Transition-Metal- and Halogen-Free Oxidation of Benzylic sp 3 C-H Bonds to Carbonyl Groups Using Potassium Persulfate

Article abstract of DOI:10.1055/s-0036-1588429

Aryl carbonyl compounds including acetophenones, benzophenones, imides, and benzoic acids are prepared from benzyl substrates using potassium persulfate as oxidant with catalytic pyridine in acetonitrile under mild conditions. Neither transition metals nor halogens are involved in the reactions.

Full text of DOI:10.1055/s-0036-1588429

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2017, 49, A–J
paper
A
en
Y. Hu et al.
Paper
Synthesis
Transition-Metal- and Halogen-Free Oxidation of Benzylic sp3 C–H
Bonds to Carbonyl Groups Using Potassium Persulfate
O
Yixin Hu
Lihong Zhou
Wenjun Lu*
R
R'
29 examples
up to 89% yield
0
0
0
0
0-
0
0
1
8-
0
7
7
7-
0
6
0
R = Me, Ph, NHCOMe, etc.
R' = H, halogen, OMe, OAc, CO2Me, NO2, etc.
Department of Chemistry, Shanghai Jiao Tong University,
800 Dongchuan Road, Shanghai 200240, P. R. of China
luwj@sjtu.edu.cn
H
H
R
0.4 equiv
N
+ K2S2O8
2.0 equiv
O
R'
MeCN, O2 (1 atm)
70–80 °C, 16 h
OH
R'
13 examples
up to 91% yield
R = H, Et, iPr, etc.
R' = H, halogen, tBu, OMe, CO2Me, CF3, NO2
Received: 17.03.2017
Accepted after revision: 28.04.2017
Published online: 06.06.2017
involved to promote the reactions (Scheme 1). Meanwhile,
photoredox catalysis was also introduced successfully for
the formation of C–O bonds from benzylic sp3 C–H bonds.18
Despite this progress, there remains a demand to establish
an effective oxidation system excluding both transition
metal and halogen in the carbonylation of benzylic sp3 C–H
bonds.
Given that potassium persulfate has been successfully
applied as an effective and convenient oxidant in various
oxidative systems,19 it is our goal to develop a new method
utilizing potassium persulfate to avoid generating large
amounts of halogenated and metallic waste. Herein, we re-
port the oxidation of benzylic sp3 C–H bonds, promoted by
potassium persulfate alone, to afford the corresponding
carbonyl compounds smoothly under mild conditions. Vari-
ous N-benzylamides and alkylarenes, especially alkylarenes
DOI: 10.1055/s-0036-1588429; Art ID: ss-2017-h0168-op
Abstract Aryl carbonyl compounds including acetophenones, benzo-
phenones, imides, and benzoic acids are prepared from benzyl sub-
strates using potassium persulfate as oxidant with catalytic pyridine in
acetonitrile under mild conditions. Neither transition metals nor halo-
gens are involved in the reactions.
Key words potassium persulfate, oxidation, transition-metal-free,
halogen-free, benzylic sp3 C–H bond
Aromatic carbonyl compounds including aryl ketones,
aldehydes, acids, imides and their derivatives are funda-
mental intermediates of considerable interest for the pro-
duction of pharmaceuticals, insecticides, plasticizers, dyes,
perfumes, and other commercial specialty products.1a Usu-
ally, aromatic carbonyl compounds are prepared through
the classic Friedel–Crafts acylation, which is the reaction of
aryl C–H bonds with acylating reagents such as acyl halides
in the presence of a stoichiometric amount of Lewis acid.1a
Alternatively, aromatic carbonyl compounds can be pre-
pared through direct oxidation of benzylic C–H bonds,
which has been well utilized in organic synthesis.1b–d How-
ever, although the cleavage of benzylic sp3 C–H bonds is not
very difficult compared with that of normal alkyl sp3 C–H
bonds because benzylic intermediates are stabilized by res-
onance of the benzene rings, traditionally metal oxidants,
especially heavy metal oxidants, are often necessary and
are consumed stoichiometrically.2 With the demand of
green and sustainable chemistry, many metal-catalyzed ox-
idations3–16 or even metal-free oxidative processes17 have
been established over the past decade. In a few recent re-
ports on transition-metal-free oxidations of benzylic sp3 C–
H bonds, stoichiometric amounts of halogen element such
as hypervalent iodine17h or alkali metal bromide,17p,q were
Previous work by Kita (1), Moriyama and Togo (2):
[PhIO]n (3 equiv)
KBr (1 equiv)
O
O
(1)
(2)
Ar
Ar
R
R
Ar
Ar
R
R
montmorillonite-K10
H2O, 80 °C, 24 h
Oxone (1.2 equiv)
KBr (1.2 equiv)
CH2Cl2–H2O
r.t., visible light, 24 h
This work:
Ar
K2S2O8 (2 equiv)
pyridine (0.4 equiv)
O
(3)
R
Ar
R
MeCN, O2 (1 atm)
70–80 °C, 16 h
Scheme 1 Transition-metal-free oxidation of a benzylic sp3 C–H bond
to a carbonyl group
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

B
Y. Hu et al.
Paper
Synthesis
substituted by electron-withdrawing groups, are available
and this oxidation proceeds under heavy-metal- and halo-
gen-free conditions.
was established that MeCN was a good solvent compared
with EtOAc, THF, DCE, DMSO and toluene in this reaction
(entry 11–15).
Initially, the oxidation of N-benzylacetamide (1a) to
form N-acetylbenzamide (2a) was investigated by using
several common oxidizing reagents or initiators20 including
persulfates, Oxone, t-BuOOH (TBHP) (70% aq), H2O2 (30%
aq) and azobisisobutyronitrile (AIBN) (Table 1). The oxida-
tion reaction did not occur when only potassium persulfate
was used (entry 1). It was assumed that potassium persul-
fate was not soluble in the solution. Therefore, pyridine was
added to increase the solubility of potassium persulfate. To
our delight, in the presence of pyridine, three persulfates
were found to oxidize the substrate to imide (entries 2–4).
