A Mild and Highly Diastereoselective Preparation of -Alkenyl-2-Pyridones via 2-Halopyridinium Salts and Aldehydes.

An experimentally simple one-pot preparation of -alkenyl-2-pyridones is reported. The reaction features mild conditions using readily available 2-halopyridinium salts and aldehydes. -Alkenyl-2-pyridone formation proceeds with high diastereoselectivity, and a wide range of aldehyde reaction partners is tolerated. Pyridone products are also amenable to further manipulation, including conversion to -alkyl pyridones and polycyclic ring systems.