Tandem Wittig Rearrangement/Aldol Reactions for the Synthesis of Glycolate Aldols

A new tandem Wittig Rearrangement/aldol reaction of O-benzyl or O-allyl glycolate esters is described. This reaction generates two carbon carbon bonds and two contiguous stereocenters in a single step from simple starting materials. The [1,2]-Wittig rearrangement proceeds under very mild reaction conditions that do not require the use of a strong base, and the 1,2-diol products are obtained in good yield with excellent diastereoselectivity (> 20:1).