Among these persulfates, potassium persulfate K2S2O8 with
pyridine as a phase-transfer catalyst (PTC)21 exhibited a
high efficiency under air atmosphere (entry 2). In contrast,
Oxone, H2O2 and AIBN were not effective (entries 5, 7, and
8). Meanwhile, other persulfates with pyridine and TBHP
could be used to carry out the oxidation, albeit with low se-
lectivity (entries 3, 4, and 6). In the screening of solvent, it
After the loading of potassium persulfate and pyridine
was adjusted, N-acetylbenzamide (2a) was obtained in 71%
isolated yield at 70 °C under air for 16 hours (Table 2, entry
1). However, when the oxidation was conducted under oxy-
gen, 89% yield of 2a was obtained (entry 9). To understand
the role of pyridine in the reaction, we tested other com-
mon phase-transfer catalysts including two kinds of quater-
nary ammonium salt and PEG-400 (entries 3–5). Both n-
Bu4NOAc and PEG-400 were effective in this reaction,
whereas n-Bu4NHSO4 did not lead to the oxidation. Several
tertiary amines such as triethylamine, 1,4-diazabicyc-
lo[2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec-7-
ene (DBU) were also tested as PTC (entries 6–8). As a result,
pyridine was more useful than other PTCs in this oxidative
reaction. The reaction did not work in the presence of a
small amount of water (see the Supporting Information).
With the optimized conditions in hand, we next ex-
plored the scope of the reaction with respect to the sub-
strate. In the oxidation of various substituted N-benzyl-
amides (Scheme 2), the phenyl rings substituted by halo-
gens were tolerated, giving the corresponding products in
66–84% yields (2b–e). Those bearing a 4-Me, 4-OMe, or 4-
NO2 group afforded the N-acetylbenzamides 2f–h in yields
Table 1 Screening of Oxidants and Solventsa
O
O
O
oxidant, pyridine
N
N
H
H
MeCN, air (1 atm)
80 °C, 12 h
1a
2a
Table 2 Optimization of Reaction Conditions and PTCa
Entry Oxidant
(2 equiv)
Pyridine
(equiv)
Solvent
Conv.
(%)b
Yield
(%)b
O
O
O
K2S2O8, pyridine
N
N
1
2
K2S2O8
K2S2O8
Na2S2O8
–
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
EtOAc
DCE
N.R.
100
71
N.D.
79
H
H
MeCN, 70 °C, 16 h
0.2
0.2
0.2
0.2
–
1a
2a
3
21
Entry K2S2O8
PTC
(equiv)
Atmosphere Conv.
(%)b
Yield
(%)b
4
(NH4)2S2O8
Oxone
78
29
(equiv)
5
<5
trace
19
1
2
2.0
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
0.5
pyridine (0.8)
pyridine (0.4)
air
air
100
75 (71)
6
TBHP (75% aq)
TBHP (75% aq)
H2O2 (30% aq)
H2O2 (30% aq)
AIBN
48
97
68
65 (63)
49
7
0.2
–
33
29
3
n-Bu4NOAc (0.4) air
8
N.R.
N.R.
N.R.
N.R.
36
N.D.
N.D.
N.D.
N.D.
29
4
n-Bu4HSO4 (0.4)
PEG-400 (0.4)
Et3N (0.4)
air
N.R.
60
N.D.
50
9
0.2
–
5
air
10
11
12
13
14
15
6
air
71
57
K2S2O8
0.2
0.2
0.2
0.2
0.2
7
DABCO (0.4)
DBU (0.4)
air
N.R.
38
N.D.
26
K2S2O8
8
air
K2S2O8
toluene
DMSO
THF
N.R.
N.R.
N.R.
N.D.
N.D.
N.D.
9
pyridine (0.4)
pyridine (0.2)
pyridine (0.4)
oxygen
oxygen
oxygen
100
65
94 (89)
54
K2S2O8
10
11
K2S2O8
65
56
a Reaction conditions: 1a (0.5 mmol), oxidant (1.0 mmol, 2 equiv), MeCN
(2.0 mL), 80 °C, under air, sealed tube, 12 h.
a Reaction conditions: N-benzylacetamide (0.5 mmol), MeCN (1.0 mL),
under air, sealed tube, 16 h.
b Conversions and yields based on substrate and detected by 1H NMR analysis
in situ using CH2Br2 as an internal standard. N.R. = no reaction; N.D. = not
determined.
b Yields based on substrate and detected by 1H NMR analysis in situ using
CH2Br2 as an internal standard, isolated yield given in parentheses.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

C
Y. Hu et al.
Paper
Synthesis
good yields (4q–s). However, the oxidation of 1-benzyl-4-
methylbenzene (3t) proceeded in a low yield of 45%.
O
O
O
K2S2O8 (2.0 equiv)
pyridine (0.4 equiv)
N
R
N
R
R'
H
R'
H
MeCN, O2 (1 atm)
70 °C, 16 h
In the case of toluene (5a), benzoic acid (6a) was ob-
served in low yield (36%) under air. The yield increased to
80% when the reaction was conducted under an oxygen at-
mosphere at 80 °C (see the Supporting Information). Deriv-
atives of toluene were also available in the oxidation to af-
ford the corresponding benzoic acids in good yields
(Scheme 4). Benzoic acids bearing halogen and electron-
withdrawing groups (6b–h) were obtained in good yields.
4-tert-Butylbenzoic acid (6i) was obtained in 90% yield,
whereas 4-methoxytoluene (5g) only gave 4-methoxyben-
zoic acid (6j) in a yield of 34% when 0.2 mmol pyridine was
utilized. However, the yield increased to 68% when 0.8
mmol (1.6 equiv) pyridine was used. In the presence of 4
1
2
O
O
O
O
O
O
Cl
N
N
N
H
H
H
F
2a 89%[a]
2b 66%
2c 74%
O
O
O
O
O
O
N
N
N
H
H
H
Cl
Br
O2N
2d 84%
2e 84%
2f 43%
O
O
O
O
O
O
N
H
N
N
H
H
O
MeO
O
K2S2O8 (2.0 equiv)
pyridine (0.4 equiv)
2g 45%
2h 46%[b]
2i 60%
R'
R'
R
O
R
MeCN, O2 (1 atm)
80 °C, 16 h
O
O
O
4
3
N
N
H
H
O
O
O
2k 73%
2j 68%
Scheme 2 Reagents and conditions: substrate (0.5 mmol), K2S2O8 (1.0
mmol, 2 equiv), pyridine (0.2 mmol, 0.4 equiv), MeCN (1.0 mL), 70 °C,
under O2, sealed tube, 16 h. Isolated yield. a K2S2O8 (0.6 mmol, 1.2
equiv). b Pyridine (0.8 mmol, 1.6 equiv).
