Lithium-Boron Chemistry: A Synergistic Strategy in Modern Synthesis

Organoboranes and boronic esters react with nucleophiles to give an intermediate boronate complex. If the nucleophile contains a good enough leaving group, a 1,2-metallate rearrangement takes places resulting in the homologation of the starting boron species. A broad range of achiral and chiral organoborons can be homologated using enantioenriched lithiated carbamates with excellent stereospecificity. The homologated chiral boron species can then undergo further homologations, often in a one-pot process, or be converted into alternative functional groups. The factors responsible for stereocontrol are described and applications of the methodology in total synthesis are illustrated.