Visible Light-Mediated Copper(I)-Catalysed Aerobic Oxidation of Ynamides/Ynamines at Room Temperature: A Sustainable Approach to the Synthesis of α-Ketoimides/α-Ketoamides

Article abstract of DOI:10.1002/adsc.201600925

A novel visible light-mediated, copper-catalysed aerobic oxidation of the C≡C bond in ynamides/ynamines at room temperature by using molecular oxygen as an oxidant is described. Overall, 23 examples were demonstrated with substrates having a wide range of functional groups. The current protocol can be readily scaled up to a preparative (1–2 g) scale with high yields (78–92%), high atom efficiency, and reaction mass efficiency. The mechanistic study shows that in-situ formation of a copper(I)-coordinated π-complex (λ_max=460 nm) is most probably the key light absorbing species responsible for the visible light-induced oxidation of ynamides and ynamines. This sustainable oxidation approach allows the direct synthesis of potentially important novel α-ketoimide/α-ketoamide skeletons without the need of external oxidants (organic/inorganic oxidants) and generation of stoichiometric amounts of wastes. (Figure presented.).

Full text of DOI:10.1002/adsc.201600925

COMMUNICATIONS
DOI: 10.1002/adsc.201600925
Visible Light-Mediated Copper(I)-Catalysed Aerobic Oxidation
of Ynamides/Ynamines at Room Temperature: A Sustainable
Approach to the Synthesis of a-Ketoimides/a-Ketoamides
a
a
a
Ayyakkannu Ragupathi, Vaibhav Pramod Charpe, Arunachalam Sagadevan,
and Kuo Chu Hwang *
a
a,
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, R.O.C.
Fax : (+886)-3571-1082; e-mail: kchwang@mx.nthu.edu.tw
Received: August 20, 2016; Revised: December 6, 2016; Published online: && &&, 0000
Supporting information for this article can be found under: http://dx.doi.org/10.1002/adsc.201600925.
Abstract: A novel visible light-mediated, copper-
catalysed aerobic oxidation of the CꢀC bond in
formations including cycloaddition and other reac-
tions, producing a diverse array of heterocyclic com-
[
5]
ynamides/ynamines at room temperature by using
molecular oxygen as an oxidant is described. Over-
all, 23 examples were demonstrated with substrates
having a wide range of functional groups. The cur-
rent protocol can be readily scaled up to a prepara-
tive (1–2 g) scale with high yields (78–92%), high
atom efficiency, and reaction mass efficiency. The
mechanistic study shows that in-situ formation of
a copper(I)-coordinated p-complex (lmax =460 nm)
is most probably the key light absorbing species re-
sponsible for the visible light-induced oxidation of
ynamides and ynamines. This sustainable oxidation
approach allows the direct synthesis of potentially
important novel a-ketoimide/a-ketoamide skeletons
without the need of external oxidants (organic/inor-
ganic oxidants) and generation of stoichiometric
amounts of wastes.
pounds. Consequently, oxidation of the CꢀC bond
of ynamides is receiving much attention and repre-
sents one of the most straightforward methods for
a direct access to potentially important synthons, such
[
6]
as, a-ketoimides. a-Ketoimides are structurally simi-
[
7]
lar to a-ketoamides and are important building
[
6]
blocks in organic synthesis. Their derivatives are
privileged precursors for diversified natural products
[
8]
of pharmacological importance. Conventionally, a-
ketoimides can be synthesized by direct amidation of
[
6b,9]
activated carbonyl groups.
But these methods
often require pre-synthesized carbonyl reagents. Only
very few examples have been reported for the oxida-
tion of ynamides by using a ruthenium or gold cata-
lyst in the presence of organic oxidants (up to
3.0 equivalents) at high temperatures for the prepara-
[
10]
tion of a-ketoimides. Despite the efficient oxidation
processes, common disadvantages have also been ob-
served, such as (i) usage of stoichiometric strong oxi-
dants (organic/inorganic oxidants), thus leading to the
generation of stoichiometric amounts of undesired
wastes, (ii) usage of expensive metal catalysts, and (iii)
typically the reactions are performed at high tempera-
tures.
