Electrochemistry offers new opportunities for sustainable synthesis,^[1] yet controlling divergent outcomes from a single substrate remains challenging.^[2],[3],[4] Here, we show that programmed reaction media can dictate electrochemical pathways, enabling propargyl alcohols to selectively form either Z-allylic alcohols or allenes under mild, transition-metal-free conditions.

In aqueous PS-750-M micellar media, electrosemihydrogenation delivers Z-allylic alcohols with 100% selectivity. The micellar nanoreactor acts as both a confined reaction environment and an extraction shuttle, suppressing over-reduction and eliminating the need for hydrogen gas, organic solvents, or toxic waste-generating reductants.

In contrast, switching to a non-micellar medium with a catalytic proton source in the bulk medium and proton film at the anode redirects the reaction toward allenes. Under anodic conditions, a surface-confined phosphate film forms to protect the anode from over-reduction, while functioning as a strong Brønsted acid pool that promotes C–O bond activation and selective dehydration–reduction.

These results establish media-programmed electrochemical reactivity as a general design principle, in which engineered microenvironments and electrode interfaces enable divergent synthesis from a common precursor, advancing sustainable and programmable organic synthesis.

[1]   R. Mathison, E. Rani, A. M. Rose, F. Prendi, C. K. Bloomquist, M. A. Modestino, Journal of the American Chemical Society, 2025, 147, 37576–37586.
[2]   H. Wang,   W. Gao,   J. Han,   S. Liu,   A. B. Ibragimov,   S. Murtaza,   L. Ma, J. Chen,  Green Chemistry, 2026, 10.1039.D6GC00942E
[3]   Y. Yuan, A. Lei, Nature Communications, 2020, 11, 802.
[4]   M. Yan, Y. Kawamata, P. S. Baran, Chemical Reviews, 2017, 117, 13230–13319.