Br
Ac
Ph
MeO2C
4c 73%
AcO
4a 89%
4b 70%
4f 70%
4j 62%
4d 69%
O
O
O
O
O
O2N
MeO
4h 72%b
4g 39%a
4e 71%
of only 43, 45, or 46%, respectively. Moderate yields were
found for substrates with different acyl groups (2i–k; 60–
73%).
O
O
O
The scope of the reaction was also extended to carbon-
ylations of normal alkylarenes by using the K2S2O8/pyridine
oxidative system (Scheme 3). In a study of the oxidizing
conditions for ethylbenzene, K2S2O8 was still the sole effec-
tive oxidant in the reaction (see the Supporting Informa-
tion). Moreover, ethylbenzenes substituted by a 4-Br (3b),
4-CO2Me (3c), 4-OAc (3d), 4-NO2 (3e), 4-Ac (3f), or 4-OMe
(3h) group provided the corresponding acetophenones in
69–73% yield. 1-Ethoxy-4-ethylbenzene (3i) and 4-ethyl-
1,1′-biphenyl (3j) gave 53 and 62% yield, respectively. More
pyridine (1.6 equiv) was needed to obtain higher yields of
products containing an alkyloxy group (4h, 4i), as in the
case of N-(4-methoxybenzyl)acetamide (1h).
EtO
4k 40%
benzoic acid (60%)
4l 25%
4i 53%b
benzoic acid (64%)
O
O
O
O
4m 33%
benzoic acid (59%)
4n 53%c
4o 41%c
4p 66%
O
O
Cl
4q 75%
4r 82%
O
O
However, when the alkyl group was a long chain, the
yield of ketone reduced because the chain was broken (4k–
m), and benzoic acid was the major byproduct. The oxida-
tions of indan (3n) and 1,2,3,4-tetrahydronaphthalene (3o)
were also tested. Mono-oxidative product 1-indanone (4n)
or 1-tetralone (4o) was obtained in 53 or 41% yield. Fluo-
rene (3p) was converted into 9-fluorenone (4p) in 66%
yield. Diarylmethanes (3q–s) also underwent the oxida-
tions well, forming the corresponding benzophnone in
OMe
4s 77%b
4t 45%c
Scheme 3 Reagents and conditions: substrate (0.5 mmol), K2S2O8 (1.0
mmol, 2 equiv), pyridine (0.2 mmol, 0.4 equiv), MeCN (1.0 mL), 80 °C,
under O2, 16 h. Isolated yield. Yields based on substrate and detected by
1H NMR analysis in situ using CH2Br2 as an internal standard given in pa-
rentheses. a 70 °C, under air. b Pyridine (0.8 mmol). c 60 °C.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

D
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Synthesis
carbon–carbon double bond.22 Oxidation of cumene to af-
ford acetophenone as the final oxidative product implies
that α-methylstyrene might be formed during the process.
K2S2O8 (2.0 equiv)
pyridine (0.4 equiv)
CH3
CO2H
R
R
MeCN, O2 (1 atm)
80 °C, 16 h
5
6
O
K2S2O8 (2.0 equiv)
pyridine (0.4 equiv)
CO2H
Cl
(1)
CO2H
CO2H
TEMPO or BHT
(2.0 equiv)
MeCN, O2 (1 atm)
80 °C, 16 h
Cl
not detected
6a 80%
CO2H
6b 81%
6c 77%
6f 64%
CO2H
CO2H
CO2H
O
K2S2O8 (2.0 equiv)
pyridine (0.4 equiv)
O2N
Cl
Br
6d 84%
6e 78%
(2)
MeCN, O2 (1 atm)
80 °C, 16 h
conv. 85%
1H-NMR yield 76%
CO2H
CO2H
MeO2C
F3C
t-Bu
O
6h 72%
6i 90%
6g 91%
K2S2O8 (2.0 equiv)
pyridine (0.4 equiv)
(3)
CO2H
CO2H
MeCN, O2 (1 atm)
80 °C, 16 h
conv. 100%
HO2C
MeO
1H-NMR yield 62%
6k 34%b
51%c
6j 68%a
Scheme 6 Mechanistic study of the direct oxidation of a benzylic C–H
bond
Scheme 4 Reagents and conditions: substrate (0.5 mmol), K2S2O8 (1.0
mmol, 2 equiv), pyridine (0.2 mmol, 0.4 equiv), MeCN (1.0 mL), 80 °C,
under O2, 16 h. Isolated yield. a Pyridine (0.8 mmol, 1.6 equiv). b p-Xy-
lene as substrate, K2S2O8 (2.0 mmol, 4 equiv). c p-Xylene as substrate,
K2S2O8 (2.0 mmol, 4 equiv), pyridine (1.2 mmol, 2.4 equiv).
To understand the side reaction of the oxidation of alk-
ylbenzene, octylbenzenene was tested under the standard
conditions (Scheme 7). Three main products including oc-
tanophenone, benzoic acid, and heptanoic acid were de-
tected by LC-MS (see the Supporting Information). These
results reveal that the carbon radical intermediate formed
from the olefin followed by rapid oxidation to carbonyl
compounds such as ketones and carboxylic acids through
oxidative cleavage of the double bond.22 On the basis of our
equivalents potassium persulfate and 2.4 equivalents pyri-
dine, p-xylene was oxidized to p-phthalic acid (6k) in a
yield of 54%.
