2,5-Dimethyl-6,7-dihydro-benzo[h]-pyrazolo[1,5-a]quinazoline and 2-tert-butyl-5-methyl-6,7-dihydro-benzo[h]pyrazolo[1,5-a]quinazoline

Article abstract of DOI:10.1107/S0108270107029010

In both 2,5-dimethyl-6,7-dihydro-benzo[h]pyrazolo[1,5-a]-quinazoline, C16H15N3, (I), and 2-tert-butyl-5-methyl-6,7-dihydro-benzo[h]pyrazolo[1,5-a] quinazoline, C19H21N3, (II), which crystallizes with Z′ = 2 in the space group P, the non-aromatic carbocyclic rings adopt screw-boat conformations. The mol-ecules of (I) are linked into chains of rings by a combination of C - H...N and C - H...π(arene) hydrogen bonds, while in (II) there are no hydrogen bonds of any kind. International Union of Crystallography 2007.

Full text of DOI:10.1107/S0108270107029010

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
where n represents zero or an integer (Evans & Boeyens,
1989). Similar conformations have been found for the corre-
sponding rings in compounds (III)±(V) (Low et al., 2004;
Portilla et al., 2005). Because of the puckering of the non-
aromatic carbocyclic rings, the molecules exhibit no internal
symmetry and hence they are chiral; however, the centro-
symmetric space group in each case accommodates equal
numbers of the two enantiomeric forms.
ISSN 0108-2701
2,5-Dimethyl-6,7-dihydrobenzo[h]-
pyrazolo[1,5-a]quinazoline and 2-tert-
butyl-5-methyl-6,7-dihydrobenzo[h]-
pyrazolo[1,5-a]quinazoline
Jaime Portilla,a Jairo Quiroga,a Justo Cobo,b John N. Lowc
and Christopher Glidewelld*
a
Â
Â
Â
Grupo de Investigacion de Compuestos Heterocõclicos, Departamento de Quõmica,
b
Â
Â
Universidad de Valle, AA 25360, Colombia, Departamento de Quõmica Inorganica
y Organica, Universidad de Jaen, 23071 Jaen, Spain, cDepartment of Chemistry,
University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and
dSchool of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland
Correspondence e-mail: cg@st-andrews.ac.uk
Â
Â
Â
Received 4 June 2007
Accepted 13 June 2007
Online 14 July 2007
In both 2,5-dimethyl-6,7-dihydrobenzo[h]pyrazolo[1,5-a]-
quinazoline, C16H15N3, (I), and 2-tert-butyl-5-methyl-6,7-
dihydrobenzo[h]pyrazolo[1,5-a]quinazoline, C19H21N3, (II),
which crystallizes with Z0 = 2 in the space group P1, the non-
aromatic carbocyclic rings adopt screw-boat conformations.
The molecules of (I) are linked into chains of rings by a
combination of CÐHÁ Á ÁN and CÐHÁ Á Áꢀ(arene) hydrogen
bonds, while in (II) there are no hydrogen bonds of any kind.
Within the heterobicyclic portions of the molecules, the
patterns of the bond distances (Tables 1 and 3) are very similar
for all three molecules. Hence, we discuss in detail only the
distances in (I) as similar remarks apply to (II). In (I), the
N1ÐC2 and C3AÐN4 bonds, which are formally double and
single bonds, respectively, are effectively of the same length;
on the other hand, the C5ÐC5A bond, which is formally a
single bond, is signi®cantly longer than the C2ÐC3 and C5AÐ
C11B bonds, which are formally double bonds. These obser-
vations are consistent with bond-®xation of the type char-
acteristic of naphthalene rather than complete peripheral
Comment
We report here the structures of two closely related 6,7-
dihydrobenzo[h]pyrazolo[1,5-a]quinazolines, (I) and (II)
(Figs. 1 and 2), both prepared using solvent-free cyclo-
condensation reactions between 2-acetyltetralone and the
appropriate 3-alkyl-5-amino-1H-pyrazole. We compare the
molecular and supramolecular structures of compounds (I)
and (II) with those of the related aryl compounds (III) and
(IV) (Portilla et al., 2005) and with that of compound (V) (Low
et al., 2004) (see scheme).
In (I) and in each of the independent molecules of (II), the
non-aromatic carbocyclic rings adopt a screw-boat confor-
mation. The ring-puckering amplitudes (Cremer & Pople,
Ê
Ê
1975) are 0.506 (2) A in (I), and 0.481 (2) and 0.482 (3) A,
respectively, for the molecules of types 1 and 2 (containing
atoms N11 and N21, respectively, see Fig. 2) in (II). In (I), the
corresponding ring-puckering angles are ꢁ = 69.0 (2)ꢀ and ' =
82.6 (3)ꢀ for the atom sequence C5AÐC6ÐC7ÐC7AÐ
C11AÐC11B; in (II), for the atom sequences Cx1AÐCx1BÐ
Cx5AÐCx6ÐCx7ÐCx7A, ꢁ = 67.5 (2)ꢀ and ' = 210.6 (3)ꢀ
when x = 1 (molecule 1), and ꢁ = 67.0 (2)ꢀ and ' = 213.4 (3)ꢀ
when x = 2 (molecule 2). For an idealized screw-boat
conformation, the values are ꢁ = 67.5ꢀ and ' = (60n + 30)ꢀ,
Figure 1
A molecule of (I), showing the atom-labelling scheme. Displacement
ellipsoids are drawn at the 30% probability level.
o458 # 2007 International Union of Crystallography
DOI: 10.1107/S0108270107029010
Acta Cryst. (2007). C63, o458±o461

