Catalyst-Free and Transition-Metal-Free Approach to 1,2-Diketones via Aerobic Alkyne Oxidation

Article abstract of DOI:10.1021/acs.joc.0c03010

A catalyst-free and transition-metal-free method for the synthesis of 1,2-diketones from aerobic alkyne oxidation was reported. The oxidation of various internal alkynes, especially more challenging aryl-alkyl acetylenes, proceeded smoothly with inexpensive, easily handled, and commercially available potassium persulfate and an ambient air balloon, achieving the corresponding 1,2-diketones with up to 85% yields. Meanwhile, mechanistic studies indicated a radical process, and the two oxygen atoms in the 1,2-diketons were most likely from persulfate salts and molecular oxygen, respectively, rather than water.

Full text of DOI:10.1021/acs.joc.0c03010

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Note
Catalyst-Free and Transition-Metal-Free Approach to 1,2-Diketones
via Aerobic Alkyne Oxidation
Duyi Shen,* Hongyan Wang, Yanan Zheng, Xinjing Zhu, Peiwei Gong, Bin Wang, Jinmao You,
Yulei Zhao,* and Mianran Chao*
Cite This: J. Org. Chem. 2021, 86, 5354−5361
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sı Supporting Information
ABSTRACT: A catalyst-free and transition-metal-free method for the
synthesis of 1,2-diketones from aerobic alkyne oxidation was reported.
The oxidation of various internal alkynes, especially more challenging
aryl-alkyl acetylenes, proceeded smoothly with inexpensive, easily
handled, and commercially available potassium persulfate and an
ambient air balloon, achieving the corresponding 1,2-diketones with
up to 85% yields. Meanwhile, mechanistic studies indicated a radical
process, and the two oxygen atoms in the 1,2-diketons were most likely
from persulfate salts and molecular oxygen, respectively, rather than
water.
ound in many natural products and bioactive molecules,
1,2-diketones are important building blocks in versatile
internal alkynes to afford 1,2-diketones. Besides, the origin of
oxygen in 1,2-diketones was not declared in those systems.
F
organic transformations for value-added pharmaceuticals and
The peroxydisulfate salts, like potassium persulfate (K
and less commonly used Na and (NH
emerged as cheap, stable, easily handled, and readily available
2 2 8
S O )
) S O , had
4 2 2 8
1
functional materials. To obtain 1,2-diketones, the most
2
S
2
O
8
straightforward strategy is the direct oxidation of alkynes
which are readily available and easily obtained by Sonogashira
11
powerful oxidants. Previous research had disclosed that, by
the aid of heat, irradiation, or transition metals, the
2
coupling. During the past decade, one of the main choices for
2
−
peroxydisulfate anion (S O ) could be converted into the
oxidizing alkynes to 1,2-diketones was transition-metal
catalysis (Scheme 1). Generally, various transition-metal-
based catalysts (especially noble metals), such as Pd, Ru, Au,
Ag, and Cu in combination with an oxygen source like DMSO,
were employed but limited to narrow substrate scopes or
2
8
•
−
12
sulfate radical anion (SO4 ), which was even more reactive
1
3
to cover a wide range of substances.
Hence, the
peroxydisulfate salts were frequently employed, for instance,
in the oxidation of transition metals, CH bonds, CC
•
−
3
bonds, heteroatoms, and aromatic rings. In these SO
-
4
higher reaction temperature. In recent years, photocatalytic
mediated oxidations, the single-electron-transfer (SET) or
hydrogen-atom-transfer (HAT) mechanisms were generally
oxidation of alkynes to 1,2-diketones using organic photo-
catalysts has also attracted much attention, since they are run
11
4
accepted. In addition, Wille had already proposed that in
in mild conditions with dioxygen or air as the oxidant. In
•
−
alkyne oxidation SO4 could also serve as an oxygen-atom-
selected reports, however, higher catalyst loading, stoichio-
metric additives, or longer reaction time is still needed to
achieve good conversions. Very recently, Dai and Xu also
presented sustainable access to 1,2-diketones via electro-
chemical oxidation of internal alkynes while the reaction
1
4
•−
transfer (OAT) reagent. The SO4 was added to CC
triple bonds to donate one oxygen atom and provide a
carbonyl group, which resembles the behavior of NO .
•
3
Meanwhile, the latter radical was reported to be responsible
15
5
for the alkyne oxidation to produce 1,2-diketones. Compared
mechanisms were not scrutinized. Even though great advances
•
•−
with the NO , however, the OAT ability of SO in synthetic
3
4
were achieved in all of the above examples, facile and efficient
approaches of 1,2-diketones from alkyne oxidation were still
highly desirable in academia as well as the chemical industry.
In recent times, the concept of “catalyst-free organic
applications was less studied, and such a synthesis strategy for
,2-diketones by alkyne oxidation only with peroxydisulfate
1
6
Received: December 23, 2020
Published: March 25, 2021
synthesis”, aiming at organic transformation without any
catalysts or sacrificial reagents, has emerged and is appealing
because it met the expectations of simple, cost-effective, and
sustainable chemical processes. In fact, classic strong but not
7
8
9
very preferred oxidants, such as KMnO , OsO , Hg(NO ) ,
4
4
3 2
10
and organic peracids, were themselves capable of oxidizing
©
2021 American Chemical Society
https://doi.org/10.1021/acs.joc.0c03010
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Note
Scheme 1. Synthesis of 1,2-Diketones from Alkyne Oxidation
salts but without any catalysts or additives has not been
reported yet.
significant role, and MeCN was shown to be better than other
common organic solvents (Table 1, entries 7−10). Besides,
Herein, we described the synthesis of a variety of 1,2-diketo
compounds from internal alkynes, including diaryl- and aryl-
alkyl acetylenes, by the combination of a suitable inorganic
oxidant, K S O , and preferred ambient air in the absence of
after modifying the volume ratio of MeCN−H O to 2:1, the
2
highest yield of 2a (benzil) could be obtained as 85% (for
more screening data, please see Table S1).
With the optimized condition in hand, first, various diaryl
acetylenes which possessed one and two substituents on the
benzene rings were examined. As shown in Figure 1, moderate
to good yields of 1,2-diketones were achieved generally.