A scale-up experiment was conducted to demonstrate
the practicality of this oxidation reaction. 1,4-Diacetylben-
zene (4f) could be obtained in 62% yield under the standard
conditions with 19% recovery of 1,4-diethylbenzene (3f)
(Scheme 5).
experiments and previous reports, a possible mechanism is
·–
depicted in Scheme 8. Initially, a sulfate radical anion (SO4
)
is generated by pyrolysis of K2S2O8, which abstracts a ben-
zyl hydrogen atom to form benzyl radical intermediate A
with the assistance of pyridine as PTC. Intermediate A is fi-
nally oxidized to the desired ketone C via peroxide interme-
diate B under a dioxygen atmosphere.17w K2S2O8 could also
provide dioxygen in these reactions.23 On the other hand,
benzyl radical intermediate A is also further oxidized to cat-
O
O
K2S2O8 (2.0 equiv)
pyridine (0.4 equiv)
MeCN, O2
80 °C, 18 h
1.54 g (10 mmol)
O
4f 62% yield
Scheme 5 Gram-scale preparation of 1,4-diacetylbenzene
O
C7H15
In a study of the mechanism, no product was detected
in the oxidation of ethylbenzene when either 2,2,6,6-te-
tramethylpiperidine-1-oxyl (TEMPO) or 2,6-di-tert-butyl-
4-methylphenol (BHT) was added to the reaction (see the
Supporting Information; Scheme 6, eq. 1), indicating that a
radical process was probably involved. Oxidation of cumene
and α-methyl-styrene both afforded acetophenone as the
major product in 76 and 67% yield, respectively (Scheme 6,
eqs. 2 and 3). It has been reported that α-methylstyrene
can be oxidized to acetophenone through cleavage of the
+
K2S2O8 (2.0 equiv)
C8H17
COOH
pyridine (0.4 equiv)
MeCN, O2, 80 °C, 16 h
+
COOH
detected by LC-MS
Scheme 7 Oxidation of octylbenzene
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

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Synthesis
13C NMR (100 MHz, CDCl3): δ = 174.1, 166.1, 133.5, 132.9, 129.2,
R
128.0, 25.9.
IR (KBr): 3276, 1738, 1679, 1511, 1488, 1284, 1219, 706 cm–1
.
.–
2–
SO4
S2O8
N-Acetyl-4-fluorobenzamide (2b)26
Yield: 59.4 mg (66%); white solid; mp 112–113 °C (Lit.26 111–112 °C).
OOH
O
O2
R
R
R
1H NMR (400 MHz, CDCl3): δ = 8.78 (br, 1 H), 7.91 (m, 2 H), 7.20 (t, J =
8.4 Hz, 2 H), 2.62 (s, 3 H).
A
B
C
13C NMR (100 MHz, CDCl3): δ = 174.4, 167.2, 165.1, 164.7, 130.8,
.–
SO4
130.7, 129.0, 116.5, 116.2, 25.9.
19F NMR (376 MHz, CDCl3): δ = –104.6.
R
CO2H
– H+
[O]
R
IR (KBr): 3292, 1716, 1696, 1608, 1467, 1373, 1299, 1239, 1163, 1025,
D
E
F
858 cm–1
.
Scheme 8 A possible mechanism
N-Acetyl-3-chlorobenzamide (2c)20a
Yield: 73.6 mg (74%); white solid; mp 113–114 °C (Lit.26 113–115 °C).
ion intermediate D by the sulfate radical,19a which forms
alkene E immediately, followed by oxidation to benzoic acid
F in the presence of dioxygen and sulfate radicals.22 This ex-
plains the low yield of ketones in the oxidation of the long-
chain alkylbenzenes such as n-propylbenzene.
In summary, a green and convenient method has been
established to prepare benzyl carbonyl compounds through
direct oxidation of benzylic sp3 C–H bonds. In this oxidative
system, K2S2O8 is an effective oxidant when pyridine plays a
role of PTC. Neither transition metal nor halogen is involved
in the processes. The procedure is suitable for a wide range
of benzyl substrates, most of which are converted into the
corresponding carbonyl compounds in good yields under
mild conditions.
1H NMR (400 MHz, CDCl3): δ = 8.73 (br, 1 H), 7.87 (s, 1 H), 7.72 (d, J =
7.6 Hz, 1 H), 7.59 (d, J = 8.0 Hz, 1 H), 7.46 (t, J = 8.0 Hz, 1 H), 2.62 (s,
3 H).
13C NMR (100 MHz, CDCl3): δ = 174.3, 164.8, 135.5, 134.6, 133.5,
130.5, 128.5, 126.0, 25.9.
IR (KBr): 3293, 1716, 1691, 1667, 1456, 1297, 1246, 1024, 731 cm–1
.
N-Acetyl-4-chlorobenzamide (2d)20a
Yield: 83 mg (84%); white solid; mp 135–136 °C (Lit.26 136–137 °C).
1H NMR (400 MHz, CDCl3): δ = 8.51 (br, 1 H), 7.79 (d, J = 8.8 Hz, 2 H),
7.50 (d, J = 8.8 Hz, 2 H), 2.62 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 174.3, 165.1, 140.0, 131.2, 129.5, 25.9.
IR (KBr): 3265, 1710, 1693, 1594, 1469, 1374, 1279, 1247, 1096, 1020,
752 cm–1
.
N-Acetyl-4-bromobenzamide (2e)27
Yield: 101.1 mg (84%); white solid; mp 180–182 °C (Lit.28 152–
1H NMR spectra were obtained with a Varian Mercury 400 plus (400
MHz for 1H NMR) instrument. Infrared (IR) data were recorded with
an AVATAR 370 spectrometer as a thin film on a KBr plate. All re-
agents were obtained from commercial sources. Solvents were dis-
tilled before use. Flash chromatography was performed on silica gel
(200–300 mesh).
154 °C).
1H NMR (400 MHz, CDCl3): δ = 8.86 (br, 1 H), 7.75 (d, J = 8.4 Hz, 2 H),
7.66 (d, J = 8.4 Hz, 2 H), 2.61 (s, 3 H).
13C NMR (100 MHz, DMSO-d6): δ = 172.8, 166.4, 133.0, 132.2, 131.1,
127.3, 26.2.
IR (KBr): 3259, 1680, 1588, 1428, 1321, 1178, 1013, 758 cm–1
.
Procedures
Details of the preparation of substrates are provided in the Support-
ing Information.
N-Acetyl-4-nitrobenzamide (2f)29
Yield: 44.7 mg (43%); yellow solid; mp 221–223 °C (Lit.28 225–
227 °C).
Oxidation of N-Benzylamides; Typical Procedure for N-Acetyl-
benzamide (2a)24
1H NMR (400 MHz, CDCl3): δ = 11.30 (br, 1 H), 8.33 (d, J = 8.8 Hz, 2 H),
8.10 (d, J = 8.4 Hz, 2 H), 2.35 (s, 3 H).
