STEREOCONTROLLED SYNTHESIS OF E-HOMOALLYLIC SULFIDES WITH 1,4,5 RELATED CHIRAL CENTERS USING THE [2,3] SIGMATROPIC REARRANGEMENT OF SULFONIUM YLIDES

E-Homoallylic sulfides with 1,4,5 related chiral centres have been syn thesised in a stereocontrolled way. An aldol condensation sets up the stereochemistry, Lactonisation with 1,2 arylsulfanyl migration followe d by reduction and sulfur-assisted dehydration converts the aldols ste reospecifically into allylic sulfides with 1,2 related chiral centres. Sulfonium salts are generated from the allylic sulfides at low temper ature, and are deprotonated to give sulfonium ylides which undergo [2, 3] sigmatropic rearrangement in good yield to give E-homoallylic sulfi des with 1,4,5 related chiral centres. The 1,4 relative stereochemistr y results from stereospecific chiral transfer and is directly related to the allylic sulfide 1,2 relative stereochemistry. High 4,5 diastere oselectivity is also observed. An explanation for the observed stereos electivity is provided.