Overall, wherever the positions of the substituents were, the
electron-donating groups like methyl, tert-butyl, phenyl, and
methoxyl just delivered 1,2-diketones in moderate yields while
the electron-withdrawing groups were beneficial to afford
products with higher yields. This phenomenon could probably
be explained by the fact that electron-withdrawing groups
would contribute to stabilize the possible radical intermediate,
thus resulting in better yields. In addition, by comparing the
results of the same substituents but at different positions, such
as para-Cl and meta-Cl, the former one tended to provide a
slightly higher yield which was consistent with the Hammett
constant. Besides, the chemoselectivity between CC and
other labile groups was also studied. The reaction exhibited
certain selectivity of alkyne over the CH bond. However, the
aldehyde was not well-tolerated, and the desired product was
obtained with very low yield (Figure 1, 2y and 2z).
In contrast to diaryl acetylenes, the oxidation of other
alkynes, such as monoaryl alkynes, was somewhat more
difficult and therefore less focused. In order to further expand
the reaction scope, we subsequently chose aryl-alkyl acetylenes
as the substrates. To our delight, alkynes with aliphatic chain
lengths ranging from 3 to 8 were all highly converted under
standard conditions. In addition, the corresponding 1,2-
diketones were isolated in moderate to good yields in general
(Figure 1, 2aa−2ff).
2
2
8
any catalysts or transition-metals. Also, control experiments,
1
8
especially the O-isotope labeling experiments, unveiled the
possible reaction mechanism and sources of oxygen atoms in
the 1,2-diketone products.
At the beginning, we chose 1a (tolane) as the model
substrate and the commonly used K S O as the oxidant. To
2
2
8
our delight, the oxidation performed well with 2 equiv of
K S O and an air balloon in a MeCN−H O mixture, yielding
2
2
8
2
7
2% 2a (benzil) (Table 1, entry 1). Moreover, other
a
Table 1. Optimization of Reaction Conditions
entry
oxidant
K S O
T (°C)
solvent (v/v)
yield (%)
1
2
3
4
5
6
7
8
9
60
60
60
60
50
70
60
60
60
60
60
60
60
MeCN/H O (1/1)
72
67
69
20
36
47
35
15
19
<5
37
85
78
2
2
8
2
Na S O
MeCN/H O (1/1)
2
2
8
2
(NH ) S O
MeCN/H O (1/1)
4
2
2
8
2
Oxone
MeCN/H O (1/1)
2
K S O
MeCN/H O (1/1)
2
2
8
2
K S O
MeCN/H O (1/1)
2
2
8
8
8
8
8
8
8
8
2
K S O
tBuOH/H O (1/1)
2
2
2
K S O
DMF/H O (1/1)
2
2
2
K S O
TFE/H O (1/1)
2
2
2
10
11
12
13
K S O
EtOAc/H O (1/1)
2
2
2
K S O
MeCN/H O (1/2)
2
2
2
K S O
MeCN/H O (2/1)
2
2
2
To gain more insights into this reaction, several mechanistic
studies were conducted. Conventionally, 2 equiv of 2,2,6,6-
tetramethyl-1-piperidinyloxyl (TEMPO), a radical scavenger,
was added into the model reaction under standard conditions.
Not surprisingly, substrate 1a was recovered by 91%, and no
targeted product 2a was detected, indicating a radical process
(eq 1). Next, the possible role of dioxygen was probed since
the standard reaction ran in the presence of air. A strict
degassed procedure was performed by the “freeze−pump−
K S O
MeCN/H O (3/1)
2
2
2
a
Reaction conditions: 1a (0.1 mmol), persulfate salts (2 equiv, 0.2
mmol), and solvents in a glass test tube equipped with an air balloon
were stirred in an oil bath for 8 h.
commercially available persulfate salts, like Na S O ,
2
2
8
(
NH ) S O , and Oxone were also screened while all exhibited
4 2 2 8
lower yields than K S O (Table 1, entries 2−4). It was said
that K S O undergoes O−O fission to form SO
higher than 50 °C; thus, the reaction temperature was tested,
and 60 °C was demonstrated to be the optimal one (Table 1,
entries 5 and 6). Accordingly, the even higher temperature,
greater oxidant loadings, or longer reaction time would all lead
to further degradation of the 1,2-diketone, perhaps via a BV-
2
2
8
•
−
18
when
thaw” methods to remove any dioxygen in the system.
2
2
8
4
1
6
However, in this time 81% of the substrate 1a was recovered
while no desired product 2a was observed, which suggested the
incorporation of dioxygen into 1,2-diketones (eq 2). Also,
neither 1,2-diphenylethan-1-one was found in this case,
implying that the alkyne hydration−oxidation pathway could
1
7
19
like oxidation. In addition, the reaction solvents played a
also be excluded in this system.
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Note
Figure 1. Scope of diaryl acetylenes (1b−1z) and aryl-alkyl acetylenes (1aa−1ff). (footnote a) Reaction conditions: alkynes (0.1 mmol), K S O (2
2
2
8
equiv, 0.2 mmol), and MeCN−H O in a glass test tube equipped with an air balloon were stirred in an oil bath under 60 °C for 8 h.
2
1
8
Moreover, O-isotope labeling experiments were carried out
to explore the sources of oxygen in the 1,2-diketone products
since both O and H O were present in the reaction. It was
h to reduce the oxygen atom exchange. Subsequently, only a
small proportion of mono- O-labeled 2a could be seen in the
1
8
blank experiment after 2 h (eq 3; Figure S2). When the model
2
2
1
8
widely accepted that ketones were able to exchange the oxygen
atom with that of H O under certain conditions. Expectedly,
when 1,2-ketone 2a was used as the substrate and H2 O rather
reaction proceeded in the presence of air and H O,
2
20
18
surprisingly, the product ratio of non- O-labeled and
2
1
8
18
mono- O-labeled 2a was similar to that in the above blank
than H O as the cosolvent, a large abundance of both
experiment (eq 4; Figure S3), showing that the oxygens in 1,2-
2
1
8
18
mono- O-labeled and bi- O-labeled 2a could be obviously
observed in the mass spectra after 8 h (Figure S1). Therefore,
the following isotope labeling reactions were only limited to 2
diketone were not likely from the solvent H O. Then, the
2
1
8
model reaction was conducted under an O atmosphere;
2
1
8
however, mono- O-labeled 2a could be clearly found as the
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Note
Scheme 2. Proposed Mechanism
1
8
the internal reference, and 13C NMR spectra were recorded with
major peak (eq 5; Figure S4). Next, when both O and
2
1
8
18
CDCl (δ = 77.00) as the internal reference. Mass spectra were
H2 O were applied, similarly, the abundance of mono- O-
labeled 2a was still the highest in this case (eq 6; Figure S5).
