Facile synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-anthraquinone dyes for improved supercritical carbon dioxide dyeing

Article abstract of DOI:10.1016/j.dyepig.2019.107991

Supercritical carbon dioxide (scCO₂) has recently been conquering both material sciences and process engineering owing to its intriguing properties like high diffusivity and tuneable (de)solubilizing performance. However, except for impregnation with biocidal preservatives, utilization of scCO₂ for modification of wood including dyeing has been hitherto less explored. Therefore, we recently proposed a green wood dyeing approach that relies on the excellent carrier medium properties of CO₂ for non-polar disperse dyes in supercritical conditions and their reversion when leaving the supercritical state. However, using a common disperse dye of the 9,10-anthraquinone family (Disperse Blue, DB-134) without the addition of co-solvent, only a moderate colour change was obtained for the interior of small wood cuboids (1 cm × 1 cm x 2 cm) even after extensive variation of scCO₂ process conditions. Insufficient solubility of the dye in scCO₂ was assumed to be a major hindrance for homogeneous wood dyeing. Therefore, we synthesized a variety of 1-n-butylamino- and 1,4-bis(n-butylamino)-9,10-anthraquinone derivatives carrying different alkyl moieties in 2-position, which was confirmed to improve scCO₂ solubility. Instead of a previously reported seven-step synthesis affording moderate yields only (60% on average), we propose an alternate much simpler synthesis comprising of Marschalk alkylation (2-position) and a sequence of tosylation and n-alkylamination (1-position). The latter proved to pave way to a wide variety of colours and disperse dyes of improved solubility in scCO₂. Moreover, all products were characterized by various techniques including liquid-state ¹H and ¹³C NMR and X-ray crystallography. Complementing X-ray diffraction, quantum-mechanical simulations were performed to predict or confirm conformation and colour of selected compounds.

Full text of DOI:10.1016/j.dyepig.2019.107991

Journal Pre-proof
Facile synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-anthraquinone
dyes for improved supercritical carbon dioxide dyeing
Julien Jaxel, Hassan Amer, Markus Bacher, Alexander Roller, Matthias
Guggenberger, Nele Sophie Zwirchmayr, Christian Hansmann, Falk Liebner
PII:
S0143-7208(19)31861-3
DOI:
https://doi.org/10.1016/j.dyepig.2019.107991
DYPI 107991
Reference:
To appear in: Dyes and Pigments
Received Date: 4 August 2019
Revised Date: 20 October 2019
Accepted Date: 21 October 2019
Please cite this article as: Jaxel J, Amer H, Bacher M, Roller A, Guggenberger M, Zwirchmayr NS,
Hansmann C, Liebner F, Facile synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-
anthraquinone dyes for improved supercritical carbon dioxide dyeing, Dyes and Pigments (2019), doi:
https://doi.org/10.1016/j.dyepig.2019.107991.
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2019 Published by Elsevier Ltd.

