Enamines as Surrogates of Alkene Carbanions for the Reductive Alkenylation of Secondary Amides: An Approach to Allylamines.

A new strategy to construct allylamines through reductive alkenylation of secondary amides with enamines is reported. The method features the use of trifluoromethanesulfonic anhydride as an activation reagent of amides, and enamines as unconventional alkenylation reagents. In this manner, enamines serve as surrogates of alkene carbanions instead of the classical enolates equivalents. A possible mechanism involving a Hoffmann-like elimination of the amine-borane complex intermediate is proposed.