Palladium-Catalyzed Electrochemical C-H Bromination Using NH4Br as the Brominating Reagent

Article abstract of DOI:10.1021/acs.orglett.9b00629

The palladium-catalyzed electrochemical C-H bromination of benzamide derivatives under divided cells is developed, in which NH₄Br serves as a brominating reagent and electrolyte. The protocol avoids the use of chemical oxidants and provides an alternative method for the synthesis of aryl bromides.

Full text of DOI:10.1021/acs.orglett.9b00629

Letter
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
pubs.acs.org/OrgLett
Palladium-Catalyzed Electrochemical C−H Bromination Using NH Br
4
as the Brominating Reagent
†
,‡
‡
‡
‡
‡
†
Qi-Liang Yang,
Xiang-Yang Wang, Tong-Lin Wang, Xiang Yang, Dong Liu, Xiaofeng Tong,
,
†
,‡
Xin-Yan Wu,* and Tian-Sheng Mei*
†Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China
University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
‡
State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic
Chemistry, Chinese Academy of Science, 345 Lingling Lu, Shanghai 200032, China
*
S Supporting Information
ABSTRACT: The palladium-catalyzed electrochemical C−H
bromination of benzamide derivatives under divided cells is
developed, in which NH Br serves as a brominating reagent
4
and electrolyte. The protocol avoids the use of chemical
oxidants and provides an alternative method for the synthesis
of aryl bromides.
ryl halides are not only important motifs in many natural
Scheme 1. Catalytic Electrochemical C−H Bromination
1
2
3
A
products, pharmaceuticals, and materials but also
4 5
ubiquitous building blocks for Grignard and cross-coupling
reactions. Thus tremendous efforts have been devoted to
develop useful protocols for the regioselective construction of
6
aryl halides, including electrophilic aromatic halogenations,
Sandmeyer-type reactions, and directed ortho-lithiation.
7
8
However, these methods still have drawbacks, such as limitation
to activated arenes, a narrow substrate scope, and the production
of metal salts as stoichiometric byproducts. In the past decade,
catalytic C−H halogenations of arenes have developed as
9
promising tools to synthesize aryl halides. In this context, four
types of halogenation protocols have been developed: (1) the
1
0
use of halogen (X ); (2) the use of NXS (N-halosuccini-
2
1
1
12,13
mide); (3) the use of Suar
of halides (X ) combined with external chemical oxidants. For
́
ez reagent IOAc,
and (4) the use
−
14
electrochemical C−H bromination of benzamide derivatives
22
example, Yu and coworkers described catalytic C−I bond
with HBr was not successful in Kakiuchi’s protocol. Generally
speaking, aryl bromides serve as important coupling partners in
catalytic cross-coupling reactions and are less accessible than
aryl chlorides, and thus the development of electrochemical C−
H bromination with a broader scope is important for future
synthetic application. Furthermore, the mechanistic study for
the electrochemical C−H bromination is still lacking.
formation using I as the oxidant in the presence of a Pd
2
1
5
catalyst. Glorius and coworkers reported catalytic C−H
16
halogenation using NXS. Shi and coworkers developed Ni-
catalyzed C−H halogenation using lithium halides and
1
7
KMnO . Despite its widespread success, catalytic C−H
4
halogenation still suffers from the use of toxic and dangerous
stoichiometric chemical oxidants. Therefore, it is attractive to
develop an alternative protocol to avoid the use of chemical
oxidants.
Our group recently described catalytic electrochemical C−H
functionalization, electrochemical carboxylation of allyl esters
with carbon dioxide, and electrochemical thiolation of aryhalides
23
with thiols. Herein we describe the Pd-catalyzed electro-
Recently, organic electrochemistry has received much
attention, in which electric current is used an as oxidant or
chemical C−H bromination of benzamides derivatives with
1
8−20
divided cells using NH Br as the brominating agent and
reductant.
For instance, catalytic C−H halogenation of 2-
4
electrolyte (Scheme 1b).
