Palladium-Catalyzed Oxidative C≡C Triple Bond Cleavage of 2-Alkynyl Carbonyl Compounds Toward 1,2-Dicarbonyl Compounds?

Article abstract of DOI:10.1002/cjoc.202000040

A new, general palladium-catalyzed oxidative strategy for the cleavage of the C≡C triple bond is presented. By employing PdCl₂, CuBr₂, TEMPO and air as the catalytic system and H₂O as the carbonyl oxygen atom source, a wide range of 2-alkynyl carbonyl compounds, including 1,3-disubstituted prop-2-yn-1-ones, propiolamides and propiolates, lost an alkynyl carbon to access various 1,2-dicarbonyl compounds, e.g., 1,2-diones, 2-keto amides and 2-keto esters, through Wacker oxidation, intramolecular cyclization and C—C bond cleavage cascades.

Full text of DOI:10.1002/cjoc.202000040

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Accepted Article
Title: Palladium-Catalyzed Oxidative CC Triple Bond Cleavage of 2-Alkynyl
Carbonyl Compounds Toward 1,2-Dicarbonyl Compounds
Authors: Ming-Bo Zhou, Mu-Jia Luo, Ming Hu, and Jin-Heng Li*
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This work may now be cited as: Chin. J. Chem. 2020, 38, 10.1002/cjoc.202000040.
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Palladium-Catalyzed Oxidative CC Triple Bond Cleavage of 2-Alkynyl
Carbonyl Compounds Toward 1,2-Dicarbonyl Compounds
Ming-Bo Zhou,b,† Mu-Jia Luo,a,c,† Ming Hu,a and Jin-Heng Li*,a,b,c
a Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, Nanchang Hangkong University, Nanchang 330063, China
b Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education), Hunan Normal University, Changsha 410081, China
c State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, China
† M.-B.Z. and M.-J.L. contributed equally to this work
Dedicated to Professor Qing-Yun Chen on the occasion of his 90th birthday
A new, general palladium-catalyzed oxidative strategy for the cleavage of the CC triple bond is presented. By employing PdCl2, CuBr2, TEMPO and air as
the catalytic system and H2O as the carbonyl oxygen atom source, a wide range of 2-alkynyl carbonyl compounds, including 1,3-disubstituted
prop-2-yn-1-ones, propiolamides and propiolates, lost an alkynyl carbon to access various 1,2-dicarbonyl compounds, e.g., 1,2-diones, 2-keto amides
and 2-keto esters, through Wacker oxidation, intramolecular cyclization and C-C bond cleavage cascades.
an alkynyl carbon-lost process (Scheme 1b).
Background and Originality Content
Alkynes are importantly common chemical feedstocks that
have been widely used in synthetic community. Accordingly, the
development of methods for transformations of alkynes to
increase molecular complexity and construct functional molecules
has attracted ongoing attention.1-9 Attractive methods include
transformations of alkynes by cleavage of the CC triple bonds.2-8
Although the cleavage of the CC triple bond of alkynes has been
widely explored, it remains a great challenge of completely
cleaving the CC triple bond and then functionalizing. Traditionally,
the CC triple bond is cleaved by ligating to metal complexes and
oxidative cleavage using a stoichiometric amount of metal
reagents.2,3 However, only a few papers3-7 on the metal-catalyzed
alkyne cleavage reactions have been reported except for
metathesis of alkynes.8 For example, the initial Rh-catalyzed
alkynes cleavage protocol used additional 2-aminopyridine or
2-aminophenol to in situ react with alkynes leading to the CC
triple bond cleavage.3,4 Subsequently, 1,n-ynols were employed
for the alkyne cleavage purpose by either Ru-catalyzed
OH-elimination generating alkene and CO5 or Au-catalyzed
OH-addition leading to butenolides and acids.6 Jiang and Wang
have established a Lewis acid promoted palladium-catalyzed
oxidative cleavage of alkynes with molecular oxygen to furnish
esters in the presence of additional alcohols.7a Thus, the
development of new metal-catalyzed alkynes cleavage
transformations are still fascinated due to its cascade or domino
strategy. In 2014, Cui and coworkers7b found a new radical
strategy for the cleavage of the C≡C triple bonds where a
combination of a base (K2CO3) with O2 as both the oxidant and the
carbonyl oxygen atom source enabled oxidative conversion of
diaryl eth-2-yn-1-ones to 1,2-diketones (Scheme 1a). However,
this method is limited to 1,3-diaryl prop-2-yn-1-ones probably
because the in-situ generation of the superoxide radical
intermediates requires the aryl functional groups to activate them.
