Oxidative aromatization of 9,10-dihydroanthracenes using molecular oxygen promoted by activated carbon

Article abstract of DOI:10.1021/jo034995q

Substituted 9,10-dihydroanthracenes were oxidatively aromatized to the corresponding anthracenes effectively by using molecular oxygen as an oxidant and activated carbon (Darco KB, Aldrich, Inc.) as a promoter in xylene.

Full text of DOI:10.1021/jo034995q

TABLE 1. Ar om a tiza tion of 9,10-Dih yd r oa n th r a cen e
Oxid a tive Ar om a tiza tion of
9,10-Dih yd r oa n th r a cen es Usin g Molecu la r
Oxygen P r om oted by Activa ted Ca r bon
Natsuki Nakamichi, Hirotoshi Kawabata, and
Masahiko Hayashi*
entry
catalyst
10% Pd/C
yieldb (%)
Department of Chemistry, Faculty of Science,
Kobe University, Kobe 657-8501, J apan
1
2
3
4
93
36 (63)
93
Pd black
activated carbona
none
mhayashi@kobe-u.ac.jp
Received J uly 11, 2003
8 (92)
Darco KB (Aldrich, Inc.). Determined by 1H NMR analyses.
The values in the parentheses indicate the yield of recovered 1.
a
b
Abstr a ct: Substituted 9,10-dihydroanthracenes were oxi-
datively aromatized to the corresponding anthracenes ef-
fectively by using molecular oxygen as an oxidant and
activated carbon (Darco KB, Aldrich, Inc.) as a promoter in
xylene.
TABLE 2. Effect of Activa ted Ca r bon
The aromatization of polycyclic hydroaromatic com-
pounds such as substituted 9,10-dihydroanthracenes has
been investigated so far.1 Several methods have been
reported which include the oxidative aromatization by
chloranil2 or DDQ,3 the dehydrogenative aromatization
by Pd/C,3,4 and the aromatization employing RhCl-
(PPh3)3,4 trityl salts,5 n-BuLi/N,N,N′,N′-tetramethyleth-
ylenediamine (TMEDA)/MeI,6 etc. However, these meth-
ods require a stoichiometric or an excess amount of the
oxidants in most cases. Furthermore, in some cases an
extremely high temperature is necessary. Therefore, a
more efficient process using oxygen as an oxidizing agent
with the aid of effective catalyst has been desired from
an environmental viewpoint. More recently, Yamada
reported the oxidative aromatization with oxygen cata-
lyzed by ruthenium porphyrin complex.7 In this paper,
we report an environmentally friendly method for the
oxidative aromatization of several 9,10-dihydroanthracenes
using molecular oxygen promoted by inexpensive and
readily available activated carbon.
activated
carbon
surface areaa
(m2/g)
Feb
(ppm)
yieldd
(%)
entry
1
2
3
Darco KB
Darco KB-B
Darco G-60
1500
1500
600
299 (N.D.)c
98.3 (100)
175 (200)
85 (14)
91 (8)
50 (48)
a
b
Data from Aldrich, Inc. Measured by ICP-AES. The values
in the parentheses indicate the data from Aldrich, Inc. c No data.
Determined by 1H NMR analyses. The values in the parentheses
d
indicate the yield of recovered 1.
Table 1). When the reaction was carried out in the
presence of 50 wt % of Pd black (entry 2), the aromati-
zation proceeded slowly (36% yield) and the starting
material was recovered in 63% yield. Based on these
results, we assumed that the activated carbon might play
an important role in this reaction. Actually, the reaction
proceeded by employing the activated carbon without any
palladium sources (entry 3). That is, treatment of 9,10-
dihydroanthracene (1) with 50 wt % of activated carbon
(Darco KB, Aldrich, Inc.) in xylene under an oxygen
atmosphere at 120 °C for 15 h produced anthracene (2)
in 93% yield.9
We then examined the aromatization of 9,10-dihy-
droanthracene (1) by using the three types of activated
carbon, that is, Darco KB, Darco KB-B, and Darco G-60
(Table 2). It was found that the use of Darco KB and
Darco KB-B, which had larger surface area compared to
Darco G-60, exhibited higher activity in the conversion
of 9,10-dihydroanthracene (1) to the corresponding aro-
matized anthracene (2) (entries 1 and 2). We measured
the contents of metals in the above three types of
activated carbon by inductively coupled plasma atomic
emission spectroscopy (ICP-AES). Among the metals we
observed, the content of Fe should be noted.10 That is,
We first examined the aromatization of 9,10-dihy-
droanthracene (1) using a Pd/C catalyst.8 As a result, we
found that the reaction using 50 wt % of 10% Pd/C under
an oxygen atmosphere in xylene at 120 °C exhibited high
performance in this conversion (93% yield, entry 1 in
* To whom correspondence should be addressed. Fax: +81-78-803-
5688.
(1) Fu, P. P.; Harvey, R. G. Chem. Rev. 1978, 78, 317.
(2) Braude, E. A.; J ackman, L. M.; Linstead, R. P. J . Chem. Soc.
1954, 3564.
(3) Harvey, R. G.; Arzadon, L.; Grant, J .; Urberg, K. J . Am. Chem.
Soc. 1969, 91, 4535.
(4) Blum, J .; Biger, S. Tetrahedron Lett. 1970, 11, 1825.
(5) (a) Bonthrone, W.; Reid, D. H. J . Chem. Soc. 1959, 2773. (b) Fu,
P. P.; Harvey, R. G. Tetrahedron Lett. 1974, 15, 3217.
(6) (a) Kitamura, M.; Shen, B.; Liu, Y.; Zheng, H.; Takahashi, T.
Chem. Lett. 2001, 646. (b) Harvey, R. G.; Cho, H. J . Am. Chem. Soc.
1974, 96, 2434. (c) Harvey, R. G.; Nazareno, L.; Cho, H. J . Am. Chem.
Soc. 1973, 95, 2376.
(7) (a) Tanaka, H.; Ikeno, T.; Yamada, T. Synlett 2003, 4, 576. (b)
Hashimoto, K.; Tanaka, H.; Ikeno, T.; Yamada, T. Chem. Lett. 2002,
582.
(9) Only slow conversion was observed even in the absence of
catalysts (120 °C, 15 h, 8% yield).
(10) The contents of metals other than Fe in Darco KB which might
concern this oxidative aromatization were as follows (ppm): Cu, 16.8
ppm; Mn, 9.99 ppm; Cr, 6.81 ppm. The contents of all metals in Darco
KB, Darco KB-B, and Darco G-60 are listed in the Supporting
Information.
(8) We recently reported the Pd/C catalyzed oxidative aromatization
of 1,3,5-trisubstituted pyrazolines and Hantzsch 1,4-dihydropyridines;
Nakamichi, N.; Kawashita, Y.; Hayashi, M. Org. Lett. 2002, 4, 3955.
10.1021/jo034995q CCC: $25.00 © 2003 American Chemical Society
Published on Web 09/16/2003
8272
J . Org. Chem. 2003, 68, 8272-8273

