Crystal structures of 3-methyl-2(1H)-quinoxalinone and three substituted derivatives

Article abstract of DOI:10.1002/poc.1846

3-Methyl-2(1H)-quinoxalinone and three derivatives (3,7-dimethyl-2(1H)- quinoxalinone, 3-methyl-6,7-dichloro-2(1H)-quinoxalinone and 3-methyl-7-nitro-2(1H)-quinoxalinone) have been synthesised and analysed by ¹H NMR and IR spectral spectroscopies. The crystal structures have been determined at room temperature from X-ray single crystal diffraction data for three of them and from powder diffraction data for the nitro derivative. 3-Methyl-2(1H)-quinoxalinone crystallises in the P2₁/c monoclinic system, 3,7-dimethyl-2(1H)-quinoxalinone in the Pbca orthorhombic system and the two others compounds in the P1 triclinic system. For the nitro derivative, C-H..N short contacts are established between the carbon of the methyl and the double bounded nitrogen of the ring. For the three other compounds N-H..O hydrogen bonds involve the atoms of the heterocyclic ring. Copyright

Full text of DOI:10.1002/poc.1846

Research Article
Received: 28 September 2010,
Revised: 2 December 2010,
Accepted: 20 January 2011,
Published online in Wiley Online Library: 8 March 2011
(
wileyonlinelibrary.com) DOI 10.1002/poc.1846
Crystal structures of 3-methyl-2(1H)-
quinoxalinone and three substituted
derivatives
a
a
b
Denise Mondieig *, Philippe Negrier , St e´ phane Massip ,
b
c
c
Jean Michel Leger , Chakir Jarmoumi and Brahim Lakhrissi
3
2
-Methyl-2(1H)-quinoxalinone and three derivatives (3,7-dimethyl-2(1H)-quinoxalinone, 3-methyl-6,7-dichloro-
(1H)-quinoxalinone and 3-methyl-7-nitro-2(1H)-quinoxalinone) have been synthesised and analysed by H NMR
1
and IR spectral spectroscopies. The crystal structures have been determined at room temperature from X-ray single
crystal diffraction data for three of them and from powder diffraction data for the nitro derivative. 3-Methyl-2(1H)
1
-quinoxalinone crystallises in the P2 /c monoclinic system, 3,7-dimethyl-2(1H)-quinoxalinone in the Pbca orthor-
hombic system and the two others compounds in the P1 triclinic system. For the nitro derivative, C—Hꢀ ꢀ ꢀN short
contacts are established between the carbon of the methyl and the double bounded nitrogen of the ring. For the three
other compounds N—Hꢀ ꢀ ꢀO hydrogen bonds involve the atoms of the heterocyclic ring. Copyright ß 2011 John Wiley
&
Sons, Ltd.
Keywords: 3-methyl-2(1H)-quinoxalinone derivative; intermolecular interaction; powder structure; single crystal structure;
synthesis
[
17]
and ethyl pyruvate 5 in aqueous HCl
(Scheme 1). The yields
INTRODUCTION
of products 6–9 were in the range of 75–85%. Bakerman et al.
[
18]
Quinoxalin-2-ones display interesting biological properties,
including the inhibition of the aldose reductase enzyme,
partial agonists for complex receptors g-aminobutyric acid
suggested a mechanism,
in which the two amino groups
[
1]
of 1–4 stepwisely attack the two carbonyl centers of 5 (first to
the carbonyl carbon) followed by elimination of water and
ethanol.
[
2–4]
(
GABA)/benzodiazepine
and as multiple-drug-resistance
[
5]
antagonists,
amongst others properties. Additionally, the
[
6–8]
[9]
quinoxalin-2-one (Fig. 1) showed antimicrobial,
antifungic,
activities. Methylquinoxalin-2(1
H)-one had recently been identified as corrosion inhibitor for mild
[
10]
[11]
antiviral
and anticancer
General methods
[
12]
All chemicals were purchased from Aldrich or Acros (France). All
solvents were distilled before use. Thin-layer chromatography
TLC) was performed on Silica Gel 60 F254 (E. Merck) plates with
visualisation by UV light (254 nm). Melting points were evaluated
by means of a DSC7 Perkin Elmer. Because of the elevated
temperature of melting, we use a relatively high heating rate
0 K min in order to diminish the time of heating and thus to
prevent degradation of the material. H NMR spectra were
recorded on a Bruker 300 WB spectrometer at 300 MHz, in
steel in 1 M HCl solution.
