A novel and convenient process for the selective oxidation of naphthalenes with hydrogen peroxide

Article abstract of DOI:10.1002/adsc.200600395

A practical ruthenium phase-transfer catalyst (Ru-PTC) system for the oxidation of naphthalene derivatives has been developed. Substituted 1,4-quinones are obtained in good selectivity and yield in water without the addition of any organic solvent and acid. By applying the optimized conditions the feed additive menadione (vitamin K₃) is obtained from 2-methylnaphthalene with 64 % yield and 73 % selectivity.

Full text of DOI:10.1002/adsc.200600395

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DOI: 10.1002/adsc.200600395
A Novel and Convenient Process for the Selective Oxidation of
Naphthalenes with Hydrogen Peroxide
Feng Shi,a Man Kin Tse,a and Matthias Bellera,*
a
Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany
Fax : (+49)-381-1281-5000; phone: (+49)-381-1281-0; e-mail: matthias.beller@catalysis.de
Received: August 4, 2006
Abstract: A practical ruthenium phase-transfer cat-
alyst (Ru-PTC) system for the oxidation of naph-
thalene derivatives has been developed. Substituted
1,4-quinones are obtained in good selectivity and
yield in water without the addition of any organic
solvent and acid. By applying the optimized condi-
tions the feed additive menadione (vitamin K3) is
obtained from 2-methylnaphthalene with 64% yield
and 73% selectivity.
The selective oxidation of arenes offers an efficient
access to substituted 1,4-quinones. Among the various
products 2-methyl-1,4-naphthoquinone (so-called me-
nadione or vitamin K3) is a useful supplement for vi-
tamins K1 and K2 in animal feed.[4] Menadione is usu-
ally prepared from 2-methylnaphthalene via oxidation
and various protocols were developed. As an example
the well-known chromium-mediated oxidation carried
out with stoichiometric quantities of chromium triox-
ide in sulfuric acid has been reported to give 38 to
60% yield of menadione.[5] Alternative procedures
Keywords: arenes; hydrogen peroxide; oxidation;
ruthenium
using stoichiometric amounts of Mn(III) or Ce(IV)
G
have also been described.[6] Obviously these processes
do not meet the standard of todayꢀs environmental re-
quirements, e.g., 18 kg of chromium-containing waste
is produced per kg of product.[7] In the last decade
The development and implementation of chemical more environmentally benign routes using catalytic
processes which reduce or eliminate the use and gen- quantities of metal salts were established. In these
eration of waste and hazardous substances is an im- processes, vanadium,[8] chromium,[9] molybdenum/
portant goal for current organic synthesis.[1] This is es- tungsten,[10] rhenium,[11] palladium,[12] cerium,[13]
pecially true for oxidation chemistry because in tradi- phthalocyanine,[14] porphyrin complexes[15] or zeo-
tional oxidation processes large amounts of toxic and lites,[16] were used as the catalysts and O2, H2O2 or a
volatile organic solvents, corrosive inorganic acids and percarboxylic acid were applied as the oxidant. The
metals oxidants, etc., were extensively used. Develop- best result till now for the selective oxidation of 2-
ing green selective oxidation processes is still a chal- methylnaphthalene was achieved in glacial acetic acid
lenging task in catalysis. By comparing different oxi- as solvent, sulfuric acid as catalyst and acetic anhy-
dation methods it is apparent that the choice of the dride as the dehydration reagent in about 80%
respective oxidant determines to a large extent the yield.[17]
practicability and efficiency of the respective reaction.
