Crystal structure of 2-methoxy-2-[(4-methoxyphenyl)sulfanyl]-1-phenylethanone

In the title β-thiocarbonyl compound, C16H16O3S, the adjacent methoxy and carbonyl O atoms are synperiplanar [the O—C—C—O torsion angle is 19.8 (4)°] and are separated by 2.582 (3) Å. The dihedral angle between the rings is 40.11 (16)°, and the methoxy group is coplanar with the benzene ring to which it is connected [the C—C—O—C torsion angle is 179.1 (3)°]. The most notable feature of the crystal packing is the formation of methine and methyl C—H⋯O(carbonyl) interactions that lead to a supramolecular chain with a zigzag topology along the c axis. Chains pack with no specific intermolecular interactions between them.


S2.1. Synthesis and crystallization
4′-Methoxythiophenol (5.0 g, 36 mmol) was reacted with bromine (1.1 ml, 20 mmol) in dichloromethane (250 ml) on an hydrated silica gel support (25 g of SiO 2 and 12 ml of water) to give 4′-methoxyphenyl disulfide (4.0 g, yield = 80%). A white solid was obtained after filtration and evaporation without further purification (Ali & McDermott, 2002). A solution of 2-methoxy acetophenone (0.80 ml, 5.81 mmol, Sigma-Aldrich) in THF (20 ml), was added drop-wise to a cooled (195 K) solution of diisopropylamine (0.90 ml, 6.39 mmol) and butyllithium (4.30 ml, 5.81 mmol) in THF (30 ml). After 30 minutes, a solution of 4′-methoxyphenyl disulfide (1.780 g, 6.39 mmol) with hexamethylphosphoramide (HMPA) (1.0 ml, 5.81 mmol) dissolved in THF (20 ml) was added drop-wise to the enolate solution (Zoretic & Soja, 1976). After stirring for 3 h, water (50 ml) was added at room temperature and extraction with dichloromethane was performed. The organic layer was then treated with saturated solution of ammonium chloride until neutral pH, and then dried over anhydrous magnesium sulfate. A brown oil was obtained after evaporation of the solvent. Purification through flash chromatography with toluene was used to remove the non-polar reactant (disulfide) then acetone to give a mixture of both acetophenones (product and reactant). Crystallization was performed by vapour diffusion of n-hexane into a chloroform solution held at 283 K to give pure product (0.3 g, yield = 40%

S2.2. Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H = 0.93-0.98 Å) and were included in the refinement in the riding model approximation, with U iso (H) = 1.2-1.5U eq (C).

Figure 1
The molecular structure of the title compound showing the atom-labelling scheme and displacement ellipsoids at the 35% probability level.

Figure 2
The supramolecular chain in the title compound sustained by C-H···O interactions shown as orange dashed lines.
Hydrogen atoms not participating in C-H···O interactions have been omitted for reasons of clarity.

Figure 3
Unit-cell contents of the title compound shown in projection down the c axis. Intermolecular C-H···O interactions are shown as orange dashed lines. One supramolecular chain has been highlighted in space-filling mode.