organic compounds
3-(4-Methoxyphenyl)-7,7-dimethyl-1,6,7,8-tetrahydropyrazolo[3,4-b]quinolin-5-one: a chain of centrosymmetric rings built from N—H⋯N and C—H⋯π(arene) hydrogen bonds
aDepartamento de Química, Universidad de Nariño, Ciudad Universitaria, Torobajo, AA 1175 Pasto, Colombia, bGrupo de Investigación de Compuestos Heterocíclicos, Departamento de Química, Universidad de Valle, AA 25360 Cali, Colombia, cDepartamento de Química Inorgánica y Orgánica, Universidad de Jaén, 23071 Jaén, Spain, dDepartment of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and eSchool of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland
*Correspondence e-mail: cg@st-andrews.ac.uk
In the title compound, C19H19N3O2, the non-aromatic carbocylic ring adopts an The molecules are linked by a combination of N—H⋯N and C—H⋯π(arene) hydrogen bonds into a chain of centrosymmetric rings.
Comment
Pyrazolo[3,4-b]quinolines are of interest because of their pharmacological applications, e.g. as antiviral agents (Crenshaw et al., 1976; Smirnoff & Crenshaw, 1977). We have recently reported several efficient methods for the synthesis of compounds of this type, using the reactions between 5-aminopyrazoles, 5,5-dimethylcyclohexane-1,3-dione (dimedone) and substituted benzaldehydes, both in solution and under solvent-free conditions, using microwave irradiation (Quiroga, Hormaza et al., 1998; Quiroga, Insuasty et al., 1998). We report here the molecular and supramolecular structures of the title compound, (I) (Fig. 1), synthesized using microwave irradiation in the absence of solvent. The structures of several analogous compounds have been reported recently, including those of (II), in both triclinic (Low et al., 2003) and monoclinic polymorphs (Mera et al., 2005), (III) (Low et al., 2004) and (IV) (Low et al., 2005), but in none of compounds (II)–(IV) is there an N—H bond at pyrazole atom N1, as found in compound (I). Hence, the supramolecular aggregation in (I) is necessarily different from those found in (II)–(IV).
The bond lengths in (I) (Table 1) show clear evidence for electronic delocalization in the pyridine ring with significant bond fixation in the pyrazole ring. Methoxy atom C341 is almost coplanar with the adjacent aryl ring, while the exocyclic bond angles at C34 show the usual difference of ca 10°. The
dihedral angle between the aryl and pyrazole rings is 13.4 (2)°. Within the non-aromatic carbocyclic ring, the ring-puckering parameters (Cremer & Pople, 1975) corresponding to the atom sequence C4a—C5—C6—C7—C8—C8a are θ = 55.1 (4)° and φ = 167.4 (4)°, indicating a conformation close to an envelope form, for which the idealized parameters are θ = 54.7° and φ = (60n)°. The ring is folded across the C6⋯C8 vector.The molecules of (I) are linked into a chain of rings by a combination of N—H⋯N and C—H⋯π(arene) hydrogen bonds (Table 2). Pyrazole atom N1 in the molecule at (x, y, z) acts as hydrogen-bond donor to pyridine atom N9 in the molecule at (2 − x, 1 − y, 1 − z), so generating by inversion an R22(8) (Bernstein et al., 1995) ring centred at (1, , ). In addition, atom C8 in the molecule at (x, y, z) acts as hydrogen-bond donor, via axial atom H8B, to the aryl ring C31–C36 in the molecule at (1 − x, 1 − y, 1 − z), so forming a second cyclic motif, this time centred at (, , ). Propagation by inversion of these two hydrogen bonds then generates a chain of rings running parallel to the [100] direction, with R22(8) rings centred at (n, , ) (n = zero or integer) and rings generated by the C—H⋯π(arene) hydrogen bond centred at (n + , , ) (n = zero or integer) (Fig. 2). The formation of this chain is reinforced by a π–π stacking interaction involving the pyridine rings of the molecules at (x, y, z) and (1 − x, 1 − y, 1 − z). These rings are strictly parallel, with an interplanar spacing of 3.310 (2) Å. The ring-centroid separation is 3.709 (2) Å, corresponding to a ring offset of 1.674 (2) Å. There are no direction-specific interactions between adjacent chains.
