tert-Butyl imidazole-1-carboxyl­ate

Kerscher, T.; Prommnitz, T.; Klüfers, P.; Mayer, P.

doi:10.1107/S1600536809003110

organic compounds

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ISSN: 2056-9890

Volume 65| Part 2| February 2009| Page o405

doi:10.1107/S1600536809003110

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tert-Butyl imidazole-1-carboxylate

Tobias Kerscher,^a Tanja Prommnitz,^a Peter Klüfers ^a and Peter Mayer ^a ^*

^aLudwig-Maximilians Universität, Department Chemie und Biochemie, Butenandtstrasse 5–13 (Haus D), 81377 München, Germany
^*Correspondence e-mail: kluef@cup.uni-muenchen.de

(Received 19 January 2009; accepted 26 January 2009; online 28 January 2009)

In the title compound, C₈H₁₂N₂O₂, molecules are interconnected by weak C—H⋯O contacts with H⋯O distances of 2.30 Å, resulting in the formation of chains along [100]. According to graph-set analysis, the unitary descriptor of these chains is C(5). In addition, there are π–π stacking interactions between pyrazole rings (centroid distance = 3.878 Å and ring plane distance = 3.26 Å).

Related literature

The title compound is a well known organic compound and was prepared according to a recently published procedure (Jia et al., 2007 ). For details of graph-set analysis see: Etter et al. (1990 ); Bernstein et al. (1995 ).

Experimental

Crystal data

C₈H₁₂N₂O₂
M_r = 168.19
Monoclinic, P 2₁ /c
a = 5.9952 (2) Å
b = 13.2507 (4) Å
c = 11.5564 (4) Å
β = 94.201 (2)°
V = 915.58 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 200 (2) K
0.50 × 0.38 × 0.38 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: none
6875 measured reflections
2097 independent reflections
1650 reflections with I > 2σ(I)
R_int = 0.026

Refinement

R[F² > 2σ(F²)] = 0.040
wR(F²) = 0.104
S = 1.07
2097 reflections
113 parameters
H-atom parameters constrained
Δρ_max = 0.17 e Å⁻³
Δρ_min = −0.16 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1⋯O2ⁱ	0.95	2.30	3.1949 (16)	156
Symmetry code: (i) x-1, y, z.

Data collection: COLLECT (Nonius, 2004 ); cell refinement: SCALEPACK (Otwinowski & Minor, 1997 ); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809003110/bt2854sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809003110/bt2854Isup2.hkl

checkCIF report

Comment top

The title compound was synthesized in a multistep sythesis in an attempt to create new complexing ligands.

The molecule is an imidazole protected by the tert-butyloxycarbonyle (Boc) group in the 1 position (see Fig. 1).

The crystal packing is shown in Fig. 2. In the crystal, weak C—H···O contacts along [100] which can be described according to graph-set analysis (Etter et al., 1990; Bernstein et al., 1995) with a unitary C(5) descriptor (see Fig. 3), lead to chain like structures of dimeric units which are formed by π-type interaction of two imidazole rings (see Fig. 4). The two imidazole rings are separated by about 3.26 Å and shifted, which results in only about half of one ring overlapping with the other ring (see Fig. 5).

Interestingly the imidazoles do not form longer strands of π-type interacting aromatic systems but only dimeric units which might be due to the large space occupied by the Boc protecting group which leads to separate strands of C—H···O bridged dimeric units (see Fig. 2).

Related literature top

The title compound is a well known organic compound and was prepared according to a recently published procedure (Jia et al., 2007). For details of graph-set analysis see: Etter et al. (1990); Bernstein et al. (1995).

Experimental top

Boc₂O was reacted solvent free with one equivalent of imidazole. After the CO₂ gas evolution had finished, the byproduct, t-butanole, was removed by fine vacuum and big colorless crystals of the title compound were obtained.

Computing details top

Data collection: COLLECT (Nonius, 2004); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	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. The packing of the title compound, viewed along [100].
	Fig. 3. Weak C—H···O interactions lead to chain-like structures in the crystal structure along [100] shown here normal to [001]. Symmetry codes: (i) x + 1, y, z; (ii) x - 1, y, z.
	Fig. 4. π interaction leads to dimeric units shown here normal to [100]. Symmetry code: (i) -x, -y, -z.
	Fig. 5. The dimeric units formed by π interaction are shifted, so that only half of the imidazole rings overlap. Two of the imidazole rings are shown here, normal to [001]. Symmetry code: (i) -x, -y, -z.

tert-Butyl imidazole-1-carboxylate top

Crystal data top

C₈H₁₂N₂O₂	F(000) = 360
M_r = 168.19	D_x = 1.220 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3660 reflections
a = 5.9952 (2) Å	θ = 3.1–27.5°
b = 13.2507 (4) Å	µ = 0.09 mm⁻¹
c = 11.5564 (4) Å	T = 200 K
β = 94.201 (2)°	Block, colourless
V = 915.58 (5) Å³	0.50 × 0.38 × 0.38 mm
Z = 4