Due to an interest in the palladium-catalyzed transformations of
alkynes, and inspired by Wan’s work which involved a new
Wacker-type oxidation of alkynes mediated by PdBr2 and CuBr2,9h-i
we accidentally found a CC triple bond cleavage using 2-alkynyl
carbonyl compounds as the starting materials, which meanwhile
led to an efficient approach to 1,2-dicarbonyl compounds through
Scheme 1 Oxidative transformations of 2-alkynyl carbonyl compounds.
Results and Discussion
Optimization of Reaction Conditions
We initiated our study by examining the reaction of
1,3-diphenylprop-2-yn-1-one (1a) with PdCl2 and CuBr2 in dioxane
o
at 80 C under air atmosphere: we were pleased to find that an
unexpected benzil (2a) was isolated in 16% yield (entry 1 in Table
1). Distinctly, benzil (2a) is generated by a carbon-lost process
from 1,3-diphenylprop-2-yn-1-one (1a), which may proceed via
the oxidative cleavage of the CC triple bond. Based on these
considerations, several oxidants, TEMPO, TBHP, DDQ and K2S2O8,
were investigated (Table S1; Supporting Information). Screening
revealed that TEMPO displayed the highest activity: treatment of
substrate 1a with 10 mol% of PdCl2, 1.2 equiv of CuBr2 and 1.2
equiv of TEMPO afforded benzil (2a) in 82% yield (entry 2). Among
the effects of Pd and Cu examination, it turned out that the
reaction was carried out at 10 mol% of PdCl2 and 1.2 equiv of
CuBr2, providing the best results (entries 2-9). Screening revealed
that the amount of water in dioxane influenced the reaction in
terms of yield: the yield of 2a was lowered to 66% using 0.25 mL
of H2O and 61% in 2 mL of H2O (entries 2, 10 and 11). Notably, the
reactivity of substrate 1a was decreased under either O2 or argon
atmosphere, suggesting that air can facilitate the reaction (entries
12 and 13). It is noteworthy that the Cu salt acts as a promoter as
without it the reaction could occur in 31% yield (entry 14).
However, Pd catalysts were crucial because omission of them the
*E-mail: jhli@hnu.edu.cn
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reaction could not take place (entry 15).
yields.
In light of the above results, substituents adjacent to the
carbonyl moiety of 2-alkynyl carbonyl compounds were tested
(2k-s). Using 1-arylprop-2-yn-1-one, possessing a para-MeO group,
on the aryl ring was converted efficiently to 2k in 73% yield.
Gratifyingly, for 1-arylprop-2-yn-1-ones bearing a para- or an
ortho-Cl group the reaction executed smoothly to afford 2l-n,
respectively, in 74-80% yields. Notably, the reaction of
1-(4-chlorophenyl)-3-(p-tolyl)prop-2-yn-1-one only furnished
1-(4-chlorophenyl)-2-(p-tolyl)ethane-1,2-dione 2n in 80% yield,
and the cross CC triple bond cleavage products, such as
Table 1 Screening of the optimal reaction conditionsa
Entry
1c
[Pd] (mol%)
PdCl2 (10)
[Cu]
Solvent (v/v)
Yield (%)b
16
CuBr2
H2O/dioxane (1/4)
1,2-dip-tolylethane-1,2-dione
and
PdCl2 (10)
PdCl2 (15)
PdCl2 (5)
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuCl2
Cu(OAc)2
CuBr2
CuBr2
CuBr2
CuBr2
―
82
81
71
78
71
68
58
41
66
61
68
56
31
0
H2O/dioxane (1/4)
H2O/dioxane (1/4)
H2O/dioxane (1/4)
H2O/dioxane (1/4)
H2O/dioxane (1/4)
H2O/dioxane (1/4)
H2O/dioxane (1/4)
H2O/dioxane (1/4)
H2O/dioxane (1/9)
H2O/dioxane (4/1)
H2O/dioxane (1/4)
H2O/dioxane (1/4)
2
3
1,2-bis(4-chlorophenyl)ethane-1,2-dione, were not observed by
GC-MS analysis. The results imply the reaction proceeds via an
intramolecular CC triple bond cleavage process. The reaction was
applicable to both propiolamides and propiolate, accessing the
corresponding products 2o-2r in good yields. Unfortunately,
attempts to execute oxidative transformations of terminal ynones
1t-u failed (2t-2u).
