Copper-Catalyzed Hydrodifluoroalkylation of N-benzylacrylamides via Intramolecular 1,4-Hydrogen Atom Transfer: Reaction Development and Mechanistic Insights.

A one-pot protocol for Cu(I)-catalyzed hydrodifluoroalkylation of benzyl-protected acrylamides to construct difluoropentanedioate compounds in moderate to excellent yields has been achieved by using the benzyl group as a traceless redox-active hydrogen donor. The mechanistic studies confirmed that the reaction proceeds by adding a difluoroalkyl radical to acrylamide, followed by unexpected intramolecular 1,4-hydrogen atom transfer (HAT) and SET oxidation reaction. DFT calculations demonstrate that the destabilizing steric repulsion is the key factor controlling the chemoselectivity, which switches from 1,4-HAT to 5-exo spirocyclization. This work provides an important basis for the 1,4-HAT reaction in theoretical and practical synthesis applications.