(Nitrosonaphtholato)metal complex-catalyzed oxidation of phenols and alkenes

Article abstract of DOI:10.1039/a902902h

Bis(1-nitroso-2-naphtholato)manganese(II), tris(1-nitroso-2-naphtholato)manganese(III), tris(2-nitroso-1-naphtholato)manganese(III), bis(1-nitroso-2-naphtholato)cobalt(II), bis(1-nitroso-2-naphtholato)nickel(II), bis(1-nitroso-2-naphtholato)copper(II) and bis(1-nitroso-2-naphtholato)zinc(II) were prepared and their catalytic abilities in the oxidation of phenols were examined. The best yields of diphenoquinones were obtained when the catalytic oxidation using bis(1-nitroso-2-naphtholato)manganese(II) was carried out at 23°C under an oxygen atmosphere (1 atm) in the presence of a phosphine ligand. Likewise, phenols were completely converted to the corresponding diphenoquinones together with small amounts of benzoquinones under an oxygen pressure (20 atm) at 50°C in a short period of time. It was proven that the manganese(II) catalyst, molecular oxygen, and phosphine ligand were essential for the catalytic phenol oxidation. On the other hand. bis(1-nitroso-2-naphtholato)manganese(II)-catalyzed epoxidation of alkenes was only effective when iodosylbenzene was used. The catalytic oxidation mechanism was discussed on the basis of the measurement of cyclic voltammograms of the (nitrosonaphtholato)metal complexes, isolated intermediates, and effect of additives.

Full text of DOI:10.1039/a902902h

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(Nitrosonaphtholato)metal complex-catalyzed oxidation of phenols
and alkenes
a
a
a
b
Hiroshi Nishino,* Hideaki Satoh, Mayumi Yamashita and Kazu Kurosawa
a
Department of Chemistry, Faculty of Science, Kumamoto University, Kurokami 2-39-1,
Kumamoto 860-8555, Japan. E-mail: nishino@aster.sci.kumamoto-u.ac.jp;
Fax: ϩ81-96-342-3371
Department of Environmental Science, Faculty of Science, Kumamoto University,
b
Kurokami 2-39-1, Kumamoto 860-8555, Japan
Received (in Cambridge, UK) 12th April 1999, Accepted 2nd July 1999
Bis(1-nitroso-2-naphtholato)manganese(), tris(1-nitroso-2-naphtholato)manganese(), tris(2-nitroso-1-
naphtholato)manganese(), bis(1-nitroso-2-naphtholato)cobalt(), bis(1-nitroso-2-naphtholato)nickel(), bis(1-
nitroso-2-naphtholato)copper() and bis(1-nitroso-2-naphtholato)zinc() were prepared and their catalytic abilities
in the oxidation of phenols were examined. The best yields of diphenoquinones were obtained when the catalytic
oxidation using bis(1-nitroso-2-naphtholato)manganese() was carried out at 23 ЊC under an oxygen atmosphere
(
1 atm) in the presence of a phosphine ligand. Likewise, phenols were completely converted to the corresponding
diphenoquinones together with small amounts of benzoquinones under an oxygen pressure (20 atm) at 50 ЊC in a
short period of time. It was proven that the manganese() catalyst, molecular oxygen, and phosphine ligand were
essential for the catalytic phenol oxidation. On the other hand, bis(1-nitroso-2-naphtholato)manganese()-catalyzed
epoxidation of alkenes was only effective when iodosylbenzene was used. The catalytic oxidation mechanism was
discussed on the basis of the measurement of cyclic voltammograms of the (nitrosonaphtholato)metal complexes,
isolated intermediates, and effect of additives.
activity when iodosylbenzene was used as an oxidant. In this
Introduction
paper, we present a modified synthesis of [M(nnap) ] com-
n
Discovery of catalysts which function efficiently under mild
plexes, catalytic oxidation of substituted phenols, catalytic
epoxidation of alkenes, and discuss possible reaction mechan-
isms.
reaction conditions using molecular oxygen such as Gif type
1
catalysts is very important for the elucidation of the biological
oxidation process, e.g., P-450 electron-transfer oxidation in
2
cells, and the development of chemical industries like alkane
3
oxidation under mild conditions. In studies on the screening
Results
of non-metallo-porphyrin or -salen complexes as molecular
oxygen carriers, we focused on (nitrosonaphtholato)metal
complexes, [M(nnap) ]. Many spectroscopic and physical
investigations of [M(nnap) ] complexes have been done over
Synthesis of (nitrosonaphtholato)metal complexes
II
n
Although it was reported that [Mn (1-nnap) ] was prepared by
2
n
addition of manganese() chloride to a diluted aqueous solu-
4
the course of the last three decades, however, little is known
4
II
tion of 1-nitroso-2-naphthol, we synthesized [Mn (1-nnap) ]
2
about the catalytic ability of these complexes in organic
as a dark brown solid by treatment of manganese() chloride
with sodium 1-nitroso-2-naphtholate, which was prepared by
stirring 1-nitroso-2-naphthol in an aqueous sodium hydroxide
solution (see Experimental section). A similar reaction of
cobalt(), nickel(), copper() and zinc() chlorides with
sodium 1-nitroso-2-naphtholate gave the corresponding
bis(1-nitroso-2-naphtholato)metal() complexes. On the
other hand, treatment of sodium 2-nitroso-1-naphtholate with
5
reactions. In an effort to further understand this system, we
prepared some [M(nnap) ] complexes and conducted the oxid-
ation of 2,4- and 2,6-disubstituted phenols which were chosen
due to their reactivity and structural simplicity. It was
thus shown that favorable results for the autoxidation of
phenols were obtained using bis(1-nitroso-2-naphtholato)-
n
6
II
II
manganese(), [Mn (1-nnap) ]. We scrutinized the [Mn -
2
(
1-nnap) ]-catalyzed oxidation for the effect of additives, reac-
2
manganese() chloride directly afforded tris(2-nitroso-1-
tion temperatures, and oxygen pressures. As a result, it was
discovered that the corresponding diphenoquinones were quan-
titatively obtained when the reactions were carried out in the
presence of triphenylphosphine or tributylphosphine under
oxygen (1 atm) at 23 ЊC. Increasing oxygen pressure (20 atm) led
to complete conversion of phenols, but benzoquinones also
formed under these conditions.
