1-Methyl-3-(4-chloro­benzo­yl)imidazo[1,2-a]pyridin-1-ium-2-olate

Victor B Rybakov; Eugene V Babaev

doi:10.1107/S1600536811039614

. 2011 Sep 30;67(Pt 10):o2814. doi: 10.1107/S1600536811039614

1-Methyl-3-(4-chlorobenzoyl)imidazo[1,2-a]pyridin-1-ium-2-olate

Victor B Rybakov ^a,^*, Eugene V Babaev ^a

PMCID: PMC3201236 PMID: 22064572

Abstract

In the molecule of the title compound, C₁₅H₁₁ClN₂O₂, the nine-membered heterobicycle is approximately planar [largest deviation from least-squares plane = 0.012 (2) Å] and forms a dihedral angle of 51.14 (8)° with the plane of the 4-chlorophenyl group. There is a non-classical intramolecular hydrogen bond between the pyridine α-H atom and the O atom of the benzoyl group. The crystal structure is stabilized by weak C—H⋯O and C—H⋯Cl interactions involving the ‘olate’ O atom and the Cl atom attached to the benzoyl group as acceptors.

Related literature

For related structures, see: Friedman et al. (1978 ▶); Rybakov et al. (1999 ▶, 2000a ▶,b ▶, 2001 ▶, 2002 ▶). For the synthesis of 1-methyl-2-oxo-2,3-dihydroimidazopyridinium perchlorate, see: Sych & Gorb (1976 ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶).

Experimental

Crystal data

C₁₅H₁₁ClN₂O₂
M _r = 286.71
Monoclinic,
a = 8.190 (8) Å
b = 13.914 (3) Å
c = 11.675 (4) Å
β = 102.38 (2)°
V = 1299.5 (14) Å³
Z = 4
Mo Kα radiation
μ = 0.30 mm⁻¹
T = 295 K
0.30 × 0.30 × 0.30 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
2675 measured reflections
2546 independent reflections
1486 reflections with I > 2σ(I)
R _int = 0.042
1 standard reflections every 200 reflections intensity decay: 2%

Refinement

R[F ² > 2σ(F ²)] = 0.044
wR(F ²) = 0.107
S = 0.94
2546 reflections
182 parameters
H-atom parameters constrained
Δρ_max = 0.15 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Data collection: CAD-4 Software (Enraf–Nonius, 1994) ▶; cell refinement: CAD-4 Software ▶; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); 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: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811039614/yk2022sup1.cif

e-67-o2814-sup1.cif^{(17.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811039614/yk2022Isup2.hkl

e-67-o2814-Isup2.hkl^{(125.1KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811039614/yk2022Isup3.cml

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
C5—H5⋯O30	0.93	2.30	2.863 (3)	119
C8—H8⋯O2ⁱ	0.93	2.47	3.291 (4)	148
C32—H32⋯Cl34ⁱⁱ	0.93	2.93	3.794 (3)	155

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

The authors are indebted to I. V. Dlinnykh for the preparation of title compound. The authors wish to thank Russian Foundation for Basic Research for covering the licence fee for use of the Cambridge Structural Database ver. 5.32 (Allen, 2002 ▶).

supplementary crystallographic information

Comment

Early we described crystal structures of "pyridylglycine" I (Rybakov et al., 1999) (Fig. 1) and the product of its cyclocondensation – 2-oxoimidazo[1,2-a]pyridine II (Rybakov et al., 2000a) (Fig. 1). According to Sych & Gorb (1976), we have also performed selective N–methylation of II and investigated the molecular and crystal structures of the resulting salt III (Rybakov et al., 2000b) (Fig. 1). In the present paper we continue the sequence I-II-III and report the molecular structure of the acylated derivative of the compound III - the mesoionic 1-methyl-3-(p–chlorobenzoyl)imidazo[1,2-a] pyridinium-2-olate IV (Fig. 1). The acylation of III was performed by using of 4-chlorobenzoyl chloride in the presence of triethylamine leading to green crystals of the derivative IV with the 60% yield.

The molecular structure of the mesoionic compound IV (Fig. 2) displays some remarkable features early observed for analogous fused imidazopyridines (Friedman et al., 1978) and oxazolopyridines (Rybakov et al., 2001; Rybakov et al., 2002). In particular, in the moiety O10═ C30—C3—C2═O2 the bonds length C3—C30 and C2—C3 correspond to single bonds (~1.43 Å), whereas the bonds length C30═O30 and C2═ O2 (~1.23 Å) correspond to double bonds, thus displaying the unusual ylide-like pattern of the imidazolone fragment. On the other hand, the sequence C5═C6–C7═C8 displays alternation of the bonds length, thus corresponding to quasi-diene fragment of the pyridine ring. These facts seem to be common to the entire class of azolopyridinium-2-olates. The intramolecular interaction C5—H5···O30 with parameters H5···O30 = 2.296 Å, C5···O30 = 2.863 (3)Å and angle C5—H5···O30 = 118.83° (Table 1) is found. The molecules in crystal are linked by weak intermolecular interactions: C8—H8···O2ⁱ with parameters H8···O2ⁱ = 2.466 Å, C8···O2ⁱ = 3.291 (4)Å and angle C8—H8···O2ⁱ = 147.86°; C32—H32···Cl34ⁱⁱ with parameters H32···Cl34ⁱⁱ = 2.931 Å, C32···Cl34 = 3.794 (3)Å and angle C32—H32···Cl34ⁱⁱ = 154.93°. Symmetry codes: (i) -x, y + 1/2, -z + 1/2; (ii) -x + 1, y + 1/2, -z + 1/2.

Experimental

1-Methyl-2-oxo-2,3-dihydroimidazopyridinium perchlorate III was obtained as described by Sych & Gorb (1976) (Fig. 2). In order to obtain 1-methyl-3-(4-chlorobenzoyl)imidazo[1,2-a]pyridinium-2-olate IV, triethylamine (2.24 ml, 0.016 mol) was added slowly to the solution of 2.0 g (8 mmol) III in 10 ml of acetonitrile, and 1.4 g (8 mmol) of 4-chlorobenzoil chloride was added to the obtained mixture. The reaction flask was stirred at room temperature for 1 h and then kept overnight. The precipitate was filtered and recrystallized from isopropyl alcohol. The yield was 1.3 g (60%). M.p. 479–481 K. ¹H NMR spectra (DMSO-d₆, p.p.m.): 9.96 (d, 1H, 9-H), 7.85 (dd, 1H, 8-H), 7.68 (m, 2H, p-ClPh), 7.61 (d, 1H, 6-H), 7.44 (m, 2H, p-ClPh), 7.34 (dd, 1H, 7-H), 3.38 (s, 3H, 4-Me). The numbering of protons is given according to the atoms numbering on Fig. 1.