Five-membered 2,3-dioxo heterocycles: LVII. Recyclization of 3-pivaloylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones by the action of o-phenylenediamine. Crystalline and molecular structure of 3-[3,3-dimethyl-2- oxo-1-(3-oxo-3,4-dihydroquinoxalin-2-yl)butyl]-1-phenylquinoxalin-2(1H)-one

Article abstract of DOI:10.1134/S1070428008040234

3-[(Z)-3,3-Dimethyl-2-oxobutylidene]-3,4-dihydroquinoxalin-2(1H)-one and its 1-phenyl-substituted analog reacted with oxalyl chloride to give the corresponding 3-pivaloylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones. Reactions of the latter with o-phenylenediamine led to the formation of 3,3′-(3,3-dimethyl-2-oxobutane-1,1-diyl)di[quinoxalin-2(1H)-ones].

Full text of DOI:10.1134/S1070428008040234

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 4, pp. 607–611. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © K.S. Bozdyreva, Z.G. Aliev, A.N. Maslivets, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 4, pp. 612–616.
Five-Membered 2,3-Dioxo Heterocycles: LVII.*
Recyclization of 3-Pivaloylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-
triones by the Action of o-Phenylenediamine. Crystalline
and Molecular Structure of 3-[3,3-Dimethyl-2-oxo-1-(3-oxo-
3,4-dihydroquinoxalin-2-yl)butyl]-1-phenylquinoxalin-2(1H)-one
K. S. Bozdyrevaa, Z. G. Alievb, and A. N. Maslivetsa
a Perm State University, ul. Bukireva 15, Perm, 614990 Russia
e-mail: koh2@psu.ru
b Institute of Chemical Physics Problems, Russian Academy of Sciences, Chernogolovka, Moscow oblast, Russia
Received May 16, 2006
Abstract—3-[(Z)-3,3-Dimethyl-2-oxobutylidene]-3,4-dihydroquinoxalin-2(1H)-one and its 1-phenyl-substi-
tuted analog reacted with oxalyl chloride to give the corresponding 3-pivaloylpyrrolo[1,2-a]quinoxaline-
1,2,4(5H)-triones. Reactions of the latter with o-phenylenediamine led to the formation of 3,3′-(3,3-dimethyl-2-
oxobutane-1,1-diyl)di[quinoxalin-2(1H)-ones].
DOI: 10.1134/S1070428008040234
3-Aroyl- and 3-hetaroyl-substituted pyrrolo[1,2-a]-
quinoxaline-1,2,4(5H)-triones were found to be con-
venient reagents for the synthesis of difficultly acces-
sible polycarbonyl derivatives of nitrogen-containing
heterocycles and fused heterocyclic systems. Hetero-
cyclizations of these compounds in reactions with
difunctional nucleophiles involve appending of a new
heteroring, the original heterocyclic system being re-
tained [2–6]. The present study continues our works on
the properties of pyrrolo[1,2-a]quinoxaline-1,2,4(5H)-
triones; it was aimed at synthesizing new represent-
atives of this class of compounds, namely 3-pivaloyl-
pyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones and study-
ing their reactions with o-phenylenediamine. We be-
lieved that introduction of a bulky tert-butyl group into
the acyl moiety in the 3-position of the pyrroloquin-
oxaline system could radically affect the direction of
their reactions with binucleophiles.
