A New Convenient Synthesis of Alkoxyanthracenes from Alkoxy-9,10- anthraquinones

Article abstract of DOI:10.1055/s-2003-42408

Methoxy-9,10-anthraquinones with mono-, di- and tetraether groups at different positions 1a-h can be directly reduced to the corresponding methoxyanthracenes 3a-h in moderate to good yields by zinc in refluxing acetic acid. Under similar conditions, ethyl 1′-anthracenoxyacetate (3i) with the ester group unaffected and 1,8-oxybis(ethyleneoxyethyleneoxy)anthracene (5) were also conveniently synthesized in 65 and 70% yields, respectively.

Full text of DOI:10.1055/s-2003-42408

2464
SHORT PAPER
A New Convenient Synthesis of Alkoxyanthracenes from Alkoxy-9,10-anthra-
quinones
A
N
ewConven
i
ient Sy
n
nthesis of
A
l
g
koxyanthrac
a
enes from
A
n
lkoxy-9,10-
g
anthraquinones Lu, Qiyin Chen, Xiaozhang Zhu, Chuanfeng Chen*
Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, P. R. China
Fax +86(10)62559373; E-mail: cchen@iccas.ac.cn
Received 27 June 2003; revised 6 August 2003
Abstract: Methoxy-9,10-anthraquinones with mono-, di- and tetra-
ether groups at different positions 1a–h can be directly reduced to
Zn/HOAc/reflux 30h
the corresponding methoxyanthracenes 3a–h in moderate to good
yields by zinc in refluxing acetic acid. Under similar conditions,
ethyl 1 -anthracenoxyacetate (3i) with the ester group unaffected
and 1,8-oxybis(ethyleneoxyethyleneoxy)anthracene (5) were also
conveniently synthesized in 65 and 70% yields, respectively.
O
OMe
OMe
OMe
2
p-chloranil
OMe O
OMe
Zn/HOAc/reflux 16h
1a
Key words: reduction, alkoxy-9,10-anthraquinones, alkoxyan-
thracene, zinc
OMe
3a
Scheme 1
Alkoxyanthracenes have attracted considerable interest
due to their photochromic properties for the construction
of photoresponsive supramolecular systems1 and on ac-
count of their unique chemical reactive properties for the
synthesis of triptycenes and triptycene quinones.2 The re-
ductive aromatization of the related alkoxy-9,10-an-
thraquinones provides the most effective route to some
alkoxyanthracenes, but the proper reductive system must
be selected.3 The reduction reaction can usually be
achieved by either excess sodium borohydride4 or compli-
cated sodium borohydride-metal (Na or Li)-ammonia/p-
chloranil system5 in a stepwise procedure. Although one-
step reductive system of zinc/aqueous ammonia,6 zinc/
aqueous sodium hydroxide7 or zinc/cyclohexyl-p-tolu-
enesulfonate/hot trichlorobenzene8 are sometimes possi-
ble, they are often unreliable or of limited substrate and
preparative value. Herein we report a new convenient
method to alkoxyanthracenes.
of a major new product. After work-up of the reaction, to
our surprise, we only obtained 1,8-dimethoxyanthracene
(3a) instead of 1,8-dimethoxy-9,10-dihydroanthracene
1
(2) in 75% yield. In the H NMR spectrum of the com-
pound 3a, the protons of H-9 and H-10 are positioned at
9.24 and 8.36 ppm, respectively. This result encouraged
us to examine the zinc/acetic acid system for the reduction
of other methoxy-9,10-anthraquinones 1b–h. After carry-
ing out the reaction for 12–24 hours and monitoring the
reaction by TLC for completion, the reactions were
quenched with ice water. As expected, the corresponding
methoxyanthracenes 3b–h as the final products were se-
lectively formed and were separated by column chroma-
tography over silica gel in moderate to good yields
(Scheme 2, Tables 1 and 2).