13C NMR (100 MHz, DMSO-d6): δ = 172.6, 166.1, 150.3, 139.7, 130.5,
N-Benzylacetamide (1a; 0.0746 g, 0.5 mmol), K2S2O8 (0.1622 g, 0.6
mmol), MeCN (1.0 mL) and pyridine (0.0158 g, 0.2 mmol) were added
to an oven-dried pressure vessel with a magnetic stir bar. The pres-
sure vessel was filled with dioxygen and the reaction mixture was
stirred at 70 °C for 16 h (oil bath). Upon completion of the reaction,
the solvent was evaporated and the reaction mixture was purified by
column chromatography (EtOAc/PE, 1:4) to give N-acetylbenzamide
(2a).
Yield: 73 mg (89%); white solid; mp 115–116 °C (Lit.25 115–117 °C).
1H NMR (400 MHz, CDCl3): δ = 9.36 (br, 1 H), 7.92 (d, J = 7.2 Hz, 2 H),
7.60 (t, J = 7.2 Hz, 1 H), 7.50 (t, J = 8.0 Hz, 2 H), 2.61 (s, 3 H).
124.1, 26.2.
IR (KBr): 3278, 1736, 1531, 1488, 1356, 1324, 1277, 1219, 1103,
714 cm–1
.
N-Acetyl-4-methylbenzamide (2g)30
Yield: 39.8 mg (45%); white solid; mp 106–107 °C (Lit.26 111–113 °C).
1H NMR (400 MHz, CDCl3): δ = 8.56 (br, 1 H), 7.74 (d, J = 8.0 Hz, 2 H),
7.31 (d, J = 8.4 Hz, 2 H), 2.62 (s, 3 H), 2.44 (s, 3 H).
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13C NMR (100 MHz, CDCl3): δ = 174.1, 165.9, 144.3, 129.9, 129.4,
4-Bromoacetophenone (4b)17p
Yield: 69.6 mg (70%); white solid; mp 45–46 °C (Lit.17m 46–47 °C).
128.0, 25.8, 21.9.
1H NMR (400 MHz, CDCl3): δ = 7.83 (d, J = 8.8 Hz, 2 H), 7.61 (d, J =
8.8 Hz, 2 H), 2.59 (s, 3 H).
IR (KBr): 3258, 1714, 1691, 1525, 1473, 1374, 1319, 1283, 1096, 1015,
748 cm–1
.
13C NMR (100 MHz, CDCl3): δ = 197.2, 135.9, 132.1, 130.0, 128.5, 26.7.
N-Acetyl-4-methoxybenzamide (2h)30
Yield: 44.3 mg (46%); white solid; mp 115–116 °C (Lit.31 119–
IR (KBr): 1675, 1586, 1391, 1270, 1078 cm–1
.
119.5 °C).
Methyl 4-Acetylbenzoate (4c)17p
Yield: 65 mg (73%); white solid; mp 91–92 °C (Lit.32 95.2–95.4 °C).
1H NMR (400 MHz, CDCl3): δ = 8.13 (d, J = 8.8 Hz, 2 H), 8.01 (d, J =
8.8 Hz, 2 H), 3.96 (s, 3 H), 2.65 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 197.8, 166.4, 140.4, 134.1, 130.0,
128.4, 52.7, 27.1.
IR (KBr): 1722, 1678, 1437, 1284, 1113, 770 cm–1
1H NMR (400 MHz, CDCl3): δ = 8.75 (br, 1 H), 7.84 (d, J = 9.2 Hz, 2 H),
6.98 (d, J = 8.8 Hz, 2 H), 3.88 (s, 3 H), 2.61 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 173.9, 165.2, 163.8, 130.1, 124.9,
114.4, 55.8, 25.8.
IR (KBr): 3236, 1715, 1696, 1608, 1475, 1279, 1255, 1177, 1028, 829,
756 cm–1
.
.
N-Propionylbenzamide (2i)24
Yield: 53.5 mg (60%); white solid; mp 93–94 °C (Lit.25 97–99 °C).
1H NMR (400 MHz, CDCl3): δ = 8.54 (br, 1 H), 7.84 (d, J = 7.2 Hz, 2 H),
7.61 (t, J = 7.6 Hz, 1 H), 7.51 (t, J = 8.0 Hz, 2 H), 3.04 (q, J = 7.2 Hz, 2 H),
1.23 (t, J = 7.6 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 177.8, 166.0, 133.3, 133.0, 129.1,
128.0, 31.5, 8.4.
IR (KBr): 3289, 1712, 1682, 1471, 1369, 1245, 1209, 709 cm–1
4-Acetoxyacetophenone (4d)17p
Yield: 61.4 mg (69%); white solid; mp 46–47 °C.
1H NMR (400 MHz, CDCl3): δ = 7.99 (d, J = 8.4 Hz, 2 H), 7.19 (d, J =
8.8 Hz, 2 H), 2.59 (s, 3 H), 2.32 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 197.1, 169.1, 154.6, 134.9, 130.2,
122.0, 26.8, 21.4.
IR (neat): 1760, 1683, 1598, 1265, 1195, 789 cm–1
.
.
4-Nitroacetophenone (4e)17p
Yield: 59 mg (71%); white solid; mp 79–80 °C (Lit.17m 80–81 °C).
1H NMR (400 MHz, CDCl3): δ = 8.32 (d, J = 9.2 Hz, 2 H), 8.11 (d, J =
9.2 Hz, 2 H), 2.68 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 196.5, 150.4, 141.6, 129.5, 124.1, 27.2.
IR (KBr): 1694, 1608, 1527, 1319, 1261, 1243, 856, 747 cm–1
N-Pivaloylbenzamide (2j)24
Yield: 69 mg (68%); white solid; mp 125–126 °C.
1H NMR (400 MHz, CDCl3): δ = 8.55 (br, 1 H), 7.75 (d, J = 8.0 Hz, 2 H),
7.59 (t, J = 7.6 Hz, 1 H), 7.49 (t, J = 7.2 Hz, 2 H), 1.33 (s, 9 H).