accurate structural parameters of these molecules. Up today, only
few structural data on quinoxalin-2-one derivatives have been
published. Two papers
line structure and another one on a different compound as
Hence it is of interest to obtain
(
[
13,14]
reported on the 2-hydroxyquinoxa-
[
15]
3-benzoylmethylene-1-methyl-3,4-dihydroquinoxalin-2(1H)-one
ꢁ
1
1
or 2-[N-(2-hydroxyethyl) carboxamide]-3-methylquinoxaline
1
[
16]
1,4-dioxide.
In this article, we focus on the crystal structures of four
substituted 3-methyl-2(1H)-quinoxalinones which have been
synthesised and analysed by NMR and IR spectroscopies. The
structures of 3-methyl-2(1H)-quinoxalinone, 3,7-dimethyl-2(1H)-
quinoxalinone and 3-methyl-6,7-dichloro-2(1H)-quinoxalinone
were determined from single crystal data while the structure
of 3-methyl-7-nitro-2(1H)-quinoxalinone was obtained from
powder X-ray diffraction data.
*
Correspondence to: D. Mondieig, Centre de Physique Mol e´ culaire, Optique et
Hertzienne, Universit e´ Bordeaux 1, UMR 5798 au CNRS, 351 cours de la
Lib e´ ration, 33405 Talence Cedex, France.
E-mail: d.mondieig@cpmoh.u-bordeaux1.fr
a
b
c
D. Mondieig, P. Negrier
Centre de Physique Mol e´ culaire, Optique et Hertzienne, Universit e´ Bordeaux 1,
UMR 5798 au CNRS, 351 cours de la Lib e´ ration, 33405 Talence Cedex, France
S. Massip, J. M. Leger
Laboratoire de Pharmacochimie, EA 4138 Universit e´ Victor Segalen Bordeaux
EXPERIMENTAL PART
2
, 146 rue L e´ o Saignat, 33076 Bordeaux Cedex, France
Synthesis of substituted 3-methyl-2(1H)-quinoxalinones 6–9
C. Jarmoumi, B. Lakhrissi
Substituted 3-methyl-2(1H)-quinoxalinones 6–9 were prepared
by the reaction of the corresponding o-phenylenediamines 1–4
Laboratoire de Chimie des Agroressources et G e´ nie des Proc e´ d e´ s, D e´ parte-
ment de Chimie, Facult e´ des Sciences, K e´ nitra, Morocco
J. Phys. Org. Chem. 2011, 24 1193–1200
Copyright ß 2011 John Wiley & Sons, Ltd.

D. MONDIEIG ET AL.
compounds were recrystallised from a mixture of DMF-ethanol
1
(
v/v, 3:7). The H NMR and IR spectral data of 6–9 are shown in
Table 1.
X-ray diffraction measurements
For compounds 6 and 9 X-ray crystal measurements were
performed with an Enraf-Nonius CAD4 using the ‘Enraf-Nonius
SDP’ program system. The crystal of 7 has been measured with a
R-Axis Rapid diffractometer equipped with a rotating anode and
Figure 1. Substituted quinoxalin-2-ones
˚
an image plate. The X-ray wavelength was Cu-K (l ¼ 1.54180 A).
a
The structures were solved by direct methods and refined by
full-matrix least-squares using SHELXS-97 software. All of the
non-hydrogen atoms were refined anisotropically meanwhile the
H-atoms were allowed to ride on the parent atoms in the model.
Additional details of structure determination are summarised in
Table 2.
Me SO-d . Chemical shifts are given as d values with reference to
2
6
tetramethylsilane (TMS) as internal standard. Infrared (IR) spectra
were performed on Bruker tensor 27 FT/IR spectrophotometer.
For 8, we did not obtain single crystals of quality good
enough for single crystal X-ray structure determination.