We briefly compare here the supramolecular aggregation in compound (I) with that found in each of compounds (II)–(IV). In the monoclinic polymorph of compound (II), which crystallizes with Z′ = 1 in the P21/n (Mera et al., 2005), two distinct C—H⋯π hydrogen bonds link the molecules into chains of rings, which are further linked into sheets by π–π stacking interactions. By contrast, in the triclinic polymorph of (II), which crystallizes with Z′ = 2 in the P (Low et al., 2003), each type of molecule forms a distinct chain built from a combination of C—H⋯O and C—H⋯π hydrogen bonds. In compound (III), the molecules are linked by a single C—H⋯N hydrogen bond to form simple C(6) chains (Low et al., 2004), while in compound (IV) the molecules are linked into isolated centrosymmetric dimers by two distinct C—H⋯π hydrogen bonds (Low et al., 2005). Thus, no two members of this series show the same pattern of supramolecular aggregation, confirming that such aggregation is very sensitive to the details of the substituents on the heterocyclic ring system.
Experimental
Equimolar quantities (1 mmol of each component) of 5-amino-3-(4-methoxyphenyl)pyrazole, 5,5-dimethylcyclohexane-1,3-dione and formaldehyde (as a 37% aqueous solution) were placed in an open Pyrex glass vessel and irradiated in a domestic microwave oven for 6 min at 600 W. The product mixture was extracted with ethanol and after removal of the solvent, the resulting product, (I), was recrystallized from ethanol to give crystals suitable for single-crystal X-ray diffraction (m.p. 566–567 K, yield 65%). MS (70 eV) m/z (%): 321 (M+, 66), 306 [(M − CH3)+, 100], 222 (33), 134 (89), 77 (13), 39 (24).
Crystal data
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Refinement
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Crystals of compound (I) are triclinic; the P was chosen and confirmed by the successful structure analysis. All H atoms were located in difference maps and then treated as riding atoms, with C—H distances of 0.95 (aromatic), 0.98 (CH3) or 0.99 Å (CH2), an N—H distance of 0.88 Å, and Uiso(H) = 1.2Ueq(C,N), or 1.5Ueq(C) for the methyl groups.
Data collection: COLLECT (Nonius, 1999); cell DENZO (Otwinowski & Minor, 1997) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine 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).
Supporting information
10.1107/S0108270106025522/sk3039sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S0108270106025522/sk3039Isup2.hkl
Equimolar quantities (1 mmol of each component) of 5-amino-3-(4-methoxyphenyl)pyrazole, 5,5-dimethylcyclohexane-1,3-dione and formaldehyde (as a 37% aqueous solution) were placed in an open Pyrex glass vessel and irradiated in a domestic microwave oven for 6 min at 600 W. The product mixture was extracted with ethanol and after removal of the solvent, the resulting product, (I), was recrystallized from ethanol to give crystals suitable for single-crystal X-ray diffraction (m.p. 566–567 K, yield 65%). MS (70 eV) m/z (%), 321 (M+, 66), 306 [(M - CH3)+, 100], 222?(33), 134?(89), 77?(13), 39?(24).
Crystals of compound (I) are triclinic; the 1 was chosen, and confirmed by the successful structure analysis. All H atoms were located in difference maps and then treated as riding atoms, with C—H distances of 0.95 (aromatic), 0.98 (CH3) or 0.99 Å (CH2), and an N—H distance of 0.88 Å, and with Uiso(H) = 1.2Ueq(C,N), or 1.5Ueq(C) for the methyl groups.