shown in Scheme 1. Compounds Ia and Ib are yellow
high-melting crystalline substances which are readily
soluble in DMF and DMSO, poorly soluble in other
common organic solvents, and insoluble in saturated
hydrocarbons and water. The IR spectra of Ia and Ib
contain absorption bands due to stretching vibrations
of the N1H group (a sharp peak at 3340 cm–1 in the
spectrum of Ia), N4H group involved in intramolecular
hydrogen bond (a broad band in the region 3130–
3150 cm–1), C2=O amide carbonyl group (1678–
1682 cm–1), and pivaloyl carbonyl group involved in
intramolecular hydrogen bond (a broad band centered
at 1619–1622 cm–1). In the 1H NMR spectra of quinox-
alines Ia and Ib, recorded from solutions in DMSO-d6,
we observed signals from aromatic protons, a nine-
proton singlet from the tert-butyl group at δ 1.17–
1.18 ppm, a singlet from the exocyclic vinylic proton
at δ 6.28–6.33 ppm, a singlet from the N1H proton at
δ 11.91 ppm (Ia), and a singlet from the N4H proton at
δ 13.30 ppm; the latter is displaced downfield due to
formation of intramolecular hydrogen bond. The dou-
blet signal from the 8-H proton in the quinoxaline ring
of compound Ib appeared separately from the other
aromatic proton signals (δ 6.30 ppm) due to shielding
effect produced by π-electron system of the benzene
ring on N1. The spectral parameters of compounds Ia
Initial 3-[(Z)-3,3-dimethyl-2-oxobutylidene]-3,4-di-
hydroquinoxalin-2(1H)-one (Ia) and its 1-phenyl-sub-
stituted analog Ib were synthesized according to the
procedure reported in [7], by reaction of 5,5-dimethyl-
2,4-dioxohexanoic acid [8] with o-phenylenediamine
and N-phenyl-o-phenylenediamine, respectively, as
* For communication LVI, see [1].
607

BOZDYREVA et al.
608
Scheme 1.
R
R
N
Me
O
NHR
NH2
N
O
O
O
ClCOCOCl
+
O
Me
Me
OH
N
H
N
O
O
Bu-t
O
Bu-t
O
Ia, Ib
IIa, IIb
R
N
Me
NH2
O
O
O
Me
Me
O
R
N
NH2
N
H
Bu-t
H
N
N
N
O
O
N
H
O
H2N
IIIa, IIIb
R = H (a), Ph (b).
1
and Ib indicate that they exist in solution and in the
crystalline state as Z isomers stabilized by strong intra-
molecular hydrogen bond between the N4H proton and
side-chain carbonyl oxygen atom, which is typical of
structurally related compounds [7].
The H NMR spectra of solutions of IIa and IIb in
DMSO-d6 contained signals from aromatic protons,
a nine-proton singlet from the tert-butyl group at
δ 1.13 ppm, and a singlet from the N5H proton at
δ 11.77 ppm (IIa). The doublet signal from the 9-H
proton is displaced downfield (δ 8.30–8.46 ppm) rela-
tive to the other aromatic proton signals as a result of
deshielding effect produced by the C1=O carbonyl
group. By contrast, the 6-H signal in the spectrum of
compound IIb appears in a stronger field (δ 6.36 ppm,
d) due to shielding by π-electron system of the benzene
ring on N5.
By reaction of quinoxalines Ia and Ib with oxalyl
chloride in anhydrous benzene (reaction time 1 h) we
obtained the corresponding 3-pivaloyl-5-phenylpyr-
rolo[1,2-a]quinoxaline-1,2,4(5H)-triones IIa and IIb
in almost quantitative yield (Scheme 1). Compounds
IIa and IIb are dark violet (almost black) crystalline
substances melting with decomposition at high tem-
perature. They are readily soluble in DMF and DMSO,
poorly soluble in other common aprotic organic sol-
vents, and insoluble in saturated hydrocarbons. Pyr-
roloquinoxalines IIa and IIb react with alcohols and
water; they turn colorless on storage due to hydrolysis
by the action of atmospheric moisture. Compounds IIa
and IIb displayed in the IR spectra absorption bands
belonging to stretching vibrations of the N5H group
(a narrow peak at 3340 cm–1 in the spectrum of IIa),
lactam carbonyl group (C1=O, 1760–1763 cm–1),
ketone carbonyl group (C2=O, 1733–1735 cm–1),
amide carbonyl group (C4=O, 1674–1686 cm–1), and
pivaloyl carbonyl group (1624–1626 cm–1). The range
of carbonyl stretching vibration frequencies, as well as
the higher stretching vibration frequency of the lactam
carbonyl group compared to the endocyclic ketone car-
bonyl group, corresponds to published data for mono-
cyclic 1H-pyrrole-2,3-diones [9] and isatins [10].
