Nitrosotetrazolium-Catalyzed Aerobic Oxidation of Alcohols to the Corresponding Carbonyl Compounds

Article abstract of DOI:10.1002/ejoc.201701662

A mesoionic-nitrosotetrazolium-catalyzed aerobic oxidation of alcohols is reported. In the presence of catalytic amounts of 5-nitroso-1,3-diphenyltetrazolium tetrafluoroborate (5 mol-%) and nitric acid (20 mol-%), a wide range of alcohols are oxidized to the corresponding aldehydes and ketones in yields of 53–100 % at room temperature under ambient air or oxygen conditions. This oxidation shows a strong preference for secondary alcohols over primary alcohols; sterically hindered alcohols are also smoothly oxidized. A mechanism involving a nitroso/NO_x catalytic cycle is proposed.

Full text of DOI:10.1002/ejoc.201701662

A Journal of
Accepted Article
Title: Nitrosotetrazolium-Catalyzed Aerobic Oxidation of Alcohols to the
Corresponding Carbonyl Compounds
Authors: Yuta Matsukawa, Tsunehisa Hirashita, and Shuki Araki
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10.1002/ejoc.201701662
European Journal of Organic Chemistry
FULL PAPER
Nitrosotetrazolium–Catalyzed Aerobic Oxidation of Alcohols to
the Corresponding Carbonyl Compounds
Yuta Matsukawa,[a] Tsunehisa Hirashita,*[a] and Shuki Araki*[a]
Abstract: In this paper, a mesoionic nitrosotetrazolium-catalyzed
Results and Discussion
aerobic oxidation of alcohols has been reported. In the presence of
catalytic
amounts
of
5-nitroso-1,3-diphenyltetrazolium
We started by screening re-oxidizing agents other than nitric
acid to act as the terminal oxidant. A series of organic and
inorganic oxidants (200 mol%) were examined for the oxidation
of benzyl alcohol (3a) in the presence of 1 (5 mol%) at room
temperature. The yield of benzaldehyde (4a) was monitored by
gas chromatography (GC) and the reaction continued until the
yield reached a plateau. The results are summarized in Table 1.
Halogen-based oxidants such as chloramine-T, chloranil, and
sodium periodate did not succeed as the re-oxidant of 2 (Entries
1 to 3). Fe(III) and Cu(II) salts afforded 24–69% yields of 4a
(Entries 4, 6, and 7), while Fe(acac)3 led to quantitative recovery
of 3a (Entry 5). Sodium nitrite and sodium nitrate under acidic
conditions gave good yields (Entries 8 and 9). Eventually, nitric
acid proved to be the best re-oxidant (Entry 10).
tetrafluoroborate (5 mol%) and nitric acid (20 mol%), a broad range
of alcohols are oxidized to the corresponding aldehydes and ketones
in yields of 53–100% at room temperature under ambient air or
oxygen conditions. This oxidation shows a strong preference for
secondary alcohols over primary ones, and sterically hindered
alcohols are also smoothly oxidized. A mechanism involving the
nitroso/NOx catalytic cycle is proposed.
