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 PdII‐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. Three more: The 3C homologation of chiral pinacol boronic esters gives di‐ or trisubstituted allylic boronic esters with high yield and E selectivities. The combination of this method with lithiation–borylation enables the synthesis of alkyl chains that bear 1,5‐stereogenic centers. The utility of the process was demonstrated in a formal synthesis of (+)‐jasplakinolide.