Synthesis and photochemical properties of phenoxy derivatives of anthra[2,3-b]furan-5,10-dione

Article abstract of DOI:10.1134/S1070428008060134

Nucleophilic replacement of the hydroxy groups in ethyl 4,11-dihydroxy-2-methyl-5,10-dioxo-5,10-dihydroanthra[2,3-b]furan-3-carboxylate by chlorine upon treatment with phosphorus acid chlorides gave the corresponding 4(11)-chloro derivatives which were co

Full text of DOI:10.1134/S1070428008060134

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 6, pp. 855–862. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © A.E. Shchekotikhin, E.K. Shevtsova, Yu.N. Luzikov, V.A. Barachevskii, V.F. Traven’, 2008, published in Zhurnal Organicheskoi
Khimii, 2008, Vol. 44, No. 6, pp. 864–871.
Synthesis and Photochemical Properties of Phenoxy Derivatives
of Anthra[2,3-b]furan-5,10-dione
A. E. Shchekotikhina,b, E. K. Shevtsovaa, Yu. N. Luzikovb,
V. A. Barachevskiic, and V. F. Traven’a
a Mendeleev Russian University of Chemical Technology, Miusskaya pl. 9, Moscow, 125047 Russia
e-mail: traven@muctr.edu.ru
b Gauze Research Institute of Antibiotics, Moscow, Russia
c Photochemistry Center, Russian Academy of Sciences, Moscow, Russia
Received August 2, 2007
Abstract—Nucleophilic replacement of the hydroxy groups in ethyl 4,11-dihydroxy-2-methyl-5,10-dioxo-
5,10-dihydroanthra[2,3-b]furan-3-carboxylate by chlorine upon treatment with phosphorus acid chlorides gave
the corresponding 4(11)-chloro derivatives which were converted into photochromic ethyl 4(11)-phenoxy-2-
methyl-5,10-dioxo-5,10-dihydroanthra[2,3-b]furan-3-carboxylates. Photoinduced decomposition of the latter
leads to the formation of phenol and fluorescent hydroxyanthra[2,3-b]furandiones.
DOI: 10.1134/S1070428008060134
Anthraquinone derivatives are widely used in vari-
ous fields of chemistry, chemical technology, medi-
cine, technics, etc. [1]. Photochromic α-aryloxy deriva-
tives of anthraquinone and naphthacenequinone [2] are
promising materials for nanotechnology, microelec-
tronics, laser technics, and data storage and recording
systems. Fusion of a heterocyclic fragment to anthra-
quinone chromophore could strongly affect spectral
and photochemical properties of such compounds [3].
We have developed a scheme for the synthesis and
examined photochromic properties of phenoxy-substi-
tuted anthra[2,3-b]furan-5,10-dione derivatives.
gen-substituted compounds which were not reported
previously. As starting material we used accessible
ethyl 4,11-dihydroxy-2-methyl-5,10-dioxo-5,10-dihy-
droanthra[2,3-b]furan-3-carboxylate (I) prepared in
two steps from quinizarin and ethyl acetoacetate [4].
The hydroxy groups in molecule I can be replaced by
halogen atoms. Heating of ester I in POCl3 for 6 h
resulted in replacement of one hydroxy group by
chlorine atom with formation of a mixture of chloro
derivatives IIa and IIb in an overall yield of 35–40%
(Scheme 1). Under analogous conditions, 4,11-dihy-
droxyanthra[2,3-b]thiophene-5,10-dione gives rise to
the corresponding 4,11-dichloro derivative [5]; how-
ever, we detected no 4,11-dihalo-substituted products
even after prolonged heating of dihydroxyanthrafuran-
α-Aryloxyanthraquinones are generally synthesized
by nucleophilic replacement of halogen atoms by the
action of phenoxides. Therefore, the first step in the
synthesis of aryloxy derivatives of anthra[2,3-b]furan-
5,10-dione was preparation of the corresponding halo-
1
dione I in POCl3. According to the H NMR data,
the ratio of isomers IIa/IIb was about 3 : 1 (after
Scheme 1.
O
O
O
OH
O
X
OEt
Me
OEt
Me
POCl3, PCl5
O
O
O
OH
O
Y
I
IIa, IIb
X = OH, Y = Cl (a); X = Cl, Y = OH (b).
855

SHCHEKOTIKHIN et al.
856
Scheme 2.
O
O
O
O
O
Z
O
X
O
O
Cl
Cl
OEt
Me
OEt
Me
OEt
Me
PrI, K2CO3
DMF
POCl3, PCl5
O
O
O
Q
O
Y
IIIa, IIIb
IIa, IIb
IIIc
Z = OPr, Q = Cl (a); Z = Cl, Q = OPr (b).
chromatographic purification). By fractional crystal-
lization from toluene we succeeded in isolating indivi-
dual isomers IIa and IIb. Their H NMR spectra were
respect to the chlorine atom; ionization of that hydroxy
group by the action of base deactivates the halogen
atom toward nucleophilic replacement. To prevent
ionization of the hydroxy group chloro derivatives IIa
and IIb were subjected to alkylation with propyl iodide
in dimethylformamide in the presence of potassium
carbonate. We thus obtained 4(11)-chloro-11(4)-prop-
oxy derivatives IIIa and IIIb (Scheme 2).
