1-[2-(2,4-Dichloro­phenyl)­pent­yl]-1H-1,2,4-triazole

Corrado Rizzoli; Elda Marku; Lucedio Greci

doi:10.1107/S1600536809007120

. 2009 Mar 6;65(Pt 4):o663. doi: 10.1107/S1600536809007120

1-[2-(2,4-Dichlorophenyl)pentyl]-1H-1,2,4-triazole

Corrado Rizzoli ^a,^*, Elda Marku ^b, Lucedio Greci ^c

PMCID: PMC2969042 PMID: 21582408

Abstract

The title compound, C₁₃H₁₅Cl₂N₃, also known as penconazole, crystallizes as a racemate. The dihedral angle between the benzene and triazole rings is 24.96 (13)°. In the crystal structure, molecules are linked into chains running parallel to the c axis by intermolecular C—H⋯N hydrogen-bonding interactions.

Related literature

For the synthesis and toxicity of the title compound, see: Maier et al. (1987 ▶); Worthing (1987 ▶); Tao et al. (2003 ▶). For the crystal structure of a related compound, see: Peeters et al. (1993 ▶).

Experimental

Crystal data

C₁₃H₁₅Cl₂N₃
M _r = 284.18
Monoclinic,
a = 25.083 (8) Å
b = 10.763 (2) Å
c = 11.206 (3) Å
β = 105.654 (3)°
V = 2913.1 (13) Å³
Z = 8
Cu Kα radiation
μ = 3.89 mm⁻¹
T = 297 K
0.23 × 0.20 × 0.16 mm

Data collection

Siemens AED diffractometer
Absorption correction: empirical (refined from ΔF) (DIFABS; Walker & Stuart, 1983 ▶) T _min = 0.432, T _max = 0.538
2737 measured reflections
2611 independent reflections
1183 reflections with I > 2σ(I)
R _int = 0.060
3 standard reflections every 100 reflections intensity decay: 0.01%

Refinement

R[F ² > 2σ(F ²)] = 0.056
wR(F ²) = 0.127
S = 0.99
2611 reflections
163 parameters
H-atom parameters constrained
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: AED (Belletti et al., 1993 ▶); cell refinement: AED; data reduction: AED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶) and SCHAKAL (Keller, 1997 ▶); software used to prepare material for publication: SHELXL97 and PARST95 (Nardelli, 1995 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809007120/hg2483sup1.cif

e-65-0o663-sup1.cif^{(15.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809007120/hg2483Isup2.hkl

e-65-0o663-Isup2.hkl^{(128.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3A⋯N3ⁱ	0.97	2.52	3.489 (4)	174

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Symmetry code: (i) Inline graphic .

Acknowledgments

Financial support from the Universitá Politecnica delle Marche and the Universitá degli Studi di Parma is gratefully acknowledged.

supplementary crystallographic information

Comment

The synthesis of the title compound, I, commonly known as penconazole, was described years ago (Maier et al., 1987). Due to its ability to inhibit the development of fungi by interfering with sterol biosynthesis of their cell membranes, this product was introduced as an agriculture systemic fungicide affecting cucurbits, grapes, pome fruits and vegetables. The advantages of this compound is its low toxicity: acute oral dose (LD50) of 2125 mg/kg for rats (Worthing, 1987). More recently, penconazole was prepared by condensation of 2-(2,4-dichlorophenyl)-1-pentanole with 1,2,4-triazole (Tao et al., 2003), but this method also leads to the formation of 1-(1H-1,3,4-triazol-1-yl)-2-(2,4-dichlorophenyl)-pentane (II) as a by-product. In repeating this reaction, our purpose was the determination of the crystal structure of the desired compound I and the evaluation of the percentage of the by-product II.

The title compound (Fig. 1) crystallizes as a racemate. The triazole ring is substantially planar (maximum deviation from planarity 0.006 (3) Å for atom C2) and forms a dihedral angle of 24.96 (13)° with the benzene ring. The N—N (1.351 (3) Å) and C—N (mean value 1.328 (4) Å) bond lengths within the triazole ring are comparable with those observed in 6-[(4-chlorophenyl)(1H-1,2,4-triazol-1-yl)methyl]-1-methyl-1H-benzotriazole (vorozole; Peeters et al., 1993) and suggest electron delocalization over the ring. In the crystal structure, an intermolecular C—H···N hydrogen bonding interaction (Table 1) link the molecules into chains running parallel to the c axis (Fig. 2).

Experimental

The title compound was prepared according to the literature reports (Tao et al., 2003). This method afforded compounds I and II in a 93:3 ratio. The two compounds were separated by chromatography on SiO₂ column eluting with cyclohexane/ethyl acetate (9:1 v/v). Crystals of the title compound suitable for X-ray analysis were obtained on slow evaporation of an n-pentane solution (m. p. 60–61°C). IR data, ν, cm^-1: 3060, 1597, 1448, 760, 746, 700. ¹H-NMR, δ in CDCL₃: 0.87 (t, 3H, –CH2CH3), 1.23 (sextet, 2H, -CH2CH3), 2.6–2.8 (m,2H, –CHCH2CH2CH3), 3.78 (1H, quintet, –CH2CHCH2-), 4.34 (d, -CH2CH<), 7.23 (1H, speudo-q, H-5, J=8.3 Hz, J=2.2 Hz), 7.38 (1H, d, H-3, J=2.2 Hz), 7.71 (s, 1H, triazolyl-H-3), 7.89 (s,1H, triazolyl-H-5). MS, Calcd for C₁₃H₁₅Cl₂N₃, 284.2; Found. M (%): 250 (12.72), 248 (36.93), 161 (63.69), 159 (100); no molecular ion peak was observed; the highest peaks are those corresponding to the loss of a chlorine atom. The ¹H-NMR spectrum of compound II shows a singlet at δ = 7.89 corresponding to the two equivalent H atoms of the 1,3,4-triazol-1-yl ring, the other part of the spectrum is strictly similar to that of compound I. Melting points were determined by an electrochemical apparatus and were uncorrected. ¹H-NMR spectra were recorded on a Varian Gemini 200 MHz. IR spectra were recorded in the solid state with a Perkin-Elmer MGX1 spectrophotometer equipped with Spectra Tech. Mass spectra were recorded with a Carlo Erba QMD 1000 mass spectrometer in positive EI mode.