The syn–anti dual pattern in elimination from fluorosulphonylethanes promoted by phenoxide and t-butoxide ions

Abstract

The stereochemical course of elimination, promoted by phenoxide and t-butoxide ions, from the diastereoisomeric 1-deuterio-2-fluoro-2-phenylthioethyl phenyl sulphones (I) and (II) has been studied. The reactions with phenoxide ion show an almost completely syn-stereospecific course, but a small contribution from the anti-pathway is present. The importance of the latter process is dramatically increased when a macrocyclic ether is added to the reaction solutions. Using t-butoxide ions in t-butyl alcohol or in benzene-t-butyl alcohol [80 : 20 (v : v)] as solvent the anti-pathway can predominate. The observations are briefly discussed in light of current views concerning elimination reactions.