1
fairly similar, while the 13C NMR spectra revealed
a considerable difference in the positions of the C4 and
C11 signals. In the 13C NMR spectrum of the major
isomer, the COH signal was located at δC 154.71 ppm,
while the COH carbon atom in the minor isomer
resonated at δC 143.92 ppm. The upfield shift of the
latter results from the presence of oxygen atom in the
ortho position [6]; therefore, the minor isomer was
assigned structure IIb.
The structure of propoxy derivatives IIIa and IIIb
was confirmed by NMR spectra. Compound IIIa
showed nuclear Overhauser effect between methylene
protons of the propoxy group and methylene protons of
the ester ethoxy group, indicating their spatial proxim-
ity. No analogous effect was observed in the spectrum
of IIIb; this means that the propoxy group in molecule
IIIb is attached to C11.
In the reaction of ethyl 4,11-dihydroxy-2-methyl-
5,10-dioxo-5,10-dihydroanthra[2,3-b]furan-3-carbox-
ylate (I) with more active phosphorus pentachloride in
a mixture with POCl3, replacement of hydroxy group
by chlorine was considerably faster (2–3 h at 40–
50°C), and halogen derivatives IIa and IIb were
obtained in a higher yield (50–60%). However, the
isomer ratio IIa/IIb approached 1:4, i.e., 4-chloro
derivative IIb was the major product. Thus variation of
the halogenating agent ensures some regioselectivity in
the formation of 4(11)-chloro-11(4)-hydroxy-2-meth-
yl-5,10-dioxo-5,10-dihydroanthra[2,3-b]furan-3-car-
boxylates IIa and IIb.
We detected no 4,11-dichloro derivative when com-
pound I was heated in a boiling PCl5–POCl3 mixture;
however, heating of monohalo derivatives IIa and IIb
or their mixture in PCl5–POCl3 at the boiling point
gave ethyl 4,11-dichloro-2-methyl-5,10-dioxoanthra-
[2,3-b]furan-3-carboxylate (IIIc) (Scheme 2). The
halogen atoms in compounds IIIa and IIIb are readily
replaced by phenoxy group on heating in molten phe-
nol in the presence of potassium carbonate at 70–80°C;
as a result, 4(11)-phenoxy-11(4)-propoxy derivatives
IVa and IVb are formed (Scheme 3). In the reaction
with 4,11-dichloroanthrafuran IIIc it was possible to
replace one or both chlorine atoms by phenoxy group,
depending on the conditions. The reaction of IIIc with
The chlorine atom in molecules IIa and IIb turned
out to be weakly reactive, and we failed to replace it by
phenoxy group. The reduced reactivity of compounds
IIa and IIb in SN2Ar processes results from the pres-
ence of a hydroxy group in the para position with
Scheme 3.
O
O
O
O
Z
O
X
OEt
Me
OEt
Me
PhOH, K2CO3
O
O
Q
O
Y
IIIa, IIIb
IVa, IVb
X = OPr, Y = OPh (a); X = OPh, Y = OPr (b).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 6 2008

SYNTHESIS AND PHOTOCHEMICAL PROPERTIES OF PHENOXY DERIVATIVES
857
Scheme 4.
O
O
O
O
Cl
O
O
X
OEt
Me
OEt
Me
PhOH, K2CO3
O
O
Cl
Y
IIIc
IVc, IVd
X = OPh, Y = Cl (c); X = Y = OPh (d).
phenol in melt at 60°C in the presence of K2CO3 gave
mainly one monophenoxy derivative IVc, whereas at
higher temperature ethyl 2-methyl-5,10-dioxo-4,11-bis-
(phenoxy)-5,10-dihydroanthra[2,3-b]furan-3-carbox-
ylate (IVd) was obtained (Scheme 4).
pattern are reversible. Irradiation of the photoinduced
forms in solution at λ 502 nm restores the initial state.
Alternate irradiation at λ 380 and 502 nm causes
multiple reversible phototransformations (Fig. 2).
However, recycling is accompanied by decrease in the
photoinduced optical density as a result of photo-
chemical decomposition (Fig. 2).
The structure of phenoxy derivatives IVa–IVd was
confirmed by NMR spectra. Unlike initial compounds
IIa, IIb, and IIIa–IIIc and other ethyl 2-methyl-5,10-
dioxo-5,10-dihydroanthra[2,3-b]furan-3-carboxylates
As in the case of phenoxynaphthacenequinones, the
observed variations in the spectral pattern may be
interpreted in terms of photoinduced rearrangement
involving isomerization of 4(11)-phenoxyanthra-
[2,3-b]furan-5,10-diones into the corresponding ana-
quinone structures, 5(10)-phenoxyanthra[2,3-b]furan-
4,10(5,11)-diones [2]. The long-wave absorption
maxima in the electronic spectra of photochromic
phenoxyanthra[2,3-b]furan-5,10-diones IVa–IVd are
displaced by 30 nm to the blue region, while the ab-
sorption maxima of their photoinduced forms are dis-
placed by 20 nm to the red region relative to the corre-
sponding maxima of analogous naphthacene-5,12-
quinone derivatives [7]. Thus the presence of a fused
1
[3], in the H NMR spectra of IVb–IVd in CDCl3 the
triplet signal from the methyl protons in the ester ethyl
group is displaced downfield by about 1.07 ppm due to
deshielding effect of the magnetically anisotropic
phenyl group in position 4 (ASIS effect). No analo-
gous effect was observed in the spectrum of compound
IVa having a phenoxy group in the 11-position. These
findings allowed us to assign compound IVc the
structure of 4-phenoxy derivative and to confirm once
more the structure of initial monochloro-substituted
compounds IIa and IIb.