With these isotope labeling data taken into consideration, it
seemed that one of the oxygen atoms in the 1,2-diketone was
3
obtained using an Agilent 7890/7000D GC-MS instrument (EI, 70
eV) and an Agilent G6460A LC-MS instrument (ESI). The alkyne
substrates were prepared with high purity and yield, using the
corresponding terminal alkynes and iodoarenes by the well-known
Sonogashira coupling according to literature methods, and the
2−
mainly from S O , while the other one was from molecular
2
8
oxygen instead of H O in this system.
4c,21
18
18
2
structures were confirmed.
H2 O (97 atom % O) was
1
8
On the basis of previous reports and the above control
experiments, a plausible reaction mechanism was proposed. As
shown in Scheme 2, the K S O was initially decomposed into
purchased from Shanghai Macklin Biochemical Co. Ltd., while O2
1
8
(98 atom % O) was bought from Guangzhou Yigas Gases Co. Ltd.
The other compounds and solvents were purchased from Shanghai
Taitan technology Co. Ltd. Commercially available reagents were
used as received unless otherwise specified.
2
2
8
•
−
persulfate radial anion SO by heating, and the addition of
4
this SO4• to the alkyne formed a vinyl radical A which was
−
•
15
Typical Experimental Procedure for Aerobic Alkyne
Oxidation. Alkynes (0.1 mmol), K S O (0.2 mmol, 54 mg), and
2 2 8
similar to the case of NO . Then, the vinyl radical A was
3
•−
quickly captured by dioxygen, rather than another SO4 , to
generate a superoxo radical species B. Next, the cleavage of the
OS bond occurred to deliver intermediate C, while a much
CH CN/H O (1.5 mL, v/v = 2:1) were added to an oven-dried test
3
2
tube equipped with a magnetic stirring bar. Then, the reaction tube
was sealed with an air balloon (atmospheric pressure) and stirred in
an oil bath at the desired temperature for the corresponding time.
After the reaction was completed, the reaction solution was extracted
by EtOAc (3 × 3 mL). The organic solvent was removed in vacuo, and
the residue was purified by flash column chromatography (petroleum
ether/EtOAc, v/v = 50:1) on silica gel to give 1,2-diketones as a
yellowish solid or oil.
•
−
15a
less reactive SO
left as a leaving group simultaneously.
3
Finally, the intermediate C was probably attacked by another
dioxygen or underwent molecular cyclization to provide 1,2-
diketone product 2a. On the other hand, in the absence of
2−
•−
dioxygen, vinyl radical A would interact with S O , SO4 , or
2
8
solvent to give minor undefined byproducts. At the same time,
it must be noted that the radical addition of SO4• to both
CC and the following vinyl radical A should be slower;
otherwise, the alkyne would not be recovered at high yield in
the absence of air (eq 2).
Experimental Procedure for Oxidation with H
18O. The
−
2
procedure was similar to the typical procedure and just replaced the
18
2
cosolvent H O with H O. After the desired reaction time, the
2
mixture was extracted by EtOAc (3 × 2 mL) and dried with
anhydrous Na SO . Finally, the filtrate was then injected into GC-MS
2
4
In summary, we developed a catalyst-free and transition-
metal-free protocol for the preparation of 1,2-diketones by the
oxidation of diaryl- and aryl-alkyl internal alkynes employing
commercially available K S O and ambient air. Meanwhile, on
for mass analysis.
Experimental Procedure for Oxidation without Air. 1a (0.1
mmol) and K (0.2 mmol, 54 mg) were added to a clean and
dried sealed Schlenk tube equipped with a stir bar. CH CN/H O (1.5
S O
2 2 8
3
2
2
2
8
18
mL, v/v = 2:1) was injected into the tube through a syringe. Then, the
Schlenk tube was put into a prepared Dewar flask with an appropriate
amount of liquid nitrogen. After the reaction solution was completely
frozen, the air in the reaction system was discharged by using a
vacuum pump. About 2 min later, the Schlenk tube was allowed to
warm to room temperature after removal from the liquid nitrogen.
This was repeated two more times for a total of three freeze−pump−
the basis of radical interrupting and O-isotope labeling
experiments, the alkynes seemed to go through a radical
process triggered by the radical addition of SO4• and the
−
following capture of O in the air to produce 1,2-diketones in
2
which the two oxygen atoms were provided by K S O and O ,
2
2
8
2
respectively. More detailed mechanistic investigations were still
ongoing in our lab. This method not only avoided the usage of
either additives or the production of considerable transition
metal or organic wastes but also offered a suitable choice of
making 1,2-diketones from easily accessed alkynes with
sustainable oxygen sources.
thaw cycles. Finally, the tube was charged with N . After the reaction
2
ran for the desired time, the reaction solution was extracted by EtOAc
(3 × 3 mL). The organic solvent was removed in vacuo, and the
residue was purified by flash column chromatography (petroleum
ether/EtOAc, v/v = 50:1) on silica gel to recover the starting material.
Experimental Procedure for Oxidation with 1 O . Following
8
2
the procedure of the freeze−pump−thaw described above, the
EXPERIMENTAL SECTION
18
■
Schlenk tube was filled with
O instead. Then, after the desired
2
General Methods. All reactions under standard conditions were
carried out in glass test tubes (1.5 cm × 10 cm) equipped with an air
reaction time, the reaction mixture was extracted by EtOAc (3 × 2
mL) and dried with anhydrous Na SO . Finally, the filtrate was
injected into GC-MS for mass analysis.
Procedure for the Oxidation of 1a on a Larger Scale.
Diphenylacetylene (1a, 1 mmol), K (2 mmol, 540 mg), and
CH CN/H O (15 mL, v/v = 2:1) were added to a 50 mL round-
2
4
1
8
balloon (atmospheric pressure). O-isotope labeling experiments
were run in Schlenk tubes (2 cm × 10 cm). Anhydrous acetonitrile
was prepared by distillation from CaH . Reactions were monitored by
thin layer chromatography (TLC) using UV light to visualize the
S O
2 2 8
2
3
2
course of reaction. Purification of reaction products was carried out by
bottom flask equipped with a magnetic stirring bar and condenser.
