10-Ethyl-4-oxo-2,3,4,10-tetrahydropyrimido[4,5-b]quinolin-2-iminium 4-toluenesulfonate: A polarized electronic structure in the cation and a hydrogen-bonded sheet structure

Article abstract of DOI:10.1107/S0108270108016995

In the title compound, C13H13N4O⁺·C7H7O3S^-, the bond distances within the cation provide evidence for the delocalization of the positive charge in a manner reminiscent of guanidinium cations. Three independent N - H...O hydrogen bonds link the ions into centrosymmetric four-ion aggregates, and these are further linked into sheets by a single C - H...O hydrogen bond. This study shows how a single hydrogen bond can link centrosymmetric entities into a continuous sheet structure.

Full text of DOI:10.1107/S0108270108016995

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
the non-H atoms of the ring systems within the asymmetric
unit are almost coplanar. The main deviations from the near
planarity are found for the O atoms of the sulfonate group and
the ethyl group pendent from the cation, the plane of which is
almost orthogonal to that of the adjacent ring (Table 1).
ISSN 0108-2701
10-Ethyl-4-oxo-2,3,4,10-tetrahydro-
pyrimido[4,5-b]quinolin-2-iminium
4-toluenesulfonate: a polarized
electronic structure in the cation and
a hydrogen-bonded sheet structure
Jorge Trilleras,a Jairo Quiroga,a John N. Low,b Justo Coboc
and Christopher Glidewelld*
a
´
Departamento de Quımica, Universidad de Valle, AA 25360 Cali, Colombia,
bDepartment of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen
c
´
´
´
AB24 3UE, Scotland, Departamento de Quımica Inorganica y Organica,
Universidad de Jaen, 23071 Jaen, Spain, and dSchool of Chemistry, University of St
´
´
Andrews, Fife KY16 9ST, Scotland
Correspondence e-mail: cg@st-andrews.ac.uk
Received 4 June 2008
Accepted 4 June 2008
Online 14 June 2008
In the title compound, C13H13N4O+ꢀC7H7O3Sꢁ, the bond
distances within the cation provide evidence for the deloca-
lization of the positive charge in a manner reminiscent of
guanidinium cations. Three independent N—Hꢀ ꢀ ꢀO hydrogen
bonds link the ions into centrosymmetric four-ion aggregates,
and these are further linked into sheets by a single C—Hꢀ ꢀ ꢀO
hydrogen bond. This study shows how a single hydrogen bond
can link centrosymmetric entities into a continuous sheet
structure.
Within the cation, the peripheral and exocyclic bond
distances (Table 1) exhibit some interesting values. Amongst
the peripheral C—C distances, the C4a—C5, C6—C7 and
C8—C9 bonds are all significantly shorter than the remainder,
indicating a degree of double-bond fixation. Of the C—N
distances, the exocyclic C2—N2 distance is the shortest by
some margin, the ring C2—N1 and C10a—N1 distances are
longer than C2—N2 and fairly similar to each other, the C2—
N3 and C10a—N10 distances are longer still and are also
similar to each other, the amidic C4—N3 bond is long for its
type with a distance more typical of C—N bonds in bis-acyl
imines (Allen et al., 1987), while C9a—N10 is the longest of all
the C—N bonds. The C2—N2 distance is, in fact, rather typical
of those found in guanidinium cations (Allen et al., 1987) and
Comment
The synthesis and study of fused pyrimidine compounds is of
interest due to the wide variety of their biological and
pharmacological properties. In particular, pyrimidinoquino-
lines have found application as antitumour agents (Chua et al.,
2008; Weissman & Yang, 2007), biocidal agents (Kumar et al.,
2002) and antiallergic agents (Althuis et al., 1980). Compounds
of this type have been prepared from 4,6-dichloro-5-formyl-
pyrimidines using a two-step sequence consisting of a mono-
substitution with aromatic amines (Quiroga et al., 2008)
followed by an acid-catalysed Bradsher-type cycloconden-
sation. The title compound, (I), was isolated in small quantity
from an attempt to induce such a cyclocondensation using
4-toluenesulfonic acid under microwave irradiation.
The title compound is a salt for which the asymmetric unit
was selected so that the two independent ions are linked
within the asymmetric unit by two N—Hꢀ ꢀ ꢀO hydrogen bonds,
which are both almost linear (Fig. 1 and Table 2). The dihedral
angle between the mean plane of the tricyclic ring system of
the cation and the aryl ring of the anion is only 5.4 (2)ꢂ, so that
Figure 1
The two independent ions in the asymmetric unit of compound (I),
showing the atom-labelling scheme. Displacement ellipsoids are drawn at
the 30% probability level and H atoms are shown as small spheres of
arbitrary radii.
o382 # 2008 International Union of Crystallography
doi:10.1107/S0108270108016995
Acta Cryst. (2008). C64, o382–o384

