Brominated thiophenes as precursors in the preparation of brominated and arylated anthraquinones

Article abstract of DOI:10.3390/molecules14031013

Brominated anthraquinones can be synthesized directly from bromothiophenes when these are reacted with 1,4-naphthoquinones in the presence of meta-chloroperoxybenzoic acid. The bromoanthraquinones are versatile building blocks in the preparation of arylated anthraquinones and of extended π-systems with interspersed anthraquinone units.

Full text of DOI:10.3390/molecules14031013

Molecules 2009, 14, 1013-1031; doi:10.3390/molecules14031013
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Brominated Thiophenes as Precursors in the Preparation of
Brominated and Arylated Anthraquinones
Thies Thiemann 1,* Yasuko Tanaka 2 and Jesus Iniesta 3
1
Interdisciplinary Graduate School of Engineering Sciences Kyushu University, 6-1, Kasuga-koh-en,
Kasuga-shi, Fukuoka 816-8580, Japan
2
Institute of Materials Chemistry and Engineering, Kyushu University, 6-1, Kasuga-koh-en, Kasuga-
shi, Fukuoka 816-8580, Japan
3
Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain;
E-mail: jesus.iniesta@ua.es (J.I.)
* Author to whom correspondence should be addressed; E-mail: thies@cm.kyushu-u.ac.jp.
Received: 22 January 2009; in revised form: 18 February 2009 / Accepted: 24 February 2009 /
Published: 4 March 2009
Abstract: Brominated anthraquinones can be synthesized directly from bromothiophenes
when these are reacted with 1,4-naphthoquinones in the presence of meta-chloroperoxy-
benzoic acid. The bromoanthraquinones are versatile building blocks in the preparation of
arylated anthraquinones and of extended π-systems with interspersed anthraquinone units.
Keywords: Anthraquinone; Oxidative cycloaddition; Suzuki cross coupling; UV
spectroscopy.
1. Introduction
Arylated anthraquinones 1 (Figure 1) have elicited interest in Physical Organic Chemistry [1,2] due
to the interaction of the attached aryl groups with the π-system of the anthraquinone core, as evidenced
in the corresponding UV and luminescence spectra [4,5], in the redox behavior of the molecules [2,3],
and their NMR shift values. Specifically, the interaction of the substituents on the anthraquinone C=O
function has been subjected to investigation [1]. In practical applications, arylated anthraquinones have

Molecules 2009, 14
1014
also been used as stabilizers of light-modulating fluids such as of fluids comprised of liquid
polybenzyltoluenes [6]. Our interest in these molecules is in the study of their electrochemical
behavior. In the following, a new direct preparation of arylated anthraquinones from bromothiophenes
is presented.
Figure 1. General Structure of arylated Anthraquinones.
A number of synthetic routes to arylated anthraquinones are known. It has been shown by
Bergmann et al. [7,8] that [4+2]-cycloaddition reactions of phenylbutadienes 2 with either 1,4-
naphthoquinone (3a) or with p-benzoquinone give 1-phenylanthraquinone (4a) and 1,4-
diphenylanthraquinone (4b) (from 1,4-naphthoquinone) and 1,5-diphenylanthraquinone and 1,4,5,8-
tetraphenylanthraquinone (from p-benzoquinone), respectively (Scheme 1). The Diels-Alder approach
has also been used for the synthesis of arenoanthraquinones such as of benz[a]anthracene-7,12-diones
[9]. For the preparation of 1,4-diarylanthraquinones, Gautrot et al. [2] started from 1,4-dihydroxy-9,10-
anthraquinone, which was transformed into its bistriflate 5 [3] and subsequently subjected to coupling
reaction with arylboronic acids (Scheme 2) [2].
Scheme 1. Aryl substituted anthraquinones by [4+2]-cycloaddition reaction [7,8].

Molecules 2009, 14
1015
Coupling reactions have also been carried out with 1-diazoanthraquinone, which was prepared from
the corresponding 1-aminoanthraquinone [10]. In order to have a versatile strategy to prepare aryl
substituted anthraquinones in hand, we wanted to use haloanthraquinones as key intermediates, which
we could subsequently transform into the target compounds by Suzuki cross coupling reactions. Again,
preparative routes to haloanthraquinones are known. Thus, Battegay and Claudin prepared a number of
dibromoanthraquinones from the corresponding diaminoanthraquinones by Sandmeyer reactions [11]
and sulfonic acid functionalities could also be transformed to bromo substituents at elevated
temperatures [11].
Scheme 2. 1,4-Diphenylanthraquinone by Suzuki-type coupling with aryl triflates [2].
Scheme 3. Bromination of an anthraquinone-disulfonic acid to a dibromoanthraquinone [11].
Based on our good experience in using thiophene S-oxides, either in situ [12-14] or in purified form
[15-17], as dienes in the preparation of multi-functionalised arenes [18,19], we decided to utilize
halogenated thiophene S-oxides as transient intermediates to prepare bromoanthraquinones. While
most thiophenes themselves are unreactive or react sluggishly [20-22] and thiophene S,S-dioxides [23]
often necessitate high temperatures to participate in [4+2]-cycloaddition reactions, thiophene S-oxides
have been found to be reactive dienes in Diels-Alder type reactions. While a number of thiophene S-
oxides [15-17,24-28], especially those with electron donating substituents have been isolated,
thiophene S-oxides can be reacted in situ [12-14]. Thiophene S-oxides undergo cycloaddition
reactions, when thiophenes are oxidized in the presence of a dienophile.

Molecules 2009, 14
Scheme 4. In situ preparation and cycloaddition of a dibrominated thiophene S-oxide [30].
1016
From our understanding, in halogenated thiophenes, the sulfur is more difficult to oxidize with
peracids or with hydrogen peroxide than in the corresponding donor substituted thiophenes. On the
other hand, oxidized halothiophenes – halothiophene S-oxides and halothiophene S,S-dioxides –
should be more reactive dienes than their electron-donor substituted counterparts. Therefore, in all
likelihood, halothiophene S-oxides would have to be used in situ. In fact, Torssell has reported on one
example of a successful oxidative cycloaddition of a monobrominated thiophene with 1,4-
naphthoquinone (3a), where the cycloadduct was produced in poor yield [29]. Our own work [30] on
the oxidative cycloaddition of brominated and chlorinated thiophenes (eg, 8a) to maleimides (eg, to 9)
indicated that halothiophene S-oxides can be produced in situ and can be reacted with electron poor
dienophiles (Scheme 4).
2. Results and Discussion
In the present case, a variety of brominated thiophenes 8 were submitted to oxidative cycloaddition
reactions with 1,4-naphthoquinones 3. Heated solutions of thiophene 8 and 1,4-naphthoquinone (3a)
were treated with meta-chloroperbenzoic acid in small portions over 48 h. Under these conditions,
cycloaddition between intermediately formed thiophene S-oxides and 1,4-naphthoquinone 3 takes
place, where the formulated, primary sulfoxy-bridged cycloadduct 11 loses the SO-bridge with
concomitant aromatization (Scheme 5). The bromoanthraquinones 7 can be obtained, albeit in very
moderate yield (Table 1). A number of more polar side products formed, depending on the substrate.
One important type of side product are hydroxyanthraquinones 12 (Figure 2). That bromothiophene S-
oxides are involved here, has been shown in the reaction under analogous conditions of 2,5-
dibromothiophene (8a), 2,3,4,5-tetrabromothiophene (8e) and 2,5-dichlorothiophene with N-
phenylmaleimide (9), where halogenated 7-thiabicyclo[2.2.1]heptene S-oxides 10 could be isolated
(Scheme 4) [30]. Nevertheless, even in cases where halothiophene S-oxides are oxidized further to
halothiophene S,S-dioxides, cycloaddition reactions may be expected to proceed as electron poor
thiophene S,S-dioxides have been found to undergo cycloaddition reactions readily [31-33], so that
under the present conditions, halothiophene S,S-dioxides can also contribute to the reaction.

