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

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

Reference:

DYPI 107991

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-9,10anthraquinone dyes for improved supercritical carbon dioxide dyeing, Dyes and Pigments (2019), doi: https://doi.org/10.1016/j.dyepig.2019.107991. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

1

Facile synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-anthraquinone dyes for

2

improved supercritical carbon dioxide dyeing

3

Julien Jaxela,b, Hassan Amera,c, Markus Bachera, Alexander Rollerd, Matthias Guggenbergera, Nele

4

Sophie Zwirchmayra, Christian Hansmannb, Falk Liebnera,b,e* a

5

Institute for Chemistry of Renewable Resources, University of Natural Resources and Life Science Vienna,

6

Konrad-Lorenz-Straße 24, 3430 Tulln an der Donau, Austria b

7

Wood K plus - Competence Center for Wood Composites & Wood Chemistry Ltd., Altenberger Straße 69, A-

8 9

4040 Linz, Austria c

Department of Natural and Microbial Products Chemistry, National Research Centre, P.O. 12622, Dokki, Giza,

10 11

Egypt d

X-Ray Structure Analysis Center, Faculty of Chemistry, University of Vienna, Währingerstrasse 42, 1090

12

Vienna, Austria e

13 14

Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal *Falk Liebner: [email protected]

15

Abstract

16

Supercritical carbon dioxide (scCO2) has recently been conquering both material sciences and

17

process engineering owing to its intriguing properties like high diffusivity and tuneable

18

(de)solubilizing performance. However, except for impregnation with biocidal preservatives,

19

utilization of scCO2 for modification of wood including dyeing has been hitherto less explored.

20

Therefore, we recently proposed a green wood dyeing approach that relies on the excellent carrier

21

medium properties of CO2 for non-polar disperse dyes in supercritical conditions and their reversion

22

when leaving the supercritical state. However, using a common disperse dye of the 9,10-

23

anthraquinone family (Disperse Blue, DB-134) without the addition of co-solvent, only a moderate

24

colour change was obtained for the interior of small wood cuboids (1 cm x 1 cm x 2 cm) even after

25

extensive variation of scCO2 process conditions. Insufficient solubility of the dye in scCO2 was

26

assumed to be a major hindrance for homogeneous wood dyeing. Therefore, we synthesized a 1

1

variety of 1-n-butylamino- and 1,4-bis(n-butylamino)-9,10-anthraquinone derivatives carrying

2

different alkyl moieties in 2-position, which was confirmed to improve scCO2 solubility. Instead of a

3

previously reported seven-step synthesis affording moderate yields only (60% on average), we

4

propose an alternate much simpler synthesis comprising of Marschalk alkylation (2-position) and a

5

sequence of tosylation and n-alkylamination (1-position). The latter proved to pave way to a wide

6

variety of colours and disperse dyes of improved solubility in scCO2. Moreover, all products were

7

characterized by various techniques including liquid-state 1H and 13C NMR and X-ray crystallography.

8

Complementing X-ray diffraction, quantum-mechanical simulations were performed to predict or

9

confirm conformation and colour of selected compounds.

10

Keywords

11

Supercritical carbon dioxide dyeing, anthraquinone disperse dyes, colouring of massive wood,

12

Marschalk alkylation, alkylamination of 1-hydroxy and 1,4-dihydroxyanthraquinone derivatives

13

1.

Introduction

14

Dyeing of wood is still a vivid field of research and development in high-end wood

15

processing. This applies in particular for the manufacture of massive wood furniture which currently

16

experiences a renaissance in Europe. Extending the ranges of colours and of possibly harmless dyes

17

is therefore a major goal of both manufacturers and distributors to satisfy the current demands of

18

customers. Aiming at both adaption of massive wood colouring towards new dyes and development

19

of more efficient dyeing approaches in terms of required time, homogeneity and environmental

20

compatibility, supercritical carbon dioxide (scCO2) was recently proposed as green carrier medium

21

for that purpose [1, 2]. Carbon dioxide in the supercritical state is indeed an appealing solvent for

22

dyeing owing to its high dissolution power and diffusivity, abundance, low cost, recyclability,

23

inertness, incombustibility and non-toxicity. Furthermore, its low critical point (31.2°C, 7.38 MPa [1])

24

renders the process less challenging in terms of equipment demands compared to other supercritical

25

fluids. Considering these intriguing properties, it is rather surprising that scCO2 has hitherto not yet 2

1

established in wood colouring even though its utilization for wood modification reaches back to the

2

early days of supercritical technologies, i.e. the mid-80s of the previous century. Impregnation of

3

wood with biocides [3-9] as one of the few intensively researched applications has even succeeded

4

upscaling to an industrial process [10]. Hydrophobization of wood for outdoor applications, such as

5

by acetylation [11] or impregnation with polysiloxanes [12, 13] is another modification approach

6

that was also demonstrated to benefit from the intriguing properties of scCO2 as a carrier medium.

7

However, similar as with a series of other scCO2 applications, scaling-up and implementation into an

8

industrial process has here not been accomplished yet, presumably in the first line due to the high

9

investment cost of the required high-pressure equipment.

10

The excellent solvation power for lipophilic compounds, such as for disperse dyes used in

11

massive wood colouring, is probably one of the biggest assets of scCO2. While the former is

12

contributed by liquid-like densities, high diffusion coefficients and low viscosities – both comparable

13

to that of gases – enable fast diffusion of solubilised compounds. Since both solvent power and

14

diffusivity can be easily tuned by variation of pressure and temperature, a wide range of process

15

conditions can be easily established.

16

Dyeing of polyester fibers using scCO2 is an environmental-friendly process that has been

17

established on industrial scale, such as for colouring of poly(ethylene terephthalate) (PET). Main

18

advantages of using scCO2 as carrier medium include i) circumvention of high temperatures owing to

19

the plasticizing effect of scCO2 facilitating dye uptake at moderate temperatures [14, 15], ii)

20

improved separation and recovery of unreacted dye as accomplished by decreasing pressure at the

21

end of the scCO2 dyeing procedure [16, 17] and iii) excellent recycling rates of both CO2 (up to 95%)

22

and dyes. These advantages render scCO2 dyeing more efficient from the economic point of view

23

compared to the still widely used hot water process [17].

24

Nevertheless, strict control of process parameters is required to obtain satisfying results in

25

scCO2 dyeing. Solubility of the respective disperse dyes in scCO2 is one of the most critical issues in

26

this regard [17]. Next to its molecular structure, solubility is strongly dependent on both pressure 3

1

and temperature. While disperse dyes feature moderate solubility only in the early supercritical

2

state, i.e. at comparatively mild temperature and pressure, increase of both temperature and/or

3

pressure typically improves solubility (e.g. for Disperse Blue 134: y = 1.2 x 10-6 molDisperse Blue 134.mol(CO2

4

+ Disperse Blue 134)

5

at 20.0 MPa and 80°C [18]). Considering industrial scale dyeing of massive wood this implicates the

6

necessity of higher one-off investment in high pressure and temperature resistant equipment and

7

acceptance of higher energy running costs.

-1

at 10.0 MPa and 50°C compared to 67.7 x 10-6 molDisperse Blue 134.mol(CO2 + Disperse Blue 134)-1

8

Besides increase of pressure and temperature, addition of a co-solvent is another measure

9

to increase the solubility of low-molecular compounds in scCO2 such as disperse dyes. Acetone,

10

ethanol and methanol are probably the most frequently used co-solvents in scCO2 processes,

11

including extraction of coffee, tea, herbs and other natural products to obtain fragrances, flavour,

12

bioactive compounds or essential oils [19]. There is evidence that these co-solvents rather interact

13

with the respective organic target compounds than change the polarity of the extraction medium

14

[20]. If the process to be developed is intended to meet the standards of green chemistry in terms of

15

organic solvent-free processes, addition of co-solvents, even in small amounts (typically 3-10 mol%)

16

is a serious drawback.

17

On top of all there is consent that solubility of a certain organic compound in scCO2 is

18

governed by intrinsic physical properties. Low molecular weight, low content of polar groups and

19

strong hydrophobicity are prerequisites to render a compound soluble in scCO2. Particularly for

20

scCO2 dyeing approaches, high dye solubility is desired to improve the efficiency of dyeing and to

21

reduce the above-discussed costs for equipment, energy and co-solvents.

22

Addition of longer-chain alkylamino groups to 9,10-anthraquinone used in colouring of

23

polypropylene fibers has been demonstrated to increase lipophilicity and, hence, solubility in scCO2.

24

Part of these non-polar moieties were introduced in form of alkylamino groups to enhance final

25

colour strength, improve dyeability and colour fastness of propylene fabric. However, the effect

26

levelled-off at chain lengths of about 8 and started to decrease significantly for substituents 4

1

composed of more than 12 carbon atoms [21]. Specifically for anthraquinone dyes it is well known

2

that longer-chain alkyl substituents in ortho position of 1-hydroxy or 1-alkylamino groups have a

3

positive impact on the solubility of the respective dyes in scCO2 facilitating dyeing at milder

4

conditions [18, 22, 23]. Shamsipur and co-workers proposed the introduction of the lipophilic

5

aliphatic moieties by seven-step synthesis starting from 2-methyl-9,10-anthraquinone. Following

6

nitration using potassium nitrate and concentrated sulfuric acid, the obtained intermediate is

7

reduced with sodium sulfide in boiling ethanol to obtain 1-amino-2-methyl-9,10-anthraquinone.