Epoxidation of alkenes is one of the most important reac-
tions in organic synthesis because epoxides are versatile inter-
mediates which can be converted to a variety of products. In
III
naphtholato)manganese(), [Mn (2-nnap) ]. Tris(1-nitroso-2-
3
III
naphtholato)manganese(), [Mn (1-nnap) ], was made by
3
a
ligand-exchange reaction of tris(pentane-2,4-dionato)-
manganese(), [Mn(acac)3], with 1-nitroso-2-naphthol in
ethanol. All of the complexes were characterized by com-
parison with melting points and spectroscopic data in the liter-
4
ature, measurement of cyclic voltammograms (Table 1), and
II
elemental analyses. In addition, the structure of [Co (1-nnap) ]
2
was also confirmed by the magnetic susceptibility which
3
8
showed µeff = 1.76 BM (295 K).
II
light of this fact, we extended the use of the [Mn (1-nnap) ]
2
complex to catalytic epoxidation of alkenes. Although this
complex did not function as a molecular oxygen carrier in the
epoxidation of aryl-substituted alkenes, it showed a catalytic
Catalytic oxidation of phenols
5
When a mixture of 2,6-di-tert-butylphenol (1a) and a catalytic
J. Chem. Soc., Perkin Trans. 2, 1999, 1919–1924
1919

View Article Online
II
amount of [Mn (1-nnap) ] was stirred in dry dichloromethane
2
at 23 ЊC under an oxygen atmosphere (1 atm), diphenoquinone
2
a† was formed in 5% yield after 10 h (Table 2, Entry 1 and
Scheme 1). Addition of triphenylphosphine or tributyl-
9
phosphine as a co-ligand accelerated the oxidation to give the
best results with yields of 93% attained (Table 2, Entries 3 and
4
). The use of bidentate bis(diphenylphosphino)alkanes also
gave 2a in good yields along with a small amount of biphenyl-
diol 3a (Table 2, Entries 5–8).
Triphenylphosphine oxide, pyridine and pyridine N-oxide
10
were not efficient as the co-ligand in this reaction (Table 2,
II
Entries 9, 10). Although the catalytic activity of [Mn (1-
nnap) ] was also demonstrated in acetonitrile, tetrahydrofuran
2
(
THF), methanol and ethyl acetate (Table 2, Entries 11–14),
no oxidation products were obtained in the reaction using benz-
ene or acetic acid. The catalyst is insoluble in benzene and
III
decomposes in acetic acid. Use of [Mn (1-nnap) ] instead of
3
II
[
Mn (1-nnap) ] also gave a good yield of 2a (Table 3, Entry 1).
Studies incorporating [Mn (2-nnap) ] showed that it was not
2
III
3
effective as a catalyst under the conditions (Table 3, Entry 2).
When a similar reaction was carried out in the presence of
II
II
[
Co (1-nnap) ] or [Ni (1-nnap) ], more vigorous conditions
2
2
were required in order to obtain 2a (Table 3, Entries 3, 4).
II
II
[
Cu (1-nnap) ] and [Zn (1-nnap) ] complexes did not show any
2
2
catalytic activity in the reaction (Table 3, Entries 5, 6).
In order to examine the oxygen pressure effect, [Mn (1-
II
nnap) ]-catalyzed oxidation of 1a was conducted under 20, 40,
2
6
0 and 80 atm of oxygen, respectively. Under these conditions,
1
a was completely consumed after 6 h, although a significant
pressure effect did not appear. On the contrary, the high pres-
Table 1 Redox potentials of (nitrosonaphtholato)metal complexes in
dichloromethane containing 0.1 M tetrabutylammonium perchlorate at
Ϫ1 a
ν = 50 mV s
b
[M(1-nnap)n]
E /V
E /V ∆E /mV
EЈ1/2/V
E1/2/V
pc
pa
p
Scheme 1
II
[
[
[
[
[
[
Mn (1-nnap) ]
Ϫ0.500 Ϫ0.379 121
85
Ϫ0.701 Ϫ0.595 106
Ϫ1.161 Ϫ1.056 105
Ϫ0.440 Ϫ0.435
Ϫ0.441 Ϫ0.436
Ϫ0.648 Ϫ0.651
Ϫ1.109 Ϫ1.116
2
III
Mn (1-nnap)3]c Ϫ0.483 Ϫ0.398
III
Mn (salen)]Cl
sure conditions led to the formation of 4a (Table 4, Entry 2).
