In 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1
H-pyrazolo[3,4-
b]pyridine, C
19H
16BrN
3, the reduced pyridine ring adopts a conformation that is close to a screw-boat form. Molecules are linked by pairs of symmetry-related C—H
π(arene) hydrogen bonds into cyclic centrosymmetric dimers. Molecules of 3-(4-nitrophenyl)-4-phenyl-1
H-pyrazolo[3,4-
b]pyridine, C
18H
12N
4O
2, are linked into centrosymmetric
R22(8) dimers by pairs of symmetry-related N—H
N hydrogen bonds, and these dimers are linked by pairs of C—H
π(pyridine) hydrogen bonds to form a chain of edge-fused rings, or a molecular ladder, along [100]. The molecular aggregation in this compound is completed by two weak C—H
O hydrogen bonds, one of which links the chains along [100] into sheets.
Supporting information
CCDC references: 774892; 774893
For the synthesis of (I), a solution of 5-amino-1-phenyl-3-methylpyrazole (0.5
mmole and 1-(4-bromophenyl)-3-(dimethylamino)propan-1-one hydrochloride (0.5 mmol) in pyridine (2 ml) was heated under reflux for 20 min. The mixture was
cooled to ambient temperature and the product was isolated by filtration,
washed with ethanol and dried prior to purification by column chromatography
on silica gel using chloroform as eluant (yield 75%, m.p. 420-422 K). MS (70 eV) m/z (%) 365 (M+, 100), 364 (41), 183 (31), 143 (18),
102 (50), 77 (79), 51 (48); HR–MS found 365.0535, C19H16BrN3 requires
365.0528. Yellow crystals suitable for single-crystal X-ray diffraction were
obtained by slow evaporation, at ambient temperature and in air, of a solution
in dimethylformamide.
For the synthesis of (II), a solution of
5-amino-3-(4-nitrophenyl)-1H-pyrazole (1.9 mmol) and
3-dimethylaminopropiophenone (1.9 mmol) in pyridine (0.5 ml) was heated under
reflux for 20 min. The solution was cooled to ambient temperature and the
product mixture was collected by filtration, washed with ethanol and dried in
air. The two components were separated by column chromatography on alumina
using chloroform as the eluant. The main product was
2-(4-nitrophenyl)-6,7-dihydro-5-phenylpyrazolo[1,5-a]pyrimidine, (III),
isolated as a yellow solid (yield 80%, m.p. 552-544 K). HR–MS found 318.0959,
C18H14N4O2 requires 318.0960. Crystallization from
ethanol–dimethylformamide (1:1, v/v) of the impure column
fractions gave just a few crystals of compound (II) that proved to be suitable
for single-crystal X-ray diffraction.
All H atoms were located in difference maps and then treated as riding atoms in
geometrically idealized positions with C—H distances of 0.95 (aromatic or
pyridyl), 0.98 (CH3) or 0.99 Å (CH2) and N—H distances of 0.88 Å,
and with Uiso(H) = kUeq(carrier), where k = 1.5 for
the methyl group in (I), which was permitted to rotate but not to tilt, and
k = 1.2 for all other H atoms.
For both compounds, data collection: COLLECT (Hooft, 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: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).
(I) 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1
H-
pyrazolo[3,4-
b]pyridine
top
Crystal data top
C19H16BrN3 | F(000) = 744 |
Mr = 366.26 | Dx = 1.571 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 3058 reflections |
a = 7.5165 (1) Å | θ = 3.2–26.1° |
b = 11.6572 (3) Å | µ = 2.66 mm−1 |
c = 17.6917 (5) Å | T = 120 K |
β = 92.701 (2)° | Needle, yellow |
V = 1548.45 (6) Å3 | 0.20 × 0.06 × 0.04 mm |
Z = 4 | |
Data collection top
Bruker–Nonius KappaCCD diffractometer | 3058 independent reflections |
Radiation source: Bruker-Nonius FR591 rotating anode | 2597 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.048 |
Detector resolution: 9.091 pixels mm-1 | θmax = 26.1°, θmin = 3.2° |
ϕ & ω scans | h = −8→9 |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | k = −14→14 |
Tmin = 0.685, Tmax = 0.901 | l = −21→21 |
