Gold-Catalyzed Intermolecular [4+2] Annulation of 2-Ethynylanilines with Ynamides: An Access to Substituted 2-Aminoquinolines

Article abstract of DOI:10.1002/adsc.201800341

A gold-catalyzed intermolecular [4+2] annulation of easily accessible 2-ethynylanilines with ynamides offers a highly region-selective, modular, efficient, and atom-economical strategy for the synthesis of substituted 2-aminoquinolines in up to 93% yield. (Figure presented.).

Full text of DOI:10.1002/adsc.201800341

Title: Gold-Catalyzed Intermolecular [4+2] Annulation of 2-
Ethynylanilines with Ynamides: An Access to Substituted 2
Aminoquinolines
Authors: Ximei Zhao, Xinlong Song, Hongming Jin, Zhongyi Zeng,
Qian Wang, Matthias Rudolph, Frank Rominger, and A.
Stephen K. Hashmi
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.201800341
Link to VoR: http://dx.doi.org/10.1002/adsc.201800341

10.1002/adsc.201800341
Advanced Synthesis & Catalysis
Gold-Catalyzed
Intermolecular
[4+2]
Annulation
of
2-Ethynylanilines with Ynamides: An Access to Substituted
2-Aminoquinolines
Ximei Zhao,† Xinlong Song,† Hongming Jin,† Zhongyi Zeng,† Qian Wang,† Matthias Rudolph,†
Frank Rominger,† and A. Stephen K. Hashmi*,†,‡
†Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld
270, 69120 Heidelberg, Germany
‡Chemistry Department, Faculty of Science, King Abdulaziz University (KAU), 21589 Jeddah,
Saudi Arabia
*Corresponding author (Fax: (+49)-6221-54-4205; E-mail: hashmi@hashmi.de; Homepage:
http://www.hashmi.de)
Abstract
A gold-catalyzed intermolecular [4+2] annulation of easily accessible
2-ethynylanilines with ynamides offers a highly region-selective, modular, efficient,
and atom-economical strategy for the synthesis of substituted 2-aminoquinolines in up
to 93% yield.
Key words: anilines, gold catalysis, heterocycles, quinolones, ynamides
1
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
Quinolines are pharmacologically important alkaloids that are ubiquitous in natural
products. They are synthetically privileged scaffolds in medicinal chemistry[1] owing
to various biological activities such as antimalarial,[1a,1j]antimicrobial,[1g,1i]
anticancer,[1g,1k] and anti-inflammatory[1g] properties. In this family, 2-aminoquinoline
motifs are of great interest due to their unique contribution to the biological activity of
pharmaceutical and agrochemical molecules[2] (Figure 1). For example
2-aminoquinolines have been reported to inhibit beta-site amyloid precursor protein
cleaving enzyme 1 (BACE1) which is revelent for Alzheimer’s disease therapeutics.[3]
Traditionally, 2-aminoquinolines are synthesized by the C2-halogenation of quinoline
N-oxides, which are available by oxygenation of quinolines with m-CPBA, followed
by deoxygenation and amination via aromatic nucleophilic substitution under basic
conditions[2b,2h-j,4] (Scheme 2a). This approach requires not only pre-activated
substrates but also harsh conditions, which limits the scope and the tolerance of
functional groups. Therefore, the development of an efficient and atom-economical
method for the synthesis of 2-aminoquinoline frameworks is highly desirable.
Figure 1. Selected bioactive compounds with 2-aminoquinoline scaffolds
The recent years have witnessed a significant development of homogeneous gold
2
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
catalysis in synthetic chemistry. The ability to efficiently activate C≡C bonds,[5] has
led to the assembly of diverse structures, especially nitrogen-containing heterocyclic
skeletons like indoles,[6] quinolines,[7] isoquinolines,[8] pyridines,[9] pyrimidines,[10]
and imidazoles.[11] Inspired by these reports and in continuation of our previous work
on gold catalyzed strategies towards 2-aminoquinolines (Scheme 2b),[12] we
envisioned that a gold-catalyzed intermolecular annulation of ynamides[13] with
2-ethynylanilines might enable an easy one step access to 2-aminoquinoline scaffolds.