4
PdBr2 (10)
Pd(OAc)2 (10)
Pd(PPh3)4 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
―
5
6
Table 2 Variation of the 2-alkynyl carbonyl compounds (1)a
7
8
9
10
11
12d
13e
14
15
H2O/dioxane (1/4)
H2O/dioxane (1/4)
CuBr2
a
Reaction conditions: 1a (0.3 mmol), [Pd], [Cu] (1.2 equiv), TEMPO (1.2
equiv), and H2O/solvent (2.5 mL) at 80 oC for 36 h under air atmosphere.
Isolated yield. Without TEMPO. Under O2 (1 atm) atmosphere. Under
argon atmosphere.
b
c
d
e
As shown in Table 2, the generality of this Pd-catalyzed
oxidative CC triple bond cleavage protocol with regard to
2-alkynyl carbonyl compounds was investigated under the optimal
reaction conditions. A variety of 3-oxoprop-1-ynyl compounds,
including 2-yn-1-ones, propiolamides and propiolate, successfully
underwent the reaction in moderate to good yields (Products
2b-s). Using 10 mol % of PdCl2, 1.2 equiv of CuBr2 and 1.2 equiv of
TEMPO, a number of substituents, such as electron-rich or
electron-deficient aryl, heteroaryl, vinyl and aliphatic groups, at
the terminal alkyne moiety of 2-yn-1-ones were all tolerated
(2b-2j). We found that substituents, including Me, MeO and
MeCO, on the aryl ring were well tolerated (2b-d), and the
electron-withdrawing MeCO group showed lower reactivity than
the electron-donating groups (e.g., Me, MeO). While alkyne
bearing a p-methoxyphenyl group reacted with PdCl2, CuBr2,
TEMPO and air smoothly to furnish the desired product 2c in 79%
yield, alkyne with an acetyl (MeCO) group diminished the yield of
2d to 63%. Notably, the introduction of a heterocycle or a
cyclohex-1-en-1-yl group into this system were also efficient for
accessing 2e-f in good yields, which makes this methodology
more valuable for the preparation of pharmaceuticals and nature
products. We were pleased to find that internal
2-alkyl-1-arylacetylenes, such as 1-phenylundec-2-yn-1-one,
7-chloro-1-phenylhept-2-yn-1-one,
a
Reaction conditions: 1a (0.3 mmol), PdCl2 (10 mol %), CuBr2 (1.2 equiv),
TEMPO (1.2 equiv), and H2O/dioxane (1:4, 2.5 mL) at 80 oC for 36 h under
air atmosphere.
To understand the mechanism, some controlled experiments
were carried out (Scheme 2). Two 13C-labeled experiments
showed that the alkynyl carbon adjacent to the carbonyl group
was lost during the CC triple bond cleavage process (eqs 1 and 2).
Subsequently, treatment of substrate 1a with H218O, PdCl2, CuCl2,
TEMPO and air afforded the corresponding 18O-containing product
2a-18O determined by GC-MS analysis (eq 3). To our surprise, the
HRMS analysis indicated that some of oxygen of the inherent
carbonyl group of 1a was replaced by 18O (2a-18O).10 We found
that a trace of 3-hydroxy-1,3-diphenylprop-2-en-1-one (3a) was
observed by GC-MS analysis during the reaction of 1a (Table 1).