8

Conversion of the amino group into a hydroxyl moiety is accomplished by nitrosation and

9

subsequent displacement of the diazonium salt by a hydroxyl group in a Sandmeyer-type reaction to

10

afford the respective 1-hydroxy-2-methyl-9,10-anthraquinone. The introduced hydroxyl group is

11

subsequently protected by methylation before the adjacent methyl group is converted into a

12

bromomethyl moiety by treatment with N-bromosuccinimide and dibenzoyl peroxide. Conversion of

13

the –CH2Br group into –CH2OR moieties (R = propyl, butyl, etc.) can be accomplished only after

14

deprotection (demethylation) of the hydroxyl group in 1-position using hydrobromic acid in glacial

15

acetic acid. The obtained 1-hydroxy-2-bromomethyl-9,10-anthraquinone reacts then easily with

16

different alcohols in the presence of potassium carbonate to the desired 2-alkoxymethyl derivatives.

17

However, despite the considerable synthesis efforts and variation of chain length, the colour of the

18

obtained family of 1-hydroxy-2-(1-alkyloxymethyl)-9,10-anthraquinones turned out to be limited to

19

the yellow to orange range.

20

Approximating solutions of the electronic Schrödinger equation is the fundamental approach

21

of ab initio quantum chemical simulation methods. These methods allow the prediction of a whole

22

array of atomic and molecular characteristics including molecular orbitals and spectroscopic

23

properties. Thereby just spatial coordinates of the studied system and its number of electrons is

24

required as input. For these reasons they are a vital tool for the characterization of small organic

25

molecules, such as the disperse dyes described in the present work. There are different

26

opportunities to obtain respective approximated solutions of the Schrödinger equation, with Density 5

1

Functional Theory (DFT) based approaches being among the most successful and popular ones. In

2

DFT, the energy of a system is described by its electron density expressed by a so called electron

3

density function. This is in contrast to the also very important Hartree-Fock method that relies on

4

modelling of each single electron individually [24, 25]. For the current work, calculations based on

5

density functional theory were employed to firstly optimize the geometries of the different products

6

synthesized and secondly to examine their spectroscopic properties in the UV-vis range.

7

In view of the elaborate synthesis approach towards anthraquinone dyes of improved scCO2

8

solubility, the current demands for massive wood furniture covering a wide gamut of colours and

9

taking into account the fact that native European wood is inherently yellowish to brownish, this

10

work targeted two goals. First Marschalk alkylation was explored as a hypothetically more

11

straightforward approach towards synthesis of 2-alkyl substituted 1-hydroxy-9,10-anthraquinone (1)

12

and 1,4-dihydroxy-9,10-anthraquinone (1’, quinizarin, Solvent Orange 86) featuring increased scCO2

13

solubility. Second, we attempted to achieve a broader colour variety in particular towards red and

14

even blue shades by replacing the respective OH groups of compound 1 and 1’ (Figure 1) by strongly

15

electron donating alkyl amino groups and, thus, benefiting from the expected extent of the

16

bathochromic shift [26].

17

6

1

2.

Results and discussion

2

Figure 1 shows the three-step approach towards the four groups of compounds synthesized

3

in this work, i.e. 1-hydroxy-2-alkyl-9,10-anthraquinones, 1,4-dihydroxy-2-alkyl-9,10-anthraquinones,

4

1-butylamino-2-alkyl-9,10-anthraquinones

5

Numbering, yields and selected properties in terms of colour and melting points of all compounds

6

have been compiled in Table 1.

and

1,4-bis(butylamino)-2-alkyl-9,10-anthraquinones.

7

In the first step of the employed reaction sequence (I, Figure 1), the educts 1 and 1’ were

8

subjected to Marschalk alkylation [27, 28]. In this reaction both 1-hydroxy-9,10-anthraquinone and

9

1,4-dihydroxy-9,10-anthraquinone are intermediary reduced by sodium dithionite to their respective

10

leuko forms. The latter undergoes then condensation with the respective aldehydes added to yield

11

the desired 2-alkylated 9,10-anthraquinones. Since the reaction was conducted in alkaline medium,

12

introduction of the alkyl substituent occurred selectively in C2 position which is in agreement with

13

the literature [29] and was confirmed by NMR spectroscopy. While the yields of the 1-hydroxy-2-

14

alkyl-9,10-anthraquinone compounds (2a-c) were between 27.5 and 63.6% only, they were distinctly

15

higher for the 1,4-dihydroxy-9,10-anthraquinone counterparts (71.9-83%).

16 17

7

O

OH

O

OH

I O 1

1: R = H 1': R1 = OH

R

R

1

O 1

2

2a: R = H; R = But 2b: R1 = H; R2 = Hex 2c: R1 = H; R2 = Oct

R

2

IIa/IIb

1

O

OTs R

R

O 1

2

3a': R1 = OTs; R2 = But 3b': R1 = OTs; R2 = Hex 3c': R1 = OTs; R2 = Oct 3d': R1 = OTs; R2 = H

1

2

2a': R = OH; R = But 2b': R1 = OH; R2 = Hex 2c': R1 = OH; R2 = Oct

III

O HN R

O

1 2

4a: R1 = H; R2 = But 4b: R1 = H; R2 = Hex 4c: R1 = H; R2 = Oct 4d: R1 = H; R2 = H

3a: R1 = H; R2 = But 3b: R1 = H; R2 = Hex 3c: R1 = H; R2 = Oct 3d: R1 = H; R2 = H

R

2

1

4a': R1 = NHBut; R2 = But 4b': R1 = NHBut; R2 = Hex 4c': R1 = NHBut; R2 = Oct 4d': R1 = NHBut; R2 = H

3

Figure 1. Reaction sequence for the synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-

4

anthraquinone dyes - I: Marschalk alkylation: 1. MeOH:H2O (1:1), 5wt% NaOH, Na2S2O4,

5

corresponding aldehyde, 75°C, Ar atmosphere. 2. Cooling followed by addition of 2M HCl. IIa:

6

Tosylation using tetra butyl ammonium bromide (TBAB) as phase-transfer catalyst (PTC):

7

Dichloromethane/H2O, p-toluene sulfonyl chloride (TsCl), triethylamine (Et3N), room temperature, 3

8

days under vigorous stirring. IIb: Tosylation: Acetonitrile (MeCN), TsCl, Et3N, reflux, 5h or overnight.

9

III: Butylamination: pyridine, large excess of n-butylamine, 50°C, 2 to 5 days.

10 11

Aiming at broadening the colour gamut that is limited to the wavelength range of about 430-

12

480 nm for the alkylated 1-hydroxy-9,10-anthraquinone (2a-c) and 1,4-dihydroxy-9,10-

13

anthraquinone disperse dyes (2a’-2c’), the respective hydroxyl groups were replaced by n-butyl

14

amino moieties that were expected to contribute both increased solubility and bathochromic shift of

15

light adsorption. Substitution of the hydroxyl groups in compounds 1, 1’, 2a-c and 2a’-2c’ by n-butyl

16

amino moieties was accomplished by subjecting the products of the Marschalk alkylation to

17

consecutive tosylation (IIa and IIb in Figure 1) and amination (III). Tetra butyl ammonium bromide

8

1

was used as a phase transfer catalyst in tosylation, since common approaches yielded dark coloured

2

products that required elaborate purification by column chromatography [30].

3 4

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-hydroxy-2-butyl-9,10-anthraquinone

2a

yellow

115-116

63.6

1-hydroxy-2-hexyl-9,10-anthraquinone

2b

yellow

99-100

55.1

1-hydroxy-2-octyl-9,10-anthraquinone

2c

yellow

101-104

27.5

1,4-dihydroxy-2-butyl-9,10-anthraquinone

2a’

orange

120-123

72.0

1,4-dihydroxy-2-hexyl-9,10-anthraquinone

2b’

orange

99-100

71.9

1,4-dihydroxy-2-octyl-9,10-anthraquinone

2c’

orange

94-95

83.0

1-p-toluonesulfonyloxy-2-butyl-9,10-anthraquinone

3a

orange/yellow

107-109

64.6

1-p-toluonesulfonyloxy-2-hexyl-9,10-anthraquinone

3b

orange/yellow

116-118

65.2

1-p-toluonesulfonyloxy-2-octyl-9,10-anthraquinone

3c

orange/yellow

97-99

41.5

1-p-toluonesulfonyloxy-9,10-anthraquinone

3d

orange/yellow

147-149

41.2

1,4-p-bis(toluonesulfonyloxy)-2-butyl-9,10-anthraquinone

3a’

pale yellow

164-166

61.1

1,4-p-bis(toluonesulfonyloxy)-2-hexyl-9,10-anthraquinone

3b’

pale yellow

148-150

64.4

1,4-p-bis(toluonesulfonyloxy)-2-octyl-9,10-anthraquinone

3c’

pale yellow

134-136

33.3

1,4-p-bis(toluonesulfonyloxy)-9,10-anthraquinone

3d’

bright yellow

227-230

73.8

1-butylamino-2-butyl-9,10-anthraquinone

4a

red

50-52

85.4

1-butylamino-2-hexyl-9,10-anthraquinone

4b

red

55-57

85.8

1-butylamino-2-octyl-9,10-anthraquinone

4c

red

55-58

80.0

1-butylamino-9,10-anthraquinone

4d

red

80-81

71.2

1,4-bis(butylamino)-2-butyl-9,10-anthraquinone

4a’

blue

60-61

63.2

1,4-bis(butylamino)-2-hexyl-9,10-anthraquinone

4b’

blue

73-75

59.9

1,4-bis(butylamino)-2-octyl-9,10-anthraquinone

4c’

blue

60-62

67.9

1,4-bis(butylamino)-9,10-anthraquinone

4d’

blue

105-108

73.7

Tosylation of 1 and 2a-c (Reaction IIa)

Tosylation of 1’ and 2a’-c’ (Reaction IIb)

Butylamination of 3a-d and 3a’-3d’ (Reaction III)

5 6

All tosylated compounds were purified by recrystallization and obtained at moderate yields. While a

7

slightly bathochromic effect was observed for the more orange-shaded tosylates of 3a-c, bis-

9

1

tosylation seems to broaden light adsorption considerably as evident from the pale yellow / off-

2

white appearance of compounds 3a’-c’.

