Metal-Free Synthesis of 3-Arylquinolin-2-ones from N,2-Diaryl- acrylamides via Phenyliodine(III) Bis(2,2-dimethylpropanoate)- Mediated Direct Oxidative C?C Bond Formation

Article abstract of DOI:10.1002/adsc.201600512

Treatment of N,2-diarylacrylamides with the organoiodine(III) compound phenyliodine(III) bis(2,2-dimethylpropanoate) [PhI(O₂C-t-Bu)₂] and boron trifluoride etherate (BF₃?Et₂O) resulted in a direct and selective oxidative C(sp²)?C(sp²) bond formation leading to a convenient assemblage, under mild conditions, of the biologically important 3-arylquinolin-2-one skeleton. Differing from the five-membered oxindole products from oxidative cyclizations mediated by transition metals, this metal-free approach realized a direct annulation of the N-arylacrylamide into a six-membered 3-arylquinolin-2-one skeleton. (Figure presented.).

Full text of DOI:10.1002/adsc.201600512

UPDATES
DOI: 10.1002/adsc.201600512
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Metal-Free Synthesis of 3-Arylquinolin-2-ones from N,2-Diaryl-
acrylamides via Phenyliodine(III) Bis(2,2-dimethylpropanoate)-
Mediated Direct Oxidative CÀC Bond Formation
Yang Cao,a Hui Zhao,b Daisy Zhang-Negrerie,a Yunfei Du,a,* and Kang Zhaoa,*
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a
Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology,
Tianjin University, Tianjin 300072, People’s Republic of China
Fax: (+86)-22-2740-4031; phone: (+86)-22-2740-4031; e-mail: duyunfeier@tju.edu.cn kangzhao@tju.edu.cn
College of Chemistry and Material Science, Shandong Agricultural University, Taian City, Shandong Province 271018,
Peopleꢀs Republic of China
b
Received: May 14, 2016; Revised: July 20, 2016; Published online on && &&, 0000
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201600512.
anilines[12] withalkynes and a [5+2-1] transformation
Abstract: Treatment of N,2-diarylacrylamides with
between isatins and alkynes[13] have all been applied to
the organoiodine(III) compound phenyliodine(III)
the syntheses of quinolin-2-one compounds. While
each of the aforementioned methods has, in its own
right, unique merits in constructing the corresponding
quinolin-2-one compounds, developing a more effi-
bis(2,2-dimethylpropanoate) [PhI(O2C-t-Bu)2] and
boron trifluoride etherate (BF3·Et2O) resulted in a
direct and selective oxidative C(sp2)ÀC(sp2) bond
formation leading to a convenient assemblage,
cient and/or more economical method, preferably
under mild conditions, of the biologically important
under metal-free conditions and with readily available
3-arylquinolin-2-one skeleton. Differing from the
starting materials remains highly desirable.
five-membered oxindole products from oxidative
It can easily be envisaged that N-arylacrylamide
cyclizations mediated by transition metals, this
metal-free approach realized a direct annulation of
the N-arylacrylamide into a six-membered 3-aryl-
quinolin-2-one skeleton.
derivatives would represent the most logical choice as
substrates for the construction of the 3-quinolin-2-one
skeleton if a direct oxidative C(sp2)ÀC(sp2) bond
formation could be realized. However, to the best of
our knowledge, only a five-membered oxindole frame-
Keywords: 3-arylquinolin-2-ones;
bond formation; organoiodine(III) compounds; ox-
idative annulation
C(sp2)ÀC(sp2)
work was formed, in all reports, via 5-endo cyclization
when N-arylacrylamide was subjected to transition
metal-mediated or light-induced C–H functionaliza-
tion reactions (Scheme 1a).[14] Studies on converting
N-arylacrylamides to the six-membered quinolinone
41 The 3-quinolin-2-one scaffold, especially that of 3- skeleton through direct oxidative C(sp2)ÀC(sp2) bond
42 arylquinolin-2-one, is an important structural motif is formation have been scarce. Recently, Liu and co-
43 not only found in many naturally occurring com- workers[15] demonstrated that, by using a combination
44 pounds[1] and pharmaceutically active molecules pos- of palladium and a cyclic hypervalent iodine oxidant,
45 sessing anticancer,[2] anti-HIV,[3] antibiotic,[4] antivi- N-arylacrylamides could be annulated directly to give
46 ral,[5] antihypersensitivity[5] and other biological the six-membered quinolone compounds (Scheme 1b).