organic compounds
delocalization of the ten ꢀ electrons. By contrast, the distances
in the carbocylic ring (C7A/C8±C11/C11A) are indicative of
typical aromatic delocalization.
(1
x, y, 2
z), so generating by inversion a cyclic
centrosymmetric R22(8) (Bernstein et al., 1995) dimer centred
at (12, 0, 1). At the same time, atom C7 in the molecule at (x, y,
z) acts as a hydrogen-bond donor, via the axial atom H7B, to
the C7A/C8±C11/C11A ring in the molecule at (1 x, 1 y,
The geometries and conformations of the two independent
molecules in (II) are very similar. Although the ADDSYM
routine in PLATON (Spek, 2003) indicated that no additional
crystallographic symmetry is present in (II), examination of
the atom coordinates showed that the two independent mol-
ecules are approximately related by a pseudo-c-glide plane at
x = 0.25. Consistent with this approximate relationship, the
re¯ections of type 0kl are, in general, very much weaker when
l is odd than when l is even, although some exhibit signi®cant
intensity.
1
z), thus generating by inversion a second cyclic motif
centred at (12, 21, 12 ). The propagation by inversion of these two
hydrogen bonds therefore leads to the formation of a chain of
centrosymmetric hydrogen-bonded rings running parallel to
the [011] direction, with the rings formed by pairs of CÐ
HÁ Á ÁN hydrogen bonds centred at (12, n, 1
n) (where n
represents zero or an integer) alternating with the rings
formed by pairs of CÐHÁ Á Áꢀ(arene) hydrogen bonds centred
1
1
Two hydrogen bonds (Table 2) link the molecules of (I) into
chains of rings. Atom C3 in the molecule at (x, y, z) acts as a
hydrogen-bond donor to the ring atom N4 in the molecule at
at (12, + n,
n) (where n represents zero or an integer)
2
2
(Fig. 3). There is a very weak ꢀ±ꢀ stacking interaction
between pairs of pyrimidine rings. These rings in the molecules
at (x, y, z) and (1 x, 1 y, 2 z) are strictly parallel, with an
Ê
interplanar spacing of 3.354 (2) A; the ring-centroid separa-
Ê
tion is 3.840 (2) A, corresponding to a ring-centroid offset of
Ê
1.870 (2) A. If this interaction is regarded as signi®cant, its
action is to link the hydrogen-bonded chains into a sheet
parallel to (100).
The supramolecular aggregation in (II), by contrast, is
extremely simple. There are no hydrogen bonds of any kind in
the structure, but the molecules of type 1 are linked into pairs
by a single weak ꢀ±ꢀ stacking interaction between the
benzene rings of the molecules at (x, y, z) and ( x, y, z).
Ê
The interplanar spacing is 3.395 (2) A and the ring-centroid
Ê
separation is 3.974 (2) A, which corresponds to a ring-centroid
Ê
offset of 1.867 (2) A. There are no direction-speci®c inter-
actions of any kind involving the molecules of type 2.
The stacking interaction in (II) closely resembles that in the
4-methylphenyl analogue (IV) (Portilla et al., 2005), where
pairs of molecules are again linked into isolated dimers. In the
unsubstituted phenyl compound (III), the molecules are
linked into chains by a combination of a CÐHÁ Á Áꢀ(arene)
hydrogen bond and a ꢀ±ꢀ stacking interaction. The
Figure 2
The two independent molecules of compound (II), showing the atom-
labelling scheme for (a) a molecule of type 1 containing atom N11 and (b)
a molecule of type 2 containing atom N21. Displacement ellipsoids are
drawn at the 30% probability level.
Figure 3
A stereoview of part of the crystal structure of (I), showing the formation
of a hydrogen-bonded chain of rings along [011]. For the sake of clarity, H
atoms not involved in the motifs shown have been omitted.
ꢁ
Acta Cryst. (2007). C63, o458±o461
Portilla et al. C16H15N3 and C19H21N3 o459