3

Amination of the (2-substituted) tosylates as conducted in pyridine at 50°C using a large excess of n-

4

butyl amine was followed by thin-layer chromatography. After quantitative consumption of the

5

respective educts 3a-3d and 3a’-3d’ the obtained crude products were purified by column

6

chromatography to yield the products of major interest in high (4a-4c; 80.0-85.8%) and moderate

7

(4a’-4c’; 59.9-67.9%) yields, respectively. The expected bathochromic effect triggered by

8

introduction of n-butyl amino groups was confirmed to occur as evident from the shift of colour

9

from yellow (2a-2c) to red (4a-4c) for the derivatives of 1 and from yellow-orange (2a’-2c’) to blue

10

(4a’-4c’) for the derivatives of 1’.

11

Visual colour perception of the purified dyes was complemented by UV/Vis spectroscopy. The

12

impact of the different substitution pattern on light absorption was studied for two series of

13

compounds derived from 1-hydroxy-9,10-anthraquinone (1) and 1,4-dihydroxy-9,10-anthraquinone

14

(quinizarin, 1’). Each set comprises of three compounds representing the synthesis steps i)

15

Marschalk alkylation (2a, 2a’), ii) tosylation (3a, 3a’) and iii) n-butyl amination (4a, 4a’) conducted in

16

this work (Figure 2).

17

10

1

Figure 2. UV/Vis spectra of selected 9,10-anthraquinone dyes in 2-propanol (ca. 0.05 mg mL-1),

2

representing the two groups of compounds derived from 1 and 1’ by sequential Marschalk alkylation

3

(2a, 2a’), tosylation (3a, 3a’) and n-butyl amination (4a, 4a’).

4

It is evident from Figure 2 that all anthraquinone derivatives are strongly absorbent in the UV region

5

which is inherent to the anthraquinone basic structure. In the range of the visible light, the π1π*

6

absorption maximum of the non-substituted compounds 1 and 1’ is at 403 nm and 481 nm,

7

respectively. Addition of n-alkyl residues in 2-position effectuates a slight bathochromic shift of the

8

E-band of the respective parent compounds which was 9 nm (2a) and 3 nm (2a’), respectively, for

9

introduction of n-butyl moieties. The tosylated compounds (3a and 3a’, Figure 2) did virtually not

10

show any absorbance in the visible range due to the strongly electron-withdrawing and, hence,

11

hypsochromic effect of the tosylate groups. The faint yellowish colour visually observed is assumed

12

to originate from trace residual contents of the respective educts. Amination and eventual

13

replacement of the tosylate groups by strongly electron donating n-butyl amino moieties had the

14

desired pronounced bathochromic effect. While the maximum light absorption shifted from 412 nm

15

(2a) to 509 nm (4a) for the mono amino derivative, it was even more pronounced for the 1,4-bis(n-

16

butylamino) compound 4a’. Here the maximum absorbance shifted from 481 nm (1’) to 620 nm

17

(centre of doublet at 597 and 643 nm) which is perceived as deep blue colour.

18

These results are in good agreement with values observed elsewhere [31]. Furthermore, the

19

observed absorption maxima for 4a and 4a’ correlate well with the results of ab initio molecular

20

orbital calculations (density functional theory, DFT). The latter yield a red and blue shift for the 1-n-

21

butylamino (4a, λmax simulation = 522 nm, f = 0.171) and 1,4-bis(n-butylamino) (4a’, λmax simulation = 584

22

nm, f = 0.270) derivatives of 1-hydroxy-2-n-butyl-9,10-anthraquinone which was in good agreement

23

with the visual observation. The pronounced shift results from the significant contribution of the n-

24

butylamino moieties to the highest / lowest occupied molecular orbital (HOMO, LUMO) of 4a’ and

25

4a which is not the case for the products of the preceding steps (1-3a and 1’-3a’; Figure 3). Quantum

11

1

computational studies furthermore confirmed the electron withdrawing effect of the p-

2

toluenesulfonyloxy moieties which is known to impede energy dissipation.

3 4

Figure 3. Highest occupied molecular orbital (HOMO, left) and lowest unoccupied molecular orbital

5

(LUMO, right) of compounds 1, 1’, 2a, 2a’, 3a, 3a’, 4a and 4a’ as calculated by DFT.

6

A comparison of the calculated (DFT) and measured (UV/Vis spectroscopy) maximum adsorption

7

wavelength values for two sets of compounds derived from 1 (2a-4a; Table 2) and 1’ (2a’-4a’),

8

respectively, confirms that the application of DFT at the B3LYP/6-311++g(d,p) level of theory is an

9

appropriate tool to predict the light absorption behaviour of 9,10-anthraquinone derivatives. The

10

main contributor to the slight differences between calculated and experimental values is supposedly

11

the insufficient consideration of solvent effects which were here approximated using implicit

12

solvation with the polarizable continuum model [32, 33]. 12

1

Table 2. Experimental and calculated maximum absorption wavelengths in the visible domain with

2

their respective molar extinction coefficients and frequencies. Compound

λmax exp. (nm)

εexp. (M-1.cm-1)

λmax simulation (nm)

f

1

403

5415

412

0.164

2a

412

5912

424

0.205

3a

257a

n.d.

263

0.469

4a

509

5795

522

0.171

1’

481

6514

468

0.222

2a’

484

9959

472

0.258

3a’

203a

n.d.

200

0.311

4a’b

597

16486

584

0.270

643

16103

3

a

4

determined.

5

X-ray diffraction analysis was performed to confirm the chemical structure of compound 4a, to

6

elucidate its conformation and to compare the structures proposed by quantum chemical DFT

7

calculations and X-ray analysis.

8

X-ray data obtained for a single 4a’ crystal were in good agreement with the simulated structure

9

(details in Supplementary Information). Besides confirmation of its planar structure, compound 4a’

10

was found to arrange in triclinic unit cells. The hydrogen bonds between the amino and ketone

11

moieties of 4a’ were noticed (Table 3). They also contribute to the wavelength of the absorption

12

maximum [34] CIF file for compound 4a’ has been submitted to the Cambridge Crystallographic Data

13

Centre (Reference number: CCDC1877294).

maximum absorption in UV;

b

doublet with similar molar extinction coefficients; n.d.: not

13

1 2

Figure 4. Crystal structure of 4a’ anisotropic displacement ellipsoids visualized with 50% probability

3

(blue), overlapped with the simulated structure as obtained by DFT (orange). Due to the

4

asymmetrical structure, HB-1 and HB-2 represent different hydrogen bonds.

5

The anthraquinone skeleton structure as proposed by X-ray analysis shows a high correlation with

6

that of DFT simulation. The only notable mismatches concern the conformation of the two n-butyl

7

substituents attached to the amino group and the C2 position which is easily comprehensible due to

8

their high degrees of rotational freedom.

9

Table 3. Distances of the simulated H-bonds present in 1’, 2a’, 3a’ and 4a’ compared to the H-bonds

10

observed in the X-ray crystallographic data of 4a’. a: Isopropanol as solvent was modelled with the

11

Polarisable Continuum Model, b: except for the one used to compare the simulated structure of 4a’

12

with the X-ray data, here no solvent was used for modelling. c: symmetrical structure.

13

14

Simulateda

Simulateda

Simulatedb

Crystal structure 4a’

1’

2a’

4a’

(X-ray)

O- - - H-O

O- - - H-O

O- - - H-N

O- - - H-N

1.657

1.768

1.970

1.678

1.773

1.878

Nature of the bond HB-1 distance (Å) 1.681c HB-2 distance (Å) 1 2 3

3.

Materials and methods 3.1 Materials

4

All chemicals were purchased from Sigma-Aldrich, TCI Chemicals or VWR, were of synthesis grade

5

and used without further purification. Fourier transform infrared spectroscopy (FTIR) was performed

6

using a Perkin Elmer Frontier IR Single-Range spectrometer (Waltham, Massachusetts, USA) in ATR

7

mode (diamond/ZnSe crystal, LiTaO3 detector, KBr windows). All spectra were derived from 16 scans,

8

each covering the wavelength range of 600 to 4000 cm-1 at a resolution of 4 cm-1. All spectra were

9

baseline corrected and normalized to the highest peak. All NMR spectra were measured at 25°C

10

using a Bruker Avance II 400 (resonance frequencies 400.13 MHz for 1H and 100.63 MHz for 13C)

11

instrument. The latter was equipped with a 5 mm broadband probe head (BBFO) with z–gradients.

12

Standard Bruker pulse programmes were used. The samples were dissolved in 0.6 ml of CDCl3 (99.8

13

% D, euriso-top, Saint-Aubin, France). Chemical shifts are given in ppm, referenced to residual

14

solvent signals (7.26 ppm for 1H, 77.0 ppm for

15

respectively, was accomplished based on the set of complementary 1H, 13C-jmod, COSY, HSQC and

16

HMBC experiments (for peak assignment see Supplementary Information). UV/Vis spectra were

17

acquired with a Perkin Elmer Lambda35 instrument. The high correlation coefficients (R2 = 0.999)

13

C). Structure elucidation and confirmation,

15

1

were used to calculate molar extinction coefficients at the selected wavelength. Elemental analyses

2

were performed at Microanalytical Laboratory, University of Vienna, Austria (report numbers

3

0418/0428 and 0518/0616). Melting points were determined from three independent

4

measurements using a Thermo Scientific 9300 apparatus.