A drawback of all known oxidation protocols is the
In addition to molecular oxygen, hydrogen peroxide, use of acidic solvents, i.e., acetic acid, or the necessity
H2O2, is the most “green”, and waste-avoiding oxi- to add inorganic acid catalysts, which causes environ-
dant.[1] It can oxidize organic compounds with an mental pollution and more seriously corrosion prob-
atom efficiency of 47% and generates theoretically lems on a larger scale. In general, a high concentra-
only water as co-product. Due to its properties H2O2 tion of hydrogen peroxide (50–83%) is needed in
is particularly useful for liquid-phase oxidations for order to get acceptable yields of menadione.[11] This
the synthesis of fine chemicals, pharmaceuticals, and may lead to explosive mixtures and causes severe
electronic materials.[2] Recently, we became interested safety problems.[17] Thus, the development of selective
in the development of novel catalysts for catalytic ep- oxidations of 2-methylnaphthalene and its derivatives
oxidations using hydrogen peroxide.[3] Herein, we which work under neutral conditions with easy to use
report for the first time our results on the ruthenium- hydrogen peroxide (30% aqueous solution) is still an
catalyzed oxidation of arenes in the presence of important and challenging goal.
phase-transfer agents.
Based on our experience in the synthesis of ruthe-
nium(II) complexes with tridentate nitrogen ligands
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Feng Shi et al.
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and their application in oxidation catalysis,[3] we thesis of menadione (2) (Table 1). To our delight all
became interested in demonstrating the utility of such prepared Ru complexes catalyze the oxidation to give
complexes in arene oxidations. In exploratory experi- the corresponding 1,4-naphthoquinones (Table 1, en-
ments, the reaction of 2-methylnaphthalene with hy- tries 1–4).[3c,18] Apart from the desired menadione (2)
drogen peroxide (2.3 equivs.) in the presence of dif- also the regioisomeric product 3 is formed in a minor
ferent Ru catalysts was examined (Scheme 1).
amount. There is no significant influence of the cata-
lyst on the ratio of quinones 2 and 3, which is in be-
tween 2.5:1 and 2.9:1. Depending on the catalyst, con-
versions of 65–91% and isolated yields of 26–53%
are obtained. In addition benzoic acids are formed as
side-products in minor amounts.
The easily available catalyst 4 was next investigated
in more detail. Applying only a slight excess of hydro-
gen peroxide (1.2 equivs.) the best chemoselectivity
(86%) is observed (Table 1, entry 5). It is noteworthy
that the starting material can be recovered and re-
used for this oxidation protocol. Increasing the cata-
lyst concentration resulted in an increase of the un-
productive decomposition of hydrogen peroxide.
Hence, an excess of hydrogen peroxide has to be used
in order to get comparable yields (Table 1, entries 11
and 12). The addition of 1–2.5 mol% of phase-trans-
Scheme 1. Synthesis of 2-methyl-1,4-naphthoquinone (mena-
dione).
In general, 0.2 mol% of a ruthenium complex cata- fer catalysts 8 and 9 resulted in a significant improve-
lyzed the reaction at room temperature to 408C for ment of the catalyst activity (Table 1, entries 6, 8, 10,
1 h in the absence of any organic solvent. Owing to 13). For example, 2-methylnaphthalene was complete-
solubility problems the reactions were performed with ly consumed in 20 min in the presence of only 0.2
or without a catalytic amount of phase-transfer mol% of Ru catalyst 4 and 1 mol% of sodium dode-
agents. Among the various Ru complexes, Ru(II)(ter- cyl sulfate to give naphthoquinones 2 and 3 in 56%
pyridine)(2,6-pyridinedicarboxylate) (4) showed sig- isolated yield [catalyst turnover frequency (TOF)=
nificant activity. Thus, we prepared complexes 4–7 840 hÀ1]. Interestingly, both cationic and anionic
(Scheme 2) and studied their behaviour for the syn-
Scheme 2. Ruthenium catalysts and phase-transfer catalysts used for the synthesis of menadione (2).
