Access to Enoylhydrazones: Pd-Catalyzed Carbonylative Coupling of Alkynes and Hydrazones

Abstract Conventional routes to enoylhydrazones frequently suffer from restricted substrate compatibility and inadequate regiocontrol. To tackle this persistent limitation, we present a robust palladium-mediated carbonylative coupling between alkynes and hydrazones, delivering unsaturated enoylhydrazones with exceptional regiochemical fidelity. This protocol exhibits broad functional-group compatibility and is amenable to gram-scale synthesis, thus resolving the sluggish reactivity typically associated with less nucleophilic hydrazone derivatives. Mechanistic investigations reveal that the transformation proceeds via a Pd(0)/Pd(II) cycle, incorporating CO with near-quantitative atom efficiency, underscoring its alignment with sustainable synthesis goals.