Media-programmed electrochemical divergence: Switching propargyl alcohols into Z-allylic alcohols or allenes via engineered micellar nanoreactors and surface-confined acidic microenvironments

Abstract: Electrochemistry is rapidly transforming the logic of synthetic design, yet the ability to precisely and sustainably programreaction pathways from a single substrate remains unprecedented. Herein, we disclose a fundamentally new strategy in which engineered reaction media dictate electrochemical fate, enabling propargyl alcohols to be selectively converted into either stereodefined Z -allylic alcohols or synthetically versatile allenes under mild, transition metal-free conditions. In aqueous micellar media derived from our designer surfactant PS-750-M, propargyl alcohols undergo a precious-metal-free electrosemihydrogenation, delivering water-sensitive allylic alcohols with perfect 100% Z -selectivity, and in water! The micelle functions simultaneously as a nanoscopic reaction compartment and a dynamic extraction shuttle, rapidly removing the product from the electrode interface to prevent over-reduction. This environmentally preferred platform eliminates the need for hydrogen gas, organic solvents, and stoichiometric reductants, establishing micellar electroreduction as a powerful tool for sustainable synthesis. In striking contrast, switching to a preferred organic solvent containing a catalytic proton source triggers a mechanistically distinct pathway leading to allenes. Under anodic polarization, the acid reorganizes at the electrode to form a surface-immobilized, glassy phosphate film acting as a strong, non-nucleophilic, confined Brønsted acid catalyst. This microenvironment weakens the C–O bond, stabilizes propargylic cationic character, and promotes a rapid dehydration–rearrangement sequence via a fleeting electrochemically generated enyne intermediate, directly observed in the control NMR study. The result is a clean, selective route to allenes while suppressing conventional side reactions. Together, these studies introduce media-programmed electrochemical reactivity as a generalizable design principle—one in which nanostructured environments and electrode surface catalysis serve as tunable levers to access divergent molecular architectures from a single starting material. This platform opens new retrosynthetic logic for sustainable organic synthesis, demonstrating how precision-engineered microenvironments can unlock reactivity inaccessible by traditional chemical means.