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Facile synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-anthraquinone dyes for
improved supercritical carbon dioxide dyeing
a,b
a,c
a
d
a
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Julien Jaxel , Hassan Amer , Markus Bacher , Alexander Roller , Matthias Guggenberger , Nele
a
b
a,b,e*
Sophie Zwirchmayr , Christian Hansmann , Falk Liebner
a
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Institute for Chemistry of Renewable Resources, University of Natural Resources and Life Science Vienna,
Konrad-Lorenz-Straße 24, 3430 Tulln an der Donau, Austria
b
Wood K plus - Competence Center for Wood Composites & Wood Chemistry Ltd., Altenberger Straße 69, A-
4040 Linz, Austria
c
Department of Natural and Microbial Products Chemistry, National Research Centre, P.O. 12622, Dokki, Giza,
Egypt
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d
X-Ray Structure Analysis Center, Faculty of Chemistry, University of Vienna, Währingerstrasse 42, 1090
Vienna, Austria
e
Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal
*Falk Liebner: falk.liebner@boku.ac.at
Abstract
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Supercritical carbon dioxide (scCO ) has recently been conquering both material sciences and
2
process engineering owing to its intriguing properties like high diffusivity and tuneable
(de)solubilizing performance. However, except for impregnation with biocidal preservatives,
utilization of scCO for modification of wood including dyeing has been hitherto less explored.
2
Therefore, we recently proposed a green wood dyeing approach that relies on the excellent carrier
medium properties of CO for non-polar disperse dyes in supercritical conditions and their reversion
2
when leaving the supercritical state. However, using a common disperse dye of the 9,10-
anthraquinone family (Disperse Blue, DB-134) without the addition of co-solvent, only a moderate
colour change was obtained for the interior of small wood cuboids (1 cm x 1 cm x 2 cm) even after
extensive variation of scCO process conditions. Insufficient solubility of the dye in scCO was
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assumed to be a major hindrance for homogeneous wood dyeing. Therefore, we synthesized a
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variety of 1-n-butylamino- and 1,4-bis(n-butylamino)-9,10-anthraquinone derivatives carrying
different alkyl moieties in 2-position, which was confirmed to improve scCO solubility. Instead of a
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previously reported seven-step synthesis affording moderate yields only (60% on average), we
propose an alternate much simpler synthesis comprising of Marschalk alkylation (2-position) and a
sequence of tosylation and n-alkylamination (1-position). The latter proved to pave way to a wide
variety of colours and disperse dyes of improved solubility in scCO . Moreover, all products were
2
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characterized by various techniques including liquid-state H and C NMR and X-ray crystallography.
Complementing X-ray diffraction, quantum-mechanical simulations were performed to predict or
confirm conformation and colour of selected compounds.
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Keywords
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Supercritical carbon dioxide dyeing, anthraquinone disperse dyes, colouring of massive wood,
Marschalk alkylation, alkylamination of 1-hydroxy and 1,4-dihydroxyanthraquinone derivatives
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1.
Introduction
Dyeing of wood is still a vivid field of research and development in high-end wood
processing. This applies in particular for the manufacture of massive wood furniture which currently
experiences a renaissance in Europe. Extending the ranges of colours and of possibly harmless dyes
is therefore a major goal of both manufacturers and distributors to satisfy the current demands of
customers. Aiming at both adaption of massive wood colouring towards new dyes and development
of more efficient dyeing approaches in terms of required time, homogeneity and environmental
compatibility, supercritical carbon dioxide (scCO ) was recently proposed as green carrier medium
2
for that purpose [1, 2]. Carbon dioxide in the supercritical state is indeed an appealing solvent for
dyeing owing to its high dissolution power and diffusivity, abundance, low cost, recyclability,
inertness, incombustibility and non-toxicity. Furthermore, its low critical point (31.2°C, 7.38 MPa [1])
renders the process less challenging in terms of equipment demands compared to other supercritical
fluids. Considering these intriguing properties, it is rather surprising that scCO has hitherto not yet
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established in wood colouring even though its utilization for wood modification reaches back to the
early days of supercritical technologies, i.e. the mid-80s of the previous century. Impregnation of
wood with biocides [3-9] as one of the few intensively researched applications has even succeeded
upscaling to an industrial process [10]. Hydrophobization of wood for outdoor applications, such as
by acetylation [11] or impregnation with polysiloxanes [12, 13] is another modification approach
that was also demonstrated to benefit from the intriguing properties of scCO as a carrier medium.
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However, similar as with a series of other scCO applications, scaling-up and implementation into an
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industrial process has here not been accomplished yet, presumably in the first line due to the high
investment cost of the required high-pressure equipment.
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The excellent solvation power for lipophilic compounds, such as for disperse dyes used in
massive wood colouring, is probably one of the biggest assets of scCO . While the former is
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contributed by liquid-like densities, high diffusion coefficients and low viscosities – both comparable
to that of gases – enable fast diffusion of solubilised compounds. Since both solvent power and
diffusivity can be easily tuned by variation of pressure and temperature, a wide range of process
conditions can be easily established.
Dyeing of polyester fibers using scCO is an environmental-friendly process that has been
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established on industrial scale, such as for colouring of poly(ethylene terephthalate) (PET). Main
advantages of using scCO as carrier medium include i) circumvention of high temperatures owing to
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the plasticizing effect of scCO facilitating dye uptake at moderate temperatures [14, 15], ii)
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improved separation and recovery of unreacted dye as accomplished by decreasing pressure at the
end of the scCO dyeing procedure [16, 17] and iii) excellent recycling rates of both CO (up to 95%)
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and dyes. These advantages render scCO dyeing more efficient from the economic point of view
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compared to the still widely used hot water process [17].
Nevertheless, strict control of process parameters is required to obtain satisfying results in
scCO dyeing. Solubility of the respective disperse dyes in scCO is one of the most critical issues in
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this regard [17]. Next to its molecular structure, solubility is strongly dependent on both pressure
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and temperature. While disperse dyes feature moderate solubility only in the early supercritical
state, i.e. at comparatively mild temperature and pressure, increase of both temperature and/or
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pressure typically improves solubility (e.g. for Disperse Blue 134: y = 1.2 x 10 molDisperse Blue 134.mol(CO2
-
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-1
at 10.0 MPa and 50°C compared to 67.7 x 10 molDisperse Blue 134.mol
(CO2 + Disperse Blue 134)
+
Disperse Blue 134)
at 20.0 MPa and 80°C [18]). Considering industrial scale dyeing of massive wood this implicates the
necessity of higher one-off investment in high pressure and temperature resistant equipment and
acceptance of higher energy running costs.
Besides increase of pressure and temperature, addition of a co-solvent is another measure
to increase the solubility of low-molecular compounds in scCO such as disperse dyes. Acetone,
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ethanol and methanol are probably the most frequently used co-solvents in scCO processes,
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including extraction of coffee, tea, herbs and other natural products to obtain fragrances, flavour,
bioactive compounds or essential oils [19]. There is evidence that these co-solvents rather interact
with the respective organic target compounds than change the polarity of the extraction medium
[20]. If the process to be developed is intended to meet the standards of green chemistry in terms of
organic solvent-free processes, addition of co-solvents, even in small amounts (typically 3-10 mol%)
is a serious drawback.
On top of all there is consent that solubility of a certain organic compound in scCO is
2
governed by intrinsic physical properties. Low molecular weight, low content of polar groups and
strong hydrophobicity are prerequisites to render a compound soluble in scCO . Particularly for
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scCO dyeing approaches, high dye solubility is desired to improve the efficiency of dyeing and to
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reduce the above-discussed costs for equipment, energy and co-solvents.
Addition of longer-chain alkylamino groups to 9,10-anthraquinone used in colouring of
polypropylene fibers has been demonstrated to increase lipophilicity and, hence, solubility in scCO2.
Part of these non-polar moieties were introduced in form of alkylamino groups to enhance final
colour strength, improve dyeability and colour fastness of propylene fabric. However, the effect
levelled-off at chain lengths of about 8 and started to decrease significantly for substituents
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composed of more than 12 carbon atoms [21]. Specifically for anthraquinone dyes it is well known
that longer-chain alkyl substituents in ortho position of 1-hydroxy or 1-alkylamino groups have a
positive impact on the solubility of the respective dyes in scCO facilitating dyeing at milder
2
conditions [18, 22, 23]. Shamsipur and co-workers proposed the introduction of the lipophilic
aliphatic moieties by seven-step synthesis starting from 2-methyl-9,10-anthraquinone. Following
nitration using potassium nitrate and concentrated sulfuric acid, the obtained intermediate is
reduced with sodium sulfide in boiling ethanol to obtain 1-amino-2-methyl-9,10-anthraquinone.
Conversion of the amino group into a hydroxyl moiety is accomplished by nitrosation and
subsequent displacement of the diazonium salt by a hydroxyl group in a Sandmeyer-type reaction to
afford the respective 1-hydroxy-2-methyl-9,10-anthraquinone. The introduced hydroxyl group is
subsequently protected by methylation before the adjacent methyl group is converted into a
bromomethyl moiety by treatment with N-bromosuccinimide and dibenzoyl peroxide. Conversion of
the –CH Br group into –CH OR moieties (R = propyl, butyl, etc.) can be accomplished only after
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deprotection (demethylation) of the hydroxyl group in 1-position using hydrobromic acid in glacial
acetic acid. The obtained 1-hydroxy-2-bromomethyl-9,10-anthraquinone reacts then easily with
different alcohols in the presence of potassium carbonate to the desired 2-alkoxymethyl derivatives.
However, despite the considerable synthesis efforts and variation of chain length, the colour of the
obtained family of 1-hydroxy-2-(1-alkyloxymethyl)-9,10-anthraquinones turned out to be limited to
the yellow to orange range.
Approximating solutions of the electronic Schrödinger equation is the fundamental approach
of ab initio quantum chemical simulation methods. These methods allow the prediction of a whole
array of atomic and molecular characteristics including molecular orbitals and spectroscopic
properties. Thereby just spatial coordinates of the studied system and its number of electrons is
required as input. For these reasons they are a vital tool for the characterization of small organic
molecules, such as the disperse dyes described in the present work. There are different
opportunities to obtain respective approximated solutions of the Schrödinger equation, with Density
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Functional Theory (DFT) based approaches being among the most successful and popular ones. In
DFT, the energy of a system is described by its electron density expressed by a so called electron
density function. This is in contrast to the also very important Hartree-Fock method that relies on
modelling of each single electron individually [24, 25]. For the current work, calculations based on
density functional theory were employed to firstly optimize the geometries of the different products
synthesized and secondly to examine their spectroscopic properties in the UV-vis range.
In view of the elaborate synthesis approach towards anthraquinone dyes of improved scCO2
solubility, the current demands for massive wood furniture covering a wide gamut of colours and
taking into account the fact that native European wood is inherently yellowish to brownish, this
work targeted two goals. First Marschalk alkylation was explored as a hypothetically more
straightforward approach towards synthesis of 2-alkyl substituted 1-hydroxy-9,10-anthraquinone (1)
and 1,4-dihydroxy-9,10-anthraquinone (1’, quinizarin, Solvent Orange 86) featuring increased scCO2
solubility. Second, we attempted to achieve a broader colour variety in particular towards red and
even blue shades by replacing the respective OH groups of compound 1 and 1’ (Figure 1) by strongly
electron donating alkyl amino groups and, thus, benefiting from the expected extent of the
bathochromic shift [26].
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Results and discussion
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Figure 1 shows the three-step approach towards the four groups of compounds synthesized
in this work, i.e. 1-hydroxy-2-alkyl-9,10-anthraquinones, 1,4-dihydroxy-2-alkyl-9,10-anthraquinones,
1-butylamino-2-alkyl-9,10-anthraquinones and 1,4-bis(butylamino)-2-alkyl-9,10-anthraquinones.
Numbering, yields and selected properties in terms of colour and melting points of all compounds
have been compiled in Table 1.
In the first step of the employed reaction sequence (I, Figure 1), the educts 1 and 1’ were
subjected to Marschalk alkylation [27, 28]. In this reaction both 1-hydroxy-9,10-anthraquinone and
1,4-dihydroxy-9,10-anthraquinone are intermediary reduced by sodium dithionite to their respective
leuko forms. The latter undergoes then condensation with the respective aldehydes added to yield
the desired 2-alkylated 9,10-anthraquinones. Since the reaction was conducted in alkaline medium,
introduction of the alkyl substituent occurred selectively in C2 position which is in agreement with
the literature [29] and was confirmed by NMR spectroscopy. While the yields of the 1-hydroxy-2-
alkyl-9,10-anthraquinone compounds (2a-c) were between 27.5 and 63.6% only, they were distinctly
higher for the 1,4-dihydroxy-9,10-anthraquinone counterparts (71.9-83%).
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a: R = H; R = But
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b: R = H; R = Hex
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O
O
OH
O
O
OH
O
O
OTs
3c: R = H; R = Oct
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R
IIa/IIb
R
3d: R = H; R = H
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a': R = OTs; R = But
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R
R
R
3b': R = OTs; R = Hex
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c': R = OTs; R = Oct
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: R = H
2a
2a'
: R = OH; R = But
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:
R = H; R = But
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d': R = OTs; R = H
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': R = OH
2b
2b'
: R = OH; R = Hex
:
R = H; R = Hex
III
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c: R = H; R = Oct
2c': R = OH; R = Oct
HN
O
O
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R
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R
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a: R = H; R = But
4a': R = NHBut; R = But
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b: R = H; R = Hex
4b': R = NHBut; R = Hex
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c: R = H; R = Oct
4c': R = NHBut; R = Oct
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d: R = H; R = H
4d': R = NHBut; R = H
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Figure 1. Reaction sequence for the synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-
anthraquinone dyes - I: Marschalk alkylation: 1. MeOH:H O (1:1), 5wt% NaOH, Na S O ,
2
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corresponding aldehyde, 75°C, Ar atmosphere. 2. Cooling followed by addition of 2M HCl. IIa:
Tosylation using tetra butyl ammonium bromide (TBAB) as phase-transfer catalyst (PTC):
Dichloromethane/H O, p-toluene sulfonyl chloride (TsCl), triethylamine (Et N), room temperature, 3
2
3
days under vigorous stirring. II : Tosylation: Acetonitrile (MeCN), TsCl, Et N, reflux, 5h or overnight.
b
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III: Butylamination: pyridine, large excess of n-butylamine, 50°C, 2 to 5 days.
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Aiming at broadening the colour gamut that is limited to the wavelength range of about 430-
480 nm for the alkylated 1-hydroxy-9,10-anthraquinone (2a-c) and 1,4-dihydroxy-9,10-
anthraquinone disperse dyes (2a’-2c’), the respective hydroxyl groups were replaced by n-butyl
amino moieties that were expected to contribute both increased solubility and bathochromic shift of
light adsorption. Substitution of the hydroxyl groups in compounds 1, 1’, 2a-c and 2a’-2c’ by n-butyl
amino moieties was accomplished by subjecting the products of the Marschalk alkylation to
consecutive tosylation (IIa and IIb in Figure 1) and amination (III). Tetra butyl ammonium bromide
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was used as a phase transfer catalyst in tosylation, since common approaches yielded dark coloured
products that required elaborate purification by column chromatography [30].
Table 1: Labelling. colour, melting point and yield of the compounds synthesized
colour
m.p. [°C]
yield
[mol %]
Marschalk alkylation of 1 and 1’ (Reaction I)
1
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1
1
1
1
-hydroxy-2-butyl-9,10-anthraquinone
-hydroxy-2-hexyl-9,10-anthraquinone
-hydroxy-2-octyl-9,10-anthraquinone
,4-dihydroxy-2-butyl-9,10-anthraquinone
,4-dihydroxy-2-hexyl-9,10-anthraquinone
,4-dihydroxy-2-octyl-9,10-anthraquinone
2a
2b
2c
yellow
yellow
yellow
orange
orange
orange
115-116
99-100
101-104
120-123
99-100
94-95
63.6
55.1
27.5
72.0
71.9
83.0
2a’
2b’
2c’
Tosylation of 1 and 2a-c (Reaction IIa)
1
1
1
1
-p-toluonesulfonyloxy-2-butyl-9,10-anthraquinone
-p-toluonesulfonyloxy-2-hexyl-9,10-anthraquinone
-p-toluonesulfonyloxy-2-octyl-9,10-anthraquinone
-p-toluonesulfonyloxy-9,10-anthraquinone
3a
3b
3c
3d
orange/yellow 107-109
orange/yellow 116-118
64.6
65.2
41.5
41.2
orange/yellow
97-99
orange/yellow 147-149
Tosylation of 1’ and 2a’-c’ (Reaction IIb)
1
1
1
1
,4-p-bis(toluonesulfonyloxy)-2-butyl-9,10-anthraquinone
,4-p-bis(toluonesulfonyloxy)-2-hexyl-9,10-anthraquinone
,4-p-bis(toluonesulfonyloxy)-2-octyl-9,10-anthraquinone
,4-p-bis(toluonesulfonyloxy)-9,10-anthraquinone
3a’
3b’
3c’
3d’
pale yellow
pale yellow
pale yellow
bright yellow
164-166
148-150
134-136
227-230
61.1
64.4
33.3
73.8
Butylamination of 3a-d and 3a’-3d’ (Reaction III)
1
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1
1
1
1
1
1
-butylamino-2-butyl-9,10-anthraquinone
-butylamino-2-hexyl-9,10-anthraquinone
-butylamino-2-octyl-9,10-anthraquinone
-butylamino-9,10-anthraquinone
4a
4b
red
red
50-52
55-57
55-58
80-81
60-61
73-75
60-62
105-108
85.4
85.8
80.0
71.2
63.2
59.9
67.9
73.7
4c
red
4d
red
,4-bis(butylamino)-2-butyl-9,10-anthraquinone
,4-bis(butylamino)-2-hexyl-9,10-anthraquinone
,4-bis(butylamino)-2-octyl-9,10-anthraquinone
,4-bis(butylamino)-9,10-anthraquinone
4a’
4b’
4c’
4d’
blue
blue
blue
blue
5
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All tosylated compounds were purified by recrystallization and obtained at moderate yields. While a
slightly bathochromic effect was observed for the more orange-shaded tosylates of 3a-c, bis-
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tosylation seems to broaden light adsorption considerably as evident from the pale yellow / off-
white appearance of compounds 3a’-c’.
Amination of the (2-substituted) tosylates as conducted in pyridine at 50°C using a large excess of n-
butyl amine was followed by thin-layer chromatography. After quantitative consumption of the
respective educts 3a-3d and 3a’-3d’ the obtained crude products were purified by column
chromatography to yield the products of major interest in high (4a-4c; 80.0-85.8%) and moderate
(4a’-4c’; 59.9-67.9%) yields, respectively. The expected bathochromic effect triggered by
introduction of n-butyl amino groups was confirmed to occur as evident from the shift of colour
from yellow (2a-2c) to red (4a-4c) for the derivatives of 1 and from yellow-orange (2a’-2c’) to blue
(4a’-4c’) for the derivatives of 1’.
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1
Visual colour perception of the purified dyes was complemented by UV/Vis spectroscopy. The
impact of the different substitution pattern on light absorption was studied for two series of
compounds derived from 1-hydroxy-9,10-anthraquinone (1) and 1,4-dihydroxy-9,10-anthraquinone
(quinizarin, 1’). Each set comprises of three compounds representing the synthesis steps i)
Marschalk alkylation (2a, 2a’), ii) tosylation (3a, 3a’) and iii) n-butyl amination (4a, 4a’) conducted in
this work (Figure 2).
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-
1
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Figure 2. UV/Vis spectra of selected 9,10-anthraquinone dyes in 2-propanol (ca. 0.05 mg mL ),
representing the two groups of compounds derived from 1 and 1’ by sequential Marschalk alkylation
(2a, 2a’), tosylation (3a, 3a’) and n-butyl amination (4a, 4a’).
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8
9
0
1
2
3
4
5
6
7
It is evident from Figure 2 that all anthraquinone derivatives are strongly absorbent in the UV region
which is inherent to the anthraquinone basic structure. In the range of the visible light, the π π*
1
absorption maximum of the non-substituted compounds 1 and 1’ is at 403 nm and 481 nm,
respectively. Addition of n-alkyl residues in 2-position effectuates a slight bathochromic shift of the
E-band of the respective parent compounds which was 9 nm (2a) and 3 nm (2a’), respectively, for
introduction of n-butyl moieties. The tosylated compounds (3a and 3a’, Figure 2) did virtually not
show any absorbance in the visible range due to the strongly electron-withdrawing and, hence,
hypsochromic effect of the tosylate groups. The faint yellowish colour visually observed is assumed
to originate from trace residual contents of the respective educts. Amination and eventual
replacement of the tosylate groups by strongly electron donating n-butyl amino moieties had the
desired pronounced bathochromic effect. While the maximum light absorption shifted from 412 nm
(2a) to 509 nm (4a) for the mono amino derivative, it was even more pronounced for the 1,4-bis(n-
butylamino) compound 4a’. Here the maximum absorbance shifted from 481 nm (1’) to 620 nm
(centre of doublet at 597 and 643 nm) which is perceived as deep blue colour.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
8
9
0
1
2
3
4
5
These results are in good agreement with values observed elsewhere [31]. Furthermore, the
observed absorption maxima for 4a and 4a’ correlate well with the results of ab initio molecular
orbital calculations (density functional theory, DFT). The latter yield a red and blue shift for the 1-n-
butylamino (4a, λmax simulation = 522 nm, f = 0.171) and 1,4-bis(n-butylamino) (4a’, λmax simulation = 584
nm, f = 0.270) derivatives of 1-hydroxy-2-n-butyl-9,10-anthraquinone which was in good agreement
with the visual observation. The pronounced shift results from the significant contribution of the n-
butylamino moieties to the highest / lowest occupied molecular orbital (HOMO, LUMO) of 4a’ and
4a which is not the case for the products of the preceding steps (1-3a and 1’-3a’; Figure 3). Quantum
1
1