It is known that 4-alkoxalyl- and 4-aroyl-substi-
tuted monocyclic 1H-pyrrole-2,3-diones react with
o-phenylenediamine according to a scheme involving
successive nucleophilic attacks on the C5 carbon atom
and carbonyl carbon atom in the acyl group on C4; as
a result, substituted pyrrolo[2,3-b][1,4]benzodiazepine-
2,3-diones are formed [11, 12]. 4-Aroyl- and 4-het-
aroyl-substituted 1H-pyrrole-2,3-diones fused to a quin-
oxaline system, namely 3-aroyl- and 3-hetaroylpyr-
rolo[1,2-a]quinoxaline-1,2,4-(5H)-triones react with
o-phenylenediamine in a similar way to produce 8-aryl-
(hetaryl)-9,14-dihydroquinoxalino[1′,2′:1,2]pyrrolo-
[2,3-b][1,5]benzodiazepine-6,7,15(16H)-triones [2, 3].
In continuation of our studies on the transformations of
4-acyl-substituted 1H-pyrrole-2,3-diones in reactions
with nucleophiles, we examined reactions of 3-piva-
loylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones IIa
and IIb with o-phenylenediamine. The reactions were
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008

FIVE-MEMBERED 2,3-DIOXO HETEROCYCLES: LVII.
carried out in boiling anhydrous benzene using equi-
609
C16
C17
C15
molar amounts of the reactants. After 15–25 min,
colorless crystalline products IIIa and IIIb separated
from the reaction mixtures on cooling. However, we
failed to unambiguously determine their structure on
the basis of the IR and NMR data. X-Ray diffraction
study of a single crystal of compound IIIb showed that
it has the structure of 3-[3,3-dimethyl-2-oxo-1-(3-oxo-
3,4-dihydroquinoxalin-2-yl)butyl]-1-phenylquinoxalin-
2(1H)-one.
C21
C14
C11
C22
C23
C20
C19
C12
N1
C13
C6
C10
O1
C2
C18
N3
C1
C9
N4
C4
H3
O3
C8
C7
C5
O2
N2
H4
C3
C24
C25
Compounds IIIa and IIIb are colorless crystalline
substances with high melting points. They are poorly
soluble in common organic solvents, except for DMF
and DMSO, and insoluble in water and saturated hy-
drocarbons. The IR spectra of IIIa and IIIb contained
absorption bands assignable to stretching vibrations of
NH (3150–3160 cm–1) and carbonyl groups (1664–
C27
C28
C26
1
1665 cm–1). In the H NMR spectra of these com-
Fig. 1. Structure of the molecule of 3-[3,3-dimethyl-2-oxo-1-
(3-oxo-3,4-dihydroquinoxalin-2-yl)butyl]-1-phenylquinox-
alin-2(1H)-one (IIIb) according to the X-ray diffraction data.
pounds in DMSO-d6, apart from signals in the aromat-
ic region, we observed a nine-proton singlet from the
tert-butyl group at δ 1.20–1.22 ppm, a singlet from CH
proton at δ 6.42–6.44 ppm, and signals from one (IIIb)
or two (IIIa) NH protons in the region δ 12.52–
12.57 ppm. In the spectrum of IIIb, the 8-H signal
(δ 6.64 ppm, d) was displaced upfield due to shielding
by π-electron system of the benzene ring on N1.
Compounds IIIa and IIIb are likely to be formed
via successive attacks by the amino groups of o-phen-
ylenediamine on the carbon atoms in positions 1 and 2
of pyrroloquinoxalinetriones Ia and Ib with interme-
diate cleavage of the C1–N10 bond. The reaction of
3-pivaloylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones
IIa and IIb with o-phenylenediamine follows a differ-
ent path than that reported for 3-aroyl(hetaroyl)pyr-
rolo[1,2-a]quinoxaline-1,2,4(5H)-triones [2, 3].
Probable reasons are steric hindrances to nucleophilic
attack on the pivaloyl carbonyl group, created by the
bulky tert-butyl group and different electron density
distribution in molecules Ia and Ib due to strong elec-
tron-donating effect of the tert-butyl group.
