2,2′-(Propane-1,3-di­yl)bis­(2H-indazole)

Ovalle, S.; Bernès, S.; Pérez Rodríguez, N.; Elizondo Martínez, P.

doi:10.1107/S1600536811029011

organic compounds

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ISSN: 2056-9890

Volume 67| Part 8| August 2011| Page o2144

doi:10.1107/S1600536811029011

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2,2′-(Propane-1,3-diyl)bis(2H-indazole)

Saúl Ovalle,^a Sylvain Bernès,^b Nancy Pérez Rodríguez ^a and Perla Elizondo Martínez ^a ^*

^aLaboratorio de Química Industrial, Centro de Laboratorios Especializados, Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, Pedro de Alba S/N, 66451 San Nicolás de los Garza, NL, Mexico, and ^bDivisión de Estudios de Posgrado, Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, Guerrero y Progreso S/N, Col. Treviño, 64570 Monterrey, NL, Mexico
^*Correspondence e-mail: sylvain_bernes@hotmail.com

(Received 14 June 2011; accepted 18 July 2011; online 30 July 2011)

The title molecule, C₁₇H₁₆N₄, is a bis-indazole crystallized in the rare 2H-tautomeric form. Indazole heterocycles are connected by a propane C₃ chain, and the molecule is placed on a general position, in contrast to the analogous compound with a central C₂ ethane bridge, which was previously found to be placed on an inversion center in the same space group. In the title molecule, indazole rings make a dihedral angle of 60.11 (7)°, and the bridging alkyl chain displays a trans conformation, resulting in a W-shaped molecule. In the crystal, molecules interact weakly through π–π contacts between inversion-related pyrazole rings, with a centroid–centroid separation of 3.746 (2) Å.

Related literature

For the synthesis of 2H-indazoles, see: Wu et al. (2010 ). For studies of 1H←→2H tautomerism in indazoles, see: Alkorta & Elguero (2005 ); Yu et al. (2006 ). For 2H-indazole X-ray structures, see: Saczewski et al. (2001 ); Rodríguez de Barbarín et al. (2006 ); Ramos Silva et al. (2008 ); Hurtado et al. (2009 ); Zhou et al. (2010 ); Long et al. (2011 ).

Experimental

Crystal data

C₁₇H₁₆N₄
M_r = 276.34
Orthorhombic, P b c a
a = 8.182 (2) Å
b = 10.549 (4) Å
c = 34.179 (9) Å
V = 2950.1 (16) Å³
Z = 8
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 298 K
0.60 × 0.40 × 0.18 mm

Data collection

Siemens P4 diffractometer
8195 measured reflections
2621 independent reflections
1607 reflections with I > 2σ(I)
R_int = 0.042
3 standard reflections every 97 reflections intensity decay: 1.5%

Refinement

R[F² > 2σ(F²)] = 0.049
wR(F²) = 0.162
S = 1.10
2621 reflections
191 parameters
H-atom parameters constrained
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.21 e Å⁻³

Data collection: XSCANS (Siemens, 1996 ); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811029011/aa2015sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811029011/aa2015Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811029011/aa2015Isup3.mol

Supporting information file. DOI: 10.1107/S1600536811029011/aa2015Isup4.cml

checkCIF report

Comment top

Although efficient synthetic routes for 2H-indazoles are available (e.g. Wu et al., 2010) few molecules belonging to this family of heterocyclic compounds have been X-ray characterized up to now. This is due, in part, to the fact that 1H tautomer for indazoles is frequently more stable than the 2H tautomer, although the opposite situation may occur for some derivatives (Alkorta & Elguero, 2005; Yu et al., 2006). On the other hand, in the case of N2-substituted indazoles, only the 2H tautomer is allowed. Tautomerism equilibrium study is important, since bioavailability and other pharmacological properties of indazoles may be dependent on such equilibria (e.g. Ramos Silva et al., 2008). Indazole derivatives have been used, for instance, for their anti-inflammatory activity.