Consequently we performed high-quality powder X-ray diffrac-
tion measurements by an INEL CPS-120 diffractometer operating
with Debye–Scherrer transmission geometry. Powder diffraction
patterns were collected on a 1208 curved counter by gas ionisa-
tion (Argon þ C H ). Powder sample was loaded into 0.5 mm
Synthesis of 3-methyl-2(1H)-quinoxalinone 6 and its
derivatives 7–9
A solution of 1 (5.4 g, 50 mM) in aq. HCl (20%, 50 mL) was added
to a solution of ethyl pyruvate (11.6 g, 100 mM) in aq. HCl (20%,
50 mL). The mixture was stirred at room temperature for 15 min.
The dark coloured precipitate of 6 was filtered, washed with
water (2 ꢂ 20 mL) and dried on anhydrous sodium sulphate to
give light-yellow crystals of 3-methyl-2(1H)-quinoxalinone 6
2
6
diameter Lindemann glass capillary that is rotated about its
axis during data collection in order to minimise the crystallites
preferential orientation. The powder pattern was measured in a
2u range from 38 to 1068 (step size ¼ 0.0298) although the
information used for structure determination ranges from 3.58 to
658. Pattern was recorded during six hours at room temperature.
(
6.0 g, yield 75%, mp 251 ꢃ 5 8C).
3
,7-Dimethyl-2(1H)-quinoxalinone 7 (6.61 g, yield 76%, mp
2
8
17 ꢃ 5 8C), 3-methyl-7-nitro-2(1H)-quinoxalinone 8 (10.1 g, yield
8%, mp 250 ꢃ 5 8C), and 3-methyl-6,7-dichloro- 2(1H)- quinox-
˚
alinone 9 (8.03 g, yield 85%, mp 336 ꢃ 5 8C) were prepared by
the procedure similar to that used in the preparation of 6. All
Monochromatic Cu-Ka1 radiation (l ¼ 1.5405 A) was selected
with asymmetric focusing incident-beam curved quartz
Scheme 1.
Table 1. Spectral data of 2(1H)-quinoxalinones derivatives
1
ꢁ1
Product
H NMR (DMSO-d ), ppm
IR (KBr), cm
6
—
3308 (NH), 1669 (C—O)
6
12.31 (br, 1H, NH), 7.69 (d, J ¼ 8.0 Hz, 1H, Ar—H),
7
.47 (t, J ¼ 6.8 Hz, 1H, Ar—H), 7.29 (m, 2H, Ar—H), 2.42 (s, 3H, CH )
3
—
3312 (NH), 1667 (C—O)
—
3323 (NH), 1682 (C—O),
7
8
12.23 (br, 1H, NH), 7.58–7.05 (m, 3H, Ar—H), 2.39 (s, 3H, CH
12.73 (br, 1H, NH), 8.41–7.37 (m, 3H, Ar—H), 2.44 (s, 3H, CH
3
), 2.37 (s, 3H, CH
3
)
3
)
1
539 (C—NO ), 1343 (C—NO )
2 2
—
9
12.23 (br, 1H, NH), 7.25–7.71 (m, 2H, Ar—H), 2.40 (s, 3H, CH
3
)
3152 (NH), 1670 (C—O)
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Copyright ß 2011 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2011, 24 1193–1200

STRUCTURE OF SUBSTITUTED 3-METHYL-2(1H)-QUINOXALINONE
Table 2. Crystal structures refinement information and crystallographic data for compounds 6, 7 and 9 from X-rays single crystal
analysis
Compound
6
7
9
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Z
C H N O
C H N O
10 10
174.20
293(2)
Orthorhombic
Pbca
C H Cl N O
2
9
8
2
2
9
6
2
160.17
293(2)
Monoclinic
229.06
293(2)
Triclinic
P1
1
P2 /c
4
8
2
˚
a (A)
4.050(2)
11.240(2)
16.975(5)
90
91.38(3)
90
5.0654(3)
16.0072(7)
21.9719(10)
90
90
90
1781.5(2)
1.299
5.941(4)
8.350(2)
˚
b (A)
˚
c (A)
10.160(3)
67.81(2)
75.54(3)
87.45(3)
451.2(3)
1.686
a (8)
b (8)
g (8)
Volume (A )
d (g cm
3
˚
772.5(5)
1.377
ꢁ
3
)
Crystal size mm
0.25 ꢂ 0.15 ꢂ 0.15
0.0527
0.758
0.20 ꢂ 0.10 ꢂ 0.10
0.0705
0.699
0.20 ꢂ 0.15 ꢂ 0.15
R
all
0.0635
ꢁ
1
m (Cu-K ) (mm
)
6.181
a
2
umax (8)
129.8
140.1
129.8
No. reflections used
No. of parameters
Goodness of fit on F
Final R
indices [I > 2s(I)]
Max. and min.