Then, the flask was charged with an air balloon (atmospheric
pressure) and stirred in an oil bath at 60 °C for 8 h. Then, the
reaction solution was extracted by EtOAc. The organic solvent was
removed in vacuo, and the residue was purified by flash column
1
flash chromatography on silica gel (300−400 mesh). H NMR spectra
1
3
were recorded with a Bruker 500 MHz instrument; C NMR spectra
were recorded at 126 MHz and in CDCl (containing 0.03% TMS)
3
1
solutions. H NMR spectra were recorded with Me Si (δ = 0.00) as
4
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Note
1
chromatography (petroleum ether/EtOAc, v/v = 50:1) on silica gel to
2H). 13C{ H} NMR (126 MHz, chloroform-d): δ 193.5, 193.1, 136.0
give 1,2-diketones (2a) as a yellowish solid (103 mg, 49%).
Benzil (2a): Purification by column chromatography (EtOAc/
petroleum ether, v/v = 1:50). Yellow solid (17.2 mg, 85% yield). H
(C−F, 2J
= 32.8 Hz), 135.6, 135.3, 132.6, 130.3, 130.0, 129.2,
C−F
4a
126.1 (C−F, 3J
= 3.8 Hz), 123.3 (C−F, 1J
= 273.4 Hz). GC-
C−F
C−F
1
+
+
MS (EI, 70 eV) m/z: 201.1 ([M − Ph] ), 173.2 ([M − PhCO] ).
1,2-Di-p-tolylethane-1,2-dione (2j): Purification by column chro-
matography (EtOAc/petroleum ether, v/v = 1:50). Yellow solid (14.5
mg, 61% yield). H NMR (500 MHz, chloroform-d): δ 7.86 (d, J =
8.1 Hz, 4H), 7.30 (d, J = 8.0 Hz, 4H), 2.43 (s, 6H). C{ H} NMR
(126 MHz, chloroform-d): δ 194.5, 146.1, 130.7, 130.0, 129.7, 21.9.
GC-MS (EI, 70 eV) m/z: 238.2 ([M] ).
15c
NMR (500 MHz, chloroform-d): δ 7.97 (dd, J = 8.3, 1.4 Hz, 4H),
1
3
1
7
.65 (td, J = 7.3, 1.4 Hz, 2H), 7.51 (t, J = 7.8 Hz, 4H). C{ H} NMR
1
(
126 MHz, chloroform-d): δ 194.6, 134.9, 133.0, 129.9, 129.0. GC-
+
13
1
MS (EI, 70 eV) m/z: 210.2 ([M] ).
-Phenyl-2-(p-tolyl)ethane-1,2-dione (2b): Purification by column
chromatography (EtOAc/petroleum ether, v/v = 1:50). Yellow solid
4a
1
+
1
22
(15.6 mg, 70% yield). H NMR (500 MHz, chloroform-d): δ 7.97 (d,
1,2-Bis(4-(tert-butyl)phenyl)ethane-1,2-dione (2k): Purification by
J = 7.7 Hz, 2H), 7.87 (d, J = 7.9 Hz, 2H), 7.65 (t, J = 7.4 Hz, 1H),
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
1
7
.50 (t, J = 7.6 Hz, 2H), 7.31 (d, J = 7.8 Hz, 2H), 2.44 (s, 3H).
C{ H} NMR (126 MHz, chloroform-d): δ 194.8, 194.3, 146.2,
Yellow solid (22.9 mg, 71% yield). H NMR (500 MHz, chloroform-
1
3
1
13
1
d): δ 7.97−7.85 (m, 4H), 7.56−7.48 (m, 4H), 1.34 (s, 18H). C{ H}
1
34.8, 133.1, 130.6, 130.0, 129.9, 129.8, 129.0, 22.0. GC-MS (EI, 70
NMR (126 MHz, chloroform-d): δ 194.5, 158.9, 130.6, 129.9, 126.0,
+
+
eV) m/z: 224.1 ([M] ).
1
tion by column chromatography (EtOAc/petroleum ether, v/v =
1
35.4, 31.0. GC-MS (EI, 70 eV) m/z: 322.2. ([M] ).
4c
15c
-([1,1′-Biphenyl]-4-yl)-2-phenylethane-1,2-dione (2c): Purifica-
1,2-Bis(4-fluorophenyl)ethane-1,2-dione (2l): Purification by col-
umn chromatography (EtOAc/petroleum ether, v/v = 1:50). Yellow
1
1
:50). Yellow solid (17.1 mg, 60% yield). H NMR (500 MHz,
solid (19.6 mg, 80% yield). H NMR (500 MHz, chloroform-d): δ
1
3
1
chloroform-d): δ 8.07−8.03 (m, 2H), 8.00 (dd, J = 8.0, 1.4 Hz, 2H),
8.06−7.98 (m, 4H), 7.23−7.16 (m, 4H). C{ H} NMR (126 MHz,
7
7
1
1
1
.75−7.70 (m, 2H), 7.66 (t, J = 7.5 Hz, 1H), 7.64−7.60 (m, 2H),
.52 (t, J = 7.7 Hz, 2H), 7.47 (t, J = 7.5 Hz, 2H), 7.41 (t, J = 7.4 Hz,
H). 13C{ H} NMR (126 MHz, chloroform-d): δ 194.6, 194.2, 147.6,
39.5, 134.9, 133.1, 131.7, 130.5, 130.0, 129.1, 129.1, 128.7, 127.7,
chloroform-d): δ 192.2, 166.8 (C−F, 1JC−F = 259.6 Hz), 132.8 (C−F,
3JC−F = 8.8 Hz), 129.4 (C−F, 3JC−F = 3.8 Hz), 116.4 (C−F, 2JC−F
=
1
+
22.7 Hz). GC-MS (EI, 70 eV) m/z: 246.1 ([M] ).
4
b
1,2-Bis(4-chlorophenyl)ethane-1,2-dione (2m): Purification by
+
27.4. GC-MS (EI, 70 eV) m/z: 286.1 ([M] ), 186.1 ([M −
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
+
1
PhCO] ).
1
Yellow solid (22.7 mg, 82% yield). H NMR (500 MHz, chloroform-
4a
13
1
-(4-(tert-Butyl)phenyl)-2-phenylethane-1,2-dione (2d): Purifica-
d): δ 7.97−7.87 (m, 4H), 7.55−7.45 (m, 4H). C{ H} NMR (126
tion by column chromatography (EtOAc/petroleum ether, v/v =
MHz, chloroform-d): δ 192.3, 141.8, 131.3, 131.1, 129.5. GC-MS (EI,
1
+
1
:50). Yellow oil (16.5 mg, 62% yield). H NMR (500 MHz,
70 eV) m/z: 243.1 ([M − Cl] ).
