π-Stacked chains in 3,5-dimethyl-1,7-diphenyl-1,7-dihydro­dipyrazolo[3,4-b,4′,3′-e]pyridine

Portilla, J.; de la Torre, J.M.; Cobo, J.; Low, J.N.; Glidewell, C.

doi:10.1107/S1600536806011068

organic compounds

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ISSN: 2056-9890

Volume 62| Part 5| May 2006| Pages o1676-o1678

https://doi.org/10.1107/S1600536806011068

π-Stacked chains in 3,5-dimethyl-1,7-diphenyl-1,7-dihydrodipyrazolo[3,4-b,4′,3′-e]pyridine

Jaime Portilla,^a Jose M. de la Torre,^b Justo Cobo,^b John N. Low ^c and Christopher Glidewell ^d ^*

^aGrupo de Investigación de Compuestos Heterocíclicos, Departamento de Química, Universidad de Valle, A.A. 25360 Cali, Colombia, ^bDepartamento de Química Inorgánica y Orgánica, Universidad de Jaén, 23071 - Jaén, Spain, ^cDepartment of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen, AB24 3UE, Scotland, and ^dSchool of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, Scotland
^*Correspondence e-mail: cg@st-andrews.ac.uk

(Received 3 March 2006; accepted 27 March 2006; online 5 April 2006)

The title compound, C₂₁H₁₇N₅, was prepared using a microwave-induced condensation reaction between 5-amino-3-methyl-1-phenylpyrazole and formaldehyde. The molecules lie across twofold rotation axes in space group C2/c and are into chains by a π–π stacking interaction.

Comment

The title compound, (I), has been prepared using microwave irradiation in a solvent-free system and this provides an attractive alternative to the method recently reported (Abramos et al., 2001 ), not only in eliminating the solvent, but also in reducing the reaction time from hours to minutes while considerably improving the yield, from 37% to 65%. The simplicity of the present procedure and its selectivity also contrast with the previous method which required two distinct azoles, an aminopyrazole and 5-chloro-4-formylpyrazole, to generate the product.

The molecules of the title compound (I) (Fig. 1) lie across twofold rotation axes in space group C2/c: the reference molecule was selected as that lying across the axis along (½, y, ¼).

The bond distances (Table 1) within the pyridine ring are consistent with aromatic delocalization, but there is very strong bond fixation within the pyrazole rings (see scheme). The dihedral angle between the phenyl ring and the adjacent pyrazole ring is 27.4 (2)°.

A single π⋯π stacking interaction links the molecules into chains. The reference molecule, which lies across (½, y, ¼), is related by inversion to the adjacent molecules lying across the axes along (½, y, −¼) and (½, y, ¾); the heterocyclic systems in these three molecules are thus parallel with an interplanar spacing between adjacent rings of 3.363 (2) Å. The ring centroid separations between the pyridine ring of the reference molecule and the pyridine and pyrazole rings of an adjacent molecule are 3.772 (2) Å and 3.489 (2) Å, respectively. Propagation of this interaction by inversion thus generates a chain of π-stacked molecules along the [001] direction (Fig. 2). Two chains of this type, related to one another by the C-centring operation, pass through each unit cell, but there are no direction-specific interactions between adjacent chains: in particular C—H⋯N and C—H⋯π hydrogen bonds are absent from the structure of (I).

Figure 1
The molecular structure of compound (I)

, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level, and the atoms marked `a' are at the symmetry position (1 − x, y, $[{1\over 2}]$ − z).

Figure 2
A stereoview of part of the crystal structure of (I)

, showing the formation of a π-stacked chain along [001]. For the sake of clarity, H atoms have been omitted.