21038 measured reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.029 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.069 | H-atom parameters constrained |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0284P)2 + 1.0784P] where P = (Fo2 + 2Fc2)/3 |
3058 reflections | (Δ/σ)max = 0.001 |
209 parameters | Δρmax = 0.26 e Å−3 |
0 restraints | Δρmin = −0.51 e Å−3 |
Crystal data top
C19H16BrN3 | V = 1548.45 (6) Å3 |
Mr = 366.26 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 7.5165 (1) Å | µ = 2.66 mm−1 |
b = 11.6572 (3) Å | T = 120 K |
c = 17.6917 (5) Å | 0.20 × 0.06 × 0.04 mm |
β = 92.701 (2)° | |
Data collection top
Bruker–Nonius KappaCCD diffractometer | 3058 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 2597 reflections with I > 2σ(I) |
Tmin = 0.685, Tmax = 0.901 | Rint = 0.048 |
21038 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.029 | 0 restraints |
wR(F2) = 0.069 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.26 e Å−3 |
3058 reflections | Δρmin = −0.51 e Å−3 |
209 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
N1 | 0.1491 (2) | 0.57039 (14) | 0.57944 (10) | 0.0166 (4) | |
N2 | 0.0955 (2) | 0.68300 (15) | 0.58020 (10) | 0.0192 (4) | |
C3 | 0.1460 (3) | 0.72732 (18) | 0.51492 (12) | 0.0196 (4) | |
C3A | 0.2321 (3) | 0.64486 (18) | 0.47129 (11) | 0.0168 (4) | |
C4 | 0.3286 (3) | 0.64703 (19) | 0.39950 (12) | 0.0222 (5) | |
H4A | 0.4481 | 0.6812 | 0.4090 | 0.027* | |
H4B | 0.2622 | 0.6950 | 0.3616 | 0.027* | |
C5 | 0.3472 (3) | 0.52481 (18) | 0.36877 (12) | 0.0193 (4) | |
H5A | 0.2469 | 0.5105 | 0.3317 | 0.023* | |
H5B | 0.4584 | 0.5208 | 0.3411 | 0.023* | |
C6 | 0.3506 (3) | 0.42890 (18) | 0.42673 (11) | 0.0159 (4) | |
N7 | 0.2959 (2) | 0.43926 (14) | 0.49501 (10) | 0.0161 (4) | |
C7A | 0.2298 (3) | 0.54648 (17) | 0.51320 (11) | 0.0158 (4) | |
C11 | 0.1298 (3) | 0.50223 (18) | 0.64513 (11) | 0.0170 (4) | |
C12 | 0.1356 (3) | 0.38296 (19) | 0.64202 (12) | 0.0196 (5) | |
H12 | 0.1541 | 0.3451 | 0.5955 | 0.024* | |
C13 | 0.1142 (3) | 0.3197 (2) | 0.70750 (12) | 0.0237 (5) | |
H13 | 0.1199 | 0.2384 | 0.7054 | 0.028* | |
C14 | 0.0847 (3) | 0.3729 (2) | 0.77579 (12) | 0.0242 (5) | |
H14 | 0.0680 | 0.3289 | 0.8201 | 0.029* | |
C15 | 0.0802 (3) | 0.4915 (2) | 0.77804 (13) | 0.0265 (5) | |
H15 | 0.0607 | 0.5290 | 0.8246 | 0.032* | |
C16 | 0.1036 (3) | 0.55689 (19) | 0.71364 (12) | 0.0231 (5) | |
H16 | 0.1018 | 0.6383 | 0.7163 | 0.028* | |
C31 | 0.1059 (3) | 0.85022 (19) | 0.49562 (14) | 0.0265 (5) | |
H31A | 0.0034 | 0.8538 | 0.4594 | 0.040* | |
H31B | 0.2097 | 0.8851 | 0.4732 | 0.040* | |
H31C | 0.0785 | 0.8920 | 0.5417 | 0.040* | |
C61 | 0.4087 (3) | 0.31249 (18) | 0.40482 (11) | 0.0162 (4) | |
C62 | 0.5062 (3) | 0.29113 (19) | 0.34087 (11) | 0.0195 (4) | |
H62 | 0.5354 | 0.3529 | 0.3087 | 0.023* | |
C63 | 0.5609 (3) | 0.18080 (19) | 0.32385 (12) | 0.0219 (5) | |
H63 | 0.6292 | 0.1672 | 0.2809 | 0.026* | |
C64 | 0.5154 (3) | 0.09143 (19) | 0.36966 (12) | 0.0202 (5) | |
Br64 | 0.59123 (3) | −0.060800 (19) | 0.348270 (13) | 0.02834 (9) | |
C65 | 0.4155 (3) | 0.10903 (19) | 0.43266 (12) | 0.0210 (5) | |
H65 | 0.3832 | 0.0463 | 0.4634 | 0.025* | |
C66 | 0.3639 (3) | 0.21905 (19) | 0.44977 (12) | 0.0206 (5) | |
H66 | 0.2964 | 0.2318 | 0.4931 | 0.025* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0184 (9) | 0.0155 (9) | 0.0158 (9) | 0.0010 (7) | 0.0017 (7) | −0.0015 (7) |
N2 | 0.0222 (9) | 0.0141 (9) | 0.0211 (9) | 0.0013 (7) | −0.0006 (7) | −0.0017 (7) |
C3 | 0.0205 (11) | 0.0169 (11) | 0.0211 (11) | −0.0005 (8) | −0.0033 (8) | 0.0002 (9) |
C3A | 0.0174 (10) | 0.0160 (11) | 0.0168 (10) | −0.0006 (8) | −0.0005 (8) | 0.0007 (8) |
C4 | 0.0278 (12) | 0.0203 (12) | 0.0184 (11) | 0.0018 (9) | 0.0016 (9) | 0.0039 (9) |
C5 | 0.0226 (11) | 0.0203 (11) | 0.0149 (10) | −0.0003 (8) | 0.0017 (8) | 0.0026 (9) |
C6 | 0.0136 (10) | 0.0187 (11) | 0.0152 (10) | −0.0028 (8) | −0.0005 (8) | 0.0000 (8) |