In the beginning, this electrochemical bromination of
benzamide (1a) bearing a removable PIP (2-pyridinylisopropyl)
phenylpyridine using HCl, HBr, or KI as a halogenating agent
under anodic oxidation conditions has been demonstrated by
21
Kakiuchi and coworkers (Scheme 1a). To overcome the
limitation of the pyridine directing group, the same group
recently elegantly developed the catalytic electrochemical C−Cl
Received: February 19, 2019
22
bond formation of benzamide derivatives. However, the
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.9b00629
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a
a
Table 1. Reaction Optimization
Scheme 3. Evaluation of Benzamide Derivatives
b
entry
variation from standard conditions above
yields (%)
1
2
3
4
5
6
7
8
none
93
86
89
84
34
<5
90
92
90
92
93
72
PdBr instead of Pd(OAc)
2
2
Pd(OCOCF ) instead of Pd(OAc)
2
3
2
DMA instead of DMF (anode)
H O instead of DMF (anode)
2
HBr instead of NH Br
LiBr instead of NH Br
NaBr instead of NH Br
80 °C instead of 90 °C
100 °C instead of 90 °C
2.5 mA instead of 5 mA (20 h)
10 mA instead of 5 mA (5 h)
RVC anode instead of Pt anode
undivided cell
4
4
4
c
9
10
11
12
13
14
15
16
d
e
95 (88)
<5%
nr
no Pd(OAc)2
no electric current
nr
a
Reaction conditions: 1a (0.25 mmol), Pd(OAc) (10 mol %) and
2
DMF (10 mL) (anode), and NH Br (0.5 M) and H O (10 mL)
4
2
(
cathode) in H-type divided cell with two platinum electrodes (20
mm × 15 mm × 0.2 mm) and an anion-exchange membrane, 5 mA,
9
b
1
0 °C, 10 h (7.5 F/mol). Yield was determined by H NMR analysis
c
with CH Br as the internal standard. Reaction time is 14 h.
2
2
d
e
Reaction time is 8 h (6.0 F/mol). Isolated yield in parentheses.
Scheme 2. Evaluation of Directing Group
a
Reaction conditions: 1a, 3 (0.25 mmol), Pd(OAc) (10 mol %),
2
DMF (10 mL) (anode), and NH Br (0.5 M), H O (10 mL)
4
2
(
cathode) in H-type divided cell with RVC anode (100 PPI, 10 mm ×
2
4
10 mm × 12 mm), platinum plate cathode (10 mm × 10 mm × 0.2
auxiliary was investigated (Table 1). Under constant-current
b
mm) and an anion-exchange membrane, 5 mA, 90 °C. 3.5 mmol
electrolysis at 5.0 mA, the desired product (2a) was obtained
scale.
1
with 93% H NMR yield in the presence of 10 mol % Pd(OAc)
2
and NH Br (0.5 M in H O) in DMF without another electrolyte
4
2
at 90 °C for 10 h with platinum electrodes (Table 1, entry 1).
PdBr and Pd(COCF ) led to similar results (entries 2 and 3).
tolerated with an undivided cell (entry 14). On the basis of
control experiments, Pd catalyst and electrical current are
necessary for this reaction (entries 15 and 16). It should be
noted that the ammonia (NH ·H O) was generated in the
2
3 2
Different solvents were evaluated, and DMF is optimal (entries 4
22
and 5). Consistent with the Kakiuchi report, HBr is not
effective. It is likely that HBr inhibits the reaction by interacting
with the pyridine group of the substrate. Inorganic bromide salts
3
2
cathodic cell.
including LiBr, NaBr, and NH Br result in good yields (entries
Next, different directing groups were evaluated, and the PIP
directing group is optimal (Scheme 2). Dibromination products
could be achieved with excellent yields (1b) with standard
reaction conditions. Similarly, the 5,7-dichloro-8-aminoquino-
line (AQ) directing group results in a corresponding
dibromination product with slightly lower yield (1c). However,
other directing groups are not effective (1d−1i).
4
6
−8). Lower or higher temperatures result in slightly lower
yields (entries 9 and 10). Decreasing the electric current with a
longer reaction time gives a similar result, although increasing
the electric current gives a lower yield (entries 11 and 12). To
our delight, the use of RVC anode instead of Pt anode gives 88%
isolated yield (entry 13). Unfortunately, the reaction is not
B
DOI: 10.1021/acs.orglett.9b00629
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 4. Preparation and Reactivity of Monomeric
Palladacycle 5
affording brominated product in excellent yields (3n and 3o).
It is worth noting that dibrominated products were obtained
with arenes bearing two ortho C−H bonds in excellent yields
(
4p−4w). The structures of 2b and 4i were further verified by X-
ray analysis. In addition, the gram-scale reaction also gives a
good yield (4i).