The electronic absorption spectra of chloroanthra-
[2,3-b]furan-5,10-diones IIa and IIb showed that
replacement of hydroxy group in anthrafuran I by
chlorine atom induces a 60–70-nm blue shift of the ab-
sorption maximum. Chloro-, propoxy-, and phenoxy-
substituted anthra[2,3-b]furan-5,10-diones III and IV
absorb in the region λ 370–380 nm. 4(11)-Chloro-
11(4)-hydroxy derivatives IIa and IIb exhibit fluores-
cence in solution (λfl = 570 nm), while dichloro-,
propoxy-, and phenoxyanthra[2,3-b]furan-5,10-diones
III and IV do not possess fluorescent properties.
D
1.0
2
1
3
Like related phenoxy-substituted 5,12-naphthacene-
quinones [7], phenoxyanthra[2,3-b]furan-5,10-diones
IVa–IVd are photochromic compounds. Irradiation of
their solutions in toluene with filtered light at λ 380 nm
induced an appreciable red shift and increase in intens-
ity of the long-wave absorption maximum (see table).
The spectra of the photoinduced forms contained two
absorption bands in the region λ 480–510 nm (Fig. 1).
The observed photoinduced variations in the spectral
0.0
300
350
400
450
500
550 λ, nm
Fig. 1. Electronic absorption spectra of (1) anthra[2,3-b]-
furan-5,10-dione IVc, (2) its photoinduced form after ir-
radiation at λ 380 nm for 30, 90, 150, 210, and 360 s, and
(3) photodecomposition product; toluene, c = 5×10–5 M.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 6 2008

SHCHEKOTIKHIN et al.
858
Electronic absorption spectra of phenoxy-substituted anthra-
[2,3-b]furan-5,10-diones IVa–IVd and their photoinduced
forms and photodecomposition products and photocolora-
tion rate constants (k) in toluene (c = 5×10–5 M)
under irradiation with unfiltered UV light over a period
of 10–15 min (Fig. 3). Photodecomposition of IVc and
IVd also gave fluorescent products. Thus the nature of
substituents and their position in the chromophore core
strongly affect the rate of photodecomposition of
phenoxyanthra[2,3-b]furan-5,10-diones. In addition,
the rate of photodecomposition strongly depends on
the solvent nature. For example, the decomposition of
compounds IVa–IVd in chloroform and alcohols was
considerably faster.
λmax,a nm
Comp.
no.
k ×102,
s–1
initial photoinduced photodecomposition
form
379
376
370
372
form
product
IVa
IVb
IVc
IVd
475, 498
484, 506
486, 510
481, 504
(427), 446
(430), 448
(428), 444
()422, 442
1.1
1.8
1.4
1.5
Unlike phenoxynaphthacenequinones [2], solutions
of the photoinduced forms derived from anthra[2,3-b]-
furan-5,10-diones IVa–IVd in toluene or chloroform
underwent complete decoloration on storage for 24 h
in the dark. The absorption and fluorescence spectra of
the products were identical to those of the photode-
composition products. Moreover, addition of protic sol-
vents (e.g., alcohols) to solutions of the photoinduced
forms of IVa–IVd was found to considerably acceler-
ate the decoloration process.
a
Hereinafter, in parentheses are given the positions of inflection
points.
heterocyclic fragment considerably affects photochem-
ical properties of such compounds.
Photoinduced isomerization of propoxyphenoxyan-
thra[2,3-b]furan-5,10-diones IVa and IVb was accom-
panied by fluorescence in the region λ 560–570 nm.
A more detailed examination showed that the observed
fluorescence is not related to the formation of the ana-
quinone isomer: it originates from the photochemical
decomposition products. When the photoinduced
forms were irradiated at λ 502 or 380 nm, decrease in
the intensity of the long-wave absorption maxima was
accompanied by increase in the fluorescence intensity
at λ 570 nm. The photodecomposition of propoxy
derivatives IVa and IVb was especially fast, whereas
toluene solutions of the photoinduced forms of
11-chloro and 11-phenoxy derivatives IVc and IVd
were more stable: their decomposition occurred only
The photochemical transformations of phenoxy
derivative IVc were studied by 1H NMR spectroscopy.
Irradiation of a solution of IVc in CDCl3 at λ 380 nm
resulted in the formation of equimolar amounts of the
corresponding hydroxy compound IIa and phenol
(Scheme 5) as products of decomposition of the photo-
induced form. Compound IIa and phenol were iden-
tified by thin-layer chromatography using authentic
samples and the Pauli reagent as developer. These data
are consistent with the previously noted similarity of
the emission spectra of the photodecomposition prod-
ucts obtained from phenoxy-5,12-naphthacenequi-
nones and the corresponding hydroxy derivatives [8].
Obviously, the photodecomposition of phenoxy-sub-
stituted anthra[2,3-b]furan-5,10-diones involves photo-
chemical nucleophilic replacement of the phenoxy
group in the photoinduced form by hydroxy group.
