Copper(II) Triflate-Catalyzed Aerobic Oxidative C-H Functionalization of Glycine Derivatives with Olefins and Organoboranes

Article abstract of DOI:10.1002/adsc.201501015

An economical, and practical copper(II) triflate-catalyzed aerobic oxidative C-H functionalization of glycine derivatives with olefins and organoboranes has been established. The mild reaction has an excellent functional group tolerance, and exhibits a br

Full text of DOI:10.1002/adsc.201501015

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DOI: 10.1002/adsc.201501015
À
Copper(II) Triflate-Catalyzed Aerobic Oxidative C H Function-
alization of Glycine Derivatives with Olefins and Organoboranes
Zhiyu Xie,+a,c Jiong Jia,+b Xigong Liu,a and Lei Liua,b,*
a
School of Pharmaceutical Sciences, Shandong University, Jinan 250012, Peopleꢀs Republic of China
E-mail: leiliu@sdu.edu.cn
b
School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, Peopleꢀs Republic of China
College of Chemistry and Chemical Engineering, Xuchang University, Xuchang 461000, Peopleꢀs Republic of China
c
+
These authors contributed equally to this work.
Received: November 5, 2015; Revised: December 12, 2015; Published online: February 15, 2016
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201501015.
Abstract: An economical, and practical copper(II) allowing for the facile synthesis of diverse substituted
À
triflate-catalyzed aerobic oxidative C H functionali- quinolines and glycine derivatives bearing various
zation of glycine derivatives with olefins and organo- patterns of functionalities in the a-position.
boranes has been established. The mild reaction has
an excellent functional group tolerance, and exhibits
a broad scope with respect to both glycine deriva- Keywords: aerobic oxidation; C H functionalization;
tives and the two types of nucleophilic components, copper; olefins; organoborane.
À
Introduction
grated pattern of functionalities in the a-position of
glycine derivatives. The widespread availability and
À
During the past decade, the direct oxidative C H unique reactivity of olefins and organoboranes have
functionalization of readily accessible substrates has attracted growing interest in exploring new chemistry
emerged as a straightforward and effective alternative in this field because employing either olefins or orga-
to conventional protocols for the synthesis of complex noboranes as coupling partners would afford a great
molecules based on economical and environmental opportunity to prepare structurally diverse complex
issues.[1] In particular, the direct oxidative C H func- quinolines or introduce diverse substituent patterns of
À
tionalization of glycine derivatives with a variety of functionalities into the a-position of glycine moiet-
carbon nucleophiles has gained considerable signifi- ies.[7] Albeit a great innovation, the existing oxidation
cance for the synthesis of structurally diverse a-substi- systems are still not ideal in terms of the economical
tuted a-amino acid derivatives. Since the pioneering and environmental issues.[8–10] For example, the tradi-
study of Li and co-workers in 2008 involving the first tional TBHP/metal system was able to promote the
example of oxidative C H functionalization of glycine C H arylation of glycine amides with diverse arylbor-
esters with malonates, structurally diverse nucleophil- onic acids at 1008C.[8a] However, the corresponding
ic components like carbonyl compounds and indoles glycine esters were not suitable components. More-
have been successfully applied to such transforma- over, a stoichiometric amount of TBHP was required,
tions.[2–6] Recently, a mild and green oxidation system which is moderately expensive and is potentially ex-
involving molecular oxygen as the terminal oxidant plosive. Very recently, Yang and coÀ-workers reported
has been established for b-keto esters, indoles, and that a relative strong oxidant T+BF4 (2,2,6,6-tetrame-
