Chiral synthesis via organoboranes. 24. B-allylbis(2-isocaranyl)borane as a superior reagent for the asymmetric allylboration of aldehydes

Article abstract of DOI:10.1021/ja00162a047

Hydroboration of (+)-2-carene, readily available via the base-induced isomerization of (+)-3-carene, provides bis(2-isocaranyl)borane, which can be readily transformed into B-allylbis(2-isocaranyl)borane (2-^dICr₂BAll). This new reagent undergoes asymmetric allylboration with a variety of aldehydes and affords the corresponding homoallylic alcohols in 94-99% ee. The enantioselectivities realized with this reagent are significantly higher than those realized with the previously explored reagents, B-allyldiisopinocampheylborane (^dIpc₂Ball) and B-allylbis(4-isocaranyl)borane (4-^dIcr₂BAll).