Synthesis and structure of 2-phenylanthra[9,1-bc]pyrrol-6-one

Article abstract of DOI:10.1134/S107042801006014X

Reduction of anti-1-benzoylanthraquinone oxime gave 2-phenylanthra[9,1-bc] pyrrol-6-one whose structure was determined by X-ray analysis. The molecule of 2-phenylanthra[9,1-bc]pyrrol-6-one is almost planar, and its crystalline structure is characterized b

Full text of DOI:10.1134/S107042801006014X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 6, pp. 866–870. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © Ya.A. Chirkova, V.Ya. Denisov, Yu.V. Gatilov, I.Yu. Bagryanskaya, T.V. Rybalova, 2010, published in Zhurnal Organicheskoi
Khimii, 2010, Vol. 46, No. 6, pp. 871–874.
Synthesis and Structure of 2-Phenylanthra[9,1-bc]pyrrol-6-one
Ya. A. Chirkovaa, V. Ya. Denisova, Yu. V. Gatilovb, I. Yu. Bagryanskayab, and T. V. Rybalovab
a Kemerovo State University, ul. Krasnaya 6, Kemerovo, 650043 Russia
e-mail: orgchem@kemsu.ru
b Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
Received September 10, 2009
Abstract—Reduction of anti-1-benzoylanthraquinone oxime gave 2-phenylanthra[9,1-bc]pyrrol-6-one whose
structure was determined by X-ray analysis. The molecule of 2-phenylanthra[9,1-bc]pyrrol-6-one is almost
planar, and its crystalline structure is characterized by head-to-tail chains formed via intermolecular hydrogen
bonds N–H···O.
DOI: 10.1134/S107042801006014X
9,10-Anthraquinone derivatives attract strong in-
terest for both science and technics. They are tradi-
tionally used for the manufacture of synthetic dyes, but
in the recent time 9,10-anthraquinones have found new
applications, in particular as biologically active com-
pounds, analytical reagents, luminophores, compo-
nents of liquid crystalline compositions, photographic
materials, etc. [1]. The 2-phenylanthra[9,1-bc]pyrrol-6-
one system (A) is a peri-fused antrhaquinone deriva-
tive with 1,10-anthraquinoid structure. The presence of
a fused pyrrole ring and anthrone fragment with un-
usual ana-quinoid bond configuration suggests high
reactivity of such system.
reported long ago. Sholl et al. [2] showed that anthra-
[9,1-bc]pyrrole derivatives can be obtained by reduc-
tion of 1-aroylanthraquinonone oximes. However, the
products were assigned anthroxyl radical structure B,
and later, aminyl radicals C [3]. According to [4, 5],
such radicals are generated by reduction of 1-cyano-
anthraquinone or in the cyclization of 1-aminomethyl
derivatives of 2-hydroxyanthraquinone which are ob-
tained in turn by alkaline hydrolysis of 1-phthalimido-
methyl- or trichloroacetylaminomethyl-2-hydroxyan-
thraquinones. After repeated experiments, Sholl and
Muller [6] concluded that the reduction products of
1-aroylanthraquinone oximes are non-radical species
and that they have structure A with 1,10-anthraquinoid
bond distribution; however, no rigorous proofs for the
First attempts to synthesize anthra[9,1-bc]pyrrol-6-
ones with no substituent on the nitrogen atom were
Ar
Ar
Ar
·
HN
HN
N
·
O
O
OH
A
B
C
O
O
O
N
COPh
N
COPh
O
OH
HO
OH
Ph
N
I
II
III
866

SYNTHESIS AND STRUCTURE OF 2-PHENYLANTHRA[9,1-bc]PYRROL-6-ONE
867
Scheme 1.
Ph
O
Ph
O
O
CrO3
+
PhCH=CH2
+
(CH2O)n
O
O
IV
V
VI
O
O
O
O
N
NH2OH
+
+
N
COPh
OH
COPh
HO
Ph
N
OH
I
III
II
Ph
HN
[H]
I
O
VII
[H] = Zn + NH3 (EtOH), NaBH4.
assigned structure were given. Gorelik and Alimova
[7] made an attempt to reproduce these results, but
no success was achieved, and the authors followed
another way. In keeping with more recent data [8],
reduction of oximes gives rise to unidentified violet
products. As shown in [6], crude 1-aroylanthraquinone
monooxime is a mixture of three isomers, anti-9-oxime
I, syn-9-oxime II, and anti-oxime III. Anthrapyrrole A
is formed by reduction of only oximes I and II,
whereas oxime III is converted into anthrapyrrole only
under severe conditions.
