Cobalt-Catalyzed Cyclization of Aliphatic Amides and Terminal Alkynes with Silver-Cocatalyst

A new
method of cobalt-catalyzed synthesis of pyrrolidinones from
aliphatic amides and terminal alkynes was discovered through a C–H
bond functionalization process on unactivated sp3 carbons
with the silver cocatalyst using a bidentate auxiliary. For the first
time, a broad range of easily accessible alkynes are exploited as
the reaction partner in C­(sp3)–H bond activation
to give the important 5-ethylidene-pyrrolidin-2-ones in a site-selective
fashion. The reaction tolerates a wide variety of functional groups
including −F, −Cl, −Br, −CF3, ether, cyclopropane, and thiophene. Both pyridine ligand and aromatic
solvent play the important role for the promotion of reactivity. This
cobalt-catalyzed cyclization reaction can be successfully extended
to a variety of aromatic amides to afford a variety of isoindolinones.
Attractive features of this catalytic system include its low cost,
easy operation, and convenient access to a wide range of pyrrolidinones
and isoindolinones.