Experimental

Equimolar amounts of 5-amino-3-methyl-1-phenylpyrazole (1.0 mmol) and formaldehyde (1.0 mmol as 37% aqueous solution) were placed in open Pyrex vessels and irradiated in a domestic microwave oven for 1.5 min at 600 W. The reaction mixture was then extracted with ethanol. After the solvent had been removed under reduced pressure, the product was recrystallized from dimethylformamide to give crystals that were suitable for single-crystal X-ray diffraction. Yield 65%; m. p. 485–486 K, literature value 490–491 K (Abramos et al., 2001),

Crystal data

C₂₁H₁₇N₅
M_r = 339.40
Monoclinic, C 2/c
a = 21.2976 (4) Å
b = 10.9267 (3) Å
c = 7.4201 (2) Å
β = 98.108 (2)°
V = 1709.49 (7) Å³
Z = 4
D_x = 1.319 Mg m⁻³
Mo Kα radiation
Cell parameters from 1957 reflections
θ = 3.4–27.5°
μ = 0.08 mm⁻¹
T = 293 (2) K
Lath, colourless
0.60 × 0.18 × 0.12 mm

Data collection

Bruker–Nonius KappaCCD diffractometer
φ and ω scans
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ) T_min = 0.925, T_max = 0.990
14999 measured reflections
1957 independent reflections
1703 reflections with I > 2σ(I)
R_int = 0.027
θ_max = 27.5°
h = −27 → 27
k = −14 → 13
l = −8 → 9

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.042
wR(F²) = 0.116
S = 1.05
1957 reflections
120 parameters
H-atom parameters constrained
w = 1/[σ²(F_o²) + (0.0625P)² + 0.6017P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.17 e Å⁻³

Table 1
Selected bond lengths (Å)

N1—N2	1.3900 (12)
N2—C3	1.3111 (15)
C3—C3A	1.4320 (16)
C3A—C4	1.3860 (14)
N1—C8A	1.3686 (13)
C3A—C8A	1.4195 (15)
N8—C8A	1.3375 (12)
N8—C8A	1.3375 (12)

All H atoms were located in difference maps, and then treated as riding atoms with C—H distances 0.93 Å (aromatic) or 0.96 Å (methyl), and with U_iso(H) = 1.2U_eq(C), or 1.5U_eq(C) for the methyl group.

Data collection: COLLECT (Hooft, 1999 ); cell refinement: DENZO (Otwinowski & Minor, 1997 ) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SIR2004 (Burla et al., 2004 ) and WinGX (Farrugia, 1999 ); 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

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536806011068/wk2006sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536806011068/wk2006Isup2.hkl

Computing details top

Data collection: COLLECT (Hooft, 1999); cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: Sir2004 (Burla et al., 200) and WinGX (Farrugia, 1999); 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).

3,5-Dimethyl-1,7-diphenyl-1,7-dihydrodipyrazolo[3,4 - b,4',3'-e]pyridine top

Crystal data top

C₂₁H₁₇N₅	F(000) = 712
M_r = 339.40	D_x = 1.319 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1957 reflections
a = 21.2976 (4) Å	θ = 3.4–27.5°
b = 10.9267 (3) Å	µ = 0.08 mm⁻¹
c = 7.4201 (2) Å	T = 293 K
β = 98.108 (2)°	Lath, colourless
V = 1709.49 (7) Å³	0.60 × 0.18 × 0.12 mm
Z = 4

Data collection top

Bruker-Nonius KappaCCD diffractometer	1957 independent reflections
Radiation source: Bruker-Nonius FR591 rotating anode	1703 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.027
Detector resolution: 9.091 pixels mm^-1	θ_max = 27.5°, θ_min = 3.4°
φ and ω scans	h = −27→27
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	k = −14→13
T_min = 0.925, T_max = 0.990	l = −8→9
14999 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)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.116	H-atom parameters constrained
S = 1.05	w = 1/[σ²(F_o²) + (0.0625P)² + 0.6017P] where P = (F_o² + 2F_c²)/3
1957 reflections	(Δ/σ)_max < 0.001
120 parameters	Δρ_max = 0.21 e Å⁻³
0 restraints	Δρ_min = −0.17 e Å⁻³