According to the literature, palladacycle 5 was synthesized by
treating Pd(OAc) and substrate 1b at 60 °C for 4 h. After the
2
addition of pyridine, complex 6 was obtained, and its structure
was verified by X-ray analysis (Scheme 4). After the anodic
oxidation of complex 5, the brominated product 2b was
achieved with 80% yield. Palladacyle 5 is the active catalyst for
this bromination reaction, which indicates that the reactive
palladacyle for the reaction could be monomeric (Scheme 4).
Finally, cyclic voltammetry (CV) experiments were studied
(
Figure 1). Two obvious oxidative peaks of NH Br (E = 0.74
4 p
and 1.06 V versus Ag/AgCl in MeCN) were observed, which are
−
−
−
probably associated with Br /Br and Br /Br redox
couples.
3
3
2
18n,25
The oxidation wave for complex 5 is E = 1.26
p
V, which is much higher than the oxidation potential of NH Br.
4
Furthermore, excellent yields (80 and 95%) were obtained
under controlled potential electrolysis (E = 0.7 and 0.8 V vs Ag/
AgCl) (Scheme 5).
A reaction mechanism is proposed in the Scheme 6. First, the
Pd species coordinates with 1a to provide palladium(II)
complex A, which undergoes electrophilic palladation to form
−
species B. Next, complex B reacts with Br3 or Br , deriving a
2
Figure 1. Cyclic voltammograms recorded on a Pt electrode (area =
26
bromide, to deliver a high-valent Pd species C. Upon reductive
2
0
.03 cm ): (a) MeCN containing 0.1 M n-Bu NPF ; (b) solution a after
4
6
elimination to form complex D, after ligand exchange to give the
product, the catalytic cycle is thereby completed.
In summary, Pd-catalyzed electrochemical C−H bromination
of benzamide derivatives under divided cells was developed,
affording aryl bromides with good to excellent yields. This
the addition of 5 mM n-Et NBr; (c) solution a after the addition of 2
mM palladacycle 5; and (d) solution b after the addition of 2 mM
palladacycle 5.
4
Scheme 5. Controlled Potential Electrolysis
protocol is obviating the use of a chemical oxidant. NH Br serves
4
as the brominating agent and electrolyte. The preliminary
mechanism study suggests that the active Pd catalyst could be a
monomeric species.
ASSOCIATED CONTENT
Supporting Information
■
*
S
Scheme 6. Proposed Catalytic Cycle
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.orglett.9b00629.
Experimental procedure, characterization data, and copies
1
13
of H and C NMR spectra (PDF)
Accession Codes
CCDC 1885370, 1885380, and 1885382 contain the supple-
mentary 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 Authors
■
As presented in Scheme 3, arenes substituted with alkyl, ether,
fluoro, trifluoromethyl, bromo, nitrile, ester, sulfonyl, nitro, and
chloro groups were tolerated (2a, 2b, 4a−4w), affording good to
excellent yields. In the case of meta-substituted arenes,
bromination preferentially takes place at the less hindered
ortho position (4h−4m). This catalytic electrochemical
bromination protocol is suitable for thiophene substrates,
*
X.-Y.W.: E-mail: xinyanwu@ecust.edu.cn.
T.-S.M.: E-mail: mei7900@sioc.ac.cn.
*
ORCID
Qi-Liang Yang: 0000-0003-4734-5391
Xin-Yan Wu: 0000-0002-6942-7067
Tian-Sheng Mei: 0000-0002-4985-1071
C
DOI: 10.1021/acs.orglett.9b00629
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Notes
(14) For selected examples, see: (a) Song, B.; Zheng, X.; Mo, J.; Xu, B.
́
Adv. Synth. Catal. 2010, 352, 329−335. (b) Zhao, X.; Dimitrijevic, E.;
The authors declare no competing financial interest.
Dong, V. M. J. Am. Chem. Soc. 2009, 131, 3466−3467. (c) Wan, X.; Ma,
Z.; Li, B.; Zhang, K.; Cao, S.; Zhang, S.; Shi, Z. J. Am. Chem. Soc. 2006,
128, 7416−7417. (d) Chen, X.; Hao, X.-S.; Goodhue, C. E.; Yu, J.-Q. J.
Am. Chem. Soc. 2006, 128, 6790−6791.