Thus, 3-hydroxy-1,3-diphenylprop-2-en-1-one (3a) was employed
for the reaction in the presence of PdCl2, CuBr2, TEMPO and air:
Indeed, substrate 3a could be converted to the desired product 2a
in 80% yield (eq 4). This suggests that the reaction may proceed
via the similar 3-hydroxy-prop-2-en-1-one intermediate.11 Notably,
3-cyclopropyl-1-phenylprop-2-yn-1-one
and
bulky
4,4-dimethyl-1-phenylpent-2-yn-1-one, were consistent with the
optimal conditions, giving the corresponding products 2g-j in high
2
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Running title
Chin. J. Chem.
the cross reaction with ynones 1a and 1k gave no the cross
product 2ak, supporting an intramolecular process (eq 5).
oxidative tandem strategy to allows a wide range of 2-alkynyl
carbonyl
compounds,
including
1,3-disubstituted
prop-2-yn-1-ones, propiolamides and propiolates, to undergo the
CC triple bond cleavage with excellent selectivity and functional
group compatibility. The mechanism was also discussed according
to the 13C-labeled and 18O-labeled experiments.
Scheme 2 Control Experiments
Experimental
General experimental section.
2-Alkynyl carbonyl compounds 1 were prepared according to
the known procedures.15 All the other materials and solvents
were purchased from commercial suppliers and used without
1
additional purification. H and 13C NMR spectra were recorded on
a Bruker DRX-500 spectrometer (1H at 500 MHz and 13C at 125
MHz). NMR data were obtained in CDCl3 unless otherwise noted.
High-resolution mass spectra were recorded on
a Bruker
microTOF-QII (ESI) spectrometer. Preparative thin-layer
chromatography was performed on silica gel plates with PF254
indicator. Flash column chromatography was performed with silica
gel 60N unless otherwise noted.
Typical Experimental Procedure for Palladium-Catalyzed
Oxidative Cleavage of the CC Triple Bond of
3-Oxoprop-1-ynyl Compounds (1):
Therefore, a possible mechanism as outlined in Scheme 3 was
proposed on the basis of the current results and the previously
reported literatures. Complexation of PdCl2 with alkyne 1a
generates intermediate A, followed by Wacker oxidation of the
CC triple bond in the alkyne with H2O to affords intermediate
B.11,12 Intermediate B undergoes the second Wacker reaction13
with the aid of TEMPO to yield intermediate C, and then
To a Schlenk tube was added alkynes 1 (0.3 mmol), PdCl2 (10
mol %), CuBr2 (1.2 equiv), TEMPO (1.2 equiv) and dioxane (2.0 mL)
o
and H2O (0.5 mL) was stirred at 85 C under air atmosphere for
the indicated time (36 h) until complete consumption of starting
material as monitored by TLC and GC-MS analysis. After the
reaction was finished, the mixture was filtered, washed with water,
and extracted with ethyl acetate. The organic layer was dried over
Na2SO4 and evaporated in vacuum. The residue was purified by
flash column chromatography on silica gel (hexane/ethyl acetate)
to afford the desired products 2.
deprotonation
to
intermediate
D
and
2,2,6,6-tetramethylpiperidin-1-ol, in which TEMPO is regenerated
from the oxidation of 2,2,6,6-tetramethylpiperidin-1-ol by O2 (air).
Intramolecular addition to the pre-existing carbonyl group of
intermediate D results in intermediates E and F.14 Finally,
sequential decarbonylation and reductive elimination of
intermediate F takes place leading to the desired product 2a, CO,
HX and Pd(0) species. Oxidation of the Pd(0) species by CuBr2
regenerates the active Pd(II) species to start the new catalytic
cycle.
Analytical data for 2 and 3
(Main Text Paragraphs) Please include all the experimental
details here excluding those in Supporting Information.
1,2-Diphenylethane-1,2-dione (2a):16a Green solid, mp:
1
94-95 °C (uncorrected); H NMR (500 MHz, CDCl3) δ: 7.98 (d, J =
8.0 Hz, 4H), 7.66 (t, J = 7.5 Hz, 2H), 7.51 (t, J = 7.5 Hz, 4H);13C NMR
(125 MHz, CDCl3) δ: 194.5, 134.9, 132.9, 129.9, 129.0; IR (KBr,
cm-1): 1659; LRMS (EI 70 ev) m/z (%): 210 (M+, 3), 105 (100), 77
(51), 51 (20).