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
N1	0.39729 (4)	0.63736 (8)	0.34529 (13)	0.0370 (2)
C11	0.37789 (5)	0.75836 (10)	0.37869 (14)	0.0369 (3)
C12	0.31364 (6)	0.78442 (12)	0.36680 (18)	0.0470 (3)
C13	0.29433 (7)	0.90036 (13)	0.4097 (2)	0.0571 (4)
C14	0.33815 (8)	0.99045 (14)	0.4626 (2)	0.0617 (4)
C15	0.40171 (8)	0.96455 (13)	0.4712 (2)	0.0613 (4)
C16	0.42225 (6)	0.84907 (12)	0.4299 (2)	0.0495 (3)
N2	0.35836 (5)	0.54010 (9)	0.37799 (14)	0.0411 (3)
C3	0.38888 (6)	0.43936 (11)	0.34922 (15)	0.0390 (3)
C31	0.36138 (7)	0.31626 (12)	0.37483 (18)	0.0512 (3)
C3A	0.44940 (5)	0.46605 (9)	0.29545 (14)	0.0354 (3)
C4	0.5000	0.39861 (14)	0.2500	0.0374 (4)
N8	0.5000	0.66527 (11)	0.2500	0.0346 (3)
C8A	0.45281 (5)	0.59578 (10)	0.29447 (14)	0.0331 (3)
H12	0.2837	0.7242	0.3301	0.056*
H13	0.2513	0.9176	0.4028	0.069*
H14	0.3249	1.0681	0.4923	0.074*
H15	0.4314	1.0257	0.5052	0.074*
H16	0.4654	0.8326	0.4366	0.059*
H31A	0.3220	0.3253	0.4222	0.077*
H31B	0.3904	0.2696	0.4588	0.077*
H31C	0.3541	0.2745	0.2599	0.077*
H4	0.5000	0.3135	0.2500	0.045*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0323 (5)	0.0356 (5)	0.0439 (5)	−0.0034 (4)	0.0084 (4)	0.0034 (4)
C11	0.0380 (6)	0.0375 (6)	0.0368 (5)	0.0002 (4)	0.0111 (4)	0.0030 (4)
C12	0.0375 (6)	0.0473 (7)	0.0581 (7)	0.0005 (5)	0.0132 (5)	0.0025 (6)
C13	0.0460 (7)	0.0534 (8)	0.0768 (9)	0.0099 (6)	0.0252 (6)	0.0048 (7)
C14	0.0665 (9)	0.0442 (7)	0.0815 (10)	0.0052 (7)	0.0348 (8)	−0.0039 (7)
C15	0.0593 (9)	0.0443 (8)	0.0847 (11)	−0.0094 (6)	0.0249 (8)	−0.0126 (7)
C16	0.0407 (6)	0.0452 (7)	0.0643 (8)	−0.0029 (5)	0.0135 (6)	−0.0053 (6)
N2	0.0375 (5)	0.0417 (6)	0.0445 (6)	−0.0093 (4)	0.0068 (4)	0.0035 (4)
C3	0.0401 (6)	0.0393 (6)	0.0361 (6)	−0.0083 (5)	0.0006 (4)	0.0030 (4)
C31	0.0571 (8)	0.0440 (7)	0.0523 (7)	−0.0161 (6)	0.0071 (6)	0.0012 (5)
C3A	0.0374 (6)	0.0340 (6)	0.0333 (5)	−0.0039 (4)	−0.0005 (4)	0.0014 (4)
C4	0.0442 (8)	0.0300 (7)	0.0359 (7)	0.000	−0.0019 (6)	0.000
N8	0.0310 (6)	0.0333 (6)	0.0397 (7)	0.000	0.0059 (5)	0.000
C8A	0.0314 (5)	0.0335 (5)	0.0335 (5)	−0.0006 (4)	0.0015 (4)	0.0015 (4)

Geometric parameters (Å, º) top

N1—N2	1.3900 (12)	C13—H13	0.93
N2—C3	1.3111 (15)	C14—C15	1.376 (2)
C3—C3A	1.4320 (16)	C14—H14	0.93
C3A—C4	1.3860 (14)	C15—C16	1.3838 (18)
N1—C8A	1.3686 (13)	C15—H15	0.93
C3A—C8A	1.4195 (15)	C16—H16	0.93
N8—C8A	1.3375 (12)	C3—C31	1.4899 (16)
N1—C11	1.4174 (14)	C31—H31A	0.96
C11—C16	1.3850 (16)	C31—H31B	0.96
C11—C12	1.3883 (16)	C31—H31C	0.96
C12—C13	1.3829 (19)	C4—H4	0.93
C12—H12	0.93	N8—C8A	1.3375 (12)
C13—C14	1.375 (2)