The title compound was prepared through a three steps procedure, the key step being the cyclization of a nitroamine derivative (compound P, see Fig. 1 and Experimental). The resulting bis-indazole consists of two 2H-indazole heterocycles connected by an alkyl C₃ bridge (Fig. 2). The molecule lies in a general position, in space group Pbca. It is worth noting that the analogue compound with a central C₂ bridge, for which we reported the X-ray structure (Rodríguez de Barbarín et al., 2006), was found to crystallize in the same space group, although the molecule was placed on an inversion center. From this pair of structures now determined, we can propose the following general rule for n-alkyl bridged bis(2H-indazoles): even-alkyl compounds should be centrosymmetric, while odd-alkyl derivatives are expected to be non-centrosymmetric, as the title compound.

Molecular dimensions observed in the title compound compare well with those reported for other 2H-indazoles (Saczewski et al., 2001; Rodríguez de Barbarín et al., 2006; Hurtado et al., 2009; Zhou et al., 2010; Long et al., 2011). Indazole rings make a dihedral angle of 60.11 (7)°. Torsion angles N2—C8—C9—C10 and C8—C9—C10—N12, -176.7 (2) and 173.5 (2)° respectively, characterize the trans conformation for the alkyl bridge, resulting in a W-shaped molecule. The crystal structure features π–π interactions of modest strength, between molecules related by inversion (Fig. 3). The separation between the centroid of the pyrazole ring N11/N12/C11/C17/C16 and the symmetry-related centroid at position -x, 1 - y, 1 - z, is 3.746 (2) Å.

Related literature top

For the synthesis of 2H-indazoles, see: Wu et al. (2010). For studies of 1H←→2H tautomerism in indazoles, see: Alkorta & Elguero (2005); Yu et al. (2006). For 2H-indazole X-ray structures, see: Saczewski et al. (2001); Rodríguez de Barbarín et al. (2006); Ramos Silva et al. (2008); Hurtado et al. (2009); Zhou et al. (2010); Long et al. (2011).

Experimental top

The title ligand, PI, was obtained by a three steps reaction procedure (Fig. 1). The condensation between 1,3-diaminopropane and 2-nitrobenzaldehyde produced the corresponding imine. Selective reduction of imine bonds with sodium borohydride in methanol gave amine P, which was isolated. Then, 0.044 g of Pd/C was added to a solution of P (0.005 mol) in ethanol. This mixture was refluxed for 5.5 h, with addition of hydrazine monohydrate (0.110 mol) during the first 3 h. The mixture was filtered, distilled, and the organic phase was extracted. The product was purified by column chromatography with silica gel and ethyl acetate:hexane (2:1) as eluent. Suitable crystals were obtained by slow evaporation of an ethanol solution at 298 K. Mp 389.4–390 K; analysis found (calc. for C₁₇H₁₆N₄): C 73.6 (73.9), H 5.8 (5.8), N 20.5% (20.3%); IR RTA: 3108 (CH Ar. ν_s), 2950 (–CH₂– ν_s), 1625 (C=N Ar. δ_s), 1514, 1467 (C=C Ar. ν_s and ν_as). ¹H NMR (300 MHz, CDCl₃): δ, p.p.m.: 2.73 (2H, m, –CH₂–), 4.41 (4H, t, N—CH₂), 7.10 (2H, dd, Ar), 7.31 (2H, dd, Ar), 7.66 (2H, dd, Ar), 7.73 (2H, td, Ar), 7.95 (2H, s, NH).

Computing details top

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS (Siemens, 1996); data reduction: XSCANS (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. Synthetic route for the title compound. P is the key intermediate and PI is the title compound.
	Fig. 2. ORTEP-like view of the title molecule, with displacement ellipsoids at the 30% probability level for non-H atoms.
	Fig. 3. A part of the crystal structure representing two molecules related by inversion, which interact through a π–π contact involving pyrazole rings (dashed line).