Molecules 2009, 14
Scheme 5. Preparation of bromoanthraquinones by oxidative cycloaddition of thiophenes to quinines.
1017
O
R1
O
R1
R2
R2
R2
R2
m-CPBA
Brn
SO
R
+
CHCl3
48h
S
R = Ar, CH3, Br
Brn
O
R1
R
O
R1
3
11
8
3a: R1 = R2 = H
3c: R1 = H, R2 = CH3
3d: R1 = Cl, R2 = H
O
R1
R2
R2
Brn
R
O
R1
7
Table 1. Preparation of bromoanthraquinones by oxidative cycloaddition of thiophenes to quinines.
X
O
Br
O
Br
Br
R
R
Br
Br
Br
Br
R
R
Br
Br
3a/3b/3c
3a
S
S
Br
X
O
Br
O
Br
8a
8e
7a (R = H, X = H) (29%)
7b (R = Me, X = H) (28%)
7c (R = H, X = Cl) (30%)
7g (R = H) (35%)
7h (R = Me) (25%)
O
Br
O
Br
3a
R
R
S
Br
3a/3c
O
S
Br
(25%) 7d
8b
O
7i (R = H) (24%)
7j (R = Me) (23%)
R
8f
Br
O
O
Br
R
S
3a
Br
8c: R = H
8d: R = Me
Br
R = H (7e) (26%), Me (7f) (28%)

Molecules 2009, 14
1018
Figure 2. Hydroxyanthraquinones as side products in the oxidative cycloaddition reactions
of thiophenes to quinines.
The brominated anthraquinones obtained were subjected to Suzuki-Miyaura cross coupling
reactions with a variety of arylboronic acids. Either Pd(PPh3)4/PPh3 or Pd(PPh3)2Cl2/PPh3 was used as
catalyst in a biphasic reaction medium of DME and aq. Na2CO3. The corresponding arylated
anthraquinones were obtained in good yield. In the case of the 1-aryl-2,4-dibromoanthraquinones, the
first aryl group enters selectively into the 4-position, ie., away from the aryl function already present in
the anthraquinone system (Figure 3). Prolonged reaction times and an excess of arylboronic acid make
the 2-position accessible, also. In this manner it is possible to provide anthraquinones with three
different aryl substituents in positions 1, 2 and 4.
Figure 3. Order of entry of further aryl substituents by Suzuki-Miyaura cross-coupling reaction.
Equally interesting is the fact that chlorinated anthraquinones exchange the chloro-substituent
readily, and thus they undergo Suzuki-Miyaura cross coupling reactions with ease, too, even when
using a common catalyst such as Pd(PPh3)4. Thus, 1,4-dibromo-5,8-dichloroanthraquinone (7c) can be
converted to the 1,4,5,8-tetra-arylanthraquinone 4t (see continued Table 2), using Pd(PPh3)4 as a
catalyst, as can be 1-bromo-5,8-dichloro-4-hydroxyanthraquinone (12b) to 13 (Scheme 7).

Molecules 2009, 14
Scheme 6. Arylated anthraquinones by Suzuki-Miyaura coupling of dibromoanthraquinones.
1019
Table 2. Arylated anthraquinones by Suzuki-Miyaura coupling of dibromoanthraquinones.
O
O
Ar
O
O
Br
O
Br
O
Ar
O
Br
O
Ar
7a
4b (Ar = Ph) (89%)
7i
4L (Ar = Ph-p-OMe) (72%)
4c (Ar = Ph-p-Me) (85%)
4d (Ar = Ph-o-Me) (83%)
4e (Ar = Ph-p-OMe) (93%)
4f (Ar = Ph-p-OEt) (91%)
O
Ar
O
Ar
O
Ar
O
Br
Br
O
Ar1
O
Br
4m (Ar = Ph, Ar1= Ph-p-OMe)
7d (Ar = Ph)
O
Ar
O
(75%)
7b
4g (Ar = Ph) (88%)
4h (Ar = Ph-OHept) (83%)
4i (Ar = Ph-ONonyl) (81%)
O
Ar
O
Ar
Br
O
O
Br
Br
O
O
Ar1
O
Ar
O
Br
4n (Ar=Ph-p-Me, Ar1=Ph-p-OMe, 68%)
4o (Ar=Ph, Ar1=Ph-p-OPr, 68%)
7e (Ar = Ph)
7f (Ar = Ph-p-Me)
4j (Ar = Ph-p-OMe) (79%)
4k (Ar = Ph-p-OPr) (85%)
7j

Molecules 2009, 14
1020
Scheme 7. Suzuki-Miyaura coupling of chloroanthraquinones.
The anthraquinones obtained show spectral data typical for this species of compounds. Thus, in the
mass spectra, many of the anthraquinones prepared above have [M+-CO] and [M+-2CO] fragmentation
peaks that are typical for anthraquinones [34,35]. In their carbon NMR spectra, the carbonyl functions
resonate at 184 – 185 ppm. In 1,2-aryl-substituted anthraquinones, the influence of the proximity of the
π-system of one aryl group on the protons of the other can be noted by a high-field shift.
The UV-VIS spectra of most of the solutions of the arylated anthraquinones in acetonitrile show at
least three distinct bands, usually associated with π-π* transitions [36,37]. The strongest band,
normally called a ‘benzoid band’ [37], is located at around λ = 250 nm for most of the compounds,
which is in accordance to data gathered from other substituted anthraquinones. It could be shown that
the substitution pattern of the aryl substituent in the anthraquinone has little influence on the
wavelength of this absorption band. Methylation of the C6/C7 positions in the anthraquinone core
leads to a shift of Δλ = 10 nm, where λmax = 263 nm. A longer-wave π-π*-transition (often called a
‘quinoid band’ [37]) can be found as a shoulder at λ = 265 – 270 nm for the 1,4-diarylated
anthraquinones. Again, there is very little influence of the substitution pattern of the aryl groups at C1
and C4 on the wavelength of this band. Also, 1,2,4-triarylated anthraquinones show this band within
the same wavelength region. Where identifiable, this transition is shifted to lower energy for 6,7-
methylated anthraquinones (eg., for 4k, λ = 279 nm). A shift to higher wavelength is also found for the
β-bromo substituted anthraquinone 4n (λ = 275 nm). Two further π-π* transitions can be noted,
although they cannot be identified for all compounds measured. The first is found at around λ = 300
nm. The π-π* transition with the longest wavelength can be noted at λ = 350 – 380 nm for the
compounds measured. Substituent dependence of this transition has been reported for mono-
substituted anthraquinones [36,37], and also in our case a substituent-dependence can be noted.
3. Experimental Section
Warning: Working with meta-chloroperoxybenzoic acid at elevated temperatures is hazardous. The
reactions should be carried out in a well-ventilated hood. Protections against an explosion should be
set up. (The authors themselves have not experienced any difficulties with these reactions. The above
measures may be seen as protective precautions).

Molecules 2009, 14
1021
General
Melting points were measured on a Yanaco microscopic hot stage and are uncorrected. IR spectra
1
were measured with JASCO IR-700 and Nippon Denshi JIR-AQ2OM machines. H- and 13C-NMR
spectra were recorded with a JEOL EX-270 (1H at 270 MHz and 13C at 67.8 MHz) and JEOL Lambda
13
400 spectrometer (1H at 395 MHz and C at 99.45 MHz). The chemical shifts are relative to TMS
(solvent CDCl3, unless otherwise noted). Mass spectra were measured with a JMS-01-SG-2
spectrometer [electron impact mode (EI), 70 eV or fast atom bombardment (FAB)]. Column
chromatography was carried out on Wakogel 300.
The oxidative cycloaddition reactions were carried out with commercially available meta-
chloroperbenzoic acid (m-CPBA, 70-75 w%, Acros), which was used without further purification.
Pd(PPh3)4 (TCI), Pd(PPh3)2Cl2 (TCI), 2,5-dibromothiophene (8a) (Aldrich), 2-methylthiophene (TCI),
2-bromothiophene (Aldrich), thiophene (Wako) and 2,5-dichlorothiophene (Aldrich) were acquired
commercially. 2,3,4,5-Tetrabromothiophene (8e) (thiophene, Br2, CHCl3) [38], 2-bromo-5-methyl-
thiophene (8f) (2-methylthiophene, NBS, CHCl3, AcOH), 2-bromo-5-phenylthiophene (8b) and 2-
bromo-5-(p-tolyl)thiophene (a. 2-bromothiophene, Aryl-B(OH)2, Pd(PPh3)4, DME, aq. Na2CO3; b.
N-bromosuccinimide [NBS], CHCl3, AcOH) [39] were prepared analogous to known procedures. 2,4-
Dibromo-5-arylthiophenes, 8c and 8d, were synthesized by brominating 2-arylthiophenes using an
excess [40] of NBS. 5,8-Dichloro-1,4-naphthoquinone (3c) was prepared by oxidative cycloaddition of
2,5-dichlorothiophene to p-benzoquinone [29]. 2,3-Dimethyl-5,8-naphthoquinone (3b) was prepared
by cycloaddition of 2,3-dimethylbuta-1,3-diene to p-benzoquinone under EuCl3 catalysis (96 h,
ClCH2CH2Cl, rt) [41] with subsequent base catalysed enolisation [42,43] of the 4a,5,8,8a-tetrahydro-
6,7-dimethyl-1,4-naphthoquinone formed and oxidation of the 6,7-dimethyl-5,8-dihydronaphthalene-
1,4-diol (Ag2O, Na2SO4, benzene) [44] to 6,7-dimethyl-5,8-dihydro-1,4-naphthoquinone, which in a
last step was dehydrogenated (DDQ, benzene, reflux). p-Methoxyphenylboronic acid (TCI), o-
methoxyphenylboronic acid (TCI), phenylboronic acid (TCI), and p-tolylboronic acid (Aldrich) were
acquired commercially. p-Ethoxy- and p-propoxyphenylboronic acids were prepared from the
corresponding p-alkoxy-bromobenzenes (a. n-BuLi, B(OEt)3, THF; b. HCl) [45].
1,4-Dibromoanthraquinone (7a) [11,46]. To a stirred solution of dibromothiophene (8a, 1.00 g, 4.16
mmol) and 1,4-naphthoquinone (3a, 517 mg, 3.47 mmol) in CHCl3 (20 mL) at 75 ºC was added m-
CPBA (70w%, 4.76 g) in small portions. After 48 h, the mixture was cooled and poured into an aq. sat.
Na2CO3 solution. After the mixture was stirred for 15 min. at rt, it was extracted with chloroform (3 X
25 mL). The organic phase was dried over anhydrous MgSO4 and concentrated in vacuo. The residue
was subjected to column chromatography on silica gel (hexane/ether/CHCl3 8:1:1) to give 7a (370 mg,
29%); δH (270 MHz, CDCl3) 7.78 – 7.81 (2H, m), 7.81 (2H, s), 8.20 – 8.23 (2H, m); δC (67.8 MHz,
CDCl3) 122.1 (2C, Cquat), 126.9 (2C, CH), 133.5 (2C, Cquat), 133.6 (2C, Cquat), 134.2 (2C, CH), 140.6
(2C, CH), 181.6 (2C, Cquat, CO); MS (EI, 70 eV) m/z (%) 368 ([81Br2]M+) (50), 366 ([81Br79Br]M+)
(100), 364 ([79Br2]M+) (51), 340 ([81Br2]M+-CO) (15), 338 ([81Br79Br]M+-CO) (30), 336 ([79Br2]M+ -
CO) (15), 312 ([81Br2]M+-2CO) (10), 310 ([81Br79Br]M+-2CO) (21), 308 ([79Br2]M+-2CO) (11), 287
79
(11), 285 (11), 231 (15), 229 (15), 150 (73). HRMS Found: 365.8716. Calcd. for C14H6O2 Br81Br:
365.8715.