Keywords: copper; molecular oxygen; oxidation;
photochemistry; radicals
Molecular oxygen-promoted oxidation of hydrocar-
Thus, it is highly desirable and challenging to devel-
bon and heteroatom-containing organic compounds op an environmentally benign and operationally
under mild conditions (room temperature) has recent- simple method for the preparation of novel a-keto-
ly emerged as an efficient and sustainable synthetic
approach for the construction of synthetically and bic oxidation of ynamides/ynamines by using the inex-
ACHTUNGTRENNUiGN mide/a-ketoamide skeleton through the direct aero-
[
1]
biologically potent molecules. In this regard, oxida- pensive simple CuCl salt as a catalyst without the
tion of CꢀC triple bonds is one of the unique oxida- need of external oxidants under low energy visible
[2]
tion process for the preparation of 1,2-diketone de- light irradiation, which would be of value in organic
rivatives, and thus many powerful transition metal- synthesis. From an ecological point of view, using mo-
[
3]
catalysed processes have been reported. Hetero- lecular oxygen as an oxidant represents one of the
[
1]
ACHTUNGTRENNUNGa tom-substituted alkynes, such as ynamides, are struc- most efficient and atom-economical transformations.
[4]
turally very special, and are involved in many trans- Visible light activated photoredox catalysis is being
Adv. Synth. Catal. 0000, 000, 0 – 0
1
ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
[
14]
accepted as a powerful and green alternative to acid such as Cu(I) upon photo irradiation. Howev-
[
11]
metal-catalysed thermal reactions.
Indeed, visible er, the same reaction does not occur under thermal
light is an environmentally friendly and sustainable conditions, even when heated to high tempera-
[
10a,12c]
source of energy for functional group transforma-
tions.
A
H
U
G
R
N
U
G
Photo-excitation can provide sufficient
[11d]
typically performed at room temperature in the ab- Cu(I) p-complex to overcome an energy barrier. Sub-
sence of ligands or additives. Moreover, visible light is sequent dark reaction with molecular oxygen can
easier to handle than high energy harmful UV light; form a copper peroxo complex and initiate the oxida-
reagents and products, including complex organic tion of the CꢀC bond of ynamides (see, details in the
molecules, are more stable under low energy visible mechanism discussion below).
light irradiation conditions. Inexpensive, photoredox
The significance of the present chemistry includes:
copper catalysis has been studied in various coupling (i) this is the first example that CuCl-catalysed oxida-
reactions, such as, C–C cross-coupling, and various C– tion of ynamides/ynamines to a-ketoimides and a-ke-
[
12]
N, C–S and C–O cross-coupling reactions. In con- toamides at room temperature; (ii) molecular oxygen
nection to copper photoredox catalysis, previously we (O ) was used as an oxidant, and (iii) a mechanistic
2
reported several examples of visible light-mediated investigation illustrates that in-situ formation of
CuCl-catalysed efficient C–C, C–N cross-coupling, a Cu(I)-coordinated p-complex might be the key cata-
[
13]
and C–H annulation reactions.
lyst responsible for the oxidation of ynamides/yn-
amines to a-ketoimides and a-ketoamides.
