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.