À
À
methylquinolines as nucleophiles by combining transi- thylpiperidine-1-oxoammonium
tetrafluoroborate)
À
tion metal catalysis with visible light catalysis or with can promote the C H arylation of glycine esters with
Brønsted acid catalysis, avoiding the usage of stoichio- arylboronic acids at 608C, and the mild system al-
metric amounts of traditionally adopted oxidants like lowed the development of a catalytic asymmetric var-
DDQ or TBHP. [3c,5]
iant of the transformation.[8b] The same oxidant
À
In spite of this great progress, the specific structures T+BF4 was also able to effect the C H functionaliza-
À
of the above-mentioned nucleophiles restrict the inte- tion of N-arylglycine esters with styrenes, generating
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Table 1. Reaction condition optimization.[a]
diverse quinoline-2-carboxylate derivatives that are
present in a number of biologically active natural
products and synthetic pharmaceuticals.[9] However,
À
T+BF4 is not commercially available, and its prepara-
tion requires extra effort. Additionally, employing
À
a stoichiometric amount of T+BF4 might complicate
the work-up process. To solve such problems, Jia and
À
Wang developed an aerobic oxidative C H function-
alization of N-arylglycine esters with styrenes in the
presence of catalytic amounts of TBPA+C [tris(4-bro-
Entry
Additive
Solvent
Yield [%][b]
mophenyl)aminium
hexachloroantimonate]
and
1
2
3
4
5
6
7
8
9
10
11
12
–
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
CH2Cl2
18
<5
<5
<5
35
55
35
39
42
40
30
28
62
76
80
73
38
15
76
32
15
InCl3.[10] While a great innovation, the radical cation
TBPA+C, the precusor of the real oxidant, is rather ex-
pensive even if only 10 mol% of TBPA+C is employed.
Recently, Huo and co-workers reported an elegant
auto-oxidative coupling system for the same reaction
with styrenes using air as the sole oxidant.[6e] Howev-
er, only moderate reaction efficiency (33–53% yields)
was obtained. The same group also reported that the
transformation can be promoted by CBr4 under an air
atmosphere.[6f] Therefore, the economic and environ-
mental concerns for existing oxidation systems
prompted us to search for a more economical, effi-
cient, and greener oxidation system using molecular
CuBr
CuCl2
Cu(OAc)2
CuBr2
Cu(OTf)2
CuOTf
Cu(MeCN)4PF6
FeCl3
FeCl2
BF3·OEt2
CH3SO3H
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
13[c]
14[d]
15[c,d]
16[c,d]
17[c,d]
18[c,d]
19[c,d]
20[c,d,e]
21[d,f]
À
oxygen as the terminal oxidant for the C H function-
CH3CN
toluene
CHCl3
ClCH2CH2Cl
ClCH2CH2Cl
alization of glycine derivatives with olefins and orga-
noboranes.[11]
Results and Discussion
[a]
General conditions: 1a (0.1 mmol), 2a (0.2 mmol), NHPI
(0.02 mmol), and additive (0.02 mmol) in ClCH2CH2Cl
(1.0 mL) at 408C under an O2 atmosphere (1 atm) for
12 h, unless otherwise specified.
Yield of isolated product.
0.01 mmol of NHPI was employed.
0.01 mmol of Cu(OTf)2 was used.
Air was used instead of O2.
Reaction without NHPI.
N-Hydroxyphthalimide (NHPI) has recently been in-
À
troduced as an effective organocatalyst for C H func-
tionalization initiated by a hydrogen abstraction.[12]
NHPI is a cheap and less toxic reagent, easily pre-
pared by the reaction of phthalic anhydride and hy-
[b]
[c]
[d]
[e]
[f]
À
droxylamine. Therefore, we initially explored the C
H functionalization of glycine ester 1a with styrene
(2a) when NHPI was used as a catalyst (Table 1).
When only NHPI was employed under an O2 atmos-
phere, quinoline 3a was isolated in 18% yield Table 1). Either changing the oxygen atmosphere to
(entry 1, Table 1). A variety of different Lewis acid air or conducting the reaction in the absence of NHPI
additives was investigated to improve the reaction ef- resulted in a dramatic drop of the efficiency (en-
ficiency. While reactions with several copper salts like tries 20 and 21, Table 1).