All bond lengths and bond angles in the molecule
of compound IIIb (Fig. 1) range within the corre-
sponding standard intervals. Interatomic distances in
the two quinoxaline fragments are similar; the double
C2=N2 (1.295 Å) and C4=N3 bonds (1.303 Å) therein
are localized. The quinoxaline ring planes are arranged
in a crossed conformation with respect to the C2–C3
and C4–C3 bonds, and the dihedral angle between them
is equal to 75.5°. Molecules IIIb in crystal give rise to
centrosymmetric dimers formed by strong intermolec-
ular hydrogen bonds N4–H4 ···O2′ with the following
parameters: N4···O2′ 2.79, H4···O2′ 1.86 Å, ∠N4H4O2′
174° (Fig. 2). Presumably, the formation of intermolec-
ular hydrogen bond is responsible for extension of the
C5=O2 bond to 1.233 Å. The C1=O1 bond is also
extended to 1.239 Å, whereas the C24=O3 bond has
a standard length (1.199 Å). Probably, the O1 atom is
also involved in hydrogen bonding with crystallization
water molecule. The O1···O29 distance equal to 3.17 Å
is too large for a strong hydrogen bond; however, the
accuracy in the localization of the oxygen atom in
the crystallization water molecule is not high due to
large thermal vibration amplitude and small number of
experimental reflections.
It should be noted that the described reaction
provides a new example of formation of difficultly
accessible bis-quinoxaline heterocyclic systems with
functional substituents in both quinoxaline fragments.
EXPERIMENTAL
The IR spectra were recorded in mineral oil on
a UR-20 spectrophotometer. The H and 13C NMR
1
spectra were obtained on a Bruker AM-400 spectrom-
1
eter (400 MHz for H) from solutions in DMSO-d6
containing tetramethylsilane as internal reference. The
purity of the products was checked by thin-layer
chromatography on Silufol plates (eluent benzene–
ethyl acetate, 5:1; spots were visualized by treatment
with iodine vapor or under UV light).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008

BOZDYREVA et al.
610
H4a
O2
O2a
H4
Fig. 2. Fragment of the crystalline structure of 3-[3,3-dimethyl-2-oxo-1-(3-oxo-3,4-dihydroquinoxalin-2-yl)butyl]-1-phenylquinox-
alin-2(1H)-one (IIIb) according to the X-ray diffraction data.
1626 (t-BuC=O), 1686 (C4=O), 1733 (C2=O), 1760
3-[(Z)-3,3-Dimethyl-2-oxobutylidene]-3,4-dihy-
1
(C1=O), 3340 (N–H). H NMR spectrum, δ, ppm:
droquinoxalin-2(1H)-one (Ia). A suspension of 1.60 g
(9.3 mmol) of 5,5-dimethyl-2,4-dioxohexanoic acid
and 1.01 g (9.3 mmol) of o-phenylenediamine in 40 ml
of ethanol was heated for 60 min under reflux. The
mixture was cooled, and the precipitate was filtered off
and recrystallized from ethanol. Yield 1.63 g (72%),
mp 242–243°C. IR spectrum, ν, cm–1: 1622 br
(t-BuCO), 1682 (C2=O), 3130 br (N4–H), 3340
1.13 s (9H, CMe3), 7.07–7.19 m (3H, Harom), 8.30 d
(1H, 9-H, J = 6.9 Hz), 11.77 s (1H, NH). Found, %:
C 64.45; H 4.74; N 9.35. C16H14N2O2. Calculated, %:
C 64.42; H 4.73; N 9.39.
5-Phenyl-3-pivaloylpyrrolo[1,2-a]quinoxaline-
1,2,4(5H)-trione (IIb) was synthesized in a similar
way. Yield 2.29 g (98%), mp 233–235°C (decomp.,
from benzene). IR spectrum, ν, cm–1: 1624 (t-BuC=O),
1
(N1–H). H NMR spectrum, δ, ppm: 1.17 s (9H,
CMe3), 6.28 s (1H, C3=CH), 7.09–7.43 m (4H, 5-H–
8-H), 11.91 s (1-H), 13.30 s (4-H). 13C NMR spectrum,
δC, ppm: 27.09 (Me), 41.84 (CMe3), 88.23 (C3=CH),
115.12–144.39 (Carom), 155.12 (C2=O), 205.16
(t-BuCO). Found, %: C 68.88; H 6.61; N 11.47.
C14H16N2O2. Calculated, %: C 68.83; H 6.60; N 11.47.
1
1674 (C4=O), 1735 (C2=O), 1763 (C1=O). H NMR
spectrum, δ, ppm: 1.13 s (9H, CMe3), 6.36 d (1H, 6-H,
J = 8.2 Hz), 7.07–7.84 m (7H, Harom), 8.46 d (1H, 9-H,
J = 8.2 Hz). Found, %: C 70.53; H 4.86; N 7.42.