D
1.0
λ 502 nm
λ 502 nm
λ 502 nm
1
We succeeded in recording the H NMR spectrum
of the photoinduced form derived from compound IVc
upon irradiation at λ 380 nm in C6D6. The spectrum
confirmed formation of ana-quinone structure Vc. The
rearrangement of 4-phenoxy derivative IVc into
5-phenoxy derivative Vc leads to an appreciable up-
field shift (δΔ = 0.25 ppm) of the triplet signal from
the methyl protons of the ester ethyl group and down-
field shift (δΔ = 0.24 ppm) of the 6-H signal. The ob-
served shifts are related to the deshielding effect of the
migrating magnetically anisotropic phenyl group on
spatially close groups, CH3 group in IVc and C6H in
Vc. The dark decoloration of photoinduced form Vc is
accompanied by appearance and increase in intensity
λ 380 nm
λ 380 nm
2000
λ 380 nm
0.0
0
1000
3000 τ, s
Fig. 2. Kinetics of reversible photochemical transformations
of phenoxyanthrafurandione IVc in toluene upon alternate
irradiation at λ 380 and 502 nm; the optical density was
measured at the absorption maximum of IVc, λ 485 nm.
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SYNTHESIS AND PHOTOCHEMICAL PROPERTIES OF PHENOXY DERIVATIVES
859
Scheme 5.
O
O
O
O
O
OPh
OPh
O
O
OH
Cl
OEt
Me
OEt
Me
OEt
hν1 (λ = 380 nm)
hν2 (λ = 502 nm)
hν, H2O
Me
–PhOH
O
O
O
Cl
IVc
O
Cl
O
Vc
IIa
of signals corresponding to hydroxy derivative IIa and
phenol.
Variation of the absorption spectra during phototrans-
formations (see table and Fig. 1) was studied at a half
of the maximal light source power. The kinetics of
photochromic transformations (Fig. 2) and photode-
composition were studied at the maximal light source
power. The progress of reactions and the purity of
products were monitored by thin-layer chromatog-
raphy on Silufol UV-254 and Kieselgel F254 (Merck)
plates. Kieselgel Merck 60 silica gel was used for
preparative chromatography.
Our results led us to conclude that, unlike phenoxy-
substituted 5,12-naphthacenequinones, photoinduced
forms derived from phenoxyanthra[2,3-b]furan-5,10-
diones are hydrolytically unstable and that they under-
go hydrolysis with water present in the solvent to give
the corresponding hydroxyanthrafurandiones and phe-
nol. The hydrolysis process is considerably accelerated
by irradiation. Taking into account that the hydrolysis
and photodecomposition products of the photoinduced
forms exhibit fluorescence, such compounds may be
interesting as materials for the design of data storage
systems. In addition, decomposition of the photoin-
duced colored forms of phenoxyanthra[2,3-b]furan-
5,10-diones to the corresponding fluorescent dye and
phenol attracts interest from the viewpoint of nano-
technology for creation of photocontrolled composi-
tions. However, practical implementation of the results
of the present work requires further study on phenoxy-
anthra[2,3-b]furan-5,10-diones, specifically on the
effect of fused heterocyclic fragment and functional
groups therein on the photochemical and spectral
properties of these compounds.
Ethyl 11-chloro-4-hydroxy-2-methyl-5,10-dioxo-
5,10-dihydroanthra[2,3-b]furan-3-carboxylate
(IIa). A solution of 400 mg (1.1 mmol) of ester I in
15 ml of phosphoryl chloride was heated for 6 h at the
boiling point. The mixture was cooled to room tem-
perature and poured onto ice under stirring. After 1 h,
the mixture was neutralized to pH 7 by carefully
adding sodium carbonate and was stirred overnight.
I
200
150
3
EXPERIMENTAL
100
1
The H and 13C NMR spectra were recorded on
a Varian VXR-400 spectrometer at 400 MHz using
tetramethylsilane as internal reference. The mass spec-
tra (electron impact, 70 eV) were obtained on a Fin-
nigan MAT SSQ 710 mass spectrometer with direct
sample admission into the ion source (ion source
temperature 150°C, batch inlet probe temperature up to
350°C). The electronic absorption spectra were meas-
ured on a Varian Cary 50 Bio spectrophotometer. The
fluorescence spectra were recorded on a Varian Cary
Eclipse spectrofluorimeter. Photochemical studies
were performed using a Namamatsu Spot Light Source
LC-4. The required wavelengths were isolated using
UFS-8 and BS-8 composite glass filters (λ 380 nm) or
ZhS-18, SZS-20, and SZS-22 filters (λ 502 nm).
50
2
1
0
500
550
600
650
700
λ, nm
Fig. 3. Fluorescence spectra in toluene (c = 5×10–5 M) of
(1) initial phenoxyanthrafurandione IVc (excitation at the
absorption maximum at λ 380 nm), (2) ana-quinoid photo-
induced form Vc generated by irradiation of compound IVc
at λ 380 nm over a period of 360 s (excitation at the absorp-
tion maximum at λ 502 nm), and (3) photodecomposition
product obtained by irradiation of Vc with unfiltered light
for 150, 600, and 900 s (excitation at the absorption maxi-
mum at λ 440 nm).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 6 2008

SHCHEKOTIKHIN et al.
