Lewis acid promoted Mannich type reactions of α,α-dichloro aldimines with potassium organotrifluoroborates

Potassium phenylethynyltrifluoroborate and potassium styryltrifluoroborates react with α,α-dichlorinated aldimines in the presence of BF₃·OEt₂ as a Lewis acid to give a new stable class of functionalized propargylamines and allylamines. The use of hexafluoroisopropanol as a co-solvent in this modified Petasis reaction allows high yield isolation of the target compounds.