2,2'-(Propane-1,3-diyl)bis(2H-indazole) top

Crystal data top

C₁₇H₁₆N₄	D_x = 1.244 Mg m⁻³
M_r = 276.34	Melting point: 389 K
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 77 reflections
a = 8.182 (2) Å	θ = 4.6–12.4°
b = 10.549 (4) Å	µ = 0.08 mm⁻¹
c = 34.179 (9) Å	T = 298 K
V = 2950.1 (16) Å³	Prism, yellow
Z = 8	0.60 × 0.40 × 0.18 mm
F(000) = 1168

Data collection top

Siemens P4 diffractometer	R_int = 0.042
Radiation source: fine-focus sealed tube	θ_max = 25.1°, θ_min = 2.4°
Graphite monochromator	h = −9→8
ω scans	k = −12→12
8195 measured reflections	l = −40→40
2621 independent reflections	3 standard reflections every 97 reflections
1607 reflections with I > 2σ(I)	intensity decay: 1.5%

Refinement top

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)] = 0.049	H-atom parameters constrained
wR(F²) = 0.162	w = 1/[σ²(F_o²) + (0.0659P)² + 0.9616P] where P = (F_o² + 2F_c²)/3
S = 1.10	(Δ/σ)_max < 0.001
2621 reflections	Δρ_max = 0.20 e Å⁻³
191 parameters	Δρ_min = −0.21 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 constraints	Extinction coefficient: 0.0159 (17)
Primary atom site location: structure-invariant direct methods

Crystal data top

C₁₇H₁₆N₄	V = 2950.1 (16) Å³
M_r = 276.34	Z = 8
Orthorhombic, Pbca	Mo Kα radiation
a = 8.182 (2) Å	µ = 0.08 mm⁻¹
b = 10.549 (4) Å	T = 298 K
c = 34.179 (9) Å	0.60 × 0.40 × 0.18 mm

Data collection top

Siemens P4 diffractometer	R_int = 0.042
8195 measured reflections	3 standard reflections every 97 reflections
2621 independent reflections	intensity decay: 1.5%
1607 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.049	0 restraints
wR(F²) = 0.162	H-atom parameters constrained
S = 1.10	Δρ_max = 0.20 e Å⁻³
2621 reflections	Δρ_min = −0.21 e Å⁻³
191 parameters