Molecules 2009, 14
1022
Selected data of other bromoanthraquinones
1,4-Dibromo-6,7-dimethylanthraquinone (7b). Yellow solid; δH (270 MHz, CDCl3) 2.42 (6H, s, 2
CH3), 7.77 (s, 2H), 7.94 (s, 2H); δC (67.8 MHz, CDCl3) 20.3 (2C, CH3), 122.1 (2C, Cquat), 127.8 (2C,
CH), 131.5 (2C, Cquat), 133.7 (2C, Cquat), 140.4 (2C, CH), 144.5 (2C, Cquat), 181.8 (2C, Cquat, CO); MS
(EI, 70 eV) m/z (%) 396 ([81Br2]M+, 50), 394 ([81Br79Br]M+, 100), 392 ([79Br2]M+, 50), 368
([81Br2]M+-CO, 12), 366 ([81Br79Br]M+ - CO, 25), 364 ([79Br2]M+ - CO, 13). HRMS Found: 393.9033.
79
Calcd. for C16H10O2 Br81Br: 393.9028.
1,4-Dibromo-5,8-dichloroanthraquinone (7c). Colorless solid; δH (270 MHz, CDCl3) 7.60 (2H, s),
7.72 (2H, s); MS (EI, 70 eV) m/z 438 (3.3), 436 (9.2), 434 (9.6), 432 (3.9), 149 (34), 58 (100). HRMS
35
Found: 433.7930. Calcd. for C14H4O2 Cl37Cl79Br2: 433.7933.
2,4-Dibromo-1-(4-methylphenyl)anthraquinone (7f). Yellow solid, mp. 183 ºC; δH (270 MHz, CDCl3)
2.47 (3H, s, CH3), 7.01 (2H, d, 3J = 8.1 Hz), 7.31 (2H, d, 3J = 8.1 Hz), 7.50 – 7.80 (2H, m), 7.96 – 8.00
(1H, m), 8.20 – 8.23 (1H, m), 8.38 (1H, s); δC (67.8 MHz, CDCl3) 21.6, 122.1, 126.9, 127.6 (2C),
128.0, 129.0, 129.2 (2C), 131.3, 133.2, 133.4, 133.5, 134.0, 134.1, 137.3, 137.4, 143.6, 143.9, 182.1,
182.2; MS (EI, 70 eV) m/z (%) 456 ([81Br79Br]M+) (18), 299 (100). HRMS Found: 455.9188. Calcd.
81
for C21H12O2 Br79Br: 455.9185.
1,2,3,4-Tetrabromoanthraquinone (7g) [47]. Orange solid; mp. 200 ºC; δH (270 MHz, CDCl3) 7.76 –
7.79 (2H, m), 8.11 – 8.14 (2H, m); δC (67.8 MHz, CDCl3) 125.0 (2C, Cquat), 126.8 (2C, CH), 133.6
(2C, Cquat), 134.3 (2C, CH), 139.0 (2C, Cquat), 181.8 (2C, Cquat, CO); MS (FAB, 3-nitrobenzyl alcohol)
79
79
79
m/z (%) 527 ([81Br3 Br]MH+) (0.2), 526 ([81Br3 Br]M+) (0.1), 525 ([81Br2 Br2]MH+) (0.3), 524
([81Br2 Br2]M+) (0.2), 523 ([81Br79Br3]MH+) (0.2). HRMS Found: 524.6993. Calcd. for
C14H5O2 Br2 Br2: 524.6983 (MH+, FAB).
79
79
81
1,2,3,4-Tetrabromo-6,7-dimethylanthraquinone (7h). Slowly solidifying yellow oil; δH (270 MHz,
CDCl3) 2.42 (6H, s, 2 CH3), 7.86 (2H, s); δC (67.8 MHz, CDCl3) 20.3 (2C, CH3), 127.7 (2C), 131.5
(2C), 134.5 (2C), 135.4 (2C), 138.7 (2C), 144.5 (2C), 181.8 (2C, CO); MS (FAB, 3-nitrobenzyl
79
alcohol) m/z (%) 552 ([81Br2 Br2]M+) (0.2)
1-Bromo-4-methylanthraquinone (7i) [48]. Beige colored solid; δH (270 MHz, CDCl3) 2.79 (3H, s,
CH3), 7.36 (1H, d, 3J = 8.4 Hz), 7.74 – 7.78 (2H, m), 7.87 (1H, d, 3J = 8.4 Hz), 8.15 – 8.24 (2H, m); δC
(67.8 MHz, CDCl3) 23.6 (CH3), 120.2 (Cquat), 126.6 (CH), 126.9 (CH), 127.8 (Cquat), 132.9 (Cquat),
133.8 (2C, CH), 134.4 (Cquat), 137.9 (CH), 140.2 (CH), 140.4 (Cquat), 141.9 (Cquat), 182.9 (Cquat, CO),
184.5 (Cquat, CO); MS (EI, 70 eV) m/z (%) 302 ([81Br]M+, 97), 300 ([79Br]M+, 100), 274 ([81Br]M+-
81
CO, 15), 272 ([79Br]M+-CO, 15), 193 (59), 165 (90). HRMS Found: 301.9764. Calcd. for C15H9O2 Br:
79
301.9767. Found: 299.9789. Calcd. for C15H9O2 Br: 299.9786.
1-Bromo-4,6,7-trimethylanthraquinone (7j). Yellow solid, mp. 194 ºC; δH (270 MHz, CDCl3) 2.42
3
(6H, s, 2 CH3), 2.73 (3H, s, CH3), 7.33 (1H, d, 3J = 8.4 Hz), 7.82 (1H, d, J = 8.4 Hz), 7.91 (1H, s),