The oxidation reaction of ynamide (1a) was chosen
Herein, we report a novel and effective aerobic oxi-
dation of ynamides/ynamines for the prepration of a-
ACHTUNGTRENNUNG
ketoimides/a-ketoamides under the combination of as the model substrate for optimisation of the experi-
CuCl and low energy visible light irradiation mental parameters. In an initial study (see Table 1),
(
Scheme 1, current work). The current oxidation pro- we were delighted to find that oxidation the CꢀC
cess is unprecedented, and is complementary to our bond of ynamide (1a) in acetonitrile in the presence
previous work on oxidative C–N coupling of anilines of 5 mol% CuCl and molecular oxygen (1 atm) at
and terminal alkynes for the preparation of ketoam- room temperature under blue LEDs irradiation (10 h)
[13c]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
ides
because, in that work the highly electron-rich furnished the corresponding a-ketoimide in 93%
ynamine intermediates (highly unstable) cannot be yield (Table 1, entry 1). Different solvents were exam-
isolated. However, the current work deals with oxida- ined for oxidation of ynamide (1a). However, acetoni-
tion of the CꢀC triple bonds of yn
ACHTUNGERTNNUNGa mides as well as trile was found to be the best solvent, in which the
[
13c]
stable ynamines. Based on our previous work,
highest yield of 93% was obtained, whereas moderate
Cu(I) ion could coordinate to the CꢀC bond of yna- to low yields were obtained when using other solvents
mides to form a Cu(I) p-complex, which can further (see entries 4–7). Addition of 0.5 mL water to the re-
undergo reactions with O to generate the desired a- action mixture does not affect the product yield
2
ketoimides upon visible light irradiation. Importantly, (entry 8). In the catalytic screening, CuX (X=Cl, Br)
oxidation of the CꢀC bond of ynamides is much more affords the highest yield of the oxidation product.
[
4b,10b]
difficult than that of the CꢀC in ynamines,
since CuCl as catalyst could also produce the oxidation
2
ynamides have less p-basicity on the CꢀC triple bond product, but fails to give high yields (entry 3). Control
and thus favor the oxidation reaction using soft Lewis experiments reveal that exclusion of either light, Cu
catalyst, or O , results in no oxidation reaction (en-
2
tries 10–12).
Under the optimized conditions, (Table 1, entry 1),
we then explored the substrate scope of ynamides
containing various arylamine, alkynes and tosyl deriv-
atives (see Table 2). In the oxidation reaction, both
electron-rich, electron-neutral and electron-poor
group-substituted arylamines on the CꢀC bond of
ynamides underwent oxidation smoothly to afford the
corresponding a-ketoimide products (2a–2d and 2g–
2
h, 89 to 93% and 78–80% yields, respectively). Nota-
bly, the current oxidation reaction also works well for
halide-substituted arylamines in the ynamide moiety
(
X=Br and I), and affords their a-ketoimide products
with 82–85% yields (2e and f). Importantly, this halo-
substituted group in a-ketoimides is useful for further
[
15]
synthetic modifications.
Scheme 1. Transition metal-catalysed oxidation of ynamides.
Adv. Synth. Catal. 0000, 000, 0 – 0
2
ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
[a]
Table 1. Optimization of the reaction conditions.
83% yields) within a period of 15–17 h. Aliphatic
linear alkynes in the ynamides can also be readily oxi-
dized and converted to the a-ketoimide (2o) in 85%
yield without affecting the aliphatic chain. Finally, the
4-bromo-substituted tosyl group as well as 4-ester-sub-
stituted arylalkyne groups in the ynamide moieties
can readily undergo the oxidation reaction and afford
the a-ketoimide 2r in 83%. Thus, the ynamide oxida-
tion reaction works well for a wide range of function-
al groups, such as, alkoxy, halo, cyano, ester, and
naphthyl, and is a powerful method for for the synthe-
sis of a-ketoimides using O as oxidant.
2
After investigation of N-tosyl- and alkyne group-
substituted ynamides, the scope of carbazole-type yn-
amines was also explored for the same oxidation reac-
tion (see Table 3). We observed that carbazole-substi-
tuted ynamines can be easily converted into their cor-
responding a-ketoamides (4a–4e) with 82–89% yields
upon blue-LEDs irradiation in the presence of O and
2
5
mol% CuCl (see Table 3). Certainly, carbazole de-
rivatives are an important scaffold in natural products
and medicines.