13C NMR (100 MHz, CDCl3): δ = 176.3, 166.7, 134.0, 133.1, 129.0,
127.9, 40.1, 27.4.
.
IR (KBr): 3309, 1734, 1683, 1506, 1481, 1134, 708 cm–1
.
1,4-Diacetylbezene (4f)33
N-Benzoylbenzamide (2k)24
Yield: 82.4 mg (73%); white solid; mp 144–145 °C (Lit.25 146–148 °C).
1H NMR (400 MHz, CDCl3): δ = 8.92 (br, 1 H), 7.88 (d, J = 7.2 Hz, 4 H),
7.62 (t, J = 7.6 Hz, 2 H), 7.52 (t, J = 8.0 Hz, 4 H).
13C NMR (100 MHz, CDCl3): δ = 166.8, 133.6, 133.3, 129.1, 128.2.
Yield: 56.6 mg (70%); white solid; mp 111–112 °C (Lit.34 110–112 °C).
1H NMR (400 MHz, CDCl3): δ = 8.04 (s, 4 H), 2.65 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 197.7, 140.3, 128.7, 27.2.
IR (KBr): 1677, 1401, 1355, 1309, 1256, 952, 835 cm–1
.
IR (KBr): 3250, 1706, 1582, 1505, 1476, 1228, 1178, 1118, 1073, 1026,
4-Methylacetophenone (4g)33
710 cm–1
.
Yield: 26.4 mg (39%); yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.86 (d, J = 8.0 Hz, 2 H), 7.26 (d, J =
8.0 Hz, 2 H), 2.58 (s, 3 H), 2.41 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 198.1, 144.1, 134.8, 129.5, 128.7, 26.8,
Oxidation of Alkylbenzenes and Toluene; Typical Procedure for
Acetophenone (4a)17p
Ethylbenzene (3a; 0.0531 g, 0.5 mmol), K2S2O8 (0.2703 g, 1.0 mmol),
pyridine (0.0158 g, 0.2 mmol) and MeCN (1.0 mL) were added to an
oven-dried pressure vessel with a magnetic stir bar. The pressure ves-
sel was filled with dioxygen and the reaction mixture was stirred at
80 °C for 16 h (oil bath). Upon completion of the reaction, the solvent
was evaporated and the reaction mixture was purified by column
chromatography (EtOAc/PE, 1:10) to give acetophenone (4a).
21.9.
IR (neat): 1682, 1607, 1269, 1182, 815 cm–1
.
4-Methoxyacetophenone (4h)33
Yield: 54.3 mg (72%); white solid; mp 37–38 °C (Lit.17m 38–39 °C).
1H NMR (400 MHz, CDCl3): δ = 7.95 (d, J = 8.8 Hz, 2 H), 6.94 (d, J =
Yield: 53.5 mg (89%); colorless oil.
9.2 Hz, 2 H), 3.88 (s, 3 H), 2.57 (s, 3 H).
1H NMR (400 MHz, CDCl3): δ = 7.97 (d, J = 8.4 Hz, 2 H), 7.57 (t, J =
8.0 Hz, 1 H), 7.47 (t, J = 7.2 Hz, 2 H), 2.62 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 197.0, 163.7, 130.8, 130.5, 113.9, 55.7,
26.6.
13C NMR (100 MHz, CDCl3): δ = 198.4, 137.3, 133.3, 128.8, 128.5, 26.8.
IR (KBr): 1676, 1602, 1359, 1260, 1173, 1028, 835 cm–1
.
IR (neat): 1685, 1632, 1513, 1385, 1266, 1117, 768 cm–1
.
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Synthesis
1-(4-Ethoxyphenyl)ethanone (4i)35
1-Tetralone (4o)17d
Yield: 43.6 mg (53%); white solid; mp 37–38 °C (Lit.36 38–39 °C).
Yield: 30 mg (41%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 7.93 (d, J = 8.8 Hz, 2 H), 6.92 (d, J =
8.8 Hz, 2 H), 4.10 (q, J = 7.2 Hz, 2 H), 2.56 (s, 3 H), 1.45 (t, J = 6.8 Hz,
3 H).
1H NMR (400 MHz, CDCl3): δ = 8.04 (d, J = 7.6 Hz, 1 H), 7.48 (t, J =
7.6 Hz, 1 H), 7.31 (t, J = 7.6 Hz, 1 H), 7.26 (d, J = 7.6 Hz, 1 H), 2.98 (t, J =
6.0 Hz, 2 H), 2.67 (t, J = 6.4 Hz, 2 H), 2.15 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 197.0, 163.1, 130.8, 130.3, 114.3, 64.0,
13C NMR (100 MHz, CDCl3): δ = 198.6, 144.7, 133.6, 132.8, 129.0,
26.6, 15.0.
127.4, 126.8, 39.4, 29.9, 23.5.
IR (KBr): 1676, 1602, 1359, 1307, 1255, 1173, 1117, 1043, 840 cm–1
.
IR (neat): 1679, 1600, 1324, 1284, 1140, 765 cm–1
.
4-Acetylbiphenyl (4j)37
9-Fluorenone (4p)17d
Yield: 60.7 mg (62%); white solid; mp 116–117 °C (Lit.37 110–111 °C).
Yield: 59.2 mg (66%); yellow solid; mp 81–83 °C (Lit.17m 84–86 °C).
1H NMR (400 MHz, CDCl3): δ = 8.04 (d, J = 8.4 Hz, 2 H), 7.69 (d, J =
8.4 Hz, 2 H), 7.63 (d, J = 7.2 Hz, 2 H), 7.48 (t, J = 7.2 Hz, 2 H), 7.40 (t, J =
7.6 Hz, 1 H), 2.64 (s, 3 H).
1H NMR (400 MHz, CDCl3): δ = 7.66 (d, J = 7.2 Hz, 2 H), 7.50 (m, 4 H),
7.30 (t, J = 7.2 Hz, 2 H).
13C NMR (100 MHz, CDCl3): δ = 194.1, 144.5, 134.9, 134.3, 129.3,
13C NMR (100 MHz, CDCl3): δ = 198.0, 146.0, 140.1, 136.0, 129.2,
124.5, 120.5.
129.2, 128.5, 127.5, 127.5, 26.9.