transmission
1285
111
1.008
1645
121
1.008
1502
129
1.035
2
R
1
¼ 0.0500,
R
1
¼ 0.0684,
R
1
¼ 0.0530,
wR ¼ 0.1316
wR ¼ 0.1831
wR ¼ 0.1566
2
2
2
0.8948
and 0.8331
336
0.9334
and 0.8729
736
0.4575
and 0.3712
232
F(000)
ꢁ
3
˚
˚
(D/r) max (A
)
0.195
0.301
0.313
ꢁ
3
(D/r) min (A
)
ꢁ0.223
ꢁ0.175
ꢁ0.243
CCDC deposition number
785053
785054
785055
monochromator. The generator power was set to 40 kV and
5 mA. External calibration to convert the measured 4096
channels into 2u degrees was carried out with the Na Ca Al
Structure solution was attempted afterwards. First, the mole-
cule was drawn in a 3D worksheet and it was minimised in energy
2
[
22]
2
3
2
F
14
by geometry optimisation using the COMPASS force field
to
cubic phase mixed with silver behenate as external standard. The
peak positions were determined after pseudo-Voigt fitting by
using DIFFRACTINEL software.
obtain relevant distances, angles and torsions for its various
bonds. Structure solution was attempted by direct-space
methods following a Monte-Carlo simulated annealing approach
[
23]
and full profile comparison as implemented in Powder Solve.
For 8, the minimised molecule shape was not correct, the
heterocyclic ring was flattened with the two nitrogen atoms
closer than those of the three other compounds. Therefore, the
molecule was drawn by adding the nitro group at the molecule of
Crystal structure determination from powder data
methodology
Peak positions were determined manually using the Peak picking
compound 6. Considering the Cambridge Structural Database
[
19]
[24–26]
option of the PC modelling platform Materials Studio. Potential
solutions of cell parameters and space groups were obtained
CSD of the CCDC and literature data,
bond lengths and
˚
˚
torsion angles of the nitro group were set at 1.466 A, 1.220 A,
123.48 and 118.38, respectively, for C—N, N—O, O—N—O and
C—N—O (so, the four atoms are coplanar). The drawn molecule
was then set as a rigid body, but with the C2—C1—N13—O14
torsion angle involving the nitro group allowed to adjust freely
and it is placed inside the unit cell previously determined,
together with its homologues related by the space group
symmetry. The total number of degrees of freedom is seven:
three translations, three rotations and the dihedral angle of the
[
20]
using the X-Cell
algorithm available in the Powder Indexing
module of Materials Studio. The cell parameters and space group
that best reproduced the experimental diffraction patterns were
[
21]
chosen and refined using a Pawley profile-fitting procedure
over a 2u range from 3.58 to 608. Pawley refinement was used to
provide refined cell parameters, the peak profile parameters
(
profile function, FWHM and asymmetry), the background and
the zero shift. All the parameters used are consigned in Table 3.
J. Phys. Org. Chem. 2011, 24 1193–1200
Copyright ß 2011 John Wiley & Sons, Ltd.
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D. MONDIEIG ET AL.