[
16]
It is worthy to note that as com-
pared to N-tosyl group-substituted ynamides, carba-
zole-bearing ynamines readily undergo the oxidation
reaction within short periods of time (7–10 h). This is
due to the fact that CuCl could easily coordinate with
the CꢀC bond of ynamines. These results provide
a key piece of mechanistic evidence that the oxidation
reaction proceeds through a Cu(I)-coordinated p-
complex of the ynamides/ynamines. The structures of
[
a]
2
c and 2d were confirmed by single-crystal X-ray dif-
Unless otherwise mentioned, reaction conditions are as
follows; 1a (0.5 mmol), 5 mol% of [Cu] catalyst, solvent fraction.
[17]
(
(
7 mL). The mixture was irradiated with blue LEDs
power density: 40 mWcm at 460 nm) for 10 h in an O2 readily scaled up to a gram scale (1.0 g, 2.88 mmol,
In addition, the current oxidation process can be
À2
atmosphere (1 atm).
Yield of the isolated product.
0
Irradiation with an ambient white light bulb for 15 h
(
Reaction was conducted in the dark at 808C.
In the absence of CuCl catalyst.
In the absence of O2.
1
1
a) and produce 0.91 grams of 2a (84% yield) after
2 h of irradiation with blue LEDs at room tempera-
[
[
[
b]
c]
d]
.5 mL water was added.
ture in the presence of O (1 atm, see Scheme S1 in
2
À2
the Supporting Information). We have evaluated the
power density: 8 mWcm at 460 nm).
[
13e,18]
[
[
[
[
e]
f]
green chemistry metrics
for the synthesis of the
a-ketoimides (2a) in a preparative scale (see the Sup-
porting Information, Table S1). Overall, our green
process can enable the a-ketoimides (2a) with an E
factor of 8.3, 100% atom economy, 84% atom effi-
ciency, and 91% reaction mass efficiency, which are
g]
h]
1
atm. air (in a balloon) was used in the reaction.
Next, we further explored the substrate scope of far better than for previously reported Ru-catalysed
[
9a]
substituted tosyl groups and various alkynes. In most thermal processes (E factor=32.5, atom economy=
of the cases, substrates with substituted tosyl groups 68%, atom efficiency=62%, reaction mass efficien-
nicely participate in the oxidation reaction to gener- cy=36%, see, Table S2 in the Supporting Informa-
ate the a-ketoimides in 83–89% yields (Table 2, 2p– tion), since the current photochemical process does
2
r). The electron-rich phenylacetylene-substituted not require any organic strong oxidants and expensive
ynamides (1i, 2j and 1n) can also undergo similar oxi- metal catalysts, and thus is a sustainable and green
dation reaction to afford the corresponding a-keto- process for the synthesis of various a-ketoimides/a-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
imide products (2i, 2j and 2n) in good yields (86– ketoamides (on a large scale).
8%). Moreover, it was found that the current proto- With respect to the UV-visible absorption spectra,
col can well tolerate an electron-withdrawing phenyl- the experimental results, and our previous studies,
acetylene ring in the oxidation of ynamides to pro- a possible reaction mechanism for the visible light-ini-
duce their corresponding a-ketoimides (2k–2m, 80– tiated, CuCl-catalysed oxidation of ynamides is pro-
8
[13c,d]
ACHTUNGTRENNUNG
Adv. Synth. Catal. 0000, 000, 0 – 0
3
ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
[a]
Table 2. Scope of ynamides 1.
[
a]
Standard conditions; isolated yields after purification by column chromatography on silica gel.
posed in Scheme 2. The first step involves the forma- Figure 1). Furthermore, formation of this Cu(I)-coor-
tion of Cu(I)-coordinated p-complex of ynamide (A), dinated p-complex of ynamide was confirmed by the
[
13c,19]
which has an absorption band at 460 nm (see detection of heat release upon complexation using
isothermal titration calorimetry (ITC) measure-
[
20]
ments,
which gives an association constant of Ka
[a]
Table 3. Scope of carbozole-type ynamines 3.
