5-Chloro-1,3-di­methyl-1H-pyrazole-4-carbaldehyde

In the title compound, C₆H₇ClN₂O, the mol­ecules are situated on mirror planes, so H atoms of two methyl groups were treated as rotationally disordered over two orientations each. The crystal packing exhibits weak inter­molecular C—H⋯O inter­actions and short Cl⋯N contacts of 3.046 (2) Å.

Related literature

For the biological activity of pyrazole derivatives, see: Hamaguchi et al. (1995); Motoba et al. (1992). For a related structure, see: Yokoyama et al. (2004).

Experimental

Crystal data

• C₆H₇ClN₂O

• M_r = 158.59

• Orthorhombic, P n m a

• a = 13.167 (9) Å

• b = 6.463 (5) Å

• c = 8.190 (6) Å

• V = 696.9 (8) ų

• Z = 4

• Mo Kα radiation

• μ = 0.47 mm⁻¹

• T = 113 K

• 0.24 × 0.22 × 0.18 mm

Data collection

• Rigaku Saturn724 CCD diffractometer

• Absorption correction: multi-scan (CrystalClear; Rigaku, 2008) T_min = 0.895, T_max = 0.920

• 7166 measured reflections

• 897 independent reflections

• 726 reflections with I > 2σ(I)

• R_int = 0.049

Refinement

• R[F² > 2σ(F²)] = 0.027

• wR(F²) = 0.081

• S = 1.05

• 897 reflections

• 63 parameters

• H-atom parameters constrained

• Δρ_max = 0.36 e Å⁻³

• Δρ_min = −0.25 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5A⋯O1^i	0.98	2.58	3.220 (3)	123
Symmetry code: (i) x, y, z+1.

Data collection: CrystalClear (Rigaku, 2008); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

S1. Comment

The pyrazole ring is a prominent heterocyclic scaffold in numerous bioactive molecules. Many pyrazole-based compounds are reported to possess diverse biological activities (Motoba et al., 1992; Hamaguchi et al., 1995). The title compound (I), is an important intermediate for the synthesis of agrochemicals and drugs. Details of its crystal structure may be helpful for the design of novel bioactive molecules.

In (I) (Fig. 1), all bond lengths and angles are normal and comparable with those observed in ethyl 4-formyl-1,3-dimethylpyrazole-5-carboxylate (Yokoyama et al., 2004). All molecules in (I) are situated on mirror planes. The crystal packing exhibits weak intermolecular C—H···O interactions (Table 1) and short Cl···N contacts of 3.046 (2) Å.

Related literature

For the biological activity of pyrazole derivatives, see: Hamaguchi et al. (1995); Motoba et al. (1992). For a related structure, see: Yokoyama et al. (2004).

S2. Experimental

To a well stirred cold solution of DMF(60 mmol) was added dropwise phosphoryl trichloride (90 mmol). The resulting mixture was stirred at 273 K for another 20 min. To the above solution was added 1,3-dimethyl- 1H-pyrazol-5(4H)-one (30 mmol), then it was heated to 363 k for 4 h. Completion of the reaction was checked by TLC, the reaction mixture was cooled and poured into cold water(100 ml). The pH of the mixture was adjusted to 7 by sodium hydroxide solution. The resulting solution was extracted with ethyl acetate (3 * 30 ml). The organic layer was dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure, then the residue was recrystallized from ethyl acetate/petroleum ether to give a colourless crystal.

S3. Refinement

All H atoms were placed in calculated positions, with C–H = 0.95, and 0.98 ° A, and included in the final cycles of refinement using a riding model, with U_iso(H) = 1.2U_eq(C). H atoms of two methyl groups were treated as rotationally disordered over two orientations each with occupancies fixed to 0.5.

Computing details

Data collection: CrystalClear (Rigaku, 2008); cell refinement: CrystalClear (Rigaku, 2008); data reduction: CrystalClear (Rigaku, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

Fig. 1. The molecular structure of (I) showing the atomic labels and 30% probability displacement ellipsoids.

5-Chloro-1,3-dimethyl-1H-pyrazole-4-carbaldehyde

Crystal data

C6H7ClN2O	F(000) = 328
Mr = 158.59	Dx = 1.511 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 2460 reflections
a = 13.167 (9) Å	θ = 2.5–27.8°
b = 6.463 (5) Å	µ = 0.47 mm^−1
c = 8.190 (6) Å	T = 113 K
V = 696.9 (8) Å^3	Prism, colourless
Z = 4	0.24 × 0.22 × 0.18 mm