Molecules 2009, 14
1023
7.95 (1H, s); δC (67.8 MHz, CDCl3) 20.2 (2C, CH3), 20.7 (CH3), 120.0 (Cquat), 127.4 (CH), 127.8
(CH), 131.7 (Cquat), 131.8 (Cquat), 132.6 (Cquat), 134.1 (Cquat), 137.7 (CH), 140.0 (CH), 141.8 (Cquat),
143.8 (Cquat, 2C), 183.2 (Cquat, CO), 184.8 (Cquat, CO); MS (EI, 70 eV) m/z (%) 330 ([81Br]M+) (100),
328 ([79Br]M+) (100), 315 ([81Br]M+-CH3) (38), 313 ([79Br]M+-CH3) (39), 302 ([81Br]M+-CO) (26),
300 ([81Br]M+-CO) (28), 287 ([81Br]M+-CH3-CO) (26), 285 ([79Br]M+-CO-CH3) (26), 221 (55), 178
79
(83). HRMS Found: 328.0097. Calcd. for C17H13O2 Br: 328.0099.
1,4-Bis(4-methylphenyl)anthraquinone (4c) [49]. Under an inert atmosphere, a solution of 7a (324 mg,
0.89 mmol), 4-methylphenylboronic acid (385 mg, 2.83 mmol), Pd(PPh3)2Cl2 (30 mg, 4.0.10-5 mol)
and triphenylphosphine (30 mg, 0.11 mmol) in a solvent mixture of DME (10 mL) and aq. Na2CO3
(2.32 g Na2CO3 in 15 mL H2O, 6 mL) was kept at 65 ºC for 18h. Thereafter the cooled solution was
poured into water (25 mL) and extracted with chloroform (3 x 15 mL). The combined organic phase
was dried over anhydrous MgSO4 and was concentrated in vacuo. Column chromatography of the
residue on silica gel (hexane/CHCl3/ether 3:1:1) gave 4c (293 mg, 85%) as an orange solid; mp. 265
3
3
ºC; δH (270 MHz, CDCl3) 2.45 (6H, s, 2 CH3), 7.18 (4H, d, J = 7.6 Hz), 7.27 (4H, d, J = 7.6 Hz),
7.53 (2H, s), 7.65 – 7.70 (2H, m), 8.05 - 8.09 (2H, m); δC (67.8 MHz, CDCl3) 21.3 (2C, CH3), 126.7
(2C, CH), 127.9 (4C, CH), 128.9 (4C, CH), 132.8 (2C, Cquat), 133.7 (2C, CH), 134.1 (2C, Cquat), 136.5
(2C, CH), 136.8 (2C, Cquat), 139.4 (2C, Cquat), 143.9 (2C, Cquat), 184.2 (2C, CO); MS (EI, 70 eV) m/z
(%) = 388 (M+) (83), 373 (M+-CH3) (100), 179 (40). HRMS Found: 388.1469. Calcd. for C28H20O2:
.
388.1463. Found: C, 84.36; H, 5.12%. Calcd. for C28H20O2 H2O: C, 84.61; H, 5.33%. UV-Vis
spectrum (CH3CN, nm) λmax 253 (44700), 268 (sh, 21310), 298 (9350), 358 (2470).
Selected data for other arylated anthraquinones
1,4-Diphenylanthraquinone (4b) [2,50] Yellow solid; δH (270 MHz, CDCl3) 7.29 – 7.35 (4H, m), 7.43
– 7.48 (6H, m), 7.56 (2H, s), 7.66 – 7.71 (2H, m), 8.05 – 8.08 (2H, m); δC (67.8 MHz, CDCl3) 126.8
(2C, CH), 127.2 (2C, CH), 127.9 (4C, CH), 128.2 (4C, CH), 132.7 (2C, Cquat), 133.7 (2C, CH), 134.0
(2C, Cquat), 136.4 (2C, CH), 142.3 (2C, Cquat), 144.1 (2C, Cquat), 184.0 (2C, Cquat, CO); MS (FAB, 3-
nitrobenzyl alcohol) m/z (%) 361 (MH+) (5.6). HRMS Found: 361.1232. Calcd. for C26H17O2:
361.1229 (MH+, FAB); UV-Vis spectrum (CH3CN, nm) λmax 253 (36370), 269 (sh, 19190), 288 (sh,
7320).
1,4-Bis(4-methoxyphenyl)anthraquinone (4e). Orange needles; mp. 231 ºC; δH (270 MHz, CDCl3) 3.89
(6H, s, 2 OCH3), 7.00 (4H, d, 3J = 8.6 Hz), 7.26 (4H, d, 3J = 8.6 Hz), 7.53 (2H, s), 7.68 – 7.72 (2H, m),
8.06 – 8.09 (2H, m); δC (67.8 MHz, CDCl3) 55.2 (2C, OCH3), 113.7 (4C, CH), 126.7 (2C, CH), 129.3
(4C, CH), 133.7 (2C, CH), 132.9 (2C, Cquat), 134.1 (2C, Cquat), 134.5 (2C, Cquat), 136.6 (2C, CH), 143.6
(2C, Cquat), 158.9 (2C, Cquat), 184.3 (2C, Cquat, CO); MS (EI, 70 eV) m/z (%) 420 (M+) (100), 389 (32),
333 (18), 313 (13), 276 (17). HRMS Found: 420.1367. Calcd. for C28H20O4: 420.1362; UV-Vis
spectrum (CH3CN, nm) λmax 253 (59610), 271 (sh, 23890), 313 (13280).
1,4-Bis(4-ethoxyphenyl)anthraquinone (4f). Orange needles; mp. 239 ºC; δH (270 MHz, CDCl3) 1.47
(3H, t, CH3, 3J = 7.0 Hz), 4.12 (2H, q, OCH2, 3J = 7.0 Hz), 6.98 (4H, d, 3J = 8.4 Hz), 7.24 (4H, d, 3J =

Molecules 2009, 14
1024
8.4 Hz), 7.53 (2H, s), 7.67 – 7.70 (2H, m), 8.05 – 8.09 (2H, m); δC (67.8 MHz, CDCl3) 14.9 (2C, CH3),
63.4 (2C, OCH2), 114.2 (4C, CH), 126.7 (2C, CH), 129.3 (4C, CH), 132.9 (2C, Cquat), 133.6 (2C, CH),
134.2 (2C, Cquat), 134.3 (2C, Cquat), 136.6 (2C, CH), 143.6 (2C, Cquat), 158.3 (2C, Cquat), 184.3 (2C,
C
quat, CO); MS (FAB, 3-nitrobenzyl alcohol) m/z (%) 449 (MH+) (7.5). HRMS Found: 449.1749.
.
Calcd. for C30H25O4: 449.1753. Found: C, 79.57; H, 5.47%. Calcd. for C30H24O4 0.2H2O: C, 79.70; H,
5.44%; UV-Vis spectrum (CH3CN, nm) λmax 253 (49430), 269 (sh, 21220), 314 (10910).
1,4-Diphenyl-6,7-dimethylanthraquinone (4g). Yellow needles, mp. 232 ºC; δH (270 MHz, CDCl3)
2.34 (6H, s, 2 CH3), 7.30 – 7.34 (4H, m), 7.43 – 7.50 (6H, m), 7.53 (2H, s), 7.82 (2H, s); δC (67.8
MHz, CDCl3) 20.1 (2C, CH3), 127.0 (2C, CH), 127.7 (2C, CH), 127.9 (4C, CH), 128.1 (4C, CH),
132.0 (2C, Cquat), 132.9 (2C, Cquat), 136.1 (2C, CH), 142.5 (2C, Cquat), 143.7 (2C, Cquat), 143.9 (2C,
Cquat), 184.1 (2C, Cquat, CO); MS (FAB, 3-nitrobenzyl alcohol) m/z (%) 389 (MH+) (5.3). HRMS
Found: 389.1539. Calcd. for C28H21O2: 389.1542 (FAB). Found: C, 85.80; H, 5.18%. Calcd. for
.
C28H20O2 0.2H2O: C, 85.78; H, 5.24%; UV-Vis spectrum (CH3CN, nm) λmax 263 (41490), 338 (4480).
1,4-Bis(4-heptoxyphenyl)-6,7-dimethylanthraquinone (4h). Beige solid; mp. 181 ºC; δH (270 MHz,
3
CDCl3) 0.92 (6H, t, J = 6.2 Hz, 2 CH3), 1.34 – 1.60 (16H, m), 1.78 – 1.86 (4H, m), 2.35 (6H, s, 2
CH3), 4.03 (4H, t, 3J = 6.5 Hz), 6.98 (4H, d, 3J = 8.6 Hz), 7.23 (4H, d, 3J = 8.6 Hz), 7.50 (2H, s), 7.83
(2H, s); δC (67.8 MHz, CDCl3) 14.1 (2C, CH3), 20.2 (2C, CH2), 22.7 (2C, CH2), 26.1 (2C, CH2), 29.1
(2C, CH2), 29.4 (2C, CH2), 31.8 (2C, CH2), 67.9 (2C, OCH2), 114.1 (4C, CH), 127.7 (2C, CH), 129.2
(4C, CH), 132.1 (2C, Cquat), 133.0 (2C, Cquat), 134.4 (2C, Cquat), 136.4 (2C, Cquat), 143.5 (2C, Cquat),
158.4 (2C, Cquat), 184.5 (2C, Cquat, CO); MS (FAB, 3-nitrobenzyl alcohol) m/z (%) 617 (MH+) (0.5).
HRMS Found: 617.3629. Calcd. for C42H49O4: 617.3631 (MH+, FAB)
1,4-Bis(4-nonyloxyphenyl)-6,7-dimethylanthraquinone (4i). Yellow-orange solid; mp. 176 ºC; δH (270
3
MHz, CDCl3) 0.88 (6H, t, J = 4.3 Hz, 2 CH3), 1.30 (20H, m), 1.44 – 1.49 (4H, m), 1.78 – 1.85 (4H,
m), 2.35 (6H, s, 2 CH3), 4.03 (4H, t, 3J = 6.5 Hz), 6.98 (4H, d, 3J = 8.6 Hz), 7.23 (4H, d, 3J = 8.6 Hz),
7.50 (2H, s), 7.83 (2H, s); δC (67.8 MHz, CDCl3) 14.1 (2C, CH3), 20.2 (2C, CH2), 22.7 (2C, CH2), 26.1
(2C, CH2), 29.3 (2C, CH2), 29.4 (2C, CH2), 29.5 (2C, CH2), 29.6 (2C, CH2), 31.9 (2C, CH2), 67.9 (2C,
OCH2), 114.1 (4C, CH), 127.6 (2C, CH), 129.2 (4C, CH), 132.1 (2C, Cquat), 133.0 (2C, Cquat), 134.4
(2C, Cquat), 136.4 (2C, Cquat), 143.5 (2C, Cquat), 158.4 (2C, Cquat), 184.5 (2C, Cquat, CO); MS (FAB, 3-
nitrobenzyl alcohol) m/z (%) 673 (MH+) (100). HRMS Found: 673.4254. Calcd. for C46H57O4:
673.4257 (MH+, FAB).
1-(4-Methoxyphenyl)-4,6,7-trimethylanthraquinone (4j). Solid; δH (270 MHz, CDCl3) 2.30 (3H, s,
CH3), 2.40 (3H, s, CH3), 2.86 (3H, s, CH3), 3.87 (3H, s, OCH3), 6.96 (2H, d, 3J = 8.6 Hz), 7.19 (2H, d,
3
3
3J = 8.6 Hz), 7.40 (1H, d, J = 7.8 Hz), 7.50 (1H, d, J = 7.8 Hz), 7.80 (1H, s), 7.94 (1H, s); δC (67.8
MHz, CDCl3) 20.1 (CH3), 20.2 (CH3), 23.8 (CH3), 55.2 (OCH3), 113.5 (2C, CH), 127.4 (CH), 127.5
(CH), 129.1 (2C, CH), 132.1 (Cquat), 132.2 (Cquat), 132.9 (Cquat), 133.0 (Cquat), 135.1 (Cquat), 136.7
(CH), 136.8 (CH), 141.1 (Cquat), 142.5 (Cquat), 143.3 (Cquat), 143.4 (Cquat), 158.6 (Cquat), 184.7 (Cquat
,
CO), 185.9 (Cquat, CO); MS (EI, 70 eV) m/z (%) 356 (M+) (84), 355 (100), 325 (32), 312 (14). HRMS