À1
ꢁ
194M between Cu(I) and 4-methyl-N-phenyl-N-
(
phenylethynyl)benzenesulfonamide (1a) (see more
details in the Supporting Information, Figure S2).
[
a]
Standard conditions; isolated yields after purification by
column chromatography on silica gel.
Scheme 2. Proposed mechanism.
Adv. Synth. Catal. 0000, 000, 0 – 0
4
ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
in-situ formation of Cua (I)-coordinated p-complex
lmax =460 nm) is most probably the key light absorb-
(
ing species responsible for the visible light-induced
oxidation of ynamides and ynamines. From an envi-
ronmental point of view, using inexpensive simple
CuCl catalyst, molecular oxygen as oxidant, and reac-
tion under low energy visible-light irradiation, make
this process a greener alternative to existing thermal
methods for the oxidation of ynamides/ynamines. Fur-
ther investigation on visible light-mediated CuCl-cata-
lysed processes for oxidation of other internal al-
kynes/hydrocarbons, and detailed mechanistic elucida-
tion are currently ongoing in our laboratory.
Experimental Section
Figure 1. UV-visible absorption spectra of in-situ generated
General Procedure
light absorbing Cu(I)-ynamide complex (A) in CH CN.
3
To a dry test tube (20 mL) containing 5 mol% CuCl was
added the ynamide/ynamine (0.5 mmol) dry CH CN (7 mL)
3
Upon blue LED (lmax =460 nm) light irradiation,
photo-excited Cu(I)-p-complex (B) could readily
solution via a syringe. The suspension was irradiated with
À2
blue LED light (40 mWcm at 460 nm) at room tempera-
react with molecular oxygen to form a copper(II) ture in the presence of 1 atm oxygen until completion of the
[13c,21]
peroxo complex.
Isomerisation rearrangement of reaction (it was monitored by thin layer chromatography).
the resulting copper(II) peroxo complex (C) gener- The reaction mixture was diluted with 30% ethyl acetate in
[
13c,22]
hexane, and stirred for 10 min. The mixture was filtered
through celite and silica gel pads, and then washed with
ethyl acetate. The filtrate was concentrated and purified by
flash column chromatography on silica gel (using n-hexane
and ethyl acetate as eluent) to afford the desired a-keto-
ates the copper(I) species (D).
Finally, this com-
plex D can undergo transformation into the inter-
mediate (E), accompanied with regeneration of the
CuCl catalyst. Subsequent O–O bond cleavage of the
intermediate (E) will produce the desired a-keto-
AHCTUNGTERNNUNGi mide/a-ketoamide products.
[13c]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
imide (2a).
In the current proposed mechanism,
the Cu(I)-coordinated p-complex of the ynamide is
the light absorbing photocatalyst (lmax =460 nm) and
is complementary to our previous light absorbing pho- Acknowledgements
[
13]
tocatalyst, Cu(I)-acetylides (lmax =460–485 nm). To
prove the source of oxygen and gain more insight This work was supported by the Ministry of Science and
Technology, Taiwan.
about the reaction mechanism, we have performed an
18
O labelling experiment under the standard condi-
2
18
16
tions. 98% purity of O gas, instead of O air, was
2
2
References
filled in the reaction system. From the ESI mass, the
final product was determined to contain a mixture of
1
8
16
[1] For reviews on aerobic oxidative reactions, see: a) S. S.
Stahl, Angew. Chem. 2004, 116, 3480–3501; Angew.
Chem. Int. Ed. 2004, 43, 3400–3420; b) Z. Shi, C.
Zhang, C. Tang, N. Jiao, Chem. Soc. Rev. 2012, 41,
O and O products with a ratio of 87.5%:12.5%
see details in the Supporting Information). These re-
(
sults unambiguously indicate that the oxygen atoms in
the products mainly originate from the molecular
3
381–3430; c) A. N. Campbell, S. S. Stahl, Acc. Chem.
16
oxygen. The 12.5% O-containing product is most
Res. 2012, 45, 851–863; d) S. D. McCann, S. S. Stahl,
Acc. Chem. Res. 2015, 48, 1756–1766.