We herein report the results on the unprecedented gold-catalyzed intermolecular
transformation of ynamides and 2-ethynylaniline under mild conditions.
Scheme 1. Traditional and gold-catalyzed syntheses of 2-aminoquinoline
frameworks
We optimized the reaction conditions by using 2-ethynylaniline 1a and ynamide 2a as
model substrates (Table 1). To our delight, treatment of 2-ethynylaniline 1a and
o
ynamide 2a with 5 mol% of PPh3AuCl/AgNTf2 in 1,2-DCE at 80 C (entry 1)
afforded the desired product 3a in 65% yield. The control experiment without catalyst
o
showed no reaction even at 100 C (entry 15). Among the screened solvents, toluene,
CH2Cl2, and CH3CN were less efficient (entry 2-4). The yield increased to 82% by
3
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
o
raising the reaction temperature to 100 C (entry 6), while room temperature and 120
oC were less efficient (entry 5 and 7). Changing the counter anion from NTf2 to OTf,
SbF6, or BF4, significantly decreased the yield (entry 8-10). Other gold catalysts like
JohnPhosAuCl/AgNTf2, IPrAuCl/AgNTf2, NaAuBr4, and KAuBr4 also afforded 3a
but in much lower yields (entry 11-14).
Table 1. Optimization of the reaction conditions.[a]
Entry
Catalyst
Solvent
T [oC]
Yield [%][b]
1
PPh3AuCl/AgNTf2
PPh3AuCl/AgNTf2
PPh3AuCl/AgNTf2
PPh3AuCl/AgNTf2
PPh3AuCl/AgNTf2
PPh3AuCl/AgNTf2
PPh3AuCl/AgNTf2
PPh3AuCl/AgOTf
PPh3AuCl/AgSbF6
PPh3AuCl/AgBF4
JohnphosAuCl/AgNTf2
IPrAuCl/AgNTf2
NaAuBr4
1,2-DCE
Toluene
CH2Cl2
80
80
65
55
60
50
28
80
73
75
45
20
33
25
37
38
2
3
80
4
CH3CN
80
5
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
R.T.
100
120
100
100
100
100
100
100
100
6
7
8
9
10
11
12
13
14
KAuBr4
4
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
15
None
1,2-DCE
100
N.R.[c]
[a] Reaction conditions: 1a (0.2 mmol), 2a (0.4 mmol) and catalyst (5 mol%) reacted
in solvent (0.5 mL). [b] Yield of isolated product after column chromatography. [c]
N.R.: no reaction; starting materials were recovered.
Next, the scope of the reaction was investigated under the optimized conditions (2.0
o
equiv of ynamide, 5 mol% PPh3AuCl/AgNTf2, 1,2-DCE, 100 C) (Table 2). First, we
explored the scope of ynamides with 2-ethynylaniline 1a as a reaction partner.
Aryl-substituted ynamides with substituents at m- and p-positions of the aryl group
gave the corresponding 2-aminoquinolines in significantly higher yields (3c-d, 3f-g)
than o-aryl-substituted ynamides (3b, 3e)which can be attributed to sterical effects.
Ynamides bearing one or two methoxy groups at the aromatic ring, no matter if o-, m,
or p-substitution, afforded products 3e-h in 63-93% yields. Electron-withdrawing
groups including fluorides (3i), chlorides (3j), bromides (3k) also worked well with
58-76% yields. Then the influence of the substituent attached to the ynamide nitrogen
R3 was explored. Various substituents like benzyl (3l), linear (3m) and branched alkyl
(3n, 3o), and cycloalkyl groups (3p) were well compatible, resulting in yields ranging
from 66-91%. Besides the tosyl group, a mesyl and a p-bromobenzenesulfonyl
protecting group also delivered the corresponding product in moderate yield (3q, 3r).
If the arene group was changed from phenyl to heterocycles including furan and
thiophene, the yield decreased dramatically to 22% (3s) and 31% (3t). Importantly,
substituted 2-ethynylanilines bearing an array of functional groups on the aromatic
backbone, including fluoride, chloride, trifluoromethyl, and methyl, all worked well
(3u-y). To verify the structural assignment, an X-ray single crystal structure analysis
of 3a was conducted (Figure 2).[14] Terminal and alkyl-substituted ynamides were
applied as well. But to our disappointment, no reaction with 2-ethynylanilines was
observed.
