Ligand-Enabled γ-C(sp3)-H Olefination of Amines: En Route to Pyrrolidines

Pd(II)-catalyzed olefination of gamma-C(sp(3))-H bonds of triflyl (Tf) and 4-nitrobenzenesulfonyl (Ns) protected amines is achieved. Subsequent aza-Wacker oxidative cyclization or conjugate addition of the olefinated intermediates provides a variety of C-2 alkylated pyrrolidines. Three pyridine- and quinoline-based ligands are developed to match different classes of amine substrates, demonstrating a rare example of ligand-enabled gamma-C(sp(3))-H olefination reactions. The use of Ns protecting group to direct gamma-C(sp(3))-H activation of alkyl amines is also a significant step toward practical C-H functionalizations of alkyl amines.