1-Methyl-4-nitro-2-(tri­chloro­acetyl)­pyrrole

The crystal structure of the title compound, C₇H₅Cl₃N₂O₃, has been determined in the orthorhombic space group Pbca. The CNO skeleton is essentially planar, except for the carbonyl O atom, which deviates by 0.217 (3) Å. There is a strong interaction between one of the nitro O atoms and a Cl atom of a neighbouring mol­ecule.

Key indicators

• Single-crystal X-ray study
• T = 193 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.047
• wR factor = 0.112
• Data-to-parameter ratio = 13.4

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S1. Comment

In the past decade, Dervan and co-workers have discovered that polyamides with certain numbers of N-methylpyrrole carboxamides and N-methylimidazole carboxamides can recognize and bind in the minor groove of predetermined DNA sequences with high affinity and specificity, comparable to naturally occurring DNA-binding proteins, and further regulate gene expression (Dervan & Büril, 1999; Simon et al., 2000). These properties stimulated our interest in this field. Crystals of the title compound, (I), were obtained as an intermediate in our synthetic investigations of polyamides.

The molecular structure and a packing diagram of (I) are illustrated in Figs. 1 and 2, respectively. Selected geometric parameters of (I) are listed in Table 1. Inspection of these values indicates that there is delocalization of the π-electron density in the pyrrole ring. Furthermore, there are no significant differences from the geometry found in a similar pyrrole (Lu et al., 2003). The 12 atoms N1–N2, O1–O3 and C1–C7 are essentially coplanar, the r.m.s. deviation being 0.088 Å and the maximum deviation from the plane 0.217 (3) Å for O1. There is a strong interaction between O3 and Cl2(1 − x, −1 − y, 1 − z), with an O3···Cl2A distance of 3.015 (2) Å.

S2. Experimental

The title compound, (I), was synthesized according to a literature procedure (Nishiwaki et al., 1988), with minor modification. The product was dissolved in CHCl₃ and the solution was set aside at room temprature. As the solvent slowly evaporated, crystals of (I) were formed.

S3. Refinement

H atoms attached to C atoms were placed in geometrically idealized positions, with Csp²—H = 0.93 Å and Csp³—H = 0.96 Å, and were constrained to ride on their parent atoms, with U_iso(H) = 1.2U_eq(C) and 1.5U_eq(C), respectively.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2000); program(s) used to refine structure: SHELXL97 (Sheldrick, 2000); molecular graphics: SHELXTL/PC (Sheldrick, 1999); software used to prepare material for publication: SHELXTL/PC.

Figures

	Fig. 1. The structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level for non-H atoms.
	Fig. 2. A packing diagram of (I), viewed along the b axis. The strong intermolecular O···Cl interactions are shown as dashed lines.

1-Methyl-4-nitro-2-(trichloroacetyl)pyrrole

Crystal data

C7H5Cl3N2O3	F(000) = 1088
Mr = 271.48	Dx = 1.733 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 3073 reflections
a = 11.590 (4) Å	θ = 2.9–27.2°
b = 10.603 (3) Å	µ = 0.87 mm^−1
c = 16.935 (5) Å	T = 193 K
V = 2081.2 (11) Å^3	Block, yellow
Z = 8	0.20 × 0.20 × 0.20 mm

Data collection

Bruker SMART 1K CCD area-detector diffractometer	1574 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.029
Graphite monochromator	θmax = 25.0°, θmin = 2.4°
ω scans	h = −13→12
7949 measured reflections	k = −11→12
1837 independent reflections	l = −18→20