47 activities,[6] but is also used as valuable building blocks The involvement of the transition metal as well as the
48 for the syntheses of many natural alkaloids.[7] For this presence of the picolinamide moiety in the substrate
49 reason, many synthetic efforts have been devoted to was found to be essential for the formation of the CÀ
50 the assemblage of this significant skeleton. Aside from C bond to take place. In 2013, we reported[16] the
¨
51 the well-known Friedlander reaction, Knorr synthesis conversion of N-methyl-N-phenylcinnamides to 3-
52 and Vilsmeier approach,[8] intra-[9a] or intermolecu- arylquinolin-2-ones through a phenyliodine bis(tri-
53 lar[9b,c] carbocyclization of internal alkynes, amidation fluoroacetate) (PIFA)-mediated CÀC bond formation
54 of o-carbonyl-substituted aryl halides,[10] tandem de- concomitant with an exclusive 1,2-aryl shift
55 carboxylative radical addition/cyclization of N-arylcin- (Scheme 1c). However, the migrating aryl group was
56 namides with aliphatic carboxylic acids,[11] carbon- indispensable for the cyclization to occur. In this
57 ylation and annulation of simple CO-containing update, we report a direct oxidative C(sp2)ÀC(sp2)
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Table 1. Optimization of the reaction conditions.[a]
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Entry Oxidant
Additive
(equiv.)
Time Yield
[h]
[%][b]
[c]
1
2
3
4
5
6
7
PIDA
PIDA
PIDA
PIDA
PIDA
PIDA
PIFA
none
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–
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BF3·Et2O (1.0) 1.5
BF3·Et2O (1.2) 1.5
BF3·Et2O (0.5) 2.0
BF3·Et2O (0.3) 4.5
TFA (1.0)
BF3·Et2O (1.0)
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71
79
76
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60
88
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PhI(O2C-t-Bu)2 BF3·Et2O (0.5)
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PhI(O2C-t-Bu)2 BF3·Et2O (0.5) 2.5
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PhI(O2C-t-Bu)2 none 1.0
PhI(O2C-t-Bu)2 BF3·Et2O (0.5) 1.5
PhI(O2C-t-Bu)2 BF3·Et2O (0.5) 1.5
[a]
All reactions were carried out with 1a (1.0 mmol) and
oxidant (1.2 mmol) in DCM (10 mL) at room temperature
unless otherwise stated.
[b]
Isolated yield.
Not detected.
The reactions were run in TFE (10 mL).
The reactions were run in TFA (10 mL).
The reactions were run in HFIP (10 mL).
The reactions were run in MeCN (10 mL).
[c]
[d]
[e]
Scheme 1. Existing strategies for the annulation of N-aryl-
acrylamide derivatives.
[f]
[g]
31 bond formation approach to afford a six-membered 3-
32 arylquinolin-2-one from an N,2-diarylacrylamide com-
Applying the more potent oxidant PIFA led to a
33 pound by applying a hypervalent iodine(III) reagent lowered yield of 60% (Table 1, entry 7). Much screen-
34 as the oxidant in the presence of BF3·Et2O as additive ing of appropriate oxidants led us to discover that
35 (Scheme 1d). This method likely represents the first phenyliodine(III)
bis(2,2-dimethylpropanoate)
36 direct annulation of N-arylacrylamides to construct [PhI(O2C-t-Bu)2] facilitated a much improved, satis-
37 the 3-arylquinolin-2-one skeleton in a metal-free factory yield of 88% (Table 1, entry 8). This result
38 environment.