ACKNOWLEDGMENTS
■
This work was financially supported by the Strategic Priority
Research Program of the Chinese Academy of Sciences (grant
XDB20000000), NSF of China (grants 21772222 and
(15) (a) Chu, L.; Wang, X.-C.; Moore, C. E.; Rheingold, A. L.; Yu, J.-
Q. J. Am. Chem. Soc. 2013, 135, 16344−16347. (b) Wang, X.-C.; Hu, Y.;
Bonacorsi, S.; Hong, Y.; Burrell, R.; Yu, J.-Q. J. Am. Chem. Soc. 2013,
2
1821002), and S&TCSM of Shanghai (grants 17JC1401200
1
(
1
35, 10326−10329.
16) (a) Schroder, N.; Lied, F.; Glorius, F. J. Am. Chem. Soc. 2015, 137,
448−1451. (b) Schroder, N.; Wencel-Delord, J.; Glorius, F. J. Am.
Chem. Soc. 2012, 134, 8298−8301.
17) Zhan, B.-B.; Liu, Y.-H.; Hu, F.; Shi, B.-F. Chem. Commun. 2016,
2, 4934−4937.
18) For recent reviews on organic electrochemistry, see: (a) Yuan, Y.;
and 18JC1415600).
̈
̈
REFERENCES
■
(
5
(
(
1) (a) Blunt, J. W.; Copp, B. R.; Keyzers, R. A.; Munro, M. H. G.;
Prinsep, M. R. Nat. Prod. Rep. 2012, 29, 144−222. (b) Gribble, G. W.
Acc. Chem. Res. 1998, 31, 141−152.
Cao, Y.; Qiao, J.; Lin, Y.; Jiang, X.; Weng, Y.; Tang, S.; Lei, A. Chin. J.
Chem. 2019, 37, 49−52. (b) Tang, S.; Liu, Y.; Lei, A. Chem. 2018, 4, 27.
c) Liu, K.; Song, C.; Lei, A. Org. Biomol. Chem. 2018, 16, 2375−2387.
d) Sauer, G. S.; Lin, S. ACS Catal. 2018, 8, 5175−5187. (e) Parry, J.;
(
2) (a) Wilcken, R.; Zimmermann, M. O.; Lange, A.; Joerger, A.-C.;
Boeckler, F. M. J. Med. Chem. 2013, 56, 1363−1388. (b) Hernandes, M.
Z.; Cavalcanti, S. M. T.; Moreira, D. R. M.; de Azevedo, W. F., Jr.; Leite,
A. C. L. Curr. Drug Targets 2010, 11, 303−314.
(
(
Fu, N.; Lin, S. Synlett 2018, 29, 257−265. (f) Nutting, J. E.; Rafiee, M.;
Stahl, S. S. Chem. Rev. 2018, 118, 4834−4885. (g) Jiang, Y.; Xu, K.;
Zeng, C. Chem. Rev. 2018, 118, 4485. (h) Waldvogel, S. R.; Lips, S.; Selt,
M.; Riehl, B.; Kampf, C. Chem. Rev. 2018, 118, 6706−6765. (i) Moeller,
K. D. Chem. Rev. 2018, 118, 4817−4833. (j) Yang, Q.-L.; Fang, P.; Mei,
T.-S. Chin. J. Chem. 2018, 36, 338−352. (k) Yan, M.; Kawamata, Y.;
Baran, P. S. Chem. Rev. 2017, 117, 13230−13319. (l) Horn, E. J.; Rosen,
B. R.; Baran, P. S. ACS Cent. Sci. 2016, 2, 302. (m) Hou, Z.-W.; Mao, Z.-
Y.; Xu, H.-C. Synlett 2017, 28, 1867−1872. (n) Francke, R.; Little, R. D.
Chem. Soc. Rev. 2014, 43, 2492−2521 For selected reviews on
transition-metal-catalyzed electrochemical C−H functionalization,
see: . (o) Meyer, T. H.; Finger, L. H.; Gandeepan, P.; Ackermann, L.
Trends Chem. 2019, DOI: 10.1016/j.trechm.2019.01.011. (p) Sauer-
mann, N.; Meyer, T. H.; Qiu, Y.; Ackermann, L. ACS Catal. 2018, 8,
(
(
3) Tang, M. L.; Bao, Z. Chem. Mater. 2011, 23, 446−455.
