Diol desymmetrization as an approach to the synthesis of unsymmetrical dienyl diesters

The tandem oxidation/Wittig olefination of unactivated diols utilizing manganese dioxide produces α,β-unsaturated hydroxy esters in high yields in a highly effective desymmetrization process. The formation of small quantities of the corresponding lactones suggests that the reaction may proceed through a lactol intermediate in some cases. The α,β-unsaturated hydroxy esters are transformed into symmetrical or unsymmetrical dienyl diesters using a second oxidation/Wittig olefination sequence mediated by PCC.