R4
R3
R4
O
R3
In the course of our studies on the construction of novel
macrocyclic compounds and new supramolecular sys-
tems, we needed 1,8-dimethoxy-9,10-dihydroanthracene
(2) and some alkoxyanthracenes including 1,8-
dimethoxyanthracene (3a) as starting materials. After ex-
amining the literature, we followed Müller’s procedure9 in
which 1,8-dimethoxy-9,10-anthraquinone (1a) was re-
duced by zinc in refluxing acetic acid for 30 hours to give
R5
R5
Zn/HOAc/reflux
R2
R2
R6
R1
R6
O
R1
1b–h
3b–h
Scheme 2
As shown in Scheme 2, methoxy-9,10-anthraquinones
with mono-, di- and tetraether groups at different posi-
tions could be directly reduced to the corresponding meth-
oxyanthracenes. Furthermore, the acidic reductive system
does not cleave the ether group present in the various
9,10-anthraquinones.6 Under the same condition, ethyl 1 -
anthracenoxyacetate (3i) could be selectively obtained
from the reduction of the related 9,10-anthraquinone de-
rivative 1i without affecting the ester group in 1i.
the
corresponding
1,8-dimethoxy-9,10-dihydroan-
thracene (2). Compound 2 can then be oxidized to 1,8-
dimethoxyanthracene 3a by p-chloranil5 (Scheme 1).
We found that when 1a was treated with zinc in refluxing
acetic acid for about 16 hours, the TLC showed the dis-
appearance of the starting material 1a and the formation
SYNTHESIS 2003, No. 16, pp 2464–2466
x
x.
x
x
.
2
0
0
3
We have also found that 1,8-oxybis(ethyleneoxyethyle-
Advanced online publication: 29.09.2003
DOI: 10.1055/s-2003-42408; Art ID: F05603SS
© Georg Thieme Verlag Stuttgart · New York
neoxy)-9,10-anthraquinone (4),14 prepared from the reac-

SHORT PAPER
A New Convenient Synthesis of Alkoxyanthracenes from Alkoxy-9,10-anthraquinones
2465
Table 1 Substituents in Compounds 1 and 3 (see Scheme 2)
tion of 1,8-dichloro-9,10-anthraquinone with tetraethyl-
ene glycol in anhydrous THF in the presence of sodium
hydride, could be easily reduced by zinc in refluxing ace-
tic acid to afford the 1,8-oxybis(ethyleneoxyethylene-
oxy)anthracene (5) in good yield (Scheme 3). In the H
NMR spectrum, the compound 5 showed two singlets at
1, 3
b
c
R1
R2
R3
H
R4
R5
H
R6
H
OMe
H
H
H
1
OMe
H
H
H
H
H
9.39 and 8.30 ppm for H-9 and H-10 , respectively.
d
e
OMe
OMe
H
OMe
H
H
H
H
H
OMe
H
H
H
O
f
OMe
OMe
H
H
OMe
H
H
Zn/HOAc/reflux 7h
g
OMe
OMe
OCH2CO2Et
H
OMe
OMe
H
OMe
OMe
H
O
O
O
O
O
70%
h
i
OMe
H
H
O
O
O
O
O
O
H
H
4
5
Scheme 3
Table 2 Alkoxyanthracenes 3 and Compound 5 Prepared
Sub-
strate
Prod-
uct
Time
(h
Yield
(%)
mp
Lit. mp (°C) or
1H NMR (CDCl3)c
, J (Hz
(°C)a
Molecular Formulab
1a
3a
16
75
195–196
1975
9.24 (s, 1 H), 8.32 (s, 1 H), 7.57 (d, J = 8.50, 2 H), 7.38 (dd,