4) Handbook of Grignard Reagents; Silverman, G. S., Rakita, P. E.,
Eds.; Dekker: New York, 1996.
5) For selected reviews, see: (a) Hartwig, J. F. Synlett 2006, 2006,
(
1
4
2
283−1294. (b) Littke, A. F.; Fu, G. C. Angew. Chem., Int. Ed. 2002, 41,
176−4211. (c) Muci, A. R.; Buchwald, S. L. Top. Curr. Chem. 2002,
19, 131−209. (d) Bolm, C.; Hildebrand, J. P.; Muniz, K.; Hermanns,
̃
N. Angew. Chem., Int. Ed. 2001, 40, 3284−3308.
6) De La Mare, P. B. D. Electrophilic Halogenation; Cambridge
University Press: New York, 1976.
7) (a) Hodgson, H. H. Chem. Rev. 1947, 40, 251−277.
b) Sandmeyer, T. Ber. Dtsch. Chem. Ges. 1884, 17, 1633−1635.
8) (a) Snieckus, V. Chem. Rev. 1990, 90, 879−933. (b) Beak, P.;
Snieckus, V. Acc. Chem. Res. 1982, 15, 306−312.
9) For selected reviews, see: (a) Petrone, D. A.; Ye, J.; Lautens, M.
(
(
(
(
7
086−7103. (q) Sauermann, N.; Meyer, T. H.; Ackermann, L. Chem. -
(
Eur. J. 2018, 24, 16209−16217. (r) Ma, C.; Fang, P.; Mei, T.-S. ACS
Catal. 2018, 8, 7179−7189. (s) Jiao, K.-J.; Zhao, C.-Q.; Fang, P.; Mei,
T.-S. Tetrahedron Lett. 2017, 58, 797.
Chem. Rev. 2016, 116, 8003−8104. (b) Engle, K. M.; Mei, T.-S.; Wasa,
M.; Yu, J.-Q. Acc. Chem. Res. 2012, 45, 788−802. (c) Lyons, T. W.;
Sanford, M. S. Chem. Rev. 2010, 110, 1147−1169.
(19) For recent examples on organic electrochemistry, see: (a) Yuan,
(10) (a) Andrienko, O. S.; Goncharov, V. S.; Raida, V. S. Russ. J. Org.
Y.; Yao, A.; Zheng, Y.; Gao, M.; Zhou, Z.; Qiao, J.; Hu, J.; Ye, B.; Zhao,
J.; Wen, H.; Lei, A. iScience 2019, 12, 293−303. (b) Wang, P.; Tang, S.;
Huang, P. F.; Lei, A. W. Angew. Chem., Int. Ed. 2017, 56, 3009−3013.
Chem. 1996, 32, 89. (b) Fahey, D. R. J. Organomet. Chem. 1971, 27,
83−292.
11) For selected examples, see: (a) Li, B.; Liu, B.; Shi, B. F. Chem.
2
(
(
c) Zhang, Z.; Zhang, L.; Cao, Y.; Li, F.; Bai, G.; Liu, G.; Yang, Y.; Mo,
Commun. 2015, 51, 5093−5096. (b) Yu, D.-G.; Gensch, T.; de
Azambuja, F.; Vasquez-Cespedes, S.; Glorius, F. J. Am. Chem. Soc. 2014,
F. Org. Lett. 2019, 21, 762−766. (d) Yan, H.; Hou, Z.-W.; Xu, H.-C.
Angew. Chem., Int. Ed. 2019, 58, 4592. (e) Hou, Z.-W.; Mao, Z.-Y.;
Zhao, H.-B.; Melcamu, Y. Y.; Lu, X.; Song, J.; Xu, H.-C. Angew. Chem.,
Int. Ed. 2016, 55, 9168. (f) Rafiee, M.; Wang, F.; Hruszkewycz, D. P.;
Stahl, S. S. J. Am. Chem. Soc. 2018, 140, 22. (g) Wang, H.; Zhang, J.;
Tan, J.; Xin, L.; Li, Y.; Zhang, S.; Xu, K. Org. Lett. 2018, 20, 2505−2508.
1
36, 17722−17725. (c) Urones, B.; Martinez, A. M.; Rodriguez, N.;
Arrayas, R. G.; Carretero, J. C. Chem. Commun. 2013, 49, 11044−
11046. (d) Sun, X.; Shan, G.; Sun, Y.; Rao, Y. Angew. Chem., Int. Ed.