860
The precipitate containing compounds IIa and IIb was
filtered off and subjected to column chromatography
on silica gel using toluene–diethyl ether (1:0 to 10:1)
as eluent. The product was recrystallized twice from
toluene. Yield 83 mg (19%), orange crystals, mp 220–
222°C. UV spectrum (EtOH), λmax, nm (logε): 204
(4.3), (238), 253 (4.5), 265 (4.5), 272 (4.5), (285), 322
(3.5), (401), 420 (3.9), 435 (3.9), (458). 1H NMR spec-
trum, δ, ppm: in CDCl3: 1.44 t (3H, CH3, J = 7.1 Hz),
2.77 s (3H, CH3), 4.42 q (2H, OCH2, J = 7.1 Hz),
7.77–7.82 m (2H, 7-H, 8-H), 8.22–8.26 m (2H, 6-H,
9-H), 14.63 s (1H, OH); in C6D6: 1.13 t (3H, CH3, J =
7.1 Hz), 2.26 s (3H, CH3), 4.23 q (2H, OCH2, J =
7.1 Hz), 7.00–7.05 m (2H, 7-H, 8-H), 8.07–8.18 m
(2H, 6-H, 9-H). 13C NMR spectrum (CDCl3), δC, ppm:
187.80 (C=O), 180.91 (C=O), 164.37 (COO), 162.09
(C), 158.31 (C), 154.19 (C), 134.22 (C), 124.95 (C),
120.17 (C), 112.73 (C), 112.22 (C), 112.11 (C), 134.58
(CH), 133.80 (CH), 127.37 (CH), 126.56 (CH), 61.41
(CH2), 14.49 (CH3), 14.16 (CH3). Mass spectrum, m/z
(Irel, %): 384 (100) [M]+, 356 (18), 339 (85) [M –
OC2H5]+, 321 (22). Found, %: C 62.43; H 3.41.
C20H13ClO6. Calculated, %: C 62.42; H 3.38. M 384.77.
C 62.40; H 3.42. C20H13ClO6. Calculated, %: C 62.42;
H 3.38. M 384.77.
Ethyl 11-chloro-2-methyl-5,10-dioxo-4-propoxy-
5,10-dihydroanthra[2,3-b]furan-3-carboxylate
(IIIa). Powdered potassium carbonate, 0.73 g
(5.3 mmol), was added to a solution of 200 mg
(0.47 mmol) of ester IIa in 10 ml of DMF, 0.4 ml
(4.0 mmol) of propyl iodide was then added, and the
mixture was stirred for 1.5 h on heating at 100°C. The
mixture was cooled to room temperature, the precip-
itate was filtered off, and the filtrate was acidified with
5% hydrochloric acid and extracted with ethyl acetate.
The extract was washed with water, dried, and evapo-
rated, and the residue was purified by column chroma-
tography on silica gel using toluene as eluent, followed
by recrystallization from hexane. Yield 150 mg (75%),
yellow crystals, mp 157–158°C. UV spectrum (EtOH),
λmax, nm (log ε): 244 (4.3), 272 (4.5), 374 (3.7).
1H NMR spectrum (CDCl3), δ, ppm: 1.02 t (3H, CH3,
J = 7.4 Hz), 1.43 t (3H, CH3, J = 7.1 Hz), 1.93–2.01 m
(2H, CH2), 2.75 s (3H, CH3), 4.03 t (2H, OCH2, J =
7.1 Hz), 4.44 q (2H, OCH2, J = 7.1 Hz), 7.72–7.77 m
(2H, 7-H, 8-H), 8.17–8.21 m (2H, 6-H, 9-H). 13C NMR
spectrum (CDCl3), δC, ppm: 182.77 (C=O), 182.01
(C=O), 164.03 (COO), 162.61 (C), 154.02 (C), 153.67
(C), 134.32 (C), 127.69 (C), 126.31 (C), 125.89 (C),
123.79 (C), 114.34 (C), 112.07 (C), 133.76 (CH),
133.41 (CH), 126.73 (CH), 126.60 (CH), 78.14 (CH2),
61.83 (CH2), 23.11 (CH2), 14.33 (CH3), 14.08 (CH3),
10.27 (CH3). Mass spectrum, m/z (Irel, %): 426 (10)
[M]+, 338 (15) [M – C3H7 – OC2H5]+, 163 (22), 87
(18), 75 (16), 50 (7), 43 (100) [C3H7]+. Found, %:
C 64.70; H 4.49. C23H19ClO6. Calculated, %: C 64.71;
H 4.45. M 426.85.
Ethyl 4-chloro-11-hydroxy-2-methyl-5,10-dioxo-
5,10-dihydroanthra[2,3-b]furan-3-carboxylate (IIb).
A mixture of 400 mg (1.1 mmol) of ester I, 15 ml of
POCl3, and 1.5 g (7.3 mmol) of PCl5 was heated for
2.5 h at 50°C. The mixture was cooled to room tem-
perature and poured onto ice under stirring. After 1 h,
the mixture was neutralized to pH 7 by carefully ad-
ding sodium carbonate and was stirred overnight. The
precipitate containing compounds IIa and IIb was
filtered off and subjected to column chromatography
on silica gel using toluene–diethyl ether (1:0 to 10:1)
as eluent. The product was recrystallized from toluene.
Yield 156 mg (37%), orange crystals, mp 236–237°C.