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

	x	y	z	U_iso*/U_eq
N1	0.3628 (3)	0.67210 (17)	0.33910 (5)	0.0640 (6)
N2	0.2422 (2)	0.75293 (17)	0.34924 (5)	0.0563 (5)
C1	0.2608 (3)	0.8690 (2)	0.33476 (6)	0.0622 (7)
H1A	0.1914	0.9378	0.3385	0.075*
C2	0.4896 (4)	0.9559 (3)	0.29004 (7)	0.0773 (8)
H2A	0.4529	1.0390	0.2876	0.093*
C3	0.6261 (5)	0.9172 (3)	0.27178 (8)	0.0902 (10)
H3A	0.6828	0.9744	0.2561	0.108*
C4	0.6856 (4)	0.7935 (4)	0.27562 (9)	0.0986 (11)
H4A	0.7815	0.7708	0.2628	0.118*
C5	0.6062 (4)	0.7056 (3)	0.29769 (8)	0.0847 (9)
H5A	0.6463	0.6235	0.3002	0.102*
C6	0.4614 (3)	0.7431 (2)	0.31655 (6)	0.0610 (7)
C7	0.4032 (3)	0.8675 (2)	0.31308 (6)	0.0604 (7)
C8	0.1158 (3)	0.7097 (2)	0.37586 (6)	0.0639 (7)
H8A	0.0822	0.6247	0.3686	0.077*
H8B	0.0214	0.7649	0.3737	0.077*
C9	0.1757 (3)	0.7094 (2)	0.41760 (7)	0.0646 (7)
H9A	0.2737	0.6582	0.4195	0.078*
H9B	0.2031	0.7952	0.4254	0.078*
C10	0.0474 (3)	0.6575 (3)	0.44453 (6)	0.0671 (7)
H10B	−0.0458	0.7143	0.4447	0.080*
H10C	0.0109	0.5760	0.4348	0.080*
N11	0.2399 (2)	0.56892 (18)	0.49101 (5)	0.0611 (6)
N12	0.1075 (2)	0.64232 (18)	0.48438 (5)	0.0571 (5)
C11	0.0399 (3)	0.6887 (2)	0.51674 (7)	0.0615 (7)
H11B	−0.0516	0.7409	0.5181	0.074*
C12	0.1239 (4)	0.6545 (2)	0.58912 (7)	0.0696 (7)
H12B	0.0444	0.7040	0.6012	0.083*
C13	0.2351 (3)	0.5902 (3)	0.61062 (7)	0.0699 (7)
H13B	0.2306	0.5947	0.6378	0.084*
C14	0.3567 (3)	0.5170 (2)	0.59287 (8)	0.0707 (7)
H14C	0.4308	0.4737	0.6086	0.085*
C15	0.3702 (3)	0.5070 (2)	0.55328 (7)	0.0683 (7)
H15B	0.4538	0.4603	0.5418	0.082*
C16	0.2530 (3)	0.5701 (2)	0.53037 (6)	0.0533 (6)
C17	0.1312 (3)	0.6448 (2)	0.54797 (7)	0.0555 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0772 (15)	0.0555 (11)	0.0593 (11)	0.0036 (11)	0.0102 (11)	0.0011 (9)
N2	0.0647 (13)	0.0543 (10)	0.0499 (10)	0.0009 (10)	0.0040 (10)	0.0007 (8)
C1	0.0780 (18)	0.0525 (13)	0.0560 (13)	0.0050 (12)	−0.0062 (14)	0.0031 (10)
C2	0.107 (2)	0.0695 (16)	0.0558 (14)	−0.0202 (17)	−0.0037 (16)	0.0056 (12)
C3	0.113 (3)	0.095 (2)	0.0633 (17)	−0.036 (2)	0.0138 (18)	0.0004 (15)
C4	0.100 (3)	0.118 (3)	0.0780 (19)	−0.011 (2)	0.0320 (18)	−0.0046 (19)
C5	0.095 (2)	0.0832 (19)	0.0754 (17)	0.0069 (18)	0.0252 (17)	−0.0047 (15)
C6	0.0760 (17)	0.0596 (14)	0.0474 (12)	−0.0041 (13)	0.0039 (12)	−0.0038 (10)
C7	0.0796 (18)	0.0570 (13)	0.0447 (12)	−0.0064 (13)	−0.0031 (12)	0.0003 (10)
C8	0.0633 (16)	0.0713 (15)	0.0572 (13)	−0.0018 (13)	0.0053 (12)	0.0041 (11)
C9	0.0662 (17)	0.0707 (15)	0.0570 (13)	−0.0090 (13)	0.0045 (12)	0.0051 (12)
C10	0.0665 (17)	0.0764 (16)	0.0583 (14)	−0.0086 (14)	0.0020 (13)	0.0044 (12)
N11	0.0601 (13)	0.0607 (12)	0.0626 (11)	0.0070 (10)	0.0088 (10)	0.0013 (9)
N12	0.0542 (12)	0.0595 (11)	0.0576 (11)	0.0007 (10)	0.0071 (10)	0.0047 (9)
C11	0.0608 (16)	0.0610 (14)	0.0628 (15)	0.0081 (12)	0.0103 (12)	0.0004 (11)
C12	0.0737 (18)	0.0719 (16)	0.0631 (15)	0.0076 (15)	0.0085 (14)	−0.0050 (12)
C13	0.0792 (19)	0.0731 (16)	0.0574 (13)	0.0005 (16)	−0.0023 (14)	0.0011 (12)
C14	0.0732 (19)	0.0667 (15)	0.0724 (16)	0.0059 (14)	−0.0063 (14)	0.0087 (13)
C15	0.0687 (17)	0.0639 (14)	0.0724 (16)	0.0098 (13)	0.0054 (14)	0.0012 (12)
C16	0.0535 (14)	0.0470 (11)	0.0593 (13)	−0.0014 (11)	0.0061 (11)	0.0023 (10)
C17	0.0570 (15)	0.0505 (12)	0.0590 (13)	0.0018 (11)	0.0072 (12)	0.0015 (10)