N7 | 0.0167 (9) | 0.0161 (9) | 0.0157 (9) | −0.0011 (7) | 0.0022 (7) | −0.0012 (7) |
C7A | 0.0146 (10) | 0.0187 (11) | 0.0139 (10) | −0.0014 (8) | 0.0002 (8) | −0.0019 (8) |
C11 | 0.0145 (10) | 0.0205 (12) | 0.0161 (10) | −0.0007 (8) | 0.0021 (8) | 0.0003 (8) |
C12 | 0.0218 (11) | 0.0200 (12) | 0.0176 (11) | −0.0007 (8) | 0.0053 (8) | −0.0031 (9) |
C13 | 0.0268 (12) | 0.0184 (12) | 0.0264 (12) | 0.0015 (9) | 0.0058 (9) | 0.0030 (9) |
C14 | 0.0254 (12) | 0.0295 (13) | 0.0179 (11) | −0.0015 (9) | 0.0035 (9) | 0.0049 (9) |
C15 | 0.0319 (13) | 0.0307 (14) | 0.0174 (12) | −0.0011 (10) | 0.0059 (9) | −0.0047 (10) |
C16 | 0.0276 (12) | 0.0208 (12) | 0.0211 (12) | −0.0003 (9) | 0.0034 (9) | −0.0038 (9) |
C31 | 0.0312 (12) | 0.0166 (12) | 0.0315 (13) | 0.0032 (9) | −0.0008 (10) | 0.0028 (10) |
C61 | 0.0158 (10) | 0.0184 (11) | 0.0145 (10) | −0.0024 (8) | −0.0004 (8) | −0.0021 (8) |
C62 | 0.0221 (11) | 0.0208 (12) | 0.0156 (11) | −0.0026 (8) | 0.0015 (8) | 0.0006 (9) |
C63 | 0.0249 (11) | 0.0241 (12) | 0.0170 (10) | −0.0001 (9) | 0.0051 (9) | −0.0023 (9) |
C64 | 0.0246 (11) | 0.0191 (11) | 0.0167 (11) | 0.0008 (8) | −0.0018 (9) | −0.0039 (9) |
Br64 | 0.04297 (16) | 0.01933 (14) | 0.02316 (14) | 0.00488 (10) | 0.00611 (10) | −0.00395 (9) |
C65 | 0.0273 (12) | 0.0169 (11) | 0.0188 (11) | −0.0043 (9) | 0.0027 (9) | 0.0018 (9) |
C66 | 0.0224 (11) | 0.0231 (12) | 0.0169 (11) | −0.0014 (9) | 0.0061 (8) | −0.0008 (9) |
Geometric parameters (Å, º) top
N1—C7A | 1.373 (3) | C13—C14 | 1.385 (3) |
N1—N2 | 1.373 (2) | C13—H13 | 0.9500 |
N1—C11 | 1.421 (3) | C14—C15 | 1.384 (3) |
N2—C3 | 1.336 (3) | C14—H14 | 0.9500 |
C3—C3A | 1.409 (3) | C15—C16 | 1.389 (3) |
C3—C31 | 1.500 (3) | C15—H15 | 0.9500 |
C3A—C7A | 1.366 (3) | C16—H16 | 0.9500 |
C3A—C4 | 1.492 (3) | C31—H31A | 0.9800 |
C4—C5 | 1.534 (3) | C31—H31B | 0.9800 |
C4—H4A | 0.9900 | C31—H31C | 0.9800 |
C4—H4B | 0.9900 | C61—C66 | 1.399 (3) |
C5—C6 | 1.516 (3) | C61—C62 | 1.399 (3) |
C5—H5A | 0.9900 | C62—C63 | 1.388 (3) |
C5—H5B | 0.9900 | C62—H62 | 0.9500 |
C6—N7 | 1.300 (3) | C63—C64 | 1.373 (3) |
C6—C61 | 1.483 (3) | C63—H63 | 0.9500 |
N7—C7A | 1.388 (3) | C64—C65 | 1.388 (3) |
C11—C16 | 1.391 (3) | C64—Br64 | 1.907 (2) |
C11—C12 | 1.392 (3) | C65—C66 | 1.378 (3) |
C12—C13 | 1.389 (3) | C65—H65 | 0.9500 |
C12—H12 | 0.9500 | C66—H66 | 0.9500 |
| | | |
C7A—N1—N2 | 110.12 (16) | C14—C13—H13 | 119.3 |
C7A—N1—C11 | 130.61 (17) | C12—C13—H13 | 119.3 |
N2—N1—C11 | 119.01 (16) | C15—C14—C13 | 118.5 (2) |
C3—N2—N1 | 105.40 (17) | C15—C14—H14 | 120.7 |
N2—C3—C3A | 111.48 (18) | C13—C14—H14 | 120.7 |
N2—C3—C31 | 120.25 (19) | C14—C15—C16 | 121.4 (2) |
C3A—C3—C31 | 128.3 (2) | C14—C15—H15 | 119.3 |
C7A—C3A—C3 | 104.93 (18) | C16—C15—H15 | 119.3 |
C7A—C3A—C4 | 119.68 (19) | C15—C16—C11 | 119.5 (2) |
C3—C3A—C4 | 135.1 (2) | C15—C16—H16 | 120.3 |
C3A—C4—C5 | 110.00 (18) | C11—C16—H16 | 120.3 |
C3A—C4—H4A | 109.7 | C3—C31—H31A | 109.5 |
C5—C4—H4A | 109.7 | C3—C31—H31B | 109.5 |
C3A—C4—H4B | 109.7 | H31A—C31—H31B | 109.5 |
C5—C4—H4B | 109.7 | C3—C31—H31C | 109.5 |
H4A—C4—H4B | 108.2 | H31A—C31—H31C | 109.5 |
C6—C5—C4 | 116.37 (17) | H31B—C31—H31C | 109.5 |
C6—C5—H5A | 108.2 | C66—C61—C62 | 118.06 (19) |
C4—C5—H5A | 108.2 | C66—C61—C6 | 118.82 (18) |
C6—C5—H5B | 108.2 | C62—C61—C6 | 123.12 (19) |
C4—C5—H5B | 108.2 | C63—C62—C61 | 120.8 (2) |
H5A—C5—H5B | 107.3 | C63—C62—H62 | 119.6 |
N7—C6—C61 | 115.98 (18) | C61—C62—H62 | 119.6 |
N7—C6—C5 | 124.32 (19) | C64—C63—C62 | 119.39 (19) |
C61—C6—C5 | 119.59 (17) | C64—C63—H63 | 120.3 |
C6—N7—C7A | 115.56 (17) | C62—C63—H63 | 120.3 |
C3A—C7A—N1 | 108.06 (18) | C63—C64—C65 | 121.4 (2) |
C3A—C7A—N7 | 128.04 (18) | C63—C64—Br64 | 120.25 (16) |
N1—C7A—N7 | 123.90 (18) | C65—C64—Br64 | 118.34 (16) |
C16—C11—C12 | 119.86 (19) | C66—C65—C64 | 118.8 (2) |
C16—C11—N1 | 118.72 (19) | C66—C65—H65 | 120.6 |