The best yield of 2a was obtained at 50 ЊC under 20 atm of
oxygen (Table 4, Entry 5). Interestingly, use of two equivalents
of triphenylphosphine under 20 atm of oxygen preferentially
yielded 4a (Table 4, Entry 4).
The catalytic oxidation was applied to other substituted
phenols 1b–f, and the catalytic ability of the [Mn (1-nnap)
II
Co (1-nnap) ]
2
II
Ni (1-nnap) ]
0.417
—
0.482
0.755
65
—
0.450
—
0.452
0.702
2
II
Zn (1-nnap) ]
2
a
b
All potentials were corrected by the use of EFc/Fc
ϩ
.
E1/2 was deter-
c
mined by differential pulse polarography. To compare the redox poten-
tials, the complex was measured (salen = bis(salicylidene)ethylene-
diaminato).
II
]
2
complex was confirmed (Table 4, Entries 6–13). The results are
†
Diphenoquinone is [bicyclohexa-2,5-dien-1-ylidene]-4,4Ј-dione.
shown in Table 4.
a
Table 2 [Mn(1-nnap) ]-catalyzed oxidation of 2,6-di-tert-butylphenol (1a) at 23 ЊC
2
c
Product (Yield (%))
b
d
Entry
Molar ratio
Additive
none
Solvent
CH Cl
Time/h
2a
3a
Recovery(%)
1
2
3
4
5
6
7
8
9
1:0.1:0
10
10
20
5
5
5
5
52
93
93
53
71
71
76
27
10
86
80
73
86
32
0
0
36
0
trace
trace
70
2
2
2
2
2
2
2
2
2
2
2
1:0.1:0.6
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
Ph P
CH Cl
3
2
Ph P
CH Cl
3
2
Bu P
CH Cl
3
2
Ph PCH PPh
CH Cl
4
23
16
2
2
2
2
Ph P(CH ) PPh
CH Cl
2
2
2
2
2
2
2
Ph P(CH ) PPh
CH Cl
5
5
2
2
3
2
Ph P(CH ) PPh
CH Cl
2
2
4
2
Ph PO
CH Cl
10
10
10
10
10
10
3
2
1
1
1
1
1
0
1
2
3
4
Py
CH Cl
84
2
Ph P
CH CN
trace
trace
12
3
3
Ph P
THF
10
79
3
Ph P
CH OH
3
3
Ph P
3
AcOEt
14
a
b
c
The reaction mixture was stirred under an oxygen atmosphere (1 atm). 1a:[Mn(1-nnap) ]:additive. Isolated yield based on the amount of 1a
2
d
used. 1a recovered after work up.
1
920
J. Chem. Soc., Perkin Trans. 2, 1999, 1919–1924

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III
ϩ
10
Catalytic epoxidation of alkenes
of epoxides in the [Cr (salen)] catalytic system, however,
pyridine N-oxide, triphenylphosphine oxide and pyridine did
Since it has become apparent that the manganese, cobalt and
nickel complexes exhibit catalytic activities in the phenol oxid-
ation, we applied the (nitrosonaphtholato)metal complexes to
catalytic epoxidation of aryl-substituted alkenes. Epoxidation
of trans-stilbene (5a), however, did not proceed under an
II
not influence the [Mn (1-nnap) ]-catalyzed epoxidation. cis-
2
Stilbene (5b) gave a mixture of trans-stilbene oxide (6a) and
cis-stilbene oxide (6b) (Table 5, Entry 2). Styrene (5c) and 1,1,2-
triphenylethene (5d) also afforded the corresponding epoxides
III
(
[
6c,d) (Table 5, Entries 3 and 4). Use of [Mn (1-nnap) ],
5
3
oxygen atmosphere. None of hydrogen peroxide, tert-
butylhydroperoxide and sodium hypochlorite was effective as
II
II
Co (1-nnap) ] and [Ni (1-nnap) ] led to similar results (Table
2
2
5
, Entries 5–7).
oxidant. When the reaction of 5a with iodosylbenzene in the
II
presence of [Mn (1-nnap) ] was carried out in dichloromethane
2
at 23 ЊC under argon, only 6% of the corresponding epoxide 6a
was obtained (Scheme 2). A similar reaction in acetonitrile at
Discussion
II
The measurements from the cyclic voltammogram of [Mn -
1-nnap) ] showed reversible Mn() Mn() and irreversible
5
0 ЊC improved the yield of 6a (Table 5, Entry 1).