Geometric parameters (Å, º) top

N1—C6	1.343 (3)	C9—H9A	0.9700
N1—N2	1.350 (3)	C9—H9B	0.9700
N2—C1	1.329 (3)	C10—N12	1.457 (3)
N2—C8	1.451 (3)	C10—H10B	0.9700
C1—C7	1.381 (4)	C10—H10C	0.9700
C1—H1A	0.9300	N11—C16	1.350 (3)
C2—C3	1.343 (4)	N11—N12	1.351 (3)
C2—C7	1.410 (3)	N12—C11	1.330 (3)
C2—H2A	0.9300	C11—C17	1.383 (3)
C3—C4	1.400 (5)	C11—H11B	0.9300
C3—H3A	0.9300	C12—C13	1.353 (4)
C4—C5	1.360 (4)	C12—C17	1.411 (3)
C4—H4A	0.9300	C12—H12B	0.9300
C5—C6	1.406 (4)	C13—C14	1.398 (4)
C5—H5A	0.9300	C13—H13B	0.9300
C6—C7	1.401 (3)	C14—C15	1.362 (4)
C8—C9	1.509 (3)	C14—H14C	0.9300
C8—H8A	0.9700	C15—C16	1.405 (3)
C8—H8B	0.9700	C15—H15B	0.9300
C9—C10	1.499 (3)	C16—C17	1.406 (3)

C6—N1—N2	103.55 (18)	C10—C9—H9B	109.5
C1—N2—N1	113.7 (2)	C8—C9—H9B	109.5
C1—N2—C8	127.2 (2)	H9A—C9—H9B	108.1
N1—N2—C8	118.95 (18)	N12—C10—C9	112.2 (2)
N2—C1—C7	106.6 (2)	N12—C10—H10B	109.2
N2—C1—H1A	126.7	C9—C10—H10B	109.2
C7—C1—H1A	126.7	N12—C10—H10C	109.2
C3—C2—C7	118.4 (3)	C9—C10—H10C	109.2
C3—C2—H2A	120.8	H10B—C10—H10C	107.9
C7—C2—H2A	120.8	C16—N11—N12	103.05 (18)
C2—C3—C4	121.9 (3)	C11—N12—N11	113.89 (19)
C2—C3—H3A	119.0	C11—N12—C10	126.6 (2)
C4—C3—H3A	119.0	N11—N12—C10	119.37 (19)
C5—C4—C3	121.5 (3)	N12—C11—C17	107.1 (2)
C5—C4—H4A	119.3	N12—C11—H11B	126.5
C3—C4—H4A	119.3	C17—C11—H11B	126.5
C4—C5—C6	117.7 (3)	C13—C12—C17	118.5 (2)
C4—C5—H5A	121.1	C13—C12—H12B	120.8
C6—C5—H5A	121.1	C17—C12—H12B	120.8
N1—C6—C7	111.5 (2)	C12—C13—C14	121.4 (2)
N1—C6—C5	127.7 (2)	C12—C13—H13B	119.3
C7—C6—C5	120.7 (2)	C14—C13—H13B	119.3
C1—C7—C6	104.6 (2)	C15—C14—C13	122.1 (2)
C1—C7—C2	135.6 (3)	C15—C14—H14C	118.9
C6—C7—C2	119.8 (3)	C13—C14—H14C	118.9
N2—C8—C9	111.3 (2)	C14—C15—C16	117.5 (2)
N2—C8—H8A	109.4	C14—C15—H15B	121.2
C9—C8—H8A	109.4	C16—C15—H15B	121.2
N2—C8—H8B	109.4	N11—C16—C15	127.3 (2)
C9—C8—H8B	109.4	N11—C16—C17	112.0 (2)
H8A—C8—H8B	108.0	C15—C16—C17	120.7 (2)
C10—C9—C8	110.7 (2)	C11—C17—C16	103.9 (2)
C10—C9—H9A	109.5	C11—C17—C12	136.2 (2)
C8—C9—H9A	109.5	C16—C17—C12	119.8 (2)