1H NMR spectrum (CDCl3), δ, ppm: 1.44 t (3H, CH3,
J = 7.1 Hz), 2.67 s (3H, CH3), 4.46 q (2H, OCH2, J =
7.1 Hz), 7.74–7.80 m (2H, 7-H, 8-H), 8.21–8.24 m
Ethyl 4-chloro-2-methyl-5,10-dioxo-11-propoxy-
5,10-dihydroanthra[2,3-b]furan-3-carboxylate
(IIIb) was synthesized as described above for com-
pound IIIa using ester IIb as initial compound. Yield
80%, yellow crystals, mp 119–121°C. UV spectrum
(EtOH), λmax, nm (logε): 244 (4.3), 273 (4.5), 379
13
(2H, 6-H, 9-H), 14.01 s (1H, OH). C NMR spectrum
1
(CDCl3), δC, ppm: 188.30 (C=O), 181.13 (C=O),
163.38 (C), 163.14 (COO), 148.81 (C), 143.92 (C),
134.72 (C), 132.93 (C), 132.06 (C), 120.30 (C), 113.52
(C), 113.64 (C), 134.91 (CH), 133.62 (CH), 127.66
(CH), 126.26 (CH), 61.56 (CH2), 13.40 (CH3), 13.38
(CH3). Mass spectrum, m/z (Irel, %): 384 (100) [M]+,
356 (36), 339 (63) [M – OC2H5]+, 321 (22), 305 (20),
199 (8), 163 (38), 156 (7), 105 (7), 87 (13), 82 (17), 50
(12), 43 (29). UV spectrum (EtOH), λmax, nm (logε):
204 (4.4), (239), 251 (4.5), (268), 274 (4.5), (289),
(320), (395), 410 (3.9), 424 (3.9), 445. Found, %:
(3.7). H NMR spectrum (CDCl3), δ, ppm: 1.13 t (3H,
CH3, J = 7.4 Hz), 1.45 t (3H, CH3, J = 7.2 Hz), 1.95–
2.01 m (2H, CH2), 2.67 s (3H, CH3), 4.35 t (2H, OCH2,
J = 6.7 Hz), 4.47 q (2H, OCH2, J = 7.2 Hz), 7.71–
7.74 m (2H, 7-H, 8-H), 8.13–8.18 m (2H, 6-H, 9-H).
13C NMR spectrum (CDCl3), δC, ppm: 182.84 (C=O),
181.95 (C=O), 163.24 (C), 162.59 (COO), 148.47 (C),
144.53 (C), 134.19 (C), 134.05 (C), 131.81 (C), 127.59
(C), 126.56 (C), 123.55 (C), 121.92 (C), 113.05 (C),
133.49 (CH), 133.43 (CH), 126.69 (CH), 126.27 (CH),
76.94 (CH2), 61.79 (CH2), 23.41 (CH2), 14.05 (CH3),
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SYNTHESIS AND PHOTOCHEMICAL PROPERTIES OF PHENOXY DERIVATIVES
861
13.76 (CH3), 10.26 (CH3). Mass spectrum, m/z
(Irel, %): 426 (57) [M]+, 397 (11), 384 (12), 356 (7),
339 (10) [M – C3H6 – OC2H5]+, 191 (8), 163 (29), 87
(9), 76 (14), 50 (6), 43 (100) [C3H7]+. Found, %:
C 64.73; H 4.44. C23H19ClO6. Calculated, %: C 64.71;
H 4.45. M 426.85.
201 (4.5), (210), 245 (4.4), 271 (4.5), 379 (3.8).
1H NMR spectrum (CDCl3), δ, ppm: 1.06 t (3H, CH3,
J = 7.5 Hz), 1.41 t (3H, CH3, J = 7.1 Hz), 1.90–2.02 m
(2H, CH2), 2.60 s (3H, CH3), 4.07 t (2H, OCH2, J =
7.3 Hz), 4.44 q (2H, OCH2, J = 7.1 Hz), 6.82 d (2H,
Harom, J = 8.8 Hz), 7.06 t (1H, Harom, J = 7.3 Hz), 7.26–
7.3 m (2H, Harom), 7.64–7.71 m (2H, 7-H, 8-H), 8.20–
8.25 m (2H, 6-H, 9-H). Mass spectrum, m/z (Irel, %):
484 (15) [M]+, 442 (30) [M – C3H6]+, 409 (10), 396
(53), 339 (8), 319 (15), 283 (8), 255 (9), 226 (8), 198
(10), 163 (13), 151 (11), 128 (10), 105 (15), 87 (9), 77
(75) [Ph]+, 51 (30), 43 (100) [C3H7]+. Found, %:
C 71.89; H 4.99. C29H24O7. Calculated, %: C 71.90;
H 4.96. M 484.50.
Ethyl 4,11-dichloro-2-methyl-5,10-dioxo-5,10-di-
hydroanthra[2,3-b]furan-3-carboxylate (IIIc). Phos-
phoryl chloride, 12.0 ml, was added to 300 mg
(0.78 mmol) of a mixture of compounds IIa and IIb,
1.0 g (4.8 mmol) of PCl5 was added, and the mixture
was heated for 3 h at the boiling point, cooled to room
temperature, and poured onto ice under stirring. After
1 h, the mixture was neutralized to pH 7 by carefully
adding sodium carbonate and was stirred overnight.
The precipitate was filtered off and subjected to
column chromatography on silica gel using toluene–
diethyl ether (1:0 to 10:1) as eluent. The product was
recrystallized from toluene–heptane (1 :1). Yield
172 mg (55%), mp 173–174°C. UV spectrum (EtOH),
λmax, nm (log ε): 243 (4.1), 274 (4.5), 367 (3.6).