5

3.2 General procedure for the Marschalk alkylation of 1-hydroxy-9,10-anthraquinone (1) and

6

1,4-dihydroxy-9,10-anthraquinone (1’) (Reaction I, Figure 1)

7

1-Hydroxy-9,10-anthraquinone (1) or 1,4-dihydroxy-9,10-anthraquinone (1’) (1 mmol) and Na2S2O4

8

(5.75 mmol) were co-dissolved in aqueous methanol (50:50, v/v) (50 mL) containing 5 w% of NaOH

9

under argon atmosphere. Once dissolution was completed, an excess of the respective aldehyde (2a:

10

butanal, 2b: hexanal etc.) was added and the mixture stirred vigorously at 75°C overnight. After

11

cooling using an ice-water bath, the product mixture was acidified with HCl (2M, 50-100 mL)

12

whereupon a change of colour occurred and a precipitate was formed. After filtration and washing

13

with deionized water (500 mL), the pasty product was washed with hot CH3OH, which removes

14

mainly side-products of competing aldol reactions and residual educts. This was confirmed by 1H

15

NMR analysis of the solid product obtained after cooling and freeze-drying (data not shown). The

16

washing procedure was repeated up to two times yielding (NMR) pure products.

17

3.2.1 1-Hydroxy-2-butyl-9,10-anthraquinone (2a)

18

Following the general procedure described in section 2.2, compound 2a was synthesized by reacting

19

1 (1.34 g, 6 mmol) and Na2S2O4 (6 g, 34.5 mmol) with butyraldehyde (6 ml, 66.6 mmol). After work-

20

up of the crude product, 1.07g (3.8 mmol) of 2a were obtained. UV (iPrOH) λmax (ε x 10-4, M-1.cm-1):

21

412 (0.59) nm. IR νmax(cm-1): 2953, 2932, 2871, 1667, 1628, 1589, 1427, 1353, 1327, 1294, 1260,

22

1203, 1153, 1104, 995, 892, 851, 790, 719, 657. 1H NMR (400.13 MHz, CDCl3): δ = 13.00 (s, 1H), 8.32

23

(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,

24

2H), 1.67 (m, 2H), 1.43 (m, 2H), 0.97 (t, J = 7.3 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 189.07,

25

182.49, 160.95, 139.51, 136.45, 134.50, 133.96, 133.85, 133.40, 131.33, 127.3, 126.88, 119.30, 16

1

115.46, 31.23, 29.68, 22.59, 13.91. Anal. Calcd. for C18H16O3: C 77.12, H 5.75, N 0. Found.: C 76.80, H

2

5.60, N <0.05.

3

3.2.2 1-Hydroxy-2-hexyl-9,10-anthraquinone (2b)

4

Following the procedure described in 2.2, 1 (1.12 g, 5 mmol) and Na2S2O4 (5 g, 28.7 mmol) were

5

reacted with hexanal (6 mL, 48.8 mmol) to yield 0.85g (2.76 mmol, 55.1%) of 2b after washing and

6

freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10-4, M-1.cm-1): 412 (0.67) nm. IR νmax/cm-1: 2950,

7

2926, 2854, 1667, 1628, 1589, 1427, 1353, 1294, 1261, 1200, 1152, 1115, 1042, 1008, 892, 852, 791,

8

717, 658. 1H NMR (400.13 MHz, CDCl3) δ: 13.00 (s, 1H), 8.32 (m, 1H), 8.29 (m, 1H), 7.80 (m, 2H), 7.78

9

(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,

10

2H), 1.33 (m, 2H), 0.90 (t, J = 7.0 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 189.09, 182.45, 160.96,

11

139.56, 136.47, 134.50, 133.96, 133.86, 133.41, 131.33, 127.30, 126.88, 119.31, 115.47, 31.67,

12

30.00, 29.19, 29.06, 22.60, 14.06. Anal. Calcd. for C20H20O3: C 77.9, H 6.54, N 0. Found: C 75.92, H

13

6.38, N <0.05.

14

3.2.3 1-Hydroxy-2-octyl-9,10-anthraquinone (2c)

15

Following the procedure described in 2.2, 1 (896.8 mg, 4 mmol) and Na2S2O4 (4 g, 23.0 mmol) were

16

reacted with octanal (7 mL, 44.8 mmol) to yield 0.37g (1.10 mmol, 27.5%) of compound 2c after

17

washing and freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10-4, M-1.cm-1): 412 (0.54) nm. IR νmax/cm-

18

1

19

894, 850, 792, 717, 657. 1H NMR (400.13 MHz, CDCl3) δ: 13.00 (s, 1H), 8.32 (m, 1H), 8.29 (m, 1H),

20

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

21

(m, 2H), 1.29 (m, 2H), 1.29 (m, 6H), 0.88 (t, J = 7.0 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 189.08,

22

182.45, 160.95, 139.56, 136.45, 134.50, 133.95, 133.85, 133.41, 131.32, 127.29, 126.88, 119.31,

23

115.47, 31.87, 30.00, 29.52, 29.43, 29.24, 29.10, 22.65, 14.08. Anal. Calcd. for C22H24O3: C 78.54, H

24

7.19, N 0. Found: C 78.00, H 7.48, N <0.05.

: 2950, 2923, 2853, 1668, 1628, 1589, 1427, 1353, 1325, 1289, 1263, 1199, 1152, 1121, 1042, 1009,

17

1

3.2.4 1,4-Dihydroxy-2-butyl-9,10-anthraquinone (2a’)

2

Following the procedure described in 2.2, 1’ (720 mg, 3 mmol) and Na2S2O4 (3 g, 17.2 mmol) were

3

reacted with butyraldehyde (3 mL, 33.3 mmol) to yield 0.64 g (2.16 mmol, 72.0%) of compound 2a’

4

after washing and freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10-4, M-1.cm-1): 484 (1.00), 518

5

(0.63) nm. IR νmax/cm-1: 2962, 2938, 2875, 1625, 1583, 1434, 1404, 1348, 1298, 1267, 1237, 1213,

6

1120, 1065, 1028, 1002, 960, 892, 811, 778, 717, 681. 1H NMR (400.13 MHz, CDCl3) δ: 13.42 (s, 1H),

7

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,

8

2H), 0.97 (t, J = 7.3 Hz, 3H) .13C NMR (100.63 MHz, CDCl3) δ: 187.21, 186.30, 157.89, 157.24, 145.51,

9

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.

10

Anal. Calcd. for C18H16O4: C 72.96, H 5.44, N 0. Found: C 72.98, H 5.37, N <0.05.

11

3.2.5 1,4-Dihydroxy-2-hexyl-9,10-anthraquinone (2b’)

12

Following the procedure described in 2.2, 1’ (1.44 g, 6 mmol) and Na2S2O4 (6 g, 34.5 mmol) were

13

reacted with hexanal (7.2 mL, 58.5 mmol) to yield 1.40 g (4.32 mmol, 71.9%) of compound 2b’ after

14

washing and freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10-4, M-1.cm-1): 484 (0.95), 518 (0.60) nm.

15

IR νmax/cm-1: 3068, 2931, 2855, 1621, 1582, 1426, 1398, 1344, 1305, 1242, 1217, 1119, 1067, 1031,

16

960, 916, 814, 785, 720, 681. 1H NMR (400.13 MHz, CDCl3) δ: 13.42 (s, 1H), 12.98 (s, 1H), 8.34 (m,

17

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

18

(t, J = 7.1 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 187.21, 186.30, 157.89, 157.24, 145.56, 134.31,

19

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,

20

14.06. Anal. Calcd. for C20H20O4: C 74.06, H 6.21, N 0. Found: C 73.13, H 6.05, N <0.05.

21

3.2.6 1,4-Dihydroxy-2-octyl-9,10-anthraquinone (2c’)

22

Following the procedure described in 2.2, 1’ (1.44 g, 6 mmol) and Na2S2O4 (6 g, 34.5 mmol) were

23

reacted with octanal (10 mL, 64.0 mmol) to yield 1.75 g (4.98 mmol, 83.0%) of compound 2c’ after

24

washing and freeze-drying (cf. Table 1). UV (iPrOH) λmax (ε x 10-4, M-1.cm-1): 484 (0.97), 518 (0.61) nm.

18

1

IR νmax/cm-1: 3070, 2919, 2853, 1622, 1583, 1426, 1404, 1345, 1268, 1236, 1210, 1118, 1070, 1023,

2

959, 906, 813, 788, 719, 681. 1H NMR (400.13 MHz, CDCl3) 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

4

(t, J = 7.2 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 187.21, 186.30, 157.89, 157.24, 145.57, 134.31,

5

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,

6

28.75, 22.65, 14.07. Anal. Calcd. for C22H24O4: C 74.98, H 6.21, N 0. Found: C 75.01, H 6.84, N <0.05.

7

3.3 General procedure for the tosylation of 1-hydroxy-9,10-anthraquinone (1) and 1-hydroxy-2-

8

alkyl-9,10-anthraquinones (2a-c) (Reaction IIa)

9

Common tosylation of 1-hydroxy-9,10-anthraquinone (1) and 1-hydroxy-2-alkyl-9,10-anthraquinones

10

(2a-c) with p-toluenesulfonyl chloride (TsCl) and pyridine [30] turned out to afforded dark brownish

11

solids which required elaborate purification by column chromatography prior further modification.

12

This obstacle could be overcome by performing sulfonylation in a biphasic medium

13

(water/dichloromethane) using tetra butyl ammonium bromide (TBAB) as a phase transfer catalyst.

14

Controlled by pH (61.6 mM NaOH), TBAB is converted into (C4H9)4N+OH- that migrates into the upper

15

organic phase and forms there under release of water the respective tetra butyl ammonium salts of

16

compounds 1 or 2a-c. The latter eventually react with TsCl to afford the tosylates 3a-3d and

17

(C4H9)4N+Cl- migrates back into the aqueous phase. All reactions were performed at room

18

temperature in a round bottom flask under vigorous stirring. After completion of the reaction (ca. 3

19

days) which was determined by TLC (SiO2, CH2Cl2), the organic phase was separated, washed

20

exhaustively with deionized water and dried over anhydrous Na2SO4. After evaporation of the

21

organic phase, the solid products were recrystallized from CHCl3/hexane.

