Crystal structure and Hirshfeld surface analysis of diethyl 2-[4-(4-fluorophenyl)-2-methyl-4-oxobutan-2-yl]malonate

The title compound was synthesized by reacting diethyl malonate with 1-(4-fluorophenyl)-3-methylbut-2-en-1-one. In the crystal, the molecules are joined by C—H⋯O contacts into infinite chains along the b-axis direction with a C(6) graph-set motif.


Structural commentary
The title compound crystallizes in the monoclinic crystal system in the space group P2 1 /n, with one molecule in the asymmetric unit (Z 0 = 1). The molecular conformation is stabilized by an intramolecular C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interaction (Fig. 1, Table 1) and short O3Á Á ÁO7 contact [3.007 (2) Å ]. All bonds between sp 3 -hybridized atoms adopt staggered conformations, thus indicating that steric tensions are absent from this molecule. The dihedral angle between the two ester groups of the malonate residue is 61.79 (5) ; the dihedral angles formed by aromatic ring with adjacent and opposite ester groups are 56.66 (4) and 16.08 (4) , respectively. The dihedral angle between aromatic ring and ketone carbonyl unit is 14.04 (5) .

Supramolecular features
In the crystal of the title compound, the shortest intermolecular contact is C15-H15BÁ Á ÁO2, which join the molecules into infinite chains with graph-set motif C(6) (Etter et al., 1990) along the b-axis direction (Table 1, Fig. 2). There are also a few other HÁ Á ÁO contacts at the level of the sum of covalent radii.

Figure 2
Crystal packing of the title compound. The C-HÁ Á ÁO hydrogen bonds form infinite chains along the b-axis direction.

Figure 3
Hirshfeld surface of the title compound mapped over d norm .

Figure 1
The asymmetric unit of the title compound with 50% probability ellipsoids with atom labelling. The intramolecular C-HÁ Á Á interaction is shown as a dotted line.
aromatic ring in YOGMEO, YUFSOJ and the title structure are 78.97 (3), 39.37 (2) and 56.66 (4) , respectively. As in the title structure, in YUFSOJ there are intermolecular C-HÁ Á ÁO contacts involving the methyl groups, whereas in YOGMEO the C-HÁ Á ÁO contacts are formed with a hydrogen atom of the aromatic group.

Synthesis and crystallization
To a stirred solution of diethyl malonate (1 g, 6.25 mmol) in tetrahydrofuran (5 ml), sodium hydride (0.33 g, 13.75 mmol) was added at 273 K. The reaction mixture was allowed to stir for 15 min. A solution of 1-(4-fluorophenyl)-3-methylbut-2en-1-one (1.11 g, 6.25 mmol) in THF was added into the reaction mixture. The reaction mixture was then allowed to stir overnight at room temperature. The completion of the reaction was monitored by thin layer chromatography. The reaction mixture was quenched with saturated ammonium chloride and extracted with ethyl acetate (2 Â 25 ml). The combined organic layer was washed with water (2 Â 25 ml), brine (25 ml), dried over sodium sulfate and evaporated under reduced pressure to obtain the crude product, which was purified by column chromatography using 60-120 mesh silica gel with ethyl acetate and hexane eluent (v/v = 1:2). Single crystals of the title compound were obtained by slow evaporation from acetone solvent at room temperature.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All hydrogen atoms were placed in idealized positions (C-H = 0.95-1.00 Å ) and refined using riding model with U iso = 1.2 or 1.5U eq (C). The methyl groups were allowed to rotate.