5
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
6
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
Table 2. Scope of the reaction
Reaction conditions: 1 (0.2 mmol), 2 (0.4 mmol), PPh3AuCl/AgNTf2 (5 mol%), 1,2-DCE (0.5 mL),
100 oC, 20 h, isolated yields.
7
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
Figure 2. Solid state molecular structure of 3a.
Efforts to use internal alkynes to produce the aryl-substituted 3z or the
alkyl-substituted 3aa failed, only complex reaction mixtures could be obtained
(Figure 3).
Figure 3. Internal alkynes failed to yield the products 3z and 3aa.
A plausible mechanism for the gold-catalyzed intermolecular [4+2] annulation of
2-ethynylanilines with ynamides is described in Scheme 2.[15] Initially, the
nucleophilic NH2 moiety of 2-ethynylaniline attacks the gold-activated ynamide A/A’
to form vinyl-gold intermediate B,[16] which after protodeauration[17] gives enamine
intermediate C. A subsequent gold-catalyzed intramolecular cyclization then delivers
intermediate F. Finally, isomerization of the double bond to the aromatic product 3
takes place.
8
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
Scheme 2. Plausible mechanism for the intermolecular annulation
In conclusion, we have developed a facile, efficient, and atom-economical one-step
synthesis of 2-aminoquinolines using a gold-catalyzed intermolecular [4+2]
annulation of 2-ethynylanilines with ynamides. The strategy should be highly
attractive for medicinal and synthetic chemistry. Owing to the readily available
starting materials, the broad substrate scope and the good functional-group tolerance
under the mild reaction conditions this represents an easy-to-apply tool in the hand of
synthetic chemists.
Experimental section
General Procedure: Gold-catalyzed Intermolecular [4+2] Annulation of 2-Ethynylanilines
with Ynamides.
A round bottom flask equipped with a magnetic stir bar was charged with PPh3AuCl (5mol%, 4.9
mg), AgNTf2 (5 mol%, 3.9 mg), and 1,2-DCE (0.5 ml). The mixture was stirred at room
temperaturefor 5minutes. Thereafter, 2-ethynylanilines1 (0.2 mmol) and ynamides 2 (0.4 mmol)
were added, and the reaction mixture was then stirred at 100oC for 20 h. After cooling to
roomtemperature, the mixture was extracted with ethyl acetate and concentrated, and the residue
was purified by chromatography on silica gel (eluent: PE/EA) to give the desired product 3.
9
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
3a: N,4-dimethyl-N-(4-methyl-3-phenylquinolin-2-yl)benzenesulfonamide
White solid; m.p.: 203 oC; Rf = 0.28 (PE/EA = 10:1); 1H NMR (500 MHz,CDCl3) δ 8.05 (d, 1H, J
= 8.5 Hz), 7.90 (d, 1H, J = 8.5 Hz), 7.79 (d, 2H, J = 8.5 Hz), 7.72-7.69 (m, 1H), 7.62-7.59 (m, 1H),
7.53-7.50 (m, 2H), 7.47-7.43 (m, 3H), 7.32 (d, 2H, J = 8.0 Hz), 2.84 (s, 3H), 2.51 (s, 3H), 2.47 (s,
3H); 13C NMR (125 MHz,CDCl3) δ 152.6 (s), 146.0 (s), 145.2 (s), 143.2 (s), 136.9 (s), 136.2 (s),
134.0 (s), 130.4 (d, 2C), 129.5 (d), 129.3 (d), 129.1 (d, 2C), 129.0 (d, 2C), 128.3 (d, 2C), 127.8 (s),
127.6 (d), 127.1 (d), 124.3 (d), 37.1 (q), 21.6 (q), 16.5 (q); IR (ATR): ṽ 3064, 2925, 1701, 1598,
1567, 1496, 1442, 1401, 1344, 1289, 1243, 1188, 1156, 1088, 1072, 1019, 973, 890, 850, 814, 763,
700, 665, 615 cm-1; HRMS (ESI) calcd for [C24H23N2O2S]+ (M + H)+: 403.1475; found: 403.1480
Acknowledgments
X. Z. is grateful to the CSC (China Scholarship Council) for a Ph.D. fellowship, Z. Z.
for a Ph.D. fellowship from the Guangzhou Elites Scholarship Council.
10
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10.1002/adsc.201800341
Advanced Synthesis & Catalysis
References
[1] a) S. J. Kesten, J. Johnson, L. M. Werbel, J. Med. Chem. 1987, 30, 906-911; b) J. J. Kwiek, T.
A. J. Haystead, J. Rudolph, Biochemistry 2004, 43, 4538-4547; c) T. S. Kaufman, E. A. Rúveda,
Angew. Chem., Int. Ed. 2005, 44, 854-885; d) V. Kouznetsov, L. Mendez, C. Gomez, Curr. Org.
Chem. 2005, 9, 141-161; e) J. P. Michael, Nat. Prod. Rep. 2007, 24, 223-246; f) J. Barluenga, F.
Rodriguez, F. J. Fananas, Chem. Asian J. 2009, 4, 1036-1048; g) K. Suresh, B. Sandhya, G.
Himanshu, Mini-Rev. Med. Chem. 2009, 9, 1648-1654; h) S. Andrews, S. J. Burgess, D. Skaalrud,
J. X. Kelly, D. H. Peyton, J. Med. Chem. 2010, 53, 916-919; i) S. Eswaran, A. V. Adhikari, I. H.
Chowdhury, N. K. Pal, K. D. Thomas, Eur. J. Med. Chem. 2010, 45, 3374-3383; j) R. Musiol, M.
Serda, S. Hensel-Bielowka, J. Polanski, Curr. Med. Chem. 2010, 17, 1960-1973; k) V. R. Solomon,
H. Lee, Curr. Med. Chem. 2011, 18, 1488-1508.
[2] a) D. G. Markees, V. C. Dewey, G. W. Kidder, J. Med. Chem. 1970, 13, 324-326; b) A. A.
Alhaider, M. A. Abdelkader, E. J. Lien, J. Med. Chem. 1985, 28, 1394-1398; c) S. F. Campbell, J.
D. Hardstone, M. J. Palmer, J. Med. Chem. 1988, 31, 1031-1035; d) J. R. Pfister, J. Nat. Prod.
1988, 51, 969-970; e) N. Rashed, E.-S. I. Ibrahim, E. S. H. El Ashry, Carbohydr. Res. 1994, 254,
295-300; f) L. Kaczmarek, W. Peczyńska-Czoch, J. Osiadacz, M. Mordarski, W. A. Sokalski, J.
Boratyński, E. Marcinkowska, H. Glazman-Kuśnierczyk, C. Radzikowski, Bioorg. Med. Chem.
1999, 7, 2457-2464; g) S. R. Inglis, C. Stojkoski, K. M. Branson, J. F. Cawthray, D. Fritz, E.
Wiadrowski, S. M. Pyke, G. W. Booker, J. Med. Chem. 2004, 47, 5405-5417; h) R. Arienzo, D. E.
Clark, S. Cramp, S. Daly, H. J. Dyke, P. Lockey, D. Norman, A. G. Roach, K. Stuttle, M.
Tomlinson, M. Wong, S. P. Wren, Bioorg. Med. Chem. Lett. 2004, 14, 4099-4102; i) S. Inglis, R.
Jones, D. Fritz, C. Stojkoski, G. Booker, S. Pyke, Org. Biomol. Chem. 2005, 3, 2543-2557; j) T.
Ulven, T. M. Frimurer, J.-M. Receveur, P. B. Little, Ø. Rist, P. K. Nørregaard, T. Högberg, J. Med.
Chem. 2005, 48, 5684-5697; k) S. R. Inglis, R. K. Jones, G. W. Booker, S. M. Pyke, Bioorg. Med.
Chem. Lett. 2006, 16, 387-390; l) J. K. Holden, M. C. Lewis, M. A. Cinelli, Z. Abdullatif, A. V.