Introduction
Metal-free aerobic oxidation of alcohols is regarded as one of
the most environmentally benign methods for forming aldehydes
and ketones because there is no metal contamination in the
products and water is the only by-product.[1–3] In recent years,
organocatalyst-mediated aerobic oxidation[4–6] has been
successfully achieved using nitroxyl radicals such as 2,2,6,6-
tetramethylpiperidine-N-oxyl (TEMPO), 9-azabicyclo [3.3.1]
nonane-N-oxyl (ABNO) and 2-azaadamantane-N-oxyl (AZADO)
with nitrogen oxides (H)NOx as co-catalysts.[7–13] We have
recently developed the mesoionic nitrosotetrazolium salt 1 via
oxidation of the mesoionic hydroxyamide 2 (Scheme 1).[14]
Although nitroso compounds generally do not function as
oxidation catalysts, a positively charged tetrazolium ring can
render the nitroso group capable of acting as a mediator in the
oxidation of alcohols. A catalytic amount of 1 (5 mol%) was
sufficient to obtain aldehydes in high yields by oxidation of
benzylic alcohols using HNO3 as a terminal oxidant. However,
the stoichiometric use of HNO3 may be a hurdle for expansion of
Table 1. Catalytic oxidations of 3a in the presence of 1 and stoichiometric
amount of re-oxidants.[a]
Time
[h]
Entry
Re-oxidant
Yield [%]
Recovery of 3a [%]
1[b]
2
chloramine-T
3.0
0
99
chloranil
3.0
1.5
1.5
3.0
28
4
96
88
67
100
44
25
5
3
NaIO4
8
the substrate scope and for
a wide range of synthetic
applications. In this article, we report a catalytic version with
atmospheric oxygen as the terminal oxidant. The mechanism
and unique selectivity are also discussed.
4
FeCl3
24
0
5
Fe(acac)3
6
CuCl2•2H2O
Cu(ClO4)2•9H2O
NaNO2[c], conc. HCl[c]
NaNO3[c], conc. HCl[c]
50
69
84
86
93
7
6.0
6.0
5.0
1.3
8
9
9
[c]
10
conc. HNO3
0
Scheme 1. Synthesis of nitrosotetrazolium salt 1.
[a] Reaction conditions: 3a (0.20 mmol), re-oxidant and 1 in MeCN (2.0 mL)
at room temperature. [b] H2O (40 µL) was added. [c] With 100 mol%.
[a]
Y. Matsukawa, Dr. T. Hirashita, Prof. Dr. S. Araki
Life Science and Applied Chemistry, Graduate School of
Engineering, Nagoya Institute of Technology
Gokiso-cho, Showa-ku, Nagoya, Aichi, 466-8555 Japan
E-mail: hirasita@nitech.ac.jp
As a high level of conversion of 3a was achieved with nitrite or
nitrate salt under acidic conditions or with nitric acid alone
(Entries 8–10, Table 1), we then attempted an aerobic oxidation
of 3a using a catalytic amount of a nitrogen oxide (NOx) source
with atmospheric oxygen as the re-oxidant (Table 2). Recently,
araki.shuki@nitech.ac.jp
https://www.nitech.ac.jp/eng/
Supporting information for this article is given via a link at the end of
the document.
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10.1002/ejoc.201701662
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NOx has been extensively studied as a co-catalyst in the aerobic
oxidation of alcohols.[3] When the aerobic oxidation of 3a was
performed with NaNO2 or NaNO3 in the presence of
trifluoroacetic acid (TFA), most of the starting alcohol was
recovered and little or no 4a was obtained (Entries 1 and 2).
Stavber et al. examined the role of acids in the aerobic oxidation
of alcohols with TEMPO and ammonium nitrate salt, and
concluded that strong acids with a pKa of at least −5 are
necessary to promote the oxidation.[15] In the present reaction,
however, even p-toluenesulfonic acid (pKa −2.8) allowed aerobic
oxidation with NOx, giving aldehyde 4a in a moderate yield
(Entries 3 and 4). Eventually, nitric acid was found to attain the
highest yield of 4a among the NOx sources investigated (Entry 6).
Reducing the amount of nitric acid below 20 mol%, it was found
that the yield of aldehyde 4a remarkably decreased, even with
15 mol% nitric acid (Entries 7–9). In contrast, a larger amount of
nitric acid (above 20 mol%) did not notably increase the yield
(Entry 10). Quantitative conversion was achieved when the
reaction was performed under pure dioxygen instead of under
ambient air conditions (Entry 11), which was determined to be
the optimum condition for the oxidation. In the absence of 1
under otherwise identical conditions, the oxidation did not
proceed.
