Pseudohalide-Guided Redox Control Enables Electrochemical Auto-Tandem Nickel Catalysis for Butafulvene Synthesis

Electrochemical nickel catalysis offers a unique platform for redox-controlled reactivity, yet its application to tandem catalysis remains underexplored. We report the development, mechanistic elucidation, and synthetic application of a conceptually novel electrochemical strategy that enables auto-tandem nickel-catalyzed (e-ATC) conversion of propargyl carbonates into butafulvenes, highly strained, antiaromatic scaffolds with limited synthetic accessibility. Comprehensive mechanistic investigations reveal that this transformation merges a reductive coupling with a mechanistically distinct cycloisomerization, both mediated by a single nickel catalyst under electroreductive conditions. Crucially, pseudohalide ligands play a central role in steering a controlled Ni(0)/Ni(II) redox manifold by suppressing one-electron Ni(I) pathways, thereby favoring a polar two-electron mechanism. The method enables broad access to butafulvenes, including fused-ring variants that are inaccessible by previous catalytic routes. Further derivatizations demonstrate the synthetic utility of these butafulvenes as precursors to strained dendralenes and complex polycyclic frameworks.