(
2
II
Mn()→Mn() processes. This indicates that [Mn (1-nnap) ]
2
tends to be oxidized to Mn() species. In other words, it could
work as a one-electron transfer catalyst. In fact, the presence of
II
0
.1 equivalent of [Mn (1-nnap) ] led to a 5% yield of 2a (Table
2
2
, Entry 1). Since phosphine compounds are known to activate
3,9,10
II
some metal catalysts,
the activation of [Mn (1-nnap) ] was
2
examined by use of phosphine ligands. Addition of triphenyl-
II
phosphine or tributylphosphine to the [Mn (1-nnap) ] complex
2
brought about the quantitative conversion of 1a to 2a at room
temperature and the phosphine co-ligands added were also
transformed into the corresponding oxides, quantitatively
(
Table 2, Entries 3 and 4). When a similar reaction was carried
Scheme 2
out in the absence of the catalyst or under an argon atmos-
phere, the oxidation did not progress at all. In addition, only the
use of triphenylphosphine in the absence of 1a at the molar
ratio of [Mn (1-nnap)
2
II
A blank experiment without [Mn (1-nnap) ] was carried out,
2
however, the corresponding epoxide was not obtained. It was
reported that addition of pyridine N-oxide increased the yield
II
]:PPh
= 0.1:1 in dichloromethane at
2
3
3 ЊC for 20 h under an oxygen atmosphere resulted in the pro-
duction of triphenylphosphine oxide in 41% yield after the TLC
separation. On the basis of these results, it could be assumed
Table 3 Catalytic oxidation of 2,6-di-tert-butylphenol (1a) in the
a
presence of various (nitrosonaphtholato)metal complexes
Table 5 (Nitrosonaphtholato)metal-catalyzed epoxidation of alkenes
Product
a
with iodosylbenzene
(
(
Yield
%))
b
Temp./
ЊC
Recovery
2a 4a (%)
Product (Yield
Temp./ЊC (%))
c
b
Entry [M(nnap)n]
Solvent
Entry Substrate Catalyst
III
1
2
3
4
5
6
[Mn (1-nnap)3] CH Cl
23
23
50
reflux
23
88
39
trace
54
1
2
3
4
5
6
7
5a
5b
5c
5d
5a
5a
5a
[Mn(1-nnap)2]
[Mn(1-nnap)2]
[Mn(1-nnap)2]
[Mn(1-nnap)2]
[Mn(1-nnap)3]
[Co(1-nnap)2]
50
23
23
23
50
50
50
6a (26)
2
2
2
III
[Mn (2-nnap)3] CH Cl
2
6a (18)
6c (28)
6d (21)
6a (25)
6a (22)
6a (14)
6b (14)
2
II
[Co (1-nnap) ]
CH CN
29 14 45
44
2
3
II
[Ni (1-nnap) ]
CH CN
43
83
90
2
3
II
[Cu (1-nnap) ]
CH Cl
2
2
2
II
[Zn (1-nnap) ]
CH CN
23
2
3
a
[Ni(1-nnap) ]
2
The reaction mixture was stirred under an oxygen atmosphere (1 atm)
for 10 h at the molar ratio of 1a:[M(nnap) ]:Ph P = 1:0.1:1.1.
Isolated yield based on the amount of 1a used. 1a recovered after
a
The reaction was carried out at the molar ratio of alkene–catalyst–
n
3
b
c
iodosylbenzene = 1:0.1:5 in acetonitrile under an argon atmosphere
for 10 h. Isolated yield based on the amount of the alkene used.
b
work up.
a
Table 4 [Mn(1-nnap) ]-catalyzed oxidation of substituted phenols 1a–f
2
b
c
Entry
Phenol
Molar ratio
Pressure/atm Temp./ЊC
Time/h
Product (Yield (%))
Recovery (%)
1
2
3
4
5
6
7
8
9
1a
1a
1a
1a
1a
1b
1b
1c
1c
1d
1:0.1:1.1
1:0.1:1.1
1:0:1.1
1:0.1:2.2
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
1
20
20
20
20
1
20
1
20
20
23
23
23
23
50
23
50
23
50
50
20
6
6
6
3
10
3
10
3
2a (93)
0
0
90
0
0
16
0
39
trace
8
2a (67)
2a (0)
4a (29)
4a (0)
2a (4)
4a (77)
4a (22)
2a (77)
2b (75)
2b (76)
2c (56)
2c (74)
2d (26)
4b (23)
1
0
3
3d (10)
4
d (26)
e
1
1
1
1
2
3
1e
1f
1:0.1:1.1
1:0.1:1.1
1:0.1:1.1
20
1
20
50
23
50
3
10
3
4e (15)
3f (47)
3f (72)
trace
47
trace
d
e
1f
a
b
c
The reaction was performed in the presence of triphenylphosphine. 1:[Mn(1-nnap) ]:PPh . Isolated yield based on the amount of phenol used.
2
3
d
e
Tributylphosphine was used instead of triphenylphosphine. A complex mixture was formed.
J. Chem. Soc., Perkin Trans. 2, 1999, 1919–1924
1921

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Scheme 3
II
that [Mn (1-nnap) ] catalyst was activated by the phosphine
2
ligand and molecular oxygen was trapped to form a new com-
plex A at the first stage (Scheme 3).
The oxidation state of A should be Mn() since the Mn()
species is electrochemically stable. Although the exact reason-
ing is not known, the phosphine ligand probably plays an
important role in the stability of A. We tried to observe the
change for the electronic spectrum of A but, unfortunately,
a significant change was not seen because of the presence of a
II
strong band based on a π→π* transition at 414 nm of [Mn (1-
nnap) ]. The phenoxy hydrogen of 1 must be abstracted by the
2
active complex A to give peroxymanganese() complex B and
phenoxyl radical C. The peroxymanganese() complex B
would immediately decompose under the reaction conditions to
yield phosphine oxide and hydroxyl radical which is trans-
3a,11
II
formed to oxygen and water.
At this stage, the [Mn (1-
nnap) ] catalyst could be regenerated and one catalytic cycle
2
would be constructed. On the other hand, the phenoxyl radical
C should react with 1 to give D which isomerizes to E. The
radical E should take part in a similar oxidation cycle, and
diphenyldiol 3 would be formed. The diphenyldiol 3 is oxidized
by the same catalytic cycle in dichloromethane, acetonitrile,
THF and methanol to yield F, which is transformed to the final
product 2 via a similar oxidation system again (Table 2, Entries
Scheme 4
reaction since the reaction did not proceed in the absence of the
Mn catalyst (Table 4, Entry 3).