We had previously reported that the addition of acid is crucial for
stabilizing the reversible redox cycle of 1.[14] As nitric acid acts
not only as an oxidizing agent but also as a proton source, we
examined these functions by individually supplying NOx and
proton sources (Table 3). When TFA (10 mol%), a non-oxidizing
proton source, was used along with nitric acid (10 mol%), the
yield remained almost constant (Entry 1). Upon using sodium
nitrite (10 mol%) as a non-acidic NOx source with nitric acid (10
mol%), the yield remarkably decreased (Entry 2). Addition of
TFA (Entry 4) to the optimum conditions (Entry 3) resulted in a
decrease in the yield. Thus, the use of nitric acid alone (Entry 11,
Table 2) again proved optimum for the catalytic oxidation.
Table 3. Comparison of amounts of NOx and H+ sources.[a]
Additive
Entry
HNO3 [mol%]
Yield [%]
Recovery of 3a [%]
(mol%)
TFA (10)
NaNO2 (10)
None
Table 2. Comparisons of amount and types of NOx sources.[a]
1
10
10
20
20
34
9
39
48
2
2
3[b]
4
80
63
TFA (20)
23
NOx source
[a] Reaction conditions: 3a (0.40 mmol), NOx, H+ sources, and 1 in MeCN (4.0
mL) at room temperature. [b] With 3a (0.2 mmol) in MeCN (2.0 mL).
Yield
[%]
Recovery
of 3a [%]
Entry
Time [h]
NOx salt
NaNO2
NaNO3
NaNO2
NaNO3
NaNO3
acid
TFA
mol%
20
20
20
20
20
20
5
1
24.0
24.0
10.0
10.0
3.0
0
75
61
25
7
2
TFA
13
42
67
65
80
15
31
39
81
98
Based on the stoichiometric oxidation reaction with nitric acid,[14]
nitrogen dioxide should also function as an oxidizing agent.
Therefore, we examined the role of nitrogen dioxide instead of
nitric acid under neutral conditions. In NO2-saturated MeCN in
an Ar atmosphere, alcohol 3a was oxidized into 4a with 40%
yield in the absence of 1,[16] while 4a was obtained with 70%
yield in the presence of a catalytic amount of 1 (Scheme 2),
which is comparable to the reactions performed with excess NOx
sources (Entries 8 and 9, Table 1). This indicates that nitrogen
dioxide is certainly involved in the redox cycle and if enough NOx
is supplied, the addition of acids is not essential to promote the
oxidation.
3
p-TsOH
p-TsOH
HCl
4
5
6
6
HNO3
3.0
2
7[b]
8[b]
9[b]
10
11[c, d]
HNO3
HNO3
HNO3
HNO3
HNO3
5.0
85
66
57
0
10
15
25
20
4.0
4.0
2.5
4.5
0
[a] Reaction conditions: 3a (0.2 mmol), NOx source, and 1 in MeCN (2.0 mL)
at room temperature. [b] With 3a (0.6 mmol) in MeCN (6.0 mL). [c] With 3a
(0.4 mmol) in MeCN (4.0 mL). [d] Under O2 balloon.
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10.1002/ejoc.201701662
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Scheme 2. Oxidation of 3a with NO2 under an argon atmosphere.
Having established the optimum reaction conditions, the
oxidation of various alcohols, including benzylic, linear aliphatic,
and cyclic aliphatic alcohols, were examined (Scheme 3).
