2,6-Dichloro-1-[(1E)-2-(phenylsulfonyl)ethenyl]benzene

In the title compound, C14H10Cl2O2S, the product of a base-catalyzed condensation followed by decarboxylation of the carboxylate group of the sulfonyl derivative, the configuration of the alkene unit is E. The torsion angle between the alkene unit and the 2,6-dichlorophenyl ring system is −40.8 (3)°. The dihedral angle between the rings is 80.39 (7)°.

In the title compound, C 14 H 10 Cl 2 O 2 S, the product of a basecatalyzed condensation followed by decarboxylation of the carboxylate group of the sulfonyl derivative, the configuration of the alkene unit is E. The torsion angle between the alkene unit and the 2,6-dichlorophenyl ring system is À40.8 (3) . The dihedral angle between the rings is 80.39 (7) .

Related literature
For a review on the use of vinyl sulfones in organic chemistry, see: Simpkins (1990). For the use of phenylsulfonylacetic acid in the formation of vinyl sulfones, see: Baliah & Seshapathirao (1959). For a general review on the condensation of activated methylenes onto aryl aldehydes, see: Jones (1967). For the structure of the related phenyl vinyl sulfone, see: Briggs et al. (1998)

Comment
We recently explored the use of commercially available phenylsulfonylacetic acid under base catalysis with the anticipation of observing the same mode of transfer using sulfonium salts; methylene transfer onto carbonyl derivatives. The use of not sulfonium but sulfonyl functionality does allow for one to explore catalysis, which is a realm of S-ylide chemistry yet to be fully explored. For this study, observed was not only methylene transfer but formation of the condensation adduct vinyl sulfone (an α,β-unsaturated sulfone). Under not base but acid catalysis, this type of condensation is common as previously reported by Baliah & Seshapathirao (1959) and Jones (1967). The title compound, C 14 H 10 Cl 2 O 2 S, was isolated as the major product in moderate yield and offered definitive evidence of the condensation of the 2,6-dichlorobenzaldehyde with phenylsulfonylacetic acid.
The C1-C2 bond distance of 1.320 (3) Å confirms the alkene moiety, the configuration of which is E. This distance is slightly elongated as compared with the comparable distance of 1.313 (3) Å in phenyl vinyl sulfone (PVS) reported by Briggs et al. (1998). Other geometric parameters in the title compound are similar but also subtly affected relative to PVS.

Experimental
To a 0.125M THF solution of phenylsulfonylacetic acid (1 g, 4.99 mmol, 2.0 equiv) was added 439 mg of 2,6-dichlorobenzaldehyde (2.51 mmol, 1.0 equiv). A 40 wt% solution of benzyltrimethylammonium hydroxide in methanol was next added by syringe (2.1 ml, 4.99 mmol, 2.0 equiv). The 50 ml one-neck round bottomed flask equipped with a magnetic stir bar was fitted with a condenser and allowed to warm to reflux. After a period of 18 h, the solution was cooled to 60 °C and 15 ml of deionized water was added and allowed to stir at this temperature for a period of 1 h. The resulting mixture was allowed to cool to room temperature at which time the mixture was washed with approximately 20 ml of ethyl acetate. After partitioning the organic from the aqueous phase, the organic fraction was washed with brine, dried over anhydrous magnesium sulfate, and concentrated in vacuo. Purification by column chromatography over silica gel (eluting with 9:1 hexanes/ethyl acetate) Hydrogen atoms were placed in calculated positions and allowed to ride during subsequent refinement, with U iso (H) = 1.2U eq (C) and C-H distances of 0.93 Å. Fig. 1 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 > 2σ(F 2 ) is used only for calculating Rfactors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.09983 (