indicated that a hypervalent iodine reagent bearing a
39
The readily available N,2-diarylacrylamide 1a was bulky ligand was beneficial for the yield of the
40 initially used as a benchmark substrate to probe the reaction. Further attempts to improve the outcome of
41 feasibility of the expected direct oxidative annulation the reaction such as by switching to other solvents
42 facilitated by hypervalent iodine as oxidant. Exposure including 2,2,2-trifluoroethanol (TFE), trifluoroacetic
43 of 1a to phenyliodine diacetate (PIDA) in dichloro- acid (TFA), hexafluoroisopropyl alcohol (HFIP) and
44 methane (DCM) for 24 h showed no cyclized product acetonitrile (MeCN) proved to be futile (Table 1,
45 (Table 1, entry 1). However, when 1.0 equivalent of entries 9–12).
46 BF3·Et2O was introduced to the reaction, the desired
Under the optimized conditions (Table 1, entry 8),
47 product 2a was isolated in 75% yield (Table 1, the generality and scope of this newly established
48 entry 2). Inscreasing the dosage of BF3·Et2O to method was investigated. The results are shown in
49 1.2 equivalents brought about a slightly descreased Table 2. It was found that the alkyl substituent on the
50 yield of 2a (Table 1, entry 3); while a reduced dosage nitrogen atom was crucial, as the reaction for the
51 of 0.5 equivalent improved the yield to 79% (Table 1, unsubstituted substrate (R2 =H) resulted in a complex
52 entry 4). Further decrease of the dosage of BF3·Et2O mixture (not shown). Substrates bearing an alkyl R2
53 to 0.3 equivalent afforded a similar yield, but at the group of various sizes including isopropyl (1b), n-butyl
54 cost of a much lengthened reaction time (Table 1, (1c) and benzyl (1d) were all converted to the
55 entry 5). Switching the additive to trifluoroacetic acid corresponding products in similarly high yields
56 (TFA) significantly decreased the desired product (Table 2, 2b–d).
57 yield to only 43% (Table 1, entry 6).
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Table 2. PhI(O2C-t-Bu)2-mediated synthesis of 3-arylquinolin-2-ones from N,2-diarylacrylamides.[a]
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[a]
Reaction conditions: 1 (1.0 mmol), PhI(O2C-t-Bu)2 (1.2 mmol) in DCM (10 mL) at room temperature.
Isolated yield unless otherwise stated.
The ratio of two separable products, 2j (7-CF3) and 2j’ (5-CF3), was 1.4:1.
The ratio of two separable products, 2k (7-Cl) and 2k’ (5-Cl), was 1.2:1.
[b]
[c]
[d]
We were delighted to see that the method could be Br) groups, all gave similar satisfactory yields like the
37 well applied to substrates with the aryl moieties unsubstituted counterpart (Table 2, 2n–p).
38 bearing electron-donating or electron-withdrawing Special cases were observed for substrates with
39 substituents. Our studies showed that the substituent R3 =OMe (Scheme 2a): Substrate 1s afforded as a by-
40 effects of R1 and R3 were overall insignificant. product the five-membered oxindole product 2s’ (33%
41 Specifically, an electron-donating R1 substituent (Me, yield) in addition to the six-membered product 2s
42 MeO) imposed essentially no effect on the reaction (35% yield); while substrate 1t afforded only the six-
43 yield while an electron-withdrawing group (F, Cl, Br, membered product 2t (21% yield), with no by-product
44 CF3) slightly disfavored the reaction (Table 2, 2e–k’, 2t’; substrates 1u and 1v delivered a complex mixture
45 2q and 2r). In the case of meta-substituted substrates containing no desired product.