1
2
computational studies furthermore confirmed the electron withdrawing effect of the p-
toluenesulfonyloxy moieties which is known to impede energy dissipation.
3
4
5
Figure 3. Highest occupied molecular orbital (HOMO, left) and lowest unoccupied molecular orbital
(LUMO, right) of compounds 1, 1’, 2a, 2a’, 3a, 3a’, 4a and 4a’ as calculated by DFT.
6
7
8
9
0
1
2
A comparison of the calculated (DFT) and measured (UV/Vis spectroscopy) maximum adsorption
wavelength values for two sets of compounds derived from 1 (2a-4a; Table 2) and 1’ (2a’-4a’),
respectively, confirms that the application of DFT at the B3LYP/6-311++g(d,p) level of theory is an
appropriate tool to predict the light absorption behaviour of 9,10-anthraquinone derivatives. The
main contributor to the slight differences between calculated and experimental values is supposedly
the insufficient consideration of solvent effects which were here approximated using implicit
solvation with the polarizable continuum model [32, 33].
1
1
1
1
2

1
2
Table 2. Experimental and calculated maximum absorption wavelengths in the visible domain with
their respective molar extinction coefficients and frequencies.
-
1
-1
Compound
1
λmax exp. (nm)
403
εexp. (M .cm )
λmax simulation (nm)
f
5415
412
424
263
522
468
472
200
584
0.164
0.205
0.469
0.171
0.222
0.258
0.311
0.270
2
3
4
a
a
a
412
5912
a
257
n.d.
509
481
484
5795
1
’
6514
2
3
a’
a’
9959
a
203
n.d.
b
4
a’
597
16486
16103
6
43
a
b
3
4
maximum absorption in UV; doublet with similar molar extinction coefficients; n.d.: not
determined.
5
6
7
X-ray diffraction analysis was performed to confirm the chemical structure of compound 4a, to
elucidate its conformation and to compare the structures proposed by quantum chemical DFT
calculations and X-ray analysis.
8
9
0
1
2
3
X-ray data obtained for a single 4a’ crystal were in good agreement with the simulated structure
(details in Supplementary Information). Besides confirmation of its planar structure, compound 4a’
was found to arrange in triclinic unit cells. The hydrogen bonds between the amino and ketone
moieties of 4a’ were noticed (Table 3). They also contribute to the wavelength of the absorption
maximum [34] CIF file for compound 4a’ has been submitted to the Cambridge Crystallographic Data
Centre (Reference number: CCDC1877294).
1
1
1
1
1
3

1
2
3
4
Figure 4. Crystal structure of 4a’ anisotropic displacement ellipsoids visualized with 50% probability
(blue), overlapped with the simulated structure as obtained by DFT (orange). Due to the
asymmetrical structure, HB-1 and HB-2 represent different hydrogen bonds.
5
6
7
8
The anthraquinone skeleton structure as proposed by X-ray analysis shows a high correlation with
that of DFT simulation. The only notable mismatches concern the conformation of the two n-butyl
substituents attached to the amino group and the C2 position which is easily comprehensible due to
their high degrees of rotational freedom.
9
0
1
2
Table 3. Distances of the simulated H-bonds present in 1’, 2a’, 3a’ and 4a’ compared to the H-bonds
a
1
1
1
observed in the X-ray crystallographic data of 4a’. : Isopropanol as solvent was modelled with the
b
Polarisable Continuum Model, : except for the one used to compare the simulated structure of 4a’
c
with the X-ray data, here no solvent was used for modelling. : symmetrical structure.
1
3
1
4

a
a
b
Simulated
Simulated
Simulated
Crystal structure 4a’
1
’
2a’
4a’
(X-ray)
Nature of
the bond
O- - - H-O
O- - - H-O
O- - - H-N
O- - - H-N
HB-1
1
1
.657
.678
1.768
1.773
1.970
1.878
distance (Å)
HB-2
c
1
.681
distance (Å)
1
2
3
3.
Materials and methods
3.1 Materials
4
5
6
7
8
9
0
1
2
3
4
5
6
7
All chemicals were purchased from Sigma-Aldrich, TCI Chemicals or VWR, were of synthesis grade
and used without further purification. Fourier transform infrared spectroscopy (FTIR) was performed
using a Perkin Elmer Frontier IR Single-Range spectrometer (Waltham, Massachusetts, USA) in ATR
mode (diamond/ZnSe crystal, LiTaO detector, KBr windows). All spectra were derived from 16 scans,
3
-
1
-1
each covering the wavelength range of 600 to 4000 cm at a resolution of 4 cm . All spectra were
baseline corrected and normalized to the highest peak. All NMR spectra were measured at 25°C
1
13
1
1
1
1
1
1
1
1
using a Bruker Avance II 400 (resonance frequencies 400.13 MHz for H and 100.63 MHz for C)
instrument. The latter was equipped with a 5 mm broadband probe head (BBFO) with z–gradients.
Standard Bruker pulse programmes were used. The samples were dissolved in 0.6 ml of CDCl (99.8
3
% D, euriso-top, Saint-Aubin, France). Chemical shifts are given in ppm, referenced to residual
1
13
solvent signals (7.26 ppm for H, 77.0 ppm for C). Structure elucidation and confirmation,
1
13
respectively, was accomplished based on the set of complementary H, C-jmod, COSY, HSQC and
HMBC experiments (for peak assignment see Supplementary Information). UV/Vis spectra were
2
acquired with a Perkin Elmer Lambda35 instrument. The high correlation coefficients (R = 0.999)
1
5

