Ethyl 2-[4-(4-methoxybenzyl)-3-methyl-6-oxopyridazin-1-yl]acetate

The inner part of the ester substituent is nearly perpendicular to the dihydropyridazine ring while the ipso carbon of the 4-methoxyphenyl group is close to the above plane. In the crystal, corrugated layers parallel to the ab plane are formed by a combination of C—H⋯O, C—H⋯π(ring) and π-stacking interactions.

data reports the plane of the pyridazine ring. This conformation appears to be the result of the intermolecular -stacking interaction (see below).

Figure 2
Detail of the intermolecular interactions viewed along the c-axis direction. C-HÁ Á ÁO hydrogen bonds are shown by black dashed lines while -stacking and C-HÁ Á Á(ring) interactions are shown, respectively, by orange and green dashed lines.

Figure 1
The title molecule with labelling scheme and 30% probability ellipsoids.
Only the major component of the disordered ethyl group is shown.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C16/C17 ethyl group is disordered and was refined as two components restrained to have comparable geometries. The refined occupancies were 0.715 (10) and 0.285 (10).

Special details
Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, collected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = -30.00 and 210.00°. The scan time was 20 sec/frame.

data-2
IUCrData (2022). 7, x220582 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. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.99 Å). All were included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms. The ethyl group in the ester is disordered over several closely spaced sites that could not be separated so a 2-site model with ISOR restraints on the two carbon atoms was used to approximate the disorder. The geometries of the two components were restrained to be similar.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (