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

Lithiation–borylation of propargylic carbamates leads to tertiary propargylic boronic esters in very high e.r., provided that ethylene glycol boronic esters are used. These versatile intermediates undergo a range of highly stereoselective transformations, including protodeboronation to give tertiary allenes and Suzuki–Miyaura cross-couplings of tertiary boron species leading to tetrasubstituted allenes with high enantiospecificity.