Scheme 3 Possible mechanisms
1-Phenyl-2-p-tolylethane-1,2-dione (2b):16a Brown oil; 1H
NMR (500 MHz, CDCl3) δ: 7.87 (d, J = 7.5 Hz, 2H), 7.78 (d, J = 8.0
Hz, 2H), 7.55 (t, J = 7.0 Hz, 1H), 7.41 (t, J = 7.5 Hz, 2H), 7.21 (d, J =
8.0 Hz, 2H), 2.34 (s, 3H); 13C NMR (125 MHz, CDCl3) δ: 194.7, 194.3,
146.2, 134.8, 133.0, 130.5, 129.9, 129.8, 129.7, 128.9, 21.9; IR
(KBr, cm-1): 1655, 1685; LRMS (EI 70 ev) m/z (%): 224 (M+, 2), 119
(100), 105 (24), 91 (37).
1-(4-Methoxyphenyl)-2-phenylethane-1,2-dione
(2c):16a
Green oil; 1H NMR (500 MHz, CDCl3) δ: 7.97-7.93 (m, 4H), 7.63 (t, J
= 7.5 Hz, 1H), 7.49 (t, J = 7.5 Hz, 2H), 6.96 (d, J = 9.0 Hz, 2H), 3.86
(s, 3H); 13C NMR (125 MHz, CDCl3) δ: 194.8, 193.1, 164.9, 134.6,
133.0, 132.3, 129.8, 128.8, 125.9, 114.3, 55.5; IR (KBr, cm-1): 1668,
1593; LRMS (EI 70 ev) m/z (%): 240 (M+, 1), 135 (100), 107 (11), 92
(13), 77 (38), 51 (9).
1-(4-Acetylphenyl)-2-phenylethane-1,2-dione (2d):16b Green
1
oil; H NMR (500 MHz, CDCl3) δ: 7.98 (s, 4H), 7.89 (d, J = 8.0 Hz,
2H), 7.60 (t, J = 7.5 Hz, 1H), 7.45 (t, J = 7.5 Hz, 2H), 2.58 (s, 3H); 13
C
Conclusions
NMR (125 MHz, CDCl3) δ: 197.2, 193.7, 193.6, 141.2, 135.9, 135.1,
132.6, 130.0, 129.9, 129.1, 128.7, 26.9; IR (KBr, cm-1): 1773, 1683;
LRMS (EI 70 ev) m/z (%): 252 (M+, 3), 147 (19), 119 (6), 105 (100),
91 (9), 77 (42), 43 (13).
In summary, we have described a novel palladium-catalyzed
oxidative cleavage of the CC triple bond in 2-alkynyl carbonyl
compounds for the synthesis of 1,2-dicarbonyl compounds using
H2O as the carbonyl oxygen atom source. This method employs an
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1-Phenyl-2-(thiophen-3-yl)ethane-1,2-dione (2e):16c Green
δ: 193.6, 193.2, 146.4, 141.4, 131.4, 131.2, 130.3, 130.0, 129.8,
129.4, 21.9; IR (KBr, cm-1): 1667; LRMS (EI 70 ev) m/z (%): 260
(M++2, 1), 258 (M+, 3), 119(100).
oil; 1H NMR (500 MHz, CDCl3) δ: 7.96 (d, J = 8.0 Hz, 2H), 7.76 (d, J
= 5.0 Hz, 1H), 7.72 (d, J = 4.0 Hz, 1H), 7.57 (t, J = 8.0 Hz, 1H), 7.44
(t, J = 8.0 Hz, 2H), 7.11 (d, J = 5.0 Hz, 1H); 13C NMR (125 MHz,
CDCl3) δ: 192.0, 185.6, 139.8, 136.9, 136.7, 134.8, 132.6, 130.2,
1
N,N-Diethyl-2-oxo-2-phenylacetamide (2p):16h Green oil; H
NMR (500 MHz, CDCl3) δ: 7.94 (d, J = 8.0 Hz, 2H), 7.64 (t, J = 7.0 Hz,
128.9, 128.8; IR (KBr, cm-1):1685; LRMS (EI 70 ev) m/z (%): 216 (M+, 1H), 7.51 (t, J = 7.5 Hz, 2H), 3.59-3.55 (m, 2H), 3.27-3.23 (m, 2H),
7), 111 (49), 105 (100), 77 (45).
