Methyl 1H-pyrrole-2-carboxyl­ate

Abstract

The title compound, C₆H₇NO₂, is essentially planar with a dihedral angle of 3.6 (3)° between the pyrrole ring and the methoxy­carbonyl O/C/O/C plane. In the crystal structure, the N atom is a hydrogen-bond donor to the carboxylate C=O O atom of the neighboring mol­ecule. These inter­molecular hydrogen bonds lead to the formation of helical chains along the b axis.

Related literature

For related structures, see: Kerscher, Klüfers, Kügel & Müller (2007 ▶); Kerscher, Klüfers & Kügel (2007 ▶). For graph-set analysis, see: Bernstein et al. (1995 ▶); Etter et al. (1990 ▶).

Experimental

Crystal data

• C₆H₇NO₂

• M _r = 125.13

• Monoclinic,

• a = 7.5346 (19) Å

• b = 5.4598 (14) Å

• c = 14.730 (4) Å

• β = 100.55 (2)°

• V = 595.7 (3) ų

• Z = 4

• Mo Kα radiation

• μ = 0.11 mm⁻¹

• T = 200 K

• 0.38 × 0.16 × 0.06 mm

Data collection

• Oxford Xcalibur KappaCCD diffractometer

• Absorption correction: none

• 2591 measured reflections

• 1103 independent reflections

• 528 reflections with I > 2σ(I)

• R _int = 0.112

Refinement

• R[F ² > 2σ(F ²)] = 0.070

• wR(F ²) = 0.176

• S = 0.95

• 1103 reflections

• 83 parameters

• H-atom parameters constrained

• Δρ_max = 0.27 e Å⁻³

• Δρ_min = −0.26 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2006 ▶); cell refinement: CrysAlis RED (Oxford Diffraction, 2006 ▶); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEPIII (Burnett & Johnson, 1996 ▶), ORTEP-3 (Farrugia, 1997 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

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
N1—H1⋯O2i	0.88	2.06	2.933 (4)	171
C4—H4⋯Cg1ii	0.95	2.63	3.401 (5)	139

Symmetry codes: (i) ; (ii) . Cg1 is the centroid of the pyrrole ring.

supplementary crystallographic information

Comment

The title compound was prepared, in the attempt to create new complexing ligands, as a byproduct. The compound is quite simular to other compounds already published by our group (Kerscher, Klüfers, Kügel & Müller, 2007; Kerscher, Klüfers & Kügel, 2007).

In the molecule, a formic acid methyl ester is in the 2 position of the pyrrole ring (Fig. 1). With a torsion angle for C2–C1–C5–O1 of only about 2.9°, the molecule is, with the exception of the H atoms of the methyl group, nearly planar. Because of this small torsion angle, the molecule is not C_s symmetric.

The hydrogen bonds of the nitrogen to the carboxylate oxygen lead to a chain like hydrogen bonding system which can be described according to graph-set analysis (Etter et al., 1990; Bernstein et al., 1995) with a C(5) descriptor on the unitary level [the rpluto program (Cambridge Crystallographic Data Centre, England) was used for the graph set analyses; one of these strands is shown in Fig. 2].

Considering contacts whose range falls below the sum of van der Waals radii by only about 0.1 Å, a set of weak C–H···π interactions leads to the formation of a second system of strands along [0 1 0] which can be described by a C(2) descriptor (see Fig. 3).

The two strand systems alternate, which means two hydrogen bonding strands are interconnected by a strand of weak C–H···π contacts (this situation is illustrated in Fig. 4) and vice versa, two strands made of weak C–H···π contacts are interconnected by hydrogen bonding strands. This bonding pattern leads to sheet like structures normal to [0 0 1].

The molecular packing of the title compound is shown in Figure 5.

Experimental

The title compound was obtained by reaction of 228 mg (3.40 mmol) of pyrrole with 280 mg (1.70 mmol) phosgene imminium chloride in 6 ml of dry acetonitrile. After removal of the solvent, the remaining green solid was purified by column chromatoghraphy on silica with chloroform as eluent. Sublimation of fraction five yielded the title compound as colorless crystals.

Refinement

H atoms were calculated in ideal geometry, with U_iso(H) = 1.2U_eq(C or N) for all aromatic C- and N-bound H atoms, and with U_iso(H) = 1.5U_eq(C) for the methylgroup H atoms.

Figures

Fig. 1.

The molecular structure of the title compound with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level) for non-H atoms.

Fig. 2.

Strands formed by N–H···O hydrogen bonds along [0 1 0] in the crystal structure of the title compound, viewed along [1 0 0]. Symmetry codes: (i) -x, y + 1/2, 1/2 - z; (ii) x, y + 1, z; (iii) -x, y + 3/2, 1/2 - z.

Fig. 3.

Strands formed by C–H···π contacts along [0 1 0] in the crystal structure of the title compound, viewed along [0 0 1]. Symmetry codes: (i) 1 - x, y + 1/2, 1/2 - z; (ii) 1 - x, y - 1/2, z - 1/2; (iii) x, y - 1, z; (iv) 1 - x, y - 3/2, 1/2 - z; (v) x, y - 2, z.

Fig. 4.

The strands formed by hydrogen bonding in the crystal structure are interconnected by the strands formed by C–H···π contacts.

Fig. 5.

The packing of the title compound, viewed along [0 1 0].