46 bearing either a CF3 or a Cl group (Table 2, 2j–2k’),
Additional control experiments revealed that the
47 two separable regioisomeric 3-arylquinolin-2-one vinyl aryl group was indispensable for the desired
48 products 2j/2j’ and 2k/2k’ were formed in each case, cyclization to occur, as, shown in Scheme 2b, the 3-
49 with the cyclization occurring preferentially at the less alkyl-substituted acrylamides 1w–y could not be con-
50 hindered position as one would have expected. ortho- verted to the corresponding products under the
51 Substituted substrate 1l also delivered the correspond- applied, optimized conditions.
52 ing product 2l, albeit in a decreased yield of only 65%,
Based on all the experimental results as well as
53 likely due to the fact there is only one ortho position previous literature reports,[17] a plausible mechanism
54 left to cyclize at as opposed to two in the cases of was formulated. A radical mechanism was ruled out
55 para- and meta-substituted substrates (Table 2, 2l). since the addition of the radical scavenger (TEMPO)
56 The substrates bearing various R3 groups, either had no significant impact on the outcome of the yield.
57 electron-donating (Me) or electron-withdrawing (Cl, As is described in Scheme 3 using 1a as an example,
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Scheme 2. Special cases of the reactions under the standard conditions.
nucleophilicity of the benzene ring, which is consistent
with our experimental results of the yield data listed
in Table 2. Finally, removal of a molecule of phenyl
iodide and pivalic acid in C with the concomitant
abstraction of a proton enabled the rearomatization to
give the title product 2a.
Regarding substrate 1s, in addition to the above
reaction mechanism, the reaction also underwent an
alternative pathway in a competitive manner. As
depicted in Scheme 4, a conjugation occurred due to
Scheme 3. Plausible mechanistic pathway for the formation
of 2a.
45 the alkene moiety in N,2-diarylacrylamide first nucle-
46 ophilically attacked the iodine center in PhI(O2C-t-
47 Bu)2, after being activated by the Lewis acid BF3·Et2
48 O, and gave a benzylic carbocation intermediate A.
49 The crucial role played by the aryl moiety can be
50 explained here for the formation of the benzylic
51 carbocation for extra stability probably required for
52 the reaction path. Next, removal of a proton in A
53 formed the intermediate B in which cyclization
54 occurred to give an ylide intermediate C. In this
55 intramolecular nucleophilic aromatic substitution re-
Scheme 4. Plausible mechanistic pathway for generation
2s’.[18]
56 action step, electron-withdrawing R1 groups would be the presence of the strong electron-donating methoxy
57 expected to disfavor the reaction by decreasing the group after the formation of the carbocation inter-
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Defeo-Jones, R. E. Jones, G. D. Hartman, J. R. Huff,
H. E. Huber, M. E. Duggan, C. W. Lindsley, Bioorg.
Med. Chem. Lett. 2005, 15, 905; c) G. Claassen, E. Brin,
C. Crogan-Grundy, M. T. Vaillancourt, H. Z. Zhang,
S. X. Cai, J. Drewe, B. Tseng, S. Kasibhatla, Cancer Lett.
2009, 274, 243.
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mediate D, and converted D to the oxonium inter-
mediate E. Next, 5-exo cyclization and the abstraction
of a proton from F gave the oxindole G. Finally,
reductive elimination of PhI from G afforded the five-
membered oxindole product 2s’.
In summary, we have described a novel approach
for the construction of the six-membered 3-arylquino-
lin-2-one framework via a hypervalent iodine-medi-
ated direct oxidative C(sp2)ÀC(sp2) bond formation of
[3] M. Patel, J. McHugh, J. Robert, B. C. Cordova, R. M.
Klabe, L. T. Bacheler, S. Erickson-Viitanen, J. D. Rodg-
ers, Bioorg. Med. Chem. Lett. 2001, 11, 1943.
[4] R. M. Forbis, K. L. Rinehart, J. Am. Chem. Soc. 1973,
95, 5003.
[5] A. L. Hopkins, J. Ren, J. Milton, R. J. Hazen, J. H.
Chan, D. I. Stuart, D. K. Stammers, J. Med. Chem. 2004,
47, 5912.
[6] For selected examples, see: a) T. N. Glasnov, W. Stadlba-
uer, C. O. Kappe, J. Org. Chem. 2005, 70, 3864; b) J. M.