organic compounds
4-chlorophenyl derivative (V) crystallizes with Z0 = 2 (Low et
al., 2004), and the molecules are linked by two independent
ꢀ±ꢀ stacking interactions into chains in which the two types of
molecules alternate.
Compound (II)
Crystal data
C19H21N3
ꢄ = 102.791 (6)ꢀ
V = 1523.66 (14) A
Z = 4
3
Ê
Mr = 291.39
Triclinic, P1
a = 11.2632 (5) A
Ê
Ê
Mo Kꢂ radiation
1
Experimental
b = 11.4574 (7) A
ꢅ = 0.08 mm
T = 120 (2) K
Ê
c = 12.1317 (6) A
Equimolar quantities (2.6 mmol of each component) of 2-acetyl-
tetralone and either 5-amino-3-methyl-1H-pyrazole [for (I)] or 5-am-
ino-3-tert-butyl-1H-pyrazole [for (II)] were thoroughly mixed at
room temperature. The solvent-free mixtures were then heated in an
oil bath at 393 K for 1.5±2 min. The resulting melts were stirred
brie¯y and then allowed to cool to ambient temperature to solidify.
The resulting solids were extracted with ethanol and, after removal of
the solvent under reduced pressure, the products (I) and (II) were
recrystallized from dimethylformamide to give crystals suitable for
single-crystal X-ray diffraction. (I): pale orange crystals, yield 86%,
m.p. 385±387 K; MS (70 eV) m/z (%): 249 (100, M+), 234 (8), 221 (9),
127 (16), 39 (22). (II): pale yellow crystals, yield 84%, m.p. 439±441 K;
MS (70 eV) m/z (%): 291 (96, M+), 276 (92), 246 (100), 128 (25),
57 (25), 41 (57), 39 (56).
ꢂ = 93.449 (5)ꢀ
ꢃ = 90.313 (4)ꢀ
0.52 Â 0.35 Â 0.15 mm
Data collection
Bruker±Nonius KappaCCD
diffractometer
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.972, Tmax = 0.989
37817 measured re¯ections
6991 independent re¯ections
4144 re¯ections with I > 2ꢆ(I)
Rint = 0.061
Re®nement
R[F2 > 2ꢆ(F2)] = 0.065
wR(F2) = 0.213
S = 1.06
405 parameters
H-atom parameters constrained
3
Ê
Áꢇmax = 0.42 e A
3
Ê
0.39 e A
6991 re¯ections
Áꢇmin
=
Table 3
Selected bond lengths (A) for (II).
Compound (I)
Ê
Crystal data
N11ÐC12
C12ÐC13
C13ÐC13A
C13AÐN14
N14ÐC15
C15ÐC15A
C15AÐC11B
C11BÐN11C
N11CÐN11
C13AÐN11C
1.347 (3)
1.404 (3)
1.383 (3)
1.353 (3)
1.324 (3)
1.424 (3)
1.377 (3)
1.381 (3)
1.364 (3)
1.389 (3)
N21ÐC22
C22ÐC23
C23ÐC23A
C23AÐN24
N24ÐC25
C25ÐC25A
C25AÐC21B
C21BÐN21C
N21CÐN21
C23AÐN21C
1.345 (3)
1.399 (3)
1.379 (3)
1.355 (3)
1.323 (3)
1.430 (3)
1.375 (3)
1.373 (3)
1.365 (3)
1.393 (3)
C16H15N3
ꢄ = 89.941 (17)ꢀ
3
Ê
V = 623.4 (3) A
Mr = 249.31
Triclinic, P1
a = 7.9430 (19) A
Z = 2
Mo Kꢂ radiation
Ê
Ê
1
b = 7.9660 (11) A
Ê
ꢅ = 0.08 mm
T = 120 (2) K
c = 9.943 (3) A
ꢂ = 87.637 (13)ꢀ
ꢃ = 82.632 (18)ꢀ
0.49 Â 0.44 Â 0.07 mm
Data collection
Bruker±Nonius KappaCCD
diffractometer
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.971, Tmax = 0.994
15496 measured re¯ections
2867 independent re¯ections
1600 re¯ections with I > 2ꢆ(I)
Rint = 0.074
Crystals of both (I) and (II) are triclinic, and for each the space
group P1 was selected and con®rmed by the structure analysis. All H