22

3.3.1 1-p-Toluonesulfonyloxy-2-butyl-9,10-anthraquinone (3a)

23

Following the procedure described in section 2.3 (Reaction IIa, Figure 1), 2a (1.12 g, 4 mmol) and

24

TsCl (3.89 g, 20.4 mmol) in CH2Cl2 (280 mL) were mixed with a solution of NaOH (1.18 g, 29.6 mmol)

25

and TBAB (6.576 g, 20.4 mmol) in deionized water (480 mL). After working-up of the reaction 19

1

mixture and recrystallization from CHCl3/hexane 1.12 g (2.58 mmol, 64.6%) of 3a were obtained (cf.

2

Table 1). IR νmax/cm-1: 2962, 2930, 2873, 1675, 1588, 1493, 1452, 1426, 1384, 1314, 1275, 1237,

3

1165, 1090, 1041, 1006, 975, 931, 892, 852, 816, 761, 738, 662. 1H NMR (400.13 MHz, CDCl3) δ: 8.23

4

(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,

5

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 =

6

7.3 Hz, 3H). 13C NMR (100.63 MHz, CDCl3) δ: 182.25, 181.98, 145.61, 145.45, 145.23, 135.48, 134.71,

7

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,

8

30.26, 22.54, 21.68, 13.76. Anal. Calcd. for C25H22O5S1: C 69.11, H 5.1, N 0, S 7.38. Found: C 68.94, H

9

5.1, N <0.05, S 7.4.

10

3.3.2 1-p-Toluonesulfonyloxy-2-hexyl-9,10-anthraquinone (3b)

11

Following the procedure described in section 2.3 (Reaction IIa, Figure 1), 2b (616 mg, 2 mmol) and

12

TsCl (1.94 g, 10.2 mmol) in CH2Cl2 (140 mL) were mixed with a solution of NaOH (594 mg, 14.8 mmol)

13

and TBAB (3.29 g, 10.2 mmol) in deionized water (240 mL). After working-up of the reaction mixture

14

and recrystallization from CHCl3/hexane 603 mg (1.30 mmol, 65.2%) of 3b were obtained (cf. Table

15

1). IR νmax/cm-1: 2962, 2934, 2858, 1676, 1588, 1468, 1374, 1311, 1284, 1220, 1156, 1089, 1038,

16

1004, 890, 848, 816, 767, 737, 717, 670, 632. 1H NMR (400.13 MHz, CDCl3) δ: 8.23 (d, J = 8.0 Hz, 1H),

17

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 =

18

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).13C

19

NMR (100.63 MHz, CDCl3) δ: 182.24, 181.98, 145.62, 145.42, 145.22, 135.45, 134.70, 134.08, 133.64,

20

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,

21

22.52, 21.67, 14.02. Anal. Calcd. for C27H26O5S1: C 70.11, H 5.67, N 0, S 6.93. Found: C 69.69, H 5.63,

22

N <0.05, S 6.97.

23

3.3.3 1-p-Toluonesulfonyloxy-2-octyl-9,10-anthraquinone (3c)

24

Following the procedure described in section 2.3 (Reaction IIa, Figure 1), 2b (336 mg, 1 mmol) and

25

TsCl (972 mg, 5.1 mmol) in CH2Cl2 (70 mL) were mixed with a solution of NaOH (297 mg, 7.4 mmol) 20

1

and TBAB (1.64 g, 5.1 mmol) in deionized water (120 mL). After working-up of the reaction mixture

2

and recrystallization from CHCl3/hexane 204 mg (0.42 mmol, 41.5%) of 3c were obtained (cf. Table

3

1). IR νmax/cm-1: 2926, 2855, 1678, 1588, 1467, 1428, 1380, 1322, 1271, 1222, 1194, 1164, 1121,

4

1091, 1039, 891, 812, 767, 735, 714, 666. 1H NMR (400.13 MHz, CDCl3) δ: 8.23 (d, J = 8.0 Hz, 1H),

5

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 =

6

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).13C

7

NMR (100.63 MHz, CDCl3) δ: 182.25, 181.98, 145.64, 145.43, 145.22, 135.47, 134.71, 134.09, 133.65,

8

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,

9

29.28, 29.18, 22.64, 21.68, 14.08. Anal. Calcd. for C29H30O5S1: C 71, H 6.16, N 0, S 6.54. Found: C

10

70.42, H 6.09, N <0.05, S 6.43.

11

3.3.4 1-p-Toluonesulfonyloxy-9,10-anthraquinone (3d)

12

Following the procedure described in section 2.3 (Reaction IIa, Figure 1), 1 (504 mg, 2.25 mmol) and

13

TsCl (2.20 g, 11.6 mmol) in CH2Cl2 (180 mL) were mixed with a solution of NaOH (760 mg, 19 mmol)

14

and TBAB (3.75 g, 11.6 mmol) in deionized water (360 mL). After working-up of the reaction mixture

15

and recrystallization from CHCl3/hexane 350 mg (0.93 mmol, 41.2%) of 3d were obtained (cf. Table

16

1). IR νmax/cm-1: 2961, 2927, 2878, 1725, 1674, 1588, 1495, 1443, 1376, 1313, 1276, 1173, 1093,

17

1043, 1005, 876, 840, 802, 746, 702, 662. 1H NMR (400.13 MHz, CDCl3) δ: 8.31 (dd, J = 7.9, 1.3 Hz,

18

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,

19

1H), 7.55 (dd, J = 8.2, 1.3 Hz, 1H), 7.32 (d, J = 8.4 Hz, 2H), 2.40 (s, 3H).13C NMR (100.63 MHz, CDCl3) δ:

20

182.18, 180.72, 147.76, 145.59, 135.56, 134.39, 134.38, 134.34, 133.85, 132.69, 132.38, 130.07,

21

129.70, 128.88, 127.37, 126.86, 126.58, 126.52, 21.68. Anal. Calcd. for C21H14O5S1: C 66.66, H 3.73, N

22

0, S 8.47. Found: C 65.35, H 3.73, N 0.124, S 8.51.

23

3.4 General procedure for the tosylation of 1,4-dihydroxy-9,10-anthraquinone (1’) and 1,4-

24

dihydroxy-2-alkyl-9,10-anthraquinones (2a’-c’) (Reaction IIb)

21

1

It is worth mentioning that different from 1-hydroxy-9,10-anthraquinone (1) and its 2-alkyl

2

derivatives (2a-2c), tosylation of the 1,4-dihydroxy-9,10-anthraquinone counterparts (1’, 2a’-2c’) did

3

neither require a phase catalyst nor column chromatography to obtain 1H NMR pure compounds.

4

Typically, 1,4-dihydroxy-9,10-anthraquinone (1’) or 1,4-dihydroxy-2-alkyl-9,10-anthraquinone (2a’-c’)

5

(1 mmol) was dissolved in acetonitrile (ACN) (9 mL) that contained triethylamine (Et3N) (1.5 mL, 11.1

6

mmol). After adding p-toluenesulfonyl chloride (TsCl) (2.5 mmol) the mixture was refluxed under

7

stirring for 5h (1’) or overnight (2a’-c’). Monitoring of the reaction was accomplished by TLC (SiO2,

8

CH2Cl2). After evaporation of the solvent, the solid product was re-dissolved in dichloromethane. The

9

obtained organic phase was washed with deionized water several times and dried over anhydrous

10

Na2SO4. Following removal of solvent, the obtained product was recrystallized (CHCl3/hexane),

11

washed with hexane and dried.

12

3.4.1 1,4-Bis(p-toluonesulfonyloxy)-2-butyl-9,10-anthraquinone (3a’)

13

Following the procedure described in section 2.4 (Reaction IIb, Figure 1), 2a’ (296 mg, 1 mmol) was

14

reacted with TsCl (480 mg, 2.5 mmol) in the presence of Et3N (1.5 mL, 11.1 mmol). After working-up

15

of the reaction mixture and recrystallization from CHCl3/hexane 369 mg (0.61 mmol, 61.1%) of 3a’

16

was obtained (cf. Table 1). IR νmax/cm-1: 2957, 2930, 2863, 1683, 1594, 1494, 1445, 1374, 1313, 1256,

17

1166, 1090, 1021, 929, 898, 814, 755, 665, 620. 1H NMR (400.13 MHz, CDCl3) δ: 8.03 (m), 7.96 (m),

18

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

19

= 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 =

20

7.2 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 181.95, 180.15, 146.68, 145.81, 145.77, 145.75, 143.66,

21

133.77, 133.37, 132.99, 132.40, 130.87, 130.34, 129.92, 129.74, 128.96, 128.67, 126.72, 126.69,

22

125.88, 31.34, 30.03, 22.41, 21.70, 21.68, 13.73. Anal. Calcd. for C32H28O8S2: C 63.56, H 4.67, N 0, S

23

10.61. Found: C 63.17, H 4.69, N <0.05, S 10.61.

24

3.4.2 1,4-Bis(p-toluonesulfonyloxy)-2-hexyl-9,10-anthraquinone (3b’)

22

1

Following the procedure described in section 2.4 (Reaction IIb, Figure 1), 2b’ (324 mg, 1 mmol) was

2

reacted with TsCl (480 mg, 2.5 mmol) in the presence of Et3N (1.5 mL, 11.1 mmol). After working-up

3

of the reaction mixture and recrystallization from CHCl3/hexane 407 mg (0.64 mmol, 64.4%) of 3b’

4

was obtained (cf. Table 1). IR νmax/cm-1: 2951, 2918, 2857, 1682, 1594, 1494, 1446, 1378, 1319, 1258,

5

1168, 1090, 1045, 930, 895, 814, 741, 698, 662, 608. 1H NMR (400.13 MHz, CDCl3) δ: 8.03 (m), 7.96

6

(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

7

(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

8

(m, 2H), 0.89 (t, J = 6.5 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 181.94, 180.15, 146.71, 145.81,

9

145.75, 145.74, 143.65, 133.76, 133.71, 133.37, 133.01, 132.40, 130.85, 130.36, 129.91, 129.76,

10

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,

11

14.02. Anal. Calcd. for C34H32O8S2: C 64.54, H 5.1, N 0, S 10.14. Found: C 64.24, H 5.07, N <0.05, S

12

10.14.