organic compounds
Figure 3
A stereoview of part of the crystal structure of compound (I), showing the
formation of a hydrogen-bonded sheet parallel to (101). For the sake of
clarity, H atoms bonded to C atoms and not participating in the sheet
formation have been omitted.
Figure 2
Part of the crystal structure of compound (I), showing a centrosymmetric
four-ion aggregate. For the sake of clarity, H atoms bonded to C atoms
have been omitted, as has the unit-cell outline. Atoms marked with an
asterisk (*) are at the symmetry position (ꢁx, 1 ꢁ y, 1 ꢁ z).
Experimental
A mixture of 2-amino-4-chloro-6-(N-ethyl-N-phenylamino)pyrimid-
ine-5-carbaldehyde (0.18 mmol) and 4-toluenesulfonic acid mono-
hydrate (0.18 mmol) in ethanol (3 ml) was subjected to microwave
irradiation in a sealed tube under magnetic stirring, using a CEM
monomode microwave reactor (maximum power 300 W, ramp time
15 min, hold time 10 min and maximum temperature 573 K). The
reaction mixture was then cooled in a refrigerator and the resulting
solid, which proved to be a mixture of several products, was collected
by filtration. Recrystallization from ethanol afforded a few crystals of
the title compound as brown blocks, which proved to be suitable for
single-crystal X-ray diffraction (m.p. 537–538 K).
is close in value to the corresponding bond in the cation, (II),
˚
of its sulfate salt [1.3195 (9) A; Cambridge Structural Data-
base (Allen, 2002) refcode HACDEU; Bieri et al., 1993]. This
distance is also consistent with the character of the C4—N3
bond, and these observations suggest that the positive charge
which is formally localized at N2 is, in fact, best described as
delocalized over atoms N2, N3 and N10, as in forms (Ia)–(Ic)
(see scheme). The cation can thus be regarded as a protonated
iminouracil derivative.
As noted above, the two independent ions within the
asymmetric unit of (I) are linked by two N—Hꢀ ꢀ ꢀO hydrogen
bonds, both of which are almost linear. In addition, pairs of
these units are linked by a third N—Hꢀ ꢀ ꢀO hydrogen bond
(Table 2) to form a centrosymmetric four-ion aggregate in
which the central R24(8) (Bernstein et al., 1995) ring is flanked
by two symmetry-equivalent R22(8) rings (Fig. 2). These
aggregates can be regarded as the basic building block for the
structure as a whole and a single C—Hꢀ ꢀ ꢀO hydrogen bond
(Table 2) links these building blocks into sheets.
Crystal data
C13H13N4O+ꢀC7H7O3Sꢁ
3
˚
V = 1902.2 (2) A
Z = 4
Mr = 412.46
Monoclinic, P21=n
Mo Kꢁ radiation
ꢂ = 0.21 mmꢁ1
T = 120 (2) K
0.41 ꢃ 0.40 ꢃ 0.39 mm
˚
a = 9.0213 (7) A
˚
b = 20.2880 (18) A
˚
c = 10.3932 (6) A
ꢀ = 90.245 (5)ꢂ
Data collection
Bruker–Nonius KappaCCD area-
detector diffractometer
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.920, Tmax = 0.924
43973 measured reflections
4370 independent reflections
3363 reflections with I > 2ꢃ(I)
Rint = 0.045
The aryl C23 atoms at (x, y, z) and (ꢁx, 1 ꢁ y, 1 ꢁ z) are
1
1
components of the aggregate centred at (0, , ). These two
atoms act as hydrogen-bond donors to sulfonate O21 atoms at
2
2
Refinement
3
2
1
2
1
2
1
2
1
2
(12 + x, ꢁ y, + z) and (ꢁ ꢁ x, ꢁ + y, ꢁ z), respectively,
R[F2 > 2ꢃ(F2)] = 0.045
wR(F2) = 0.127
S = 1.08
265 parameters
H-atom parameteꢁrs3 constrained
which themselves are components of the aggregates centred at
1
(12, 1, 1) and (ꢁ , 0, 0), respectively. Similarly, the O21 atoms at
˚
(x, y, z) and (ꢁ2x, 1 ꢁ y, 1 ꢁ z) accept hydrogen bonds from the
Áꢄmax = 0.67 e A
ꢁ3
˚
4370 reflections
Áꢄmin = ꢁ0.53 e A
C23 atoms at (ꢁ + x, 23 ꢁ y, ꢁ + z) and (21 ꢁ x, ꢁ + y, 23 ꢁ z),
1
1
1
2
2
2
The space group P21/n was uniquely assigned from the systematic
absences. All H atoms were located in difference maps and then
treated as riding atoms in geometrically idealized positions, with C—
respectively, which are components of the aggregates centred
at (ꢁ , 1, 0) and (12, 0, 1). Propagation of this interaction by the
1
2
space group links the centrosymmetric four-ion aggregates
into a sheet parallel to (101) and built from a combination of
R22(8), R24(8) and R88(40) rings (Fig. 3). Thus, a single hydrogen
bond is sufficient to link the centrosymmetric four-ion entities
into a two-dimensional structure. There are no direction-
specific interactions between adjacent sheets. By contrast, in
HACDEU, where there are nine independent N—H bonds all
participating in hydrogen-bond formation, the overall
hydrogen-bonded supramolecular structure is three-dimen-
sional.
˚
˚
H = 0.95 (aryl), 0.98 (CH3) or 0.99 A (CH2) and N—H = 0.88 A, and
with Uiso(H) = kUeq(carrier), where k = 1.5 for the methyl groups and
1.2 for all other H atoms.
Data collection: COLLECT (Nonius, 1999); cell refinement:
DIRAX/LSQ (Duisenberg et al., 2000); data reduction: EVALCCD
(Duisenberg et al., 2003); program(s) used to solve structure: SIR2004
(Burla et al., 2005); program(s) used to refine structure: OSCAIL
(McArdle, 2003) and SHELXL97 (Sheldrick, 2008); molecular
graphics: PLATON (Spek, 2003); software used to prepare material
for publication: SHELXL97 and PRPKAPPA (Ferguson, 1999).
Trilleras et al. C13H13N4O+ꢀC7H7O3Sꢁ o383
ꢄ
Acta Cryst. (2008). C64, o382–o384