Table 3. Results from the Rietveld refinement for compound
8
Parameter
Value
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Z
C H N O
7 3 3
205.18
293
Triclinic
P1
9
2
Lattice parameters
˚
a (A)
˚
11.226 (2)
11.168 (1)
3.931(1)
b (A)
˚
c (A)
a (8)
b (8)
g (8)
Volume (A )
d (g cm
97.64 (1)
95.38 (1)
101.56 (1)
474.9(6)
Figure 2. Experimental (red circles) and calculated (blue line) diffraction
patterns along with the difference profile (black line) of 3-methyl-7-
nitro-2(1H)-quinoxalinone (compound 8) at 295K. Inset corresponds to
the scale for the data with 2u > 358
3
˚
ꢁ
3
)
1.435
2
2
u-angular range
u-shift (zero correction)
5.0–65.0
0.01797 ꢃ 0.00098
initially searched within the Powder Solve module by the
March–Dollase function and the Rietveld–Toraya function
for the final Rietveld refinement.
[
27]
[28,29]
Asymmetry parameters (Finger–Cox–Jephcoat function)
2
u limit
17.000
H/L
S/L
0.02015 ꢃ 0.00015
The experimental collected and the final calculated profiles for
are shown in Fig. 2 together with the difference plot between
them. Calculated and experimental profiles are in a good
agreement as shown by the difference plot (black curve) and the
reliability parameters (Table 3).
0.02032 ꢃ 0.00015
8
Reliability parameters
Rwp
6.44%
4.46%
Rp
Peak shape parameters
u
v
w
0.03012 ꢃ 0.02508
0.04822 ꢃ 0.00882
0.00314 ꢃ 0.00068
0.05932 ꢃ 0.00227
RESULTS AND DISCUSSION
Overall isotropic temperature
factor, U/A
2
˚
The crystallographic data and structural parameters of refine-
ment at room temperature for 6, 7 and 9 are given in Table 2 and
in Table 3 for 8. They crystallise in three different systems.
Compound 6 is monoclinic, 7 orthorhombic as compound 1
but with different space group. Compounds 8 and 9 are triclinic.
The ORTEP representations (with the ellipsoids drawn at the
Preferred orientation (Rietveld–Toraya function)
a*
0.05932 ꢃ 0.00227
b
*
0.20997 ꢃ 0.04292
0.46389 ꢃ 0.02376
0.15864 ꢃ 0.05758
0.00000
[13,14]
c*
G1
G2
5
0% probability level and including the atomic numbering) of
CCDC deposition number
785056
theses structures are shown in Fig. 3a, b, c, d for 6, 7, 9 and 8,
ꢁ
ꢁ
ꢂ
respectively. The molecules of these compounds are very similar
and intra-molecular bonds are comparable to those of.
Relevant bond distances are summarised in Table 4. The carbon
P
ꢀ
ꢀ
ꢀ2
sim
exp
back
ꢀ
[13]
Rwp ¼
wi cY ð2uiÞꢁI ð2uiÞ þ Y
ð2uiÞ
i
ꢂ
1=2
P
exp
2
ring is aromatic (mean C—C bond distance is 1.39 A). The
˚
=
wijI ð2uiÞj
.
i
heterocyclic and benzene rings are planar, the dihedral angle
ꢁ
ꢂ
P
ꢀ
ꢀ
ꢀ
P
[13]
between the planes are small, 1.48, 0.58, 2.08 and 1.68 for 6, 7, 9
ꢀ
exp
cYsimð2uiÞꢁI ð2uiÞ þ Y
back
exp
Rp ¼
ð2uiÞ
=
jI ð2uiÞj.
—
and 1, respectively. The C8—O11 double bonds vary between
i
i
˚
1
.228 and 1.239 A. For 8, the refined values of torsion angles
involving the nitro group are given in Table 5, they indicate that
the nitro group is slightly out of the heterocyclic ring plane.
Projections of the structures are shown in Figs. 4, 5, 6 and 7 for
6, 7, 8 and 9, respectively. The shortest donor –Hꢀ ꢀ ꢀ acceptor
distances are represented with blue dashed lines. Despite the
similarities of the molecule shapes, their packing in the crystal is
diverse as they crystallise in three distinct space groups. In the
orthorhombic structure of 7 (Fig. 5), molecules form a zigzag
along b direction with an angle of 838 between the molecules.