CuBr, CuCl2, and Cu(OAc)2 did not afford any 3a,
With the optimized reaction conditions in hand, the
Cu(OTf)2 proved to be an ideal additive in terms of scope of olefin coupling partners was studied
the reaction efficiency (entries 2–8, Table 1). Other (Scheme 1). A wide range of electronically varied
Lewis acids like FeCl3, FeCl2, and BF3·OEt2 as well as styrenes with different substitution patterns was well
Brønsted acids like CH3SO3H gave inferior results tolerated with the NHPI-catalyzed aerobic oxidative
À
(entries 6 and 9–12, Table 1). The reaction was found C H functionalization of glycine ester 1a, providing
to be highly dependent on the catalyst loadings of 3a–3f in 70–82% yields (Scheme 1). The reaction effi-
both NHPI and Cu(OTf)2 (entries 6 and 13–15). ciency was found to be not sensitive to the electronic
When the loadings of NHPI and Cu(OTf)2 were re- substituent effect on the aryl rings. Bromo and chloro
duced from 20 mol% to 10 mol%, an 80% isolated substituents were compatible with the mild oxidation
yield of 3a was observed (entry 15, Table 1). The sol- system, which will be beneficial for further modifica-
vent effect was also explored, with dichloroethane tion and diversification. 1,2-Disubstituted olefin 2g
being identified as the optimal choice (entries 15–19, was also a suitable substrate, providing 2,3,4-trisubsti-
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Copper(II) Triflate-Catalyzed Aerobic Oxidative C H Functionalization
Scheme 1. The scope of olefins.
tuted quinoline 3g in excellent regioselectivity with an NHPI, electronically varied arylethynyl trifluorobo-
alkene installed at the 4-position for further manipu- rate salts were well tolerated, delivering the desired
lation. Aliphatic olefin 2h also participated in the cou- alkynylation products 6a–6g in good yields. Aliphatic
pling reaction, albeit a moderate yield was obtained.
ethynyl trifluoroborate salts were also suitable cou-
The scope of glycine derivatives was then explored pling partners for the reaction (6h and 6i). The alken-
(Scheme 2). We first studied the electronic substituent yl organoborane was also an effective component,
effect on the aniline fragment. A broad range of ani- and use of the corresponding boronic acid and boro-
lines 1 bearing electron-donating and electron-with- nate ester species gave comparable results to those of
drawing substituents was compatible with the oxida- the potassium trifluoroborates (6j). Aryl. (5k and 5l)
tion system, affording the corresponding quinoline and heteroaryltrifluoroborates (5m and 5n) participat-
À
products 4b–4f in good yields (Scheme 2). The scope ed in the aerobic oxidative C H arylation smoothly,
of the carbonyl fragment was also examined. Com- although the corresponding boronic acid failed to pro-
monly encountered alkyl esters including methyl 1g, vide the expected product. Aside from the sp- and
isopropyl 1h, tert-butyl 1i, isobutyl 1j, benzyl 1k, and sp2-hybridized organoboranes, sp3-hybridized ones
À
allyl moieties 1m as well as aryl ester 1l were found were also explored, as demonstrated by the C H ben-
to be well tolerated in the oxidative C H functionali- zylation of 1a (6o).[13] The substituent effects on both
À
zation with 2a, yielding quinolines 4g–4m in good the aniline and carboxylic fragments were also stud-
yields. Glycine amides also proved to be suitable com- ied, affording 6p–6r in good yields.
ponents with the mild oxidation system (4n–4p).
Control experiments were performed to gain a pre-
The NHPI/Cu(OTf)2-catalyzed aerobic oxidative liminary understanding of the reaction mechanism
À
system proved to be effective for the C H functional- (Scheme 4). We envisioned that imine 7 might be the
ization of glycine esters with organoboranes, as dem- intermediate for the subsequent addition of organo-
onstrated by the coupling of 1a with potassium tri- boranes or styrenes. Therefore, 7 was prepared and
fluoroborate salt 5a, affording alkynylated 6a in 73% subjected to the standard conditions (Scheme 4).[14]
yield (Scheme 3).[13] The further study revealed that Comparable results to those starting from glycine
NHPI was not a prerequisite for the coupling, and the ester 1a were obtained in the presence of Cu(OTf)2,
Cu(OTf)2-catalyzed reaction without NHPI gave 6a in indicating that imine 7 should be the intermediate for
71% yield. Under the optimized conditions without both transformations. With respect to the reaction
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Scheme 2. The scope of N-arylglycine derivatives.