1-Cyclohexenyl-2-phenylethane-1,2-dione (2f): Green oil; H
1.29 (t, J = 7.0 Hz, 3H), 1.16 (t, J = 7.0 Hz, 3H); 13C NMR (125 MHz,
CDCl3) δ: 191.5, 166.7, 134.5, 133.2, 129.5, 128.9, 42.1, 38.8, 14.0,
1
NMR (500 MHz, CDCl3) δ: 7.81 (d, J = 8.0 Hz, 2H), 7.56 (t, J = 7.5 Hz, 12.8; IR (KBr, cm-1): 1679, 1654; LRMS (EI 70 ev) m/z (%): 205 (M+,
1H), 7.42 (t, J = 7.5 Hz, 2H), 6.77-6.76 (m, 1H), 2.33-2.30 (m, 2H),
2.22-2.18 (m, 2H), 1.67-1.58 (m, 4H);13C NMR (125 MHz, CDCl3) δ:
196.5, 195.7, 149.9, 137.0, 134.5, 133.3, 129.6, 128.8, 26.6, 21.9,
21.4; IR (KBr, cm-1): 2848, 1667, 1662; LRMS (EI 70 ev) m/z (%):
214 (M+, 11), 105 (42), 109 (100), 81 (60), 77 (47), 51 (18); HRMS
m/z (ESI) calcd for C14H15O2 [M+H]+ 215.1067, found 214.1073.
1-Phenyldecane-1,2-dione (2g):16d Green oil; 1H NMR (500
MHz, CDCl3) δ: 7.93 (d, J = 7.0 Hz, 2H), 7.59 (t, J = 7.0 Hz, 1H), 7.44
(t, J = 7.5 Hz, 2H), 2.82 (t, J = 7.5 Hz, 2H), 1.66-1.63 (m, 2H),
1.32-1.22 (m, 10H), 0.83 (t, J = 6.8 Hz, 3H); 13C NMR (125 MHz,
CDCl3) δ: 203.3, 192.3, 134.3, 131.8, 129.9, 128.6, 38.6, 31.5, 29.0,
28.9, 28.8, 22.6, 22.4, 13.8; IR (KBr, cm-1): 2917, 2847, 1720, 1671;
LRMS (EI 70 ev) m/z (%): 246 (M+, 1), 141 (6), 105 (100), 77 (25),
71 (11), 57 (13).
2), 105 (48), 100 (100), 77 (35) 72 (75).
N-Butyl-2-oxo-2-phenylacetamide (2q):16i Green oil; 1H NMR
(500 MHz, CDCl3) δ: 8.26 (d, J = 8.0 Hz, 2H), 7.55 (t, J = 7.5 Hz, 1H),
7.41 (t, J = 7.5 Hz, 2H), 7.02 (brs, 1H), 3.35-3.31 (m, 2H), 1.54-1.50
(m, 2H), 1.36-1.32 (m, 2H), 0.89 (t, J = 7.5 Hz, 3H);13C NMR (125
MHz, CDCl3) δ: 187.9, 161.7, 134.3, 133.4, 131.2, 128.4, 39.1, 31.3,
20.0, 13.7; IR (KBr, cm-1): 3388, 2954, 2921, 1664; LRMS (EI 70 ev)
m/z (%): 205 (M+, 12), 105 (100), 77 (38), 57 (25).
