Diastereo- and Enantioselective Synthesis of Homoallylic Amines Bearing Quaternary Carbon Centers

A Cu-catalyzed method for the efficient
enantio- and diastereoselective
synthesis of chiral homoallylic amines bearing a quaternary carbon
and an alkenylboron is disclosed. Transformations are promoted by
a readily prepared (phosphoramidite)–Cu complex and involve
bench-stable γ,γ-disubstituted allyldiborons and benzyl
imines; products are obtained in up to 82% yield, >20:1 dr, and
>99:1
er. Reactions proceed via stereodefined boron-stabilized allylic Cu
species formed by an enantioselective transmetalation. Utility of
the 1-amino-3-alkenylboronate products is highlighted by a variety
of synthetic transformations.