PData collection: COLLECT (Nonius, 1999); cell
DENZO (Otwinowski & Minor, 1997) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine 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).C19H19N3O2 | Z = 2 |
Mr = 321.37 | F(000) = 340 |
Triclinic, P1 | Dx = 1.308 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.1510 (6) Å | Cell parameters from 3721 reflections |
b = 9.7680 (7) Å | θ = 3.5–27.5° |
c = 12.3780 (8) Å | µ = 0.09 mm−1 |
α = 72.094 (5)° | T = 120 K |
β = 83.529 (4)° | Lath, colourless |
γ = 85.055 (4)° | 0.20 × 0.10 × 0.03 mm |
V = 816.28 (10) Å3 |
Bruker Nonius KappaCCD area-detector diffractometer | 3721 independent reflections |
Radiation source: Bruker-Nonius FR591 rotating anode | 2099 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.108 |
Detector resolution: 9.091 pixels mm-1 | θmax = 27.5°, θmin = 3.5° |
ϕ and ω scans | h = −9→9 |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | k = −12→12 |
Tmin = 0.977, Tmax = 0.997 | l = −15→16 |
17481 measured reflections |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.074 | H-atom parameters constrained |
wR(F2) = 0.160 | w = 1/[σ2(Fo2) + (0.0572P)2 + 0.2906P] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max < 0.001 |
3721 reflections | Δρmax = 0.26 e Å−3 |
218 parameters | Δρmin = −0.18 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.036 (6) |
C19H19N3O2 | γ = 85.055 (4)° |
Mr = 321.37 | V = 816.28 (10) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.1510 (6) Å | Mo Kα radiation |
b = 9.7680 (7) Å | µ = 0.09 mm−1 |
c = 12.3780 (8) Å | T = 120 K |
α = 72.094 (5)° | 0.20 × 0.10 × 0.03 mm |
β = 83.529 (4)° |
Bruker Nonius KappaCCD area-detector diffractometer | 3721 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 2099 reflections with I > 2σ(I) |
Tmin = 0.977, Tmax = 0.997 | Rint = 0.108 |
17481 measured reflections |
R[F2 > 2σ(F2)] = 0.074 | 0 restraints |
wR(F2) = 0.160 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.26 e Å−3 |
3721 reflections | Δρmin = −0.18 e Å−3 |
218 parameters |
x | y | z | Uiso*/Ueq | ||
N1 | 0.8449 (3) | 0.3499 (2) | 0.56302 (16) | 0.0362 (5) | |
N2 | 0.7495 (3) | 0.2317 (2) | 0.62560 (16) | 0.0370 (5) | |
C3 | 0.6037 (3) | 0.2260 (2) | 0.56934 (19) | 0.0325 (6) | |
C31 | 0.4783 (3) | 0.1064 (2) | 0.61535 (19) | 0.0320 (6) | |
C32 | 0.3040 (3) | 0.1065 (3) | 0.5758 (2) | 0.0380 (6) | |
C33 | 0.1874 (4) | −0.0076 (3) | 0.6223 (2) | 0.0406 (6) | |
C34 | 0.2451 (4) | −0.1255 (3) | 0.7085 (2) | 0.0386 (6) | |
O34 | 0.1450 (3) | −0.24533 (19) | 0.75828 (16) | 0.0515 (5) | |
C341 | −0.0270 (4) | −0.2543 (3) | 0.7151 (3) | 0.0546 (8) | |
C35 | 0.4177 (4) | −0.1267 (3) | 0.7502 (2) | 0.0456 (7) | |