Kraus, C. L. M. J. Verlinde, M. Karimi, G. I. Lepesheva,
M. H. Gelb, F. S. Buckner, J. Med. Chem. 2009, 52,
1639; c) J. M. Kraus, H. B. Tatipaka, S. A. McGuffin,
N. K. Chennamaneni, M. Karimi, J. Arif, C. L. M. J.
Verlinde, F. S. Buckner, M. H. Gelb, J. Med. Chem.
2010, 53, 3887; d) A. Dolꢂans-Jordheim, J.-B. Veron, O.
Fendrich, E. Bergeron, A. Montagut-Romans, Y.-S.
Wong, B. Furdui, J. Freney, C. Dumontet, A. Boumend-
jel, ChemMedChem 2013, 8, 652; e) R. W. Carling, P. D.
Leeson, K. W. Moore, J. D. Smith, C. R. Moyes, I. M.
Mawer, S. Thomas, T. Chan, R. Baker, J. Med. Chem.
1993, 36, 3397.
10 N,2-diarylacrylamide derivatives. The methodology
11 features readily available starting materials, mild and
12 transition metal-free reaction conditions, and toler-
13 ance of a wide range of functional groups. The
14 importance of the 3-arylquinolin-2-one compounds
15 should render this method a useful organic synthetic
16 tool.
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Experimental Section
General Procedure for Preparation of 3-Aryl-
quinolin-2-ones 2
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To a solution of 1 (1.0 mmol) in DCM (6.0 mL) was slowly
added PhI(O2C-t-Bu)2 (1.2 mmol). Then,
a solution of
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BF3 Et2O (0.5 mmol) in DCM (4 mL) was added dropwise to
the above mixture under stirring. The resulting mixture
remained at room temperature under stirring, and the
progress of the reaction was monitored by TLC. Upon
completion, the reaction mixture was poured into cold water
(20 mL) and extracted with CH2Cl2 (3320 mL). The com-
bined organic layer was washed with brine (50 mL) before
being dried over Na2SO4. The solvent was removed under
vacuum and the residue was purified by silica gel chromatog-
raphy, using a mixture of PE/EA to afford the desired
product 2.
[7] For some examples, see: a) J. P. Michael, Nat. Prod.
Rep. 1995, 12, 465; b) J. B. Hanuman, A. Katz, Nat.
Prod. Lett. 1993, 3, 227.
[8] For selected examples, see: a) M. A. Alonso, M. M.
Blanco, C. Avendano, J. C. Menendez, Heterocycles
1993, 36, 2315; b) X. Liu, X. Xin, D. Xiang, R. Zhang, S.
Kumar, F. Zhou, D. Dong, Org. Biomol. Chem. 2012,
10, 5643; c) B. Joseph, F. Darro, A. Behard, B. Lesur, F.
Collignon, C. Decaestecker, A. Frydman, G. Guillau-
met, R. J. Kiss, J. Med. Chem. 2002, 45, 2543; d) Y.
Zhang, Y. Fang, H. Liang, H. Wang, K. Hu, X. Liu, X.
Yi, Y. Peng, Bioorg. Med. Chem. Lett. 2013, 23, 107.
[9] For selected examples, see: a) C. Jia, D. Piao, T.
Kitamura, Y. Fujiwara, J. Org. Chem. 2000, 65, 7516;
b) R. Manikandan, M. Jeganmohan, Org. Lett. 2014, 16,
3568; c) D. V. Kadnikov, R. C. Larock, J. Org. Chem.
2004, 69, 6772.
Acknowledgements
We acknowledge the National Science Foundation of China
(#21472136), Tianjin Research Program of Application
Foundation and Advanced Technology (#15JCZDJC32900)
and the National Basic Research Project (#2014CB932201)
for financial support.
[10] P. J. Manley, M. T. Bilodeau, Org. Lett. 2004, 6, 2433.
[11] W.-P. Mai, J.-T. Wang, L.-R. Yang, Y.-M. Xiao, P. Mao,
L.-B. Qu, Org. Lett. 2014, 16, 204.
