Aerobic oxidation of hydroquinones to quinones catalyzed by VO(acac)2

Article abstract of DOI:10.1055/s-1999-2545

In the presence of a catalytic amount of VO(acac)₂, oxidation of hydroquinone and its derivatives with molecular oxygen at room temperature gave the corresponding quinones in moderate to high yields.

Full text of DOI:10.1055/s-1999-2545

LETTER
77
Aerobic Oxidation of Hydroquinones to Quinones Catalyzed by VO(acac)2
Der-Ren Hwang, Chang-Ying Chu, Sheng-Kai Wang, and Biing-Jiun Uang*
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300, Republic of China
Fax: +886-3-5711082; E-mail:bjuang@faculty.nthu.edu.tw
Received 13 November 1998
similar results were observed. A particular case of note is
the trisubstituted hydroquinone 5a in which an excellent
yield of the corresponding quinone 5b was obtained. To
test the scope of this catalytic system, tert-butyl, phenyl,
bromo and thiophenyl substituted hydroquinones 6a-9a
were investigated and were found to tolerate this catalytic
system. In the case of phenylthioquinone 9a, only the de-
sired quinone 9b was obtained as the reaction product and
no over-oxidation product (sulfoxide or sulfone) was de-
tected. The oxidation of hydroquinone was suppressed
when the reaction was conducted in methanol or other po-
lar solvent, such as ethanol and acetonitrile.
Abstract: In the presence of a catalytic amount of VO(acac) , oxi-
2
dation of hydroquinone and its derivatives with molecular oxygen
at room temperature gave the corresponding quinones in moderate
to high yields.
Key words: hydroquinones, quinones, oxidation, molecular oxy-
gen, vanadyl acetylacetonate
Substituted quinones are not only present as common
1
units in nature products but also used as very useful inter-
2
mediates in organic synthesis. A wide variety of oxidants
that oxidize hydroquinones to quinones has been reported.
Among these methods, there are some common stoichio-
3
metric oxidation methods that use chromium trioxide, so-
4
5
6
dium hypochlorite, iron(III) chloride, silver oxide,
7
silver carbonate/celite, or cerium(IV) ammonium nitrate/
silica as the oxidants. Catalytic oxidations using nitrogen
oxides/O , alumina-supported copper(II) sulfate/O and
copper (II)/persulfate have been reported recently.
These methods required either stoichiomeric amounts of
oxidants or tedious reaction conditions even though they
were used in catalytic amounts. However, oxovanadium
complexes have been found to have specific catalytic ac-
8
9
10
2
2
1
1
1
2
tivity especially in oxidation reactions, and we found
that vanadyl acetylacetonate (VO(acac) ), a stable, com-
2
mercially available and very inexpensive catalyst was ca-
pable to catalyze ortho coupling of phenols to biphenols
1
3
with molecular oxygen. In an extension to this work we
report herein an effective conversion of hydroquinones to
the corresponding quinones with molecular oxygen in the
presence of catalytic amount of VO(acac)2.
Oxidation of 3,5-di-tert-butylpyrocatechol 1a with mo-
lecular oxygen in the presence of VO(acac) was found to
2
give the corresponding quinone 1b in 15% yield along
1
4
with the formation of 1c and 1d (eq. 1). When similar
conditions were applied to the reaction of catechol, main-
ly starting material was recovered after 10 h, along with
the formation of some unknown black powder that was in-
soluble in any organic solvent. A possible reason might be
that the catechol had chelated with vanadium ion to form
1
5
a stable complex. However, when hydroquinone 2a was
reacted with molecular oxygen in the presence of a cata-
lytic amount of VO(acac) in dichloromethane at room
2
temperature, quinone 2b was obtained in 75 % yield after
column chromatographic purification of the resulting
mixture (eq.2). The reaction is basically very clean as
judged by thin layer chromatography. Subsequently,
mono-, di- and trimethyl-hydroquinones 3a-5a were ex-
amined under the same reaction conditions (Table 1), and
Synlett 1999, No. 1, 77–78 ISSN 0936-5214 © Thieme Stuttgart · New Yorkrk