1-benzoylanthraquinone decreased. With a view to im-
prove the yield of 1-benzoylanthraquinone, we utilized
a different procedure. As starting compound we used
anthrone (IV) which was subjected to condensation
with styrene and paraformaldehyde to obtain 1-phenyl-
benzanthrone (V) (yield 67%) [9]. Compound V was
oxidized with chromium(VI) oxide in acetic acid at
100–110°C, and 1-benzoylanthraquinone (VI) was
thus synthesized in 77% yield [10] (Scheme 1). With
a view to obtain isomeric 1-benzoylanthraquinone
oximes, a mixture of compound VI, hydroxylamine
hydrochloride, sodium carbonate, and alcohol was
heated under reflux. Crystals of pure oxime I separated
from the hot reaction mixture (yield 30%), and the
mother liquor contained a mixture of oximes I–III
which were separated by fractional recrystallization
first from alcohol and then from benzene. The overall
yield of oxime I was 45%, and the yields of oximes II
and III were 2 and 4%, respectively.
The goal of the present work was to reliably estab-
lish the structure of products formed by reduction of
1-aroylanthraquinone oximes. While performing
studies in this line, we leaned on the above listed
results, but some changes were introduced. Sholl and
Muller [6] proposed to obtain 1-aroylanthraquinone
oximes by oximation of 1-aroylanthraquinones synthe-
sized by Friedel–Crafts acylation of benzene or other
arenes with 9,10-dioxo-9,10-dihydroanthracene-1-car-
bonyl chloride. We tried to reproduce Sholl’s proce-
dure and obtained 1-benzoylanthraquinone in 50%
yield together with blue 10β-phenyl-6H-anthra[9,1-dc]-
furan-2,6-dione (50%); in this case, prolonged reaction
favored formation of the latter, while the yield of
Oxime I was then subjected to reduction. Appro-
priate reduction conditions included the use of zinc in
aqueous–alcoholic ammonia and sodium tetrahydrido-
borate. The reduction product displayed no paramag-
netic properties and was assigned the structure of
2-phenylanthra[9,1-bc]pyrrol-6-one (VII). The yield of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 6 2010

CHIRKOVA et al.
868
Table 1. Bond lengths in the molecule of 2-phenylanthra[9,1-bc]pyrrol-6-one (VII)
Bond
d, Å
Bond
d, Å
Bond
d, Å
N1– C2
N1– C10b
O1– C6
C2a– C3
C2a– C10s
C2a– C2
C2– C11
C3– C4
1.370(12)
1.374(8)0
1.270(7)0
1.410(13)
1.418(11)
1.419(9)0
1.454(10)
1.376(10)
1.405(13)
C5a– C10s
C5a– C5
C5a– C6
C6a– C7
C6a– C10a
C6a– C6
C7– C8
1.382(9)0
1.411(12)
1.434(12)
1.380(12)
1.451(9)0
1.474(12)
1.417(14)
1.372(9)0
1.366(11)
C10a– C10
C10a– C10b
C10s– C10b
C11– C16
C11– C12
C12– C13
C13– C14
C14– C15
C15– C16
1.394(11)
1.401(11)
1.397(10)
1.354(16)
1.389(13)
1.383(12)
1.384(18)
1.324(17)
1.388(14)
C8– C9
C4– C5
C9– C10
Table 2. Bond angles in the molecule of 2-phenylanthra[9,1-bc]pyrrol-6-one (VII)
Angle
ω, deg
Angle
ω, deg
Angle
ω, deg
C2N1C10b
C3C2aC10c
C3C2aC2
113.0(6)
115.7(6)
137.7(8)
106.6(8)
105.9(7)
122.7(7)
131.3(9)
120.2(9)
121.9(9)
115.4(8)
118.1(7)
126.5(7)
120.5(8)
119.0(7)
C7C6aC6
C10aC6aC6
O1C6C5a
O1C6C6a
C5aC6C6a
C6aC7C8
C9C8C7
C10C9C8
C10C10aC10b
C10C10aC6a
C10bC10aC6a
C5aC10cC10b
C5aC10cC2a
118.6(6)
122.5(8)
122.7(8)
119.6(8)
117.6(6)
121.0(7)
119.5(9)
120.5(9)
126.9(6)
117.5(8)
115.6(7)
124.3(8)
126.2(8)
C10bC10cC2a
N1C10bC10c
N1C10bC10a
C10cC10bC10a
C9C10C10a
C16C11C12
C16C11C2
109.4(6)
105.1(7)
133.0(7)
C
10cC2aC2
121.9(6)
N1C2C2a
N1C2C11
C2aC2C11
C4C3C2a
C3C4C5
122.6(7)
116.6(8)
121.8(9)
C12C11C2
121.5(9)
C13C12C11
C14C13C12
C15C14C13
C14C15C16
C11C16C15
0120.2(12)
0121.5(12)
0118.8(10)
0121.1(15)
0121.8(12)
C
10cC5aC5
10cC5aC6
C
C5C5aC6
C4C5C5a
C7C6aC10a
VII was 73% in the reduction with zinc in aqueous–
alcoholic ammonia and 70% in the reduction with
sodium tetrahydridoborate. In both cases, compound
VII was isolated as sufficiently pure substance. The
reaction mixture (in a closed vessel) turned red–brown,
and the color changed first to green and then to blue
upon exposure to atmospheric air.