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)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.112	H-atom parameters constrained
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0553P)^2 + 0.8439P] where P = (Fo^2 + 2Fc^2)/3
1837 reflections	(Δ/σ)max = 0.001
137 parameters	Δρmax = 0.33 e Å^−3
0 restraints	Δρmin = −0.19 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
O2	0.2386 (2)	−0.0288 (2)	1.05488 (14)	0.0763 (7)
Cl1	0.43332 (7)	0.09579 (9)	0.70167 (5)	0.0686 (3)
Cl2	0.66325 (7)	0.18290 (9)	0.67657 (5)	0.0706 (3)
Cl3	0.62763 (9)	−0.05161 (8)	0.75825 (6)	0.0760 (3)
C3	0.4904 (2)	0.1345 (2)	0.88368 (15)	0.0399 (6)
C4	0.4192 (2)	0.0315 (3)	0.88783 (16)	0.0434 (6)
H4	0.4102	−0.0310	0.8498	0.052*
N2	0.2791 (2)	−0.0471 (2)	0.98913 (16)	0.0556 (7)
N1	0.47657 (19)	0.2036 (2)	0.95299 (13)	0.0434 (5)
C2	0.5735 (2)	0.1735 (3)	0.82389 (17)	0.0467 (7)
C5	0.3628 (2)	0.0394 (3)	0.96037 (17)	0.0429 (6)
O1	0.6432 (2)	0.2557 (2)	0.83321 (14)	0.0774 (7)
C1	0.5730 (2)	0.1024 (3)	0.74347 (17)	0.0501 (7)
C6	0.3992 (2)	0.1462 (3)	0.99869 (17)	0.0454 (7)
H6	0.3743	0.1737	1.0480	0.054*
C7	0.5283 (3)	0.3257 (3)	0.97263 (19)	0.0615 (8)
H7A	0.4935	0.3580	1.0199	0.092*
H7B	0.5155	0.3838	0.9300	0.092*
H7C	0.6097	0.3153	0.9808	0.092*
O3	0.2513 (2)	−0.1352 (2)	0.94712 (16)	0.0864 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O2	0.0714 (16)	0.0900 (18)	0.0675 (15)	0.0037 (13)	0.0308 (13)	0.0150 (13)
Cl1	0.0538 (5)	0.1008 (7)	0.0513 (5)	−0.0077 (4)	−0.0042 (4)	−0.0021 (4)
Cl2	0.0628 (5)	0.0948 (7)	0.0542 (5)	−0.0062 (4)	0.0178 (4)	0.0103 (4)
Cl3	0.0930 (7)	0.0576 (5)	0.0775 (6)	0.0200 (5)	0.0132 (5)	−0.0045 (4)
C3	0.0419 (14)	0.0399 (14)	0.0379 (14)	0.0022 (11)	0.0001 (11)	0.0022 (11)
C4	0.0428 (15)	0.0405 (15)	0.0468 (16)	0.0038 (12)	0.0007 (12)	0.0009 (12)
N2	0.0477 (15)	0.0505 (15)	0.0686 (18)	0.0073 (12)	0.0147 (13)	0.0145 (14)
N1	0.0477 (13)	0.0400 (12)	0.0424 (12)	0.0035 (10)	−0.0021 (10)	0.0005 (10)
C2	0.0483 (16)	0.0423 (15)	0.0493 (17)	0.0006 (13)	0.0019 (13)	0.0024 (13)
C5	0.0368 (14)	0.0433 (15)	0.0486 (16)	0.0065 (12)	0.0026 (12)	0.0117 (13)
O1	0.0844 (16)	0.0751 (16)	0.0727 (15)	−0.0386 (14)	0.0210 (13)	−0.0142 (13)
C1	0.0455 (16)	0.0566 (18)	0.0481 (17)	−0.0007 (14)	0.0067 (13)	0.0046 (14)
C6	0.0476 (16)	0.0489 (16)	0.0396 (15)	0.0094 (13)	0.0033 (12)	0.0049 (13)
C7	0.076 (2)	0.0511 (18)	0.0573 (19)	−0.0070 (16)	−0.0014 (17)	−0.0099 (14)
O3	0.0916 (19)	0.0610 (15)	0.107 (2)	−0.0274 (14)	0.0374 (16)	−0.0118 (15)

Geometric parameters (Å, º)

O2—N2	1.224 (3)	N2—C5	1.421 (4)
Cl1—C1	1.769 (3)	N1—C6	1.331 (3)
Cl2—C1	1.762 (3)	N1—C7	1.465 (4)
Cl3—C1	1.769 (3)	C2—O1	1.199 (3)
C3—C4	1.371 (4)	C2—C1	1.556 (4)
C3—N1	1.393 (3)	C5—C6	1.372 (4)
C3—C2	1.457 (4)	C6—H6	0.9300
C4—C5	1.394 (4)	C7—H7A	0.9600
C4—H4	0.9300	C7—H7B	0.9600
N2—O3	1.217 (3)	C7—H7C	0.9600
C4—C3—N1	107.8 (2)	C4—C5—N2	125.7 (3)
C4—C3—C2	131.3 (2)	C2—C1—Cl2	109.0 (2)
N1—C3—C2	120.8 (2)	C2—C1—Cl1	111.87 (19)
C3—C4—C5	106.3 (2)	Cl2—C1—Cl1	107.77 (16)
C3—C4—H4	126.9	C2—C1—Cl3	108.8 (2)
C5—C4—H4	126.9	Cl2—C1—Cl3	109.01 (16)
O3—N2—O2	123.5 (3)	Cl1—C1—Cl3	110.32 (17)
O3—N2—C5	118.4 (3)	N1—C6—C5	108.0 (2)
O2—N2—C5	118.1 (3)	N1—C6—H6	126.0
C6—N1—C3	109.1 (2)	C5—C6—H6	126.0
C6—N1—C7	123.2 (2)	N1—C7—H7A	109.5
C3—N1—C7	127.5 (2)	N1—C7—H7B	109.5
O1—C2—C3	124.0 (3)	H7A—C7—H7B	109.5
O1—C2—C1	118.0 (3)	N1—C7—H7C	109.5
C3—C2—C1	118.0 (2)	H7A—C7—H7C	109.5
C6—C5—C4	108.8 (2)	H7B—C7—H7C	109.5
C6—C5—N2	125.5 (3)
N1—C3—C4—C5	−0.2 (3)	O2—N2—C5—C6	−3.0 (4)
C2—C3—C4—C5	177.0 (3)	O3—N2—C5—C4	−1.5 (4)
C4—C3—N1—C6	−0.2 (3)	O2—N2—C5—C4	178.8 (3)
C2—C3—N1—C6	−177.8 (2)	O1—C2—C1—Cl2	−10.6 (3)
C4—C3—N1—C7	−175.1 (3)	C3—C2—C1—Cl2	170.4 (2)
C2—C3—N1—C7	7.3 (4)	O1—C2—C1—Cl1	−129.7 (3)
C4—C3—C2—O1	−168.0 (3)	C3—C2—C1—Cl1	51.3 (3)
N1—C3—C2—O1	9.0 (4)	O1—C2—C1—Cl3	108.2 (3)
C4—C3—C2—C1	10.9 (4)	C3—C2—C1—Cl3	−70.8 (3)
N1—C3—C2—C1	−172.1 (2)	C3—N1—C6—C5	0.5 (3)
C3—C4—C5—C6	0.5 (3)	C7—N1—C6—C5	175.6 (2)
C3—C4—C5—N2	179.0 (2)	C4—C5—C6—N1	−0.6 (3)
O3—N2—C5—C6	176.7 (3)	N2—C5—C6—N1	−179.1 (2)