Molecules 2009, 14
1025
Found: 356.1413. Calcd. for C24H20O3: 356.1412; UV-Vis spectrum (CH3CN, nm) λmax 263 (49630),
278 (sh, 19470), 339 (4880).
1-(4-Propoxyphenyl)-4,6,7-trimethylanthraquinone (4k). Yellow solid; mp. 215 ºC; δH (270 MHz,
CDCl3) 1.07 (3H, t, 3J = 7.6 Hz, CH3), 1.56 (3H, s, CH3), 1.85 (2H, dt, 3J = 7.6 Hz, 3J = 6.5 Hz), 2.35
(3H, s, CH3), 2.41 (3H, s, CH3), 3.99 (2H, t, 3J = 6.5 Hz, OCH2), 6.95 (2H, d, 3J = 8.6 Hz), 7.17 (2H, d,
3
3
3J = 8.6 Hz), 7.41 (1H, d, J = 7.8 Hz), 7.50 (1H, d, J = 7.8 Hz), 7.81 (1H, s), 7.94 (1H, s); δC (67.8
MHz, CDCl3) 10.6 (CH3), 20.1 (CH3), 20.2 (CH3), 22.7 (CH2), 23.8 (CH3), 69.4 (OCH2), 114.1 (2C,
CH), 127.5 (CH), 127.6 (CH), 129.1 (2C, CH), 132.1 (Cquat), 132.2 (Cquat), 132.8 (Cquat), 133.0 (Cquat),
134.8 (Cquat), 136.7 (CH), 136.8 (CH), 141.1 (Cquat), 142.6 (Cquat), 143.3 (Cquat), 143.4 (Cquat), 158.2
(Cquat), 184.7 (Cquat, CO), 185.9 (Cquat, CO); MS (EI, 70 eV) m/z (%) 384 (M+) (68), 341 (M+-
(CH2)2CH3) (100). HRMs Found: 384.1718. Calcd. for C26H24O3: 384.1725 UV-Vis spectrum
(CH3CN, nm) λmax 263 (57850), 279 (sh, 20490), 330 (5580, ill-defined).
1-(4-Methoxyphenyl)-4-methylanthraquinone (4l) [50]. Yellow-orange needles; mp. 221 ºC; δH (270
3
3
MHz, CDCl3) 2.88 (3H, s, CH3), 3.88 (3H, s, OCH3), 6.97 (2H, d, J = 8.6 Hz), 7.20 (2H, d, J = 8.6
Hz), 7.44 (1H, d, 3J = 8.1 Hz), 7.53 (1H, d, 3J = 8.1 Hz), 7.67 – 7.75 (2H, m), 8.04 – 8.07 (1H, m), 8.19
– 8.23 (1H, m); δC (67.8 MHz, CDCl3) 23.8 (CH3), 55.2 (OCH3), 113.6 (2C, CH), 126.6 (CH), 129.2
(2C, CH), 132.8 (Cquat), 132.9 (Cquat), 133.5 (CH), 133.6 (CH), 134.1 (Cquat), 134.2 (Cquat), 134.8
(Cquat), 137.0 (CH, 3C), 141.3 (Cquat), 142.6 (Cquat), 158.7 (Cquat), 184.6 (Cquat, CO), 184.7 (Cquat, CO);
MS (FAB, 3-nitrobenzyl alcohol) m/z (%) 329 (MH+) (14). HRMS Found: 329.1183. Calcd. for
.
C22H17O3: 329.1178 (MH+, FAB). Found: C, 79.89; H, 4.73%. Calcd. for C22H16O3 0.1H2O: C, 80.03;
H, 4.91%; UV-Vis spectrum (CH3CN, nm) λmax 253 (38343), 269 (sh, 15440), 302 (5400), 354 (2505).
1-(4-Methoxyphenyl)-4-phenylanthraquinone (4m). Beige solid; MS (FAB, 3-nitrobenzyl alcohol) m/z
(%) 391 (MH+) (7.6). HRMS Found: 391.1340. Calcd. for C27H19O3: 391.1334 (MH+, FAB); UV-Vis
spectrum (CH3CN, nm) λmax 253 (38520), 271 (sh, 18390), 306 (7980).
2-Bromo-1-(4-methylphenyl)-4-(4-methoxyphenyl)anthraquinone (4n). Orange needles; mp. 208 ºC; δH
(270 MHz, CDCl3) 2.49 (3H, s, CH3), 3.89 (3H, s, OCH3), 7.01 (2H, d, 3J = 8.9 Hz), 7.08 (2H, d, 3J =
8.1 Hz), 7.27 (2H, d, 3J = 8.9 Hz), 7.33 (2H, d, 3J = 8.1 Hz), 7.66 – 7.70 (2H, m), 7.92 (1H, s), 8.00 –
8.07 (2H, m); MS (FAB, 3-nitrobenzyl alcohol) m/z (%) 485 ([81BrM]H+) (7.2), 484 (81BrM+) (8.0),
79
483 ([79BrM]H+, 8.9), 482 (79BrM+) (6.0). HRMS Found: 483.0595. Calcd. for C28H20O3 Br (MH+,
FAB); UV-Vis spectrum (CH3CN, nm) λmax 258 (37150), 275 (sh, 16870), 309 (8100).
2-Bromo-1-phenyl-4-(4-propoxyphenyl)anthraquinone (4o). Yellow solid; mp. 183 ºC; δH (270 MHz,
CDCl3) 1.08 (3H, t, 3J = 7.3 Hz, CH3), 1.86 (2H, dt, 3J = 7.3 Hz, 3J = 6.5 Hz), 4.01 (2H, t, 3J = 6.5 Hz,
OCH2), 7.00 (2H, d, 3J = 8.4 Hz), 7.17 – 7.21 (2H, m), 7.25 (2H, d, 3J = 8.4 Hz), 7.48 – 7.54 (3H, m),
7.66 – 7.70 (2H, m), 7.93 (1H, s), 7.98 – 8.02 (1H, m), 8.04 – 8.07 (1H, m); δC (67.8 MHz, CDCl3)
10.6 (CH3), 22.7 (CH2), 69.5 (OCH2), 114.3 (2C, CH), 126.7 (CH), 126.9 (CH), 127.4 (CH), 127.9
(2C, CH), 128.3 (2C, CH), 129.2 (2C, CH), 131.7 (Cquat), 132.3 (Cquat), 132.9 (Cquat), 133.6 (Cquat),
133.8 (CH), 133.9 (CH), 134.3 (Cquat), 141.0 (CH), 141.2 (Cquat), 142.9 (Cquat), 145.1 (Cquat), 155.8
(Cquat), 183.1 (Cquat, CO), 183.7 (Cquat, CO); MS (EI, 70 eV) m/z (%) 498 ([81Br]M+) (100), 496