À
Scheme 3. Cu(OTf)2-catalyzed aerobic oxidative C H functionalization of glycine esters with organoboranes.
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Copper(II) Triflate-Catalyzed Aerobic Oxidative C H Functionalization
Conclusions
In conclusion, a mild and economical Cu(II)-catalyzed
À
aerobic oxidative C H functionalization of glycine
derivatives with olefins and organoboranes has been
established. The reaction has an excellent functional
group tolerance, and exhibits a broad scope with re-
spect to both glycine derivatives and nucleophilic
components. The employment of cheap and non-toxic
NHPI as the co-catalyst for the reaction with olefins
makes the synthesis of diverse substituted quinolines
practical and sustainable. With respect to organobor-
anes, structurally and electronically varied alkynyl, al-
kenyl, aryl, and benzyl organoboranes proved to be
compatible with the mild oxidation system, allowing
diverse patterns of functionalities to be integrated in
the a-position of the glycine derivatives.
Scheme 4. Control experiments.
with imine 7, a diminished yield was observed in the
absence of Cu(OTf)2, implying that the copper salt
should activate 7 for nucleophilic attack (Scheme 4b).
À
Given that NHPI was not a prerequisite for the C
Experimental Section
H functionalization of glycine esters with organobor-
anes, we envisioned that glycine ester 1 can be oxi-
dized by Cu(OTf)2 under an O2 atmosphere, generat-
ing imine intermediate 7. Then, 7 might be activated
by Cu(OTf)2 for the subsquent nucleophilic addition
by organoborane 5 (Figure 1). When olefin 2 was
used as the coupling partner, Cu(OTf)2 might catalyze
the reaction of imine 7 with 2 giving tetrahydroquino-
line 8. Since NHPI was crucial to the reaction effi-
ciency, we believed that PINO (phthalimide N-oxyl),
generated through the interaction between NHPI and
dioxygen, might be in essential for the oxidation of 8
General Experimental Methods
Proton (1H NMR) and carbon (13C NMR) nuclear magnetic
resonance spectra were recorded at 600 MHz, 400 MHz,
300 MHz and 151 MHz, 101 MHz, 75 MHz, respectively.
The chemical shifts are given in parts per million (ppm) on
the delta (d) scale. The solvent peak was used as a reference
value, for 1H NMR: CDCl3 =7.27 ppm, for 13C NMR:
CDCl3 =77.23. Infrared spectra were recorded on an FT-IR
spectrometer with KBr discs. Analytical TLC was performed
on precoated silica gel GF254 plates. Column chromatogra-
phy was carried out on silica gel (200–300 mesh). HR-MS
were carried out on an Orbitrap analyzer. CH2Cl2 and DCE
were distilled from CaH2. Cu(OTf)2 (98%) and NHPI
(97%) were purchased from Sigma–Aldrich Corporation
and used as received. Glycine derivatives 1a–1n were syn-
thesized according to the known procedures.[3b,5] Organobor-
anes 5 were prepared according to the known literature.[11h]
À
to provide quinoline 9. Such a PINO-catalyzed C H
oxidation might also exist in the conversion of 1 to
imine 7.
Figure 1. The plausible mechanism.
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Procedure for the Synthesis of 3a through
NHPI-Catalyzed Aerobic Oxidative C H
Functionalization of Glycine Ester 1a with Styrene 2a
Acknowledgements
À
This work was supported by the National Science Foundation
of China (No. 21202093 and 21472112), the Program for
New Century Excellent Talents in University (No. NCET-13–
0346), the Shandong Science Fund for Distinguished Young
Scholars (JQ201404), and the Fundamental Research Funds
of Shandong University (No. 2014JC005 and 2015JC035).