13

3.4.3 1,4-Bis(p-toluonesulfonyloxy)-2-octyl-9,10-anthraquinone (3c’)

14

Following the procedure described in section 2.4 (Reaction IIb, Figure 1), 2c’ (352 mg, 1 mmol) was

15

reacted with TsCl (0.48 g, 2.5 mmol) in the presence of Et3N (1.5 mL, 11.1 mmol). After working-up

16

of the reaction mixture and recrystallization from CHCl3/hexane 220 mg (0.33 mmol, 33.3%) of 3c’

17

was obtained (cf. Table 1). IR νmax/cm-1: 2928, 2851, 1682, 1594, 1494, 1447, 1379, 1319, 1257, 1169,

18

1090, 1020, 930, 896, 813, 741, 699, 664, 608. 1H NMR (400.13 MHz, CDCl3) δ: 8.03 (m), 7.96 (m),

19

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,

20

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,

21

8H), 0.90 (t, J = 6.9 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 181.95, 180.16, 146.73, 145.82, 145.75,

22

143.64, 133.76, 133.72, 133.38, 133.02, 132.41, 130.87, 130.32, 129.92, 129.73, 128.96, 128.61,

23

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.

24

Calcd. for C36H36O8S2: C 65.43, H 5.49, N 0, S 9.7. Found: C 64.98, H 5.42, N <0.05, S 9.72.

25

3.4.4 1,4-Bis(p-toluonesulfonyloxy)-9,10-anthraquinone (3d’)

23

1

Following the procedure described in section 2.4 (Reaction IIb, Figure 1), 1’ (2.5 g, 10.4 mmol) was

2

reacted with TsCl (4.8 g, 25.2 mmol) in the presence of Et3N (10 mL, 74.1 mmol). After working-up of

3

the reaction mixture and recrystallization from CHCl3/hexane 4.215 g (7.7 mmol, 73.8%) of 3d’ was

4

obtained (cf. Table 1). IR νmax/cm-1: 3073, 1678, 1583, 1492, 1451, 1403, 1347, 1306, 1260, 1218,

5

1169, 1089, 1021, 925, 896, 867, 810, 781, 744, 705, 673, 617. 1H NMR (400.13 MHz, CDCl3) δ: 8.02

6

(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).13C

7

NMR (100.63 MHz, CDCl3) δ: 180.36, 146.10, 145.89, 133.94, 133.36, 132.28, 130.53, 129.82, 128.89,

8

128.37, 126.80, 21.69. Anal. Calcd. for C28H20O8S2: C 61.3, H 3.67, N 0, S 11.69. Found: C 61.2, H 3.62,

9

N <0.05, S 11.88.

10

3.5

General

procedure

11

anthraquinones

12

toluonesulfonyloxy)-2-alkyl-9,10-anthraquinones (3a’-c’) and 1,4- bis(p-toluonesulfonyloxy)-

13

9,10-anthraquinone (3d’) (Reaction III, Figure 1)

(3a-c),

for

butylamination

of

1-p-toluonesulfonyloxy-2-alkyl-9,10-

1-p-toluonesulfonyloxy-9,10-anthraquinone

(3d),

1,4-bis(p-

14

A large excess (400-1000 mol eq.) of n-butylamine was added to a solution of the respective

15

tosylated compound in pyridine and the reaction mixture was kept at 50°C for 2-5 days to ensure

16

completion of the reaction which was monitored by TLC (SiO2; heptane-ethylacetate ratio 6:1). After

17

cooling, pyridine was removed by co-evaporation with toluene. Column chromatography was then

18

performed (SiO2, heptane-to-ethylacetate ratio 6:1), the first eluting red (for educts 3a-d) and blue

19

fraction (for educts 3a’-d’), respectively, was collected. After evaporation of solvent, the obtained

20

solids were recrystallized from absolute ethanol.

21

3.5.1 1-Butylamino-2-butyl-9,10-anthraquinone (4a)

22

Following the procedure described in section 2.5, 3a (867 mg, 2 mmol) and n-butylamine (79.1mL,

23

800 mmol) were co-dissolved in pyridine (70 mL). The mixture was kept at 50°C for two days. After

24

work-up and recrystallization 602 mg (1.80 mmol, 85.4%) of 4a was obtained (cf. Table 1). UV

25

(iPrOH) λmax (ε x 10-4, M-1.cm-1): 509 (0.58) nm. IR νmax/cm-1: 3073, 2954, 2929, 2871, 1663, 1624, 24

1

1522, 1455, 1351, 1303, 1258, 1177, 1103, 1049, 1009, 965, 897, 841, 789, 716, 670. 1H NMR

2

(400.13 MHz, CDCl3) 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 =

4

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),

5

1.40 (m, 2H), 0.97 (t, J = 7.4 Hz, 3H), 0.96 (t, J = 7.3 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 185.72,

6

183.63, 153.44, 138.48, 136.78, 135.40, 133.79, 132.97, 132.94, 132.83, 127.01, 126.45, 118.18,

7

116.78, 47.44, 34.16, 33.27, 31.84, 22.63, 20.20, 13.93, 13.84. Anal. Calcd. for C22H25O2N1: C 78.77, H

8

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)

10

Following the procedure described in section 2.5, 3b (461.5 mg, 1 mmol) and n-butylamine (39.5 mL,

11

400 mmol) were co-dissolved in pyridine (40 mL). The mixture was kept at 50°C for two days. After

12

work-up and recrystallization 311.6 mg (0.86 mmol, 85.8%) of 4b was obtained (cf. Table 1). UV

13

(iPrOH) λmax (ε x 10-4, M-1.cm-1): 508 (0.60) nm. IR νmax/cm-1: 3071, 2952, 2922, 2851, 1664, 1628,

14

1578, 1507, 1461, 1353, 1304, 1268, 1181, 1039, 976, 904, 850, 773, 710. 1H NMR (400.13 MHz,

15

CDCl3) 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,

16

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),

17

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),

18

1.33 (m, 4H), 0.97 (t, J = 7.4 Hz, 3H), 0.89 (t, J = 6.9 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 185.74,

19

183.62, 153.31, 138.59, 136.79, 135.40, 133.81, 132.96, 132.84, 127.03, 126.47, 118.26, 116.83,

20

47.46, 34.48, 33.24, 31.68, 29.71, 29.23, 22.59, 20.21, 14.03, 13.84. Anal. Calcd. for C24H29O2N1: C

21

79.3, H 8.04, N 3.85, S 0. Found: C 79.05, H 8.16, N 4.01, S <0.02.

22

3.5.3 1-Butylamino-2-octyl-9,10-anthraquinone (4c)

23

Following the procedure described in section 2.5, 3c (155 mg, 0.32 mmol) and n-butylamine (12.5

24

mL, 126.5 mmol) were co-dissolved in pyridine (15 mL). The mixture was kept at 50°C for two days.

25

After work-up and recrystallization 99 mg (0.25 mmol, 80.0%) of 4c was obtained (cf. Table 1). UV 25

1

(iPrOH) λmax (ε x 10-4, M-1.cm-1): 508 (0.62) nm. IR νmax/cm-1: 3072, 2953, 2927, 2848, 1667, 1628,

2

1593, 1522, 1464, 1350, 1302, 1263, 1232, 1171, 1098, 989, 970, 911, 839, 792, 736, 710, 670. 1H

3

NMR (400.13 MHz, CDCl3) 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,

4

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 =

5

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),

6

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).13C NMR

7

(100.63 MHz, CDCl3) δ: 185.74, 183.61, 153.28, 138.60, 136.80, 135.39, 133.81, 132.97, 132.84,

8

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,

9

14.07, 13.84. Anal. Calcd. for C26H33O2N1: C 79.76, H 8.49, N 3.58, S 0. Found: C 79.71, H 8.65, N 3.77,

10

S <0.02.

11

3.5.4 1-Butylamino-9,10-anthraquinone (4d)

12

Following the procedure described in section 2.5, 3d (378 mg, 1 mmol) and n-butylamine (39.5 mL,

13

400 mmol) were co-dissolved in pyridine (50 mL). The mixture was kept at 50°C for three days. After

14

work-up and recrystallization 198.6 mg (0.71 mmol, 71.2%) of 4d was obtained (cf. Table 1). UV

15

(iPrOH) λmax (ε x 10-4, M-1.cm-1): 508 (0.66) nm. IR νmax/cm-1: 3258, 3079, 2957, 2927, 2855, 1662,

16

1627, 1590, 1505, 1472, 1405, 1362, 1302, 1272, 1161, 1136, 1067, 994, 906, 869, 827, 800, 733,

17

705, 660, 606. 1H NMR (400.13 MHz, CDCl3) δ: 9.75 (br.s, 1H), 8.28 (dd, J = 7.6 Hz, 1H), 8.24 (dd, J =

18

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 =

19

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

20

(m, 2H), 1.54 (m, 2H), 1.01 (t, J = 7.4 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 184.96, 183.86, 151.86,

21

135.25, 135.09, 134.69, 133.89, 133.07, 132.84, 126.69, 126.63, 117.86, 115.49, 112.85, 42.68,

22

31.20, 20.36, 13.83. Anal. Calcd. for C18H17O2N1: C 77.4, H 6.13, N 5.01. Found: C 77.33, H 6.08, N

23

4.99.

24

3.5.5 1,4-Bis(butylamino)-2-butyl-9,10-anthraquinone (4a’)

26

1

Following the procedure described in section 2.5, 3a’ (302 mg, 0.5 mmol) and n-butylamine (52.6

2

mL, 530 mmol) were co-dissolved in pyridine (50 mL). The mixture was kept at 50°C for five days.