304
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Selective Oxidation of Naphthalenes with Hydrogen Peroxide
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Table 1. Selective oxidation of 2-methylnaphthalene with different ruthenium catalysts.[a]
Entry Cat. [mol%] PTC [mol%] T [oC] 1/H2O2 Conversion[b] [%] Yield[c] [%] Selectivity [%] Ratio of 2:3[d]
1
2
3
4
5
6
7
8
4 (0.2)
5 (0.2)
6 (0.2)
7 (0.2)
4 (0.2)
4 (0.2)
4 (0.2)
4 (0.2)
4 (0.2)
4 (0.2)
4 (0.5)
4 (1.0)
4 (0.2)
-
-
-
-
40
40
40
40
40
40
40
40
40
40
40
40
r.t.
1:7
1:7
1:7
1:7
1:3.6
1:3.6
1:7
67
65
91
88
58
70
67
88
65
97
73
58
99
51
32
26
53
50
54
51
64
49
52
56
41
56
77
50
29
61
86
77
77
73
75
54
77
71
56
2.8:1
2.7:1
2.9:1
2.5:1
2.9:1
3.2:1
3.1:1
3.0:1
2.9:1
3.0:1
2.9:1
2.9:1
2.8:1
-
8 (2.5)
-
8 (2.5)
-
8 (2.5)
-
-
1:7
9
1:10
1:10
1:7
1:10
1:3.6
10
11
12
13
9 (1)
[a]
[b]
[c]
[d]
1 mmol of starting material, 0.5 mL of H2O.
Conversion was determined by GC.
Isolated yield of quinones 2 and 3.
1
The ratio between products 2 and 3 was determined by GC and H NMR.
phase-transfer catalysts showed a similar rate in- 2.5 mol% 8 (catalyst system A), and 0.2 mol% 4+1
crease. mol% 9 (catalyst system B) were further employed in
To demonstrate the usefulness of our novel proto- the oxidation of electron-rich and electron-poor naph-
col the most effective catalyst systems, 0.2 mol% 4+ thalenes (Table 2). For this comparative study, naph-
Table 2. Selective oxidation of different naphthalene derivatives.[a]
Entry Substrate
Product[b]
Cat. t
Conversion
Yield
[%][c]
Selectivity
[%]
[h] [%]
1
A
B
1
1
95
39
59
55
40
61
99
2[d]
96
3
A
15 55
4[e]
B
21 83
64
50
77
90
5
A
15 55
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Feng Shi et al.
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Table 2. (Continued)
Entry Substrate
Product[b]
Cat. t
Conversion
Yield
[%][c]
Selectivity
[%]
[h] [%]
6[d,f]
B
A
B
14 94
48
26
10
51
26
10
7
1
1
100
100
8[d,f]
9[f]
A
B
A
B
15 83
14 53
18 61
0.5 96
58
53
38
51
83
99
63
53
10[d]
11
12[d]
13
A
B
15 83
35
54
40
60
14
15 90
[a]
1 mmol of starting material, catalyst A or B, 0.5 mL of H2O, 7 mmol (ca. 0.7 mL) of 30 wt% H2O2, 408C. A=0.2 mol%
of 4 + 2.5 mol% of 8; B=0.2 mol% of 4 + 1 mol% of 9.
The ratio between the products was determined by GC and H NMR.
Isolated yield.
Performed at room temperature.
1:H2O2 =1:10.
1:H2O2 =1:3.6.
[b]
[c]
[d]
[e]
[f]
1
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Selective Oxidation of Naphthalenes with Hydrogen Peroxide
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thalene, 2-ethylnaphthalene, 2,6-dimethylnaphthalene, General Procedure for Ruthenium-Catalyzed
2-methyl-1-hydroxynaphthalene, 2-chloronaphthalene, Selective Oxidation of Naphthalene Derivatives
2-bromonaphthalene, and anthracene were chosen as
representative substrates.
All reactions were carried out in an oil bath (408C) or di-
rectly in air (23–268C). To a glass reactor (40 mL), 1 mmol
Applying catalyst system B naphthalene furnished
the desired naphthoquinone in 59% isolated yield
(Table 2, entry 2). Noteworthy, methyltrioxorhenium
(MTO), a previous state-of-the-art catalyst for this
type of oxidation, gave only 11% yield for this sub-
strate.[11] The industrially important 2,6-dimethylnaph-
thalene and 2-ethylnaphthalene led to similar results
compared to 2-methylnaphthalene. Here, the isolated
yields of the corresponding naphthoquinones were
64% and 50%, respectively (Table 2, entries 3–6).