Benzylic alcohols possessing a chloro, a nitro, a methoxy, or an
ester group at the para position were smoothly oxidized to the
corresponding aldehydes 4a–4e in high yields. Benzhydrol 3f
was readily oxidized to benzophenone 4f in excellent yield. The
cycloaliphatic alcohols 3g–3i were oxidized to the corresponding
ketones in moderate to good yields. Primary and secondary
aliphatic alcohols gave the corresponding carbonyl compounds
4j (53%) and 4k (96%). This preference for secondary alcohols
suggests that a chemo-selective oxidation of secondary alcohols
could be achieved in the presence of primary hydroxyl
functionality. Indeed, treatment of a 1:1 mixture of 3j and 3k
afforded 4k selectively in 48% yield. Even the sterically hindered
secondary alcohol 3l was also successfully oxidized to ketone 4l
in 87% yield. In TEMPO-based alcohol oxidation, oxoammonium
species generated in situ show different selectivities toward
primary and secondary alcohols depending on pH; the oxidation
of secondary alcohols, which are better hydride donors than
primary alcohols, are dominant in acidic media.[6] The selective
oxidation of secondary alcohol 3k (Scheme 3) can be explained
by assuming that the reaction mechanism involving the
nitrosotetrazolium salt 1 is similar to that of the oxoammonium
species. The smooth oxidation of a sterically demanding alcohol
like 3i can be accounted for by the smaller steric hindrance in
nitrosotetrazolium salt 1 than in the oxoammonium derived from
TEMPO.[17–18] In contrast, ethyl lactate (3m) and benzoin (3n)
were not oxidized at all and remained almost intact. Such α-
hydroxy carbonyl compounds can be almost quantitatively
oxidized using ABNO or keto-ABNO.[10] In addition, no formation
of carboxylic acids was observed at all in the oxidation of
primary alcohols. The intramolecular competitive oxidation of
1,2-diol 3o selectively gave 2-hydroxyacetophenone (phenacyl
alcohol 4o) in 82% yield, without any possible by-products like 2-
hydroxyphenylacetaldehyde, phenylglyoxal, or 1,2-cleavage
products, highlighting the unique chemoselectivity of this
oxidizing agent. Some limitations were, however, found in the
oxidation reaction; p-aminobenzyl alcohol and cinnamyl alcohol
were hardly converted to the corresponding aldehydes. This
may be attributed to reactions of the nitroso functionality in 1
with the amino group and the alkenyl moiety.
Scheme 3. Oxidation of alcohols under the optimum conditions. [a]
[a] Reaction conditions: 3 (0.20 mmol), concentrated HNO3, and 1 in MeCN
(2.0 mL) at room temperature. [b] With 3 (0.40 mmol) in MeCN (4.0 mL). [c]
With 3 (1.0 mmol) in MeCN (10 mL). [d] Isolated yield.
The catalyst 1 can be reused (Table 4). After completing the
oxidation reaction of 3a, the solvent containing 1 was directly
reused for the next oxidation of 3a. Although addition of new
HNO3 was required, no decrease in yield was observed.
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10.1002/ejoc.201701662
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without using heavy metals. The mesoionic catalyst is re-
oxidized by nitrogen dioxide, and the resulting nitric oxide is
recycled to nitrogen dioxide by oxidation with dioxygen. In this
process, secondary alcohols are preferably oxidized over
primary alcohols, and primary alcohols are selectively oxidized
into aldehydes, with no carboxylic acids being observed as
products. As long as nitrogen dioxide exists in the solution, this
oxidation reaction proceeds. Therefore, concentrated nitric acid
is not necessary for the oxidation reaction itself, meaning this
reaction can be applied to a wide range of substrates containing
acid-sensitive functionalities.
Table 4. Recyclability of 1.[a]
Entry
Run
Time [h]
Yield [%]
Recovery of 3a [%]
1
2
4.5
3.0
4.5
4.5
97
73
1
21
0
1
Experimental Section
General Experimental Procedure
1
99
All solvents and chemicals were used without further purification
unless otherwise stated. MeCN was dried by distillation from
CaH2 powder. Benzyl alcohol, benzaldehyde, 1-undecanol,
2
2[b]
100
0
[a] Reaction conditions: 3a (0.40 mmol), concentrated HNO3 (20 mol%) and 1
(5 mol%) in MeCN (4.0 mL) at room temperature. [b] After the run 1,
concentrated HNO3 (20 mol%) was added.
undecanal,
2-undecanol,
2-undecanone,
cyclohexanol,
cyclohexanone, and ethyl lactate were purified by Kugelrohr
distillation. 2,2-Dimethyl-3-octanone (4l)[19] and methyl p-
(hydroxymethyl)benzoate (3e)[20] were prepared according to
literature
procedure.