C36 | 0.5311 (4) | −0.0123 (3) | 0.7045 (2) | 0.0406 (6) | |
C3a | 0.6023 (3) | 0.3451 (2) | 0.46651 (18) | 0.0311 (5) | |
C4 | 0.4953 (3) | 0.4027 (2) | 0.37388 (19) | 0.0321 (6) | |
C4a | 0.5550 (3) | 0.5250 (2) | 0.28986 (19) | 0.0310 (5) | |
C5 | 0.4408 (4) | 0.5911 (3) | 0.1919 (2) | 0.0393 (6) | |
O5 | 0.2986 (3) | 0.5368 (2) | 0.18253 (15) | 0.0582 (6) | |
C6 | 0.5056 (4) | 0.7290 (3) | 0.1078 (2) | 0.0429 (7) | |
C7 | 0.7206 (4) | 0.7351 (3) | 0.08807 (19) | 0.0377 (6) | |
C71 | 0.8045 (4) | 0.6166 (3) | 0.0377 (2) | 0.0549 (8) | |
C72 | 0.7733 (4) | 0.8819 (3) | 0.0066 (2) | 0.0517 (7) | |
C8a | 0.7237 (3) | 0.5885 (2) | 0.29668 (18) | 0.0310 (5) | |
C8 | 0.7964 (3) | 0.7156 (3) | 0.20328 (19) | 0.0368 (6) | |
N9 | 0.8268 (3) | 0.5376 (2) | 0.38620 (16) | 0.0325 (5) | |
C9a | 0.7617 (3) | 0.4207 (3) | 0.46696 (19) | 0.0314 (6) | |
H1 | 0.9473 | 0.3766 | 0.5827 | 0.043* | |
H32 | 0.2636 | 0.1866 | 0.5156 | 0.046* | |
H33 | 0.0679 | −0.0045 | 0.5946 | 0.049* | |
H34A | −0.0830 | −0.3455 | 0.7584 | 0.082* | |
H34B | −0.0033 | −0.2499 | 0.6346 | 0.082* | |
H34C | −0.1140 | −0.1737 | 0.7223 | 0.082* | |
H35 | 0.4577 | −0.2070 | 0.8104 | 0.055* | |
H36 | 0.6482 | −0.0144 | 0.7345 | 0.049* | |
H4 | 0.3843 | 0.3591 | 0.3686 | 0.038* | |
H6B | 0.4533 | 0.8106 | 0.1354 | 0.052* | |
H6A | 0.4546 | 0.7410 | 0.0341 | 0.052* | |
H71A | 0.7710 | 0.5224 | 0.0902 | 0.082* | |
H71B | 0.9420 | 0.6208 | 0.0262 | 0.082* | |
H71C | 0.7544 | 0.6304 | −0.0356 | 0.082* | |
H72A | 0.7190 | 0.9580 | 0.0389 | 0.077* | |
H72B | 0.7239 | 0.8958 | −0.0670 | 0.077* | |
H72C | 0.9108 | 0.8861 | −0.0044 | 0.077* | |
H8A | 0.9357 | 0.7046 | 0.1940 | 0.044* | |
H8B | 0.7621 | 0.8038 | 0.2261 | 0.044* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0302 (11) | 0.0403 (12) | 0.0358 (11) | −0.0039 (9) | −0.0101 (9) | −0.0049 (10) |
N2 | 0.0361 (12) | 0.0370 (12) | 0.0362 (11) | −0.0001 (9) | −0.0104 (9) | −0.0063 (10) |
C3 | 0.0340 (13) | 0.0356 (14) | 0.0289 (12) | 0.0045 (11) | −0.0073 (10) | −0.0114 (11) |
C31 | 0.0359 (14) | 0.0315 (13) | 0.0279 (12) | 0.0020 (10) | −0.0037 (10) | −0.0087 (11) |
C32 | 0.0419 (15) | 0.0350 (14) | 0.0333 (13) | 0.0006 (11) | −0.0088 (11) | −0.0035 (11) |
C33 | 0.0384 (15) | 0.0411 (15) | 0.0414 (14) | −0.0025 (12) | −0.0087 (12) | −0.0091 (13) |
C34 | 0.0479 (16) | 0.0322 (14) | 0.0340 (14) | −0.0048 (12) | −0.0015 (12) | −0.0079 (12) |
O34 | 0.0570 (12) | 0.0396 (11) | 0.0525 (11) | −0.0119 (9) | −0.0041 (9) | −0.0035 (9) |
C341 | 0.0459 (17) | 0.0500 (18) | 0.068 (2) | −0.0109 (14) | 0.0032 (15) | −0.0196 (16) |
