Enantioselective Synthesis and Cross-Coupling of Tertiary Propargylic Boronic Esters Using Lithiation-Borylation of Propargylic Carbamates

摘要

Chiral tertiary boronic esters have been shown to be useful intermediates in organic synthesis, as they can undergo a variety of functional group transformations, for example, conversion to alcohols, amines, quaternary centers, or aryl-dialkylmethmes with high stereospecificity. Recently, such intermediates have become available in high ee through two distinct methods: 1) borylation of Michael acceptors or allylic electrophiles, and 2) lithiation-borylation of secondary benzylic carbamates (Scheme l), which can deliver exceptionally high enantioselectivities over a broad range of substrates (> 99.1 e.r.).