To a solution of the glycine ester 1a (38.6 mg, 0.2 mmol) and
styrene 2a (46 mL, 0.4 mmol) in anhydrous DCE (2 mL) was
added Cu(OTf)2 (7.2 mg, 0.1 equiv.) and NHPI (3.3 mg,
0.1 equiv.). The mixture was stirred at 408C under a dioxygen
atmosphere (dioxygen balloon, 1 atm) overnight. Subse-
quently, the volatiles were removed under reduced pressure
and the residue was purified by flash chromatography on
silica gel using EtOAc/petroleum ether (10:90) as eluent to
give the desired 3a as a pale yellow solid; yield: 46.6 mg
(80%).
References
[1] For selected reviews, see: a) C.-J. Li, Z. Li, Pure Appl.
Chem. 2006, 78, 935; b) C.-J. Li, Acc. Chem. Res. 2009,
42, 335; c) C. Scheuermann, Chem. Asian J. 2010, 5,
436; d) J. A. Ashenhurst, Chem. Soc. Rev. 2010, 39,
540; e) S. H. Cho, J. Y. Kim, J. Kwak, S. Chang, Chem.
Soc. Rev. 2011, 40, 5068; f) J. Le Bras, J. Muzart, Chem.
Rev. 2011, 111, 1170; g) C. S. Yeung, V. M. Dong,
Chem. Rev. 2011, 111, 1215; h) C. Liu, H. Zhang, W.
Shi, A. Lei, Chem. Rev. 2011, 111, 1780; i) C. Zhang, C.
Tang, N. Jiao, Chem. Soc. Rev. 2012, 41, 3464; j) S. A.
Girard, T. Knauber, C.-J. Li, Angew. Chem. 2014, 126,
76; Angew. Chem. Int. Ed. 2014, 53, 74; k) M. Kluss-
mann, D. Sureshkumar, Synthesis 2011, 353; l) S. Mura-
hashi, D. Zhang, Chem. Soc. Rev. 2008, 37, 1490.
[2] L. Zhao, C.-J. Li, Angew. Chem. 2008, 120, 7183;
Angew. Chem. Int. Ed. 2008, 47, 7075.
Procedure for the Synthesis 6a through Cu(OTf)2-
À
Catalyzed Aerobic Oxidative C H Functionalization
of Glycine Ester 1a with Organoborane 5a
A solution of the glycine ester 1a (38.6 mg, 0.2 mmol) and
Cu(OTf)2 (7.2 mg, 0.1 equiv.) in anhydrous CH2Cl2 (2 mL)
was stirred at 408C under a dioxygen atmosphere (dioxygen
balloon, 1 atm). After all the glycine derivative 1a had dis-
appeared, the organoborane 5a (83.2 mg, 0.4 mmol) was
added and the mixture was stirred at room temperature
under an N2 atmosphere overnight. Then the reaction sol-
vent was removed under reduced pressure and the residue
was purified by flash chromatography on silica gel using
EtOAc/petroleum ether (3:97) as eluent to give the desired
6a as a pale yellow solid; yield: 41.7 mg (71%).
[3] a) J. Xie, Z.-Z. Huang, Angew. Chem. 2010, 122, 10379;
Angew. Chem. Int. Ed. 2010, 49, 10181; b) G. Zhang, Y.
Zhang, R. Wang, Angew. Chem. 2011, 123, 10613;
Angew. Chem. Int. Ed. 2011, 50, 10429; c) X.-W. Gao,
Q.-Y. Meng, M. Xiang, B. Chen, K. Feng, C.-H. Tung,
L. Z. Wu, Adv. Synth. Catal. 2013, 355, 2158.
Procedure for the Preparation of 3a through the
Reaction of 7 with 2a
[4] W.-T. Wei, R.-J. Song, J.-H. Li, Adv. Synth. Catal. 2014,
356, 1703.
To a solution of the imine 7 (38.3 mg, 0.2 mmol) and styrene
2a (46 mL, 0.4 mmol) in anhydrous DCE (2 mL) was added
Cu(OTf)2 (7.2 mg, 0.1 equiv.) and NHPI (3.3 mg, 0.1 equiv.).
The mixture was stirred at 408C under a dioxygen atmos-
phere (dioxygen balloon, 1 atm) overnight. Subsequently,
the volatiles were removed under reduced pressure and the
residue was purified by flash chromatography on silica gel
using EtOAc/petroleum ether (10:90) as eluent to give the
desired 3a as a pale yellow solid; yield: 49.5 mg (85%).