1H NMR spectrum (CDCl3), δ, ppm: 1.44 t (3H, CH3,
J = 7.1 Hz), 2.71 s (3H, CH3), 4.48 q (2H, OCH2, J =
7.1 Hz), 7.75–7.79 m (2H, 7-H, 8-H), 8.18–8.21 m
(2H, 6-H, 9-H). 13C NMR spectrum (CDCl3), δC, ppm:
182.09 (C=O), 181.98 (C=O), 164.06 (COO), 162.83
(C), 152.15 (C), 134.21 (C), 133.79 (C), 130.46 (C),
128.42 (C), 128.03 (C), 126.84 (C), 117.91 (C), 113.37
(C), 134.06 (CH), 133.80 (CH), 126.91 (CH), 126.70
(CH), 117.91 (CH), 61.99 (CH2), 14.11 (CH3), 13.96
(CH3). Mass spectrum, m/z (Irel, %): 402 (10) [M]+, 357
(7) [M – OC2H5]+, 238 (9), 210 (54), 174 (100), 164
(22), 151 (26), 133 (28), 122 (20), 105 (76), 98 (42),
92 (10), 87 (52), 76 (82), 63 (10), 50 (50), 43 (84).
Found, %: C 59.57; H 3.01. C20H12Cl2O5. Calculated,
%: C 59.55; H 2.98. M 403.21.
Compounds IVb–IVd were synthesized in a similar
way.
Ethyl 2-methyl-5,10-dioxo-4-phenoxy-11-prop-
oxy-5,10-dihydroanthra[2,3-b]furan-3-carboxylate
(IVb) was synthesized from ester IIIb. Yield 62%,
light yellow crystals, mp 126–127°C. UV spectrum
(EtOH), λmax, nm (logε): 202 (4.3), (211), 244 (4.4),
1
271 (4.5), 377 (3.8). H NMR spectrum (CDCl3), δ,
ppm: 1.07 t (3H, CH3, J = 6.8 Hz), 1.16 t (3H, CH3,
J = 7.2 Hz), 2.00–2.07 m (2H, CH2), 2.73 s (3H, CH3),
4.07 q (2H, OCH2, J = 7.2 Hz), 4.40 t (2H, OCH2, J =
6.8 Hz), 6.80 d (2H, Harom, J = 8.8 Hz), 6.94 t (1H,
Harom, J = 7.2 Hz), 7.21–7.27 m (2H, Harom), 7.65–
7.72 m (2H, 7-H, 8-H), 8.05–8.22 m (2H, 6-H, 9-H).
Mass spectrum, m/z (Irel, %): 484 (8) [M]+, 442 (7)
[M – C3H6]+, 396 (7) [M – C3H7 – OC2H5]+, 163 (7),
105 (8), 77 (45) [Ph]+, 51 (24), 43 (100) [C3H7]+.
Found, %: C 71.92; H 4.98. C29H24O7. Calculated, %:
C 71.90; H 4.96. M 484.50.
Ethyl 11-chloro-2-methyl-5,10-dioxo-4-phenoxy-
5,10-dihydroanthra[2,3-b]furan-3-carboxylate (IVc)
was synthesized from ester IIIc; the mixture was
heated at 60°C. Yield 64%, light yellow crystals,
mp 228–229°C. UV spectrum (EtOH), λmax, nm (logε):
202 (4.4), (212), 244 (4.2), 272 (4.5), 369 (3.7).
1H NMR spectrum, δ, ppm: in CDCl3: 1.07 t (3H, CH3,
J = 7.1 Hz), 2.77 s (3H, CH3), 4.08 q (2H, OCH2, J =
7.1 Hz), 6.81 d (2H, Harom, J = 7.8 Hz), 7.01 t (1H,
Harom, J = 7.3 Hz), 7.23–7.28 m (2H, Harom), 7.62–
7.69 m (2H, 7-H, 8-H), 8.18–8.21 m (2H, 6-H, 9-H); in
C6D6: 0.79 t (3H, CH3, J = 7.1 Hz), 2.21 s (3H, CH3),
3.88 q (2H, OCH2, J = 7.1 Hz), 6.80–7.09 m (7H,
C6H5, 7-H, 8-H), 7.91 d (1H, 6-H, J = 7.5 Hz), 8.12 d
(1H, 9-H, J = 7.7 Hz). 13C NMR spectrum (CDCl3), δC,
ppm: 182.31 (C=O), 180.83 (C=O), 165.88 (COO),
162.27 (C), 158.90 (C), 153.82 (C), 146.91 (C), 133.98
(C), 133.81 (C), 127.80 (C), 126.13 (C), 124.36 (C),
Ethyl 2-methyl-5,10-dioxo-11-phenoxy-4-prop-
oxy-5,10-dihydroanthra[2,3-b]furan-3-carboxylate
(IVa). A mixture of 100 mg (0.23 mmol) of ester IIIa,
3.0 g (31.9 mmol) of phenol, and 150 mg (1.1 mmol)
of potassium carbonate was heated for 30–60 min at
80–90°C. When the reaction was complete (TLC), the
mixture was diluted with toluene and poured into
water. The product was extracted into warm toluene,
the extract was washed with a 5% solution of sodium
hydroxide, water, and a saturated solution of sodium
chloride, dried, and evaporated. The dry residue was
purified by column chromatography on silica gel using
toluene as eluent, followed by recrystallization from
hexane. Yield 65 mg (58%), light yellow crystals,
mp 122–123°C. UV spectrum (EtOH), λmax, nm (logε):
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 6 2008

SHCHEKOTIKHIN et al.