C12—C11—N1 | 121.43 (18) | C64—C65—H65 | 120.6 |
C13—C12—C11 | 119.5 (2) | C65—C66—C61 | 121.47 (19) |
C13—C12—H12 | 120.3 | C65—C66—H66 | 119.3 |
C11—C12—H12 | 120.3 | C61—C66—H66 | 119.3 |
C14—C13—C12 | 121.3 (2) | | |
| | | |
C7A—N1—N2—C3 | −0.8 (2) | N2—N1—C11—C16 | −17.2 (3) |
C11—N1—N2—C3 | 173.92 (17) | C7A—N1—C11—C12 | −24.0 (3) |
N1—N2—C3—C3A | 0.1 (2) | N2—N1—C11—C12 | 162.54 (18) |
N1—N2—C3—C31 | 178.99 (18) | C16—C11—C12—C13 | 0.4 (3) |
N2—C3—C3A—C7A | 0.7 (2) | N1—C11—C12—C13 | −179.33 (19) |
C31—C3—C3A—C7A | −178.1 (2) | C11—C12—C13—C14 | 0.9 (3) |
N2—C3—C3A—C4 | −173.2 (2) | C12—C13—C14—C15 | −1.2 (3) |
C31—C3—C3A—C4 | 8.0 (4) | C13—C14—C15—C16 | 0.3 (3) |
C7A—C3A—C4—C5 | 22.7 (3) | C14—C15—C16—C11 | 0.9 (3) |
C3—C3A—C4—C5 | −164.1 (2) | C12—C11—C16—C15 | −1.2 (3) |
C3A—C4—C5—C6 | −27.5 (3) | N1—C11—C16—C15 | 178.50 (19) |
C4—C5—C6—N7 | 17.9 (3) | N7—C6—C61—C66 | 14.6 (3) |
C4—C5—C6—C61 | −166.16 (18) | C5—C6—C61—C66 | −161.72 (19) |
C61—C6—N7—C7A | −175.57 (17) | N7—C6—C61—C62 | −165.64 (19) |
C5—C6—N7—C7A | 0.5 (3) | C5—C6—C61—C62 | 18.1 (3) |
C3—C3A—C7A—N1 | −1.2 (2) | C66—C61—C62—C63 | −1.7 (3) |
C4—C3A—C7A—N1 | 173.88 (18) | C6—C61—C62—C63 | 178.49 (19) |
C3—C3A—C7A—N7 | 179.06 (19) | C61—C62—C63—C64 | 1.3 (3) |
C4—C3A—C7A—N7 | −5.9 (3) | C62—C63—C64—C65 | 0.1 (3) |
N2—N1—C7A—C3A | 1.3 (2) | C62—C63—C64—Br64 | −179.25 (16) |
C11—N1—C7A—C3A | −172.66 (19) | C63—C64—C65—C66 | −1.0 (3) |
N2—N1—C7A—N7 | −178.93 (17) | Br64—C64—C65—C66 | 178.34 (16) |
C11—N1—C7A—N7 | 7.1 (3) | C64—C65—C66—C61 | 0.6 (3) |
C6—N7—C7A—C3A | −7.3 (3) | C62—C61—C66—C65 | 0.8 (3) |
C6—N7—C7A—N1 | 172.91 (19) | C6—C61—C66—C65 | −179.42 (19) |
C7A—N1—C11—C16 | 156.3 (2) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C5—H5A···Cg1i | 0.99 | 2.80 | 3.662 (2) | 146 |
Symmetry code: (i) −x, −y+1, −z+1. |
(II) 3-(4-nitrophenyl)-4-phenyl-1
H-pyrazolo[3,4-
b]pyridine
top
Crystal data top
C18H12N4O2 | Z = 2 |
Mr = 316.32 | F(000) = 328 |
Triclinic, P1 | Dx = 1.406 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.0408 (1) Å | Cell parameters from 2938 reflections |
b = 9.6360 (3) Å | θ = 3.5–26.1° |
c = 11.1961 (3) Å | µ = 0.10 mm−1 |
α = 84.906 (1)° | T = 120 K |
β = 89.177 (2)° | Plate, yellow |
γ = 81.012 (2)° | 0.24 × 0.20 × 0.06 mm |
V = 747.31 (3) Å3 | |
Data collection top
Bruker–Nonius KappaCCD diffractometer | 2938 independent reflections |
Radiation source: Bruker-Nonius FR591 rotating anode | 2447 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.038 |
Detector resolution: 9.091 pixels mm-1 | θmax = 26.1°, θmin = 3.5° |
ϕ & ω scans | h = −8→8 |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | k = −11→11 |
Tmin = 0.974, Tmax = 0.994 | l = −13→13 |
13461 measured reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.038 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.101 | H-atom parameters constrained |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0487P)2 + 0.2645P] where P = (Fo2 + 2Fc2)/3 |
2938 reflections | (Δ/σ)max = 0.001 |
217 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.34 e Å−3 |
Crystal data top
C18H12N4O2 | γ = 81.012 (2)° |
Mr = 316.32 | V = 747.31 (3) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.0408 (1) Å | Mo Kα radiation |
b = 9.6360 (3) Å | µ = 0.10 mm−1 |
c = 11.1961 (3) Å | T = 120 K |
α = 84.906 (1)° | 0.24 × 0.20 × 0.06 mm |
β = 89.177 (2)° | |
Data collection top
Bruker–Nonius KappaCCD diffractometer | 2938 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 2447 reflections with I > 2σ(I) |
Tmin = 0.974, Tmax = 0.994 | Rint = 0.038 |
13461 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.038 | 0 restraints |
wR(F2) = 0.101 | H-atom parameters constrained |
S = 1.06 | Δρmax = 0.20 e Å−3 |
2938 reflections | Δρmin = −0.34 e Å−3 |
217 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
N1 | 0.14822 (16) | 0.02507 (12) | 0.86334 (10) | 0.0174 (3) | |