C22H18N2O4. Calculated, %: C 70.58; H 4.85; N 7.48.
3,3′-(3,3-Dimethyl-2-oxobutane-1,1-diyl)di[quin-
oxalin-2(1H)-one] (IIIa). A solution of 0.36 g
(3.4 mmol) of o-phenylenediamine in 30 ml of anhy-
drous benzene was added to 1.00 g (3.4 mmol) of com-
pound IIa in 40 ml of anhydrous benzene, and the
mixture was heated for 15 min under reflux until the
original dark violet color disappeared. The mixture
was cooled, and the precipitate was filtered off. Yield
1.08 g (83%), mp 279–280°C (from propan-2-ol). IR
spectrum, ν, cm–1: 1664 (C=O, t-BuC=O), 3160
(N–H). 1H NMR spectrum, δ, ppm: 1.20 s (9H, CMe3),
6.42 s (1H,), 7.26–7.63 m (8H, Harom), 12.52 br.s
(2H, NH). Found, %: C 68.03; H 5.17; N 14.42.
C22H20N4O3. Calculated, %: C 68.03; H 5.19; N 14.42.
3-[(Z)-3,3-Dimethyl-2-oxobutylidene]-1-phenyl-
3,4-dihydroquinoxalin-2(1H)-one (Ib) was synthe-
sized in a similar way. Yield 2.75 g (86%), mp 158–
160°C (from ethanol). IR spectrum, ν, cm–1: 1619 br
1
(t-BuC=O), 1678 (C2=O), 3150 br (N4–H). H NMR
spectrum, δ, ppm: 1.18 s (9H, CMe3), 6.30 d (1H, 8-H,
J = 7.6 Hz), 6.33 s (1H, C3=CH), 6.96–7.65 m
(8H, C6H5, 5-H, 6-H, 7-H), 13.30 s (4-H). Found, %:
C 74.92; H 6.26; N 8.73. C20H20N2O2. Calculated, %:
C 74.98; H 6.29; N 8.74.
3-Pivaloylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-
trione (IIa). A solution of 1.00 g (4 mmol) of com-
pound Ia and 0.37 ml (4.3 mmol) of oxalyl chloride in
20 ml of anhydrous benzene was heated for 60 min
under reflux (until the originally yellow mixture turned
dark violet). The mixture was cooled, and the precip-
itate was filtered off. Yield 1.12 g (92%), mp 242–
243°C (decomp., from benzene). IR spectrum, ν, cm–1:
3-[3,3-Dimethyl-2-oxo-1-(3-oxo-3,4-dihydroquin-
oxalin-2-yl)butyl]-1-phenylquinoxalin-2(1H)-one
(IIIb) was synthesized in a similar way. Yield 0.59 g
(92%), mp 198–200°C (from acetonitrile). IR spec-
trum, ν, cm–1: 1665 (C=O, t-BuC=O), 3150 (N–H).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008

FIVE-MEMBERED 2,3-DIOXO HETEROCYCLES: LVII.
1H NMR spectrum, δ, ppm: 1.22 s (9H, CMe3), 6.44 s
611
REFERENCES
(1H), 6.64 d (1H, 8-H, J = 7.4 Hz), 7.29–7.73 m (12H,
Harom), 12.57 s (1H, NH). 13C NMR spectrum, δC, ppm:
26.88 (Me), 44.44 (CMe3), 54.00 (CH), 115.25–135.37
(Carom), 153.00 (C3′=O), 153.69 (C2=O), 157.61 (C3),
157.87 (C2′), 209.52 (t-BuCO). Found, %: C 72.41;
H 5.28; N 12.00. C28H24N4O3. Calculated, %: C 72.40;
H 5.21; N 12.06.
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rameters: a = 13.640(3), b = 11.573(2), c = 8.540(2) Å;
α = 73.94(3), β = 88.96(3), γ = 83.97(3)°; V =
1288.1(5) Å3; M 482.53; dcalc = 1.244 g/cm3; Z = 2;
space group P-1. The unit cell parameters and the set
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positions of non-hydrogen atoms was performed in
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[14] and was complete at R1 = 0.0840, wR2 = 0.2026
[for reflections with I ≥ 2σ(I)]; goodness of fit 0.800.
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008