Data collection

Rigaku Saturn724 CCD diffractometer	897 independent reflections
Radiation source: rotating anode	726 reflections with I > 2σ(I)
Multilayer monochromator	Rint = 0.049
Detector resolution: 14.22 pixels mm^-1	θmax = 27.8°, θmin = 2.9°
ω and ϕ scans	h = −16→17
Absorption correction: multi-scan (CrystalClear; Rigaku, 2008)	k = −8→8
Tmin = 0.895, Tmax = 0.920	l = −10→10
7166 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.081	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0516P)^2] where P = (Fo^2 + 2Fc^2)/3
897 reflections	(Δ/σ)max = 0.002
63 parameters	Δρmax = 0.36 e Å^−3
0 restraints	Δρmin = −0.25 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.41884 (3)	0.2500	0.25597 (5)	0.01825 (17)
O1	0.48840 (10)	0.2500	−0.28470 (15)	0.0222 (3)
N1	0.62098 (12)	0.2500	0.23171 (16)	0.0159 (4)
N2	0.70015 (10)	0.2500	0.12266 (17)	0.0166 (3)
C1	0.53190 (11)	0.2500	0.1537 (2)	0.0146 (4)
C2	0.54995 (11)	0.2500	−0.0124 (2)	0.0141 (4)
C3	0.65799 (11)	0.2500	−0.0242 (2)	0.0142 (4)
C4	0.72306 (11)	0.2500	−0.1739 (2)	0.0178 (4)
H4A	0.7015	0.3620	−0.2468	0.027*	0.50
H4B	0.7161	0.1170	−0.2303	0.027*	0.50
H4C	0.7942	0.2710	−0.1426	0.027*	0.50
C5	0.63988 (14)	0.2500	0.4067 (2)	0.0234 (4)
H5A	0.5928	0.3457	0.4603	0.035*	0.50
H5B	0.7099	0.2942	0.4276	0.035*	0.50
H5C	0.6297	0.1102	0.4500	0.035*	0.50
C6	0.47278 (12)	0.2500	−0.1387 (2)	0.0167 (4)
H6	0.4039	0.2500	−0.1041	0.020*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0131 (3)	0.0215 (3)	0.0202 (3)	0.000	0.00588 (14)	0.000
O1	0.0198 (7)	0.0291 (8)	0.0177 (6)	0.000	−0.0013 (5)	0.000
N1	0.0138 (8)	0.0210 (8)	0.0130 (7)	0.000	0.0020 (5)	0.000
N2	0.0119 (7)	0.0226 (8)	0.0153 (7)	0.000	0.0035 (6)	0.000
C1	0.0119 (8)	0.0145 (9)	0.0175 (8)	0.000	0.0017 (6)	0.000
C2	0.0124 (8)	0.0137 (8)	0.0163 (8)	0.000	0.0001 (6)	0.000
C3	0.0125 (8)	0.0137 (9)	0.0163 (8)	0.000	0.0000 (6)	0.000
C4	0.0135 (8)	0.0239 (10)	0.0159 (8)	0.000	0.0008 (6)	0.000
C5	0.0237 (9)	0.0354 (12)	0.0111 (9)	0.000	0.0000 (7)	0.000
C6	0.0119 (8)	0.0182 (9)	0.0199 (8)	0.000	−0.0006 (7)	0.000

Geometric parameters (Å, º)

Cl1—C1	1.7081 (18)	C3—C4	1.495 (2)
O1—C6	1.213 (2)	C4—H4A	0.9800
N1—C1	1.336 (2)	C4—H4B	0.9800
N1—N2	1.373 (2)	C4—H4C	0.9800
N1—C5	1.455 (2)	C5—H5A	0.9800
N2—C3	1.325 (2)	C5—H5B	0.9800
C1—C2	1.381 (2)	C5—H5C	0.9800
C2—C3	1.426 (2)	C6—H6	0.9500
C2—C6	1.450 (2)
C1—N1—N2	110.83 (14)	C3—C4—H4B	109.5
C1—N1—C5	128.43 (15)	H4A—C4—H4B	109.5
N2—N1—C5	120.74 (15)	C3—C4—H4C	109.5
C3—N2—N1	105.82 (13)	H4A—C4—H4C	109.5
N1—C1—C2	108.67 (14)	H4B—C4—H4C	109.5
N1—C1—Cl1	122.06 (14)	N1—C5—H5A	109.5
C2—C1—Cl1	129.27 (13)	N1—C5—H5B	109.5
C1—C2—C3	103.80 (14)	H5A—C5—H5B	109.5
C1—C2—C6	125.60 (15)	N1—C5—H5C	109.5
C3—C2—C6	130.61 (15)	H5A—C5—H5C	109.5
N2—C3—C2	110.88 (14)	H5B—C5—H5C	109.5
N2—C3—C4	120.27 (14)	O1—C6—C2	125.74 (15)
C2—C3—C4	128.84 (15)	O1—C6—H6	117.1
C3—C4—H4A	109.5	C2—C6—H6	117.1
C1—N1—N2—C3	0.0	Cl1—C1—C2—C6	0.0
C5—N1—N2—C3	180.0	N1—N2—C3—C2	0.0
N2—N1—C1—C2	0.0	N1—N2—C3—C4	180.0
C5—N1—C1—C2	180.0	C1—C2—C3—N2	0.0
N2—N1—C1—Cl1	180.0	C6—C2—C3—N2	180.0
C5—N1—C1—Cl1	0.0	C1—C2—C3—C4	180.0
N1—C1—C2—C3	0.0	C6—C2—C3—C4	0.0
Cl1—C1—C2—C3	180.0	C1—C2—C6—O1	180.0
N1—C1—C2—C6	180.0	C3—C2—C6—O1	0.0

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5A···O1^i	0.98	2.58	3.220 (3)	123

Symmetry code: (i) x, y, z+1.