Synthèse stéréosélective des sulfones vinyliques Z et E.

The condensation of α-sulphonyl carbanions with esters or with aldehydes (followed in this case by oxidation) gives β-ketosulphones. These were reduced stereoselectively into threo β-hydroxysulphones.Basic conditions have been found where the corresponding tosylates are converted into Z vinylic sulphones whereas the erythro tosylates lead to the E isomer. The corresponding acetoxy-sulphones erythro or threo, under different alkaline conditions are converted into the same E vinylic sulphone in a “convergent” manner.