5-Nitroso-1,3-diphenyltetrazolium
tetrafluoroborate (1) was also synthesized according to literature
A plausible mechanism for this aerobic oxidation is depicted in
Scheme 4. The nitrosotetrazolium salt 1 and alcohol 3 react to
produce the corresponding carbonyl compound 4 and the
protonated hydroxyamide 2. The latter is oxidized by nitric acid
to regenerate the nitrosotetrazolium salt 1, and nitric acid itself is
decomposed into nitrogen dioxide. Nitrogen dioxide can also
convert the hydroxyamide into nitrosotetrazolium salt 1 giving
nitric oxide (Scheme 2), which is oxidized to nitrogen dioxide by
molecular oxygen, closing the catalytic cycle.
procedure.[14]
General procedure for catalytic oxidations of alcohol 3a in
the presence of 1 and stoichiometric amount of re-oxidants
(Table 1)
A mixture of nitrosotetrazolium salt (1, 5 mol%), re-oxidant (200
mol%), and alcohol 3a (100 mol%) was stirred in MeCN (2 mL)
at room temperature in the presence of PhCN (tR = 5.9 min) as
an internal standard. At intervals, aliquots were analyzed by GC.
The yields of aldehyde 4a (tR = 4.4 min, 0−93%) and recoveries
of 3a (tR = 9.5 min, 0−100%) were calculated using GC with
respect to the internal standard.
Oxidation of 3a with NO2 under argon atmosphere (Scheme
2)
Cu powder (3.1 g, 0.049 mol) was added to concentrated HNO3
(10 mL, 0.13 mol) at room temperature. The generated brown
gas was dried by passing through a column filled with P4O10 and
liquefied by cooling in a dry ice and acetone bath. The collected
liquid was vaporized by heating to room temperature and the
regenerated brown gas was led into MeCN (10 mL) to prepare
an NO2-saturated solution. A mixture of nitrosotetrazolium salt (1,
5 mol%) and benzyl alcohol (3a, 100 mol%) was stirred in the
NO2-saturated MeCN (2.0 mL) at room temperature in an Ar
atmosphere for 3.0 h in the presence of PhCN as an internal
standard. At intervals, aliquots were analyzed by GC. The yields
of 4a and recoveries of 3a were calculated to be 70% and 15%
by GC using the internal standard.
Scheme 4. Plausible mechanism for the aerobic oxidation.
Conclusions
General procedure for the comparisons of amount and
types of NOx sources (Table 2)
A mixture of nitrosotetrazolium salt (1, 5 mol%), NOx source (5–
25 mol%), and benzyl alcohol (3a, 100 mol%) was stirred in
In summary, we demonstrate the properties of mesoionic
nitrosotetrazolium salt 1 as an efficient catalyst for the aerobic
oxidation of alcohols under mild conditions. This oxidation can
be performed using atmospheric oxygen as a terminal oxidant
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1
MeCN (2.0 mL) at room temperature under air (balloon) for 2.5
to 24.0 h in the presence of PhCN as an internal standard. At
intervals, aliquots were analyzed by GC after passing through a
SiO2 column (eluting with CH2Cl2). The yields of 4a (0−98%) and
recoveries of 3a (2−85%) were calculated by GC using the
internal standard.