862
116.14 (C), 111.96 (C), 133.89 (CH), 133.55 (CH),
129.47 (2 CH), 126.82 (CH), 126.69 (CH), 121.81
(CH), 114.66 (2CH), 61.48 (CH2), 14.45 (CH3), 13.79
(CH3). Mass spectrum, m/z (Irel, %): 460 (20) [M]+, 415
(13) [M – OC2H5]+, 387 (9) [M – CO2C2H5]+, 339 (8),
311 (7), 283 (7), 239 (15), 207 (7), 199 (10), 175 (11),
163 (25), 149 (12), 105 (14), 98 (7), 87 (8), 77 (100)
[Ph]+, 65 (9), 51 (58), 43 (53). Found, %: C 67.73;
H 3.66. C26H17ClO6. Calculated, %: C 67.75; H 3.69.
M 460.86.
Ethyl 11-chloro-2-methyl-4,10-dioxo-5-phenoxy-
4,10-dihydroanthra[2,3-b]furan-3-carboxylate (Vc).
A solution of 3 mg (0.007 mmol) of ester IVc in 1.0 ml
of C6D6 was irradiated at λ 380 nm (filtered light) over
1
a period of 1.5 h, and H NMR spectrum of the solu-
tion was recorded, δ, ppm: 1.03 t (3H, CH3, J =
7.1 Hz), 2.11 s (3H, CH3), 4.08 q (2H, OCH2, J =
7.1 Hz), 6.80–7.06 m (7H, Ph, 7-H, 8-H), 7.67 d (1H,
6-H, J = 7.3 Hz), 8.32 d (1H, 9-H, J = 7.7 Hz).
REFERENCES
Ethyl 2-methyl-5,10-dioxo-4,11-diphenoxyan-
thra[2,3-b]furan-3-carboxylate (IVd) was synthe-
sized from ester IIIc. Yield 53%, light yellow crystals,
mp 225–227°C. UV spectrum (EtOH), λmax, nm (logε):
205 (4.5), (213), 243 (4.3), 270 (4.5), 372 (3.6).
1H NMR spectrum (CDCl3), δ, ppm: 1.08 t (3H, CH3,
J = 7.1 Hz), 2.63 s (3H, CH3), 4.06 q (2H, OCH2, J =
7.1 Hz), 6.87 d (2H, Harom, J = 8.8 Hz), 6.98 d (2H,
1. Gorelik, M.V., Khimiya antrakhinonov i ikh proizvodnykh
(Chemistry of Anthraquinones and Their Derivatives),
Moscow: Khimiya, 1983, p. 15.
2. Barachevsky, V.A., Organic Photochromic and Thermo-
chromic Compounds, Crano, J.C. and Guglielmetti, R.J.,
New York: Kluwer Academic/Plenum, 1999, p. 267.
3. Shchekotikhin, A.E., Shevtsova, E.K., and Traven’, V.F.,
Harom, J = 8.7 Hz), 7.01 t (1H, Harom, J = 7.3 Hz), 7.09 t
Russ. J. Org. Chem., 2007, vol. 43, p. 1686.
(1H, Harom, J = 7.3 Hz), 7.25–7.36 m (4H, Harom), 7.64–
7.68 m (2H, 7-H, 8-H), 8.03–8.11 m (2H, 6-H, 9-H).
13C NMR spectrum (CDCl3), δC, ppm: 181.73 (C=O),
180.39 (C=O), 165.85 (COO), 162.50 (C), 158.99 (C),
158.01 (C), 150.54 (C), 145.23 (C), 137.28 (C), 134.11
(C), 128.00 (C), 124.09 (C), 123.54 (C), 111.83 (C),
97.66 (C), 133.76 (CH), 133.54 (CH), 129.70 (2CH),
129.53 (2 CH), 126.95 (CH), 126.61 (CH), 122.65
(CH), 121.86 (CH), 115.07 (2CH), 114.66 (2CH),
61.52 (CH2), 14.42 (CH3), 13.82 (CH3). Mass spec-
trum, m/z (Irel, %): 518 (7) [M]+, 105 (11), 77 (100)
[Ph]+, 65 (7), 51 (43), 43 (30). Found, %: C 74.10;
H 4.24. C32H22O7. Calculated, %: C 74.13; H 4.25.
M 518.51.
4. Gorelik, M.V. and Mishina, E.V., Zh. Org. Khim., 1983,
vol. 19, p. 2185.
5. Fischer-Reimann, E., EP Patent no. 592366, 1993; Chem.
Abstr., 1994, vol. 121, no. 108509b.
6. Pretsch, E., Bühlmann, P., and Affolter, C., Structure
Determination of Organic Compounds: Tables of Spectral
Data, Berlin: Springer, 2000, 3rd ed. Translated under the
title Opredelenie stroeniya organicheskikh soedinenii,
Moscow: Mir, 2006, p. 115.
7. Sokolik, N.T. and Pisulina, L.P., Zh. Nauch. Prikl.
Fotogr., 1998, vol. 43, p. 59.
8. Belaits, I.L., Sokolik, N.T., Parshutkin, A.A., Samsono-
va, L.P., and Gerasimenko, Yu.E., Zh. Fiz. Khim., 1986,
vol. 60, p. 640.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 6 2008