Ligand-Enabled
γ‑C(sp<sup>3</sup>)–H
Olefination of Amines: En Route to Pyrrolidines
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Abstract
Pd(II)-catalyzed
olefination of γ-C(sp<sup>3</sup>)–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 C(sp<sup>3</sup>)–H olefination
reactions. The use of Ns protecting group to direct C(sp<sup>3</sup>)–H activation of alkyl amines is also a significant step
toward practical C–H functionalizations of alkyl amines