2-Adamantanone (4h):[17] Colorless crystals (28 mg, 93%). H
NMR (300 MHz, CDCl3): δ = 1.93−2.11 (m, 12H), 2.55 ppm (m,
2H).
l-Menthone (4i):[17] Colorless liquid (80 mg, 52%). 1H NMR (300
MHz, CDCl3): δ = 0.85 (d, 3H, J = 6.6 Hz, CH3 of iPr), 0.91 (d, 3H,
i
J = 6.9 Hz, CH3 of Pr), 1.01 (d, 3H, J = 6.9 Hz, Me), 1.37−1.49
General procedure for the comparison of amounts of NOx
and H+ source (Table 3)
(m, 2H), 1.89−1.95 (m, 3H) 1.99−2.16 (m, 3H), 2.32−2.37 ppm
(m, 1H).
A mixture of nitrosotetrazolium salt (1, 5 mol%), NOx source (10
or 20 mol%), H+ source (10–40 mol%) and benzyl alcohol (3a,
100 mol%) was stirred in MeCN (2.0−4.0 mL) at room
temperature with an air balloon for 3.0 h in the presence of
PhCN as an internal standard. At intervals, aliquots were
analyzed by GC. The yields of 4a (9−80%) and recoveries of 3a
(2−48%) were calculated by GC using the internal standard.
2-Hydroxyacetophenone (4o):[22] Colorless crystals (45 mg,
82%). H NMR (300 MHz, CDCl3): δ = 3.52 (t, 1H, J = 4.7 Hz,
OH), 4.90 (d, 2H, J = 4.8 Hz, CH2), 7.52 (t, 2H, J = 7.8 Hz, m of
Ph), 7.65 (t, 1H, J = 7.4 Hz, p of Ph), 7.94 ppm (d, 2H, J = 7.2
Hz, o of Ph).
1
Competitive oxidation of primary and secondary alcohols
(Scheme 3)
General procedure for the aerobic oxidation of alcohols
under the optimum conditions (Scheme 3)
A mixture of nitrosotetrazolium salt (1, 3.6 mg, 0.011 mmol),
concentrated HNO3 (3.0 µL, 0.040 mmol), 1-undecanol (3j, 35
mg, 0.20 mmol), and 2-undecanol (3k, 35 mg, 0.20 mmol) was
stirred in MeCN (2.0 mL) at room temperature under O2 (O2
balloon) for 7 h in the presence of PhCN (tR = 5.9 min) as an
internal standard. At intervals, aliquots were analyzed by GC
after passing through a SiO2 column (eluting with CH2Cl2). The
yield of 4k (tR = 5.6 min), the recoveries of 3j (tR = 9.4 min) and
3k (tR = 8.0 min) were calculated to be 48%, 83%, and 45%,
respectively, based on a calibration curve obtained using an
authentic sample. The peak of 4j (tR = 5.7 min) was not detected
at any intervals.
A mixture of nitrosotetrazolium salt (1, 5 mol%), concentrated
HNO3 (20 mol%), and alcohol 3 (100 mol%) was stirred in MeCN
(2.0−10.0 mL) at room temperature under O2 balloon in the
presence of PhCN as an internal standard. At intervals, aliquots
were analyzed by GC after passing through a SiO2 column
(eluting with CH2Cl2). The yields of 4 (0−100%) were calculated
by GC using the internal standard. For p-chlorobenzyl alcohol
(3b),
p-nitrobenzyl
alcohol
(3c),
methyl
p-
(hydroxymethyl)benzoate (3e), benzhydrol (3f), 2-adamantanol
(3h), l-menthol (3i), and styrene glycol (3o), the corresponding
carbonyl compounds were isolated by column chromatography
on silica gel eluting with CH2Cl2. Retention times for carbonyl
compounds the 4d, 4g, 4j, 4k, and 4l were as follows: tR = 10.4
General procedure for the catalytic oxidation on a 1.0 mmol-
scale
min for 4d in 100% yield; tR = 2.3 min for 4g in 79% yield; tR
=
5.9 min for 4j in 53% yield; tR = 5.6 min for 4k in 96% yield; tR =
2.1 min for 4l in 87% yield. Retention times for alcohols 3g, 3j,
3k, 3l and 3m were as follows: tR = 2.9 min for 3g in 7% yield; tR
= 9.4 min for 3j in 31% yield; tR = 8.1 min for 3k in 3% yield; tR =
3.1 min for 3l in 8% yield; tR = 2.3 min for 3m in 80% yield. In the
competitive oxidation of 3j and 3k, recoveries of these
compounds were calculated to be 3j (83%) and 3k (45%).