1
2
3
4
were used to calculate molar extinction coefficients at the selected wavelength. Elemental analyses
were performed at Microanalytical Laboratory, University of Vienna, Austria (report numbers
0418/0428 and 0518/0616). Melting points were determined from three independent
measurements using a Thermo Scientific 9300 apparatus.
5
6
3.2 General procedure for the Marschalk alkylation of 1-hydroxy-9,10-anthraquinone (1) and
1,4-dihydroxy-9,10-anthraquinone (1’) (Reaction I, Figure 1)
7
8
9
0
1
2
3
4
5
6
1-Hydroxy-9,10-anthraquinone (1) or 1,4-dihydroxy-9,10-anthraquinone (1’) (1 mmol) and Na S O
4
2
2
(5.75 mmol) were co-dissolved in aqueous methanol (50:50, v/v) (50 mL) containing 5 w% of NaOH
under argon atmosphere. Once dissolution was completed, an excess of the respective aldehyde (2a:
butanal, 2b: hexanal etc.) was added and the mixture stirred vigorously at 75°C overnight. After
cooling using an ice-water bath, the product mixture was acidified with HCl (2M, 50-100 mL)
whereupon a change of colour occurred and a precipitate was formed. After filtration and washing
1
1
1
1
1
1
1
with deionized water (500 mL), the pasty product was washed with hot CH OH, which removes
3
1
mainly side-products of competing aldol reactions and residual educts. This was confirmed by H
NMR analysis of the solid product obtained after cooling and freeze-drying (data not shown). The
washing procedure was repeated up to two times yielding (NMR) pure products.
1
7
3.2.1 1-Hydroxy-2-butyl-9,10-anthraquinone (2a)
1
1
2
2
2
2
2
2
8
9
0
1
2
3
4
5
Following the general procedure described in section 2.2, compound 2a was synthesized by reacting
1 (1.34 g, 6 mmol) and Na S O (6 g, 34.5 mmol) with butyraldehyde (6 ml, 66.6 mmol). After work-
2
2
4
-
4
-1
-1
up of the crude product, 1.07g (3.8 mmol) of 2a were obtained. UV (iPrOH) λmax (ε x 10 , M .cm ):
-1
412 (0.59) nm. IR νmax(cm ): 2953, 2932, 2871, 1667, 1628, 1589, 1427, 1353, 1327, 1294, 1260,
1
1203, 1153, 1104, 995, 892, 851, 790, 719, 657. H NMR (400.13 MHz, CDCl ): δ = 13.00 (s, 1H), 8.32
3
(m, 1H), 8.29 (m, 1H), 7.80 (m, 2H), 7.78 (d, J = 7.7 Hz, 1H), 7.54 (d, J = 7.7 Hz, 1H), 2.77 (t, J = 7.7 Hz,
1
3
2H), 1.67 (m, 2H), 1.43 (m, 2H), 0.97 (t, J = 7.3 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 189.07,
3
182.49, 160.95, 139.51, 136.45, 134.50, 133.96, 133.85, 133.40, 131.33, 127.3, 126.88, 119.30,
1
6

1
2
115.46, 31.23, 29.68, 22.59, 13.91. Anal. Calcd. for C H O : C 77.12, H 5.75, N 0. Found.: C 76.80, H
18 16 3
5.60, N <0.05.
3
3.2.2 1-Hydroxy-2-hexyl-9,10-anthraquinone (2b)
4
5
6
7
8
9
0
1
2
3
Following the procedure described in 2.2, 1 (1.12 g, 5 mmol) and Na S O (5 g, 28.7 mmol) were
2 2 4
reacted with hexanal (6 mL, 48.8 mmol) to yield 0.85g (2.76 mmol, 55.1%) of 2b after washing and
-
4
-1
-1
-1
freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10 , M .cm ): 412 (0.67) nm. IR ν /cm : 2950,
max
2926, 2854, 1667, 1628, 1589, 1427, 1353, 1294, 1261, 1200, 1152, 1115, 1042, 1008, 892, 852, 791,
1
717, 658. H NMR (400.13 MHz, CDCl ) δ: 13.00 (s, 1H), 8.32 (m, 1H), 8.29 (m, 1H), 7.80 (m, 2H), 7.78
3
(d, J = 7.7 Hz, 1H), 7.54 (d, J = 7.7 Hz, 1H), 2.77 (t, J = 7.7 Hz, 2H), 1.67 (m, 2H), 1.39 (m, 2H), 1.33 (m,
1
3
1
1
1
1
2H), 1.33 (m, 2H), 0.90 (t, J = 7.0 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 189.09, 182.45, 160.96,
3
139.56, 136.47, 134.50, 133.96, 133.86, 133.41, 131.33, 127.30, 126.88, 119.31, 115.47, 31.67,
30.00, 29.19, 29.06, 22.60, 14.06. Anal. Calcd. for C H O : C 77.9, H 6.54, N 0. Found: C 75.92, H
20
20
3
6.38, N <0.05.
1
4
3.2.3 1-Hydroxy-2-octyl-9,10-anthraquinone (2c)
1
1
1
1
1
2
2
2
2
2
5
6
7
8
9
0
1
2
3
4
Following the procedure described in 2.2, 1 (896.8 mg, 4 mmol) and Na S O (4 g, 23.0 mmol) were
2 2 4
reacted with octanal (7 mL, 44.8 mmol) to yield 0.37g (1.10 mmol, 27.5%) of compound 2c after
-
4
-1
-1
-
washing and freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10 , M .cm ): 412 (0.54) nm. IR νmax/cm
1
: 2950, 2923, 2853, 1668, 1628, 1589, 1427, 1353, 1325, 1289, 1263, 1199, 1152, 1121, 1042, 1009,
1
894, 850, 792, 717, 657. H NMR (400.13 MHz, CDCl ) δ: 13.00 (s, 1H), 8.32 (m, 1H), 8.29 (m, 1H),
3
7.80 (m, 2H), 7.78 (d, J = 7.7 Hz, 1H), 7.54 (d, J = 7.7 Hz, 1H), 2.76 (t, J = 7.7 Hz, 2H), 1.68 (m, 2H), 1.38
1
3
(m, 2H), 1.29 (m, 2H), 1.29 (m, 6H), 0.88 (t, J = 7.0 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 189.08,
3
182.45, 160.95, 139.56, 136.45, 134.50, 133.95, 133.85, 133.41, 131.32, 127.29, 126.88, 119.31,
115.47, 31.87, 30.00, 29.52, 29.43, 29.24, 29.10, 22.65, 14.08. Anal. Calcd. for C H O : C 78.54, H
22
24
3
7.19, N 0. Found: C 78.00, H 7.48, N <0.05.
1
7

1
3.2.4 1,4-Dihydroxy-2-butyl-9,10-anthraquinone (2a’)
2
3
4
5
6
7
8
9
0
Following the procedure described in 2.2, 1’ (720 mg, 3 mmol) and Na S O (3 g, 17.2 mmol) were
2
2
4
reacted with butyraldehyde (3 mL, 33.3 mmol) to yield 0.64 g (2.16 mmol, 72.0%) of compound 2a’
-
4
-1
-1
after washing and freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10 , M .cm ): 484 (1.00), 518
-
1
(0.63) nm. IR νmax/cm : 2962, 2938, 2875, 1625, 1583, 1434, 1404, 1348, 1298, 1267, 1237, 1213,
1
1120, 1065, 1028, 1002, 960, 892, 811, 778, 717, 681. H NMR (400.13 MHz, CDCl ) δ: 13.42 (s, 1H),
3
12.98 (s, 1H), 8.34 (m, 2H), 7.82 (m, 2H), 7.16 (s, 1H), 2.75 (t, J = 7.7 Hz, 2H), 1.67 (m, 2H), 1.44 (m,
1
3
2H), 0.97 (t, J = 7.3 Hz, 3H) . C NMR (100.63 MHz, CDCl ) δ: 187.21, 186.30, 157.89, 157.24, 145.51,
3
134.31, 134.19, 133.72, 133.59, 128.06, 126.99, 126.87, 112.00, 111.04, 30.87, 29.85, 22.52, 13.87.
Anal. Calcd. for C H O : C 72.96, H 5.44, N 0. Found: C 72.98, H 5.37, N <0.05.
1
1
18
16
4
1
3.2.5 1,4-Dihydroxy-2-hexyl-9,10-anthraquinone (2b’)
1
1
1
1
1
1
1
1
2
2
3
4
5
6
7
8
9
0
Following the procedure described in 2.2, 1’ (1.44 g, 6 mmol) and Na S O (6 g, 34.5 mmol) were
2
2
4
reacted with hexanal (7.2 mL, 58.5 mmol) to yield 1.40 g (4.32 mmol, 71.9%) of compound 2b’ after
-
4
-1
-1
washing and freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10 , M .cm ): 484 (0.95), 518 (0.60) nm.
-
1
IR νmax/cm : 3068, 2931, 2855, 1621, 1582, 1426, 1398, 1344, 1305, 1242, 1217, 1119, 1067, 1031,
1
960, 916, 814, 785, 720, 681. H NMR (400.13 MHz, CDCl ) δ: 13.42 (s, 1H), 12.98 (s, 1H), 8.34 (m,
3
2H), 7.82 (m, 2H), 7.16 (s, 1H), 2.75 (t, J = 7.7 Hz, 2H), 1.68 (m, 2H), 1.41 (m, 2H), 1.34 (m, 4H), 0.90
1
3
(t, J = 7.1 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 187.21, 186.30, 157.89, 157.24, 145.56, 134.31,
3
134.19, 133.73, 133.60, 128.06, 126.99, 126.87, 112.01, 111.04, 31.63, 30.16, 29.11, 28.71, 22.57,
14.06. Anal. Calcd. for C H O : C 74.06, H 6.21, N 0. Found: C 73.13, H 6.05, N <0.05.
20
20
4
2
1
3.2.6 1,4-Dihydroxy-2-octyl-9,10-anthraquinone (2c’)
2
2
2
2
3
4
Following the procedure described in 2.2, 1’ (1.44 g, 6 mmol) and Na S O (6 g, 34.5 mmol) were
2
2
4
reacted with octanal (10 mL, 64.0 mmol) to yield 1.75 g (4.98 mmol, 83.0%) of compound 2c’ after
-
4
-1
-1
washing and freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10 , M .cm ): 484 (0.97), 518 (0.61) nm.
1
8