atoms were located in difference maps and then treated as riding
atoms in geometrically idealized positions, with CÐH distances of
Re®nement
R[F2 > 2ꢆ(F2)] = 0.067
wR(F2) = 0.220
S = 1.04
174 parameters
H-atom parameters constrained
Ê
0.95 (aromatic), 0.98 (CH3) or 0.99 A (CH2), and with Uiso(H) =
3
kUeq(C), where k = 1.5 for the methyl groups and k = 1.2 for all other
H atoms. A search for possible additional symmetry in (II) revealed
none.
Ê
Áꢇmax = 0.42 e A
3
Ê
0.29 e A
2867 re¯ections
Áꢇmin
=
For both compounds, data collection: COLLECT (Hooft, 1999);
cell re®nement: DIRAX/LSQ (Duisenberg et al., 2000); data reduc-
tion: EVALCCD (Duisenberg et al., 2003); program(s) used to solve
structure: SIR2004 (Burla et al., 2005); program(s) used to re®ne
structure: OSCAIL (McArdle, 2003) and SHELXL97 (Sheldrick,
1997); molecular graphics: PLATON (Spek, 2003); software used to
prepare material for publication: SHELXL97 and PRPKAPPA
(Ferguson, 1999).
Table 1
Selected bond lengths (A) for (I).
Ê
N1ÐC2
C2ÐC3
1.350 (3)
1.385 (4)
1.370 (3)
1.351 (3)
1.320 (3)
C5ÐC5A
1.423 (3)
1.379 (3)
1.372 (3)
1.360 (3)
1.402 (3)
C5AÐC11B
C11BÐN11C
N11CÐN1
C3ÐC3A
C3AÐN4
N4ÐC5
C3AÐN11C
Table 2
Hydrogen-bond geometry (A, ) for (I).
ꢀ
Ê
 Â
The authors thank `Servicios Tecnicos de Investigacion of
Â
Universidad de Jaen' and the staff for data collection. JC
thanks the Consejerõa de Innovacion, Ciencia y Empresa
Cg is the centroid of the C7A/C8±C11/C11A ring.
Â
Â
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
Â
Â
(Junta de Andalucõa, Spain) and the Universidad de Jaen for
®nancial support. JP and JQ thank COLCIENCIAS and
UNIVALLE (Universidad del Valle, Colombia) for ®nancial
support.
C3ÐH3Á Á ÁN4i
0.95
0.99
2.55
2.97
3.495 (3)
3.789 (3)
175
141
C7ÐH7BÁ Á ÁCgii
Symmetry codes: (i) x ‡ 1; y; z ‡ 2; (ii) x ‡ 1; y ‡ 1; z ‡ 1.
ꢁ
o460 Portilla et al. C16H15N3 and C19H21N3
Acta Cryst. (2007). C63, o458±o461

organic compounds
Duisenberg, A. J. M., Kroon-Batenburg, L. M. J. & Schreurs, A. M. M. (2003).
J. Appl. Cryst. 36, 220±229.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: SK3137). Services for accessing these data are
described at the back of the journal.
Evans, D. G. & Boeyens, J. C. A. (1989). Acta Cryst. B45, 581±590.
Ferguson, G. (1999). PRPKAPPA. University of Guelph, Canada.
Hooft, R. W. W. (1999). COLLECT. Nonius BV, Delft, The Netherlands.
Low, J. N., Cobo, J., Quiroga, J., Portilla, J. & Glidewell, C. (2004). Acta Cryst.
C60, o604±o607.
McArdle, P. (2003). OSCAIL for Windows. Version 10. Crystallography
Centre, Chemistry Department, NUI Galway, Ireland.
Portilla, J., Quiroga, J., Cobo, J., Nogueras, M., Low, J. N. & Glidewell, C.
(2005). Acta Cryst. C61, o398±o403.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of
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Acta Cryst. (2007). C63, o458±o461
Portilla et al. C16H15N3 and C19H21N3 o461