There are many reports suggesting that higher valent oxo-
manganese species participate in most catalytic epoxid-
[Mn (1-nnap) ] would be somewhat oxidized by
iodosylbenzene to afford I and then J which is the most
plausible oxygen carrier intermediate in this reaction (Scheme 5).
II
3c,12
II
ations.
2
2
–8, 11–13). The plausible mechanism is also supported by the
isolation of 3 which was oxidized under the same reaction con-
6a
ditions to quantitatively give 2, and the fact that the added
phosphine ligand converted to the corresponding phosphine
oxide. However, the stoichiometry in molecular oxygen and the
phosphine ligand is not clear at this moment.
It was observed that increasing oxygen pressure caused the
formation of benzoquinone 4 to some extent (Table 4, Entries
2
, 4, 7, 10, 11). It was thought that raising the oxygen pressure
led to the increased probability of formation of A, which
resulted in the acceleration of the reaction of A with C (Scheme
4
). This interaction releases phenoxyl radical H and triphenyl-
II
phosphine oxide, reproducing [Mn (1-nnap) ] by a subsequent
2
one-electron transfer in intermediate complex G. The phenoxyl
radical H should be oxidized by a similar catalytic cycle men-
tioned in Scheme 3 to produce benzoquinone 4. It might be
considered that direct oxidation of H with molecular oxygen
with increasing oxygen pressure would also occur. However, it is
II
apparent that the Mn catalyst plays an important role in the
Scheme 5
1
922
J. Chem. Soc., Perkin Trans. 2, 1999, 1919–1924

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The complex J will react with alkene 5 according to the mech-
and were uncorrected. The reactions under high pressure were
carried out in a glass tube using a Taiastu Glass stainless steel
reactor.
12
anism proposed in the literature to form epoxide 6 and
II
regenerate [Mn (1-nnap) ]. Racemization of the epoxide in the
2
reaction using cis-stilbene (5b) (Table 5, Entry 2) supports the
fact that a radical intermediate such as K must be involved in
12
II
Materials
the catalytic cycle, however, it seemed that [Mn (1-nnap) ]
2
complex was only allowed to exist in the Mn() Mn() state,
while the Mn() Mn() redox state or a higher-valent state
was forbidden because of accompanying decomposition of the
complex based on the result of electrochemical measurement.
Therefore, the complex J would decompose to some extent
before oxygen transfer to 5. That is, this catalytic epoxidation
2-Naphthol, 1-naphthol, 2,6-di-tert-butylphenol (1a), 2,6-
dimethoxyphenol (1b), 2,6-diisopropylphenol (1c), 2,4-
dimethylphenol (1e), trans-stilbene (5a), styrene (5c), MnCl2,
CoCl , NiCl , CuCl , ZnCl , triphenylphosphine, tributylphos-
phine, pyridine (Wako), bis(diphenylphosphino)methane,
1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphos-
2
2
2
2
5
was not efficient in contrast to the results reported. It is
phino)propane, 1,4-bis(diphenylphosphino)butane (Kanto)
and 2,6-dimethylphenol (1d), cis-stilbene (5b), pyridine N-
oxide, iodobenzene diacetate (Aldrich) were used as received.
possible that the oxidant, such as molecular oxygen, tert-
butylhydroperoxide and sodium hypochlorite, was too weak to
produce a high-valent complex like J, which explains why the
attempted epoxidation using these oxidants failed. In addition,
it seems that peroxyl radical complex A as shown in Scheme 3 is
unique in its ability to abstract hydrogen from the hydroxy
15
16
17
[Mn(acac)3], 1,1,2-triphenylethene
and iodosylbenzene
were prepared according to the methods described in the
literature. Solvents were reagent grade and in many cases were
dried before use.
group since a co-ligand such as triphenylphosphine was not
III
effective in this epoxidation. Use of [Mn (1-nnap) ] also led to
3
Preparation of 1-nitroso-2-naphthol
II
a similar result of [Mn (1-nnap) ]-catalyzed epoxidation (Table
2
After 2-naphthol (29 g) was dissolved in hot 0.6 M NaOH (340
5
, Entry 5). It might be due to the instability of the correspond-
3
III
cm ), the solution was cooled to 0 ЊC. NaNO (14 g) was added,
2
ing high-valent oxo-manganese species since [Mn (1-nnap) ]
3
3
and 6 M H SO (31 cm ) was carefully dropped into the solu-
2
4
also resisted electrochemical oxidation to Mn().
tion during 1.5 h with stirring. The mixture was stirred for 1 h.
The brown solid which formed was filtered, washed with water,
and dried in a desiccator. The crude material was recrystallized
Conclusion
from ligroin (bp 75–120 ЊC) to give 1-nitroso-2-naphthol (14 g,
II
[
Mn (1-nnap) ] was the most effective catalyst in the oxidation
18
2
4
1
0%) as reddish-brown needles, mp 107–109 ЊC (lit., mp 106–
08 ЊC).
of phenols 1 under an oxygen atmosphere. Phosphine com-
pounds were essential as co-ligands for the oxidative conversion
of 1 to diphenoquinones 2. During the oxidation, it seemed that
at least four catalytic cycles as shown in Scheme 3 participated
in the formation of diphenoquinone 2. Raising the oxygen pres-
sure led to the production of benzoquinone 4 since the reaction
of peroxymanganese complex A with phenoxyl radical C was
accelerated under these conditions. Although (nitrosonaphthol-
ato)metal complex-catalyzed epoxidation of aryl-substituted
alkene 5 was not efficient, formation of the corresponding
epoxides 6 was possible using iodosylbenzene.