1
8
16
probably formed via a partial O-H O exchange
2
[
23]
during the silica gel column purification process.
[2] a) F. Chen, T. Wang, N. Jiao, Chem. Rev. 2014, 114,
8
4
613–8661; b) T. Wang, N. Jiao, Acc. Chem. Res. 2014,
7, 1137–1145; c) N. J. Turro, V. Ramamurthy, K.-C.
In summary, we have successfully developed
a novel process using visible light-mediated molecular
oxygen-promoted oxidation of ynamides/ynamines
using simple CuCl as a catalyst for the preparation of
a-ketoimides/a-ketoamides at room temperature
without the need for strong organic oxidants. The cur-
rent method can be readily scaled up to a preparative
Liu, A. Krebs, R. Kemper, J. Am. Chem. Soc. 1976, 98,
758–6761; d) M. Sasaki, M. Ando, M. Kawahata, K.
6
Yamaguchi, K. Takeda, Org. Lett. 2016, 18, 1598–1601.
3] a) R. Chinchilla, C. Nꢁjera, Chem. Rev. 2014, 114,
[
1
783–1826; b) S. Chen, Z. Liu, E. Shi, L. Chen, W. Wei,
H. Li, Y. Cheng, X. Wan, Org. Lett. 2011, 13, 2274–
2277; c) W. Ren, Y. Xia, S.-J. Ji, Y. Zhang, X. Wan, J.
Zhao, Org. Lett. 2009, 11, 1841–1844; metal-free proce-
(
1–2 g) scale with high atom efficiency, and reaction
mass efficiency. A mechanistic study illustrates that
Adv. Synth. Catal. 0000, 000, 0 – 0
5
ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
dure: d) X. Liu, T. Cong, P. Liu, P. Sun, J. Org. Chem.
016, DOI: 10.1021/acs.joc.6b00097.
4] a) X.-N. Wang, H.-S. Yeom, L.-C. Fang, S. He, Z.-X.
[12] Copper-photoredox catalyst, see: a) M. Pirtsch, S.
Paria, T. Matsuno, H. Isobe, O. Reiser, Chem. Eur. J.
2012, 18, 7336–7340; b) S. Paria, O. Reiser, Chem-
CatChem 2014, 6, 2477–2483; c) A. Baralle, L. Fenster-
bank, J.-P. Goddard, C. Ollivier, Chem. Eur. J. 2013, 19,
10809–10813; d) A. C. Hernandez-Perez, S. K. Collins,
Angew. Chem. 2013, 125, 12928–12932; Angew. Chem.
Int. Ed. 2013, 52, 12696–12700; e) S. E. Creutz, K. J.
Lotito, G. C. Fu, J. C. Peters, Science. 2012, 338, 647–
2
[
Ma, B. L. Kedrowski, R. P. Hsung, Acc. Chem. Res.
2
014, 47, 560–578; 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) G. Evano, A.
Coste, K. Jouvin, Angew. Chem. 2010, 122, 2902–2921;
Angew. Chem. Int. Ed. 2010, 49, 2840–2859.
[
5] a) A. Mukherjee, R. B. Dateer, R. Chaudhuri, S.
6
51.
13] a) A. Sagadevan, K. C. Hwang, Adv. Synth. Catal. 2012,
54, 3421–3427; b) A. Sagadevan, A. Ragupathi, K. C.
Hwang, Photochem. Photobiol. Sci. 2013, 12, 2110–
118; c) A. Sagadevan, A. Ragupathi, C.-C. Lin, J. R.
Bhunia, S. N. Karad, R.-S. Liu, J. Am. Chem. Soc. 2011,
[
1
33, 15372–15375; b) S. A. Gawade, D. B. Huple, R.-S.
3
Liu, J. Am. Chem. Soc. 2014, 136, 2978–2981; c) A. Si-
va Reddy, A. L. Siva Kumari, S. Saha, K. C. Kumar-
a Swamy, Adv. Synth. Catal. 2016, 358, 1625–1638; d) C.