Crystal data

C6H7NO2	F(000) = 264
Mr = 125.13	Dx = 1.395 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 1091 reflections
a = 7.5346 (19) Å	θ = 4.0–27.5°
b = 5.4598 (14) Å	µ = 0.11 mm−1
c = 14.730 (4) Å	T = 200 K
β = 100.55 (2)°	Platelet, colourless
V = 595.7 (3) Å3	0.38 × 0.16 × 0.06 mm
Z = 4

Data collection

Oxford Xcalibur KappaCCD diffractometer	528 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.112
graphite	θmax = 25.5°, θmin = 4.0°
ω–scans	h = −9→9
2591 measured reflections	k = −6→6
1103 independent reflections	l = −17→17

Refinement

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)] = 0.070	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.176	H-atom parameters constrained
S = 0.95	w = 1/[σ2(Fo2) + (0.0745P)2] where P = (Fo2 + 2Fc2)/3
1103 reflections	(Δ/σ)max < 0.001
83 parameters	Δρmax = 0.27 e Å−3
0 restraints	Δρmin = −0.26 e Å−3

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

	x	y	z	Uiso*/Ueq
O1	0.0203 (3)	0.7534 (4)	0.08955 (19)	0.0312 (8)
O2	−0.0644 (3)	0.4755 (5)	0.18723 (19)	0.0331 (8)
N1	0.2637 (4)	0.2221 (6)	0.1856 (2)	0.0286 (9)
H1	0.1960	0.1417	0.2183	0.034*
C1	0.2176 (5)	0.4370 (7)	0.1405 (3)	0.0248 (10)
C5	0.0452 (5)	0.5519 (7)	0.1425 (3)	0.0276 (10)
C6	−0.1459 (5)	0.8847 (7)	0.0877 (3)	0.0378 (12)
H6A	−0.2475	0.7701	0.0753	0.057*
H6B	−0.1594	1.0093	0.0391	0.057*
H6C	−0.1439	0.9640	0.1476	0.057*
C3	0.4923 (5)	0.3236 (7)	0.1182 (3)	0.0275 (10)
H3	0.6054	0.3212	0.0984	0.033*
C4	0.4295 (5)	0.1506 (7)	0.1726 (3)	0.0300 (10)
H4	0.4914	0.0065	0.1967	0.036*
C2	0.3585 (5)	0.5042 (7)	0.0975 (3)	0.0276 (10)
H2	0.3638	0.6461	0.0608	0.033*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
O1	0.0235 (16)	0.0309 (17)	0.0388 (19)	0.0084 (12)	0.0042 (12)	0.0051 (13)
O2	0.0241 (16)	0.0352 (17)	0.041 (2)	0.0013 (13)	0.0090 (14)	−0.0012 (14)
N1	0.025 (2)	0.0251 (19)	0.036 (2)	−0.0002 (15)	0.0059 (15)	−0.0020 (16)
C1	0.024 (2)	0.022 (2)	0.028 (2)	−0.0012 (18)	0.0041 (18)	−0.0015 (17)
C5	0.028 (2)	0.022 (2)	0.030 (2)	0.0005 (18)	−0.0009 (19)	−0.0072 (18)
C6	0.034 (3)	0.037 (3)	0.041 (3)	0.009 (2)	0.004 (2)	0.001 (2)
C3	0.026 (2)	0.031 (2)	0.026 (2)	0.0016 (18)	0.0079 (17)	−0.0016 (19)
C4	0.023 (2)	0.029 (2)	0.035 (3)	0.0024 (19)	−0.0013 (18)	−0.0029 (19)
C2	0.030 (2)	0.026 (2)	0.026 (3)	−0.0026 (19)	0.0051 (19)	0.0019 (19)

Geometric parameters (Å, °)

O1—C5	1.341 (4)	C6—H6A	0.9800
O1—C6	1.439 (4)	C6—H6B	0.9800
O2—C5	1.221 (5)	C6—H6C	0.9800
N1—C4	1.356 (5)	C3—C4	1.377 (5)
N1—C1	1.362 (5)	C3—C2	1.403 (5)
N1—H1	0.8800	C3—H3	0.9500
C1—C2	1.382 (5)	C4—H4	0.9500
C1—C5	1.447 (5)	C2—H2	0.9500
C5—O1—C6	116.6 (3)	O1—C6—H6C	109.5
C4—N1—C1	109.8 (3)	H6A—C6—H6C	109.5
C4—N1—H1	125.1	H6B—C6—H6C	109.5
C1—N1—H1	125.1	C4—C3—C2	107.4 (3)
N1—C1—C2	107.7 (3)	C4—C3—H3	126.3
N1—C1—C5	120.9 (3)	C2—C3—H3	126.3
C2—C1—C5	131.4 (4)	N1—C4—C3	108.0 (3)
O2—C5—O1	123.9 (4)	N1—C4—H4	126.0
O2—C5—C1	124.1 (4)	C3—C4—H4	126.0
O1—C5—C1	112.0 (4)	C1—C2—C3	107.2 (3)
O1—C6—H6A	109.5	C1—C2—H2	126.4
O1—C6—H6B	109.5	C3—C2—H2	126.4
H6A—C6—H6B	109.5
C4—N1—C1—C2	0.0 (4)	C2—C1—C5—O1	2.9 (6)
C4—N1—C1—C5	179.3 (3)	C1—N1—C4—C3	0.3 (4)
C6—O1—C5—O2	0.7 (5)	C2—C3—C4—N1	−0.4 (4)
C6—O1—C5—C1	−179.0 (3)	N1—C1—C2—C3	−0.2 (4)
N1—C1—C5—O2	4.1 (6)	C5—C1—C2—C3	−179.4 (4)
C2—C1—C5—O2	−176.8 (4)	C4—C3—C2—C1	0.4 (4)
N1—C1—C5—O1	−176.2 (3)

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2i	0.88	2.06	2.933 (4)	171
C4—H4···Cg1ii	0.95	2.63	3.401 (5)	139

Symmetry codes: (i) −x, y−1/2, −z+1/2; (ii) −x+1, y−1/2, −z+1/2.