A mixture of nitrosotetrazolium salt (1, 17 mg, 0.050 mmol),
concentrated HNO3 (15.3 µL, 0.20 mmol), and alcohol 3f or 3h
(1.0 mmol) was stirred in MeCN (10 mL) at room temperature
under O2 balloon for 2.0–7.5 h. The solvent was evaporated
under reduced pressure and the residue was passed through a
SiO2 column (eluting with CH2Cl2) to give the corresponding
ketone (4f, 100%; 4h, 96%).
p-Chlorobenzaldehyde (4b):[21] Colorless crystals (52 mg,
92%). H NMR (300 MHz, CDCl3): δ = 7.53 (d, 2H, J = 8.1 Hz),
Benzophenone (4f):[21] Colorless liquid (0.18 g, 1.0 mmol,
100%). 1H NMR (300 MHz, CDCl3): δ = 7.49 (t, 4H, J = 7.7 Hz, m
of Ph), 7.60 (t, 2H, J = 7.3 Hz, p of Ph), 7.81 ppm (d, 4H, J = 7.2
Hz, o of Ph).
1
7.83 (d, 2H, J = 8.7 Hz), 9.99 ppm (s, 1H).
p-Nitrobenzaldehyde (4c):[21] Colorless crystals (50 mg, 83%).
1H NMR (300 MHz, CDCl3): δ = 8.08 (d, 2H, J = 9.0 Hz), 8.41 (d,
2H, J = 8.4 Hz), 10.17 ppm (s, 1H).
2-Adamantanone (4h):[17] Colorless crystals (0.15 g, 0.96 mmol,
1
96%). H NMR (300 MHz, CDCl3): δ = 1.94−2.11 (m, 12H), 2.55
ppm (m, 2H).
Methyl telephthalaldehydate (4e):[21] Colorless crystals (57 mg,
87%). 1H NMR (300 MHz, CDCl3): δ = 3.97 (s, 3H, CH3), 7.96 (d,
2H, J = 8.1 Hz), 8.21 (d, 2H, J = 8.4 Hz), 10.11 ppm (s, 1H).
Recyclability of 1 (entry 2 in Table 4)
A mixture of nitrosotetrazolium salt (1, 5 mol%), concentrated
HNO3 (20 mol%), and benzyl alcohol (3a, 100 mol%) was stirred
in MeCN (4.0 mL) at room temperature under O2 balloon for 4.5
h in the presence of PhCN as an internal standard. After
confirming the completion of the oxidation by GC, 3a (100 mol%)
and HNO3 (20 mol%) were added. At intervals, aliquots were
analyzed by GC after passing through a SiO2 column (eluting
1
Benzophenone (4f):[21] Colorless liquid (71 mg, 98%). H NMR
(300 MHz, CDCl3): δ = 7.49 (t, 4H, J = 7.3 Hz, m of Ph), 7.60 (t,
2H, J = 7.4 Hz, p of Ph), 7.81 ppm (d, 4H, J = 7.2 Hz, o of Ph).
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[8]
[9]
R. Liu, C. Dong, X. Liang, X. Wang, X. Hu, J. Org. Chem. 2005, 70,
with CH2Cl2). The yields of 4a (100%) was calculated by GC
using the internal standard.
729–731.
X. L. Wang, R. H. Liu, Y. Jin, X. M. Liang, Chem. Eur. J. 2008, 14,
2679–2685.
[10] M. B. Lauber, S. S. Stahl, ACS Catal. 2013, 3, 2612–2616.