23
chloroform-d): δ 7.97 (dd, J = 8.2, 1.4 Hz, 2H), 7.93−7.89 (m, 2H),
1,2-Bis(4-(trifluoromethyl)phenyl)ethane-1,2-dione (2n): Purifica-
7
.64 (td, J = 7.3, 1.4 Hz, 1H), 7.55−7.47 (m, 4H), 1.34 (s, 9H).
tion by column chromatography (EtOAc/petroleum ether, v/v =
1
3
1
1
C{ H} NMR (126 MHz, chloroform-d): δ 194.8, 194.3, 159.0,
1:50). Yellow solid (28.0 mg, 81% yield). H NMR (500 MHz,
1
34.8, 133.1, 130.4, 129.9, 129.0, 126.0, 35.4, 31.0. GC-MS (EI, 70
chloroform-d): δ 8.12 (d, J = 8.1 Hz, 4H), 7.81 (d, J = 8.1 Hz, 4H).
+
+
13
1
eV) m/z: 251.1 ([M − CH ] ), 161.1 ([M − PhCO] ).
1
C{ H} NMR (126 MHz, chloroform-d): δ 191.9, 136.2 (C−F,
3
4a
-(4-Methoxyphenyl)-2-phenylethane-1,2-dione (2e): Purification
2JC−F = 32.8 Hz), 135.3, 130.4, 126.2 (C−F, 3JC−F = 3.8 Hz), 123.2
(C−F, 1JC−F = 273.4 Hz). GC-MS (EI, 70 eV) m/z: 327.1 ([M −
by column chromatography (EtOAc/petroleum ether, v/v = 1:50).
1
+
Yellow oil (8.6 mg, 36% yield). H NMR (500 MHz, chloroform-d): δ
F] ).
4a
7
7
.96 (ddd, J = 11.7, 7.3, 1.7 Hz, 4H), 7.64 (dd, J = 8.4, 6.6 Hz, 1H),
.50 (t, J = 7.6 Hz, 2H), 7.00−6.94 (m, 2H), 3.88 (s, 3H). C{ H}
1-Phenyl-2-(m-tolyl)ethane-1,2-dione (2o): Purification by column
1
3
1
chromatography (EtOAc/petroleum ether, v/v = 1:50). Yellow solid
1
NMR (126 MHz, chloroform-d): δ 194.8, 193.2, 165.0, 134.7, 133.2,
(15.0 mg, 67% yield). H NMR (500 MHz, chloroform-d): δ 8.00−
1
1
1
32.4, 129.9, 128.9, 126.1, 114.4, 57.7. GC-MS (EI, 70 eV) m/z:
7.94 (m, 2H), 7.80−7.74 (m, 2H), 7.69−7.63 (m, 1H), 7.51 (t, J =
7.8 Hz, 2H), 7.47 (d, J = 7.6 Hz, 1H), 7.40 (t, J = 7.6 Hz, 1H), 2.41
+
35.3 ([M − PhCO] ).
4a
13
1
-(4-Fluorophenyl)-2-phenylethane-1,2-dione (2f): Purification by
(s, 3H). C{ H} NMR (126 MHz, chloroform-d): δ 194.9, 194.7,
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
Yellow solid (19.1 mg, 84% yield). H NMR (500 MHz, chloroform-
139.0, 135.8, 134.9, 133.0, 133.0, 130.2, 129.9, 129.0, 128.9, 127.2,
1
+
21.3. GC-MS (EI, 70 eV) m/z: 224.2 ([M] ).
1-(3-Chlorophenyl)-2-phenylethane-1,2-dione (2p): Purification by
4a
d): δ 8.05−8.00 (m, 2H), 7.97 (dd, J = 8.1, 1.4 Hz, 2H), 7.67 (t, J =
7
.4 Hz, 1H), 7.52 (t, J = 7.8 Hz, 2H), 7.19 (t, J = 8.6 Hz, 2H).
C{ H} NMR (126 MHz, chloroform-d): δ 194.1, 192.7, 166.8 (C−
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
13
1
1
Yellow solid (17.1 mg, 70% yield). H NMR (500 MHz, chloroform-
F, 1JC−F = 258.3 Hz), 135.0, 132.9, 132.8 (C−F, 3JC−F = 10.1 Hz),
d): δ 7.96 (dt, J = 6.8, 1.5 Hz, 3H), 7.83 (dt, J = 7.8, 1.4 Hz, 1H),
7.69−7.64 (m, 1H), 7.61 (ddd, J = 8.0, 2.2, 1.0 Hz, 1H), 7.52 (t, J =
1
29.9, 129.5 (C−F, 3J
= 2.5 Hz), 129.1, 116.4 (C−F, 2J
= 21.4
C−F
C−F
+
13
1
Hz). GC-MS (EI, 70 eV) m/z: 228.1 ([M] ).
-(4-Chlorophenyl)-2-phenylethane-1,2-dione (2g): Purification by
7.9 Hz, 2H), 7.44 (t, J = 7.9 Hz, 1H). C{ H} NMR (126 MHz,
chloroform-d): δ 193.6, 192.9, 135.4, 135.1, 134.7, 134.5, 132.7,
130.4, 129.9, 129.5, 129.1, 128.1. GC-MS (EI, 70 eV) m/z: 244.1
4a
1
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
1
+
Yellow solid (20.2 mg, 83% yield). H NMR (500 MHz, chloroform-
([M] ).
4a
d): δ 7.97 (d, J = 7.7 Hz, 2H), 7.93 (d, J = 8.2 Hz, 2H), 7.67 (t, J =
1-Phenyl-2-(o-tolyl)ethane-1,2-dione (2q): Purification by column
1
3
1
7
.5 Hz, 1H), 7.51 (dd, J = 18.6, 7.9 Hz, 4H). C{ H} NMR (126
chromatography (EtOAc/petroleum ether, v/v = 1:50). Yellow solid
1
MHz, chloroform-d): δ 193.9, 193.1, 141.6, 135.1, 132.8, 131.4, 131.2,
(12.9 mg, 58% yield). H NMR (500 MHz, chloroform-d): δ 7.98
+
1
1
30.0, 129.5, 129.1. GC-MS (EI, 70 eV) m/z: 244.1 ([M] ).
(dd, J = 8.1, 1.4 Hz, 2H), 7.69−7.62 (m, 2H), 7.56−7.46 (m, 3H),
4a
-(4-Bromophenyl)-2-phenylethane-1,2-dione (2h): Purification by
7.35 (d, J = 7.6 Hz, 1H), 7.27 (t, J = 7.6 Hz, 1H), 2.71 (s, 3H).