C6—N1—N2—C1	−0.6 (2)	C8—C9—C10—N12	173.5 (2)
C6—N1—N2—C8	−176.64 (19)	C16—N11—N12—C11	0.5 (3)
N1—N2—C1—C7	0.3 (3)	C16—N11—N12—C10	−176.1 (2)
C8—N2—C1—C7	176.0 (2)	C9—C10—N12—C11	126.4 (3)
C7—C2—C3—C4	−1.2 (4)	C9—C10—N12—N11	−57.4 (3)
C2—C3—C4—C5	1.0 (5)	N11—N12—C11—C17	0.0 (3)
C3—C4—C5—C6	0.2 (5)	C10—N12—C11—C17	176.3 (2)
N2—N1—C6—C7	0.6 (3)	C17—C12—C13—C14	1.0 (4)
N2—N1—C6—C5	−179.3 (2)	C12—C13—C14—C15	0.3 (4)
C4—C5—C6—N1	178.9 (3)	C13—C14—C15—C16	−2.1 (4)
C4—C5—C6—C7	−1.0 (4)	N12—N11—C16—C15	179.2 (2)
N2—C1—C7—C6	0.1 (2)	N12—N11—C16—C17	−0.8 (2)
N2—C1—C7—C2	178.5 (3)	C14—C15—C16—N11	−177.3 (2)
N1—C6—C7—C1	−0.5 (3)	C14—C15—C16—C17	2.7 (4)
C5—C6—C7—C1	179.5 (2)	N12—C11—C17—C16	−0.5 (3)
N1—C6—C7—C2	−179.2 (2)	N12—C11—C17—C12	−177.6 (3)
C5—C6—C7—C2	0.8 (4)	N11—C16—C17—C11	0.8 (3)
C3—C2—C7—C1	−177.9 (3)	C15—C16—C17—C11	−179.2 (2)
C3—C2—C7—C6	0.4 (4)	N11—C16—C17—C12	178.5 (2)
C1—N2—C8—C9	−97.6 (3)	C15—C16—C17—C12	−1.5 (3)
N1—N2—C8—C9	77.9 (3)	C13—C12—C17—C11	176.4 (3)
N2—C8—C9—C10	−176.7 (2)	C13—C12—C17—C16	−0.4 (4)

Experimental details

Crystal data
Chemical formula	C₁₇H₁₆N₄
M_r	276.34
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	298
a, b, c (Å)	8.182 (2), 10.549 (4), 34.179 (9)
V (Å³)	2950.1 (16)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.08
Crystal size (mm)	0.60 × 0.40 × 0.18

Data collection
Diffractometer	Siemens P4 diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	8195, 2621, 1607
R_int	0.042
(sin θ/λ)_max (Å⁻¹)	0.597

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.049, 0.162, 1.10
No. of reflections	2621
No. of parameters	191
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.20, −0.21

Computer programs: XSCANS (Siemens, 1996), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006).

Acknowledgements

The authors thank the PAICyT program (Programa de Apoyo a la Investigación Científica y Tecnológica) of the Universidad Autónoma de Nuevo León for supporting this work (project No. T004–09).

References

Alkorta, I. & Elguero, J. (2005). J. Phys. Org. Chem. 18, 719–724. Web of Science CrossRef CAS Google Scholar
Hurtado, J., Mac-Leod Carey, D., Muñoz-Castro, A., Arratia-Pérez, R., Quijada, R., Wu, G., Rojas, R. & Valderrama, M. (2009). J. Organomet. Chem. 694, 2636–2641. Web of Science CSD CrossRef CAS Google Scholar
Long, L., Liu, B.-N., Liu, M. & Liu, D.-K. (2011). Acta Cryst. E67, o1546. Web of Science CSD CrossRef IUCr Journals Google Scholar
Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453–457. Web of Science CrossRef CAS IUCr Journals Google Scholar
Ramos Silva, M., Moreira, V. M., Cardoso, C., Matos Beja, A. & Salvador, J. A. R. (2008). Acta Cryst. C64, o217–o219. Web of Science CSD CrossRef IUCr Journals Google Scholar
Rodríguez de Barbarín, C., Nájera, B., Elizondo, P. & Cerda, P. (2006). Acta Cryst. E62, o5423–o5424. Web of Science CSD CrossRef IUCr Journals Google Scholar
Saczewski, F., Saczewski, J. & Gdaniec, M. (2001). Chem. Pharm. Bull. 49, 1203–1206. Web of Science CSD CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Siemens (1996). XSCANS. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. Google Scholar
Wu, C., Fang, Y., Larock, R. C. & Shi, F. (2010). Org. Lett. 12, 2234–2237. Web of Science CrossRef CAS PubMed Google Scholar
Yu, H.-Y., Li, B.-Z. & Guo, Y.-M. (2006). Chin. J. Chem. Phys. 19, 233–237. Web of Science CrossRef CAS Google Scholar
Zhou, X., Qin, X. & Zhang, J. (2010). Acta Cryst. E66, o2732. Web of Science CSD CrossRef IUCr Journals Google Scholar