Molecules 2009, 14
1026
([79Br]M+) (98), 455 ([81Br]M+-(CH2)2CH3) (84), 453 ([79Br]M+-(CH2)2CH3) (81). HRMS Found:
79
496.0677. Calcd. for C29H21O3 Br: 496.0674.
1-(4-Methylphenyl)-2,4-bis(4-ethoxyphenyl)anthraquinone (4q). Yellow needles, mp. 230 ºC; δH (270
3
3
MHz, CDCl3) 1.37 (3H, t, J = 7.0 Hz, CH3), 1.46 (3H, t, J = 7.0 Hz, CH3), 2.36 (3H, s, CH3), 3.97
3
3
3
(2H, d, J = 7.0 Hz, OCH2), 4.11 (2H, d, J = 7.0 Hz, OCH2), 6.67 (2H, d, J = 8.9 Hz), 6.91 – 6.99
(6H, m), 7.08 (2H, d, 3J = 7.8 Hz), 7.29 (2H, d, 3J = 8.9 Hz), 7.57 (1H, s), 8.00 – 8.04 (2H, m), 8.06 –
8.09 (2H, m); δC (67.8 MHz, CDCl3) 14.7 (CH3), 14.9 (CH3), 21.4 (CH3), 63.3 (OCH2), 63.4 (OCH2),
113.7 (2C, CH), 114.1 (2C, CH), 126.5 (CH), 126.7 (CH), 128.6 (2C, CH), 129.2 (2C, CH), 129.4 (2C,
CH), 130.7 (2C, CH), 131.3 (Cquat), 132.0 (Cquat), 133.4 (CH), 133.5 (CH), 134.1 (Cquat), 134.2 (Cquat),
134.3 (Cquat), 134.5 (Cquat), 135.9 (Cquat), 137.0 (Cquat), 138.9 (CH), 141.6 (Cquat), 143.4 (Cquat), 147.4
(Cquat), 158.0 (Cquat), 158.3 (Cquat), 184.1 (Cquat, CO), 184.9 (Cquat, CO); MS (FAB, 3-nitrobenzyl
alcohol) m/z (%) 539 (MH+) (31). HRMS Found: 539.2219. Calcd. for C37H31O4: 539.2222. Found: C,
82.26; H, 5.62%. Calcd. for C37H30O4: C, 82.50; H, 5.61%; UV-Vis spectrum (CH3CN, nm) λmax 250
(57030), 268 (sh, 31850), 298 (sh, 19440), 359 (6340).
1-(4-Methylphenyl)-2,4-bis(4-methoxyphenyl)anthraquinone (4r). Orange solid; mp. 230 ºC; δH (270
3
MHz, CDCl3) 2.36 (3H, s, CH3), 3.75 (3H, s, OCH3), 3.88 (3H, s, OCH3), 6.69 (2H, d, J = 8.6 Hz),
6.93 – 6.96 (4H, m), 6.99 (2H, d, 3J = 8.6 Hz), 7.08 (2H, d, 3J = 8.6 Hz), 7.31 (2H, d, 3J = 8.6 Hz), 7.57
(1H, s), 7.65 – 7.69 (2H, m), 8.00 – 8.11 (2H, m); δC (67.8 MHz, CDCl3) 21.4 (CH3), 55.1 (OCH3),
55.2 (OCH3), 113.1 (2C, CH), 113.6 (2C, CH), 126.5 (CH), 126.7 (CH), 128.6 (2C, CH), 129.2 (2C,
CH), 129.4 (2C, CH), 130.7 (2C, CH), 131.4 (Cquat), 132.2 (Cquat), 133.5 (CH), 133.6 (CH), 134.1
(Cquat), 134.3 (Cquat), 134.5 (Cquat), 134.6 (Cquat), 135.9 (Cquat), 137.0 (Cquat), 138.9 (CH), 141.6 (Cquat),
143.4 (Cquat), 147.4(Cquat), 158.6 (Cquat), 158.9 (Cquat), 184.1 (Cquat, CO), 184.9 (Cquat, CO). MS (FAB,
3-nitrobenzyl alcohol) m/z (%) 511 (MH+) (13). HRMS Found: 511.1905. Calcd. for C35H27O4:
511.1909 (MH+, FAB); UV-Vis spectrum (CH3CN, nm) λmax 250 (50 085), 269 (sh, 26790), 300 (sh,
15980), 365 (4960).
2-(4-Methoxyphenyl)-1-phenyl-4-(4-propoxyphenyl)anthraquinone (4s). Light yellow needles; mp. 233
3
ºC; δH (270 MHz, CDCl3) 1.08 (3H, t, 3J = 7.6 Hz, CH3), 1.86 (2H, tt, J = 7.6 Hz, 3J = 6.2 Hz), 3.74
3
3
3
(3H, s, OCH3), 4.00 (t, 2H, J = 6.2 Hz, OCH2), 6.68 (2H, d, J = 8.6 Hz), 6.94 (2H, d, J = 8.6 Hz),
6.99 (2H, d, 3J = 8.6 Hz), 7.27 – 7.30 (3H, m), 7.04 – 7.08 (2H, m), 7.30 (2H, d, 3J = 8.6 Hz), 7.59 (1H,
s), 7.65 – 7.71 (2H, m), 8.00 – 8.03 (1H, m), 8.07 – 8.10 (1H, m); δC (67.8 MHz, CDCl3) 10.6 (CH3),
22.7 (CH2), 55.1 (OCH3), 69.4 (OCH2), 113.2 (CH, 2C), 114.2 (CH, 2C), 126.5 (CH), 126.6 (CH),
126.7 (CH), 127.7 (CH, 2C), 129.4 (CH, 4C), 130.7 (CH, 2C), 131.4 (Cquat), 132.6 (Cquat), 133.5 (CH),
133.6 (CH), 134.1 (Cquat), 134.2 (Cquat), 134.4 (Cquat), 138.9 (Cquat), 140.2 (Cquat), 141.5 (Cquat), 143.7
(Cquat), 147.3 (Cquat), 158.6 (Cquat), 158.7 (Cquat), 184.1 (Cquat, CO), 184.8 (Cquat, CO). MS (FAB, 3-
nitrobenzyl alcohol) m/z (%) 525 (MH+) (9), 524 (M+) (11). HRMS Found: 524.1990. Calcd. For
C36H28O4: 524.1988. UV-Vis spectrum (CH3CN, nm) λmax 249 (22370), 268 (sh, 12560), 298 (sh,
7490), 382 (2320).