-
1
1
2
3
4
5
6
IR νmax/cm : 3070, 2919, 2853, 1622, 1583, 1426, 1404, 1345, 1268, 1236, 1210, 1118, 1070, 1023,
1
959, 906, 813, 788, 719, 681. H NMR (400.13 MHz, CDCl ) δ: 13.42 (s, 1H), 12.99 (s, 1H), 8.34 (m,
3
2H), 7.82 (m, 2H), 7.16 (s, 1H), 2.74 (t, J = 7.8 Hz, 2H), 1.68 (m, 2H), 1.40 (m, 2H), 1.29 (m, 8H), 0.89
13
(t, J = 7.2 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 187.21, 186.30, 157.89, 157.24, 145.57, 134.31,
3
134.19, 133.73, 133.60, 128.06, 126.99, 126.87, 112.01, 111.04, 31.86, 30.16, 29.45, 29.39, 29.21,
28.75, 22.65, 14.07. Anal. Calcd. for C H O : C 74.98, H 6.21, N 0. Found: C 75.01, H 6.84, N <0.05.
22
24
4
7
8
3.3 General procedure for the tosylation of 1-hydroxy-9,10-anthraquinone (1) and 1-hydroxy-2-
alkyl-9,10-anthraquinones (2a-c) (Reaction IIa)
9
0
1
2
3
4
5
6
7
8
9
0
1
Common tosylation of 1-hydroxy-9,10-anthraquinone (1) and 1-hydroxy-2-alkyl-9,10-anthraquinones
(2a-c) with p-toluenesulfonyl chloride (TsCl) and pyridine [30] turned out to afforded dark brownish
solids which required elaborate purification by column chromatography prior further modification.
This obstacle could be overcome by performing sulfonylation in a biphasic medium
(water/dichloromethane) using tetra butyl ammonium bromide (TBAB) as a phase transfer catalyst.
1
1
1
1
1
1
1
1
1
1
2
2
+
-
Controlled by pH (61.6 mM NaOH), TBAB is converted into (C H ) N OH that migrates into the upper
4
9 4
organic phase and forms there under release of water the respective tetra butyl ammonium salts of
compounds 1 or 2a-c. The latter eventually react with TsCl to afford the tosylates 3a-3d and
+
-
(C H ) N Cl migrates back into the aqueous phase. All reactions were performed at room
4
9 4
temperature in a round bottom flask under vigorous stirring. After completion of the reaction (ca. 3
days) which was determined by TLC (SiO , CH Cl ), the organic phase was separated, washed
2
2
2
exhaustively with deionized water and dried over anhydrous Na SO . After evaporation of the
2
4
organic phase, the solid products were recrystallized from CHCl /hexane.
3
2
2
3.3.1 1-p-Toluonesulfonyloxy-2-butyl-9,10-anthraquinone (3a)
2
2
2
3
4
5
Following the procedure described in section 2.3 (Reaction IIa, Figure 1), 2a (1.12 g, 4 mmol) and
TsCl (3.89 g, 20.4 mmol) in CH Cl (280 mL) were mixed with a solution of NaOH (1.18 g, 29.6 mmol)
2
2
and TBAB (6.576 g, 20.4 mmol) in deionized water (480 mL). After working-up of the reaction
1
9

1
2
3
4
5
6
7
8
9
mixture and recrystallization from CHCl /hexane 1.12 g (2.58 mmol, 64.6%) of 3a were obtained (cf.
3
-
1
Table 1). IR νmax/cm : 2962, 2930, 2873, 1675, 1588, 1493, 1452, 1426, 1384, 1314, 1275, 1237,
1
1165, 1090, 1041, 1006, 975, 931, 892, 852, 816, 761, 738, 662. H NMR (400.13 MHz, CDCl ) δ: 8.23
3
(d, J = 7.9 Hz, 1H), 8.22 (m, 1H), 8.08 (m, 1H), 7.84 (d, J = 8.3 Hz, 2H), 7.75 (m, 2H), 7.65 (d, J = 7.9 Hz,
1H), 7.33 (d, J = 8.3 Hz, 2H), 2.61 (t, J = 7.8 Hz, 2H), 2.42 (s, 3H), 1.55 (m, 2H), 1.29 (m, 2H), 0.90 (t, J =
1
3
7.3 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 182.25, 181.98, 145.61, 145.45, 145.23, 135.48, 134.71,
3
134.09, 133.65, 133.46, 133.37, 132.45, 129.8, 129.8, 128.7, 128.24, 127.30, 126.67, 126.16, 31.81,
30.26, 22.54, 21.68, 13.76. Anal. Calcd. for C H O S : C 69.11, H 5.1, N 0, S 7.38. Found: C 68.94, H
25
22
5 1
5.1, N <0.05, S 7.4.
1
0
3.3.2 1-p-Toluonesulfonyloxy-2-hexyl-9,10-anthraquinone (3b)
1
1
1
1
1
1
1
1
1
2
2
2
1
2
3
4
5
6
7
8
9
0
1
2
Following the procedure described in section 2.3 (Reaction IIa, Figure 1), 2b (616 mg, 2 mmol) and
TsCl (1.94 g, 10.2 mmol) in CH Cl (140 mL) were mixed with a solution of NaOH (594 mg, 14.8 mmol)
2
2
and TBAB (3.29 g, 10.2 mmol) in deionized water (240 mL). After working-up of the reaction mixture
and recrystallization from CHCl /hexane 603 mg (1.30 mmol, 65.2%) of 3b were obtained (cf. Table
3
-
1
1). IR νmax/cm : 2962, 2934, 2858, 1676, 1588, 1468, 1374, 1311, 1284, 1220, 1156, 1089, 1038,
1
1004, 890, 848, 816, 767, 737, 717, 670, 632. H NMR (400.13 MHz, CDCl ) δ: 8.23 (d, J = 8.0 Hz, 1H),
3
8.22 (m, 1H), 8.09 (m, 1H), 7.84 (d, J = 8.4 Hz, 2H), 7.75 (m, 2H), 7.65 (d, J = 8.0 Hz, 1H), 7.33 (d, J =
13
8.4 Hz, 2H), 2.60 (t, J = 7.8 Hz, 2H), 2.42 (s, 3H), 1.56 (m, 2H), 1.27 (m, 6H), 0.88 (t, J = 6.7 Hz, 3H). C
NMR (100.63 MHz, CDCl ) δ: 182.24, 181.98, 145.62, 145.42, 145.22, 135.45, 134.70, 134.08, 133.64,
3
133.48, 133.36, 132.44, 129.79, 128.69, 128.22, 127.30, 126.66, 126.15, 31.47, 30.55, 29.64, 29.11,
22.52, 21.67, 14.02. Anal. Calcd. for C H O S : C 70.11, H 5.67, N 0, S 6.93. Found: C 69.69, H 5.63,
27
26
5 1
N <0.05, S 6.97.
2
3
3.3.3 1-p-Toluonesulfonyloxy-2-octyl-9,10-anthraquinone (3c)
2
2
4
5
Following the procedure described in section 2.3 (Reaction IIa, Figure 1), 2b (336 mg, 1 mmol) and
TsCl (972 mg, 5.1 mmol) in CH Cl (70 mL) were mixed with a solution of NaOH (297 mg, 7.4 mmol)
2
2
2
0

1
2
3
4
5
6
7
8
9
0
and TBAB (1.64 g, 5.1 mmol) in deionized water (120 mL). After working-up of the reaction mixture
and recrystallization from CHCl /hexane 204 mg (0.42 mmol, 41.5%) of 3c were obtained (cf. Table
3
-
1
1). IR νmax/cm : 2926, 2855, 1678, 1588, 1467, 1428, 1380, 1322, 1271, 1222, 1194, 1164, 1121,
1
1091, 1039, 891, 812, 767, 735, 714, 666. H NMR (400.13 MHz, CDCl ) δ: 8.23 (d, J = 8.0 Hz, 1H),
3
8.22 (m, 1H), 8.09 (m, 1H), 7.84 (d, J = 8.4 Hz, 2H), 7.75 (m, 2H), 7.65 (d, J = 8.0 Hz, 1H), 7.33 (d, J =
13
8.4 Hz, 2H), 2.60 (t, J = 7.8 Hz, 2H), 2.42 (s, 3H), 1.56 (m, 2H), 1.26 (m, 10H), 0.88 (t, J = 6.7 Hz, 3H). C
NMR (100.63 MHz, CDCl ) δ: 182.25, 181.98, 145.64, 145.43, 145.22, 135.47, 134.71, 134.09, 133.65,
3
133.49, 133.37, 132.46, 129.80, 128.70, 128.23, 127.31, 126.67, 126.16, 31.84, 30.57, 29.70, 29.46,
29.28, 29.18, 22.64, 21.68, 14.08. Anal. Calcd. for C H O S : C 71, H 6.16, N 0, S 6.54. Found: C
29
30
5 1
1
1
70.42, H 6.09, N <0.05, S 6.43.
1
3.3.4 1-p-Toluonesulfonyloxy-9,10-anthraquinone (3d)
1
1
1
1
1
1
1
1
2
2
2
2
3
4
5
6
7
8
9
0
1
2
Following the procedure described in section 2.3 (Reaction IIa, Figure 1), 1 (504 mg, 2.25 mmol) and
TsCl (2.20 g, 11.6 mmol) in CH Cl (180 mL) were mixed with a solution of NaOH (760 mg, 19 mmol)
2
2
and TBAB (3.75 g, 11.6 mmol) in deionized water (360 mL). After working-up of the reaction mixture
and recrystallization from CHCl /hexane 350 mg (0.93 mmol, 41.2%) of 3d were obtained (cf. Table
3
-
1
1). IR νmax/cm : 2961, 2927, 2878, 1725, 1674, 1588, 1495, 1443, 1376, 1313, 1276, 1173, 1093,
1
1043, 1005, 876, 840, 802, 746, 702, 662. H NMR (400.13 MHz, CDCl ) δ: 8.31 (dd, J = 7.9, 1.3 Hz,
3
1H), 8.24 (m, 1H), 8.17 (m, 1H), 7.88 (d, J = 8.4 Hz, 2H), 7.79 (m, 1H), 7.77 (m, 1H), 7.75 (t, J = 8.0 Hz,
1
3
1H), 7.55 (dd, J = 8.2, 1.3 Hz, 1H), 7.32 (d, J = 8.4 Hz, 2H), 2.40 (s, 3H). C NMR (100.63 MHz, CDCl ) δ:
3
182.18, 180.72, 147.76, 145.59, 135.56, 134.39, 134.38, 134.34, 133.85, 132.69, 132.38, 130.07,
129.70, 128.88, 127.37, 126.86, 126.58, 126.52, 21.68. Anal. Calcd. for C H O S : C 66.66, H 3.73, N
21
14
5 1
0, S 8.47. Found: C 65.35, H 3.73, N 0.124, S 8.51.
2
2
3
4
3.4 General procedure for the tosylation of 1,4-dihydroxy-9,10-anthraquinone (1’) and 1,4-
dihydroxy-2-alkyl-9,10-anthraquinones (2a’-c’) (Reaction IIb)
2
1