1
3
1
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
C{ H} NMR (126 MHz, chloroform-d): δ 196.8, 194.8, 141.4,
1
Yellow solid (19.2 mg, 67% yield). H NMR (500 MHz, chloroform-
134.7, 133.8, 133.1, 133.1, 132.6, 131.8, 129.9, 129.0, 126.0, 21.9. GC-
+
d): δ 7.96 (d, J = 7.7 Hz, 2H), 7.84 (d, J = 8.2 Hz, 2H), 7.66 (d, J =
MS (EI, 70 eV) m/z: 224.1 ([M] ).
1-(2-Chlorophenyl)-2-phenylethane-1,2-dione (2r): Purification by
1
3
1
4a
8
.2 Hz, 3H), 7.52 (t, J = 7.7 Hz, 2H). C{ H} NMR (126 MHz,
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
Yellow solid (15.8 mg, 65% yield). H NMR (500 MHz, chloroform-
+
1
d): δ 8.06−8.01 (m, 2H), 7.92−7.87 (m, 1H), 7.67−7.61 (m, 1H),
1
3
1
7.52 (td, J = 7.6, 1.7 Hz, 3H), 7.44−7.39 (m, 2H). C{ H} NMR
(126 MHz, chloroform-d): δ 193.6, 192.0, 134.6, 134.5, 133.9, 133.8,
132.4, 132.1, 130.5, 130.2, 128.9, 127.4. GC-MS (EI, 70 eV) m/z:
+
244.1 ([M] ).
5
358
https://doi.org/10.1021/acs.joc.0c03010
J. Org. Chem. 2021, 86, 5354−5361

The Journal of Organic Chemistry
pubs.acs.org/joc
Note
2
2
1
,2-Di-m-tolylethane-1,2-dione (2s): Purification by column
134.6, 131.7, 130.3, 128.8, 26.4. GC-MS (EI, 70 eV) m/z: 134.1 ([M
+
chromatography (EtOAc/petroleum ether, v/v = 1:50). Yellow solid
− CH ] ).
2
1
15c
(
7
(
14.0 mg, 59% yield). H NMR (500 MHz, chloroform-d): δ 7.79−
1-Phenylbutane-1,2-dione (2bb): Purification by column chroma-
.76 (m, 3H), 7.76 (d, J = 1.4 Hz, 1H), 7.47 (d, J = 7.7 Hz, 2H), 7.40
tography (EtOAc/petroleum ether, v/v = 1:50). Yellow oil (11.3 mg,
1
3
1
1
t, J = 7.6 Hz, 2H), 2.41 (s, 6H). C{ H} NMR (126 MHz,
70% yield). H NMR (500 MHz, chloroform-d): δ 7.98 (dt, J = 8.4,
chloroform-d): δ 195.0, 139.0, 135.7, 133.0, 130.2, 128.9, 127.2, 21.3.
1.1 Hz, 2H), 7.64 (td, J = 7.4, 1.2 Hz, 1H), 7.53−7.47 (m, 2H), 2.92
+
13
1
GC-MS (EI, 70 eV) m/z: 238.1 ([M] ).
(qd, J = 7.2, 1.1 Hz, 2H), 1.20 (td, J = 7.3, 1.1 Hz, 3H). C{ H}
22
1
,2-Bis(3-chlorophenyl)ethane-1,2-dione (2t): Purification by col-
umn chromatography (EtOAc/petroleum ether, v/v = 1:50). Yellow
solid (17.5 mg, 63% yield). H NMR (500 MHz, chloroform-d): δ
.97 (s, 2H), 7.84 (d, J = 7.8 Hz, 2H), 7.65 (dd, J = 8.1, 2.0 Hz, 2H),
.47 (t, J = 7.9 Hz, 2H). C{ H} NMR (126 MHz, chloroform-d): δ
92.0, 135.5, 135.0, 134.2, 130.4, 129.7, 128.2. GC-MS (EI, 70 eV)
m/z: 278.0 ([M] ), 243.1 ([M − Cl] ).
,2-Di-o-tolylethane-1,2-dione (2u): Purification by column chro-
NMR (126 MHz, chloroform-d): δ 203.8, 192.5, 134.5, 131.9, 130.1,
+
1
1
28.8, 32.1, 6.7. GC-MS (EI, 70 eV) m/z: 162.1 ([M] ).
26
1
-Phenylpentane-1,2-dione (2cc): Purification by column chroma-
tography (EtOAc/petroleum ether, v/v = 1:50). Yellow oil (13.0 mg,
7
7
1
1
1
3
1
74% yield). H NMR (500 MHz, chloroform-d): δ 8.01−7.95 (m,
2
H), 7.64 (ddt, J = 8.8, 7.6, 1.3 Hz, 1H), 7.52−7.48 (m, 2H), 2.86 (t,
+
+
J = 7.3 Hz, 2H), 1.74 (h, J = 7.1 Hz, 2H), 1.01 (t, J = 7.4 Hz, 3H).
1
3
1
22
C{ H} NMR (126 MHz, chloroform-d): δ 203.4, 192.6, 134.6,
1
1
32.0, 130.1, 128.8, 40.6, 16.4, 13.7. GC-MS (EI, 70 eV) m/z: 176.1
matography (EtOAc/petroleum ether, v/v = 1:50). Yellow solid (10.7
mg, 45% yield). H NMR (500 MHz, chloroform-d): δ 7.67 (d, J =
+
1
([M] ).
1
17b
-Phenylhexane-1,2-dione (2dd): Purification by column chroma-
8
(
.1 Hz, 2H), 7.49 (t, J = 7.7 Hz, 2H), 7.35 (d, J = 7.6 Hz, 2H), 7.28
t, J = 7.5 Hz, 2H), 2.71 (s, 6H). 1 C{ H} NMR (126 MHz,
3
1
tography (EtOAc/petroleum ether, v/v = 1:50). Yellow oil (13.4 mg,
1
7
1% yield). H NMR (500 MHz, chloroform-d): δ 8.00−7.95 (m,
chloroform-d): δ 196.9, 141.5, 133.6, 133.0, 132.6, 131.8, 126.0, 21.9.
