Boron-Enolate Enabled Chemoselective Twofold Allylation of Alkenyl-Keto-Imines Using Allylboronic Acids: Asymmetric Construction of Nonadjacent Stereocenters.

A twofold allylation strategy is developed for the efficient synthesis of chiral α-amino-ketones bearing both adjacent and nonadjacent stereocenters including quaternary ones. Both linear and branched-allyl moieties were incorporated using either same or different nucleophiles through successive chemoselective allylations on alkenyl-keto-imines in a single operation. Notably, in the whole reaction sequence, while the first allyl nucleophile reacts selectively on ketone, the second one reacts on imine. Control experiments and DFT calculations supported the proposed reaction mechanism.