J = 8.50, 7.47, 2 H), 6.74 (d, J = 7.47, 2 H), 4.09 (s, 6 H,
OCH3)
1b
3b
12
75
70–71
70–7210
8.86 (s, 1 H), 8.39 (s, 1 H), 8.05–8.08 (m, 1 H), 7.99–8.02 (m,
1 H), 7.60 (d, J = 8.56, 1 H), 7.45–7.50 (m, 2 H), 7.39 (dd,
J = 8.56, 7.37, 1 H), 6.76 (d, J = 7.37, 1 H), 4.11 (s, 3 H,
OCH3)
1c
3c
12
71
183–184
183.1–183.611
8.36 (s, 1 H), 8.29 (s, 1 H), 7.94–7.99 (m, 2 H), 7.90 (d,
J = 9.11, 1 H), 7.41–7.46 (m, 2 H), 7.21 (s, 1 H), 7.18 (d,
J = 9.11, 1 H), 3.98 (s, 3 H, OCH3)
1d
1e
1f
3d
3e
3f
15
12
24
62
70
60
134–136
227–228
261–262
134–1364a
2288
8.79 (s, 2 H), 8.03–8.07 (m, 2 H), 7.47–7.50 (m, 2 H), 6.62 (s,
2 H), 4.04 (s, 6 H, OCH3)
8.80 (s, 2 H), 7.65 (d, J = 8.54, 2 H), 7.37 (dd, J = 8.54, 7.39,
2 H), 6.77 (d, J = 7.39, 2 H), 4.09 (s, 6 H, OCH3)
260–2625
8.23 (s, 2 H), 7.56 (d, J = 8.96, 2 H), 7.20 (s, 2 H), 7.17 (d,
J = 8.96, 2 H), 4.09 (s, 6 H, OCH3)
1g
1h
3g
3h
24
24
50
52
297–299
128–130
298–30012
9.12 (s, 2 H), 6.65 (s, 4 H), 4.05 (s, 12 H, OCH3)
C18H18O4 (298.12)
9.00 (s, 1 H), 8.74 (s, 1 H), 7.83 (d, J = 9.15, 1 H), 7.38 (d,
J = 9.15, 1 H), 6.60 (ABq, 2 H), 4.11(s, 3 H, OCH3), 4.06 (s,
6 H, OCH3), 4.04 (s, 3 H, OCH3)d
1i
4
3i
5
6
7
65
70
oil
C18H16O3 (280.11)
C22H24O5 (368.37)
8.99 (s, 1 H), 8.40 (s, 1 H), 8.10–8.13 (m, 1 H), 8.00–8.03 (m,
1 H), 7.67 (d, J = 8.57, 1 H), 7.48–7.54 (m, 2 H), 7.35 (dd,
J = 8.57, 7.38, 1 H), 6.66 (d, J = 7.38, 1 H), 4.90 (s, 2 H), 4.37
(q, J = 7.13, 2 H), 1.35 (t, J = 7.13, 3 H)d
157–158
9.39 (s, 1 H), 8.30 (s, 1 H), 7.56 (d, J = 8.56, 2 H), 7.35 (dd,
J = 8.56, 7.34, 2 H), 6.69 (d, J = 7.34, 2 H), 4.36 (t, J = 3.79,
4 H), 4.16 (t, J = 3.79, 4 H) 3.88–3.95 (m, 8 H)d
a Uncorrected.
b Satisfactory microanalyses obtained: C 0.17, H 0.11.
c Recorded on Bruker AM-300 spectrometer.
d 13C NMR (CDCl3)c: 3h: = 55.5, 57.1, 61.1, 100.2, 100.9, 114.0, 116.7, 120.8, 124.3, 125.1, 125.6, 127.5, 128.5, 142.4, 147.0, 149.3, 149.4;
3i: = 14.1, 61.4, 65.6, 102.7, 121.3, 121.6, 124.7, 125.2, 125.6, 125.7, 127.8, 128.8, 131.3, 132.0, 132.5, 153.6, 168.8; 5: = 68.6, 69.2,
70.2, 71.4, 102.2, 116.4, 120.4, 124.5, 125.0, 125.6, 132.9, 155.1.
Synthesis 2003, No. 16, 2464–2466 © Thieme Stuttgart · New York

2466
L. Lu et al.
SHORT PAPER
In conclusion, a new convenient method to prepare
alkoxyanthracenes with the ether group at different posi-
tion has been presented and it may be generally applicable
in the synthesis of alkoxyanthracenes.
References
(1) (a) Bouas-Laurent, H.; Desvergne, J. P.; Fages, F.; Marsau,
P. In Fluorescent Chemosensors for Ion and Molecule
Recognition; Czarnik, A. W., Ed.; Oxford University Press:
Oxfoed, 1992, 59. (b) Brotin, T.; Desvergne, J. P.; Fages, F.;
Utermohlen, R.; Bonneau, R.; Bouas-Laurent, H.