N-Benzyl-N-butyl-2-oxo-2-phenylacetamide (2r): Green
oil;1H NMR (500 MHz, CDCl3) δ: 7.87 (t, J = 4.5 Hz, 2H), 7.53 (d, J =
7.5 Hz, 1H), 7.41 (t, J = 7.5 Hz, 2H), 7.29 (d, J = 4.5 Hz, 2H),
7.24-7.17 (m, 3H), 4.67 (s, 1H), 4.30 (s, 1H), 3.33 (t, J = 7.5 Hz, 1H),
3.00 (t, J = 7.5 Hz, 1H), 1.54-1.51 (m, 1H), 1.45-1.42 (m, 1H), 1.27
(t, J = 7.5 Hz, 1H), 1.07-1.02 (m, 1H), 0.85 (t, J = 7.5 Hz, 1.5H), 0.67
(t, J = 7.5 Hz, 1.5H); 13C NMR (125 MHz, CDCl3) δ: 191.4, 191.2,
167.3, 167.2, 136.2, 135.1, 134.5, 133.2, 130.0, 129.6, 129.5,
128.9, 128.9, 128.7, 128.6, 128.3, 128.2, 128.0, 127.8, 127.7, 51.0,
46.8, 46.6, 43.3, 29.9, 28.8, 20.0, 19.6, 13.7, 13.4; IR (KBr, cm-1):
2962, 2929, 1683, 1634; LRMS (EI 70 ev) m/z (%): 295 (M+, 2), 105
1
6-Chloro-1-phenylhexane-1,2-dione (2h): Green oil; H NMR
(500 MHz, CDCl3) δ: 7.92 (d, J = 8.0 Hz, 2H), 7.58 (t, J = 7.5 Hz, 1H),
7.44 (t, J = 7.5 Hz, 2H), 3.51 (t, J = 6.0 Hz, 2H), 2.87 (t, J = 7.0 Hz,
2H), 1.82-1.79 (m, 4H);13C NMR (125 MHz, CDCl3) δ: 202.5, 192.0,
134.7, 131.8, 130.2, 128.9, 44.4, 37.7, 31.7, 20.2; IR (KBr, cm-1):
2958, 1708, 1668; LRMS (EI 70 ev) m/z (%): 226 (M++2, 1), 224 (M+, (37), 91 (100); HRMS m/z (ESI) calcd for C19H22NO2 [M+H]+
3), 105 (100), 77 (39), 51 (13); HRMS m/z (ESI) calcd for
296.1645, found 296.1657.
C12H1435ClO2 [M+H]+ 225.0677, found 225.0815.
Ethyl 2-oxo-2-phenylacetate (2s):16j Green oil; H NMR (500
1
1-Cyclopropyl-2-phenylethane-1,2-dione (2i):16e Green oil;
1H NMR (500 MHz, CDCl3) δ: 7.92 (d, J = 8.0 Hz, 2H), 7.56 (t, J = 7.5
Hz, 1H), 7.42 (t, J = 7.5 Hz, 2H), 2.49-2.46 (m, 1H), 1.27-1.24 (m,
2H), 1.14-1.11 (m, 2H);13C NMR (125 MHz, CDCl3) δ: 202.6, 192.3,
134.5, 132.1, 130.2, 128.8, 18.6, 13.2; IR (KBr, cm-1): 1691, 1675;
LRMS (EI 70 ev) m/z (%): 174 (M+, 2), 105 (100), 78 (4), 77 (48), 51
(19), 41 (21).
MHz, CDCl3) δ: 7.93 (d, J = 7.5 Hz, 2H), 7.57 (t, J = 7.5 Hz, 1H), 7.43
(t, J = 7.5 Hz, 2H), 4.40-4.35 (m, 2H), 1.34 (t, J = 7.0 Hz, 3H); 13
C
NMR (125 MHz, CDCl3) δ: 186.4, 163.8, 134.8, 132.3, 129.9, 128.8,
62.3, 14.0; IR (KBr, cm-1): 1736, 1683, 1200; LRMS (EI 70 ev) m/z
(%): 178 (M+, 1), 105 (100), 77 (48).
3-Hydroxy-1,3-diphenylprop-2-en-1-one (3a):16k Colorless oil;
1H NMR (500 MHz, CDCl3) δ: 16.92 (s, 1H), 8.01 (d, J = 7.5 Hz, 4H),
3,3-Dimethyl-1-phenylbutane-1,2-dione (2j):16c Green oil; 1H
NMR (500 MHz, CDCl3) δ: 7.75 (t, J = 8.5 Hz, 2H), 7.56 (t, J = 8.5 Hz,
1H), 7.42 (t, J = 8.0 Hz, 2H), 1.23 (s, 9H);13C NMR (125 MHz, CDCl3)
δ: 210.9, 195.4, 134.5, 132.8, 129.5, 128.9, 42.6, 26.2; IR (KBr,
cm-1): 2962, 1695, 1671; LRMS (EI 70 ev) m/z (%): 190 (M+, 2), 105
(100), 85 (6), 77 (35), 57 (33), 51 (13).
7.55 (d, J = 7.5 Hz, 2H), 7.49 (t, J = 7.5 Hz, 4H), 6.88 (s, 1H); 13
C
NMR (125 MHz, CDCl3) δ: 185.6, 135.3, 132.3, 128.5, 127.0, 93.0;
LRMS (EI 70 ev) m/z (%): 224 (M+, 65), 223 (80), 147 (38), 105
(100).
Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2018xxxxx.
1,2-Bis(4-methoxyphenyl)ethane-1,2-dione (2k):16a Yellow
oil; 1H NMR (500 MHz, CDCl3) δ 7.94 (d, J = 9.0 Hz, 4H), 6.96 (d, J =
9.0 Hz, 4H), 3.87 (s, 6H); 13C NMR (125 MHz, CDCl3) δ 193.5, 164.8,
132.3, 126.1, 114.2, 55.6; LRMS (EI, 70 eV) m/z (%): 270 (M+, 3),
207 (4), 135 (100), 92(28).
Acknowledgement
1-(4-Chlorophenyl)-2-phenylethane-1,2-dione (2l):16a Brown
1
solid, mp 82-83 oC (uncorrected); H NMR (500 MHz, CDCl3) δ:
We thank the National Natural Science Foundation of China
(Nos. 21625203 and 21871126) and the Opening Fund of
KLCBTCMR, Ministry of Education (No. KLCBTCMR18-02) for
financial support.
7.89 (d, J = 7.5 Hz, 2H), 7.85 (d, J = 8.5 Hz, 2H), 7.59 (t, J = 7.5 Hz,
1H), 7.46-7.40 (m, 4H);13C NMR (125 MHz, CDCl3) δ: 193.4, 192.5,
141.1, 134.6, 132.2, 130.8, 130.7, 129.4, 128.9, 128.6; IR (KBr,
cm-1): 1671, 1589; LRMS (EI 70 ev) m/z (%): 246 (M++2, 1), 244
(M+, 3), 139 (24), 111 (16), 105 (100), 77 (40), 75 (13), 51 (16).
References
1-(2-Chlorophenyl)-2-phenylethane-1,2-dione
(2m):16f
1
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4
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© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, XXX－XXX

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[13] (a) Phillips, F. C. Researches Upon the Phenomena of Oxidation and
Chemical Properties of Gases. Am. Chem. J. 1894, 16, 163–187; (b)
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Wacker Oxidation Mechanisms. J. Am. Chem. Soc. 2007, 129, 12342–
12343; (c) Keith, J. A.; Nielsen, R. J.; Oxgaard, J.; Goddard, W. A.
Inaccessibility of β-Hydride Elimination from −OH Functional Groups
in Wacker-Type Oxidation. J. Am. Chem. Soc. 2006, 128, 3132–3133;
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(The following will be filled in by the editorial staff)
Manuscript received: XXXX, 2019
Manuscript revised: XXXX, 2019
Manuscript accepted: XXXX, 2019
Accepted manuscript online: XXXX, 2019
Version of record online: XXXX, 2019
[14] The controlled experiments (eq S2 of Scheme S1 in Supporting
Information) show that CuBr2 as a catalyst takes part in the reaction
besides as an oxidant (another mechanism was proposed in Scheme
S2). Moreover, TEMPO is necessary in the reaction of 3a. A paper has
reported on an example of AlCl3 or Cu(OAc)2-mediated
decar-oxylation of 1,3-diphenylpropane-1,2,3-trione leading to benzil
2a, see: Robertsd, J. D.; Smith, D. R.; Lee, C. C. The Decarbonylation
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Chin. J. Chem. 2019, 37, XXX－XXX

Running title
Chin. J. Chem.
Entry for the Table of Contents
Page No.
Palladium-Catalyzed Oxidative CC Triple Bond
Cleavage of 2-Alkynyl Carbonyl Compounds
Toward 1,2-Dicarbonyl Compounds
New palladium-catalyzed oxidative strategy for the cleavage of the CC triple bond toward
1,2-dicarbonyl compounds, including 1,2-diones, 2-keto amides and 2-keto esters, is described, in
which H2O serves as the carbonyl oxygen atom source. This reaction is highlighted by its generality
with respective to a wide range of 2-alkynyl carbonyl compounds, The mechanism was discussed
according to the 13C-labeled and 18O-labeled experiments.
Ming-Bo Zhou,† Mu-Jia Luo,† Ming Hu, and
Jin-Heng Li*
Chin. J. Chem. 2019, 37, XXX－XXX
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