1
2
3
4
5
6
7
8
9
0
1
It is worth mentioning that different from 1-hydroxy-9,10-anthraquinone (1) and its 2-alkyl
derivatives (2a-2c), tosylation of the 1,4-dihydroxy-9,10-anthraquinone counterparts (1’, 2a’-2c’) did
1
neither require a phase catalyst nor column chromatography to obtain H NMR pure compounds.
Typically, 1,4-dihydroxy-9,10-anthraquinone (1’) or 1,4-dihydroxy-2-alkyl-9,10-anthraquinone (2a’-c’)
(1 mmol) was dissolved in acetonitrile (ACN) (9 mL) that contained triethylamine (Et N) (1.5 mL, 11.1
3
mmol). After adding p-toluenesulfonyl chloride (TsCl) (2.5 mmol) the mixture was refluxed under
stirring for 5h (1’) or overnight (2a’-c’). Monitoring of the reaction was accomplished by TLC (SiO2,
CH Cl ). After evaporation of the solvent, the solid product was re-dissolved in dichloromethane. The
2
2
obtained organic phase was washed with deionized water several times and dried over anhydrous
Na SO . Following removal of solvent, the obtained product was recrystallized (CHCl /hexane),
1
1
2
4
3
washed with hexane and dried.
1
2
3.4.1 1,4-Bis(p-toluonesulfonyloxy)-2-butyl-9,10-anthraquinone (3a’)
1
1
1
1
1
1
1
2
2
2
2
3
4
5
6
7
8
9
0
1
2
3
Following the procedure described in section 2.4 (Reaction IIb, Figure 1), 2a’ (296 mg, 1 mmol) was
reacted with TsCl (480 mg, 2.5 mmol) in the presence of Et N (1.5 mL, 11.1 mmol). After working-up
3
of the reaction mixture and recrystallization from CHCl /hexane 369 mg (0.61 mmol, 61.1%) of 3a’
3
-
1
was obtained (cf. Table 1). IR νmax/cm : 2957, 2930, 2863, 1683, 1594, 1494, 1445, 1374, 1313, 1256,
1
1166, 1090, 1021, 929, 898, 814, 755, 665, 620. H NMR (400.13 MHz, CDCl ) δ: 8.03 (m), 7.96 (m),
3
7.86 (d, J = 8.3 Hz, 2H), 7.81 (d, J = 8.3 Hz, 2H), 7.71 (m, 2H), 7.39 (s), 7.33 (d, J = 8.3 Hz, 2H), 7.31 (d, J
= 8.3 Hz, 2H), 2.56 (t, J = 7.8 Hz, 2H), 2.43 (s, 3H), 2.40 (s, 3H), 1.46 (m, 2H), 1.27 (m, 2H), 0.89 (t, J =
1
3
7.2 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 181.95, 180.15, 146.68, 145.81, 145.77, 145.75, 143.66,
3
133.77, 133.37, 132.99, 132.40, 130.87, 130.34, 129.92, 129.74, 128.96, 128.67, 126.72, 126.69,
125.88, 31.34, 30.03, 22.41, 21.70, 21.68, 13.73. Anal. Calcd. for C H O S : C 63.56, H 4.67, N 0, S
32
28
8 2
10.61. Found: C 63.17, H 4.69, N <0.05, S 10.61.
2
4
3.4.2 1,4-Bis(p-toluonesulfonyloxy)-2-hexyl-9,10-anthraquinone (3b’)
2
2

1
2
3
4
5
6
7
8
9
0
1
2
Following the procedure described in section 2.4 (Reaction IIb, Figure 1), 2b’ (324 mg, 1 mmol) was
reacted with TsCl (480 mg, 2.5 mmol) in the presence of Et N (1.5 mL, 11.1 mmol). After working-up
3
of the reaction mixture and recrystallization from CHCl /hexane 407 mg (0.64 mmol, 64.4%) of 3b’
3
-
1
was obtained (cf. Table 1). IR νmax/cm : 2951, 2918, 2857, 1682, 1594, 1494, 1446, 1378, 1319, 1258,
1
1168, 1090, 1045, 930, 895, 814, 741, 698, 662, 608. H NMR (400.13 MHz, CDCl ) δ: 8.03 (m), 7.96
3
(m), 7.85 (d, J = 8.3 Hz, 2H), 7.81 (d, J = 8.3 Hz, 2H), 7.71 (m, 2H), 7.39 (s), 7.33 (d, 8.3 Hz, 2H), 7.31
(d, J = 8.3 Hz, 2H), 2.54 (t, J = 7.9 Hz, 2H), 2.42 (s, 3H), 2.39 (s, 3H), 1.47 (m, 2H), 1.24 (m, 4H), 1.28
1
3
(m, 2H), 0.89 (t, J = 6.5 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 181.94, 180.15, 146.71, 145.81,
3
145.75, 145.74, 143.65, 133.76, 133.71, 133.37, 133.01, 132.40, 130.85, 130.36, 129.91, 129.76,
129.73, 128.95, 128.67, 126.71, 126.67, 125.86, 31.44, 30.32, 29.20, 28.98, 22.49, 21.70, 21.68,
14.02. Anal. Calcd. for C H O S : C 64.54, H 5.1, N 0, S 10.14. Found: C 64.24, H 5.07, N <0.05, S
1
1
1
34
32
8 2
10.14.
1
3
3.4.3 1,4-Bis(p-toluonesulfonyloxy)-2-octyl-9,10-anthraquinone (3c’)
1
1
1
1
1
1
2
2
2
2
2
4
5
6
7
8
9
0
1
2
3
4
Following the procedure described in section 2.4 (Reaction IIb, Figure 1), 2c’ (352 mg, 1 mmol) was
reacted with TsCl (0.48 g, 2.5 mmol) in the presence of Et N (1.5 mL, 11.1 mmol). After working-up
3
of the reaction mixture and recrystallization from CHCl /hexane 220 mg (0.33 mmol, 33.3%) of 3c’
3
-
1
was obtained (cf. Table 1). IR νmax/cm : 2928, 2851, 1682, 1594, 1494, 1447, 1379, 1319, 1257, 1169,
1
1090, 1020, 930, 896, 813, 741, 699, 664, 608. H NMR (400.13 MHz, CDCl ) δ: 8.03 (m), 7.96 (m),
3
7.85 (d, J = 8.3 Hz, 2H), 7.81 (d, J = 8.3 Hz, 2H), 7.71 (m, 2H), 7.39 (s), 7.33 (d, J = 8.3 Hz, 2H), 7.31 (d,
J = 8.3 Hz, 2H), 2.54 (t, J = 7.9 Hz, 2H), 2.43 (s, 3H), 2.39 (s, 3H), 1.47 (m, 2H), 1.29 (m, 2H), 1.25 (m,
1
3
8H), 0.90 (t, J = 6.9 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 181.95, 180.16, 146.73, 145.82, 145.75,
3
143.64, 133.76, 133.72, 133.38, 133.02, 132.41, 130.87, 130.32, 129.92, 129.73, 128.96, 128.61,
126.71, 126.67, 125.86, 31.83, 30.34, 29.35, 29.28, 29.25, 29.17, 22.64, 21.70, 21.68, 14.09. Anal.
Calcd. for C H O S : C 65.43, H 5.49, N 0, S 9.7. Found: C 64.98, H 5.42, N <0.05, S 9.72.
36
36
8 2
2
5
3.4.4 1,4-Bis(p-toluonesulfonyloxy)-9,10-anthraquinone (3d’)
2
3