[11] M. Shibuya, S. Nagasawa, Y. Osada, Y. Iwabuchi, J. Org. Chem. 2014,
79, 10256–10268.
Acknowledgments
[12] Y. Kadoh, M. Tashiro, K. Oisaki, M. Kanai, Adv. Synth. Catal. 2015, 357,
2193–2198.
Financial support of this work by the Sasakawa Scientific
Research Grant (28-303) is gratefully acknowledged.
[13] T. Hirashita, M. Nakanishi, T. Uchida, M. Yamamoto, S. Araki, I. W. C.
E. Arends, R. A. Sheldon, ChemCatChem, 2016, 8, 2704–2709.
[14] Y. Matsukawa, T. Hirashita, S. Araki, Tetrahedron, 2017, 73,
6052−6056.
Keywords: mesoionic compounds • nitrogen heterocycles •
nitroso compounds • oxidation
[15] R. Prebil, G. Stavber, S. Stavber, Eur. J. Org. Chem. 2014, 395–402.
[16] I Hermans, H. J. Teles, R. Dehn, T. Bruggemann, R. Send, P. N.
Plessow, Top. Catal. 2014, 57, 1256−1264.; C. Aellig, U.
Neuenschwander, I. Hermans, ChemCatChem, 2012, 4, 525−529.
[17] M. Shibuya, M. Tomizawa, Y. Sasano, Y. Iwabuchi, J. Org. Chem. 2009,
74, 4619–4622.
[1]
[2]
S. S. Stahl, P. L. Alsters, Liquid Phase Aerobic Oxidation Catalysis;
Wiley-VCH: Weinheim, 2016.
M. I. Fernandez, G. Tojo, Oxidation of Alcohols to Aldehydes and
Ketones: A Guide to Current Common Practice.; Springer: New York,
2006.
[18] M. Shibuya, M. Tomizawa, I. Suzuki, Y. Iwabuchi, J. Am. Chem. Soc.
2006, 128, 8412–8413.
[3]
R. A. Sheldon, I. W. C. E. Arends, G.-J. ten Brink, A. Dijksman, Acc.
Chem. Res. 2002, 35, 774–781.
[19] L. F. Fieser, Experiments in Organic Chemistry 3rd Edition, D. C.
Health and Company, Boston, 1955; pp 94.
[4]
[5]
B. L. Ryland, S. S. Stahl, Angew. Chem. Int. Ed. 2014, 53, 8824–8838.
Q. Cao, L. M. Dornan, L. Rogan, N. L. Hughes, M. J. Muldoon, Chem.
Commun. 2014, 50, 4524–4543.
[20] B. T. Cho, S. K. Kang, M. S. Kim, S. R. Ryu, D. K. An, Tetrahedron,
2006, 62, 8164–8168.
[21] M. Iinuma, K. Moriyama, H. Togo, Tetrahedron, 2013, 69, 2961−2970.
[22] B. Plietker, J. Org. Chem. 2004, 69, 8287−8296.
[6]
[7]
S. Wertz, A. Studer, Green Chem. 2013, 15, 3116–3134.
R. Liu, X. Liang, C. Dong, X. Hu, J. Am. Chem. Soc. 2004, 126, 4112–
4113.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201701662
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents
FULL PAPER
Nitrosotetrazolium-catalyzed aerobic
oxidation of alcohols is reported. By
using catalytic amounts of
nitrosotetrazolium 1 and nitric acid,
various alcohols can be oxidized to
the corresponding carbonyl
Aerobic oxidation
Yuta Matsukawa,[a] Tsunehisa
Hirashita,*[a] and Shuki Araki*[a]
Page No. – Page No.
Nitrosotetrazolium–Catalyzed Aerobic
Oxidation of Alcohols to the
Corresponding Carbonyl Compounds
compounds under ambient air or
oxygen conditions. A mechanism
involving the nitroso/NOx catalytic
cycle is proposed.
This article is protected by copyright. All rights reserved.