C8A—N1—N2	110.74 (9)	C3—N2—N1	106.97 (10)
C8A—N1—C11	129.96 (9)	N2—C3—C3A	111.14 (10)
N2—N1—C11	119.14 (9)	N2—C3—C31	121.63 (11)
C16—C11—C12	119.91 (11)	C3A—C3—C31	127.22 (11)
C16—C11—N1	120.75 (10)	C3—C31—H31A	109.5
C12—C11—N1	119.28 (10)	C3—C31—H31B	109.5
C13—C12—C11	119.72 (12)	H31A—C31—H31B	109.5
C13—C12—H12	120.1	C3—C31—H31C	109.5
C11—C12—H12	120.1	H31A—C31—H31C	109.5
C14—C13—C12	120.65 (13)	H31B—C31—H31C	109.5
C14—C13—H13	119.7	C4—C3A—C8A	119.18 (10)
C12—C13—H13	119.7	C4—C3A—C3	136.13 (11)
C13—C14—C15	119.32 (13)	C8A—C3A—C3	104.69 (10)
C13—C14—H14	120.3	C3Aⁱ—C4—C3A	115.75 (14)
C15—C14—H14	120.3	C3Aⁱ—C4—H4	122.1
C14—C15—C16	121.13 (14)	C3A—C4—H4	122.1
C14—C15—H15	119.4	C8Aⁱ—N8—C8A	110.82 (13)
C16—C15—H15	119.4	N8—C8A—N1	126.02 (10)
C15—C16—C11	119.25 (12)	N8—C8A—C3A	127.52 (10)
C15—C16—H16	120.4	N1—C8A—C3A	106.45 (9)
C11—C16—H16	120.4

C8A—N1—C11—C16	−24.88 (18)	N2—C3—C3A—C4	179.68 (10)
N2—N1—C11—C16	150.10 (11)	C31—C3—C3A—C4	0.6 (2)
C8A—N1—C11—C12	157.75 (11)	N2—C3—C3A—C8A	0.06 (12)
N2—N1—C11—C12	−27.28 (15)	C31—C3—C3A—C8A	−179.04 (11)
C16—C11—C12—C13	−1.26 (19)	C8A—C3A—C4—C3Aⁱ	−0.65 (6)
N1—C11—C12—C13	176.14 (12)	C3—C3A—C4—C3Aⁱ	179.77 (14)
C11—C12—C13—C14	0.6 (2)	C8Aⁱ—N8—C8A—N1	−179.48 (12)
C12—C13—C14—C15	0.5 (2)	C8Aⁱ—N8—C8A—C3A	−0.76 (7)
C13—C14—C15—C16	−0.9 (3)	N2—N1—C8A—N8	178.68 (8)
C14—C15—C16—C11	0.2 (2)	C11—N1—C8A—N8	−6.02 (17)
C12—C11—C16—C15	0.87 (19)	N2—N1—C8A—C3A	−0.26 (11)
N1—C11—C16—C15	−176.49 (12)	C11—N1—C8A—C3A	175.05 (10)
C8A—N1—N2—C3	0.30 (12)	C4—C3A—C8A—N8	1.51 (14)
C11—N1—N2—C3	−175.58 (9)	C3—C3A—C8A—N8	−178.79 (9)
N1—N2—C3—C3A	−0.21 (13)	C4—C3A—C8A—N1	−179.57 (8)
N1—N2—C3—C31	178.94 (10)	C3—C3A—C8A—N1	0.13 (11)

Symmetry code: (i) −x+1, y, −z+1/2.

Acknowledgements

X-ray data were collected at the EPSRC X-ray Crystallographic Service, University of Southampton, UK. JC and JT thank the Consejería de Innovación, Ciencia y Empresa (Junta de Andalucía, Spain) and the Universidad de Jaén for financial support. JT also thanks the Universidad de Jaén for a research scholarship supporting a short stay at the EPSRC X-ray Crystallographic Service, University of Southampton, UK. JP thanks COLCIENCIAS and UNIVALLE (Universidad del Valle, Colombia) for financial support.

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