1
2
3
4
5
6
7
8
9
Following the procedure described in section 2.4 (Reaction IIb, Figure 1), 1’ (2.5 g, 10.4 mmol) was
reacted with TsCl (4.8 g, 25.2 mmol) in the presence of Et N (10 mL, 74.1 mmol). After working-up of
3
the reaction mixture and recrystallization from CHCl /hexane 4.215 g (7.7 mmol, 73.8%) of 3d’ was
3
-
1
obtained (cf. Table 1). IR νmax/cm : 3073, 1678, 1583, 1492, 1451, 1403, 1347, 1306, 1260, 1218,
1
1169, 1089, 1021, 925, 896, 867, 810, 781, 744, 705, 673, 617. H NMR (400.13 MHz, CDCl ) δ: 8.02
3
13
(m, 2H), 7.84 (d, J = 8.2 Hz, 4H), 7.72 (m, 2H), 7.50 (s, 2H), 7.32 (d, J = 8.2 Hz, 4H), 2.40 (s, 6H). C
NMR (100.63 MHz, CDCl ) δ: 180.36, 146.10, 145.89, 133.94, 133.36, 132.28, 130.53, 129.82, 128.89,
3
128.37, 126.80, 21.69. Anal. Calcd. for C H O S : C 61.3, H 3.67, N 0, S 11.69. Found: C 61.2, H 3.62,
28
20
8 2
N <0.05, S 11.88.
1
1
1
1
0
1
2
3
3.5 General procedure for butylamination of 1-p-toluonesulfonyloxy-2-alkyl-9,10-
anthraquinones (3a-c), 1-p-toluonesulfonyloxy-9,10-anthraquinone (3d), 1,4-bis(p-
toluonesulfonyloxy)-2-alkyl-9,10-anthraquinones (3a’-c’) and 1,4- bis(p-toluonesulfonyloxy)-
9,10-anthraquinone (3d’) (Reaction III, Figure 1)
1
1
1
1
1
1
2
4
5
6
7
8
9
0
A large excess (400-1000 mol eq.) of n-butylamine was added to a solution of the respective
tosylated compound in pyridine and the reaction mixture was kept at 50°C for 2-5 days to ensure
completion of the reaction which was monitored by TLC (SiO ; heptane-ethylacetate ratio 6:1). After
2
cooling, pyridine was removed by co-evaporation with toluene. Column chromatography was then
performed (SiO , heptane-to-ethylacetate ratio 6:1), the first eluting red (for educts 3a-d) and blue
2
fraction (for educts 3a’-d’), respectively, was collected. After evaporation of solvent, the obtained
solids were recrystallized from absolute ethanol.
2
1
3.5.1 1-Butylamino-2-butyl-9,10-anthraquinone (4a)
2
2
2
2
2
3
4
5
Following the procedure described in section 2.5, 3a (867 mg, 2 mmol) and n-butylamine (79.1mL,
800 mmol) were co-dissolved in pyridine (70 mL). The mixture was kept at 50°C for two days. After
work-up and recrystallization 602 mg (1.80 mmol, 85.4%) of 4a was obtained (cf. Table 1). UV
-
4
-1
-1
-1
(iPrOH) λmax (ε x 10 , M .cm ): 509 (0.58) nm. IR ν /cm : 3073, 2954, 2929, 2871, 1663, 1624,
max
2
4

1
1
2
3
4
5
6
7
8
1522, 1455, 1351, 1303, 1258, 1177, 1103, 1049, 1009, 965, 897, 841, 789, 716, 670. H NMR
(400.13 MHz, CDCl ) δ: 9.67 (br.s, 1H), 8.31 (dd, J = 7.6, 1.5 Hz, 1H), 8.22 (dd, J = 7.6, 1.6 Hz, 1H), 7.75
3
(ddd, J = 7.6, 7.6, 1.5 Hz, 1H), 7.69 (ddd, J = 7.6, 7.6, 1.5 Hz, 1H), 7.68 (d, J = 7.6 Hz, 1H), 7.41 (d, J =
7.6 Hz, 1H), 3.39 (t, J = 7.2 Hz, 2H), 2.81 (t, J = 7.8 Hz, 2H), 1.69 (m, 2H), 1.64 (m, 2H), 1.48 (m, 2H),
13
1.40 (m, 2H), 0.97 (t, J = 7.4 Hz, 3H), 0.96 (t, J = 7.3 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 185.72,
3
183.63, 153.44, 138.48, 136.78, 135.40, 133.79, 132.97, 132.94, 132.83, 127.01, 126.45, 118.18,
116.78, 47.44, 34.16, 33.27, 31.84, 22.63, 20.20, 13.93, 13.84. Anal. Calcd. for C H O N : C 78.77, H
22
25
2
1
7.51, N 4.18, S 0. Found: C 78.66, H 7.7, N 4.31, S <0.02.
9
3.5.2 1-Butylamino-2-hexyl-9,10-anthraquinone (4b)
1
1
1
1
1
1
1
1
1
1
2
2
0
1
2
3
4
5
6
7
8
9
0
1
Following the procedure described in section 2.5, 3b (461.5 mg, 1 mmol) and n-butylamine (39.5 mL,
400 mmol) were co-dissolved in pyridine (40 mL). The mixture was kept at 50°C for two days. After
work-up and recrystallization 311.6 mg (0.86 mmol, 85.8%) of 4b was obtained (cf. Table 1). UV
-
4
-1
-1
-1
(iPrOH) λmax (ε x 10 , M .cm ): 508 (0.60) nm. IR ν /cm : 3071, 2952, 2922, 2851, 1664, 1628,
max
1
1578, 1507, 1461, 1353, 1304, 1268, 1181, 1039, 976, 904, 850, 773, 710. H NMR (400.13 MHz,
CDCl ) δ: 9.69 (br.s, 1H), 8.31 (dd, J = 7.6, 1.4 Hz, 1H), 8.23 (dd, J = 7.6, 1.4 Hz, 1H), 7.75 (ddd, J = 7.6,
3
7.6, 1.4 Hz, 1H), 7.70 (ddd, J = 7.6, 7.6, 1.4 Hz, 1H), 7.69 (d, J = 7.8 Hz, 1H), 7.41 (d, J = 7.8 Hz, 1H),
3.39 (t, J = 7.2 Hz, 2H), 2.80 (t, J = 7.8 Hz, 2H), 1.70 (m, 2H), 1.65 (m, 2H), 1.48 (m, 2H), 1.37 (m, 2H),
1
3
1.33 (m, 4H), 0.97 (t, J = 7.4 Hz, 3H), 0.89 (t, J = 6.9 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 185.74,
3
183.62, 153.31, 138.59, 136.79, 135.40, 133.81, 132.96, 132.84, 127.03, 126.47, 118.26, 116.83,
47.46, 34.48, 33.24, 31.68, 29.71, 29.23, 22.59, 20.21, 14.03, 13.84. Anal. Calcd. for C H O N : C
24
29
2
1
79.3, H 8.04, N 3.85, S 0. Found: C 79.05, H 8.16, N 4.01, S <0.02.
2
2
3.5.3 1-Butylamino-2-octyl-9,10-anthraquinone (4c)
2
2
2
3
4
5
Following the procedure described in section 2.5, 3c (155 mg, 0.32 mmol) and n-butylamine (12.5
mL, 126.5 mmol) were co-dissolved in pyridine (15 mL). The mixture was kept at 50°C for two days.
After work-up and recrystallization 99 mg (0.25 mmol, 80.0%) of 4c was obtained (cf. Table 1). UV
2
5

-
4
-1
-1
-1
1
2
3
4
5
6
7
8
9
0
(iPrOH) λmax (ε x 10 , M .cm ): 508 (0.62) nm. IR ν /cm : 3072, 2953, 2927, 2848, 1667, 1628,
max
1
1593, 1522, 1464, 1350, 1302, 1263, 1232, 1171, 1098, 989, 970, 911, 839, 792, 736, 710, 670. H
NMR (400.13 MHz, CDCl ) δ: 9.69 (br.s, 1H), 8.31 (dd, J = 7.6, 1.4 Hz, 1H), 8.22 (dd, J = 7.6, 1.4 Hz,
3
1H), 7.75 (ddd, J = 7.6, 1.4 Hz, 1H), 7.70 (ddd, J = 7.6, 1.4 Hz, 1H), 7.69 (d, J = 7.6 Hz, 1H), 7.41 (d, J =
7.6 Hz, 1H), 3.39 (t, J = 7.2 Hz, 2H), 2.80 (t, J = 7.8 Hz, 2H), 1.70 (m, 2H), 1.65 (m, 2H), 1.48 (m, 2H),
13
1.35 (m, 2H), 1.30 (m, 6H), 1.28 (m, 2H), 0.97 (t, J = 7.4 Hz, 3H), 0.88 (t, J = 6.8 Hz, 3H). C NMR
(100.63 MHz, CDCl ) δ: 185.74, 183.61, 153.28, 138.60, 136.80, 135.39, 133.81, 132.97, 132.84,
3
127.03, 126.47, 118.28, 116.84, 47.47, 34.47, 33.23, 31.83, 29.75, 29.56, 29.44, 29.23, 22.65, 20.21,
14.07, 13.84. Anal. Calcd. for C H O N : C 79.76, H 8.49, N 3.58, S 0. Found: C 79.71, H 8.65, N 3.77,
2
6
33
2
1
1
1
S <0.02.
1
3.5.4 1-Butylamino-9,10-anthraquinone (4d)
1
1
1
1
1
1
1
1
2
2
2
2
2
3
4
5
6
7
8
9
0
1
2
3
Following the procedure described in section 2.5, 3d (378 mg, 1 mmol) and n-butylamine (39.5 mL,
400 mmol) were co-dissolved in pyridine (50 mL). The mixture was kept at 50°C for three days. After
work-up and recrystallization 198.6 mg (0.71 mmol, 71.2%) of 4d was obtained (cf. Table 1). UV
-
4
-1
-1
-1
(iPrOH) λmax (ε x 10 , M .cm ): 508 (0.66) nm. IR ν /cm : 3258, 3079, 2957, 2927, 2855, 1662,
max
1627, 1590, 1505, 1472, 1405, 1362, 1302, 1272, 1161, 1136, 1067, 994, 906, 869, 827, 800, 733,
1
705, 660, 606. H NMR (400.13 MHz, CDCl ) δ: 9.75 (br.s, 1H), 8.28 (dd, J = 7.6 Hz, 1H), 8.24 (dd, J =
3
7.6, 1.4 Hz, 1H), 7.76 (ddd, J = 7.4, 7.4, 1.4 Hz, 1H), 7.70 (ddd, J = 7.4, 7.4, 1.4 Hz, 1H), 7.59 (dd, J =
7.4, 1.0 Hz, 1H), 7.53 (t, J = 8.0 Hz, 1H), 7.06 (dd, J = 8.4, 1.0 Hz, 1H), 3.35 (td, J = 7.0, 5.3 Hz, 2H), 1.76
1
3
(m, 2H), 1.54 (m, 2H), 1.01 (t, J = 7.4 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 184.96, 183.86, 151.86,
3
135.25, 135.09, 134.69, 133.89, 133.07, 132.84, 126.69, 126.63, 117.86, 115.49, 112.85, 42.68,
31.20, 20.36, 13.83. Anal. Calcd. for C H O N : C 77.4, H 6.13, N 5.01. Found: C 77.33, H 6.08, N
18
17
2
1
4.99.
2
4
3.5.5 1,4-Bis(butylamino)-2-butyl-9,10-anthraquinone (4a’)
2
6