Though in the monoclinic structure of 6 (Fig. 4), the angles
between molecules are smaller, 178 and 258, respectively, for the
nitro group. Following the global optimisation algorithm, trial
structures are continuously generated by modifying the seven
degrees of freedom to find the trial structure that yields the
best agreement between calculated and experimental powder
patterns.
The following Rietveld procedure included refinement of the
translation, rotation and dihedral angle of the molecule, the
isotropic temperature factors, and the preferred orientations, also
with the parameters previously refined in the Pawley procedure.
Preferred-orientation corrections of the powder sample were
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Copyright ß 2011 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2011, 24 1193–1200

STRUCTURE OF SUBSTITUTED 3-METHYL-2(1H)-QUINOXALINONE
Figure 3. ORTEP plots (with the ellipsoids drawn at the 50% probability level): (a) 3-methyl-2(1H)-quinoxalinone (compound 6), (b)
3,7-dimethyl-2(1H)-quinoxalinone (compound 7), (c) 3-methyl-6,7-dichloro-2(1H)-quinoxalinone (compound 9) and (d) 3-methyl-7-nitro-2(1H)- quinox-
alinone (compound 8)
˚
Table 4. Intramolecular bond distances in A: (a) Common
bonds (common distances in compound 8 have been con-
sidered as identical to those of compound 6), (b) Other bonds
Table 5. Torsion angles involving the nitro group in com-
pound 8
Compounds
Torsion
Angle (8)
Bonds
a)
6
7
9
C6—C1—N13—O14
C6—C1—N13—O15
C2—C1—N13—O14
C2—C1—N13—O15
174.51
ꢁ5.30
ꢁ4.23
175.96
(
N7—C4
N7—C8
N10—C3
N10—C9
C1—C2
C1—C6
C2—C3
C3—C4
C4—C5
C5—C6
C8—C9
C9—C12
O11—C8
1.380
1.345
1.387
1.291
1.365
1.401
1.398
1.400
1.393
1.368
1.482
1.485
1.239
1.377
1.354
1.384
1.288
1.375
1.402
1.396
1.401
1.395
1.373
1.490
1.453
1.232
1.362
1.346
1.391
1.286
1.378
1.402
1.398
1.424
1.379
1.369
1.497
1.486
1.228
2
-fold screw axis and by the glide plane symmetry related
molecules. Compounds 8 and 9 have the same triclinic space
group but molecules are stacked differently. For 8 (Fig. 6), short
contact bonds involve the C12ꢀ ꢀ ꢀH12A atoms of the methyl
substituent and the double bonded nitrogen N10 of the ring.
There are edge-to-edge overlaps of the benzene rings
between adjacent neighbouring molecules related by x, y,
z ꢁ 1 and x, y, z þ 1 symmetry transformations. The C3ꢀꢀꢀC5
˚
and C2ꢀꢀꢀC6 inter-molecular distance is 3.37 A. For 9 (Fig. 7), the
molecules are stacked by two hydrogen bonds involving N7—H7
and O11. Compounds 7 and 8 exhibit the same type of
hydrogen bonds as 9. The characteristic distances and angles
relative to the hydrogen bonds and short contacts are
summarised in Table 6. Compound 6 exihibits long hydrogen
bonds which can be related to the smallest size of R1 and R2
substituents.
Compounds
Bond
Distance
(
b)
7
9
C6—C16
Cl13—C1
Cl16—C6
1.492
1.736
1.728
J. Phys. Org. Chem. 2011, 24 1193–1200
Copyright ß 2011 John Wiley & Sons, Ltd.
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D. MONDIEIG ET AL.