Full conversions but only low yields (up to 26%)
were obtained with 2-methyl-1-hydroxynaphthalene
as substrate (Table 2, entries 7 and 8). These results
demonstrate that A and B behave differently com-
pared to previously reported catalysts. In general, 2-
methyl-1-hydroxnaphthalene is considered to be the
key intermediate to yield menadione 2.[11,17] Appa-
rently, the oxidation mechanism is unlike to those
processes in acidic solvents or in the presence of acid
catalysts.
In addition to alkyl-substituted naphthalenes, the
selective oxidation of 2-chloronaphthalene and 2-bro-
monaphthalene could be carried out effectively (54%
and 60% yield, respectively). In the presence of other
catalysts often such electron-poor naphthalenes gave
only low yields of quinones. Finally, we investigated
the oxidation of anthracene. Here a mixture of 73%
of 9,10-anthraquinone and 27% of 1,4-anthraquinone
is obtained. Again using MTO as catalyst no quinone
was observed and only 2,2ꢀ-biphenyldicarboxylic acid
was isolated.[11]
(0.1442 g) of 2-methylnaphthalene, 0.002 mmol of
4
(1.0 mg), 0.025 mmol (7.9 mg) of tributylbenzylammonium
chloride, 0.5 mL of H2O and 7 mmol (ca. 0.7 mL) of 30 wt%
H2O2 were added, respectively. The reaction mixture was
vigorously stirred (750 t/min) at 408C for 1 hour. Then, the
mixture was cooled to room temperature, and extracted
with CH2Cl2 (20 mL”3). The solvent was removed in
vacuum and the naphthoquinones are isolated by column
chromatography (silica gel 60, 70–230 mesh, hexane:
EtOAc=8:2, v/v). A mixture of 2 and 3 (0.11 g, 64%) was
obtained, which were characterized by 1H NMR, GC-FID
(HP6890N with FID detector, column HP5MS 30 m”
0.250 mm”0.25 mm) and GC-MS (HP6890N with MSD5973,
column HP5MS 30 m”0.250 mm”0.25 mm) and compared
with the authentic sample of 2. The ratio of 2 and 3 was ca.
1
3:1. It was determined by H NMRand GC-FID (the same
1
ratios were obtained from both methods). Using H NMR
spectroscopy the ratio of 2 and 3 was determined by the in-
tegral of the methyl group signals (d=2.17–2.20, d and d=
2.49, s).
Product 2: 1H NMR(400.1 MHz, CDCl3): d=2.17–2.20
(3H, d, J=1.5 Hz), 6.80–6.85 (1H, q, J=1.5 Hz), 7.66–7.72
(m, 2H), 8.03–8.06 (m, 1H), 8.07–8.11 (m, 1H); GC-MS
(relative intensity): m/z=172 (M+, 100), 116 (33), 115 (43),
104 (39), 76 (27).
Product 3: 1H NMR(400.1 MHz, CDCl 3): d=2.49 (3H,
s), 6.93 (s, 2H), 7.52–7.57 (1H, m), 7.84–7.87 (1H, m), 7.94–
7.99 (1H, d, J=7.9 Hz); GC-MS (relative intensity): m/z=
172 (M+, 100), 118 (32), 115 (37), 89 (23).
Acknowledgements
This work has been supported by the State of Mecklenburg-
Western Pommerania and the Deutsche Forschungsgemein-
schaft (SPP 1118 and Leibniz prize). Dr. Feng Shi thanks the
Alexander-von-Humboldt-Stiftung for an AvH-Fellowship.