2
013, 52, 4440−4444. (e) Bedford, R. B.; Haddow, M. F.; Mitchell, C.
J.; Webster, R. L. Angew. Chem., Int. Ed. 2011, 50, 5524−5527.
(
h) Lin, D. Z.; Huang, J. M. Org. Lett. 2018, 20, 2112−2115. (i) Ye, Z.;
Ding, M.; Wu, Y.; Li, Y.; Hua, W.; Zhang, F. Green Chem. 2018, 20,
732−1737. (j) Wang, Q.-Q.; Xu, K.; Jiang, Y.-Y.; Liu, Y.-G.; Sun, B.-
(f) Dudnik, A. S.; Chernyak, N.; Huang, C.; Gevorgyan, V. Angew.
Chem., Int. Ed. 2010, 49, 8729−8732. (g) Arnold, P. L.; Sanford, M. S.;
Pearson, S. M. J. Am. Chem. Soc. 2009, 131, 13912−13913.
1
(
1
h) Whitfield, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129,
5142−15143. (i) Hull, K. L.; Anani, W. Q.; Sanford, M. S. J. Am. Chem.
G.; Zeng, C.-C. Org. Lett. 2017, 19, 5517−5520. (k) Wiebe, A.; Lips, S.;
Schollmeyer, D.; Franke, R.; Waldvogel, S. R. Angew. Chem., Int. Ed.
2017, 56, 14727−14731. (l) Kawamata, Y.; Yan, M.; Liu, Z.; Bao, D.-
H.; Chen, J.; Starr, J.; Baran, P. S. J. Am. Chem. Soc. 2017, 139, 7448−
7451. (m) Horn, E. J.; Rosen, B. R.; Chen, Y.; Tang, J.; Chen, K.;
Eastgate, M. D.; Baran, P. S. Nature 2016, 533, 77−81.
(20) For selected examples on transition-metal-catalyzed electro-
chemical C−H functionalization, see: (a) Qiu, Y.; Scheremetjew, A.;
Ackermann, L. J. Am. Chem. Soc. 2019, 141, 2731−2738. (b) Qiu, Y.;
Stangier, M.; Meyer, T. H.; Oliveira, J. C. A.; Ackermann, L. Angew.
Chem., Int. Ed. 2018, 57, 14179−14183. (c) Mei, R.; Sauermann, N.;
Oliveira, J. C. A.; Ackermann, L. J. Am. Chem. Soc. 2018, 140, 7913−
7921. (d) Sauermann, N.; Meyer, T. H.; Tian, C.; Ackermann, L. J. Am.
Chem. Soc. 2017, 139, 18452. (e) Gao, X.; Wang, P.; Zeng, L.; Tang, S.;
Lei, A. J. Am. Chem. Soc. 2018, 140, 4195−4199. (f) Tang, S.; Wang, D.;
Liu, Y.; Zeng, L.; Lei, A. Nat. Commun. 2018, 9, 798−805. (g) Xu, F.; Li,
Y.-J.; Huang, C.; Xu, H.-C. ACS Catal. 2018, 8, 3820−3824.
Soc. 2006, 128, 7134−7135. (j) Kalyani, D.; Dick, A. R.; Anani, W. Q.;
Sanford, M. S. Org. Lett. 2006, 8, 2523−2526. (k) Kalyani, D.; Dick, A.
R.; Anani, W. Q.; Sanford, M. S. Tetrahedron 2006, 62, 11483−11498.
(l) Dick, A. R.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126,
2
(
300−2301.
12) Concepcion
Suarez, E. Tetrahedron Lett. 1984, 25, 1953−1956.
13) For selected examples, see: (a) Zhu, R.-Y.; Liu, L.-Y.; Yu, J.-Q. J.
, J. I.; Francisco, C. G.; Hernandez, R.; Salazar, J. A.;
́ ́
́
(
Am. Chem. Soc. 2017, 139, 12394−12397. (b) Mei, T.-S.; Wang, D.-H.;
Yu, J.-Q. Org. Lett. 2010, 12, 3140−3143. (c) Li, J.-J.; Giri, R.; Yu, J.-Q.
Tetrahedron 2008, 64, 6979−6987. (d) Li, J.-J.; Mei, T.-S.; Yu, J.-Q.
