8-Methyl-3-methylsulfanyl-8a,8b-dihydro-5H-1-oxa-2,4-diazaacenaphthylene

In the structure of the diazadihydroacenaphthylene derivative reported here, stabilization is provided by C—H⋯N and C—H⋯π interactions.


Structure description
Diazadihydroacenaphthylene derivatives contain an isoxazoline scaffold and constitute an important class of heterocyclic compounds whose chemical properties have been investigated over the years . This scaffold is used in the synthesis of several complex natural products (Saha & Bhattacharjya, 1997;Copp et al.,1992) and is a pharmacophore of numerous medicinal chemistry compounds (Brandi et al., 2003;King et al., 1982;Bacher et al., 1997;You et al., 1995). It has also been reported that this scaffold has a multiple range of biological activities, covering the agricultural field (Liu & Howe, 1983), medicinal properties such as anticancer, antibiotic (Habeeb et al., 2001;Mallesha et al., 2001), antiviral and anti-HIV (Ichiba et al., 1993) agents.

Synthesis and crystallization
1-[(4-Methylbenzyl)amino]-1-methylthio-2-nitroethylene (236 mg; 1 mmol) was dissolved in 4.4 ml (50 mmol) of triflic acid at a temperature within the range À26 to À15 C under a nitrogen atmosphere. The reaction was monitored as follows: one or two drops of the reacting medium were quenched over ice (about 1 g) and extracted with CH 2 Cl2 2 (0.5 ml). The organic extract was dried over Na 2 CO 3 and was purified by flash chromatography on a silica column (eluent: petroleum ether/ethyl acetate: (85:15, v/v) to afford the title compound (97 mg; 0.441 mmol) as a colourless powder. The powder was dissolved in a minimum of dichloromethane by heating under agitation. To this hot mixture, petroleum ether was added until the formation of a new precipitate started, which dissolved in the resulting mixture upon heating. Upon cooling, colourless Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
Part of the crystal packing of the title compound showing the formation of intermolecular C1-H1Á Á ÁN12 hydrogen bonds along the b axis.
Dashed lines indicate hydrogen bond contacts. H atoms not involved in hydrogen bond interactions have been omitted for clarity.

Figure 3
A view of the crystal packing, showing the -ring interactions (dashed lines). The yellow dots are centroids of rings. H atoms not involved in these interactions have been omitted for clarity.

Figure 1
The molecular structure of the title compound and the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as spheres of arbitrary radius.
crystals suitable for single-crystal X-ray diffraction analysis were obtained, m.p. 120.1 C.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.32 e Å −3 Δρ min = −0.19 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.