3

After work-up and recrystallization 128.3 mg (0.32 mmol, 63.2%) of 4a’ was obtained (cf. Table 1).

4

UV (iPrOH) λmax (ε x 10-4, M-1.cm-1): 597 (1.65), 643 (1.61) nm. IR νmax/cm-1: 3064, 2954, 2930, 2867,

5

1610, 1558, 1455, 1362, 1257, 1187, 1090, 1050, 1023, 955, 904, 864, 823, 787, 728, 664, 618. 1H

6

NMR (400.13 MHz, CDCl3) δ: 10.71 (br.s, J = 5.4 Hz, 1H), 10.34 (br.s, 1H), 8.34 (m, 1H), 8.31 (m, 1H),

7

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),

8

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),

9

0.95 (t, J = 7.4 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 184.07, 182.07, 148.03, 147.70, 144.47,

10

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,

11

31.81, 31.68, 22.70, 20.39, 20.29, 13.94, 13.87. Anal. Calcd. for C26H34O2N2: C 76.81, H 8.43, N 6.89.

12

Found: C 76.57, H 8.48, N 6.87.

13

3.5.6 1,4-Bis(butylamino)-2-hexyl-9,10-anthraquinone (4b’)

14

Following the procedure described in section 2.5, 3b’ (316 mg, 0.5 mmol) and n-butylamine (52.6

15

mL, 530 mmol) was co-dissolved in pyridine (50 mL). The mixture was kept at 50°C for five days.

16

After work-up and recrystallization 130 mg (0.30 mmol, 59.9%) of 4b’ was obtained (cf. Table 1). UV

17

(iPrOH) λmax (ε x 10-4, M-1.cm-1): 597 (1.25), 643 (1.21) nm. IR νmax/cm-1: 3065, 2956, 2923, 2872, 1742,

18

1606, 1558, 1504, 1456, 1377, 1257, 1185, 1132, 1105, 1017, 874, 798, 763, 723, 665, 638. 1H NMR

19

(400.13 MHz, CDCl3) 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

20

(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

21

(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

22

Hz, 3H), 0.90 (t, J = 7.1 Hz, 3H).13C NMR (100.63 MHz, CDCl3) δ: 184.05, 182.07, 148.03, 147.70,

23

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,

24

33.47, 31.69, 31.69, 29.67, 29.30, 22.61, 20.39, 20.30, 14.04, 13.87. Anal. Calcd. for C28H38O2N2: C

25

77.38, H 8.81, N 6.45. Found: C 77.34, H 9.04, N 6.44.

27

1

3.5.7 1,4-Bis(butylamino)-2-octyl-9,10-anthraquinone (4c’)

2

Following the procedure described in section 2.5, 3c’ (259 mg, 0.39 mmol) and of n-butylamine (39.5

3

mL, 400 mmol) was co-dissolved in pyridine (40 mL). The mixture was kept at 50°C for five days.

4

After work-up and recrystallization 123.1 mg (0.27 mmol, 67.9%) of 4c’ was obtained (cf. Table 1).

5

UV (iPrOH) λmax (ε x 10-4, M-1.cm-1): 597 (1.44), 643 (1.40) nm. IR νmax/cm-1: 3074, 2957, 2922, 2870,

6

1739, 1606, 1567, 1504, 1455, 1380, 1307, 1272, 1198, 1107, 1017, 877, 798, 766, 724, 665. 1H NMR

7

(400.13 MHz, CDCl3) 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

8

(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,

9

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),

10

1.01 (t, 7.4 Hz, 3H), 0.95 (t, 7.4 Hz, 3H), 0.88 (t, 7.0 Hz, 3H). 13C NMR (100.63 MHz, CDCl3) δ: 184.05,

11

182.07, 148.03, 147.70, 144.49, 134.65, 134.58, 132.29, 131.88, 126.41, 125.80, 123.02, 115.33,

12

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,

13

14.07, 13.87. Anal. Calcd. for C30H42O2N2: C 77.88, H 9.15, N 6.05. Found: C 77.73, H 9.27, N 6.08.

14

3.5.8 1,4-Bis(butylamino)-9,10-anthraquinone (4d’)

15

Following the procedure described in section 2.5, 3d’ (548 mg, 1 mmol) and of n-butylamine (98.9

16

mL, 1 mol) was co-dissolved in pyridine (100 mL). The mixture was kept at 50°C for five days. After

17

work-up and recrystallization 258.2 mg (0.74 mmol, 73.7%) of 4d’ was obtained (cf. Table 1). UV

18

(iPrOH) λmax (ε x 10-4, M-1.cm-1): 596 (0.78), 644 (0.96) nm. IR νmax/cm-1: 3072, 2961, 2928, 2855, 1717,

19

1641, 1552, 1518, 1464, 1393, 1343, 1270, 1163, 1134, 1055, 1017, 988, 949, 849, 797, 726, 666,

20

624. 1H NMR (400.13 MHz, CDCl3) δ: 10.82 (br.t, J =5.5 Hz, 2H), 8.35 (m, 2H), 7.68 (m, 2H), 7.24 (s,

21

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). 13C NMR (100.63

22

MHz, CDCl3) δ: 182.24, 146.28, 134.57, 131.88, 125.98, 123.57, 109.69, 42.61, 31.76, 20.36, 13.83.

23

Anal. Calcd. for C22H26O2N2: C 75.4, H 7.48, N 7.99. Found: C 75, H 7.76, N 7.73.

24

3.6 X-ray analysis

28

1

X-ray diffraction analysis of compound 4a’ was performed using a Bruker D8 Venture diffractometer

2

equipped with multilayer monochromator, Mo K/α INCOATEC micro focus sealed tube, Oxford

3

cooling system. Structure elucidation was accomplished by direct methods and refined by full-matrix

4

least-squares techniques. Non-hydrogen atoms were refined with anisotropic displacement

5

parameters. Hydrogen atoms were inserted at calculated positions and refined with riding model.

6

The following software was used: Bruker SAINT software package [35] using a narrow-frame

7

algorithm for frame integration, SADABS [36] for absorption correction, OLEX2 [37] for structure

8

solution, refinement, molecular diagrams and graphical user-interface, Shelxle [38] for refinement

9

and graphical user-interface SHELXS-2015 [39] for structure solution, SHELXL-2015 [39] for

10

refinement, Platon [40] for symmetry check. Experimental data, CCDC-Code, crystal data, data

11

collection

12

http://www.ccdc.cam.ac.uk/conts/retrieving.html) can be found in the Supplementary Information

13

section.

14

parameters

and

structure

refinement

details

(Available

online:

3.7 Computational details

15

All calculations were performed using the Gaussian 09 software package (Wallingford, CT, USA)

16

available at the Vienna Scientific Cluster (VSC). Figures were created with Avogadro 1.20, an open-

17

source molecular builder and visualization tool [41].

18

The structures of 1 ,1’, 2a, 2a’,3a, 3a’, 4a and 4a’ were subjected to geometry optimisation based on

19

the density functional theory (DFT) with the B3LYP functional and the 6-311++g(d,p) basis set. In

20

addition, the integration grid was set to ‘ultrafine’ and Grimme’s D3 dispersion correction was

21

employed. Frequency calculations with the optimized structures at the same level of theory were

22

used to guarantee the absence of imaginary frequencies.

23

Isopropanol as solvent was modelled with the Polarisable Continuum Model. The solvent was

24

included in all the calculations except for the one used to compare the simulated structure of 4a’

25

with the X-ray data. 29

1

Time dependent density functional theory was used to perform excited state calculations on the

2

optimized structures, which resulted in simulated UV-vis spectra. Respective calculations were

3

performed at the B3LYP/6-311++g(d,p) level of theory using isopropanol as solvent.

4

30

4. Conclusions In this work, a series of new 1-butylamino-2-alkyl and 1,4-bis(butylamino)-2-alkyl-9,10anthraquinone derivatives for supercritical carbon dioxide dyeing was successfully synthesized. Different from previous elaborate multi-step approaches towards similar 9,10-anthraquinone derivatives, a facile three-step synthesis is proposed that gives the desired products in good yield. It comprises of Marschalk alkylation of 1-hydroxy- and 1,4-dihydroxy-9,10-anthraquinone, subsequent (bis) tosylation and (bis) n-butylamination. While the bis-tosylated products 3a’-3d’ were accessible in good yields by common tosylation (TsCl, NEt3, ACN), mono tosylation of 2a-2c required the use of a phase transfer catalyst (TBAB) in biphasic medium (H2O/CH2Cl2) to obtain the desired products in good yield and purity. All obtained products were fully characterized. X-ray diffraction of compound 4a’ confirmed the absolute structure and configuration of the product. The results were in good agreement with that of quantum computational calculations. The latter also showed the impact of the different substituents on light absorption nicely and revealed the participation of the hydroxyl or amino groups in the HOMOs and LUMOs. These computational outcomes are in line with a previous study by Xiao et al. [31] on similar anthraquinone derived compounds. In this work, the simulated absorption spectra of 1,4-dihydroxy-9,10-anthraquinone (1’) and 1,4-bis(pentylamino)-9,10anthraquinone (alias ‘Oil Blue N’) as well as their molecular orbitals were examined amongst others. Matching our results, it was shown that the substituents at positions 1 and 4 are vital for the colour perception of the respective compounds. Similarly, there was good agreement between simulated and measured absorption spectra irrespective of the slightly bigger wavelength difference obtained by Xiao and coworkers (e.g. for 1’: 25 nm versus 13 nm in the present study) which are attributed to the different levels of theory employed for these calculations. Following preliminary successful dyeing experiments with selected wood and plastic samples, comprehensive investigation of scCO2 solubility of the synthesized dyes will be subject of a separate study.