Data collection top

Nonius KappaCCD diffractometer	1650 reflections with I > 2σ(I)
Radiation source: rotating anode	R_int = 0.026
MONTEL, graded multilayered X-ray optics monochromator	θ_max = 27.5°, θ_min = 3.4°
CCD; rotation images; thick slices scans	h = −7→7
6875 measured reflections	k = −17→17
2097 independent reflections	l = −14→15

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)] = 0.040	H-atom parameters constrained
wR(F²) = 0.104	w = 1/[σ²(F_o²) + (0.0396P)² + 0.2307P] where P = (F_o² + 2F_c²)/3
S = 1.07	(Δ/σ)_max < 0.001
2097 reflections	Δρ_max = 0.17 e Å⁻³
113 parameters	Δρ_min = −0.16 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008)
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.063 (6)

Crystal data top

C₈H₁₂N₂O₂	V = 915.58 (5) Å³
M_r = 168.19	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 5.9952 (2) Å	µ = 0.09 mm⁻¹
b = 13.2507 (4) Å	T = 200 K
c = 11.5564 (4) Å	0.50 × 0.38 × 0.38 mm
β = 94.201 (2)°

Data collection top

Nonius KappaCCD diffractometer	1650 reflections with I > 2σ(I)
6875 measured reflections	R_int = 0.026
2097 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.040	0 restraints
wR(F²) = 0.104	H-atom parameters constrained
S = 1.07	Δρ_max = 0.17 e Å⁻³
2097 reflections	Δρ_min = −0.16 e Å⁻³
113 parameters

Special details top

Refinement. Hydrogen atoms were placed in calculated positions (C–H 0.95 Å for aromatic C atoms and C–H 0.98 Å for methyl C atoms) and were included in the refinement in the riding model approximation with U(H) set to 1.2 U_eq(C) for aromatic C atoms and 1.5 U_eq(C) for methyl C atoms.

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

	x	y	z	U_iso*/U_eq
O1	0.15042 (14)	0.21450 (6)	0.03780 (8)	0.0356 (3)
O2	0.50241 (15)	0.15584 (8)	0.07833 (10)	0.0527 (3)
N1	0.19880 (17)	0.06402 (8)	0.12264 (9)	0.0329 (3)
N2	−0.0623 (2)	−0.03954 (9)	0.17875 (11)	0.0442 (3)
C1	−0.0253 (2)	0.04699 (10)	0.13009 (11)	0.0359 (3)
H1	−0.1397	0.0927	0.1031	0.043*
C2	0.1485 (2)	−0.08085 (11)	0.20408 (13)	0.0450 (4)
H2	0.1750	−0.1445	0.2404	0.054*
C3	0.3103 (2)	−0.01943 (10)	0.17071 (12)	0.0410 (3)
H3	0.4671	−0.0307	0.1784	0.049*
C4	0.3034 (2)	0.14897 (10)	0.07701 (11)	0.0350 (3)
C5	0.2187 (2)	0.30947 (10)	−0.01876 (12)	0.0373 (3)
C6	−0.0052 (3)	0.35703 (12)	−0.05516 (15)	0.0526 (4)
H6A	−0.0861	0.3708	0.0138	0.079*
H6B	−0.0929	0.3107	−0.1065	0.079*
H6C	0.0187	0.4204	−0.0963	0.079*
C7	0.3515 (3)	0.37416 (11)	0.06973 (13)	0.0485 (4)
H7A	0.4941	0.3410	0.0926	0.073*
H7B	0.2661	0.3830	0.1382	0.073*
H7C	0.3801	0.4402	0.0357	0.073*
C8	0.3472 (3)	0.28433 (12)	−0.12317 (13)	0.0501 (4)
H8A	0.2566	0.2400	−0.1756	0.075*
H8B	0.4871	0.2501	−0.0974	0.075*
H8C	0.3812	0.3467	−0.1640	0.075*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0293 (5)	0.0336 (5)	0.0438 (5)	−0.0001 (3)	0.0018 (4)	0.0068 (4)
O2	0.0279 (5)	0.0595 (7)	0.0709 (7)	0.0038 (4)	0.0052 (5)	0.0188 (6)
N1	0.0322 (6)	0.0335 (6)	0.0329 (5)	0.0020 (4)	0.0007 (4)	0.0020 (4)
N2	0.0469 (7)	0.0399 (6)	0.0458 (7)	−0.0045 (5)	0.0035 (5)	0.0022 (5)
C1	0.0334 (7)	0.0376 (7)	0.0366 (7)	−0.0013 (5)	0.0017 (5)	−0.0004 (5)
C2	0.0549 (9)	0.0359 (7)	0.0436 (8)	0.0016 (6)	0.0004 (6)	0.0049 (6)
C3	0.0424 (8)	0.0385 (7)	0.0413 (7)	0.0078 (6)	−0.0022 (6)	0.0036 (6)
C4	0.0312 (7)	0.0384 (7)	0.0353 (6)	0.0023 (5)	0.0016 (5)	0.0028 (5)
C5	0.0389 (7)	0.0338 (7)	0.0392 (7)	−0.0034 (5)	0.0036 (5)	0.0049 (5)
C6	0.0507 (9)	0.0407 (8)	0.0654 (10)	0.0045 (7)	−0.0025 (7)	0.0133 (7)
C7	0.0532 (9)	0.0456 (8)	0.0470 (8)	−0.0127 (7)	0.0054 (7)	−0.0033 (7)
C8	0.0600 (10)	0.0514 (9)	0.0397 (8)	−0.0053 (7)	0.0093 (7)	0.0038 (7)