H1 | 0.0523 | −0.0214 | 0.8820 | 0.021* | |
N2 | 0.23027 (16) | 0.03444 (12) | 0.75281 (10) | 0.0177 (3) | |
C3 | 0.37039 (18) | 0.11149 (14) | 0.76011 (12) | 0.0152 (3) | |
C3A | 0.37809 (18) | 0.15793 (14) | 0.87802 (12) | 0.0149 (3) | |
C4 | 0.47665 (18) | 0.24722 (14) | 0.93931 (12) | 0.0155 (3) | |
C5 | 0.42734 (19) | 0.25808 (15) | 1.05886 (12) | 0.0189 (3) | |
H5 | 0.4920 | 0.3143 | 1.1051 | 0.023* | |
C6 | 0.28394 (19) | 0.18771 (15) | 1.11298 (13) | 0.0190 (3) | |
H6 | 0.2575 | 0.1979 | 1.1955 | 0.023* | |
N7 | 0.18203 (16) | 0.10750 (12) | 1.05670 (10) | 0.0173 (3) | |
C7A | 0.23280 (18) | 0.09634 (14) | 0.94114 (12) | 0.0152 (3) | |
C31 | 0.49462 (19) | 0.13361 (14) | 0.65465 (12) | 0.0148 (3) | |
C32 | 0.41393 (19) | 0.17295 (15) | 0.54097 (12) | 0.0181 (3) | |
H32 | 0.2788 | 0.1815 | 0.5305 | 0.022* | |
C33 | 0.53012 (19) | 0.19956 (15) | 0.44359 (12) | 0.0183 (3) | |
H33 | 0.4761 | 0.2267 | 0.3662 | 0.022* | |
C34 | 0.72658 (19) | 0.18583 (14) | 0.46111 (12) | 0.0155 (3) | |
C35 | 0.81192 (19) | 0.14082 (14) | 0.57121 (12) | 0.0163 (3) | |
H35 | 0.9477 | 0.1274 | 0.5801 | 0.020* | |
C36 | 0.69376 (19) | 0.11592 (14) | 0.66806 (12) | 0.0166 (3) | |
H36 | 0.7491 | 0.0864 | 0.7448 | 0.020* | |
N34 | 0.84861 (16) | 0.22220 (12) | 0.35935 (10) | 0.0180 (3) | |
O1 | 0.77058 (15) | 0.28314 (11) | 0.26739 (9) | 0.0258 (3) | |
O2 | 1.02401 (14) | 0.19188 (12) | 0.37097 (9) | 0.0260 (3) | |
C41 | 0.61947 (19) | 0.32961 (14) | 0.88097 (12) | 0.0170 (3) | |
C42 | 0.5819 (2) | 0.40547 (15) | 0.76971 (13) | 0.0213 (3) | |
H42 | 0.4614 | 0.4081 | 0.7318 | 0.026* | |
C43 | 0.7203 (2) | 0.47722 (16) | 0.71405 (15) | 0.0294 (4) | |
H43 | 0.6944 | 0.5280 | 0.6379 | 0.035* | |
C44 | 0.8960 (2) | 0.47499 (16) | 0.76927 (16) | 0.0321 (4) | |
H44 | 0.9912 | 0.5226 | 0.7304 | 0.039* | |
C45 | 0.9319 (2) | 0.40323 (16) | 0.88105 (15) | 0.0287 (4) | |
H45 | 1.0513 | 0.4031 | 0.9196 | 0.034* | |
C46 | 0.7945 (2) | 0.33129 (15) | 0.93734 (14) | 0.0214 (3) | |
H46 | 0.8198 | 0.2830 | 1.0145 | 0.026* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0156 (6) | 0.0238 (6) | 0.0151 (6) | −0.0096 (5) | 0.0038 (4) | −0.0038 (5) |
N2 | 0.0167 (6) | 0.0226 (6) | 0.0151 (6) | −0.0067 (5) | 0.0033 (4) | −0.0028 (5) |
C3 | 0.0132 (6) | 0.0174 (7) | 0.0151 (7) | −0.0033 (5) | 0.0000 (5) | −0.0010 (5) |
C3A | 0.0129 (6) | 0.0168 (7) | 0.0146 (7) | −0.0015 (5) | 0.0009 (5) | −0.0006 (5) |
C4 | 0.0132 (6) | 0.0165 (7) | 0.0165 (7) | −0.0018 (5) | −0.0001 (5) | −0.0018 (5) |
C5 | 0.0180 (7) | 0.0234 (7) | 0.0169 (7) | −0.0070 (6) | −0.0004 (5) | −0.0043 (6) |
C6 | 0.0180 (7) | 0.0259 (8) | 0.0140 (7) | −0.0052 (6) | 0.0011 (5) | −0.0032 (6) |
N7 | 0.0167 (6) | 0.0216 (6) | 0.0144 (6) | −0.0053 (5) | 0.0019 (4) | −0.0020 (5) |
C7A | 0.0129 (6) | 0.0174 (7) | 0.0153 (7) | −0.0029 (5) | 0.0008 (5) | −0.0014 (5) |
C31 | 0.0158 (7) | 0.0149 (7) | 0.0147 (7) | −0.0047 (5) | 0.0026 (5) | −0.0038 (5) |
C32 | 0.0134 (7) | 0.0245 (7) | 0.0174 (7) | −0.0053 (5) | 0.0001 (5) | −0.0039 (6) |
C33 | 0.0195 (7) | 0.0219 (7) | 0.0136 (7) | −0.0038 (5) | −0.0022 (5) | −0.0007 (6) |
C34 | 0.0171 (7) | 0.0161 (7) | 0.0141 (7) | −0.0048 (5) | 0.0044 (5) | −0.0021 (5) |
C35 | 0.0121 (7) | 0.0193 (7) | 0.0179 (7) | −0.0029 (5) | 0.0006 (5) | −0.0025 (5) |
C36 | 0.0177 (7) | 0.0189 (7) | 0.0132 (7) | −0.0032 (5) | −0.0009 (5) | −0.0005 (5) |
N34 | 0.0193 (6) | 0.0206 (6) | 0.0154 (6) | −0.0066 (5) | 0.0026 (5) | −0.0022 (5) |
O1 | 0.0282 (6) | 0.0332 (6) | 0.0161 (5) | −0.0090 (4) | −0.0007 (4) | 0.0056 (4) |
O2 | 0.0166 (5) | 0.0381 (6) | 0.0231 (6) | −0.0058 (4) | 0.0049 (4) | 0.0005 (5) |
C41 | 0.0172 (7) | 0.0156 (7) | 0.0195 (7) | −0.0043 (5) | 0.0041 (5) | −0.0050 (5) |
C42 | 0.0250 (8) | 0.0175 (7) | 0.0220 (8) | −0.0043 (6) | 0.0018 (6) | −0.0032 (6) |
C43 | 0.0429 (10) | 0.0174 (8) | 0.0273 (9) | −0.0050 (6) | 0.0100 (7) | 0.0009 (6) |
