J. P. Djukic, J. Wencel-
Delord and F. Colobert, Chemistry, 2017, 23, 15594; (h) G. Chen,
Z. Zhuang, G.-C. Li, T. G. Saint-Denis, Y. Hsiao, C. L. Joe and
J.-Q. Yu, Angew. Chem., Int. Ed., 2017, 56, 1506; (i) Y. Zhu, X. Chen,
C. Yuan, G. Li, J. Zhang and Y. Zhao, Nat. Commun., 2017, 8, 14904;
( j) K. K. Ghosh and M. van Gemmeren, Chem. – Eur. J., 2017,
23, 17697; (k) M. Bauer, W. Wang, M. M. Lorion, C. Dong and
L. Ackermann, Angew. Chem., Int. Ed., 2018, 57, 203; (l) X. Zhang,
G. Lu, M. Sun, M. Mahankali, Y. Ma, M. Zhang, W. Hua, Y. Hu,
Q. Wang, J. Chen, G. He, X. Qi, W. Shen, P. Liu and G. Chen,
Nat. Chem., 2018, 10, 540; (m) P.-X. Shen, L. Hu, Q. Shao, K. Hong
and J.-Q. Yu, J. Am. Chem. Soc., 2018, 140, 6545; for more examples,
see ref. 1c and d.
2 For Pd(II)-catalyzed examples: (a) I. Moritanl and Y. Fujiwara, Tetra-
hedron Lett., 1967, 8, 1119; (b) Y. Fujiwara, I. Moritani, S. Danno,
R. Asano and S. Teranishi, J. Am. Chem. Soc., 1969, 91, 7166;
(c) X. Chen, J.-J. Li, X.-S. Hao, C. E. Goodhue and J.-Q. Yu, J. Am.
Chem. Soc., 2006, 128, 78; (d) X. Chen, C. E. Goodhue and J.-Q. Yu,
J. Am. Chem. Soc., 2006, 128, 12634; (e) Z. Shi, B. Li, X. Wan, J. Cheng,
Z. Fang, B. Cao, C. Qin and Y. Wang, Angew. Chem., Int. Ed., 2007,
46, 5554; ( f ) R. Giri, N. Maugel, J.-J. Li, D.-H. Wang, S. P. Breazzano,
L. B. Saunders and J.-Q. Yu, J. Am. Chem. Soc., 2007, 129, 3510;
(g) S. Yang, B. Li, X. Wan and Z. Shi, J. Am. Chem. Soc., 2007,
129, 6066; (h) B.-F. Shi, N. Maugel, Y.-H. Zhang and J.-Q. Yu, Angew.
Chem., Int. Ed., 2008, 47, 4882; (i) S.-D. Yang, C.-L. Sun, Z. Fang,
B.-J. Li, Y.-Z. Li and Z.-J. Shi, Angew. Chem., Int. Ed., 2008, 47, 1473;
( j) D.-H. Wang, T.-S. Mei and J.-Q. Yu, J. Am. Chem. Soc., 2008,
130, 17676; (k) H. Zhou, Y.-H. Xu, W.-J. Chung and T.-P. Loh, Angew.
Chem., Int. Ed., 2009, 48, 5355; (l) C.-L. Sun, N. Liu, B.-J. Li, D.-G. Yu,
Y. Wang and Z.-J. Shi, Org. Lett., 2010, 12, 184; (m) Z. Liang, B. Yao
and Y. Zhang, Org. Lett., 2010, 12, 3185; (n) K. M. Engle, P. S. Thuy-
Boun, M. Dang and J.-Q. Yu, J. Am. Chem. Soc., 2011, 133, 18183;
(o) W. Li, Z. Yin, X. Jiang and P. Sun, J. Org. Chem., 2011, 76, 8543;
(p) J.-Z. Yao, M. Yu and Y. H. Zhang, Adv. Synth. Catal., 2012,
354, 3205; (q) L. Wan, N. Dastbaravardeh, G. Li and J.-Q. Yu,
J. Am. Chem. Soc., 2013, 135, 18056; (r) Z. Liang, J. Yao, K. Wang,
H. Li and Y. Zhang, Chem. – Eur. J., 2013, 19, 16825; (s) C. K.
Seigerman, T. M. Micyus, S. R. Neufeldt and M. S. Sanford,
Tetrahedron, 2013, 69, 5580; (t) B. N. Laforteza, K. S. L. Chan and
J.-Q. Yu, Angew. Chem., Int. Ed., 2015, 54, 11143.
9 (a) K. M. Engle, T.-S. Mei, M. Wasa and J.-Q. Yu, Acc. Chem. Res.,
2012, 45, 788; (b) S. De Sarkar, W. Liu, S. I. Kozhushkov and
L. Ackermann, Adv. Synth. Catal., 2014, 356, 1461.
10 (a) T. G. Saint-Denis, R.-Y. Zhu, G. Chen, Q.-F. Wu and J.-Q. Yu,
Science, 2018, 359, 759; (b) S.-B. Yan, S. Zhang and W.-L. Duan, Org.
¨
Lett., 2015, 17, 2458; (c) G. Chen, W. Gong, Z. Zhuang, M.-S. Andra,
3 For non-Pd(II)-catalyzed examples: (a) F. Kakiuchi, Y. Matsuura,
S. Kan and N. Chatani, J. Am. Chem. Soc., 2005, 127, 5936;
(b) J. Karthikeyan, R. Haridharan and C.-H. Cheng, Angew. Chem.,
Int. Ed., 2012, 51, 12343; (c) R. Shang, L. Ilies, S. Asako and
E. Nakamura, J. Am. Chem. Soc., 2014, 136, 14349; (d) M. Z. Lu,
P. Lu, Y.-H. Xu and T.-P. Loh, Org. Lett., 2014, 16, 2614; (e) M. Shang,
S.-Z. Sun, H.-X. Dai and J.-Q. Yu, Org. Lett., 2014, 16, 5666;
( f ) J. Zheng, Y. Zhang and S. Cui, Org. Lett., 2014, 16, 3560;
Y.-Q. Chen, X. Hong, Y.-F. Yang, T. Liu, K. N. Houk and J.-Q. Yu,
Science, 2016, 353, 1023; (d) H. Wang, H. R. Tong, G. He and
G. Chen, Angew. Chem., Int. Ed., 2016, 55, 15387; (e) Q.-F. Wu,
P.-X. Shen, J. He, X.-B. Wang, F. Zhang, Q. Shao, R.-Y. Zhu,
C. Mapelli, J. X. Qiao, M. A. Poss and J.-Q. Yu, Science, 2017,
355, 499; ( f ) S.-Y. Yan, Y.-Q. Han, Q.-J. Yao, X.-L. Nie, L. Liu and
B.-F. Shi, Angew. Chem., Int. Ed., 2018, 57, 9093.
This journal is ©The Royal Society of Chemistry 2018
Chem. Commun., 2018, 54, 12766--12769 | 12769