Geometric parameters (Å, º) top

O1—C4	1.3187 (15)	C5—C6	1.5144 (19)
O1—C5	1.4892 (15)	C5—C7	1.5147 (19)
O2—C4	1.1958 (15)	C5—C8	1.515 (2)
N1—C1	1.3714 (16)	C6—H6A	0.9800
N1—C3	1.3870 (16)	C6—H6B	0.9800
N1—C4	1.4094 (17)	C6—H6C	0.9800
N2—C1	1.3032 (17)	C7—H7A	0.9800
N2—C2	1.3886 (19)	C7—H7B	0.9800
C1—H1	0.9500	C7—H7C	0.9800
C2—C3	1.344 (2)	C8—H8A	0.9800
C2—H2	0.9500	C8—H8B	0.9800
C3—H3	0.9500	C8—H8C	0.9800

C4—O1—C5	120.04 (10)	C6—C5—C8	111.24 (12)
C1—N1—C3	106.82 (11)	C7—C5—C8	112.92 (12)
C1—N1—C4	128.28 (10)	C5—C6—H6A	109.5
C3—N1—C4	124.90 (11)	C5—C6—H6B	109.5
C1—N2—C2	104.88 (11)	H6A—C6—H6B	109.5
N2—C1—N1	111.73 (11)	C5—C6—H6C	109.5
N2—C1—H1	124.1	H6A—C6—H6C	109.5
N1—C1—H1	124.1	H6B—C6—H6C	109.5
C3—C2—N2	111.44 (12)	C5—C7—H7A	109.5
C3—C2—H2	124.3	C5—C7—H7B	109.5
N2—C2—H2	124.3	H7A—C7—H7B	109.5
C2—C3—N1	105.13 (12)	C5—C7—H7C	109.5
C2—C3—H3	127.4	H7A—C7—H7C	109.5
N1—C3—H3	127.4	H7B—C7—H7C	109.5
O2—C4—O1	128.48 (12)	C5—C8—H8A	109.5
O2—C4—N1	121.79 (11)	C5—C8—H8B	109.5
O1—C4—N1	109.72 (10)	H8A—C8—H8B	109.5
O1—C5—C6	101.94 (10)	C5—C8—H8C	109.5
O1—C5—C7	109.24 (11)	H8A—C8—H8C	109.5
C6—C5—C7	111.30 (12)	H8B—C8—H8C	109.5
O1—C5—C8	109.63 (11)

C2—N2—C1—N1	−0.07 (15)	C5—O1—C4—N1	−177.82 (10)
C3—N1—C1—N2	0.14 (15)	C1—N1—C4—O2	178.00 (13)
C4—N1—C1—N2	−179.21 (12)	C3—N1—C4—O2	−1.2 (2)
C1—N2—C2—C3	−0.04 (16)	C1—N1—C4—O1	−0.98 (18)
N2—C2—C3—N1	0.12 (16)	C3—N1—C4—O1	179.77 (11)
C1—N1—C3—C2	−0.15 (14)	C4—O1—C5—C6	176.89 (11)
C4—N1—C3—C2	179.23 (12)	C4—O1—C5—C7	−65.27 (15)
C5—O1—C4—O2	3.3 (2)	C4—O1—C5—C8	58.95 (15)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···O2ⁱ	0.95	2.30	3.1949 (16)	156

Symmetry code: (i) x−1, y, z.

Experimental details

Crystal data
Chemical formula	C₈H₁₂N₂O₂
M_r	168.19
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	200
a, b, c (Å)	5.9952 (2), 13.2507 (4), 11.5564 (4)
β (°)	94.201 (2)
V (Å³)	915.58 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.09
Crystal size (mm)	0.50 × 0.38 × 0.38

Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	6875, 2097, 1650
R_int	0.026
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.104, 1.07
No. of reflections	2097
No. of parameters	113
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.17, −0.16

Computer programs: COLLECT (Nonius, 2004), SCALEPACK (Otwinowski & Minor, 1997), SCALEPACK and DENZO (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···O2ⁱ	0.95	2.30	3.1949 (16)	156

Symmetry code: (i) x−1, y, z.

Acknowledgements

TK thanks the Hanns Seidel Stiftung for a personal grant funded by the German Bundesministerium für Bildung und Forschung.

References

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