C44 | 0.0299 (9) | 0.0218 (8) | 0.0469 (11) | −0.0111 (7) | 0.0179 (7) | −0.0053 (7) |
C45 | 0.0186 (8) | 0.0251 (8) | 0.0447 (10) | −0.0083 (6) | 0.0044 (7) | −0.0072 (7) |
C46 | 0.0188 (7) | 0.0208 (7) | 0.0258 (8) | −0.0052 (6) | 0.0012 (6) | −0.0043 (6) |
Geometric parameters (Å, º) top
N1—C7A | 1.3543 (17) | C33—H33 | 0.9500 |
N1—N2 | 1.3599 (15) | C34—C35 | 1.3833 (19) |
N1—H1 | 0.8800 | C34—N34 | 1.4677 (17) |
N2—C3 | 1.3316 (17) | C35—C36 | 1.3841 (19) |
C3—C3A | 1.4354 (19) | C35—H35 | 0.9500 |
C3—C31 | 1.4794 (18) | C36—H36 | 0.9500 |
C3A—C7A | 1.4116 (18) | N34—O2 | 1.2299 (15) |
C3A—C4 | 1.4135 (19) | N34—O1 | 1.2308 (15) |
C4—C5 | 1.3868 (19) | C41—C42 | 1.394 (2) |
C4—C41 | 1.4854 (18) | C41—C46 | 1.396 (2) |
C5—C6 | 1.4034 (19) | C42—C43 | 1.390 (2) |
C5—H5 | 0.9500 | C42—H42 | 0.9500 |
C6—N7 | 1.3350 (18) | C43—C44 | 1.387 (2) |
C6—H6 | 0.9500 | C43—H43 | 0.9500 |
N7—C7A | 1.3463 (17) | C44—C45 | 1.382 (2) |
C31—C36 | 1.3944 (19) | C44—H44 | 0.9500 |
C31—C32 | 1.3980 (19) | C45—C46 | 1.389 (2) |
C32—C33 | 1.3835 (19) | C45—H45 | 0.9500 |
C32—H32 | 0.9500 | C46—H46 | 0.9500 |
C33—C34 | 1.3840 (19) | | |
| | | |
C7A—N1—N2 | 111.45 (11) | C34—C33—H33 | 120.6 |
C7A—N1—H1 | 124.3 | C35—C34—C33 | 122.49 (12) |
N2—N1—H1 | 124.3 | C35—C34—N34 | 118.79 (12) |
C3—N2—N1 | 106.65 (11) | C33—C34—N34 | 118.71 (12) |
N2—C3—C3A | 110.78 (11) | C34—C35—C36 | 118.09 (12) |
N2—C3—C31 | 119.39 (12) | C34—C35—H35 | 121.0 |
C3A—C3—C31 | 129.80 (12) | C36—C35—H35 | 121.0 |
C7A—C3A—C4 | 117.54 (12) | C35—C36—C31 | 120.95 (12) |
C7A—C3A—C3 | 103.56 (11) | C35—C36—H36 | 119.5 |
C4—C3A—C3 | 138.78 (12) | C31—C36—H36 | 119.5 |
C5—C4—C3A | 115.72 (12) | O2—N34—O1 | 123.32 (11) |
C5—C4—C41 | 120.84 (12) | O2—N34—C34 | 118.23 (11) |
C3A—C4—C41 | 123.40 (12) | O1—N34—C34 | 118.44 (11) |
C4—C5—C6 | 121.39 (13) | C42—C41—C46 | 119.07 (13) |
C4—C5—H5 | 119.3 | C42—C41—C4 | 120.93 (12) |
C6—C5—H5 | 119.3 | C46—C41—C4 | 120.00 (13) |
N7—C6—C5 | 124.60 (13) | C43—C42—C41 | 120.22 (14) |
N7—C6—H6 | 117.7 | C43—C42—H42 | 119.9 |
C5—C6—H6 | 117.7 | C41—C42—H42 | 119.9 |
C6—N7—C7A | 113.47 (11) | C44—C43—C42 | 120.27 (15) |
N7—C7A—N1 | 125.29 (12) | C44—C43—H43 | 119.9 |
N7—C7A—C3A | 127.17 (12) | C42—C43—H43 | 119.9 |
N1—C7A—C3A | 107.52 (11) | C45—C44—C43 | 119.77 (14) |
C36—C31—C32 | 119.39 (12) | C45—C44—H44 | 120.1 |
C36—C31—C3 | 120.12 (12) | C43—C44—H44 | 120.1 |
C32—C31—C3 | 120.49 (12) | C44—C45—C46 | 120.34 (15) |
C33—C32—C31 | 120.24 (13) | C44—C45—H45 | 119.8 |
C33—C32—H32 | 119.9 | C46—C45—H45 | 119.8 |
C31—C32—H32 | 119.9 | C45—C46—C41 | 120.29 (14) |
C32—C33—C34 | 118.73 (13) | C45—C46—H46 | 119.9 |
C32—C33—H33 | 120.6 | C41—C46—H46 | 119.9 |
| | | |
C7A—N1—N2—C3 | 0.60 (15) | C36—C31—C32—C33 | −2.6 (2) |
N1—N2—C3—C3A | −1.66 (15) | C3—C31—C32—C33 | 177.14 (12) |
N1—N2—C3—C31 | 176.51 (11) | C31—C32—C33—C34 | 0.3 (2) |
N2—C3—C3A—C7A | 2.04 (15) | C32—C33—C34—C35 | 2.8 (2) |
C31—C3—C3A—C7A | −175.88 (13) | C32—C33—C34—N34 | −176.39 (12) |
N2—C3—C3A—C4 | −173.67 (15) | C33—C34—C35—C36 | −3.4 (2) |
C31—C3—C3A—C4 | 8.4 (3) | N34—C34—C35—C36 | 175.78 (12) |
C7A—C3A—C4—C5 | 3.82 (18) | C34—C35—C36—C31 | 1.0 (2) |
C3—C3A—C4—C5 | 179.11 (15) | C32—C31—C36—C35 | 1.9 (2) |
C7A—C3A—C4—C41 | −174.04 (12) | C3—C31—C36—C35 | −177.77 (12) |
C3—C3A—C4—C41 | 1.2 (2) | C35—C34—N34—O2 | 10.49 (18) |
C3A—C4—C5—C6 | −1.97 (19) | C33—C34—N34—O2 | −170.30 (12) |
C41—C4—C5—C6 | 175.95 (12) | C35—C34—N34—O1 | −168.53 (12) |
C4—C5—C6—N7 | −0.9 (2) | C33—C34—N34—O1 | 10.69 (18) |
C5—C6—N7—C7A | 1.6 (2) | C5—C4—C41—C42 | −132.24 (14) |
C6—N7—C7A—N1 | −177.81 (13) | C3A—C4—C41—C42 | 45.51 (19) |
C6—N7—C7A—C3A | 0.6 (2) | C5—C4—C41—C46 | 48.04 (19) |
N2—N1—C7A—N7 | 179.36 (12) | C3A—C4—C41—C46 | −134.20 (14) |
N2—N1—C7A—C3A | 0.70 (15) | C46—C41—C42—C43 | 2.4 (2) |