References
[1] For selected examples, see: a) P. M. Fresneda, P. Molina,
S. Delgado, Tetrahedron Lett. 1999, 40, 7275; b) W. E.
Campell, K. P. Finch, P. A. Bean, N. Finkelstein, Phy-
tochemistry 1987, 26, 33; c) J. He, U. Lion, I. Sattler,
F. A. Gollmick, S. Grabley, J. Cai, M. Meiners, H.
Schunke, K. Schaumann, U. Dechert, M. Krohn, J. Nat.
Prod. 2005, 68, 1397; d) J. Toum, A. Moquette, Y.
Lamotte, O. Mirguet, Tetrahedron Lett. 2012, 53, 1920.
[2] For selected examples, see: a) C. Peifer, R. Urich, V.
Schattel, M. Abadleh, M. Rottig, O. Kohlbacher, S.
Laufer, Bioorg. Med. Chem. Lett. 2008, 18, 1431; b) Z.
Zhao, W. H. Leister, R. G. Robinson, S. F. Barnett, D.
[12] X. Li, X. Li, N. Jiao, J. Am. Chem. Soc. 2015, 137, 9246.
[13] R. Zeng, G. Dong, J. Am. Chem. Soc. 2015, 137, 1408.
[14] For selected examples, see: a) J. R. Chen, X. Y. Yu, W. J.
Xiao, Synthesis 2015, 47, 604; b) H. Wang, L. N. Guo,
X. H. Duan, Chem. Commun. 2013, 49, 10370; c) Y. M.
Li, M. Sun, H. L. Wang, Q. P. Tian, S. D. Yang, Angew.
Chem. 2013, 125, 4064; Angew. Chem. Int. Ed. 2013, 52,
3972; d) T. Shen, Y. Z. Yuan, S. Song, N. Jiao, Chem.
Commun. 2014, 50, 4115; e) Y. M. Li, X. H. Wei, X. A.
Li, S. D. Yang, Chem. Commun. 2013, 49, 11701; f) G.
Jacquemot, M.-A. Mꢂnard, C. L’Homme, S. Canesi,
Chem. Sci. 2013, 4, 1287; g) J. Xie, P. Xu, H. Li, Q. Xue,
Adv. Synth. Catal. 2016, 358, 1–7
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asc.wiley-vch.de
H. Jin, Y. Cheng, C. Zhu, Chem. Commun. 2013, 49,
5672.
[15] D. Zhang, F. Gao, Y. Nian, Y. Zhou, H. Jiang, H. Liu,
Int. Ed. 2013, 52, 7156; c) P. Mizar, A. Laverny, M. EI-
Sherbini, U. Farid, M. Brown, F. Malmedy, T. Wirth,
Chem. Eur. J. 2014, 20, 9910.
1
2
3
4
5
6
7
8
9
Chem. Commun. 2015, 51, 7509.
[18] For selected examples, see: a) S. Jaegli, J. Dufour, H.-L.
Wei, T. Piou, X.-H. Duan, J.-P. Vors, L. Neuville, J. Zhu,
Org. Lett. 2010, 12, 4498; b) H.-L. Wei, T. Piou, J.
Dufour, L. Neuville, J. Zhu, Org. Lett. 2011, 13, 2244;
c) Y. Yang, X. Wu, S. Mao, J. Yu, L. Wang, Synlett 2014,
25, 1419.
[16] L. Liu, H. Lu, H. Wang, C. Yang, X. Zhang, D. Zhang-
Negrerie, Y. Du, K. Zhao, Org. Lett. 2013, 15, 2906.
[17] For selected examples, see: a) A. C. Boye, D. Meyer,
C. K. Ingison, A. N. French, T. Wirth, Org. Lett. 2003, 5,
2157; b) U. Farid, F. Malmedy, R. Claveau, L. Albers, T.
Wirth, Angew. Chem. 2013, 125, 7297; Angew. Chem.
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UPDATES
Metal-Free Synthesis of 3-Arylquinolin-2-ones from N,2-
Diaryl-acrylamides via Phenyliodine(III) Bis(2,2-dime-
thylpropanoate)-Mediated Direct Oxidative CÀC Bond
Formation
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Y. Cao, H. Zhao, D. Zhang-Negrerie, Y. Du*, K. Zhao*