Preparation of 2-nitroso-1-naphthol
To a heated solution of 95% EtOH in which fused ZnCl (5.0 g)
2
and 1-naphthol (3.3 g) were dissolved, NaNO (2.5 g) was
2
slowly added. The mixture was heated under reflux for 3 h. The
solid which formed was filtered, washed with EtOH, and dried.
The solid was dissolved in water, which was acidified with conc.
HCl. A brown solid was formed again, filtered, and recrystal-
lized from EtOH to give 2-nitroso-1-naphthol as reddish-brown
microcrystals (3.26 g, 36%), mp 154.2–156.1 ЊC (decomp.)
18
(
lit., mp 156 ЊC (decomp.)).
Experimental
Preparation of nitrosonaphthol sodium salt
-Nitroso-2-naphthol (2.0 g) was dissolved in a 10 M NaOH
solution (50 cm ) at 0 ЊC during 2 h, and the mixture was stirred
at room temperature overnight. A green solid which formed
was filtered, washed with 2 M NaOH solution, and dried in a
desiccator to give the corresponding sodium salt (2.0 g, 90%). 2-
Nitroso-1-naphthol sodium salt was also prepared in a similar
manner to that described above.
Measurements
1
1
All of the H NMR spectra were recorded by a JNM PMX-
3
6
0SI (60 MHz) spectrometer with TMS being used as the
internal standard. The chemical shifts are shown as δ values
ppm). The IR spectra were measured on a JASCO A-102 IR
(
Ϫ1
spectrometer. The IR spectral data are expressed in cm . Mass
spectra were recorded by a JNM DX-300 mass spectrometer.
The UV–visible spectra were taken by a Hitachi U-4000 spec-
trophotometer in CH Cl . The electrochemical measurements
of the (nitrosonaphtholato)metals were carried out on a Yan-
agimoto Polarographic Analyzer P-1100 in CH Cl equipped
2
2
II
Preparation of [Mn (1-nnap)
]
2
2
2
Sodium 1-nitroso-2-naphtholate (2.7 g) was dissolved in water
with three electrodes, using a glassy carbon working electrode, a
platinum wire auxiliary electrode and a saturated calomel elec-
trode (SCE) as the reference. Tetrabutylammonium perchlorate
3
(
200 cm ), and MnCl (1.6 g) was added. After stirring for 2 h,
2
the solid which had formed was filtered, thoroughly washed
with water, and dried in a desiccator. The solid was recrystal-
lized from CH Cl –hexane to give dark-brown crystals (1.45 g,
Ϫ1
Ϫ3
(
ca. 1 × 10 mol dm ) was employed as the supporting electro-
II
2
2
lyte. Magnetic susceptibility of [Co (1-nnap) ] was measured
on a Faraday balance. The apparatus was calibrated with
2
4
6%) (Found: C, 59.96; H, 3.13; N, 6.83%. Calcd. for
C H O N Mn: C, 60.17; H, 3.02; N, 7.02%), mp over 300 ЊC;
1
3
20 12
4
2
[
Ni(en) ][S O ] (en = ethane-1,2-diamine). Diamagnetic cor-
Ϫ1
3
2
3
νmax(CHCl )/cm
1510 (N᎐O); λmax(CH Cl )/nm 414 (log ε
2 2
14
3
rections were made by Pascal’s constant. The effective mag-
4
.33).
netic moment was calculated using the equation µ = 2.828
eff
AT 1/2
A
(
χ ) , where χ is the magnetic susceptibility per cobalt atom.
III
Preparation of [Mn (1-nnap) ]
3
The GC was recorded by a HP-6590 apparatus equipped with
a fused-silica capillary column. The HPLC was performed by a
Hitachi HPLC apparatus equipped with an RP-18 ODS packed
column eluting with MeOH. All of the melting points were
determined by a Yanaco micromelting-point apparatus MP-J3
3
After [Mn(acac) ] (0.34 g) was dissolved in EtOH (100 cm ),
3
1-nitroso-2-naphthol (1.29 g) was added, and the mixture
3
was stirred for 5 h at room temperature. Hexane (100 cm )
was added to initiate crystal growth. The solid obtained was
J. Chem. Soc., Perkin Trans. 2, 1999, 1919–1924
1923

View Article Online
recrystallized from CH Cl –hexane: 0.65 g (50%) (Found: C,
measurements of Dr Masaaki Nakamura, Department of
2
2
6
2.92; H, 3.18; N, 7.12%. Calcd. for C H O N Mn: C, 63.06;
Chemistry, Kumamoto University, Kumamoto, Japan.
30
18
6
3
H, 3.18; N, 7.35%); dark-brown microcrystals, mp over 300 ЊC;
Ϫ1
νmax(KBr)/cm 1505 (N᎐O); λmax(CH Cl )/nm 421 (log ε 4.51).