Angew. Chem., Int. Ed. 2008, 47, 6452−6455. (e) Mei, T.-S.; Giri, R.;
Maugel, N.; Yu, J.-Q. Angew. Chem., Int. Ed. 2008, 47, 5215−5219.
(
2
f) Giri, R.; Chen, X.; Yu, J.-Q. Angew. Chem., Int. Ed. 2005, 44, 2112−
115.
D
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Organic Letters
Letter
(
2
h) Shrestha, A.; Lee, M.; Dunn, A. L.; Sanford, M. S. Org. Lett. 2018,
0, 204−207. (i) Grayaznova, T. V.; Dudkina, Y. B.; Islamov, D. R.;
Kataeva, O. N.; Sinyashin, O. G.; Vicic, D. A.; Budnikova, Y. H. J.
Organomet. Chem. 2015, 785, 68−71. (j) Amatore, C.; Cammoun, C.;
Jutand, A. Adv. Synth. Catal. 2007, 349, 292−296. (k) Freund, M. S.;
Labinger, J. A.; Lewis, N. S.; Bercaw, J. E. J. Mol. Catal. 1994, 87, L11−
L15.
(
21) (a) Saito, F.; Aiso, H.; Kochi, T.; Kakiuchi, F. Organometallics
014, 33, 6704−6707. (b) Aiso, H.; Kochi, T.; Mutsutani, H.; Tanabe,
T.; Nishiyama, S.; Kakiuchi, F. J. Org. Chem. 2012, 77, 7718−7724.
c) Kakiuchi, F.; Kochi, T.; Mutsutani, H.; Kobayashi, N.; Urano, S.;
Sato, M.; Nishiyama, S.; Tanabe, T. J. Am. Chem. Soc. 2009, 131,
1310−11311.
22) Konishi, M.; Tsuchida, K.; Sano, K.; Kochi, T.; Kakiuchi, F. J.
Org. Chem. 2017, 82, 8716−8724.
23) Liu, D.; Ma, H.-X.; Fang, P.; Mei, T.-S. Angew. Chem., Int. Ed.
019, 58, 5033. (b) Jiao, K.-J.; Li, Z.-M.; Xu, X.-T.; Zhang, L.-P.; Li, Y.-
Q.; Zhang, K.; Mei, T.-S. Org. Chem. Front. 2018, 5, 2244−2248.
c) Yang, Q.-L.; Wang, X.-Y.; Lu, J.-Y.; Zhang, L.-P.; Fang, P.; Mei, T.-S.
2
(
1
(
(
2
(
J. Am. Chem. Soc. 2018, 140, 11487−11494. (d) Yang, Q.-L.; Li, C.-Z.;
Zhang, L.-W.; Li, Y.-Y.; Tong, X.; Wu, X.-Y.; Mei, T.-S. Organometallics
2
019, 38, 1208. (e) Ma, C.; Zhao, C.-Q.; Li, Y.-Q.; Zhang, L.-P.; Xu, X.-
T.; Zhang, K.; Mei, T.-S. Chem. Commun. 2017, 53, 12189−12192.
f) Li, Y.-Q.; Yang, Q.-L.; Fang, P.; Mei, T.-S.; Zhang, D. Org. Lett.
017, 19, 2905−2908. (g) Yang, Q.-L.; Li, Y.-Q.; Ma, C.; Fang, P.;
Zhang, X.-J.; Mei, T.-S. J. Am. Chem. Soc. 2017, 139, 3293−3298.
24) For the discovery of PIP directing group, see: Chen, F. J.; Zhao,
S.; Hu, F.; Chen, K.; Zhang, Q.; Zhang, S.-Q.; Shi, B.-F. Chem. Sci. 2013,
, 4187−4192.
25) Yu, L.; Jin, X.; Chen, G. Z. J. Electroanal. Chem. 2013, 688, 371−
78.
26) (a) Hickman, A. J.; Sanford, M. S. Nature 2012, 484, 177−185.
b) Powers, D. C.; Ritter, T. Acc. Chem. Res. 2012, 45, 840−850.
c) Powers, D. C.; Lee, E.; Ariafard, A.; Sanford, M. S.; Yates, B. F.;
(
2
(
4
(
3
(
(
(
Canty, A. J.; Ritter, T. J. Am. Chem. Soc. 2012, 134, 12002−12009.
E
DOI: 10.1021/acs.orglett.9b00629
Org. Lett. XXXX, XXX, XXX−XXX