+
2H), 7.64 (ddt, J = 8.8, 7.1, 1.4 Hz, 1H), 7.50 (t, J = 7.8 Hz, 2H), 2.88
(t, J = 7.4 Hz, 2H), 1.72−1.65 (m, 2H), 1.45−1.37 (m, 2H), 0.95 (t, J
7.3 Hz, 3H). C{ H} NMR (126 MHz, chloroform-d): δ 203.5,
GC-MS (EI, 70 eV) m/z: 238.1 ([M] ).
2
4
1
,2-Bis(2-chlorophenyl)ethane-1,2-dione (2v): Purification by
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
Yellow solid (15.0 mg, 54% yield). H NMR (500 MHz, chloroform-
d): δ 8.07 (dd, J = 7.8, 1.8 Hz, 2H), 7.57 (td, J = 7.7, 1.8 Hz, 2H),
1
3
1
=
1
192.5, 134.5, 132.0, 130.1, 128.8, 38.5, 24.9, 22.3, 13.8. GC-MS (EI,
+
7
0 eV) m/z: 190.1 ([M] ).
27
1
3
1
1-Phenylheptane-1,2-dione (2ee): Purification by column chroma-
7
.47 (ddd, J = 15.1, 7.8, 1.2 Hz, 4H). C{ H} NMR (126 MHz,
tography (EtOAc/petroleum ether, v/v = 1:50). Yellow oil (13.8 mg,
chloroform-d): δ 191.0, 135.0, 134.8, 132.7, 132.2, 130.9, 127.2. GC-
1
+
68% yield). H NMR (500 MHz, chloroform-d): δ 8.01−7.95 (m,
MS (EI, 70 eV) m/z: 243.1 ([M − Cl] ).
4b
2H), 7.64 (td, J = 7.3, 1.4 Hz, 1H), 7.50 (t, J = 7.8 Hz, 2H), 2.87 (t, J
1
-(3-Fluorophenyl)-2-phenylethane-1,2-dione (2w): Purification by
=
7.4 Hz, 2H), 1.70 (p, J = 7.3 Hz, 2H), 1.36 (m, 4H), 0.91 (t, J = 7.0
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
Yellow solid (16.6 mg, 73% yield). H NMR (500 MHz, chloroform-
d): δ 7.97 (d, J = 7.7 Hz, 2H), 7.71 (dt, J = 22.9, 7.6 Hz, 3H), 7.57−
.46 (m, 3H), 7.37 (td, J = 8.4, 2.4 Hz, 1H). C{ H} NMR (126
13 1
1
Hz, 3H). C{ H} NMR (126 MHz, chloroform-d): δ 203.5, 192.6,
34.5, 132.1, 130.2, 128.8, 38.8, 31.3, 22.6, 22.4, 13.9. GC-MS (EI, 70
1
+
eV) m/z: 204.2 ([M] ).
-Phenyloctane-1,2-dione (2ff): Purification by column chromatog-
raphy (EtOAc/petroleum ether, v/v = 1:50). Yellow oil (15.7 mg,
1
3
1
7
5
1
MHz, chloroform-d): δ 193.7, 193.0 (C−F, 3J
= 2.5 Hz), 162.9
C−F
(C−F, 1J
= 249.5 Hz), 135.1, 135.0 (C−F, 3J
= 6.3 Hz),
1
C−F
C−F
7
2
2
3
2% yield). H NMR (500 MHz, chloroform-d): δ 8.00−7.95 (m,
H), 7.67−7.61 (m, 1H), 7.50 (t, J = 7.8 Hz, 2H), 2.87 (t, J = 7.4 Hz,
H), 1.70 (p, J = 7.5 Hz, 2H), 1.41−1.35 (m, 2H), 1.31 (dq, J = 7.3,
1
3
2
1
32.72, 130.8 (C−F, 3J
C−F
= 7.6 Hz), 130.0, 129.1, 126.0 (C−F,
C−F
J
= 3.8 Hz), 122.0 (C−F, 2J
= 21.4 Hz), 116.1 (C−F, 2J
=
C−F
C−F
+
3.9 Hz). LC-MS (ESI) m/z: 229.1 ([M + H] ).
13
1
.7, 3.2 Hz, 4H), 0.89 (t, J = 7.0 Hz, 3H). C{ H} NMR (126 MHz,
20
-Phenyl-2-(3-(trifluoromethyl)phenyl)ethane-1,2-dione (2x): Pu-
rification by column chromatography (EtOAc/petroleum ether, v/v =
:50). Yellow solid (20.0 mg, 72% yield). H NMR (500 MHz,
chloroform-d): δ 203.5, 192.6, 134.5, 132.1, 130.2, 128.9, 38.8, 31.5,
+
2
8.8, 22.9, 22.5, 14.0. GC-MS (EI, 70 eV) m/z: 218.2 ([M] ).
1
1
chloroform-d): δ 8.28 (s, 1H), 8.15 (d, J = 7.8 Hz, 1H), 7.99 (d, J =
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.joc.0c03010.
7
7
1
.6 Hz, 2H), 7.91 (d, J = 7.8 Hz, 1H), 7.68 (dt, J = 14.9, 7.6 Hz, 2H),
■
*
1
3
1
sı
.54 (t, J = 7.7 Hz, 2H). C{ H} NMR (126 MHz, chloroform-d): δ
93.3, 192.6, 135.3, 133.6, 133.2, 132.6, 131.8 (C−F, 2JC−F = 32.8
Hz), 131.1 (C−F, 3J
= 3.8 Hz), 130.0, 129.7, 129.2, 126.4 (C−F,
C−F
3
2
1
J
= 3.8 Hz), 123.4 (C−F, 1J
= 273.4 Hz). LC-MS (ESI) m/z:
C−F
C−F
+
Full optimization of the reaction conditions, MS spectra
79.1 ([M + H] ).
-(4-Ethylphenyl)-2-phenylethane-1,2-dione (2y): Purification by
1
8
1
25
of O-isotope labeling experiments, and H and
1
3
1
C{ H} NMR spectra of 1,2-diketones (2a−2z, 2aa−
column chromatography (EtOAc/petroleum ether, v/v = 1:50).
1
Yellow oil (12.1 mg, 13% yield). H NMR (500 MHz, chloroform-d):
2ff) (PDF)
δ 7.97 (d, J = 7.8 Hz, 2H), 7.90 (d, J = 7.9 Hz, 2H), 7.65 (t, J = 7.5
Hz, 1H), 7.50 (t, J = 7.7 Hz, 2H), 7.33 (d, J = 7.9 Hz, 2H), 2.73 (q, J
AUTHOR INFORMATION
Corresponding Authors
1
3
1
■
=
7.7 Hz, 2H), 1.26 (t, J = 7.6 Hz, 3H). C{ H} NMR (126 MHz,
chloroform-d): δ 194.7, 194.3, 152.3, 134.7, 133.1, 130.8, 130.1,
+
1
4
29.9, 128.9, 128.6, 29.2, 15.0. LC-MS (ESI) m/z: 239.2 ([M + H] ).