IR (KBr): 1681, 1602, 1404, 1264, 961, 835 cm–1
IR (KBr): 1715, 1611, 1599, 1450, 1298, 1150, 918, 735 cm–1
.
.
Benzophenone (4q)17p
Yield: 68 mg (75%); white solid; mp 47–48 °C (Lit.17m 47–49 °C).
Propiophenone (4k)38
Yield: 21.4 mg (32%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 7.81 (d, J = 7.2 Hz, 4 H), 7.59 (t, J =
7.2 Hz, 2 H), 7.48 (t, J = 7.6 Hz, 4 H).
13C NMR (100 MHz, CDCl3): δ = 197.0, 137.8, 132.7, 130.3, 128.5.
1H NMR (400 MHz, CDCl3): δ = 7.97 (d, J = 7.2 Hz, 2 H), 7.55 (t, J =
7.6 Hz, 1 H), 7.46 (t, J = 8.0 Hz, 2 H), 3.01 (q, J = 7.2 Hz, 2 H), 1.23 (t, J =
7.2 Hz, 3 H).
IR (KBr): 1652, 1594, 1448, 1322, 1279, 1175, 918, 705 cm–1
.
13C NMR (100 MHz, CDCl3): δ = 201.0, 137.1, 133.1, 128.8, 128.2, 32.0,
8.5.
4-Chlorobenzophenone (4r)39
Yield: 89.1 mg (82%); white solid; mp 71–72 °C (Lit.40 73–74 °C).
IR (neat): 1686, 1601, 1256, 1221, 1174 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 7.77 (m, 4 H), 7.61 (t, J = 7.6 Hz, 1 H),
7.49 (m, 4 H).
13C NMR (100 MHz, CDCl3): δ = 195.7, 139.1, 137.4, 136.1, 132.9,
131.7, 130.2, 128.9, 128.6.
Isobutyrophenone (4l)17p
Yield: 14.8 mg (20%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 7.96 (d, J = 7.2 Hz, 2 H), 7.55 (t, J =
7.2 Hz, 1 H), 7.47 (t, J = 8.0 Hz, 2 H), 3.56 (m, 1 H), 1.22 (d, J = 6.8 Hz,
6 H).
IR (KBr): 1650, 1585, 1284, 1089, 844 cm–1
.
13C NMR (100 MHz, CDCl3): δ = 204.7, 136.4, 133.0, 128.8, 128.5, 35.6,
19.4.
4-Methoxybenzophenone (4s)41
Yield: 81.8 mg (77%); white solid; mp 57–58 °C (Lit.40 59–60 °C).
1H NMR (400 MHz, CDCl3): δ = 7.83 (d, J = 8.4 Hz, 2 H), 7.75 (d, J =
7.2 Hz, 2 H), 7.56 (t, J = 7.2 Hz, 1 H), 7.47 (t, J = 7.6 Hz, 2 H), 6.96 (d, J =
8.4 Hz, 2 H), 3.88 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 195.8, 163.5, 138.5, 132.8, 132.1,
130.3, 130.0, 128.4, 113.8, 55.7.
IR (KBr): 1650, 1599, 1319, 1262, 1170, 1024, 844 cm–1
IR (neat): 1684, 1465, 1383, 1225, 1161, 1015 cm–1
.
Butyrophenone (4m)17p
Yield: 20 mg (27%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 7.96 (d, J = 7.2 Hz, 2 H), 7.55 (t, J =
7.2 Hz, 1 H), 7.46 (t, J = 7.6 Hz, 2 H), 2.95 (t, J = 7.2 Hz, 2 H), 1.78 (m,
2 H), 1.01 (t, J = 7.2 Hz, 3 H).
.
13C NMR (100 MHz, CDCl3): δ = 200.7, 137.3, 133.1, 128.8, 128.3, 40.7,
18.0, 14.1.
4-Methybenzophenone (4t)39
Yield: 44.3 mg (45%); white solid; mp 51–52 °C (Lit.40 56–57 °C).
1H NMR (400 MHz, CDCl3): δ = 7.78 (d, J = 6.8 Hz, 2 H), 7.73 (d, J =
8.0 Hz, 2 H), 7.58 (t, J = 7.2 Hz, 1 H), 7.48 (t, J = 8.0 Hz, 2 H), 7.28 (d, J =
8.0 Hz, 2 H), 2.45 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 196.7, 143.5, 138.2, 135.1, 132.4,
130.5, 130.2, 129.2, 128.4, 21.9.
IR (KBr): 1655, 1605, 1280, 936, 732 cm–1
IR (neat): 1688, 1599, 1449, 1275, 1214, 1180 cm–1
.
1-Indanone (4n)17d
Yield: 34.9 mg (53%); white solid; mp 39–40 °C (Lit.17m 40–42 °C).
1H NMR (400 MHz, CDCl3): δ = 7.77 (d, J = 7.6 Hz, 1 H), 7.60 (t, J =
7.6 Hz, 1 H), 7.49 (d, J = 6.8 Hz, 1 H), 7.38 (t, J = 8.0 Hz, 1 H), 3.16 (t, J =
5.6 Hz, 2 H), 2.71 (t, J = 5.6 Hz, 2 H).
.
13C NMR (100 MHz, CDCl3): δ = 207.2, 155.4, 137.2, 134.8, 127.5,
126.9, 123.9, 36.5, 26.0.
Benzoic Acid (6a)42
Yield: 48.8 mg (80%); white solid; mp 120–121 °C (Lit.17m 122–
IR (KBr): 1706, 1612, 1328, 1277, 1204, 1174, 772 cm–1
.
124 °C).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

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Y. Hu et al.
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1H NMR (400 MHz, CDCl3): δ = 8.13 (d, J = 7.2 Hz, 2 H), 7.62 (t, J =
7.6 Hz, 1 H), 7.49 (t, J = 8.0 Hz, 2 H).
13C NMR (100 MHz, CDCl3): δ = 172.9, 134.1, 130.5, 129.6, 128.7.
p-Trifluoromethylbenzoic Acid (6h)42
Yield: 68.5 mg (72%); white solid; mp 186–187 °C (Lit.45 220–222 °C).
1H NMR (400 MHz, CDCl3): δ = 8.23 (d, J = 8.0 Hz, 2 H), 7.76 (d, J =
8.4 Hz, 2 H).
IR (KBr): 1687, 1424, 1326, 1293, 935, 708 cm–1
.
