3-Phenyl-1H-pyrrolo[2,1-c][1,4]oxazin-1-one

Salman Tariq Khan; Peng Yu; Suchada Chantrapromma; Yong-En Guo; Nighat Afza

doi:10.1107/S1600536810017940

. 2010 May 26;66(Pt 6):o1469. doi: 10.1107/S1600536810017940

3-Phenyl-1H-pyrrolo[2,1-c][1,4]oxazin-1-one

Salman Tariq Khan ^a,^‡, Peng Yu ^a,^*, Suchada Chantrapromma ^b,^§, Yong-En Guo ^a, Nighat Afza ^c

PMCID: PMC2979495 PMID: 21579537

Abstract

The molecule of the title compound, C₁₃H₉NO₂, is slightly twisted with a dihedral angle of 4.85 (9)° between the nine-membered ring system and the phenyl ring. The nine non-H atoms of the 1H-pyrrolo[2,1-c][1,4]oxazin-1-one system are coplanar [r.m.s. deviation = 0.0122 (2) Å]. In the crystal, weak intermolecular C—H⋯O interactions link molecules into chains along [1 Inline graphic 0]. The crystal studied was an inversion twin with a 0.48624 (9):0.51376 (9) domain ratio.

Related literature

For the biological activity and applications of pyrrolo[1,2-a]pyrazine derivatives, see: Bélanger et al. (1983 ▶); Fu et al. (2002 ▶); Micheli et al. (2008 ▶). For a related structure, see: Khan et al. (2010 ▶). For standard bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₁₃H₉NO₂
M _r = 211.21
Monoclinic,
a = 5.870 (1) Å
b = 3.8345 (7) Å
c = 21.733 (4) Å
β = 91.059 (7)°
V = 489.09 (15) Å³
Z = 2
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 113 K
0.22 × 0.18 × 0.08 mm

Data collection

Rigaku Saturn CCD area-detector diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 ▶) T _min = 0.979, T _max = 0.992
4358 measured reflections
1222 independent reflections
1092 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.031
wR(F ²) = 0.085
S = 1.10
1222 reflections
147 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: CrystalClear (Rigaku, 2005 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810017940/rz2449sup1.cif

e-66-o1469-sup1.cif^{(16.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810017940/rz2449Isup2.hkl

e-66-o1469-Isup2.hkl^{(60.4KB, hkl)}

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
C7—H7⋯O2ⁱ	0.95	2.27	3.109 (2)	147

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Symmetry code: (i) Inline graphic .

Acknowledgments

STK acknowledges funding from the Industrial Linkage Programme of Pakistan Council of Scientific and Industrial Research (PCSIR) Laboratories, Pakistan. He also thanks Dr Song Haibin of the State Key Laboratory of Elemento-Organic Chemistry, Nankai University, for the X-ray data collection. PY is grateful to Tianjin University of Science & Technology for a research grant (No. 2009 0431).

supplementary crystallographic information

Comment

A series of pyrrolo[1,2-a]pyrazine compounds show potent and selective non-competitive mGluR5 antagonists properties (Micheli et al., 2008). We previously reported the synthesis and crystal structure of 3-methyl-1H-pyrrolo[2,1-c][1,4]oxazin-1-one (I) (Khan et al., 2010). The title compound (II), which was designed by changing the methyl substituent in (I) to phenyl, is a new key intermediate which can be used as a precursor for the syntheses of muscle relaxant agents (Bélanger et al., 1983) and other biological active compounds (Fu et al., 2002).

The molecule of title compound (Fig. 1) is slightly twisted, the dihedral angle between this nine membered ring system and phenyl ring being 4.85 (9)° and the O1–C6–C8–C9 torsion angle 5.0 (3)°. The nine non-hydrogen atoms of the 1H-pyrrolo[2,1-c][1,4]oxazin-1-one ring system are coplanar with a r.m.s. of 0.0122 (2) Å. The bond lengths are in normal ranges (Allen et al., 1987) and comparable with the related structure (Khan et al., 2010). In the crystal structure (Fig. 2), weak intermolecular C—H···O interactions (Table 1) link the molecules into chains along [110]. These chains are stacked along the b axis.

Experimental

A solution of α-bromo acetophenone (2.37 g, 11.91 mmol) in acetone (25 ml) was dropwise added through a dropping funnel to a slurry of 2,2,2-trichloro-1-(lH-pyrrol-2-yl)ethanone (1.69 g, 7.95 mmol), potassium carbonate (1.98 g, 14.31 mmol) and acetone (20 ml) at room temperature in a 100 ml reaction flask. The reaction mixture was refluxed for 4 h. The solid was then removed by filtration and washed with acetone. The filtrate was concentrated under reduced pressure by rotary evaporator, the residue was partitioned between water (20 ml) and ethyl acetate (40 ml) in a separatory funnel (100 ml). The organic layer was separated and the aqueous phase was washed with ethyl acetate (30 ml x 2). The combined organic layers were washed successively with water (20 ml x 3) and brine solution and dried over anhydrous MgSO₄. After filtration, the solvent was removed by rotary evaporator to obtain the oily residue (1.90 g) which was purified by flash column chromatography (petroleum ether:ethyl acetate, 4:1 v/v) to afford the desired compound as white solid (1.05 g, yield 62.5 %). Colourless needle-shaped single crystals of the title compound suitable for X-ray structure determination were recrystalized from ethyl acetate by slow evaporation of the solvent at room temperature after several days.