Shu, Y.-H. Wang, C.-H. Shen, P.-P. Ruan, X. Lu, L.-W.
Ye, Org. Lett. 2016, 18, 3254–3257; e) S. N. Karad, R.-S.
Liu, Angew. Chem. 2014, 126, 9218–9222; Angew.
Chem. Int. Ed. 2014, 53, 9072–9076; f) J. Zhang, Q.
Zhang, B. Xia, J. Wu, X.-N. Wang, J. Chang, Org. Lett.
2
Hwu, K. C. Hwang, Green Chem. 2015, 17, 1113–1119;
d) A. Sagadevan, A. Ragupathi, K. C. Hwang, Angew.
Chem. 2015, 127, 14102–14107; Angew. Chem. Int. Ed.
2
015, 54, 13896–13901; e) A. Sagadevan, P. C. Lyu,
K. C. Hwang, Green Chem. 2016, 18, 4526–4530; f) A.
Ragupathi, A. Sagadevan, C.-C. Lin, J. R. Hwu, K. C.
Hwang, Chem. Commun. 2016, 52, 11756–11759; g) A.
Sagadevan, V. P. Charpe, K. C. Hwang, Catal. Sci. Tech-
nol. 2016, 6, 7688–7692.
2
016, 18, 3390–3393.
[
6] a) S. M. Kim, I. S. Byun, Y. H. Kim, Angew. Chem.
2
7
000, 112, 744–747; Angew. Chem. Int. Ed. 2000, 39,
28–731; b) J.-H. Chen, U. Venkatesham, L.-C. Lee, K.
[
[
[
14] R. Chinchilla, C. Najera, Chem. Soc. Rev. 2011, 40,
Chen, Tetrahedron. 2006, 62, 887–893; c) S. W. Young,
Y. H. Kim, J.-W. Hwang, Y. Do, Chem. Commun. 2001,
5
084–5121.
15] M. Gholami, R. R. Tykwinski, Chem. Rev. 2006, 106,
997–5027.
9
96–997; d) M. Kosior, M. Asztemborska, J. Jurczak,
4
Synthesis. 2004, 87–91; e) L. Yang, D.-X. Wang, Z.-T.
Huang, M.-X. Wang, J. Am. Chem. Soc. 2009, 131,
16] a) C. Schuster, K. K. Julich-Gruner, H. Schnitzler, R.
Hesse, A. Jꢂger, A. W. Schmidt, H.-J. Knçlker, J. Org.
Chem. 2015, 80, 5666–5673; b) A. W. Schmidt, K. R.
Reddy, H.-J. Knçlker, Chem. Rev. 2012, 112, 3193–
1
0390–10391; f) S. R. Ram, A. R. Devi, D. S. Iyengar,
Chem. Lett. 2002, 7, 718–719.
[
7] a) C. De Risi, G. P. Pollini, V. Zanirato, Chem. Rev.
3
328.
2
016, 116, 3241–3305; b) D. Kumar, S. R. Vemula, G. R.
[
17] CCDC 1495656 (2c) and CCDC 1495655 (2d) contain
the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The
Cook, ACS Catal. 2016, 6, 4920–4945.
[
8] a) C. K. Wada, R. R. Frey, Z. Ji, M. L. Curtin, R. B.
Garland, J. H. Holms, J. Li, L. J. Pease, J. Guo, K. B.
Glaser, P. A. Marcotte, P. L. Richardson, S. S. Murphy,
J. J. Bouska, P. Tapang, T. J. Magoc, D. H. Albert, S. K.
Davidsen, M. R. Michaelides, Bioorg. Med. Chem. Lett.
Cambridge
Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. See also the Sup-
porting Information.
2
003, 13, 3331–3335; b) M. R. Angelastro, S. Mehdi,
[18] R. Turgis, I. Billault, S. Acherar, J. Augꢃ, M.-C. Scherr-
mann, Green Chem. 2013, 15, 1016–1029.