protons (12H) and a singlet at δ 2.86 ppm from the NH
proton. The latter appears in a strong field as a result of
participation in hydrogen bond. Compound VII dis-
played in the 13C NMR spectrum 11 signals corre-
sponding to 21 carbon nuclei. In the high-resolution
mass spectrum of VII, the molecular ion peak [M]+ ·
had an m/z value corresponding to the calculated mo-
lecular weight; fragment ions with m/z 264, 190, 164,
and 163 were formed as a result of elimination of
PhCN, CO, and C6H5· from the molecular ion
[C21H13NO]+·.
2-Phenylanthra[9,1-bc]pyrrol-6-one (VII) crystal-
lized as blue–violet needles with cooper luster, which
decomposed at 266°C. The structure of compound VII
1
was determined on the basis of its IR, H and 13C
NMR, and mass spectra, as well as of X-ray diffraction
data. The IR spectrum of VII contained absorption
bands at 1640 (C=O), 3060 (C–Harom), and 3270 cm–1
(broad, N–H). In the H NMR spectrum of VII we
observed a multiplet at δ 7.3–8.65 ppm due to aromatic
According to the X-ray diffraction data, the mole-
cule of 2-phenylanthra[9,1-bc]pyrrol-6-one (VII) is
almost planar: the average deviation of all non-hydro-
gen atoms from the mean-square plane is 0.044 Å (see
figure). Unlike compound VII, the 2,4,6-trimethyl-
1
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 6 2010

SYNTHESIS AND STRUCTURE OF 2-PHENYLANTHRA[9,1-bc]PYRROL-6-ONE
phenyl group in structurally related 1-(2,4,6-trimethyl-
869
C14
C13
phenyl)-6H-anthra[9,1-bc]pyrrol-6-one [11] is turned
through an angle of 79.5° from the plane of the tetra-
cyclic skeleton. Molecules VII in crystal are linked in
“head-to-tail” mode through intermolecular hydrogen
bonds N1–H···O1, giving rise to chains oriented along
the a + c and a – c axes. The hydrogen bond is charac-
terized by the following parameters: N1–H 0.86,
H···O1 2.03, N1···O1 2.872 Å. The chains are packed
into stacks along the c axis as a result of π-stacking
between the six-membered rings in the neighboring
molecules; the interplanar distance is 3.42 Å, and the
intercentroid distances are 3.635(6) and 3.648(6) Å.
The bond lengths and bond angles and bond angles in
molecule VII are listed in Tables 1 and 2, respectively.
C15
C12
C16
C11
C2
C2a
N1
C10b
C10
C3
C10a
C9
C8
C4
C6a
C5a
C7
C5
C6
O1
EXPERIMENTAL
The IR spectra were recorded in the range from 400
to 4000 cm–1 on a Specord M-80 spectrometer from
samples pelleted with KBr. The mass spectra were
Structure of the molecule of 2-phenylanthra[9,1-bc]pyrrol-6-
one (VII) according to the X-ray diffraction data.