C35 | 0.0569 (18) | 0.0360 (15) | 0.0390 (15) | 0.0006 (13) | −0.0135 (13) | −0.0016 (12) |
C36 | 0.0452 (15) | 0.0367 (15) | 0.0386 (14) | −0.0013 (12) | −0.0130 (12) | −0.0064 (12) |
C3a | 0.0335 (13) | 0.0334 (13) | 0.0276 (12) | −0.0001 (10) | −0.0052 (10) | −0.0104 (11) |
C4 | 0.0345 (13) | 0.0329 (13) | 0.0322 (13) | −0.0013 (10) | −0.0070 (10) | −0.0134 (11) |
C4a | 0.0334 (13) | 0.0330 (13) | 0.0270 (12) | 0.0005 (10) | −0.0077 (10) | −0.0083 (11) |
C5 | 0.0423 (15) | 0.0428 (15) | 0.0341 (14) | −0.0052 (12) | −0.0108 (12) | −0.0099 (12) |
O5 | 0.0580 (13) | 0.0633 (13) | 0.0503 (12) | −0.0203 (10) | −0.0291 (10) | 0.0001 (10) |
C6 | 0.0481 (16) | 0.0424 (15) | 0.0363 (14) | −0.0041 (12) | −0.0158 (12) | −0.0044 (12) |
C7 | 0.0449 (15) | 0.0370 (14) | 0.0295 (13) | −0.0040 (11) | −0.0069 (11) | −0.0057 (11) |
C71 | 0.074 (2) | 0.0538 (18) | 0.0383 (15) | −0.0075 (15) | 0.0022 (14) | −0.0175 (14) |
C72 | 0.0618 (19) | 0.0472 (17) | 0.0392 (15) | −0.0104 (14) | −0.0107 (14) | 0.0012 (13) |
C8a | 0.0316 (13) | 0.0336 (13) | 0.0283 (12) | 0.0010 (10) | −0.0047 (10) | −0.0102 (11) |
C8 | 0.0378 (14) | 0.0377 (14) | 0.0347 (13) | −0.0027 (11) | −0.0058 (11) | −0.0098 (11) |
N9 | 0.0298 (11) | 0.0363 (12) | 0.0306 (11) | −0.0010 (9) | −0.0052 (9) | −0.0082 (9) |
C9a | 0.0289 (13) | 0.0372 (14) | 0.0290 (12) | 0.0029 (10) | −0.0072 (10) | −0.0109 (11) |
N1—N2 | 1.366 (3) | C34—O34 | 1.365 (3) |
N2—C3 | 1.331 (3) | C34—C35 | 1.388 (4) |
C3—C3a | 1.436 (3) | O34—C341 | 1.416 (3) |
C3a—C4 | 1.394 (3) | C341—H34A | 0.98 |
C4—C4a | 1.384 (3) | C341—H34B | 0.98 |
C4a—C8a | 1.425 (3) | C341—H34C | 0.98 |
C4a—C5 | 1.485 (3) | C35—C36 | 1.374 (4) |
C5—C6 | 1.500 (3) | C35—H35 | 0.95 |
C6—C7 | 1.533 (4) | C36—H36 | 0.95 |
C7—C8 | 1.534 (3) | C4—H4 | 0.95 |
C8—C8a | 1.497 (3) | C5—O5 | 1.220 (3) |
C8a—N9 | 1.342 (3) | C6—H6B | 0.99 |
N9—C9a | 1.343 (3) | C6—H6A | 0.99 |
C9a—N1 | 1.352 (3) | C7—C71 | 1.526 (4) |
C3a—C9a | 1.412 (3) | C7—C72 | 1.527 (3) |
N1—H1 | 0.88 | C71—H71A | 0.98 |
C3—C31 | 1.467 (3) | C71—H71B | 0.98 |
C31—C32 | 1.389 (3) | C71—H71C | 0.98 |
C31—C36 | 1.392 (3) | C72—H72A | 0.98 |
C32—C33 | 1.388 (3) | C72—H72B | 0.98 |
C32—H32 | 0.95 | C72—H72C | 0.98 |
C33—C34 | 1.377 (3) | C8—H8A | 0.99 |
C33—H33 | 0.95 | C8—H8B | 0.99 |
C9a—N1—N2 | 111.21 (18) | O5—C5—C4a | 121.0 (2) |
C9a—N1—H1 | 124.4 | O5—C5—C6 | 122.0 (2) |
N2—N1—H1 | 124.4 | C4a—C5—C6 | 117.0 (2) |
C3—N2—N1 | 107.27 (18) | C5—C6—C7 | 113.4 (2) |
N2—C3—C3a | 109.9 (2) | C5—C6—H6B | 108.9 |
N2—C3—C31 | 119.4 (2) | C7—C6—H6B | 108.9 |
C3a—C3—C31 | 130.7 (2) | C5—C6—H6A | 108.9 |
C32—C31—C36 | 117.3 (2) | C7—C6—H6A | 108.9 |
C32—C31—C3 | 123.0 (2) | H6B—C6—H6A | 107.7 |