1
2
3
4
5
6
7
8
9
0
1
2
Following the procedure described in section 2.5, 3a’ (302 mg, 0.5 mmol) and n-butylamine (52.6
mL, 530 mmol) were co-dissolved in pyridine (50 mL). The mixture was kept at 50°C for five days.
After work-up and recrystallization 128.3 mg (0.32 mmol, 63.2%) of 4a’ was obtained (cf. Table 1).
-
4
-1
-1
-1
UV (iPrOH) λmax (ε x 10 , M .cm ): 597 (1.65), 643 (1.61) nm. IR ν /cm : 3064, 2954, 2930, 2867,
max
1
1610, 1558, 1455, 1362, 1257, 1187, 1090, 1050, 1023, 955, 904, 864, 823, 787, 728, 664, 618. H
NMR (400.13 MHz, CDCl ) δ: 10.71 (br.s, J = 5.4 Hz, 1H), 10.34 (br.s, 1H), 8.34 (m, 1H), 8.31 (m, 1H),
3
7.67 (m, 2H), 7.02 (s, 1H), 3.40 (td, J = 7.0, 5.4 Hz, 2H), 3.32 (t, J = 7.1 Hz, 2H), 2.82 (t, J = 7.7 Hz, 2H),
1.76 (m, 2H), 1.68 (m, 4H), 1.54 (m, 2H), 1.44 (m, 4H), 1.01 (t, J = 7.4 Hz, 3H), 0.98 (t, J = 7.4 Hz, 3H),
1
3
0.95 (t, J = 7.4 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 184.07, 182.07, 148.03, 147.70, 144.47,
3
1
1
1
134.64, 134.57, 132.29, 131.88, 126.41, 125.80, 123.02, 115.36, 108.85, 48.07, 42.57, 34.43, 33.45,
31.81, 31.68, 22.70, 20.39, 20.29, 13.94, 13.87. Anal. Calcd. for C H O N : C 76.81, H 8.43, N 6.89.
26
34
2
2
Found: C 76.57, H 8.48, N 6.87.
1
3
3.5.6 1,4-Bis(butylamino)-2-hexyl-9,10-anthraquinone (4b’)
1
1
1
1
1
1
2
2
2
2
2
2
4
5
6
7
8
9
0
1
2
3
4
5
Following the procedure described in section 2.5, 3b’ (316 mg, 0.5 mmol) and n-butylamine (52.6
mL, 530 mmol) was co-dissolved in pyridine (50 mL). The mixture was kept at 50°C for five days.
After work-up and recrystallization 130 mg (0.30 mmol, 59.9%) of 4b’ was obtained (cf. Table 1). UV
-
4
-1
-1
-1
(iPrOH) λmax (ε x 10 , M .cm ): 597 (1.25), 643 (1.21) nm. IR ν /cm : 3065, 2956, 2923, 2872, 1742,
max
1
1606, 1558, 1504, 1456, 1377, 1257, 1185, 1132, 1105, 1017, 874, 798, 763, 723, 665, 638. H NMR
(400.13 MHz, CDCl ) δ: 10.71 (br.t, J = 5.4 Hz, 1H), 10.35 (br.s, 1H), 8.34 (m, 1H), 8.31 (m, 1H), 7.67
3
(m, 2H), 7.02 (s, 1H), 3.40 (td, J = 7.0, 5.4 Hz, 2H), 3.32 (t, J = 7.2 Hz, 2H), 2.81 (t, J = 7.8 Hz, 2H), 1.76
(m, 2H), 1.68 (m, 4H), 1.54 (m, 2H), 1.45 (m, 4H), 1.34 (m, 4H), 1.01 (t, J = 7.4 Hz, 3H), 0.95 (t, J = 7.4
1
3
Hz, 3H), 0.90 (t, J = 7.1 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 184.05, 182.07, 148.03, 147.70,
3
144.49, 134.65, 134.58, 132.29, 131.88, 126.41, 125.80, 123.01, 115.35, 108.85, 48.05, 42.56, 34.75,
33.47, 31.69, 31.69, 29.67, 29.30, 22.61, 20.39, 20.30, 14.04, 13.87. Anal. Calcd. for C H O N : C
28
38
2
2
77.38, H 8.81, N 6.45. Found: C 77.34, H 9.04, N 6.44.
2
7

1
3.5.7 1,4-Bis(butylamino)-2-octyl-9,10-anthraquinone (4c’)
2
3
4
5
6
7
8
9
0
1
2
3
Following the procedure described in section 2.5, 3c’ (259 mg, 0.39 mmol) and of n-butylamine (39.5
mL, 400 mmol) was co-dissolved in pyridine (40 mL). The mixture was kept at 50°C for five days.
After work-up and recrystallization 123.1 mg (0.27 mmol, 67.9%) of 4c’ was obtained (cf. Table 1).
-
4
-1
-1
-1
UV (iPrOH) λmax (ε x 10 , M .cm ): 597 (1.44), 643 (1.40) nm. IR ν /cm : 3074, 2957, 2922, 2870,
max
1
1739, 1606, 1567, 1504, 1455, 1380, 1307, 1272, 1198, 1107, 1017, 877, 798, 766, 724, 665. H NMR
(400.13 MHz, CDCl ) δ: 10.71 (br.t, J = 5.3 Hz, 1H), 10.35 (br.s, 1H), 8.34 (m, 1H), 8.31 (m, 1H), 7.67
3
(m, 2H), 7.02 (s, 1H), 3.40 (td, J =,7.0, 5.3 Hz, 2H), 3.32 (t, 7.2 Hz, 2H), 2.80 (t, 7.8 Hz, 2H), 1.76 (m,
2H), 1.68 (m, 4H), 1.54 (m, 2H), 1.46 (m, 2H), 1.40 (m, 2H), 1.37 (m, 2H), 1.29 (m, 4H), 1.28 (m, 2h),
1
3
1
1
1
1
1.01 (t, 7.4 Hz, 3H), 0.95 (t, 7.4 Hz, 3H), 0.88 (t, 7.0 Hz, 3H). C NMR (100.63 MHz, CDCl ) δ: 184.05,
3
182.07, 148.03, 147.70, 144.49, 134.65, 134.58, 132.29, 131.88, 126.41, 125.80, 123.02, 115.33,
108.85, 48.05, 42.56, 34.75, 33.47, 31.84, 31.69, 29.73, 29.62, 29.45, 29.25, 22.64, 20.39, 20.30,
14.07, 13.87. Anal. Calcd. for C H O N : C 77.88, H 9.15, N 6.05. Found: C 77.73, H 9.27, N 6.08.
30
42
2
2
1
4
3.5.8 1,4-Bis(butylamino)-9,10-anthraquinone (4d’)
1
1
1
1
1
2
2
2
2
5
6
7
8
9
0
1
2
3
Following the procedure described in section 2.5, 3d’ (548 mg, 1 mmol) and of n-butylamine (98.9
mL, 1 mol) was co-dissolved in pyridine (100 mL). The mixture was kept at 50°C for five days. After
work-up and recrystallization 258.2 mg (0.74 mmol, 73.7%) of 4d’ was obtained (cf. Table 1). UV
-
4
-1
-1
-1
(iPrOH) λmax (ε x 10 , M .cm ): 596 (0.78), 644 (0.96) nm. IR ν /cm : 3072, 2961, 2928, 2855, 1717,
max
1641, 1552, 1518, 1464, 1393, 1343, 1270, 1163, 1134, 1055, 1017, 988, 949, 849, 797, 726, 666,
1
624. H NMR (400.13 MHz, CDCl ) δ: 10.82 (br.t, J =5.5 Hz, 2H), 8.35 (m, 2H), 7.68 (m, 2H), 7.24 (s,
3
13
2H), 3.41 (td, J = 7.0, 5.5 Hz, 4H), 1.76 (m, 4H), 1.53 (m, 4H), 1.00 (t, J = 7.4 Hz, 6H). C NMR (100.63
MHz, CDCl ) δ: 182.24, 146.28, 134.57, 131.88, 125.98, 123.57, 109.69, 42.61, 31.76, 20.36, 13.83.
3
Anal. Calcd. for C H O N : C 75.4, H 7.48, N 7.99. Found: C 75, H 7.76, N 7.73.
22
26
2
2
2
4
3.6 X-ray analysis
2
8

1
2
3
4
5
6
7
8
9
0
1
2
3
X-ray diffraction analysis of compound 4a’ was performed using a Bruker D8 Venture diffractometer
equipped with multilayer monochromator, Mo K/α INCOATEC micro focus sealed tube, Oxford
cooling system. Structure elucidation was accomplished by direct methods and refined by full-matrix
least-squares techniques. Non-hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were inserted at calculated positions and refined with riding model.
The following software was used: Bruker SAINT software package [35] using a narrow-frame
algorithm for frame integration, SADABS [36] for absorption correction, OLEX2 [37] for structure
solution, refinement, molecular diagrams and graphical user-interface, Shelxle [38] for refinement
and graphical user-interface SHELXS-2015 [39] for structure solution, SHELXL-2015 [39] for
refinement, Platon [40] for symmetry check. Experimental data, CCDC-Code, crystal data, data
1
1
1
1
collection
parameters
and
structure
refinement
details
(Available
online:
http://www.ccdc.cam.ac.uk/conts/retrieving.html) can be found in the Supplementary Information
section.
1
4
3.7 Computational details
1
1
1
5
6
7
All calculations were performed using the Gaussian 09 software package (Wallingford, CT, USA)
available at the Vienna Scientific Cluster (VSC). Figures were created with Avogadro 1.20, an open-
source molecular builder and visualization tool [41].
1
1
2
2
2
8
9
0
1
2
The structures of 1 ,1’, 2a, 2a’,3a, 3a’, 4a and 4a’ were subjected to geometry optimisation based on
the density functional theory (DFT) with the B3LYP functional and the 6-311++g(d,p) basis set. In
addition, the integration grid was set to ‘ultrafine’ and Grimme’s D3 dispersion correction was
employed. Frequency calculations with the optimized structures at the same level of theory were
used to guarantee the absence of imaginary frequencies.
2
2
2
3
4
5
Isopropanol as solvent was modelled with the Polarisable Continuum Model. The solvent was
included in all the calculations except for the one used to compare the simulated structure of 4a’
with the X-ray data.
2
9