13C NMR (100 MHz, DMSO-d6): δ = 166.9, 135.2, 133.3, 133.0, 130.8,
126.3.
o-Chlorobenzoic Acid (6b)38
Yield: 63.4 mg (81%); white solid; mp 132–133 °C (Lit.43 138–140 °C).
IR (KBr): 1700, 1429, 1317, 1289, 1173, 1143, 1063, 863 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.02 (d, J = 6.8 Hz, 1 H), 7.49 (m, 2 H),
19F NMR (376 MHz, DMSO-d6): δ = –61.6.46
7.36 (m, 1 H).
13C NMR (100 MHz, CDCl3): δ = 171.0, 135.0, 133.8, 132.7, 131.7,
p-tert-Butylbenzoic Acid (6i)47
Yield: 80.9 mg (90%); white solid; mp 163–164 °C (Lit.17m 160–
161 °C).
128.6, 126.9.
IR (KBr): 1691, 1317, 1268, 1176, 1052, 745 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.04 (d, J = 8.8 Hz, 2 H), 7.49 (d, J =
8.4 Hz, 2 H), 1.35 (s, 9 H).
m-Chlorobenzoic Acid (6c)38
Yield: 60.6 mg (77%); white solid; mp 151–152 °C (Lit.43 155–157 °C).
13C NMR (100 MHz, DMSO-d6): δ = 167.9, 156.4, 129.9, 128.7, 126.0,
1H NMR (400 MHz, CDCl3): δ = 8.00 (d, J = 7.6 Hz, 1 H), 7.61 (m, 1 H),
7.59 (m, 1 H), 7.43 (t, J = 8.0 Hz, 1 H).
35.4, 31.5.
IR (KBr): 2966, 1686, 1610, 1422, 1288, 1188, 856 cm–1
.
13C NMR (100 MHz, CDCl3): δ = 171.1, 134.9, 134.2, 131.1, 130.5,
130.1, 128.6.
p-Methoxybenzoic Acid (6j)42
Yield: 51.7 mg (68%); white solid; mp 180–181 °C (Lit.45 182–184 °C).
IR (KBr): 1697, 1417, 1304, 1263, 750 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.07 (d, J = 8.8 Hz, 2 H), 6.95 (d, J =
8.8 Hz, 2 H), 3.88 (s, 3 H).
p-Chlorobenzoic Acid (6d)42
Yield: 65.8 mg (84%); white solid; mp 215–216 °C (Lit.17m 236–
13C NMR (100 MHz, DMSO-d6): δ = 167.7, 163.5, 132.0, 123.6, 114.5,
237 °C).
56.1.
1H NMR (400 MHz, CDCl3): δ = 8.04 (d, J = 8.4 Hz, 2 H), 7.46 (d, J =
IR (KBr): 1687, 1605, 1428, 1305, 1263, 1168, 1027, 845 cm–1
.
8.4 Hz, 2 H).
13C NMR (100 MHz, DMSO-d6): δ = 167.1, 138.5, 131.8, 130.3, 129.4.
Terephthalic Acid (6k)48
Yield: 42.3 mg (51%); white solid; mp >300 °C (Lit.17m >300 °C).
IR (KBr): 1684, 1593, 1425, 1322, 1093, 762 cm–1
.
1H NMR (400 MHz, DMSO-d6): δ = 8.04 (s, 4 H).
13C NMR (100 MHz, DMSO-d6): δ = 167.3, 135.1, 130.1.
p-Bromobenzoic Acid (6e)42
Yield: 78.3 mg (78%); white solid; mp 205–206 °C (Lit.17m 249–
IR (KBr): 1691, 1426, 1285, 1113 cm–1
.
250 °C).
1H NMR (400 MHz, CDCl3): δ = 7.96 (d, J = 8.8 Hz, 2 H), 7.63 (d, J =
8.8 Hz, 2 H).
Funding Information
13C NMR (100 MHz, DMSO-d6): δ = 167.3, 132.4, 132.0, 130.6, 127.6.
We thank the National Natural Science Foundation of China (Grant
IR (KBr): 1681, 1588, 1428, 1321, 1128, 1013, 852 cm–1
.
No. 21372153) for financial support.
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p-Nitrobenzoic Acid (6f)42
Yield: 53.7 mg (64%); white solid; mp 227–228 °C (Lit.17m 238–
239 °C).
Supporting Information
Supporting information for this article is available online at
1H NMR (400 MHz, CDCl3): δ = 8.34 (d, J = 8.8 Hz, 2 H), 8.28 (d, J =
9.2 Hz, 2 H).
https://doi.org/10.1055/s-0036-1588429.
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13C NMR (100 MHz, DMSO-d6): δ = 166.5, 150.7, 137.1, 131.4, 124.4.
IR (KBr): 1695, 1608, 1543, 1430, 1351, 1111, 802 cm–1
.
References
(1) (a) Röper, M.; Gehrer, E.; Narbeshuber, T.; Siegel, W. Acylation
and Alkylation, Ullmann’s Encyclopedia of Industrial Chemistry;
Wiley-VCH: Weinheim, 2002. (b) Sheldon, R. A.; Kochi, J. K.
Metal-Catalyzed Oxidations of Organic Compounds; Academic:
New York, 1981. (c) Cainelli, G.; Cardillo, G. Chromium Oxida-
tions in Organic Chemistry; Springer: Berlin, 1984. (d) Hudlicky,
M. Oxidation in Organic Chemistry; American Chemical Society:
Washington DC, 1990. (e) Recupero, F.; Punta, C. Chem. Rev.
2007, 107, 3800.
4-(Methoxycarbonyl)benzoic Acid (6g)44
Yield: 81.9 mg (91%); white solid; mp 223–224 °C (Lit.43 221–223 °C).
1H NMR (400 MHz, CDCl3): δ = 8.16 (m, 4 H), 3.97 (s, 3 H).
13C NMR (100 MHz, DMSO-d6): δ = 167.2, 166.3, 135.4, 133.8, 130.3,
130.0, 53.2.
IR (KBr): 2548, 1719, 1683, 1426, 1257, 1103, 938, 728 cm–1
.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

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Y. Hu et al.
Paper
Synthesis
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