SYN-EFFECT IN THE DESULFONYLATION REACTION OF ALPHA,ALPHA-DIALKYLATED(E)-ALLYLIC SULFONES

It was found that the desulfonylation reaction of alpha,alpha-dialkyla ted (E)-allylic sulfones with a base preferentially affords the steric ally unfavorable (Z)-alkadienes. The relative degree of the ''syn-effe ct'', which is herein defined as an effect which stabilizes the syn-co nformation, leading to (Z)-products, in the transition state against t he steric hindrance, was revealed fbr various substituents at the delt a-position of the (E)-allylic sulfones to be as follows: RO- >> CH3- > RS- > -CH2- > (CH3)(2)CH- >> (CH3)(3)C- > C6H5-. This finding is in a ccord with a previously found tendency in the conversion of (E)-vinyli c sulfones to the corresponding allylic sulfones under basic condition s.