In summary, we have developed an easy to use Ru-
PTC catalyst system for the selective oxidation of
naphthalene derivatives. Good results are obtained
for alkyl-substituted naphthalenes and electron-poor
naphthalenes. The process needs only a small amount
of catalyst (0.2 mol%) and proceeds with water as
the solvent. Compared to previous protocols for this
type of reaction, there is no need for acidic solvents
and high concentrations of hydrogen peroxide, which
makes the reaction more environmentally friendly.
References
[1] a) C. W. Jones, Application of Hydrogen Peroxide and
Derivatives, Royal Society of Chemistry: Cambridge,
1999; b) G. Grigoropoulou, J. H. Clark, J. A. Elings,
Green Chem. 2003, 1, 1–7; c) N. Mizuno, K. Yamagu-
chi, K. Kamata, Coord. Chem. Rev. 2005, 249, 1944–
1956.
[2] a) R. S. Varma, K. P. Naicker, Org. Lett. 1999, 1, 189–
192; b) K. Sato, M. Aoki, J. Takagi, R. Noyori, J. Am.
Chem. Soc. 1997, 119, 12386–12387; c) S. Stankovic, J.
H. Espenson, J. Org. Chem. 2000, 65, 2218–2221; d) E.
Baciocchi, M. F. Gerini, A. Lapi, J. Org. Chem. 2004,
69, 3586–3589; e) D. Sloboda-Rozner, P. L. Alsters, R.
Neumann, J. Am. Chem. Soc. 2003, 125, 5280–5281;
f) V. Kogan, M. M. Quintal, R. Neumann, Org. Lett.
2005, 7, 5039–5042; g) U. R. Pillai, Endalkachew Sahle-
Demessie, New J. Chem. 2003, 3, 525–528; h) D.
Experimental Section
Reagents and Methods
Ruthenium complexes were prepared according to previous-
ly reported methods.[3c,18] H2O2 (29–31%) was purchased
from Merck. Naphthalene, 2-methylnaphthalene, 2,6-dime-
thylnaphthalene, 2-ethylnaphthalene, 2-chloronaphthalene,
2-bromonaphthalene, tributylbenzyl ammonium chloride
and sodium dodecyl sulfate were of analytical purity and
used without further purification.
Adv. Synth. Catal. 2007, 349, 303 – 308
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
307

Feng Shi et al.
COMMUNICATIONS
Choudhary, S. Paul, R. Gupta, J. H. Clark, Green
Chem. 2006, 5, 479–482; i) E. A. Gutkina, V. M. Tru-
khan, C. G. Pierpont, S. Mkoyan, V. V. Strelets, E.
Nordlander, A. A. Shteinman, Dalton Trans. 2006, 3,
492–501; j) S. Taktak, M. Flook, B. M. Foxman, L.
Que, Jr., E. V. Rybak-Akimova, Chem. Commun. 2005,
42, 5301–5303.
[6] a) R. P. Kreh, R. M. Spotnitz, J. T. Lundquist, J. Org.
Chem. 1989, 54, 1526–1531; b) M. Periasamy, M. V.
Bhatt, Tetrahedron Lett. 1978, 19, 4561–4562.
[7] a) L. F. Fieser, J. Biol. Chem. 1940, 133, 391–396;
b) R. A. Sheldon, J. Dakka, Catal. Today 1994, 19, 215–
245.
[8] T. Takai, E. Hata, T. Mukaiyama, Chem. Lett. 1994,
885–886.
[3] a) M. Klawonn, M. K. Tse, S. Bhor, C. Dçbler, M.
Beller, J. Mol. Catal. A: Chem. 2004, 218, 13–19;
b) M. K. Tse, C. Dçbler, S. Bhor, M. Klawonn, W. Mä-
gerlein, H. Hugl, M. Beller, Angew. Chem. Int. Ed.
2004, 43, 5255–5260; c) M. K. Tse, M. Klawonn, S.
Bhor, C. Dçbler, G. Anilkumar, M. Beller, Org. Lett.