[5] Z.-Q. Zhu, P. Bai, Z.-Z. Huang, Org. Lett. 2014, 16,
4881.
[6] a) S. Zhu, M. Rueping, Chem. Commun. 2012, 48,
11960; b) J.-C. Wu, R.-J. Song, Z.-Q. Wang, X.-C.
Huang, Y.-X. Xie, J.-H. Li, Angew. Chem. 2012, 124,
3509; Angew. Chem. Int. Ed. 2012, 51, 3453; c) Z.-Q.
Wang, M. Hu, X.-C. Huang, L.-B. Gong, Y.-X. Xie, J.-
H. Li, J. Org. Chem. 2012, 77, 8705; d) C. Huo, C.
Wang, M. Xu, X. Jia, H. Xie, Y. Yuan, Adv. Synth.
Catal. 2014, 356, 411; e) C. Huo, Y. Yuan, M. Wu, X.
Jia, X. Wang, F. Chen, J. Tang, Angew. Chem. 2014,
126, 13762; Angew. Chem. Int. Ed. 2014, 53, 13544;
f) C. Huo, H. Xie, M. Wu, X. Jia, X. Wang, F. Chen, J.
Tang, Chem. Eur. J. 2015, 21, 5723; g) C. Huo, M. Wu,
F. Chen, X. Jia, Y. Yuan, H. Xie, Chem. Commun.
2015, 51, 4708; h) C. Huo, F. Chen, Y. Yuan, H. Xie, Y.
Wang, Org. Lett. 2015, 17, 5028; i) C. Huo, Y. Yuan, F.
Chen, J. Tang, Y. Wang, Org. Lett. 2015, 17, 4208; j) C.
Huo, C. Wang, C. Sun, X. Jia, X. Wang, W. Chang, M.
Wu, Adv. Synth. Catal. 2013, 355, 1911; k) C. Huo, Y.
Yuan, F. Chen, Y. Wang, Adv. Synth. Catal. 2015, 357,
3648.
Procedure for the Synthesis of 6a through the
Reaction of 7 with 5a
To a solution of the imine 7 (38.3 mg, 0.2 mmol) and
Cu(OTf)2 (7.2 mg, 0.1 equiv.) in anhydrous CH2Cl2 (2 mL)
was added the organoborane 5a (83.2 mg, 0.4 mmol) and the
mixture was stirred at room temperature under an N2 at-
mosphere overnight. Then the solvent was removed under
reduced pressure and the residue was purified by flash chro-
matography on silica gel using EtOAc/petroleum ether
(3:97) as eluent to give the desired 6a as a pale yellow solid;
yield: 44.0 mg (75%).
[7] a) H. Kim, D. W. C. MacMillan, J. Am. Chem. Soc.
2008, 130, 398; b) D. K. Nielsen, A. G. Doyle, Angew.
Chem. 2011, 123, 6180; Angew. Chem. Int. Ed. 2011, 50,
6056; c) T. J. A. Graham, A. G. Doyle, Org. Lett. 2012,
924
asc.wiley-vch.de
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2016, 358, 919 – 925

À
FULL PAPERS
Copper(II) Triflate-Catalyzed Aerobic Oxidative C H Functionalization
14, 1616; d) T. J. A. Graham, J. D. Shields, A. G. Doyle,
Chem. Sci. 2011, 2, 980; e) T. A. Mitchell, J. W. Bode, J.
Am. Chem. Soc. 2009, 131, 18057; f) C.-V. T. Vo, T. A.
Mitchell, J. W. Bode, J. Am. Chem. Soc. 2011, 133,
14082; g) R. A. Batey, D. B. MacKay, V. Santhakumar,
J. Am. Chem. Soc. 1999, 121, 5075; h) I. B. Seiple, S.
Su, R. A. Rodriguez, R. Gianatassio, Y. Fujiwara, A. L.