C4—C3A—C7A—N7 | −3.4 (2) | C4—C41—C42—C43 | −177.32 (13) |
C3—C3A—C7A—N7 | 179.78 (13) | C41—C42—C43—C44 | −0.6 (2) |
C4—C3A—C7A—N1 | 175.21 (11) | C42—C43—C44—C45 | −1.2 (2) |
C3—C3A—C7A—N1 | −1.59 (14) | C43—C44—C45—C46 | 1.2 (2) |
N2—C3—C31—C36 | −133.34 (14) | C44—C45—C46—C41 | 0.6 (2) |
C3A—C3—C31—C36 | 44.4 (2) | C42—C41—C46—C45 | −2.4 (2) |
N2—C3—C31—C32 | 46.95 (18) | C4—C41—C46—C45 | 177.30 (13) |
C3A—C3—C31—C32 | −135.29 (15) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···N7i | 0.88 | 2.04 | 2.916 (2) | 171 |
C6—H6···O2ii | 0.95 | 2.55 | 3.397 (2) | 149 |
C32—H32···O2iii | 0.95 | 2.53 | 3.335 (2) | 142 |
C45—H45···Cg2iv | 0.95 | 2.79 | 3.472 (2) | 129 |
Symmetry codes: (i) −x, −y, −z+2; (ii) x−1, y, z+1; (iii) x−1, y, z; (iv) x+1, y, z. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | C19H16BrN3 | C18H12N4O2 |
Mr | 366.26 | 316.32 |
Crystal system, space group | Monoclinic, P21/c | Triclinic, P1 |
Temperature (K) | 120 | 120 |
a, b, c (Å) | 7.5165 (1), 11.6572 (3), 17.6917 (5) | 7.0408 (1), 9.6360 (3), 11.1961 (3) |
α, β, γ (°) | 90, 92.701 (2), 90 | 84.906 (1), 89.177 (2), 81.012 (2) |
V (Å3) | 1548.45 (6) | 747.31 (3) |
Z | 4 | 2 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 2.66 | 0.10 |
Crystal size (mm) | 0.20 × 0.06 × 0.04 | 0.24 × 0.20 × 0.06 |
|
Data collection |
Diffractometer | Bruker–Nonius KappaCCD diffractometer | Bruker–Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.685, 0.901 | 0.974, 0.994 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 21038, 3058, 2597 | 13461, 2938, 2447 |
Rint | 0.048 | 0.038 |
(sin θ/λ)max (Å−1) | 0.618 | 0.618 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.069, 1.05 | 0.038, 0.101, 1.06 |
No. of reflections | 3058 | 2938 |
No. of parameters | 209 | 217 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.26, −0.51 | 0.20, −0.34 |
Selected geometric parameters (Å, °) for compounds
(I) and (II) topParameter | (I) | (II) |
N1—N2 | 1.373 (2) | 1.3599 (15) |
N2—C3 | 1.336 (3) | 1.3316 (17) |
C3—C3A | 1.409 (3) | 1.4354 (19) |
C3A—C4 | 1.492 (3) | 1.4135 (19) |
C4—C5 | 1.534 (3) | 1.3868 (19) |
C5—C6 | 1.516 (3) | 1.4034 (19) |
C6—N7 | 1.300 (3) | 1.3350 (18) |
N7—C7A | 1.388 (3) | 1.3463 (17) |
C7A—N1 | 1.373 (3) | 1.3543 (17) |
C3A—C7A | 1.366 (2) | 1.4116 (18) |
| | |
N2—N1—C11—C12 | 162.54 (18) | |
N2—C3—C31—C32 | | 46.95 (18) |
N7—C6—C61—C62 | -165.64 (19) | |
C3A—C4—C41—C42 | | 45.51 (19) |
C33—C34—N34—O1 | | 10.69 (18) |
Hydrogen bonds and short intermolecular contacts (Å, °)
for compounds (I) and (II) topCompound | D—H···A | D—H | H···A | D···A | D—H···A |
(I) | C5—H5A···Cg1a,i | 0.99 | 2.80 | 3.662 (2) | 146 |
| | | | | |
(II) | N1—H1···N7ii | 0.88 | 2.04 | 2.916 (2) | 171 |
| C6—H6···O2iii | 0.95 | 2.55 | 3.397 (2) | 149 |
| C32—H32···O2iv | 0.95 | 2.53 | 3.335 (2) | 142 |
| C45—H45···Cg2b,v | 0.95 | 2.79 | 3.472 (2) | 129 |
Cg1 and Cg2 represent the centroids of the C11–C16
and C3A/C4/C5/C6/N7/C7A rings, respectively.
Symmetry codes: (i) -x, -y+1, -z+1; (ii) -x, -y, -z+2;
(iii) x-1, y, z+1; (iv) x-1, y, z; (v) x+1, y, z. |
4,5-Dihydropyrazolo[3,4-b]pyridines and their derivatives are useful synthetic intermediates as position 5 is active in, for example, Vilsmeier formylation reactions. The analogous 6,7-dihydropyrazolo[1,5-a]pyrimidines, which are purine analogues, are of potential pharmacological value (Novinson et al., 1976; Senga et al., 1981). Here we report the molecular and supramolecular structures of two pyrazolo[3,4-b]pyridine derivatives, namely 6-(4-bromophenyl)-4,5-dihydro-3-methyl-1-phenyl-1H- pyrazolo[3,4-b]pyridine, (I), and 3-(4-nitrophenyl)-4-phenyl-1H-pyrazolo[3,4-b]pyridine, (II) (Figs. 1 and 2), each of which was obtained from a cyclization reaction between a substituted 5-aminopyrazole and a 3-(dimethylamino)propiophenone derivative, but involving different regiochemistry in the two cases.
