NH4I-Triggered [4 + 2] Annulation of α,β-Unsaturated Ketoxime Acetates with N-Acetyl Enamides for the Synthesis of Pyridines.

The NH4I-triggered formal [4 + 2] annulation of α,β-unsaturated ketoxime acetates with N-acetyl enamides has been developed. The current protocol employs electron-rich enamides as C2 synthons and enables the efficient and straightforward construction of polysubstituted pyridines in moderate to good yields based on metal-free systems. The reaction tolerates a wide range of functional groups and represents an alternate route toward the synthesis of pyridine derivatives.