Photochem. Photobiol. 1992, 55, 349.
(2) Hua, D. H.; Tamura, M.; Huang, X.; Stephany, H. A.;
Helfrich, B. A.; Perchellet, E. M.; Sperfslage, B. J.;
Perchellet, J.; Jiang, S.; Kyle, D. E.; Chiang, P. K. J. Org.
Chem. 2002, 67, 2907.
(3) Syamasundar, N.; Caluwe, P. J. Org. Chem. 1981, 46, 1552.
(4) (a) Criswell, T. R.; Klanderman, B. H. J. Org. Chem. 1974,
39, 770. (b) Pozzo, J.; Clavier, G. M.; Colomes, M.; Bouas-
Laurent, H. Tetrahedron 1997, 53, 6377. (c) Tius, M. A.;
Gomes-Galeno, J.; Zaidi, J. H. Tetrahedron Lett. 1988, 29,
6909.
(5) Syamasundar, N.; Caluwe, P. J. Org. Chem. 1981, 46, 809.
(6) Cook, J. W.; Pausen, P. L. J. Chem. Soc. 1949, 2726.
(7) Rabideau, P. W. J. Org. Chem. 1971, 36, 2723.
(8) Cameron, D. W.; Schütz, P. E. J. Chem. Soc., C 1967, 2121.
(9) Prinz, H.; Burgemeister, T.; Wiegrebe, W.; Müller, K. J.
Org. Chem. 1996, 61, 2857.
Methoxy-9, 10-anthraquinones 1a–h were prepared from the corre-
sponding available hydroxyl-substituted 9,10-anthraquinones and
dimethyl sulfate in anhyd acetone in the presence of anhyd
K2CO3.13 Similarly, compound 1i was prepared in 85% yield from
1-hydroxy-9,10-anthraquinone and ethyl bromoacetate. 1,8-Oxy-
bis(ethyleneoxyethyleneoxy)-9,10-anthraquinone (4) was prepared
from 1,8-dichloro-9,10-anthraquinone and tetraethylene glycol in
anhyd THF in the presence of NaH according to the literature.14
Reduction of Alkoxy-9,10-anthraquinones 1 and 1,8-Oxybis-
(ethyleneoxyethyleneoxy)-9,10-anthraquinone (4); General
Procedure
To a suspension of 1 or 4 (1.0 mmol) in glacial AcOH (30 mL) was
added zinc dust (1.7 g, 26 mmol) in one portion. The reaction mix-
ture was refluxed for 6–24 h. After the reaction was complete (mon-
itored by TLC), the mixture was poured into ice water and extracted
with CH2Cl2. The combined organic phase was washed with H2O
and sat. aq solution of NaHCO3, respectively, and then dried
(Na2SO4). After removal of the solvent in vacuo, the residue was
separated by column chromatography over silica gel to afford the
corresponding alkoxyanthracene 3 or 1,8-oxybis(ethyleneoxyethyl-
eneoxy)-9,10-anthracene (5) (Tables 1 and 2).
(10) Fitzgerald, J. J.; Drysdale, N. E.; Olofson, R. A. J. Org.
Chem. 1992, 57, 7122.
(11) Haddon, R. C. Aust. J. Chem. 1982, 35, 1733.
(12) Fitzgerald, J. J.; Drysdale, N. E.; Olofson, R. A. Synth.
Commun. 1992, 22, 1807.
(13) Sharghi, H.; Tamaddon, F. Tetrahedron 1996, 52, 13623.
(14) Delgado, M.; Gustowski, D. A.; Yoo, H. K.; Gatto, V. J.;
Gokel, G. W.; Echegoyen, L. J. Am. Chem. Soc. 1988, 110,
119.
Acknowledgment
This work was supported by the Chinese Academy of Sciences and
the National Natural Foundation of China.
Synthesis 2003, No. 16, 2464–2466 © Thieme Stuttgart · New York