Duyi Shen − Key Laboratory of Life-Organic Analysis of
Shandong Province, School of Chemistry and Chemical
Engineering, Qufu Normal University, Qufu 273165, P. R.
China; orcid.org/0000-0001-8244-9909;
4a
-(2-Oxo-2-phenylacetyl)benzaldehyde (2z): Purification by col-
umn chromatography (EtOAc/petroleum ether, v/v = 1:50). Yellow
1
solid (3.0 mg, 13% yield). H NMR (500 MHz, chloroform-d): δ
1
0.02 (s, 1H), 7.89−7.84 (m, 2H), 7.68 (d, J = 7.9 Hz, 2H), 7.56
Email: shendy@qfnu.edu.cn
13 1
(
ddt, J = 5.1, 2.7, 1.3 Hz, 2H), 7.38 (tt, J = 3.7, 1.9 Hz, 3H). C{ H}
NMR (126 MHz, chloroform-d): δ 193.5, 193.4, 191.3, 140.0, 137.1,
35.2, 132.6, 130.4, 130.0, 130.0, 129.2. LC-MS (ESI) m/z: 239.0
Yulei Zhao − Key Laboratory of Life-Organic Analysis of
Shandong Province, School of Chemistry and Chemical
Engineering, Qufu Normal University, Qufu 273165, P. R.
China; orcid.org/0000-0002-8628-2680;
1
+
(
1
[M + H] ).
-Phenylpropane-1,2-dione (2aa): Purification by column chroma-
tography (EtOAc/petroleum ether, v/v = 1:50). Yellow oil (8.9 mg,
5
Email: zhaoyulei86@126.com
1
Mianran Chao − Key Laboratory of Life-Organic Analysis of
Shandong Province, School of Chemistry and Chemical
Engineering, Qufu Normal University, Qufu 273165, P. R.
60% yield). H NMR (500 MHz, chloroform-d): δ 8.01 (d, J = 7.6
Hz, 2H), 7.64 (td, J = 7.5, 1.3 Hz, 1H), 7.50 (t, J = 7.5 Hz, 2H), 2.53
s, 3H). 13C{ H} NMR (126 MHz, chloroform-d): δ 200.6, 191.4,
1
(
5
359
https://doi.org/10.1021/acs.joc.0c03010
J. Org. Chem. 2021, 86, 5354−5361

The Journal of Organic Chemistry
pubs.acs.org/joc
Note
China; orcid.org/0000-0002-9864-0633;
Email: chaomr@qfnu.edu.cn
4711. (d) Alterman, J. L.; Vang, D. X.; Stroud, M. R.; Halverson, L. J.;
Kraus, G. A. Ozonolysis of alkynes-A flexible route to alpha-diketones:
Synthesis of AI-2. Org. Lett. 2020, 22, 7424−7426.
Authors
(3) For selected reviews, please see: (a) Yuan, L.-Z.; Hamze, A.;
Alami, M.; Provot, O. Synthesis of substituted benzils from
diarylalkyne oxidation. Synthesis 2017, 49, 504−525. (b) Sawama,
Y.; Asai, S.; Monguchi, Y.; Sajiki, H. Versatile oxidation methods for
organic and inorganic substrates catalyzed by platinum-group metals
on carbons. Chem. Rec. 2016, 16, 261−272.
Hongyan Wang − Key Laboratory of Life-Organic Analysis of
Shandong Province, School of Chemistry and Chemical
Engineering, Qufu Normal University, Qufu 273165, P. R.
China
Yanan Zheng − Key Laboratory of Life-Organic Analysis of
Shandong Province, School of Chemistry and Chemical
Engineering, Qufu Normal University, Qufu 273165, P. R.
China
Xinjing Zhu − Key Laboratory of Life-Organic Analysis of
Shandong Province, School of Chemistry and Chemical
Engineering, Qufu Normal University, Qufu 273165, P. R.
China
Peiwei Gong − Key Laboratory of Life-Organic Analysis of
Shandong Province, School of Chemistry and Chemical
Engineering, Qufu Normal University, Qufu 273165, P. R.
China; orcid.org/0000-0003-2514-015X
Bin Wang − School of Chemistry and Chemical Engineering,
University of Jinan, Jinan 250022, P. R. China
Jinmao You − Key Laboratory of Life-Organic Analysis of
Shandong Province, School of Chemistry and Chemical
Engineering, Qufu Normal University, Qufu 273165, P. R.
China; Northwest Institute of Plateau Biology, Chinese
Academy of Science, Xining 810001, P. R. China;
orcid.org/0000-0002-8808-6085
(4) For selected examples, please see: (a) Liu, X.; Cong, T.; Liu, P.;
Sun, P. Synthesis of 1,2-diketones via a metal-free, visible-light-
induced aerobic photooxidation of alkynes. J. Org. Chem. 2016, 81,
7256−7261. (b) Zhu, X.; Li, P.; Shi, Q.; Wang, L. Thiyl radical
catalyzed oxidation of diarylalkynes to α-diketones by molecular
oxygen under visiblelight irradiation. Green Chem. 2016, 18, 6373−
6379. (c) Qin, H.-T.; Xu, X.; Liu, F. Aerobic oxidation of alkynes to
1,2-diketones by organic photoredox catalysis. ChemCatChem 2017, 9,
1
(
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The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We are thankful for the financial support from National
Natural Science Foundation of China (21802084, 51805295,
1905304, and 21771087) and the Natural Science Founda-
tion of Shandong Province (ZR2019BB021 and
ZR2018BB026).
■
2
2
8
ACS Catal. 2018, 8, 5085−5144. (b) Sathyamoorthi, S.; Banerjee, S.
Peroxydisulfate as an oxidant in the site-selective functionalization of
5
3
sp C−H bonds. ChemistrySelect 2017, 2, 10678−10688. (c) Blon-
diaux, E.; Bomon, J.; Smolen, M.; Kaval, N.; Lemiere, F.; Sergeyev, S.;
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Diels, L.; Sels, B.; Maes, B. U. W. Bio-based aromatic amines from
lignin-derived monomers. ACS Sustainable Chem. Eng. 2019, 7, 6906−
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