The synthesis of compound (I) involved a cyclization reaction between 5-amino-3-methyl-1-phenylpyrazole and a bromo-substituted 3-(dimethylamino)propiophenone hydrochloride to give the product (I) in 75% yield (see scheme). In this cyclization, the amino group of the pyrazole component reacts with the carbonyl group of the propiophenone component, while atom C4 of the pyrazole reacts at position 3 of the propiophenone. By contrast, in the corresponding reaction between 5-amino-3-(4-nitrophenyl)-1H-pyrazole and neutral 3-(dimethylamino)propiophenone, the formation of compound (II) involves the opposite regiochemistry, with atom C4 of the pyrazole reacting with the carbonyl group and the amino group of the pyrazole attacking at position 3 of the propiophenone. Compound (II) was, in fact, formed as a very minor product, and the major product of this reaction resulted from a cyclization utilising both the NH2 and the NH functions of the pyrazole component to yield 2-(4-nitrophenyl)-6,7-dihydro-5-phenylpyrazolo[1,5-a]pyrimidine, (III), in 80% yield (see scheme). Compounds (I) and (II) thus differ in several respects: the oxidation level of the six-membered heterocyclic ring; the location of the aryl substituent in this ring; and the presence in (II), but not in (I), of an NH group available for hydrogen-bond formation. However, because of the very similar processes by which they are formed, differing primarily in the regiochemistry of the reaction rather than in the reactants themselves, it is appropriate to consider them at the same time. Compounds (IV) and (V) (see scheme) are close analogues of compounds (I) and (II), respectively whose structures have been published, and these two compounds are discussed following the discussion of compounds (I) and (II).
Within the molecule of compound (I), the reduced pyridine ring is nonplanar with ring-puckering angles (Cremer & Pople, 1975) θ = 62.0 (5)° and ϕ = 161.7 (6)°; these values indicate a ring conformation that is close to the screw-boat form, where the idealized ring-puckering angles are θ = 67.5° and ϕ = (60k + 30)° (k represents an integer). The rest of the molecular conformation in (I) can be defined in terms of just two torsion angles (Table 1). The molecular conformation of compound (II) can be defined in terms of three torsion angles (Table 1) or, alternatively, in terms of three interplanar angles. The substituted and unsubstituted aryl rings in (II) make dihedral angles with their neighbouring heterocyclic rings of 46.1 (2) and 46.4 (2)°, respectively, while the nitro group makes a dihedral angle of 11.3 (2)° with the adjacent phenyl ring. The molecules of compounds (I) and (II) thus have no internal symmetry, and so they are conformationally chiral; however, the centrosymmetric space groups accommodate equal numbers of the two conformational enantiomers in each case. The bond distances in the fused heterocyclic systems (Table 1) are consistent with a modest degree of electronic delocalization in the pyrazole ring of (I) and with a delocalized pyridine system in (II).
The supramolecular aggregation is very simple in (I) and more complex in (II). In (I), pairs of molecules related by inversion are linked by pairs of symmetry-related C—H···π(arene) hydrogen bonds (Table 2) to form a cyclic centrosymmetric dimers (Fig. 3), but there are no significant direction-specific interactions between the dimers.
The molecules of compound (II) are linked into a chain of edge-fused rings, or a molecular ladder, by a combination of N—H···N and C—H···π(pyridine) hydrogen bonds (Table 2). Pairs of molecules related by inversion are linked by pairs of symmetry-related, nearly linear N—H···N hydrogen bonds to form cyclic dimers characterised by an R22(8) (Bernstein et al., 1995) motif (Fig. 4). In addition, the phenyl atom C45 in the molecule at (x, y, z) acts as hydrogen-bond donor to the pyridine ring of the molecule at (x + 1, y, z), so linking cyclic dimers into a chain of edge-fused rings running parallel to the [100] direction. In this chain, the centosymmetric R22(8) rings are centred at (n, 0, 1), where n represents an integer. These alternate with the larger centrosymmetric rings formed by the C—H···π(pyridine) hydrogen bonds and centred at (n + 1/2, 0, 1), where n again represents an integer (Fig. 4).
Within this chain of rings, pairs of pyrazolopyridine rings related by inversion across (n + 1/2, 0, 1) have an interplanar spacing of 3.663 (2) Å between the pyridine rings, whose ring-centroid separation is 3.827 (2) Å, corresponding to a ring-centroid offset of 1.106 (2)°. The interplanar spacing and the ring-centroid separation are both quite large, and it is possible that this contact is an adventitious consequence of the hydrogen bonding, rather than being of structural significance in itself. Nonetheless, any attractive interaction associated with this contact will reinforce, albeit weakly, the formation of the chain of rings parallel to [100].
There are also two short intermolecular C—H···O contacts in the crystal structure of (II), both involving the nitro atom O2 (Table 2). One of these contacts, involving atom C32, is between molecules related by translation along the [100] direction so that, if this contact is regarded as a weak hydrogen bond, its role is to reinforce the chain along [100]. The second contact, involving atom C6, is between molecules related by translation along [101]; if this contact is regarded as a weak hydrogen bond, then its role is to link the chains along [100] into a sheet parallel to (010).
The structure of the 4-chlorophenyl analogue of (I), compound (IV) (see scheme) was reported some years ago on a proof of constitution basis, without discussion [Cambridge Structural Database (CSD; Allen, 2002) refcode LABDAT (Quiroga et al., 1998)]. It is clear from the unit-cell dimensions for (IV) [a = 8.113 (1) Å, b = 17.315 (1) Å, c = 11.789 (1) Å, β = 104.77 (1)° in space group P21/n (incorrectly reported as P21/c)] that compounds (I) and (IV) are by no means isomorphous, as might possibly have been expected. However, since no H-atom coordinates for (IV) have been deposited, very little can be deduced about any supramolecular aggregation in the structure of (IV). Somewhat similar to compound (II), and obtained in a somewhat similar way, is compound (V), which was also reported on a proof of constitution basis without discussion (CSD refcode DEZQII; Quiroga et al., 1999), although this appears to be the only previously reported example of a 1H-pyrazolo[3,4-b]pyridine carrying two aryl substituents at the 3- and 4-positions. Examination of the crystal structure of (V) using the deposited atomic coordinates shows the presence of two hydrogen bonds, one each of N—H···N and C—H···N types, where the acceptors are, respectively, the pyridine ring N atom and the nitrile N atom. Inversion-related pairs of molecules are linked by pairs of N—H···N hydrogen bonds to form centrosymmetric R22(8) dimers, just as in (II). However, in (V) these dimers are linked by the C—H···N hydrogen bond to form a sheet lying parallel to (101) and built from centrosymmetric R22(8) and centrosymmetric R66(44) rings arranged in a chessboard fashion (Fig. 5). Unlike the structure of (II), that of (V) contains no C—H···π(arene) hydrogen bonds.