Figure 4. Monoclinic structure of 3-methyl-2(1H)-quinoxalinone (compound 6). Blue dotted lines indicate the hydrogen bonds. (a) (b, c) plane and (b) (a,
c) plane
Figure 5. Orthorhombic crystal structure of 3,7-dimethyl-2(1H)-quinoxalinone (compound 7). (a) (b, c) plane and (b) (a, b) plane
Figure 6. Triclinic structure of 3-methyl-6,7-dichloro-2(1H)-quinoxalinone (compound 9). (a) (b, c) plane and (b) (a, c) plane
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Copyright ß 2011 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2011, 24 1193–1200

STRUCTURE OF SUBSTITUTED 3-METHYL-2(1H)-QUINOXALINONE
Figure 7. Triclinic structure of 3-methyl-7-nitro-2(1H)-quinoxalinone (compound 8). (a) (a, b) plane and (b) (a, c) plane
Table 6. Shortest donor –Hꢀ ꢀ ꢀ acceptor distances
˚
Hꢀ ꢀ ꢀA ( A˚ )
Dꢀ ꢀ ꢀA ( A˚ )
Compound
D—Hꢀ ꢀ ꢀA
D—H (A)
D—Hꢀ ꢀ ꢀA (8)
(A) Symmetry code
6
7
8
9
N7 H7 O11
N7 H7 O11
0.860
0.859
0.960
0.860
1.949
1.992
1.680
1.987
2.801
2.836
2.622
2.839
170.8
166.9
166.0
170.4
ꢁx þ 1, 1 ꢁ y, ꢁz
ꢁx þ 1, ꢁy, ꢁz þ 1
ꢁx þ 1, ꢁy þ 2, ꢁz þ 3
ꢁx þ 1, ꢁy þ 2, ꢁz ꢁ 1
C12 H12 N10
A
N7 H7 O11
CONCLUSION
[2] R. E. TenBrink, W. B. Im, V. H. Sethy, A. H. Tang, D. B. Carter, J. Med.
Chem. 1994, 37, 758.
[
3] E. J. Jacobsen, R. E. TenBrink, L. S. Stelzer, K. L. Belonga, D. B. Carter, H.
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3
-Methyl-2 (1H)-quinoxalinone and three derivatives (3,7-
dimethyl-2 (1H)-quinoxalinone, 3- methyl-6,7- dichloro- 2( 1H)-
quinoxalinone and 3- methyl-7-nitro-2(1H)-quinoxalinone) have
been synthesised and analysed by H NMR and IR spectral
[
1
spectroscopies.
1
123–1144.
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94–601.
The crystal structures have been determined at room
temperature from X-ray single crystal diffraction for three of
them and from powder diffraction for the nitro derivative. This
last structure was determined by the combination of direct space
Monte-Carlo simulated annealing methods and Rietveld refine-
ment combined with force-field-energy minimisation.
The shape of the molecules only differ by the presence
of different R1 and R2 substituents, the common intermolecular
distances are very similar. The benzene and the heterocyclic
rings are planar and the inter-ring dihedral angles are small
[
5
[6] P. Sanna, A. Carta, M. Loriga, S. Zanetti, L. Sechi, IL Farmaco 1999, 54,
161–168.
[
7] P. Sanna, A. Carta, M. Loriga, S. Zanetti, L. Sechi, IL Farmaco 1999, 54,
69–177.
1
[
8] M. M. Ali, M. M. F. Ismail, M. S. A. El-Gaby, M. A. Zahran, Y. A. Ammar,
Molecules 2000, 5, 864–873.
[9] A. Carta, P. Sanna, L. Gherardini, D. Usai, S. Zanetti, IL Farmaco 2001,
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5
[
Viitanen, G. L. Trainor, J. D. Rodgers, Bioorg. Med. Chem. Lett. 2000, 10,
(
ꢄ28).
Crystal structures in terms of crystal packing are very different.
-Methyl-2(1H)-quinoxalinone crystallises in the monoclinic
1729–1731.
[11] A. Carta, P. Sanna, M. Loriga, M. G. Setzu, P. L. Colla, R. Loddo, IL
Farmaco 2002, 57, 19–25.
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Addou, Spectrosc. Lett. 2010, 43(2), 136–143.
3
[
system, 3,7-dimethyl-2(1H)-quinoxalinone in the orthorhombic
system and the two others compounds in the triclinic system. For
compounds 6, 7 and 9, the molecules are united into
centro-symmetric dimers via N—Hꢀ ꢀ ꢀO hydrogen bonds invol-
ving the atoms of the heterocyclic ring. For the nitro derivative
C—Hꢀ ꢀ ꢀN short contact bonds are established between the
double bonded nitrogen of the ring and the carbons of the
methyl.
[
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