C36—C31—C3 | 119.7 (2) | C71—C7—C72 | 109.5 (2) |
C33—C32—C31 | 121.6 (2) | C71—C7—C6 | 110.2 (2) |
C33—C32—H32 | 119.2 | C72—C7—C6 | 109.8 (2) |
C31—C32—H32 | 119.2 | C71—C7—C8 | 110.5 (2) |
C34—C33—C32 | 119.9 (2) | C72—C7—C8 | 108.9 (2) |
C34—C33—H33 | 120.1 | C6—C7—C8 | 107.95 (19) |
C32—C33—H33 | 120.1 | C7—C71—H71A | 109.5 |
O34—C34—C33 | 125.0 (2) | C7—C71—H71B | 109.5 |
O34—C34—C35 | 115.6 (2) | H71A—C71—H71B | 109.5 |
C33—C34—C35 | 119.3 (2) | C7—C71—H71C | 109.5 |
C34—O34—C341 | 118.3 (2) | H71A—C71—H71C | 109.5 |
O34—C341—H34A | 109.5 | H71B—C71—H71C | 109.5 |
O34—C341—H34B | 109.5 | C7—C72—H72A | 109.5 |
H34A—C341—H34B | 109.5 | C7—C72—H72B | 109.5 |
O34—C341—H34C | 109.5 | H72A—C72—H72B | 109.5 |
H34A—C341—H34C | 109.5 | C7—C72—H72C | 109.5 |
H34B—C341—H34C | 109.5 | H72A—C72—H72C | 109.5 |
C36—C35—C34 | 120.3 (2) | H72B—C72—H72C | 109.5 |
C36—C35—H35 | 119.9 | N9—C8a—C4a | 122.2 (2) |
C34—C35—H35 | 119.9 | N9—C8a—C8 | 116.3 (2) |
C35—C36—C31 | 121.6 (2) | C4a—C8a—C8 | 121.5 (2) |
C35—C36—H36 | 119.2 | C8a—C8—C7 | 113.87 (19) |
C31—C36—H36 | 119.2 | C8a—C8—H8A | 108.8 |
C4—C3a—C9a | 116.0 (2) | C7—C8—H8A | 108.8 |
C4—C3a—C3 | 139.6 (2) | C8a—C8—H8B | 108.8 |
C9a—C3a—C3 | 104.36 (19) | C7—C8—H8B | 108.8 |
C4a—C4—C3a | 118.3 (2) | H8A—C8—H8B | 107.7 |
C4a—C4—H4 | 120.9 | C8a—N9—C9a | 115.04 (19) |
C3a—C4—H4 | 120.9 | N9—C9a—N1 | 125.1 (2) |
C4—C4a—C8a | 120.8 (2) | N9—C9a—C3a | 127.6 (2) |
C4—C4a—C5 | 119.4 (2) | N1—C9a—C3a | 107.2 (2) |
C8a—C4a—C5 | 119.8 (2) | ||
C9a—N1—N2—C3 | 0.1 (3) | C8a—C4a—C5—O5 | 178.1 (2) |
N1—N2—C3—C3a | −0.4 (2) | C4—C4a—C5—C6 | 176.0 (2) |
N1—N2—C3—C31 | 178.17 (19) | C8a—C4a—C5—C6 | −3.7 (3) |
N2—C3—C31—C32 | 166.7 (2) | O5—C5—C6—C7 | −145.8 (2) |
C3a—C3—C31—C32 | −15.1 (4) | C4a—C5—C6—C7 | 35.9 (3) |
N2—C3—C31—C36 | −11.7 (3) | C5—C6—C7—C71 | 62.4 (3) |
C3a—C3—C31—C36 | 166.5 (2) | C5—C6—C7—C72 | −176.9 (2) |
C36—C31—C32—C33 | −0.6 (4) | C5—C6—C7—C8 | −58.3 (3) |
C3—C31—C32—C33 | −179.1 (2) | C4—C4a—C8a—N9 | −3.2 (3) |
C31—C32—C33—C34 | −1.0 (4) | C5—C4a—C8a—N9 | 176.5 (2) |
C32—C33—C34—O34 | −178.0 (2) | C4—C4a—C8a—C8 | 176.3 (2) |
C32—C33—C34—C35 | 1.8 (4) | C5—C4a—C8a—C8 | −4.1 (3) |
C33—C34—O34—C341 | 3.5 (4) | N9—C8a—C8—C7 | 158.8 (2) |
C35—C34—O34—C341 | −176.3 (2) | C4a—C8a—C8—C7 | −20.7 (3) |
O34—C34—C35—C36 | 178.9 (2) | C71—C7—C8—C8a | −70.4 (3) |
C33—C34—C35—C36 | −1.0 (4) | C72—C7—C8—C8a | 169.2 (2) |
C34—C35—C36—C31 | −0.7 (4) | C6—C7—C8—C8a | 50.1 (3) |
C32—C31—C36—C35 | 1.5 (4) | C4a—C8a—N9—C9a | 1.6 (3) |
C3—C31—C36—C35 | 180.0 (2) | C8—C8a—N9—C9a | −177.88 (19) |
N2—C3—C3a—C4 | −179.1 (3) | C8a—N9—C9a—N1 | 178.6 (2) |
C31—C3—C3a—C4 | 2.5 (5) | C8a—N9—C9a—C3a | 1.6 (3) |
