Lewis Acid Catalyzed Borotropic Shifts in the Design of Diastereo- and Enantioselective γ-Additions of Allylboron Moieties to Aldimines

Catalytic allylboron additions to aldimines are presented for which small amounts of Zn(OMe)2 serve as the co-catalyst to accelerate allyl exchange and 1,3-borotropic shift processes. Low-yielding and moderately α- and diastereoselective reactions are thus turned into highly efficient γ-, diastereo-, and enantioselective transformations that exhibit considerable scope.