organic compounds
Table 1
Selected geometric parameters (A, ).
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: SK3244). Services for accessing these data are
described at the back of the journal.
ꢂ
˚
N1—C2
C2—N3
N3—C4
C4—C4a
C4a—C5
C5—C5a
C5a—C6
C6—C7
C7—C8
1.346 (2)
1.364 (2)
1.377 (2)
1.473 (3)
1.362 (3)
1.415 (3)
1.410 (3)
1.369 (3)
1.397 (3)
C8—C9
1.376 (3)
1.410 (3)
1.390 (2)
1.365 (2)
1.335 (2)
1.430 (3)
1.416 (3)
1.312 (3)
1.217 (2)
C9—C9a
C9a—N10
N10—C10a
C10a—N1
C4a—C10a
C5a—C9a
C2—N2
References
Allen, F. H. (2002). Acta Cryst. B58, 380–388.
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor,
R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.
Althuis, T. H., Kadin, S. B., Czuba, L. J., Moore, P. F. & Hess, H. J. (1980). J.
Med. Chem. 23, 262–269.
C4—O4
C9a—N10—C101—C102 ꢁ86.8 (2)
C10a—N10—C101—C102
91.7 (2)
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem.
Int. Ed. Engl. 34, 1555–1573.
Bieri, J. H., Prewo, R. & Linden, A. (1993). Private communication to the CSD
(refcode HACDEU). CCDC, Union Road, Cambridge, England.
Burla, M. C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G. L., De
Caro, L., Giacovazzo, C., Polidori, G. & Spagna, R. (2005). J. Appl. Cryst. 38,
381–388.
Table 2
Hydrogen-bond geometry (A, ).
ꢂ
˚
D—Hꢀ ꢀ ꢀA
D—H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
Chua, P., Pierre, F. & Whitten, J. P. (2008). PCT Int. Appl. WO 200802-
8168.
Duisenberg, A. J. M., Hooft, R. W. W., Schreurs, A. M. M. & Kroon, J. (2000).
J. Appl. Cryst. 33, 893–898.
Duisenberg, A. J. M., Kroon-Batenburg, L. M. J. & Schreurs, A. M. M. (2003).
J. Appl. Cryst. 36, 220–229.
Ferguson, G. (1999). PRPKAPPA. University of Guelph, Canada.
Kumar, R. N., Suresh, T. & Mohan, P. S. (2002). Asian J. Chem. 14, 1405–
1408.
N2—H2Aꢀ ꢀ ꢀO23i
N2—H2Bꢀ ꢀ ꢀO23
N3—H3ꢀ ꢀ ꢀO22
0.88
0.88
0.88
0.95
2.03
2.11
1.92
2.37
2.855 (2)
2.976 (2)
2.799 (2)
3.299 (3)
156
166
174
164
C23—H23ꢀ ꢀ ꢀO21ii
1
2
3
2
1
2
Symmetry codes: (i) ꢁx; ꢁy þ 1; ꢁz þ 1; (ii) x þ ; ꢁy þ ; z þ .
McArdle, P. (2003). OSCAIL for Windows. Version 10. Crystallography
Centre, Chemistry Department, NUI Galway, Ireland.
Nonius (1999). COLLECT. Nonius BV, Delft, The Netherlands.
´
The authors thank the Servicios Tecnicos de Investigacion
of the Universidad de Jaen and the staff for data collection. JC
´
´
´
Quiroga, J., Trilleras, J., Insuasty, B., Abonıa, R., Nogueras, M., Marchal, A. &
Cobo, J. (2008). Tetrahedron Lett. 49, 3257–3259.
´
´
thanks the Consejerıa de Innovacion, Ciencia y Empresa
´
´
¨
(Junta de Andalucıa, Spain) and the Universidad de Jaen for
financial support. JT and JQ thank COLCIENCIAS and
UNIVALLE (Universidad del Valle, Colombia) for financial
support.
Sheldrick, G. M. (2003). SADABS. Version 2.10. University of Gottingen,
Germany.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13.
Weissman, A. & Yang, Y. (2007). PCT Int. Appl. WO 2007146375.
o384 Trilleras et al. C13H13N4O+ꢀC7H7O3Sꢁ
Acta Cryst. (2008). C64, o382–o384
ꢄ