N2—C3—C3a—C9a | 0.5 (2) | N2—N1—C9a—N9 | −177.3 (2) |
C31—C3—C3a—C9a | −177.8 (2) | N2—N1—C9a—C3a | 0.2 (3) |
C9a—C3a—C4—C4a | 1.5 (3) | C4—C3a—C9a—N9 | −3.3 (3) |
C3—C3a—C4—C4a | −178.9 (3) | C3—C3a—C9a—N9 | 177.0 (2) |
C3a—C4—C4a—C8a | 1.4 (3) | C4—C3a—C9a—N1 | 179.33 (19) |
C3a—C4—C4a—C5 | −178.3 (2) | C3—C3a—C9a—N1 | −0.4 (2) |
C4—C4a—C5—O5 | −2.3 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···N9i | 0.88 | 2.01 | 2.884 (3) | 173 |
C8—H8B···Cgii | 0.99 | 2.80 | 3.772 (3) | 167 |
Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C19H19N3O2 |
Mr | 321.37 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 120 |
a, b, c (Å) | 7.1510 (6), 9.7680 (7), 12.3780 (8) |
α, β, γ (°) | 72.094 (5), 83.529 (4), 85.055 (4) |
V (Å3) | 816.28 (10) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.20 × 0.10 × 0.03 |
Data collection | |
Diffractometer | Bruker Nonius KappaCCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.977, 0.997 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17481, 3721, 2099 |
Rint | 0.108 |
(sin θ/λ)max (Å−1) | 0.650 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.074, 0.160, 1.03 |
No. of reflections | 3721 |
No. of parameters | 218 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.26, −0.18 |
Computer programs: COLLECT (Nonius, 1999), DENZO (Otwinowski & Minor, 1997) and COLLECT, DENZO and COLLECT, SIR2004 (Burla et al., 2005), OSCAIL (McArdle, 2003) and SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2003), SHELXL97 and PRPKAPPA (Ferguson, 1999).
N1—N2 | 1.366 (3) | C4a—C8a | 1.425 (3) |
N2—C3 | 1.331 (3) | C8a—N9 | 1.342 (3) |
C3—C3a | 1.436 (3) | N9—C9a | 1.343 (3) |
C3a—C4 | 1.394 (3) | C9a—N1 | 1.352 (3) |
C4—C4a | 1.384 (3) | C3a—C9a | 1.412 (3) |
O34—C34—C33 | 125.0 (2) | C34—O34—C341 | 118.3 (2) |
O34—C34—C35 | 115.6 (2) | ||
N2—C3—C31—C32 | 166.7 (2) | C33—C34—O34—C341 | 3.5 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···N9i | 0.88 | 2.01 | 2.884 (3) | 173 |
C8—H8B···Cgii | 0.99 | 2.80 | 3.772 (3) | 167 |
Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x+1, −y+1, −z+1. |
Acknowledgements
The X-ray data were collected by the EPSRC National X-ray Crystallography Service, University of Southampton, England; the authors thank the staff for all their help and advice. JC and JMT thank the Consejería de Innovación, Ciencia y Empresa (Junta de Andalucía, Spain), and the Universidad de Jaén for financial support. JMT also thanks Universidad de Jaén for a scholarship grant. JQ and SC thank COLCIENCIAS, UNIVALLE (Universidad del Valle, Colombia) and UDENAR (Universidad de Nariño, Colombia) for financial support.