2
2
References
II
1 G. Balavoine, D. H. R. Barton, Y. V. Geletii and D. R. Hill, in The
Activation of Dioxygen and Homogeneous Catalytic Oxidation, eds.
D. H. R. Barton, A. E. Martell and D. T. Sawyer, Plenum Press,
New York, 1993, p. 225.
Preparation of other [M (1-nnap) ] complexes
2
II
Other [M (1-nnap) ] complexes were synthesized by the reac-
2
tion of sodium 1-nitroso-2-naphtholate with the corresponding
metal(II) chlorides by a method similar to that described above.
The IR spectra of these complexes were identical with those
2
(a) Cytochrome P-450, eds. R. Sato and T. Omura, Academic Press,
New York, 1978; (b) T. J. McMurry and J. T. Groves, Cytochrome
P-450: Structure, Mechanism, and Biochemistry, ed. P. Ortiz
de Montellano, Chapter I, Plenum Press, New York, 1986; (c) J. P.
Collman and S. E. Groh, J. Am. Chem. Soc., 1982, 104, 1391;
(d) I. Tabushi and K. Morimitsu, J. Am. Chem. Soc., 1984, 106,
4
a
found in literature.
II
[
Co (1-nnap) ]. Red microcrystals, mp 275 ЊC (decomp.); ν
KBr)/cm 1516 (N᎐O); λ (CH Cl )/nm 407 (log ε 4.30).
2
max
6
871; (e) D. Mansury, Pure Appl. Chem., 1987, 59, 759.
Ϫ1
(
᎐
max 2 2
3
(a) R. A. Sheldon and J. K. Kochi, Metal-Catalyzed Oxidations of
Organic Compounds, Academic Press, New York, 1981; (b) P. A.
Chaloner, Handbook of Coordination Catalysis in Organic
Chemistry, Butterworths, London, 1986; (c) K. A. Jørgensen, Chem.
Rev., 1989, 89, 431; (d) G. W. Parshall and S. D. Ittel, Homogeneous
Catalysis, 2nd edn., Wiley, New York, 1992.
II
[
Ni (1-nnap) ]. Brown microcrystals, mp 93 ЊC (decomp.);
2
Ϫ1
νmax (KBr)/cm 1552 (N᎐O); λmax(CH Cl )/nm 411 (log ε 3.95).
2
2
II
[
Cu (1-nnap) ]. Brown microcrystals, mp over 300 ЊC; ν
2
Ϫ1
max
4 (a) S. Gurrieri and G. Siracusa, Inorg. Chim. Acta, 1971, 650 and
references cited therein; (b) G. T. Morgan and J. D. M. Smith,
J. Chem. Soc., 1921, 119, 704; (c) P. E. Wenger, D. Monnier and
F. Jaccard, Helv. Chim. Acta, 1950, 33, 1458; (d) C. M. Callahan,
W. C. Fernelius and B. P. Block, Anal. Chim. Acta, 1957, 16, 101; (e)
K. B. Yatsimirskii and B. D. Berezin, Izv. Vyssh. Uchebn. Zaved.,
Khim. Khim. Tekhnol., 1958, 6, 28; ( f ) E. K. Astakhova, V. M.
Savostina and V. M. Peshkova, Vestn. Mosk. Univ., Khim., 1964, 19,
(
(
KBr)/cm 1524 (N᎐O); λ (CH Cl )/nm 417 (log ε 4.32).
᎐
max 2 2
II
[
Zn (1-nnap) ]. Green microcrystals, mp over 300 ЊC; ν
2
Ϫ1
max
KBr)/cm 1554 (N᎐O); λ (CH Cl )/nm 393 (log ε 4.18).
᎐
max
2
2
III
[
Mn (2-nnap) ]. (Found: C, 63.60; H, 3.17; N, 6.84%. Calcd.
3
for C H O N Mn: C, 63.06; H, 3.18; N, 7.35%); dark brown
microcrystals, mp over 300 ЊC; νmax (CHCl )/cm 1508 (N᎐O).
6
2; (g) J. Charalambous, M. J. Frazer and F. B. Taylor, J. Chem.
Soc., 1969, 2787; (h) K. K. Chatterjee, Anal. Chim. Acta, 1959, 20,
23; (i) R. C. Aggarwal, R. Bala and R. L. Prasad, Synth. React.
30
18
6
3
Ϫ1
3
4
Inorg. Metal-Org. Chem., 1984, 14, 171; (j) D. Ray and A.
Catalytic oxidation of phenols 1a–f
Chakravorty, Inorg. Chem., 1988, 27, 3292.
5
D. Baluch, J. Charalambous, L. Lan and B. Haines, J. Chem. Soc.,
Chem. Commun., 1988, 1178.
6 (a) H. Nishino, N. Itoh, M. Nagashima and K. Kurosawa, Bull.
Chem. Soc. Jpn., 1992, 65, 620; (b) K. Omura, J. Org. Chem., 1998,
A mixture of phenol 1 (1 mmol), (nitrosonaphtholato)metal
complex (0.1 mmol) and phosphine ligand (1.1 mmol) was
3
stirred in dry CH Cl (30 cm ) at 23 ЊC under an oxygen atmos-
2
2
6
3, 10031.
