Tellurium-catalysed decomposition of a-lithiated benzylic sulphones into 1,2-diarylethylenes

4 Tellurium-catalysed decomposition of a-lithiated benzylic sulphones into 1,2-diarylethylenes 

Since the required starting sulphones are easily prepared by the reaction of sodium benzene sulphinate with benzyl bromides, the described method comprises the formal dimerization of a benzyUc fragment. 

The reaction has been rationalized as involving an attack of lithium teUurolate on a lithi-ated sulphone, promoting the elimination of lithium phenyl sulphinate and the formation of a labile epitelluride that readily collapses into stilbene and elemental tellurium. 

Ar= Ph, o-MeC0H4, p-MeOC0H4, O-CIC0H4, m-CIC0H4, p-BrCel-l4, m,m-MeC0H3, 2-naphthyl, o-biphenylyl 

The product is heated under reflux in CHCI3 (15 mL) containing TeCl4 (0.10 g, 0.37 mmol) for 1 h. The cooled solution is then shaken with 5% aqueous Na2C03 in a separating funnel. The organic layer is dried and evaporated, giving pure franx-stilbene (0.33 g (85%) m.p. 124°C). 

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