Sobel, P. S. Baran, J. Am. Chem. Soc. 2010, 132, 13194;
i) Y. Fujiwara, V. Domingo, I. B. Seiple, R. Gianatassio,
M. Del Bel, P. S. Baran, J. Am. Chem. Soc. 2011, 133,
3292; j) D. J. Clausen, P. E. Floreancig, J. Org. Chem.
2012, 77, 6574.
[11] Selected examples of oxidative C-H functionalization
reaction development from our group: a) M. Wan, H.
Lou, L. Liu, Chem. Commun. 2015, 51, 13953;b) X.
Liu, S. Sun, Z. Meng, H. Lou, L. Liu, Org. Lett. 2015,
17, 2396; c) S. Sun, C. Li, P. E. Floreancig, H. Lou, L.
Liu, Org. Lett. 2015, 17, 1684; d) X. Liu, Z. Meng, C.
Li, H. Lou, L. Liu, Angew. Chem. 2015, 127, 6110;
Angew. Chem. Int. Ed. 2015, 54, 6012; e) F. Li, Z.
Meng, J. Hua, W. Li, H. Lou, L. Liu, Org. Biomol.
Chem. 2015, 13, 5710; f) W. Chen, Z. Xie, H. Zheng, H.
Lou, L. Liu, Org. Lett. 2014, 16, 5988; g) M. Wan, Z.
Meng, H. Lou, L. Liu, Angew. Chem. 2014, 126, 14065;
Angew. Chem. Int. Ed. 2014, 53, 13845; h) Z. Xie, L.
Liu, W. Chen, H. Zheng, Q. Xu, H. Yuan, H. Lou,
Angew. Chem. 2014, 126, 3985; Angew. Chem. Int. Ed.
2014, 53, 3904; i) Z. Meng, S. Sun, H. Yuan, H. Lou, L.
Liu, Angew. Chem. 2014, 126, 553; Angew. Chem. Int.
Ed. 2014, 53, 543; j) X. Liu, B. Sun, Z. Xie, X. Qin, L.
Liu, H. Lou, J. Org. Chem. 2013, 78, 3104.
[8] a) L. Zhao, O. BaslØ, C.-J. Li, Proc. Natl. Acad. Sci.
USA 2009, 106, 4106; b) X.-H. Wei, G.-W. Wang, S.-D.
Yang, Chem. Commun. 2015, 51, 832.
[9] a) H. Richter, O. G. MancheÇo, Org. Lett. 2011, 13,
6066; b) R. Rohlmann, T. Stopka, H. Richter, O. G.
MancheÇo, J. Org. Chem. 2013, 78, 6050.
[10] a) X.-D. Jia, F.-F. Peng, C. Qing, C.-D. Huo, X.-C.
Wang, Org. Lett. 2012, 14, 4030; b) X.-D. Jia, Y.-X.
Wang, F.-F. Peng, C.-D. Huo, L.-L. Yu, X.-C. Wang, J.
Org. Chem. 2013, 78, 9450; c) Y.-X. Wang, F.-F. Peng, J.
Liu, C.-D. Huo, X.-C. Wang, X.-D. Jia, J. Org. Chem.
2015, 80, 609; d) X.-D. Jia, Y.-X. Wang, F.-F. Peng, C.-
D. Huo, L.-L. Yu, J. Liu, X.-C. Wang, Adv. Synth.
Catal. 2014, 356, 1210; e) J. Liu, Y.-X. Wang, L.-L. Yu,
C.-D. Huo, X.-C. Wang, X.-D. Jia, Adv. Synth. Catal.
2014, 356, 3214; f) J. Liu, F. Liu, Y. Zhu, X. Ma, X. Jia,
Org. Lett. 2015, 17, 1409.
[12] F. Recupero, C. Punta, Chem. Rev. 2007, 107, 3800.
[13] The reason for the employment of alkynyl and benzyl
potassium trifluoroborate salts instead of the corre-
sponding boronic acids is that the preparation and pu-
rification of the latter are much more difficult than
those of the former.
[14] H. Huang, H. Jiang, K. Chen, H. Liu, J. Org. Chem.
2009, 74, 5476.
Adv. Synth. Catal. 2016, 358, 919 – 925
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