Acyclic Stereocontrol through the Thio-Claisen Rearrangement of Precursors bearing a Chiral Centre adjacent to Carbon 1

Article abstract of DOI:10.1016/S0040-4020(01)88336-8

The Claisen rearrangement of precursors bearing a stereogenic centre adjacent to carbon 1 of the pericyclic nucleus has been investigated in the sulfur series.Dithioesters having a methyl and various alkyl or alkenyls groups on the β-carbon were deprotonated by LDA.The resulting enethiolates were allylated on sulfur to give S-allyl ketenedithioacetals.The thio-Claisen transposition of the latter compounds was achieved either at room temperature or at 101 deg C to afford good yield of allylated dithioesters.Diastereomeric selectivities up to 95:5 have been observed.These results have been explained by a steric effect and correlated to allylic strain values.