TABLE 3. Ar om a tiza tion of Va r iou s
9,10-Dih yd r oa n th r a cen esa
thracenes are summarized in Table 3. The 9,10-dihy-
droanthracenes bearing a variety of substituents were
treated with 50 wt % activated carbon (Darco KB) in
xylene under oxygen (120 °C, 15__32 h) to give the
corresponding substituted anthracenes in high yield
(79-90% yield).
In conclusion, we have disclosed an extremely simple
oxidative aromatization method to convert 9,10-dihy-
droanthracenes to the corresponding anthracenes using
molecular oxygen promoted by activated carbon.11 Fur-
ther investigations on the detail reaction mechanism
including the role of activated carbon are currently
underway.
Exp er im en ta l Section
Typ ica l P r oced u r e for Oxid a tive Ar om a tiza tion . A three-
necked flask was charged with 9,10-dihydroanthracene (1) 2.0
g (11.1 mmol), xylene12 (15 mL), and 1.0 g (50 wt %) of activated
carbon (Darco KB, Aldrich, Inc.) under an oxygen atmosphere
using a balloon. The whole was warmed to 120 °C and stirred
for 12 h at this temperature. After confirmation of the consump-
tion of starting material by TLC analysis, activated carbon was
filtered off using Celite. After washing with toluene, the filtrate
was evaporated and the resulting solid was purified by recrys-
tallization to give the desired anthracene (2) 1.7 g (86%) as a
yellow crystal: mp 216 °C (lit.13 mp 218 °C).
a
All reactions were carried out using 200-300 mg of substrate
and 50 wt % of activated carbon (Darco KB, Aldrich, Inc.) in xylene
(3.5 mL) at 120 °C under an oxygen atmosphere. Isolated yields
b
by recrystallizations. The values in the parentheses indicate the
yields determined by 1H NMR analyses.
Gen er a l P r oced u r e for Mea su r em en t of ICP -AE S. All
reagents used in this study were of analytical or special grade.
the following amount of Fe was observed in 1 g of
activated carbon: Darco KB, 299 ppm; Darco KB-B, 98.3
ppm; Darco G-60, 175 ppm. Among these activated
carbons we examined, Darco KB-B contained a smaller
amount of Fe; however, the reactivity of it was almost
the same with Darco KB, which contained a larger
amount of Fe. In these activated carbons, the important
difference is not the amount of Fe but the extent of
surface area: Darco KB, 1500 m2/g; Darco KB-B, 1500
m2/g; Darco G-60, 600 m2/g (data from Aldrich, Inc.).
Therefore, it would be considered that the extent of the
surface area would exhibit more important effect on
reactivity than the amount of Fe in the activated carbon.
At present, we assume that the activated carbon would
effectively adsorb oxygen to promote the reaction.
Wet digestion method: An accurately weighed activated
carbon (1.0 g) was digested with 20 mL of 2 M HNO3. After the
solution was shaken for 24 h at room temperature, activated
carbon was removed by filtration. Then, 5 mL of filtrate was
diluted with water to 50 mL. The resulting solution was analyzed
by ICP-AES (Varian Liberty Series II).
Dry digestion method: An accurately weighed activated
carbon (1.0 g) was heated for 6 h at 600 or 800 °C. After the
residue was cooled to room temperature, 2 mL of 12 M HCl was
added and heated gently. The insoluble material was filtrated,
and the filtrate was diluted with water to 100 mL. The resulting
solution was analyzed by ICP-AES.
Ack n ow led gm en t. This research was supported by
a Grant-in-Aid for Scientific Research from the Ministry
of Education, Culture, Sports, Science and Technology,
J apan. We also thank Ms. Yoshiko Murakami of
Yamaguchi University for measuring ICP-AES.
Several examples of the aromatization of 9,10-dihy-
droanthracene derivatives to the corresponding an-
(11) The present activated carbon (Darco KB, Aldrich, Inc.) also
promoted the reaction of Hantzsch 1,4-dihydropyridine to afford the
corresponding pyridine derivative in high yield. The detail of this
reaction will be published soon.
(12) We used an inexpensive mixture of o-, m-, and p-xylene.
(13) Merck Index, 13th ed.; Merck: Boca Raton, 2001; p 115.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and compound characterization data. This material
is available free of charge via the Internet at http://pubs.acs.org.
J O034995Q
J . Org. Chem, Vol. 68, No. 21, 2003 8273