Molecules 2009, 14
1,4,5,8-Tetrakis(4-methoxyphenyl)anthraquinone (4t). Pale orange solid; mp. 251 ˚C; δH (270 MHz,
1027
3
3
CDCl3) 3.84 (12H, s, 4 OCH3), 6.85 (8H, d, J = 8.4 Hz), 7.21 (8H, d, J = 8.4 Hz), 7.48 (4H, s); δC
(67.8 MHz, CDCl3) 55.2 (4C, OCH3), 113.4 (8C, CH), 130.3 (8C, CH), 131.9 (4C, Cquat), 134.5 (4C,
CH), 135.5 (4C, Cquat), 140.3 (4C, Cquat), 159.0 (4C, Cquat), 188.4 (2C, Cquat, CO); MS (FAB, 3-
nitrobenzyl alcohol) m/z (%) 633 (MH+) (1.0). HRMS Found: 633.2286. Calcd. for C42H33O6:
633.2277 (MH+, FAB).
1,2,3,4-Tetrakis(4-heptoxyphenyl)anthraquinone (4u). Slowly crystallizing orange oil; δH (270 MHz,
CDCl3) 0.88 (12H, t, 3J = 7.0 Hz, 4 CH3), 1.28 – 1.31 (32H, m), 1.66 (4H, m), 1.72 (4H, m), 2.32 (6H,
s, 2 CH3), 3.74 (4H, t, 3J = 6.5 Hz), 3.90 (4H, t, 3J = 6.5 Hz), 6.39 (4H, d, 3J = 8.6 Hz), 6.52 (4H, d, 3J
3
3
= 8.6 Hz), 6.70 (4H, d, J = 8.6 Hz), 6.86 (4H, d, J = 8.6 Hz), 7.78 (2H, s); δC (67.8 MHz, CDCl3)
14.0 (2C, CH3), 14.1 (2C, CH3), 20.1 (2C), 22.5 (2C), 22.6 (2C), 25.9 (2C), 26.1 (2C), 29.0 (2C), 29.1
(2C), 29.2 (2C), 29.4 (2C), 31.7 (2C), 31.8 (2C), 67.7 (4C, OCH2), 112.9 (4C), 113.5 (4C), 128.5 (2C),
130.2 (4C), 131.2 (2C), 131.6 (4C), 132.4 (2C), 132.8 (2C), 133.2 (2C), 142.6 (2C), 143.2 (2C), 148.3
(2C), 157.2 (2C), 156.7 (2C), 184.8 (2C, CO); MS (FAB, 3-nitrobenzyl alcohol) m/z (%) 997 (MH+)
(100). HRMS Found: 997.6355. Calcd. for C68H85O5: 997.6346.
1-Hydroxy-4,5,8-tris(4-methoxyphenyl)anthraquinone (13). Reddish solid; mp. 238 ˚C; δH (270 MHz,
3
CDCl3) 3.82 (3H, s, OCH3), 3.83 (3H, s, OCH3), 3.90 (3H, s, OCH3), 6.84 (2H, d, J = 8.6 Hz), 6.87
3
3
3
(2H, d, J = 8.6 Hz), 7.00 (2H, d, J = 8.6 Hz), 7.14 – 7.29 (7H, m), 7.46 (1H, d, J = 7.8 Hz), 7.47
3
3
(1H, d, J = 8.4 Hz), 7.56 (1H, d, J = 7.8 Hz), 12.21 (s, 1H, OH); δC (67.8 MHz, CDCl3) 55.2 (2C,
OCH3), 55.3 (OCH3), 113.6 (6C, CH), 117.1 (Cquat), 122.1 (CH), 129.4 (2C, CH), 129.9 (2C, CH),
130.2 (2C, CH), 131.0 (Cquat), 132.2 (Cquat), 132.5 (Cquat), 134.0 (Cquat), 134.1 (Cquat), 134.2 (Cquat),
136.0 (CH), 136.4 (CH), 136.8 (Cquat), 139.5 (CH), 142.0 (Cquat), 142.9 (Cquat), 158.8 (Cquat), 159.0 (2C,
Cquat), 161.0 (Cquat), 188.0 (Cquat, CO), 189.5 (Cquat, CO); MS (FAB, 3-nitrobenzyl alcohol) m/z (%)
543 (MH+) (1.4). HRMS Found: 543.1805. Calcd. for C35H27O6: 543.1808 (MH+, FAB).
4. Conclusions
Bromoanthraquinones can be synthesized by an oxidative cycloaddition to suitably substituted
naphthoquinones. Bromoanthraquinones can be reacted further to arylated anthraquinones via Suzuki-
Miyaura coupling. Initial results show that also chloro substituted anthraquinones undergo Suzuki
reactions in presence of the commercially available Pd(PPh3)4. The UV-VIS spectra of most of the
solutions of the arylated anthraquinones in acetonitrile show at least three distinct bands associated
with π-π* transitions. Substituent dependence of the longest wavelength transition of the three bands
can be noted.
Acknowledgements
This work has been supported in part by the Global Centre of Excellence of Kyushu University on
New Carbon Resources.

Molecules 2009, 14
1028
References and Notes
1. Josien, J.M.; Fuson, N. The infrared study of the valence bond C=O in polycyclic compounds.
Bull. Soc. Chim. Fr. 1952, 389-397.
2. Gautrot, J.E.; Hodge, P.; Cupertino, D.; Helliwell, M. Experimental evidence for carbonyl-π
electron cloud interactions. New J. Chem. 2006, 30, 1801-1807.
3. Showalter, H.D.H.; Berman, E.M.; Johnson, J.L.; Hunter, W.E. A facile synthesis of
functionalized 9,10-anthracenediones via tosylate and triflate phenolic activation. Tetrahedron
Lett. 1985, 26, 157-160.
4. Shcheglova, N.A.; Shigorin, D.N.; Dokunikhin, N.S. Characteristics of luminescence and
absorption spectra of 1- and 2-alkyl- and arylanthraquinones in solutions. II. Luminescence
spectra at 77 K. Zh. Fiz. Khim. 1966, 40, 1048-1055; [Chem. Abstr. 1966, 65, 9958b].
5. Shcheglova, N.A.; Shigorin, D.N.; Dokunikhin, N.S. Spectra of luminescence and absorption of α
- and β -alkyl and aryl derivatives of anthraquinone in solutions. I. Absorption spectra of α - and β
-alkyl and aryl derivatives of anthraquinone. Zh. Fiz. Khim. 1965, 39, 3039-3043; [Chem. Abstr.
1965, 64, 12058f].
6. Orser, D.A. (General Electric Company, Schenectady, N.Y., USA) Light-modulating medium for
image projection apparatus. US Pat. 3764549, Oct. 9, 1973; [Chem. Abstr. 1973, 79, 141431j].
7. Weizmann, C.; Bergmann, E.; Haskelberg, L. Phenylated phthalic acids and anthracene
derivatives. J. Chem. Soc. 1939, 391-397.
8. Bergmann, E.; Haskelberg, L.; Bergmann, F. Successive diene addition and dehydrogenation in
nitrobenzene solution without isolation of the hydroaromatic intermediate. J. Org. Chem. 1942, 7,
303-306.
9. Muschik, G.M.; Tomaszewski, J.E.; Sato, R.I. Synthesis of the 1-,2-,3-,4-hydroxy isomers of
benz[a]anthracene-7,12-dione, benz[a]anthracene, and 7,12-dimethylbenz[a]anthracene. J. Org.
Chem. 1979, 44, 2150-2153.
10. Puchkov, V.A. Synthesis of 1-phenylanthraquinone.Zh. Vsesoy. Khim. Obshch. im. D. I.
Mendeleeva 1961, 6, 238-239; [Chem. Abstr. 1961, 55, 19877g].
11. Battegay, M.; Claudin, J. Dibromoanthraquinones. Bull. Soc. Chim. Fr. 1921, 29, 1017-1027.
12. Li, Y.Q.; Thiemann, T.; Sawada, T.; Tashiro, M. Novel crown ethers by oxidative cycloaddition
of thiopheno crown ethers. J. Chem. Soc., Perkin Trans. 1 1994, 2323-2329.
13. Thiemann, T.; Li, Y.Q.; Mataka, S.; Tashiro, M. Intramolecular oxidative cycloaddition of
thiophenes. J. Chem. Res. (S) 1995, 384-384, (M) 1995, 2364-2379.
14. Thiemann, T.; Li, Y.Q.; Thiemann, C.; Sawada, T.; Ohira, D.; Tashiro, M.; Mataka, S. Oxidative
cycloaddition of structures with multi core thiophenes. Heterocycles 2000, 1215-1230.
15 Li, Y.Q.; Matsuda, M.; Thiemann, T.; Sawada, T.; Mataka, S. Lewis acid catalysed oxidative
cycloaddition of thiophenes. Synlett. 1996, 461-464.
16. Li, Y.Q.; Thiemann, T.; Sawada, T.; Mataka, S.; Tashiro, M. Lewis acid catalysis in the oxidative
cycloaddition of thiophenes. J. Org. Chem. 1997, 62, 7926-7936.
17. Li, Y.Q.; Thiemann, T.; Mimura, K.; Sawada, T.; Mataka, S.; Tashiro, M. Oxidative
cycloaddition
of
thiophenophanes
–
[n](2,5)-parathiophenophane
(n=8,10-12.14).

