Potassium allyl- and crotyltrifluoroborates: Stable and efficient agents for allylation and crotylation

Article abstract of DOI:10.1016/S0040-4039(99)00774-1

Potassium allyl- and crotyltrifluoroborates react rapidly with aldehydes in the presence of BF₃ · Et₂O. These salts are stable to air and moisture, and lead to adducts in high yield and with high diastereoselectivity. The stereochemistry of the crotylated products is consistent with the reaction via allylboron difluoride and a Zimmerman-Traxler like transition state.