Enantioselective Synthesis of (E)-δ-Stannyl Homoallylic Alcohols via Aldehyde Allylboration Using α-Stannylallylboranes Generated by Allene Hydroboration Followed by a Highly Diastereoselective 1,3-Boratropic Shift

A highly enantioselective synthesis of (E)-delta-stannyl homoallylic alcohols 4 via aldehyde allylboration reactions of the double-chiral allylborane reagent 2a is reported. Allylborane 2a was generated from the hydroboration of commercially available allenylstannane 1 with ((d)Ipc)(2)BH at -40 to -20 degrees C followed by a kinetically controlled and highly diastereoselective 1,3-boratropic shift in intermediate 3a.