Molecules 2009, 14
1029
[8](2,4)metathiophenophane and [2.2](2,5)parametathiophenophane. Eur. J. Org. Chem. 1998,
1841-1850.
18. for reviews, see: Thiemann T.; Dongol, K.G. Thiophene-S-oxides. J. Chem. Res. (S) 2002, 303-
308; (M) 2002, 701-708 and ref.18.
19. Thiemann, T.; Walton, D.J.; Brett, A.O.; Iniesta, J.; Marken, F.; Li, Y.Q. The chemistry of
thiophene-S-oxides and related compounds. ARKIVOC 2009, Vol. ix, 96-113.
20. Exceptions are strained thiophenes: Nakayama J.; Kuroda, K. Synthesis and reactivities of a
highly
strained
thiophene
with
two
fused
four-membered
rings,
1,2,4,5-
tetahydrodicyclobuta[b,d]thiophene. J. Am. Chem. Soc. 1993, 115, 4612-4617 and ref. 21, 22.
21. Thiophenes with very effective electron-donor substituents: Barker, J.M.; Huddleston, P.R.;
Shutler, S.W. Preparation and reactions of 2,5-dimethoxythiophene. J. Chem. Soc., Perkin Trans.
1 1975, 2483-2484.
22. Wynberg, H.; Helder, R. One-step ring enlargement of a thiophene to a thiepin. Tetrahedron Lett.
1972, 3647-3650.
23. This is underscored by theoretical calculations, see, cf.: Jursic, B.S.; Coupe, D. AM1
semiempirical searching for suitable thiophene derivatives that will enable thiophenes to act as a
diene in the Diels-Alder reactions. J. Heterocycl. Chem. 1995, 32, 483-489.
24. Furukawa, N.; Zhang, S.; Sato, S.; Higaki, M. Simple procedure for the synthesis of 2,5-
bis(silylated) thiophene S-oxides with m-chloroperbenzoic acid in the presence of BF3(Et2O).
Heterocycles 1997, 44, 61-66.
25. Nakayama, J.; Nagasawa, H.; Sugihara, Y.; Ishii, A. Synthesis, isolation, and full characterization
of the parent thiophene 1,1-dioxide. J. Am. Chem. Soc. 1997, 119, 9077-9078.
26. Furukawa, N.; Zhang, S.-Z.; Horn, E.; Takahashi, S.; Sato, S.; Yokoyama, M.; Yamaguchi, K. X-
ray crystallographic analysis of 2,5-bis(diphenylmethylsilyl)thiophene monooxide and the Diels-
Alder reaction of thiophene monooxide with dienophiles. Heterocycles 1998, 47, 793-809.
27. Pouzet, P.; Erdelmeier, I.; Ginderow, D.; Mornon, J.-P.; Dansette, P.M.; Mansuy, D. Thiophene 1-
oxides. V. comparison of the crystal structures and thiophene ring aromaticity of 2,5-
diphenylthiophene, its sulfoxide and sulfone. J. Heterocycl. Chem. 1997, 34, 1567-1574.
28. Pouzet, P.; Erdelmeier, I.; Ginderow, D.; Mornon, J.-P.; Dansette, P.M.; Mansuy, D. Thiophene
S-oxides: convenient preparation, first complete structural characterization and unexpected
dimerization of one of them, 2,5-diphenylthiophene 1-oxide. J. Chem. Soc., Chem. Commun.
1995, 473-474.
29. Torssell, K. Diels-Alder reactions of thiophene oxides generated in situ. Acta Chem. Scand., Ser.
B 1976, 30, 353-357.
30. Thiemann, T.; Sa e Melo, M.L.; Campos Neves, A.S.; Li; Y.Q.; Mataka, S.; Tashiro, M.; Geiβler,
U.; Walton, D. Preparation and electrooxidative SO-extrusion of halogenated 7-
thiabicyclo[2.2.1]heptene 7-oxides. J. Chem. Res. (S) 1998, 346-347.
31. Raasch, M.S. Annulations with tetrachlorothiophene 1,1-dioxide. J. Org. Chem. 1980, 45, 856-
867.
32. Raasch, M.S. Addition-rearrangement reactions of halogenated thiophene dioxides with furans. J.
Org. Chem., 1980, 45, 867-870.
33. Hamon, D.P.G.; Spurr, P.R. A simple construction of the iceane skeleton via an intramolecular

Molecules 2009, 14
1030
Diels-Alder reaction. J. Chem. Soc., Chem. Commun. 1982, 372-373.
34. Hesse, M.; Meier, H.; Zeeh, B. Spectroscopic Methods in Organic Chemistry; Georg Thieme
Verlag: Stuttgart, Germany, 1997; p. 246.
35. Wraight, E.S. Some Newer Phys. Methods Struct. Chem., Proc. Symp. 1967, 67-67; [Chem. Abstr.
1969, 70, 62337u].
36, Yoshida, Z.; Takabayashi, F. Electronic spectra of monosubstituted anthraquinones and solvent
effects. Tetrahedron 1968, 24, 933-943.
37. Peters, R.H.; Sumners, H. Spectra of anthraquinone derivatives. J. Chem. Soc. 1953, 2101-2110.
38. cf., Ertas, E.; Ozturk, T. A new reaction of P4S10 and Lawesson's reagent; a new method for the
synthesis of dithieno[3,2-b;2',3'-d]thiophenes. Tetrahedron Lett. 2004, 45, 3405-3407.
39. see also: Goldberg, Y.; Alper, H. Electrophilic halogenation of aromatics and heteroaromatics
with N-halosuccinimides in a solid/liquid system using an H+ ion exchanger or ultrasonic
irradiation. J. Mol. Cat. 1994, 88, 377-383.
40. Gjoes, N.; Gronowitz, S. Substitution reactions of 2-phenylthiophene. Acta Chem. Scand. 1972,
26, 1851-1859.
41. This reaction has been reported to proceed under YbCl3 catalysis: Fang, X.; Warner, B.P.;
Watkin, J.G. Ytterbium trichloride-catalyzed Diels-Alder reactions of un-activated dienes. Synth.
Commun. 2000, 30, 2669-2676. We have found that it proceeds also in the presence of EuCl3.
42. Here, we have used a biphasic system of 4N aq. NaOH and ether under ultrasonication. The
enolisation has been reported to also go very well in the presence of triethylamine (Et3N) or in the
presence of acids such as HCl: Fernandez, M.P.; Gonzalez, B.; Pardo, M.; Soto, J.L. 1,3-Dipolar
cycloaddition of nitrile oxides with Diels-Alder adducts of p-benzoquinone and 1,4-
naphthoquinone. Anal. Quim. 1994, 90, 477-482 (for Et3N), also see ref. [43].
43. Kotha, S.; Manivannan, E. Synthesis of functionalized cis-syn-cis triquinanes. Ind. J. Chem., Sect.
B 2002, 41B, 808-811 (for HCl).
44. We used Ag2O in benzene as the oxidation agent as described for the oxidation of other
hydroquinones to quinones. The reaction gives quantitative yields of 6,7-dimethyl-5,8-dihydro-
1,4-naphthoquinone, when carried out at rt. Specifically for the transformation of 6,7-dimethyl-
5,8-dihydronaphthalene-1,4-diol to 6,7-dimethyl-5,8-dihydro-1,4-naphthoquinone, the use of
MnO2 in acetone has been described, also: ref. [43].
45. cf., Fuchibe K.; Akiyama, T. Low-valent niobium-mediated double activation of C-F/C-H bonds:
fluorene synthesis from o-arylated alpha,alpha,alpha-trifluorotoluene derivatives. J. Am. Chem.
Soc. 2006, 128, 1434-1435.
46. Kondo, M.; Murata, M.; Nishihara, H.; Nishibori, E.; Aoyagi, S.; Yoshida, M.; Kinoshita, Y.;
Sakata, M. Guest-induced instant and reversible crystal-to-crystal transformation of 1,4-
bis(ferrocenylethynyl)anthraquinone. Angew. Chem. Int. Ed. Engl. 2006, 45, 5461-5464.
47. Hofmann, A. Substituted benzoylbenzoic acids. Monatsh. Chem. 1915, 36, 805-824.
48. Castle, R.N.; Kudo, H.; Lee, M.L. The synthesis of some monomethylanthracenamines. Coll.
Czech Chem. Commun. 1991, 56, 2269-2277.
49. Mizuno, H.; Kubota S. (Seiko Epson Corp.), Method of distinguishing right from left contact
lenses by coloring. JP Pat. 04011214, 1992; [Chem. Abstr. 1992, 116, 221636].
50. Ganushchak, N.I.; Dombrovskii, A.V.; Vislobitskaya, O.A. Syntheses based on Diels-Alder

Molecules 2009, 14
1031
condensations. I. 1-Methyl-4-arylanthraquinones. Zh. Obshch. Khim. 1963, 33, 2532-2534.
Sample Availability: Samples of the compounds 4b-4f, 4m are available from the authors.
© 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.
This article is an open-access article distributed under the terms and conditions of the Creative
Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).