7
8
D.-R. Hwang et al.
LETTER
A possible mechanism for the vanadium catalyzed oxida- short column of silica gel and eluted with ethyl acetate
tion of hydroquinones is depicted in Figure 1. The oxida- (100 mL). The filtrate was concentrated and purified by
tive reaction may start from a partial disproportionation of column chromatography (SiO , hexane : ethyl acetate =
2
o
9
oxovanadium(IV) complex to the corresponding vanadi- 10 : 1) to afford quinone 5b (362mg, 97%, mp 29 C; lit.
1
6
o
um(III) and vanadium(V). Vanadium(V) complex oxi- mp 31-32 C)
dizes hydroquinone to the corresponding quinone and
becomes vanadium(III). Then, molecular oxygen oxidizes
Acknowledgement
vanadium(III) to vanadium(V) and generates one mole of
hydrogen peroxide. This constitutes the catalytic cycle.
1
7
We are grateful to the National Science Council, Republic of China
for support of this work.
References and Notes
(1) Corey, E. J.; Cheng, X.-M. The Logic of Chemical Synthesis;
Wiley: New York, 1989, pp362-425.
(
2) (a) Thomson, R. H. In The Chemistry of Quinonoid Com-
pounds, Part I; Patai, S., Ed.; Wiley; New York, 1974; p111.
(
b) Naruta, Y.; Maruyama, K. In The Chemistry of Quinonoid
Compounds; Patai, S.; Rappoport, Z., Eds.; Wiley; New York,
988; pp241-402.
1
(
(
(
3) Kohn, M.; Sussmann, J. J. Monatsh. Chem. 1927, 48, 203.
4) Ishii, F.; Kishi, K.-I. Synthesis 1980, 706.
5) Jempty, T. C.; Gogins, K. A. Z.; Mazur, Y.; Miller, L. L. J.
Org. Chem. 1981, 46, 4545.
(
(
6) Willstatter, R.; Pfannenstiel, A. Chem. Ber. 1904, 37, 4744.
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1339.
(8) Fischer, A.; Henderson, G. N. Synthesis 1985, 641.
(
9) Bosch, E.; Rathore, R.; Kochi, J. K. J. Org. Chem. 1994, 59,
2
529.
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(
3
Figure 1
(
11) Costantini, C.; d’Ischia, M.; Prota, G. Synthesis 1994, 1399.
(12) For the recent review see: Hirao, T. Chem. Rev. 1997, 97,
2707.
In conclusion, an efficient and simple method for the oxi- (13) Hwang, D. R.; Chen, C. P.; Uang, B. J. submitted for publica-
dation of hydroquinone and its derivatives to the corre-
sponding quinones has been demonstrated. This method
tion.
(
14) Tatsuno, Y.; Tatsuda, M.; Otsuka, S. J. Chem. Soc., Chem.
Commun. 1982, 1100.
employs VO(acac) , a stable, commercially available and
2
(
15) Vilas Boas, L. F.; Costa Pessoa, J. In Comprehensive Coordi-
nation Chemistry: the synthesis, reactions, properties and ap-
plications of coordination compounds; Wilkinson, J.; Gillard,
R.D.; McCleverty, J., Eds; Pergamon Press: New York, 1987;
vol. 3; pp502-504.
16) Yamamoto, K. ; Oyaizu, K.; Iwasaki, N.; Tsuchida, E. Chem.
Lett. 1993, 1223.
17) Yamamoto, K.; Tsuchida, E.; Nishide, H.; Jikei, M.; Oyaizu,
K. Macromolecules 1993, 26, 3432.
very inexpensive catalyst, and molecular oxygen to oxi-
dize hydroquinone to quinone at room temperature in
moderate to high yields.
A typical procedure follows: A stirred mixture of hydro-
(
quinone 5a (380 mg, 25 mmol), and VO(acac) (66.3 mg,
2
0
.1 mmol) in dichloromethane (25 mL) was exposed to an
(
atmospheric pressure of molecular oxygen at room tem-
perature for 14 h. The mixture was then filtered through a
Synlett 1999, No. 1, 77–78 ISSN 0936-5214 © Thieme Stuttgart · New York