1
obtained on a Finnigan MAT-8200 instrument. The H
2-Phenylanthra[9,1-bc]pyrrol-6-one (VII).
a. 1-Benzoylanthraquinone anti-9-oxime, 0.5 g
(15 mmol), was dissolved in ethanol on heating on
a water bath, 1 g (0.015 mol) of zinc dust and 71.5 ml
of 15% aqueous ammonia were added, and the mixture
was heated for 5 min at 75°C (TLC). The mixture was
then stirred for 1 h in a closed vessel in the dark and
filtered from zinc, the filtrate was saturated with at-
mospheric air and diluted with two volumes of water,
and the precipitate was filtered off and reprecipitated
from alcohol. The product was dissolved in acetone,
the solution was filtered, the filtrate was slowly evapo-
rated almost to dryness, and the precipitate was filtered
off and dried in the dark at room temperature. Yield
0.33 g (73%), dark blue–violet needles with copper
luster, mp 266.5°C (decomp.); published data [2]:
mp 266°C. 13C NMR spectrum, δC, ppm: 120.5 (C11),
124.0 (C2a, C10a), 124.6 (C14), 124.8 (C13, C15), 126.0
(C3, C4, C8, C9), 127.0 (C12, C16), 128.2 (C5), 128.5
(C7), 129.2 (C5a, C6a, C10a, C10c), 132.6 (C2, C10b), 205.1
(C6). Mass spectrum, m/z (Irel, %): 295.09960 (100)
[M]+ ·, 264 (11.22), 190 (14.65), 164 (37.12), 163
(16.49). Calculated: M 295.09971.
and 13C NMR spectra were measured on a Bruker AC-
200 spectrometer using acetone-d6 as solvent and
hexamethyldisiloxane as internal reference. The prog-
ress of reactions and the purity of products were moni-
tored by TLC on Silufol plates. The melting points
were determined in sealed capillary on a TU-25-11-17-
44-76 apparatus. Initial 1-phenylbenzanthrone [9],
1-benzoylanthraquinone [10], and isomeric oximes [6]
were synthesized according to known procedures [6].
The X-ray diffraction data for compound VII were
acquired on a Bruker P-4 automatic four-circle dif-
fractometer [graphite monochromator, λ(MoKα) =
0.71073 Å, ω-scanning, 2θ < 50°] from a dark red
rhombic single crystal grown from acetone of ultrapure
grade at room temperature. Intensities of 1469 inde-
pendent reflections were measured at room tempera-
ture; unit cell parameters: a = 28.016(11), b =
42.40(3), c = 5.013 (3) Å; V = 5955(5) Å3; Z = 16;
dcalc = 1.318 g/cm3; μ(MoKα) = 0.081 mm–1; space
group Fdd2. The structure was solved by the direct
method using SHELXS-97 software package and was
refined with respect to all F2hkl in anisotropic approxi-
mation for non-hydrogen atoms and isotropic approxi-
mation (riding model) for hydrogen atoms using
SHELXS-97 software. The final divergence factors
were R1 = 0.0757 for 828 reflections with I > 2σ(I) and
wR2 = 0.2573 for all reflections; number of refined
parameters 208; goodness of fit 1.032.
b. 1-Benzoylanthraquinone anti-9-oxime, 0.1 g
(0.31 mmol), was dissolved in boiling alcohol, the
solution was cooled to 35–40°C, a solution of 0.07 g
(1.8 mmol) of sodium tetrahydridoborate in 0.15 ml of
water was added (TLC), the mixture was kept for
20 min in a closed vessel at room temperature, saturat-
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CHIRKOVA et al.
870
5. Diesbach, H. and Gubser, P., Helv. Chim. Acta, 1930,
vol. 13, p. 120.
6. Sholl, R. and Muller, E.J., Chem. Ber., 1935, vol. 68,
ed with atmospheric oxygen, and diluted with two
volumes of water, and the precipitate was filtered off,
washed with water, and reprecipitated from alcohol.
Yield 0.064 g (70%), mp 265–266°C (decomp.).
p. 801.
7. Gorelik, M.V. and Alimova, R.A., Zh. Obshch. Khim.,
1984, vol. 20, p. 1553.
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(Chemistry of Anthraquinones and Their Derivatives),
Moscow: Khimiya, 1983.
9. Schlichting, O. and Hrubesch, A., Deutsch Patent
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no. 859144, 1952; Chem. Zentr., 1953, p. 2522.
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