(a) T. Matsushita, H. Kono and T. Shono, Bull. Chem. Soc. Jpn.,
981, 54, 2646; (b) T. Matsushita, M. Fujiwara and T. Shono, Chem.
phere (normally 1 atm). After quenching with 2 M HCl, the
aqueous mixture was extracted with CH Cl . The extract was
concentrated to dryness, and the products were separated by
silica gel TLC (Wakogel B-10) with CHCl or Et O–hexane
7
2
2
1
Lett., 1981, 631; (c) T. Matsushita, Y. Hirata and T. Shono, Bull.
Chem. Soc. Jpn., 1982, 55, 108.
8 (a) H. Hope, M. M. Olmstead, B. D. Murray and P. P. Power, J. Am.
Chem. Soc., 1985, 107, 712; (b) I. R. Little and B. P. Straughan,
J. Chem. Soc., Dalton Trans., 1986, 2211.
9 (a) T.-L. Ho, Hard and Soft Acids and Bases Principle in Organic
Chemistry, Academic Press, New York, 1977; (b) J. P. Collman, L. S.
Hegedus, J. R. Norton and R. G. Finke, Principles and Applications
of Organotransition Metal Chemistry, University Science Books,
Mill Valley, California, 1987.
0 E. G. Samsel, K. Srinivasan and J. K. Kochi, J. Am. Chem. Soc.,
1985, 107, 7606.
11 (a) C. Walling and S. Kato, J. Am. Chem. Soc., 1971, 93, 4275; C.
Walling, G. M. El-Taliawi and R. A. Johnson, J. Am. Chem. Soc.,
1974, 96, 133; (b) A. Zombeck, R. S. Drago, B. B. Corden and J. H.
Gaul, J. Am. Chem. Soc., 1981, 103, 7580; (c) S. A. Bedell and A. E.
Martell, Inorg. Chem., 1983, 22, 364; X.-Y. Wang, R. J. Motekaitis
and A. E. Martell, Inorg. Chem., 1984, 23, 271.
12 (a) K. Srinivasan, P. Michaud and J. K. Kochi, J. Am. Chem. Soc.,
1986, 108, 2309; (b) T. Katsuki, J. Synth. Org. Chem. Jpn., 1995, 53,
940; Y. N. Ito and T. Katsuki, Tetrahedron Lett., 1998, 39, 4325.
3
2
(
1:9 v/v) as the developing solvents. Melting points, R values,
f
1
retention times, IR and H NMR spectra of diphenoquinones
2
a–d, diphenyldiols 3a,c,d,f and benzoquinones 4a,b,d,e were
6,19,20
identical with those of the authentic samples.
Catalytic epoxidation of alkenes 5a–d
A mixture of alkene 5 (1 mmol), iodosylbenzene (1–5 mmol)
1
and (nitrosonaphtholato)metal complex (0.1 mmol) was stirred
3
in dry MeCN (30 cm ) for 10 h under an argon atmosphere.
3
After quenching with saturated NaHSO (2 cm ) and saturated
3
3
NaHCO aqueous solution (30 cm ), the mixture was extracted
3
with CH Cl . The extract was concentrated to dryness and the
2
2
residue was separated by silica gel TLC using CH Cl –hexane
2
2
(
1:1 v/v) as the developing solvents. Melting points, R values,
f
1
retention times, IR and H NMR spectra of epoxides 6a–d were
2
1
identical with those of the authentic samples.
1
3 L. F. Lindoy, V. Katovic and D. H. Busch, J. Chem. Educ., 1972, 49,
17.
1
1
4 A. Earnshaw, Introduction to Magnetochemistry, Academic Press,
New York, 1968.
Acknowledgements
We are grateful for the financial support of this work by a
Grant-in-Aid for General Scientific Research No. 08640691
from the Ministry of Education, Science, Culture and Sports,
Japan. HN thanks Professor Jay K. Kochi, Department of
Chemistry, University of Houston, Houston, Texas, USA, who
15 M. N. Bhattacharjee, M. K. Chaudhuri and D. T. Khathing,
J. Chem. Soc., Dalton Trans., 1982, 669.
1
1
6 H. Nishino, Bull. Chem. Soc. Jpn., 1985, 58, 217.
7 H. Saltzman and J. G. Sharefkin, Org. Synth., Coll. Vol. 5, Wiley,
New York, 1973, p. 658.
1
8 C. S. Marvel and P. K. Porter, Org. Synth., Coll. Vol. 1, Wiley, New
York, 1967, p. 411.
led us to investigate the catalytic ability of [Mn(1-nnap) ], and
2
the late Professor Derek H. R. Barton, Department of Chem-
istry, Texas A&M University, College Station, Texas, USA,
who discussed catalytic oxidations in Gif chemistry, and also
thanks Dr Thomas M. Mitzel, Department of Chemistry, Ohio
State University, Columbus, Ohio, USA, who read our manu-
script. It is a pleasure to acknowledge the redox potential
19 V. Balogh, M. Fetizon and M. Golfier, J. Org. Chem., 1971, 36, 1339.
2
0 J. H. Fookes, E. L. Pelton and M. W. Long, Jr., USP 2, 885, 444/
959 (Chem. Abstr., 1960, 54, 5579i).
1 (a) J. Read and I. G. M. Campbell, J. Chem. Soc., 1930, 2377; (b)
L. F. Lane and D. R. Walters, J. Am. Chem. Soc., 1951, 73, 4234.
1
2
Paper 9/02902H
1
924
J. Chem. Soc., Perkin Trans. 2, 1999, 1919–1924