Waveform-Enhanced Alternating Current Electrocatalysis Enables Cu-Catalyzed Carbon–Oxygenation of <i>β</i> -Keto Carbonyls with Alkenes and Alkynes

Alternating current (AC) electrolysis furnishes a dynamic electric field with tunable frequency, duty ratio, and waveform, features that have recently conferred distinct advantages in organic electrosynthesis. In this work, we introduce an unsymmetrical AC waveform-driven Cu-catalyzed oxidative strategy that employs available <i>β</i>-keto carbonyls, alkenes or alkynes to access valuable 5,5-spirocyclic and <i>E</i>-type alkene scaffolds via intra- and intermolecular carbon-oxygenation. Under two distinct waveforms, the reactions proceed smoothly via a Cu-bound radical and nucleophilic addition pathway, respectively. Electron paramagnetic resonance (EPR) studies demonstrate that unsymmetrical AC waveforms maintain a high-concentration dynamic equilibrium of copper intermediates within their respective reaction environments. These findings broaden the scope of AC electrosynthesis and illustrate how waveform design can be leveraged to direct reactivity in challenging bond-forming cascades.