31

Acknowledgements The financial support by FFG - The Austrian Research Promotion Agency through the BRIDGE project “Dyeing of massive wood mediated by supercritical CO2” (2016-2019, n°853234) is thankfully acknowledged. Authors are grateful to Julie Rodriguez who contributed calculation of the molar extinction coefficients. The computational results presented have been achieved using the Vienna Scientific Cluster (VSC). References [1] Drescher M, Jokisch A, Steiner R, Peek RD, Korte H. Untersuchungen zur Tiefenfärbung von Holz unter Verwendung von verdichtetem Kohlendioxid. Chemie Ingenieur Technik. 2005;77(4):436-41. [2] Jaxel J, Fontaine L, Krenke T, Hansmann C, Liebner F. Bio-inspired conformational lipophilization of wood for scCO2-assisted colouring with disperse dyes. J Supercrit Fluids. 2019;147:116-25. [3] Kjellow AW, Henriksen O. Supercritical wood impregnation. J Supercrit Fluids. 2009;50(3):297304. [4] Sahle-Demessie E, Levien KL, Morrell JJ. Impregnation of wood with biocides using supercritical fluid carriers. Innovations in Supercritical Fluids: American Chemical Society; 1995. p. 415-28. [5] Acda MN, Morrell JJ, Levien KL. Effect of process variables on supercritical impregnation of composites with tebuconazole. Wood Fiber Sci. 1997;29(3):282-90. [6] Morrell JJ, Levien KL. The Deposition of a Biocide in Wood-Based Material. In: Williams JR, Clifford AA, editors. Supercritical Fluid Methods and Protocols. Totowa, NJ: Humana Press; 2000. p. 227-33. [7] Acda MN, Morrell JJ, Levien KL. Supercritical fluid impregnation of selected wood species with tebuconazole. Wood Sci Technol. 2001;35(1):127-36. [8] Kang S-M, Levien KL, Morrell JJ. Supercritical fluid impregnation of wood with biocides using temperature reduction to induce deposition. Wood Sci Technol. 2005;39(5):328-38. [9] Kang SM, Levien KL, Morrell JJ. Effect of process variations during supercritical fluid impregnation on cyproconazole retention and distribution in Ponderosa pine sapwood. Wood Fiber Sci. 2006;38(1):64-73. [10] Henriksen O, Larsen T, Iversen SB, Felsvang K. Process for treatment of wood using a carrier fluid under high pressure without damaging the wood, US 7,807,224. In: Patent US, editor.2010. [11] Matsunaga M, Kataoka Y, Matsunaga H, Matsui H. A novel method of acetylation of wood using supercritical carbon dioxide. J Wood Sci. 2010;56(4):293-8. [12] Meints T, Hansmann C, Müller M, Liebner F, Gindl-Altmutter W. Highly effective impregnation and modification of spruce wood with epoxy-functional siloxane using supercritical carbon dioxide solvent. Wood Sci Technol. 2018. [13] Eastman SA, Lesser AJ, McCarthy TJ. Supercritical CO2-assisted, silicone-modified wood for enhanced fire resistance. J Mater Chem. 2009;44(5):1275-82. [14] Özcan AS, Özcan A. Adsorption behavior of a disperse dye on polyester in supercritical carbon dioxide. J Supercrit Fluids. 2005;35(2):133-9. [15] De Giorgi MR, Cadoni E, Maricca D, Piras A. Dyeing polyester fibres with disperse dyes in supercritical CO2. Dyes Pigm. 2000;45(1):75-9. [16] Hou A, Chen B, Dai J, Zhang K. Using supercritical carbon dioxide as solvent to replace water in polyethylene terephthalate (PET) fabric dyeing procedures. J Clean Prod. 2010;18(10–11):1009-14. [17] Banchero M. Supercritical fluid dyeing of synthetic and natural textiles – a review. Color Technol. 2013;129(1):2-17. [18] Gupta RB, Shim J-J. Solubility in supercritical carbon dioxide: CRC Press, 2006. 32

[19] de Melo MMR, Silvestre AJD, Silva CM. Supercritical fluid extraction of vegetable matrices: Applications, trends and future perspectives of a convincing green technology. J Supercrit Fluids. 2014;92:115-76. [20] Shimizu S, Abbott S. How entrainers enhance solubility in supercritical carbon dioxide. J Phys Chem B. 2016;120(15):3713-23. [21] Miyazaki K, Tabata I, Hori T. Relationship between colour fastness and colour strength of polypropylene fabrics dyed in supercritical carbon dioxide: effect of chemical structure in 1,4bis(alkylamino)anthraquinone dyestuffs on dyeing performance. Color Technol. 2011;128(1):60-7. [22] Sharghi H, Forghaniha A. Efficient Synthesis of a Range of 1-Hydroxy-2-(1-Alkyloxymethyl)-9,10Anthraquinone Derivatives. Iran J Chem Chem Eng. 1995;14(1):16-22. [23] Shamsipur M, Karami AR, Yamini Y, Sharghi H. Solubilities of some 1-hydroxy-9,10anthraquinone derivatives in supercritical carbon dioxide. J Supercrit Fluids. 2004;32(1–3):47-53. [24] Dreuw A, Head-Gordon M. Single-Reference ab Initio Methods for the Calculation of Excited States of Large Molecules. Chem Rev. 2005;105(11):4009-37. [25] Friesner RA, Berne BJ. Ab initio Quantum Chemistry: Methodology and Applications. Proceedings of the National Academy of Sciences of the United States of America. 2005;102(19):6648-53. [26] General introduction to the chemistry of dyes. Some Aromatic Amines, Organic Dyes, and Related Exposures. Lyon, France: IARC Working Group on the Evaluation of Carcinogenic Risk to Humans, International Agency for Research on Cancer; 2010. [27] Chang P, Lee K-H. Antitumor agents, 75. Synthesis of cytotoxic anthraquinones digiferruginol and morindaparvin-B. J Nat Prod. 1985;48(6):948-51. [28] Marschalk C. New method of introducing side chains into the anthraquinone nucleus. Bull Soc Chim Fr. 1936;3:1545. [29] Brown JR, Imam SH. 5 Recent Studies on Doxorubicin and its Analogues. In: Ellis GP, West GB, editors. Progress in Medicinal Chemistry: Elsevier; 1985. p. 169-236. [30] Zielske AG. (Tosyloxy)anthraquinones. Versatile synthons for the preparation of various aminoanthraquinones. J Org Chem. 1987;52(7):1305-9. [31] Xiao P, Dumur F, Graff B, Fouassier JP, Gigmes D, Lalevée J. Cationic and Thiol–Ene Photopolymerization upon Red Lights Using Anthraquinone Derivatives as Photoinitiators. Macromolecules. 2013;46(17):6744-50. [32] Mennucci B. Polarizable continuum model. Wiley Interdisciplinary Reviews: Computational Molecular Science. 2012;2(3):386-404. [33] Skyner RE, McDonagh JL, Groom CR, van Mourik T, Mitchell JBO. A review of methods for the calculation of solution free energies and the modelling of systems in solution. PCCP. 2015;17(9):6174-91. [34] Zollinger H. Carbonyl Dyes and Pigments. In: Zollinger H, editor. Color Chemistry: Synthesis, Properties and Applications of Organic Dyes and Pigments Wiley-VCH; 2004. p. 278-9. [35] Bruker. SAINT v8.37A Copyright (c). Bruker AXS; 2005-2018. [36] Sheldrick GM. SADABS. University of Göttingen, Germany.1996. [37] Dolomanov OV, Bourhis LJ, Gildea RJ, Howard JAK, Puschmann H. OLEX2: a complete structure solution, refinement and analysis program. J Appl Crystallogr. 2009;42(2):339-41. [38] Hübschle CB, Sheldrick GM, Dittrich B. ShelXle: a Qt graphical user interface for SHELXL. J Appl Crystallogr. 2011;44(Pt 6):1281-4. [39] Sheldrick GM. Crystal structure refinement with SHELXL. Acta Crystallogr Sect C: Cryst Struct Commun. 2015;71(Pt 1):3-8. [40] Spek A. Structure validation in chemical crystallography. Acta Crystallogr Sect D. 2009;65(2):14855. [41] Hanwell MD, Curtis DE, Lonie DC, Vandermeersch T, Zurek E, Hutchison GR. Avogadro: an advanced semantic chemical editor, visualization, and analysis platform. Journal of Cheminformatics. 2012;4(1):17. 33

Highlights: •

Three-step lipophilization of 9,10-anthraquinone dyes for improved scCO2 dyeing

•

Facile Marschalk alkylation used to introduced alkyl moieties in 2-position

•

Additional n-Butylamination of -OH groups (1 and 1,4) causes bathochromic shift

•

Structure elucidation (e.g., NMR, X-ray) and evaluation of spectroscopic properties

•

Good correlation between optimized simulation and X-ray crystallographic structure

Universität für Bodenkultur Wien University of Natural Resources and Life Sciences, Vienna

Assoc. Prof. Dipl.-Chem. Dr. rer. nat. habil. Falk Liebner Privatdozent of Biopolymer Materials Chemistry Institute for Chemistry of Renewable Resources Distinguished Professor at University of Aveiro, Portugal Invited Chair of Bioeconomy and Biorefinery Department of Chemistry Konrad-Lorenz-Straße 24 A-3430 Tulln an der Donau, Austria Phone: +43-1-47654 77413 [email protected]

Vienna 20. 10. 2019 Elsevier - Dyes and Pigments Editorial Office

Conflict of Interest

Dear Madam or Sir, On behalf of my co-authors I declare that there is no conflict of interest for the paper below: “Facile synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-anthraquinone dyes for improved supercritical carbon dioxide dyeing” by Julien Jaxel, Hassan Amer, Markus Bacher, Alexander Roller, Matthias Guggenberger, Nele Sophie Zwirchmayr, Christian Hansmann, Falk Liebner

Yours sincerely