Iron-catalyzed [4 + 2] annulation of α,β-unsaturated ketoxime acetates with enaminones toward functionalized pyridines

The iron-catalyzed [4 ​+ ​2] annulation of α,β-unsaturated ketoxime acetates with enaminones has been developed, providing efficient access to highly substituted pyridines in moderate to good yields. Notable features of the present strategy include low-cost catalytic system, simple and mild reaction condition and wide substrate scope. Mechanistic studies reveal that FeCl2 may directly serve as a Lewis acid to activate the α,β-unsaturated ketoxime acetates for the nucleophilic addition.