2-Oxo-2,3-dihydro-1H-imidazo[1,2-a]pyridinium iodide

Abstract

In the title compound, C₇H₇N₂O⁺·I⁻, the carbonyl C and O atoms of the cation and the iodide ion are situated on mirror planes. The mean plane of the imidazo[1,2-d]pyridinium cation is perpendicular to the mirror plane as a consequence of the disorder of the cation over two opposite orientations of equal occupancy. In the crystal, N—H⋯I interactions are present.

Related literature

For the synthesis of imidazo[1,2-a]pyridinium chloride or bromide, see: Newton et al. (1984 ▶); Baumann et al. (1986 ▶). For the derivatization of imidazo[1,2-a]pyridinium and related structures, see: Plutecka et al. (2006 ▶); Hoffmann et al. (2005 ▶); Qiao et al. (2006 ▶).

Experimental

Crystal data

• C₇H₇N₂O⁺·I⁻

• M _r = 262.05

• Orthorhombic,

• a = 14.597 (2) Å

• b = 8.2044 (18) Å

• c = 7.0926 (15) Å

• V = 849.4 (3) ų

• Z = 4

• Mo Kα radiation

• μ = 3.71 mm⁻¹

• T = 298 K

• 0.48 × 0.45 × 0.23 mm

Data collection

• Bruker SMART 1000 CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2001 ▶) T _min = 0.269, T _max = 0.482

• 3631 measured reflections

• 806 independent reflections

• 691 reflections with I > 2σ(I)

• R _int = 0.064

Refinement

• R[F ² > 2σ(F ²)] = 0.036

• wR(F ²) = 0.103

• S = 1.05

• 806 reflections

• 73 parameters

• 24 restraints

• H-atom parameters constrained

• Δρ_max = 0.70 e Å⁻³

• Δρ_min = −0.93 e Å⁻³

Data collection: SMART (Bruker, 2001 ▶); cell refinement: SAINT (Bruker, 2001 ▶); data reduction: SAINT; 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.

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—H2A⋯I1i	1.03	2.85	3.80 (2)	153

Symmetry code: (i) .

supplementary crystallographic information

Comment

Imidazo[1,2-a]pyridine derivatives have been investigated as important intermediates in organic synthesis and useful agents in medicinal chemistry. Imidazo[1,2-a]pyridinium chloride or bromide is accessible from the reaction of alkyl haloacetate with 2-aminopyridine compounds (Newton et al., 1984; Baumann et al., 1986), and can be further derivatised (Plutecka et al., 2006; Hoffmann et al., 2005). The reaction of 2-aminopyridine and chloroacetic acid under basic condition gave rise to, after acidification, 3,3-bis(carboxymethyl) imidazo[1,2-a]pyridine-2-one (Qiao et al., 2006). Here we report on the synthesis and structure of the title compound (I), which was obtained from the reaction of iodoacetic acid with 2-aminopyridine under basic condition.

The structure of (I) (Fig. 1) consists of imidazo[1,2-a]pyridinium cations and iodide anions. In the cation, the six-membered and five-membered rings are coplanar with a dihedral angle of 0.48°. However, the four C/N atoms in the ring system (Fig. 1) are found to be disordered. The structure may be seen as two molecules being in one crystallographic position, with an occupancy of 0.5 for each C/N atom involved. Thus, in one molecule the five-membered ring is N2/C2/C1/N1a/C3a, and in another molecule - C3/N1/C1/C2a/N2a.

Experimental

A mixture of 2-aminopyridine (1.132 g, 0.012 mol), ICH₂COOH (5.592 g, 0.030 mol) and Na₂CO₃ (2.549 g, 0.024 mol) was placed in 60 ml of distilled water. After the evolution of bubbles was over, the mixture of was heated at reflux for 6 h, while the pH was adjusted to 8–9 using aqueous NaOH (0.1 mol/l) solution, at a time interval of 0.5 h. The resulting deep red solution was cooled to room temperature and acidified with hydrochloric acid till pH 2–3 (during which some red solid was formed, but could be dissolved on warming to 40°C). On standing still at room temperature, deep red crystals were grown after one month. IR (KBr): 3465, 3076, 1751, 1650, 1511, 1330, 1185, 792, 608 cm^-1.

Refinement

All H atoms were positioned geometrically and refined using a riding model with C—H = 0.93–0.97 Å, N—H = 0.86 Å, U_iso(H) = 1.2U_eq(C,N).

Figures

Fig. 1.

The molecular structure, with atom labels and 25% probability displacement ellipsoids [symmetry code: (a) x, 1/2 - y, z].