2005, 7, 987–990; d) S. Bhor, G. Anilkumar, M. K. Tse,
M. Klawonn, C. Dçbler, B. Bitterlich, A. Grotevendt,
M. Beller, Org. Lett. 2005, 7, 3393–3396; e) G. Anilku-
mar, S. Bhor, M. K. Tse, M. Klawonn, B. Bitterlich, Tet-
rahedron: Asymmetry 2005, 16, 3536–3561; f) M. K.
Tse, S. Bhor, M. Klawonn, C. Dçbler, W. Mägerlein, H.
Hugl, A. Spannenberg, M. Beller, Chem. Eur. J. 2006,
12, 1855–1874; g) M. K. Tse, S. Bhor, M. Klawonn, C.
Dçbler, W. Mägerlein, H. Hugl, H.-j. Jiao, M. Beller,
Chem. Eur. J. 2006, 12, 1875–1888; h) M. K. Tse, H.-J.
Jiao, G. Anilkumar, B. Bitterlich, F. G. Gelalcha, M.
Beller, J. Organomet. Chem. 2006, 691, 4419–4433.
[4] a) J. Rodriguez, E. Quinoa, R. Riguera, B. M. Peters,
L. M. Abrell, P. Crews, Tetrahedron 1992, 48, 6667–
6680; b) L. F. Fieser, M. Tushler, W. L. Sampson, J.
Biol. Chem. 1941, 137, 659–692.
[9] S. Yamazaki, Tetrahedron Lett. 2001, 42, 3355–3357.
[10] R. Neumann, M. de LaVega, J. Mol. Catal. 1993, 84,
93–108.
[11] a) W. A. Herrmann, J. D. G. Correia, R. W. Fischer, J.
Mol. Catal. A: Chem. 1999, 138, 115–121; b) W. Adam,
W. A. Herrmann, J. Lin, C. R. Sahamçller, R. W. Fisch-
er, J. D. G. Correia, Angew. Chem. Int. Ed. Eng. 1994,
33, 2475–2477.
[12] S. Yamaguchi, M. Inoue, S. Enomoto, Chem. Lett. 1985,
827–828.
[13] J. Skaryewski, Tetrahedron 1984, 40, 4997–5000.
[14] a) A. B. Sorokin, S. Mangematin, C. Pergrale, J. Mol.
Catal. A: Chem. 2002, 182–183, 267–281; b) A. B. Soro-
kin, A. Tuel, Catal. Today 2000, 57, 45–59; c) A. B. Sor-
okin, A. Tuel, New J. Chem. 1999, 23, 473–476; d) S. V.
Barkanova, V. M. Derkacheva, O. V. Dolotova, V. D.
Li, V. M. Negrimovsky, O. L. Kaliya, E. A. Lukꢀyanets,
Tetrahedron Lett. 1996, 37, 1637–1640.
[15] R. Song, A. Sorokin, J. Bernadou, B. Meunier, J. Org.
Chem. 1997, 62, 673–678.
[16] O. A. Anunyiata, L. B. Pierella, A. R. Beltramone, J.
Mol. Catal. A: Chem. 1999, 149, 255–261.
[5] a) S. Chocron, M. Michman, Appl. Catal. 1990, 62,
119–123; b) M. Juaristi, J. M. Aiypurua, B. Lecea, C.
Palomo, Can. J. Chem. 1984, 62, 2941–2944; c) R. A.
Sheldon, J. K. Kochi, Metal-catalyzed Oxidation of Or-
ganic Compounds, Academic Press, New York, 1981;
d) R. A. Sheldon, Top. Curr. Chem. 1993, 164, 21–34.
[17] A. Bohle, A. Schubert, Y. Sun, W. R. Thiel, Adv. Synth.
Catal. 2006, 348, 1011–1015.
[18] H. Nishiyama, T. Shimada, H. Itoh, H. Sugiyama, Y.
Motoyama, Chem. Commun. 1997, 1863–1864.
308
www.asc.wiley-vch.de
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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