Catalytic Asymmetric Allene Diboration/Allylation/Functionalization

Significance

This work represents further developments in the area of the recently discovered asymmetric diboration of allenes. The resulting allyl-alkenyl bis-boranes may react consequently in diastereoselective allylations of carbonyl compounds and then as nucleophiles in a cross-coupling reaction, or can be trapped with other electrophiles. All these reactions are performed in one pot and offer overall a possibility for the introduction of functional groups into the allene precursor. The optimization of the TADDOL-like ligand 1 allowed achieving very good enantioselectivities in most cases. The stereoselectivity of the allylation is controlled by the configuration of the allylboron intermediate and thus can be determined by the choice of the ligand enantiomer.