Crystal data

C7H7N2O+·I−	Dx = 2.049 Mg m−3
Mr = 262.05	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnma	Cell parameters from 1914 reflections
a = 14.597 (2) Å	θ = 2.5–27.2°
b = 8.2044 (18) Å	µ = 3.71 mm−1
c = 7.0926 (15) Å	T = 298 K
V = 849.4 (3) Å3	Block, red
Z = 4	0.48 × 0.45 × 0.23 mm
F(000) = 496

Data collection

Bruker SMART 1000 CCD area-detector diffractometer	806 independent reflections
Radiation source: fine-focus sealed tube	691 reflections with I > 2σ(I)
graphite	Rint = 0.064
ω scans	θmax = 25.0°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Bruker, 2001)	h = −17→13
Tmin = 0.269, Tmax = 0.482	k = −9→9
3631 measured reflections	l = −5→8

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)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.103	H-atom parameters constrained
S = 1.05	w = 1/[σ2(Fo2) + (0.0619P)2 + 0.9786P] where P = (Fo2 + 2Fc2)/3
806 reflections	(Δ/σ)max < 0.001
73 parameters	Δρmax = 0.70 e Å−3
24 restraints	Δρmin = −0.93 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.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
I1	0.41289 (4)	0.2500	0.91066 (7)	0.0537 (3)
C4	0.1109 (3)	0.0822 (7)	0.9883 (8)	0.0519 (13)
H4	0.1112	−0.0311	0.9844	0.062*
C5	0.0758 (4)	0.1656 (8)	1.1372 (9)	0.0551 (14)
H5	0.0517	0.1091	1.2395	0.066*
O1	0.2504 (5)	0.2500	0.4103 (7)	0.0724 (19)
C1	0.2120 (6)	0.2500	0.5605 (11)	0.053 (2)
C2	0.184 (3)	0.103 (3)	0.674 (4)	0.050 (9)	0.50
H2A	0.1384	0.0386	0.6073	0.060*	0.50
H2B	0.2363	0.0342	0.7024	0.060*	0.50
N2	0.146 (4)	0.174 (3)	0.846 (4)	0.039 (8)	0.50
N1	0.186 (2)	0.1164 (19)	0.666 (3)	0.049 (7)	0.50
H1	0.1935	0.0170	0.6309	0.058*	0.50
C3	0.146 (4)	0.161 (4)	0.831 (5)	0.037 (8)	0.50

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
I1	0.0550 (4)	0.0434 (4)	0.0627 (4)	0.000	−0.0103 (2)	0.000
C4	0.044 (3)	0.044 (3)	0.068 (3)	0.002 (2)	−0.003 (3)	0.009 (3)
C5	0.046 (3)	0.064 (4)	0.056 (3)	0.000 (2)	−0.001 (2)	0.013 (3)
O1	0.070 (4)	0.099 (5)	0.049 (3)	0.000	0.003 (3)	0.000
C1	0.047 (5)	0.058 (5)	0.053 (5)	0.000	−0.004 (4)	0.000
C2	0.054 (13)	0.039 (10)	0.057 (12)	−0.006 (8)	0.009 (8)	0.005 (8)
N2	0.032 (10)	0.040 (9)	0.047 (9)	0.004 (7)	−0.003 (7)	−0.002 (6)
N1	0.047 (11)	0.042 (9)	0.058 (11)	0.003 (8)	−0.016 (8)	−0.019 (7)
C3	0.030 (11)	0.034 (10)	0.048 (10)	−0.002 (6)	−0.010 (7)	−0.006 (6)

Geometric parameters (Å, °)

C4—N2	1.357 (9)	C1—N1i	1.381 (9)
C4—C5	1.358 (9)	C1—C2	1.509 (10)
C4—C3	1.387 (9)	C1—C2i	1.509 (10)
C4—H4	0.9300	C2—N2	1.461 (10)
C5—C5i	1.386 (14)	C2—H2A	0.9700
C5—H5	0.9300	C2—H2B	0.9700
O1—C1	1.204 (9)	N1—C3	1.360 (10)
C1—N1	1.381 (9)	N1—H1	0.8600
N2—C4—C5	116.2 (14)	O1—C1—C2i	126.8 (12)
N2—C4—C3	6(3)	N1—C1—C2i	105.8 (7)
C5—C4—C3	121.9 (16)	N1i—C1—C2i	1(3)
N2—C4—H4	121.9	C2—C1—C2i	106 (2)
C5—C4—H4	121.9	N2—C2—C1	103.3 (11)
C3—C4—H4	116.2	N2—C2—H2A	111.1
C4—C5—C5i	120.2 (4)	C1—C2—H2A	111.1
C4—C5—H5	119.9	N2—C2—H2B	111.1
C5i—C5—H5	119.9	C1—C2—H2B	111.1
O1—C1—N1	127.5 (10)	H2A—C2—H2B	109.1
O1—C1—N1i	127.5 (10)	C4—N2—C2	122.9 (19)
N1—C1—N1i	105 (2)	C3—N1—C1	111.7 (10)
O1—C1—C2	126.8 (12)	C3—N1—H1	124.1
N1—C1—C2	1(3)	C1—N1—H1	124.1
N1i—C1—C2	105.8 (7)	N1—C3—C4	136 (2)

Symmetry codes: (i) x, −y+1/2, z.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H2A···I1ii	1.03	2.85	3.80 (2)	153

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