Pensa, R. B. Silverman, T. L. Poulos, Biochemistry 2016, 55, 5587-5594; m) M. A. Cinelli, H. Li,
G. Chreifi, T. L. Poulos, R. B. Silverman, J. Med. Chem. 2017, 60, 3958-3978.
[3] a) E. W. Baxter, K. A. Conway, L. Kennis, F. Bischoff, M. H. Mercken, H. L. De Winter, C. H.
Reynolds, B. A. Tounge, C. Luo, M. K. Scott, Y. Huang, M. Braeken, S. M. A. Pieters, D. J. C.
Berthelot, S. Masure, W. D. Bruinzeel, A. D. Jordan, M. H. Parker, R. E. Boyd, J. Qu, R. S.
Alexander, D. E. Brenneman, A. B. Reitz, J. Med. Chem. 2007, 50, 4261-4264; b) R. Silvestri,
Med. Res. Rev. 2009, 29, 295-338; c) Y. Cheng, T. C. Judd, M. D. Bartberger, J. Brown, K. Chen,
R. T. Fremeau, D. Hickman, S. A. Hitchcock, B. Jordan, V. Li, P. Lopez, S. W. Louie, Y. Luo, K.
Michelsen, T. Nixey, T. S. Powers, C. Rattan, E. A. Sickmier, D. J. St. Jean, R. C. Wahl, P. H. Wen,
11
This article is protected by copyright. All rights reserved.

10.1002/adsc.201800341
Advanced Synthesis & Catalysis
S. Wood, J. Med. Chem. 2011, 54, 5836-5857.
[4] a) D. Wang, H. Jia, W. Wang, Z. Wang, Tetrahedron Lett. 2014, 55, 7130-7132; b) P. Sharma,
R. S. Liu, Chem. - Eur. J. 2015, 21, 4590-4594.
[5] Selected reviews on gold catalysis: a) A. S. K. Hashmi, Chem. Rev. 2007, 107, 3180-3211; b)
D. J. Gorin, F. D. Toste, Nature 2007, 446, 395-403; c) A. S. K. Hashmi, M. Rudolph, Chem. Soc.
Rev. 2008, 37, 1766-1775; d) Z. Li, C. Brouwer, C. He, Chem. Rev. 2008, 108, 3239-3265; e) A.
Arcadi, Chem. Rev. 2008, 108, 3266-3325; f) M. Rudolph, A. S. Hashmi, Chem. Soc. Rev. 2012,
41, 2448-2462; g) A. S. K. Hashmi, Acc. Chem. Res. 2014, 47, 864-876; h) L. Zhang, Acc. Chem.
Res. 2014, 47, 877-888; i) H.-S. Yeom, S. Shin, Acc. Chem. Res. 2014, 47, 966-977; j) A. M. Asiri,
A. S. K. Hashmi, Chem. Soc. Rev. 2016, 45, 4471-4503; k) D. Pflästerer, A. S. K. Hashmi, Chem.
Soc. Rev. 2016, 45, 1331-1367.
[6] a) A. Wetzel, F. Gagosz, Angew. Chem., Int. Ed. 2011, 50, 7354-7358; b) B. Lu, Y. Luo, L. Liu,
L. Ye, Y. Wang, L. Zhang, Angew. Chem., Int. Ed. 2011, 50, 8358-8362; c) N. Li, T. Y. Wang, L. Z.
Gong, L. Zhang, Chem. - Eur. J. 2015, 21, 3585-3588; d) C.-H. Shen, Y. Pan, Y.-F. Yu, Z.-S. Wang,
W. He, T. Li, L.-W. Ye, J. Organomet. Chem. 2015, 795, 63-67; e) C. Shu†, Y.-H. Wang, B. Zhou,
X.-L. Li, Y.-F. Ping, X. Lu, L.-W. Ye, J. Am. Chem. Soc. 2015, 137, 9567--9570.
[7] a) C. Gronnier, G. Boissonnat, F. Gagosz, Org. Lett. 2013, 15, 4234-4237; b) S. Zhu, L. Wu, X.
Huang, J. Org. Chem. 2013, 78, 9120-9126.
