Umpolung-like Cross-coupling of Tosylhydrazones with 4-Hydroxy-2-pyridones under Palladium Catalysis.

Tosylhydrazones under palladium catalysis were found to perform cross-coupling reactions with 4-hydroxy-2-pyridones. The umpolung-like reactivity, between the α-carbon of tosylhydrazone and the 3-position of the heterocycle, which is observed in the obtained products, indicates the directed sp3-CH-activation of an alkylated phenol intermediate by the pendant 3-palladated heterocycle. The reaction and its intercepted variants are surveyed in their scope, allowing the synthesis of inaccessible 3-carbocyclic pyridones in moderate to excellent yields.