Stereocontrolled Synthesis of 1,5‐Stereogenic Centers through Three‐Carbon Homologation of Boronic Esters

Allylic pinacol boronic esters are stable toward 1,3‐borotropic rearrangement. We developed a Pd^II‐mediated isomerization process that gives di‐ or trisubstituted allylic boronic esters with high E selectivity. The combination of this method with lithiation–borylation enables the synthesis of carbon chains that bear 1,5‐stereogenic centers. The utility of this method has been demonstrated in a formal synthesis of (+)‐jasplakinolide.