[8] a) Z. Huo, Y. Yamamoto, Tetrahedron Lett. 2009, 50, 3651-3653; b) Y. Pan, G.-W. Chen, C.-H.
Shen, W. He, L.-W. Ye, Org. Chem. Front. 2016, 3, 491-495.
[9] A. Prechter, G. Henrion, P. Faudot dit Bel, F. Gagosz, Angew. Chem., Int. Ed. 2014, 53,
4959-4963.
[10] Z. Zeng, H. Jin, X. Song, Q. Wang, M. Rudolph, F. Rominger, A. S. Hashmi, Chem. Commun.
2017, 53, 4304-4307.
[11] a) Y. Xiao, L. Zhang, Org. Lett. 2012, 14, 4662-4665; b) Z. Zeng, H. Jin, J. Xie, B. Tian, M.
Rudolph, F. Rominger, A. S. K. Hashmi, Org. Lett. 2017, 19, 1020-1023.
[12] H. Jin, B. Tian, X. Song, J. Xie, M. Rudolph, F. Rominger, A. S. K. Hashmi, Angew. Chem.,
Int. Ed. 2016, 55, 12688-12692.
[13] a) G. Evano, A. Coste, K. Jouvin, Angew. Chem. Int. Ed. 2010, 49, 2840-2859 ; b) K. A.
DeKorver, H. Li, A. G. Lohse, R. Hayashi, Z. Lu, Y. Zhang, R. P. Hsung, Chem. Rev. 2010, 110,
5064-5106; c) M. C. Blanco Jaimes, V. Weingand, F. Rominger, A. S. K. Hashmi, Chem. Eur. J.
2013, 19, 12504–12511, d) E. Rettenmeier, A. M. Schuster, M. Rudolph, F. Rominger, C. Gade, A.
S. K. Hashmi, Angew. Chem. Int. Ed. 2013, 52, 5880-5884; Angew. Chem. 2013, 125, 5993–5997;
e) X.-N. Wang, H.-S. Yeom†, L.-C. Fang, S. He, Z.-X. Ma, B. L. Kedrowski, R. P. Hsung,, Acc.
12
This article is protected by copyright. All rights reserved.

10.1002/adsc.201800341
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Chem. Res. 2014, 47, 560-578; d) G. Evano, C. Theunissen, M. Lecomte, Aldrichimica Acta 2015,
48, 59-70; e) Y. Tokimizu, M. Wieteck, M. Rudolph, S. Oishi, N. Fujii, A. S. K. Hashmi, H. Ohno,
Org. Lett. 2015, 17, 604–607; ;f) F. Pan, C. Shua, L.-W. Ye, Org. Biomol. Chem. 2016, 14,
9456-9465.
[14] CCDC 1584985 (3a) contains the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallographic Data Centre
via https://www.ccdc.cam.ac.uk/structures/.
[15] a) N. Sakai, K. Annaka, A. Fujita, A. Sato, T. Konakahara, J. Org. Chem. 2008, 73,
4160-4165; b) P. Perumal, C. Praveen, S. Jegatheesan, Synlett 2009, 2009, 2795-2800; c) C.
Praveen, P. Perumal, Synthesis 2016, 48, 855-864; d) A. S. K. Hashmi, Angew. Chem. Int. Ed.
2010, 49, 5232-5241; Angew. Chem. 2010, 122, 5360-5369.
[16] A. S. K. Hashmi, A. Schuster, F. Rominger, Angew. Chem. Int. Ed. 2009, 48,
8247-8249; Angew. Chem. 2009, 121, 8396-8398.
[17] a) A. S. K. Hashmi, Catal. Today 2007, 122, 211-214; b) C. M. Krauter, A. S. K.
Hashmi, M. Pernpointner, ChemCatChem 2010, 2, 1226-1230; c) L. Nunes dos Santos
Comprido, J. E. M. N. Klein, G. Knizia, J. Kästner, A. S. K. Hashmi, Chem. Eur. J.
2017, 23, 10901-10905; d) N. Zhou, X.-A. Yuan,Y. Zhao, J. Xie, C. Zhu, Angew.
Chem. Int. Ed. 2018, https://doi.org/10.1002/anie.201800421.
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