References
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Pyrazolo[3,4-b]quinolines are of interest because of their pharmacological applications, e.g. as antiviral agents (Crenshaw et al., 1976; Smirnoff & Crenshaw, 1977). We have recently reported several efficient methods for the synthesis of compounds of this type, using the reactions between 5-aminopyrazoles, 5,5-dimethylcyclohexane-1,3-dione (dimedone) and substituted benzaldehydes, both in solution and under solvent-free conditions using microwave irradiation (Quiroga, Hormaza et al., 1998; Quiroga, Insuasty et al., 1998). Here, we report the molecular and supramolecular structure of the title compound, (I) (Fig. 1), synthesized using microwave irradiation in the absence of solvent. The structures of several analogous compounds have been reported recently, including those of (II), in both triclinic (Low et al., 2003) and monoclinic polymorphs (Mera et al., 2005), (III) (Low et al., 2004) and (IV) (Low et al., 2005), but in none of compounds (II)–(IV) is there an N—H bond at the pyrazole atom N1, as found in compound (I). Hence, the supramolecular aggregation in (I) is necessarily different from those found in (II)–(IV).
The bond lengths in (I) (Table 1) show clear evidence for electronic delocalization in the pyridine ring with significant bond fixation in the pyrazole ring. The methoxy atom C341 is almost coplanar with the adjacent aryl ring, while the exocyclic bond angles at C34 show the usual difference of ca 10°. The dihedral angle between the aryl and pyrazole rings is 13.4 (2)°. Within the non-aromatic carbocyclic ring, the ring-puckering parameters (Cremer & Pople, 1975) corresponding to the atom sequence C4a/C5–C8/C8a are θ = 55.1 (4)° and ϕ = 167.4 (4)°, indicating a conformation close to an envelope form, for which the idealized parameters are θ = 54.7° and ϕ = (60n)°. The ring is folded across the C6···C8 vector.
The molecules of (I) are linked into a chain of rings by a combination of N—H···N and C—H···π(arene) hydrogen bonds (Table 2). Pyrazole atom N1 in the molecule at (x, y, z) acts as hydrogen-bond donor to pyridine atom N9 in the molecule at (2 − x, 1 − y, 1 − z), so generating by inversion an R22(8) (Bernstein et al., 1995) ring centred at (1, 1/2, 1/2). In addition, atom C8 in the molecule at (x, y, z) acts as hydrogen-bond donor, via axial atom H8B, to the aryl ring C31–C36 in the molecule at (1 − x, 1 − y, 1 − z), so forming a second cyclic motif, this time centred at (1/2, 1/2, 1/2). Propagation by inversion of these two hydrogen bonds then generates a chain of rings running parallel to the [100] direction, with R22(8) rings centred at (n, 1/2, 1/2) (n = zero or integer) and rings generated by the C—H···π(arene) hydrogen bond centred at (n + 1/2, 1/2, 1/2) (n = zero or integer) (Fig. 2). The formation of this chain is reinforced by a π–π stacking interaction involving the pyridine rings of the molecules at (x, y, z) and (1 − x, 1 − y, 1 − z). These rings are strictly parallel, with an interplanar spacing of 3.310 (2) Å. The ring-centroid separation is 3.709 (2) Å, corresponding to a ring offset of 1.674 (2) Å. There are no direction-specific interactions between adjacent chains.
We briefly compare here the supramolecular aggregation in compound (I) with that found in each of compounds (II)–(IV). In the monoclinic polymorph of compound (II), which crystallizes with Z' = 1 in space group P21/n (Mera et al., 2005), two distinct C—H···π hydrogen bonds link the molecules into chains of rings, which are further linked into sheets by π–π stacking interactions. By contrast, in the triclinic polymorph of (II), which crystallizes with Z' = 2 in space group P1 (Low et al., 2003), each type of molecule forms a distinct chain built from a combination of C—H···O and C—H···π hydrogen bonds. In compound (III), the molecules are linked by a single C—H···N hydrogen bond to form simple C(6) chains (Low et al., 2004), while in compound (IV) the molecules are linked into isolated centrosymmetric dimers by two distinct C—H···π hydrogen bonds (Low et al., 2005). Thus no two members of this series show the same pattern of supramolecular aggregation, confirming that such aggregation is very sensitive to the details of the substituents on the heterocyclic ring system.