Enantioconvergent Hydroboration of a Racemic Allene: Enantioselective Synthesis of (<i>E</i>)-δ-Stannyl-<i>anti</i>-homoallylic Alcohols via Aldehyde Crotylboration

Abstract

The enantioconvergent hydroboration of racemic allenylstannane (±)-1 with ((d)Ipc)(2)BH converts both enantiomers of (±)-1 into the enantioenriched crotylborane (S)-E-3. Subsequent crotylboration of aldehydes with (S)-E-3 provides (E)-stannyl-homoallylic alcohols 5 in good yields and with excellent enantioselectivity.