J. P. Burkhart, N. P. Peet, P. Bey, J. Med. Chem. 1990,
3
3, 11–13; c) T. D. Ocain, D. H. Rich, J. Med. Chem.
[19] a) Z. Chen, W. Zeng, H. Jiang, L. Liu, Org. Lett. 2012,
14, 5385–5387; b) J. Li, L. Neuville, Org. Lett. 2013, 15,
1752–1755; c) S.-U. Kim, Y. Liu, K. M. Nash, J. L.
Zweier, A. Rockenbauer, F. A. Villamena, J. Am.
Chem. Soc. 2010, 132, 17157–17173.
1
992, 35, 451–456.
[
9] a) E. Valeur, M. Bradley, Chem. Soc. Rev. 2009, 38,
6
06–631; I -catalysed method, see: b) X. Wu, Q. Gao, S.
2
Liu, A. Wu, Org. Lett. 2014, 16, 2888–2891.
[
10] a) Z. F. Al-Rashid, W. L. Johnson, R. P. Hsung, Y. Wei,
[
20] S. Leavitt, E. Freire, Curr Opin Struct Biol. 2001, 5,
60–566.
21] a) C. Zhang, N. Jiao, Angew. Chem. 2010, 122, 6310–
313; Angew. Chem. Int. Ed. 2010, 49, 6174–6177;
P.-Y. Yao, R. Liu, K. Zhao, J. Org. Chem. 2008, 73,
5
8
780–8784; b) C.-F. Xu, M. Xu, Y.-X. Jia, C.-Y. Li, Org.
[
Lett. 2011, 13, 1556–1559; metal-free procedure, see:
c) T. Chikugo, Y. Yauchi, M. Ide, T. Iwasawa, Tetrahe-
dron. 2014, 70, 3988–3993; using DMDO as oxidant,
see: d) Z. F. Al-Rashid, R. P. Hsung, Org. Lett. 2008,
6
b) K. K. Toh, Y.-F. Wang, E. P. J. Ng, S. Chiba, J. Am.
Chem. Soc. 2011, 133, 13942–13945; c) S. E. Allen,
R. R. Walvoord, R. Padilla-Salinas, M. C. Kozlowski,
Chem. Rev. 2013, 113, 6234–6458.
1
0, 661–663.
[
11] For light-induced photoredox catalysts, see: a) C. K.
[
[
22] H. Wang, Y. Wang, D. Liang, L. Liu, J. Zhang, Q. Zhu,
Angew. Chem. 2011, 123, 5796–5799; Angew. Chem.
Int. Ed. 2011, 50, 5678–5681.
Prier, D. A. Rankic, D. W. C. MacMillan, Chem.Rev.
2
013, 113, 5322; b) M. Reckenthꢂler, A. G. Griesbeck,
Adv. Synth. Catal. 2013, 355, 2727–2744; c) J. M. R.
Narayanam, C. R. J. Stephenson, Chem. Soc. Rev. 2011,
23] C. Zhang, Z. Xu, L. Zhang, N. Jiao, Angew. Chem.
2
5
011, 123, 11284–11288; Angew. Chem. Int. Ed. 2011,
0, 11088-11092.
4
0, 102–113; d) P. Y. Tehshik, A. I. Michael, D. Juana,
Nat. Chem. 2010, 2, 527–532.
Adv. Synth. Catal. 0000, 000, 0 – 0
6
ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
Visible Light-Mediated Copper(I)-Catalysed Aerobic
Oxidation of Ynamides/Ynamines at Room Temperature: A
Sustainable Approach to the Synthesis of a-Ketoimides/a-
Ketoamides
7
Adv. Synth. Catal. 2017, 359, 1 – 7
Ayyakkannu Ragupathi, Vaibhav Pramod Charpe,
Arunachalam Sagadevan, Kuo Chu Hwang*
Adv. Synth. Catal. 0000, 000, 0 – 0
7
ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!